Glioblastoma (GBM) is the most common malignant tumor arising from brain parenchyma. Although many efforts have been made to develop therapies for GBM, the prognosis still remains poor, mainly because of the difficulty in total resection of the tumor mass from brain tissue and the resistance of the residual tumor against standard chemoradiotherapy. Therefore, novel adjuvant therapies are urgently needed. Recent genome-wide analyses of GBM cases have clarified molecular signaling mechanisms underlying GBM biology. However, results of clinical trials targeting phosphorylation-mediated signaling have been unsatisfactory to date. Protein phosphatases are enzymes that antagonize phosphorylation signaling by dephosphorylating phosphorylated signaling molecules. Recently, the critical roles of phosphatases in the regulation of oncogenic signaling in malignant tumor cells have been reported, and tumorigenic roles of deregulated phosphatases have been demonstrated in GBM. However, a detailed mechanism underlying phosphatase-mediated signaling transduction in the regulation of GBM has not been elucidated, and such information is necessary to apply phosphatases as a therapeutic target for GBM. This review highlights and summarizes the phosphatases that have crucial roles in the regulation of oncogenic signaling in GBM cells. Malignant gliomas are the most common primary intracranial malignant neoplasm arising from brain parenchyma. And, Glioblastoma (GBM) is the most malignant and aggressive form of gliomas (WHO grade Ⅳ) with the highly infiltrative phenotype, refractoriness, and genetical complexity ,2. DespiRegulation of molecular signaling, including signaling related to tumor biology, generally involves post-translational modification of the signaling molecules. One of the most common modifications is phosphorylation. As a result of upstream signaling activation, kinases are activated and attach phosphate groups to certain amino-acid residues of their specific substrate molecules, resulting in downstream signaling activation. In GBM, kinases are often hyperactivated as a result of genetic alteration or enhanced upstream signaling activation, and, therefore, kinase hyperactivation has been focused on as a therapeutic target ,18,19,20Protein phosphatases (PPPs), as negative regulators of phosphorylation-dependent signaling, remove phosphate groups of certain phosphorylated amino-acid residues of specific substrate molecules ,26,27,28PPPs are classified as classical or atypical PPPs  21,23,2,223,27. To develop clinical GBM therapies targeting PPPs, it is important to understand the detailed molecular mechanisms underlying both tumor-suppressive and oncogenic PPPs in GBM cells. In what follows, we discuss PPPs that are suggested to have major roles in GBM biology in detail.2+/calmodulin-dependent protein kinase inhibitor (H7), PI3K inhibitor (LY29644), and multi-RTKs inhibitor (sunitinib). These knowledges suggest not only expressional but also enzymatic inhibition of PP2A in GBM cells would be important for the maintenance of GBM malignancy, and the possible role of PP2A reactivation as the therapeutic strategy of GBM would also be considered  is one of the most major PSPs. PP2A is a heterotrimeric protein phosphatase complex which consists of the alpha (PPP2R1A) or beta (PPP2R1B) isoform of the structural A subunit, the alpha (PPP2CA) or beta (PPP2CB) isoform of the catalytic C subunit, and the regulatory B subunit. The A subunit and C subunit forms core heterodimer, and association of one of the multiple B subunits with the core dimer directs various substrate specificity (more than 60 combinations) of PP2A . PP2A reBM cells . TreatmeBM cells . TreatmeBM cells . PharmacBM cells ,59,60. ABM cells ,61,62,63PPP4C gene, which encodes the catalytic subunit of PP4 (PP4C), in the TCGA GBM dataset was not confirmed [Protein phosphatase 4 (PP4) is a member of the type 2A PSP family, which includes PP2A, PP4, and protein phosphatase 6 (PP6) ,65. Thesonfirmed . In addionfirmed . AlthougPPP5C and highly expressed in central nervous system and neurons [Protein phosphatase 5 (PP5) is one of the classical PSPs encoded by  neurons ,72. Phys neurons . On the  neurons ,75. Howe neurons . TherefoLike PP4, Protein phosphatase 6 (PP6) is a member of the type 2A PSP family. It regulates various physiological processes, such as anti-inflammation, cell-cycle regulation, DNA-damage repair, and lymphocyte development. Furthermore, it is reportedly involved in the regulation of tumorigenesis. In melanomas, PP6 has been shown to act as a tumor suppressor . On the Tyrosine-protein phosphatase non-receptor type 6  is a PTP primarily expressed in hematopoietic cells in normal tissue and regulates hematopoietic signaling, such as tyrosine-protein kinase Lyn-mediated pathway. In a series of glioma cases, high expression of SHP1 in glioma tissue was associated with poor prognosis . FurtherTyrosine-protein phosphatase non-receptor type 11  is a PTP activated mainly by RTKs and is one of the representative PTPs that have oncogenic roles in various cancers ,83,84,85Tyrosine-protein phosphatase non-receptor type 13 (PTPN13 or PTPL1) is a PTP that regulates various cellular functions, such as proliferation and differentiation, via the Ras-ERK cascade or the Rho-associated protein kinase (ROCK) pathway ,93,94,95PTPRD gene and is inactivated in about 2 to 3% of GBM cases in the TCGA dataset [PTPRD triggers craniosynostosis, hearing loss, or intellectual disability [PTPRD is frequently observed [Receptor-type tyrosine-protein phosphatase delta (PTPRD) is one of the receptor-type tyrosine kinases (RTPTPs). PTPRD is encoded by the  dataset . Physiol dataset , and mutsability ,104. In observed ,106. Forobserved ,107. TheReceptor-type tyrosine-protein phosphatase mu (PTPRM or RTPTPμ) is RPTPT expressed in endothelial, glial, and neuronal cells. PTPRM regulates various biological process, such as cell growth, differentiation, and mitosis. And importantly, PTPRM positively regulates cell–cell adhesion by association with another PTPRM expressed at adjacent cells via homophilic binding . The rolPTPRZ1 [Receptor-type tyrosine-protein phosphatase zeta (PTPRZ) is an RTPTP encoded by PTPRZ1 ,114. In PTPRZ1 ,116. PhoPTPRZ1 . In GBM PTPRZ1 ,118. ImpPTPRZ1 . In addiPTPRZ1 ,120,121.PTPRZ1 . The bioPTEN promoter methylation-mediated PTEN silencing has also been detected in GBMs [Phosphatase and tensin homolog (PTEN) is one of the best known DUSPs in gliomas, because inactivation of PTEN by deletion or mutation was discovered in 41% of the TCGA GBM dataset . In phys in GBMs . Because in GBMs ,127,128, in GBMs , and exo in GBMs , suggestDUSP1, and DUSP1 expression is transcriptionally regulated by tumor suppressor p53 [Most DUSP family members regulate the phosphorylation (activation) status and subcellular localization of MAPKs ,28,131. ssor p53 , which issor p53 . Thus, sssor p53 . Knockdossor p53 . These fDUSP4 and is widely expressed in the nucleus in various tissues. Like other DUSPs, DUSP4 dephosphorylates MAPKs, such as ERK1, ERK2, and JNK, and regulates proliferation and differentiation [DUSP4 promoter methylation [DUSP4 promoter methylation is reported to be associated with alteration of the IDH1 gene encoding isocitrate dehydrogenase 1 (IDH1) [IDH1 mutation is one of the most important genetic alteration in gliomas, which is not only necessary for molecular diagnosis of glioma cases, but is also essential for understanding glioma biology [IDH1 mutations in gliomas are gain-of-function mutations that lead to the generation of the oncometabolite 2-hydroxyglutarate instead of 2-oxoglutarate from isocitrate, which induces a wide range of epigenetic dysregulation collectively termed “glioma CpG island methylator phenotype” [IDH1 mutation is one of the most important determining factors for molecular diagnosis in the WHO 2016 classification of gliomas [IDH1 mutation and to contribute to glioma tumorigenesis through enhancement of MAPK signaling. Accordingly, the DUSP4 expression level might serve as a predictor of IDH1 mutation, which currently is crucial for the molecular diagnosis of gliomas.Dual-specificity phosphatase 4 (DUSP4)/mitogen-activated protein kinase phosphatase 2 (MKP-2) is encoded by ntiation ,131. In ntiation ,138,139,ntiation . This dohylation ,141. Imp1 (IDH1) , which c1 (IDH1) . IDH1 mu biology . IDH1 muenotype” . The pre gliomas ,146. TheDUSP26 and dephosphorylates MAPKs, including ERK, JNK, and p38; however, its physiological function remains unclear. In tumor cells, DUSP26 is known to act as both oncogene and tumor suppressor. A recent study revealed that the oncogenic activity of DUSP26 depends on dephosphorylation and inactivation of tumor suppressor p53 [Dual-specificity phosphatase 26 (DUSP26) is encoded by ssor p53 . In GBMsssor p53 . Anotherssor p53 . CollectPhosphatase of regenerating liver 3 (PRL-3) is a DUSP that positively regulates various cellular signaling factors, such as PI3K, Src, and Rho ,151,152.CDKN3 gene, which encodes KAP, in the TCGA GBM dataset was not confirmed [Cyclin-dependent kinase inhibitor 3  is a DUSP that physiologically dephosphorylates cyclin-dependent kinase 2 (CDK2) and induces mitotic G1-S arrest ,160. In onfirmed , KAP exponfirmed ; howeveronfirmed . An in vonfirmed . In addionfirmed . TherefoThe cell division cycle 25 (CDC25) family of DUSPs is commonly involved in mitotic entry in the cell cycle through dephosphorylation and activation of cyclin-dependent kinases (CDKs). In many cancers, the upregulated expression of CDC25s and its role in tumor progression by accelerating proliferation has been confirmed. All three CDC25 variants  are involved in the regulation of GBM biology. Although genetic alterations of the genes encoding CDC25s are not observed in the TCGA GBM dataset, in a certain series of human glioma samples, expression of the cell-cycle marker Ki67 is increased in parallel with increased CDC25A expression, and dephosphorylation of PKM2 by CDC25A induces glycolytic metabolism, resulting in the Warburg effect and tumorigenicity of GBM cells ,164. On EYA2 is observed in around 0.7% of the total cases [The eyes absent (EYA) family (EYA1–4) is a group of atypical PPPs that function as transcriptional cofactors as well as phosphatases. As for the physiological functions of the EYA family, they are known to be involved in organ development by regulating RTK, transforming growth factor (TGF) and Hedgehog-mediated signaling ,175,176.al cases . Thus, aRecently, to establish the therapy targeting phosphatases based on the biological features of each phosphatase upon neoplasms, the small molecule inhibitors and activators against some phosphatases have been developed as the antitumor agents. The summary of these agents is shown in https://clinicaltrials.gov/ct2/show/NCT03027388). However, okadaic acid-induced dormancy of GBM stem-like cells was also reported [As noted above, PP2A works as either oncogenic protein or tumor suppressor which is dependent on the type harboring tumor, and the inhibitor and activator have been the focused as novel anticancer drug against various malignancies previously. LB-100, a water-soluble small molecule inhibitor of PP2A, and its lipid-soluble derivative LB-102 have been shown antitumor effects against various tumors . And impreported . This mereported . OP440, reported . Anticanreported . In GBMsreported . In addireported . Currentreported . Efficacreported ,188; howhttps://clinicaltrials.gov/ct2/show/NCT03114319); however, the efficacy of these allosteric inhibitors of SHP2 in GBM treatment has not yet been well-proven. On the other hand, the activator of SHP2, geranylnaringenin (CG902), is reported to inhibit proliferation of the prostate cell line via SHP2-dependent STAT3 suppression [As mentioned above, not only tumor-suppressive roles but tumorigenic functions of SHP2 have been suggested in various cancer systems. Therefore, SHP2 inhibitors, as well as SHP2 activators, have been developed as the anticancer drugs. The classical SHP2 inhibitors, such as NSC-87877 or PHPS1 which targets the catalytic domain of SHP2 ,212, dempression . Althougpression .As mentioned above, suppression of PTPRZ expression resulted in inhibition of GBM cell oncogenicity. SCB4380, a cell-impermeable small molecule PTPRZ inhibitor which also potentially blocks PTPRG activity, suppressed migration, proliferation, and tumorigenicity of the Rat GBM cell line by liposome-mediated intracellular loading . NAZ2329The various inhibitors targeting certain DUSPs  have been developed for cancer therapy . Among tInhibitors targeting PRL-3 have been developed as anti-cancer agents for years. Thienopyridone, a classical PRL-3 inhibitor targeting active site of PRL-3, blocks PRLs activity and has demonstrated anticancer effects . In addiCDC25s play fundamental roles in regulation of GBM biology, and pharmacological inhibition of CDC25B or CDC25C expression resulted in growth arrest of GBM cells ,172,173.As noted above, EYA2 is overexpressed and regulates growth and invasion of high-grade gliomas including GBMs . MLS0005https://clinicaltrials.gov/ct2/show/NCT03027388), and the drugs targeting PPPs with greater permeability of the BBB, such as SMAPs, have been developed recently [Given current knowledge, it still remains difficult to determine which PPPs might be appropriate as a therapeutic target for GBM. Therefore, it is necessary to verify the effect and usefulness of PPP inactivation or activation in vitro before the efficacy of targeting PPPs which can be studies in in vivo models or clinical studies. As for inhibitors or activator of PPPs, substrate specificity and blood–brain barrier (BBB) permeability might pose issues, especially in the case of GBMs . Now, asrecently ,187,188;Recent studies on glioma biology have indicated the roles of PPPs in the regulation of GBM oncogenicity, and the modulation of PPP expression or activity for clinical GBM treatment is gradually getting closer. However, further in-depth studies are needed before the application of PPP modulation in clinical GBM treatment can be contemplated, as PPPs are more difficult as therapeutic targets than certain other molecules because a single PPP regulates multiple and complex signaling pathways. However, from another angle, PPP modulation might avoid relapse and the development of therapeutic insensitivity in GBM exactly because PPPs modulate diverse intracellular signaling pathways. In any case, targeting of PPPs in GBM therapy would be challenging but is worth further development. In future, highly specific and blood–brain barrier-permeable PPP inhibitors might have potential as novel therapeutic agents against refractory GBMs.


We reconcile this liquid-like model incorporating thermally-activated dielectric solvation with more standard solid-state theories of the emission Stokes shift in crystalline semiconductors.Lead-halide perovskites have emerged as promising materials for photovoltaic and optoelectronic applications. Their significantly anharmonic lattice motion, in contrast to conventional harmonic semiconductors, presents a conceptual challenge in understanding the genesis of their exceptional optoelectronic properties. Here we report a strongly temperature dependent luminescence Stokes shift in the electronic spectra of both hybrid and inorganic lead-bromide perovskite single crystals. This behavior stands in stark contrast to that exhibited by more conventional crystalline semiconductors. We correlate the electronic spectra with the anti-Stokes and Stokes Raman vibrational spectra. Dielectric solvation theories, originally developed for excited molecules dissolved in polar liquids, reproduce our experimental observations. Our approach, which invokes a classical Debye-like relaxation process, captures the dielectric response originating from the incipient anharmonicity of the LO phonon at about 20 meV (160 cm Lead halide perovskites have unique electronic properties that depend on the crystal’s anharmonicity. Dielectric solvation theories, developed for molecules dissolved in polar liquids, are shown here to reproduce the temperature behavior of carrier solvation in the electronic spectra, implying strongly anharmonic lattice dynamics. Despite their inexpensive and facile synthesis, the lead-halide perovskites exhibit long carrier lifetimes and diffusion lengths, as well as low electron-hole recombination rates2. In search of the basic cause of these remarkable properties, several models and perspectives have been discussed, including Rashba splitting4, ferroelectricity7, and polaron formation10. The large polaron model provides a conceptual starting point in understanding the electron-phonon interaction in polar solids8. In LHPs, a polaron theory must take into account the strongly anharmonic atomic displacements that are observed at room temperature14. While marked anharmonicity occurs in some oxide perovskites and other dielectrics15, it is unusual in the crystalline semiconductors that are typically employed in optoelectronic device applications. Indeed, semiconductor lattice dynamics and polarons are typically modeled as harmonic with small perturbative anharmonic corrections17. Recently the significance of the strongly anharmonic lattice dynamics has begun to be recognized and considered in LHPs19.Solution processed lead-halide perovskites (LHPs) are highly promising materials for photovoltaic and optoelectronic applications3NH3PbBr3 (MAPbBr3) and all-inorganic CsPbBr3. The emission Stokes shift stems from the fact that, to a good approximation, absorption instantaneously excites an exciton resonance before any possible excited state lattice relaxation can occur, while emission probes the inter-band electronic transition after lattice relaxation. We observe that in contrast to conventional IV, III-V, and II-VI semiconductors, the emission Stokes shift in lead-halide perovskites significantly increases with T. Using classical dielectric solvation theories, originally developed for describing the Stokes shift of molecules in polar liquids, we reproduce the experimental observation. The efficacy of dielectric solvation theory highlights the role of lattice anharmonicity in carrier-lattice interactions in lead-halide perovskites. Yet we nevertheless show that this result is consistent with the ability of an effective harmonic model to describe the emission Stokes shift.In this work we explore the consequence of strong lattice anharmonicity on carrier recombination luminescence. We examine the difference between the absorption and luminescence resonance energies  as a function of temperature (T). We do so for two typical halide perovskites single crystals: hybrid CHα is calculated from the observed reflectance spectra using a Kramers–Kronig constrained variational analysis. . We assign this energy scale to framework LO phonons as did Wright et al.Figure t by Eq.  at highet by Eq. , γ0, cap27. The highest energy optical phonon branch of the lead-bromide lattice occurs at about 20 meV (160 cm−1)29. These modes involve predominantly halide octahedral motion27. Thus we observe the somewhat expected fact that linewidth broadening shows activated behavior due to carrier coupling to LO phonons.Both perovskite compounds exhibit similar distributions of framework vibrational modes3 (green dots) and MAPbBr3 (blue dots). Below about 50 K the emission Stokes shift is weakly dependent on temperature, and decreases as T increases. This type of Stokes-shifted luminescence is typically produced by potential fluctuations, such as compositional disorder, defect sites, and surface states, which allow relaxation and localization into trap sites before radiative recombination30. The influence of such extrinsic fluctuations in the emission Stokes shift decreases at higher temperature as detrapping occurs.Figure FC) into phonons. For the simplest model of ground and excited state potential energy curves of displaced harmonic oscillators, the Frank–Condon energy is EFC = Sħω, where S is the Huang-Rhys factor and ħω is the phonon energy31. S itself is a geometrical factor with no temperature dependence. In this simple harmonic model the excitonic absorption and emission linewidths will broaden as T increases, but the emission Stokes shift is independent of T. This model, often applied to localized states, clearly does not describe our data.From 60 K to 300 K, the emission Stokes shift strongly increases with T. This finding is both surprising and significant. Generally speaking, an intrinsic emission Stokes shift results from lattice relaxation around an optically excited state. For example, in a Frank–Condon picture, the optically excited state prepared by vertical electronic transition subsequently relaxes to lower vibrational states of the excited potential curve, dissipating the excess energy  dielectric constant of a polar liquid thus shows a large increase from low to high temperature. In typical organic dipolar solvents, a dielectric continuum model captures the non-equilibrium solvation around the excited molecule, as described in the Ooshika-Lippert-Mataga (OLM) relation35. More general descriptions of this dielectric solvation process exist36, which provide closed-form analytical expressions for the emission Stokes shift We now seek to understand the anomalous temperature dependence of the emission Stokes shift. Some temperature dependence should come from the T dependence of the static dielectric constant s = iω, a is the radius of a bounding cavity around the solute molecule, and ε(s) is the dielectric response of the solvent. In this context, the constant a should be no smaller than the excitonic radius. The nature of the luminescing band edge species has been a topic of ongoing discussion37. We apply this dielectric solvation framework also to dipolar excitonic species. The dielectric solvation of a single point dipole is expressed in Eq.  are the same as in Eq.   0 obtain40. A classical exemplar of this fact is the success of the Marcus theory of electron transfer in polar solvents such as water42. Indeed, recent simulations demonstrate that even though the perovskite lattice is highly anharmonic, the relevant nuclear fluctuations are statistically nearly Gaussian. Given these facts, we postulate that an effective harmonic phononic model of the Stokes shift may be constructed, using the strongly temperature-dependent dielectric function as input43.In the dynamics of liquid state processes, it is well-known that the non-equilibrium response of even highly anharmonic systems may be modeled by an effective harmonic model as long as the pertinent fluctuations are Gaussian or if the environment responds in a linear fashion45. Here ELO is the LO phonon energy, and the other symbols have their usual meaning. This model does not consider excitons. This framework works well for GaAs46, CdSe47, CdTe49, and other semiconductors at room temperature. In these compounds the emission Stokes shift is just a few meV. Furthermore in such standard cases the static dielectric constant is typically only about 10% larger than the optical dielectric constant50. In contrast, the predicted emission Stokes shift  ~ A × n(T) where A ~ 6 and n is the Bose–Einstein population. In conventional semiconductors the dielectric response is ε0(T) ~ A × T where A ~ 10−450. This difference is not due to different LO phonon frequencies or populations. For example the ELO of CdTe (21 meV) is very similar to that of CsPbBr3 and MAPbBr3 (~20 meV). A low ELO and the resulting larger phonon population at higher T does not explain the stronger coupling in lead-halide perovskites.This dielectric response is far stronger than in the more conventional semiconductors. Thus the coupling between the moving carrier and lattice is large in these lead-halide perovskites. These perovskites show a T dependent dielectric response that behaves roughly as 52. Large polarons help to explain the stabilization and protection of carriers in lead halide perovskites10. Scattering by LO phonons is thought to limit the mobility of polarons54. The dielectric response factor (1/ε∞ − 1/ε0) in Eq. . Figure 3 and MAPbBr3, respectively. Previously we reported their Raman spectra above 80 K27. The new measurements reported here extend the T range down to 5 K, well below all structural phase transitions. We observe that the Raman modes broaden and shift as they are thermally populated. This thermal population is directly observed in anti-Stokes Raman scattering in Fig. −1 becomes thermally populated near 50–60 K, matching the onset of luminescence Stokes shift rise and linewidth broadening discussed above. Also as discussed above, theoretically the perovskite framework LO mode energies fall just below 150 cm−1 at the Brillouin zone center Γ point.The analysis of both the electronic spectral width and the emission Stokes shift point to significant coupling with the lead-halide framework modes at the top of the phonon dispersion curves  and HBr (48% Acros) were mixed to prepare CH3NH3Br. PbBr2 (98% Sigma-Aldrich) and CH3NH3Br were then dissolved in N,N-dimethylformamide at 1:1 ratio to form 1 M solution. Single crystals of MA were grown by diffusion of isopropyl alcohol vapor into the solution. Single crystals of Cs were grown by diffusion of n-propyl alcohol vapor into a 30 mM solution of 1:1 lead bromide  and cesium bromide  in N,N- dimethylformamide.High quality, mm-sized single crystals of MAPbBr−5 torr, before cooling down with liquid Helium.Single crystals were mounted onto the cold finger of an optical cryostat. The sample chamber was pumped down to the order of 1060.A quartz-tungsten-halogen lamp was used as the white light source. The white light passed through a 100-micron pinhole and was collimated. The white light beam was then sent into an inverted microscope, and imaged onto the back aperture of a ×40 long working distance objective with NA = 0.6. The objective focused the beam onto samples at normal incidence. The reflected light was collected by the same objective and imaged onto the entrance slit of a spectrograph. A 150 grooves/mm grating dispersed the reflected light on a thermoelectrically cooled CCD detector. For each measurement, reflectance of fused silica was collected under the same conditions, which was used as a reference2 at low temperatures (T < 200 K), and about 1 W/cm2 at higher temperatures (T > 200 K).Photoluminescence was excited with the 458 nm line of an Ar ion laser. The excitation laser was focused on samples using a ×40 objective with NA = 0.6. Photoluminescence was collected by the same objective, imaged onto the spectrograph entrance slit, and dispersed by a 150 grooves/mm grating on the CCD detector. Typical excitation power was about 0.2 W/cm−1 around the 633 nm laser line. After passing through the VHG filters, the Raman signal was spatially filtered, imaged onto the entrance slit of a spectrograph, dispersed by a 1800 grooves/mm grating onto a liquid nitrogen cooled Si CCD detector. Spectral collection covered anti-Stokes and Stokes region from −200 to 200 cm−1. The anti-Stokes to Stokes ratio was used to calculate sample spot temperature as expected from the Bose–Einstein distribution. The cryostat temperature control and readout were found to be accurate within ±1 K. Data analysis was done using the Python programming language. Both reflectance and photoluminescence data was fit with the lmfit package61.The 633 nm line of a Helium-Neon laser was used as the Raman excitation. Spurious light in the laser beam was rejected by a 90/10 volume holographic grating (VHG) beam splitter. The beam was coupled into a home-built inverted microscope, and focused on samples with a ×40 objective with NA = 0.6. The Raman scattered light was collected by the same objective. Rayleigh scattered light was rejected first by the 90/10 VHG beam splitter, and then by two VHG notch filters. Each notch filter has OD > 4 rejection, and a spectral cutoff full width half maximum about 7 cmCustom computer codes used in this work are available from the corresponding author upon request.Supplementary Information


It has been nearly 40 years since human T-cell leukemia virus-1 (HTLV-1), the first oncogenic retrovirus in humans and the first demonstrable cause of cancer by an infectious agent, was discovered. Studies indicate that HTLV-1 is arguably one of the most carcinogenic agents to humans. In addition, HTLV-1 causes a diverse array of diseases, including myelopathy and immunodeficiency, which cause morbidity and mortality to many people in the world, including the indigenous population in Australia, a fact that was emphasized only recently. HTLV-1 can be transmitted by infected lymphocytes, from mother to child via breast feeding, by sex, by blood transfusion, and by organ transplant. Therefore, the prevention of HTLV-1 infection is possible but such action has been taken in only a limited part of the world. However, until now it has not been listed by the World Health Organization as a sexually transmitted organism nor, oddly, recognized as an oncogenic virus by the recent list of the National Cancer Institute/National Institutes of Health. Such underestimation of HTLV-1 by health agencies has led to a remarkable lack of funding supporting research and development of treatments and vaccines, causing HTLV-1 to remain a global threat. Nonetheless, there are emerging novel therapeutic and prevention strategies which will help people who have diseases caused by HTLV-1. In this review, we present a brief historic overview of the key events in HTLV-1 research, including its pivotal role in generating ideas of a retrovirus cause of AIDS and in several essential technologies applicable to the discovery of HIV and the unraveling of its genes and their function. This is followed by the status of HTLV-1 research and the preventive and therapeutic developments of today. We also discuss pending issues and remaining challenges to enable the eradication of HTLV-1 in the future. Thus, it is fitting to start this review by looking back at the chronology preceding the discovery of HTLV-1. The group, focusing on virology, has been pursuing the biochemical purification and characterization of the reverse transcriptase since the early ’70s. In the mid-’70s, they identified the first T-cell growth-promoting cytokine2, now known as interleukin-2 (IL-2), in their efforts to enable a long-term culture of human T cells so they could study cells isolated from patients with leukemia. All of these efforts paved the way for the group to discover a new retrovirus from human T cells, the HTLV-1; subsequently, the same group discovered the second human retrovirus (HTLV-2)3 and co-discovered the third human retrovirus, now known as HIV-1 as the cause of AIDS4. In 1981, at a conference held in Kyoto (near Lake Biwa), the Gallo group reported that sera from patients with adult T-cell leukemia (ATL), described below, contain antibodies against the purified p24 protein of the HTLV5. Later that year, a Japanese group led by Hinuma isolated a similar type C-retrovirus from an ATL cell line and also showed that sera from patients with ATL contain antibodies reactive with cells infected with the new virus6. This virus was later shown to be identical to HTLV-18.It has been 40 years since human T-cell leukemia virus (HTLV)-19. It shifted the paradigm in the virology world in many ways by demonstrating not only that retroviruses can infect humans but also that retroviruses can be pathogenic in humans. In 1982, the Gallo group reported the second human retrovirus, HTLV-210. Around the same time, reports of a rare form of lung infection,Pneumocystis carinii pneumonia, among homosexual young men started to appear from the west-coast areas of the US and soon from other parts of the world, which the US Centers for Disease Control and Prevention named “acquired immunodeficiency syndrome” (AIDS). It drew the attention of virologists, and in 1982 Max Essex and Gallo postulated that a new type of (retro)virus may be associated with AIDS, although the scientific community remained skeptical. In 1983, the Montagnier group at the Pasteur Institute in Paris reported the discovery of a new retrovirus  from one patient with AIDS11. In 1983 and 1984, the Gallo group reported the isolation of a human retrovirus (HTLV-III) in 48 patients with AIDS and, along with their blood test, linked the virus to AIDS as the cause18. LAV and HTLV-III were shown to be the same virus22, and the name HIV (human immunodeficiency virus) was adopted in 1986. The technological approach was the same as for the HTLVs. Studies on HTLVs also provided both conceptual and scientific methodology critical to the discovery of HIV23; thus, the discovery of HTLV-1 and -2 laid the foundation for the discovery of HIV. Moreover, it provided the framework by creating the “human retrovirology field”. Furthermore, the study on thepX/Tax gene of HTLV-1 accelerated the mechanistic understanding of the action of HIV through the study of regulatory elements of this virus26 , asTax served as the prototypic example of human retroviral regulatory genes. HIV and HTLV can co-inhabit, as the first isolate of HTLV-III from the Gallo group came from a person who was doubly infected by HTLV-1 and HIV, most likely through blood transfusion, and the same T cells from this individual were producing HTLV-1 and HIV, which challenged the strongly held view at that time of “viral interference”, stating that a cell infected by a retrovirus resists superinfection by another retrovirus. This prevented the Gallo group from announcing the discovery of HTLV-III (HIV) for several months because of the confusion it caused to the group before they realized that these cultures contained HTLV-1 plus a new retrovirus (HIV). On the other hand, this established a new methodology of stably maintaining HIV in culture because CD4 T cells doubly infected by HTLV-1 and HIV would remain viable and keep producing HIV whereas an infection by HIV alone would kill the target CD4 T cells. This led to the concept that immortalized (transformed) CD4 T cells could continuously produce HIV. By adopting HIV to mature CD4 T cells already transformed by other causes than HTLV-1, the cells maintain their growth and enabled the mass production of HIV(as early as 1983), which was essential for establishing a global blood test for HIV4 and central for the testing of anti-HIV drugs.HTLV-1 was the first human retrovirus discovered30 and papilloma viruses32. Although the oncogenic capability of papilloma viruses is as solid as that of HTLV-1, the extent to which EBV/HHV-4 directly causes malignancy is still in dispute33. Despite the prolific nature of EBV/HHV-4 reaching 90% prevalence among adult humans, the associated malignancies such as Burkitt’s lymphoma (BL), Hodgkin’s lymphoma and nasopharyngeal carcinoma are yet unconventional. In addition, BL can occur in the absence of EBV/HHV-430. EBV/HHV-4 is the most powerful B-cell transforming factorin vitro30. However, the pattern and regulation of EBV gene expression are strikingly different betweenin vitro transformed cells andin vivo BL cells34. It is unquestionably a triggering factor for human malignancy, but EBV/HHV-4 appears to require co-factors to cause cancers30.HTLV-1 was the first retrovirus identified from humans. Moreover, it is one of the first human viruses which were proven to have oncogenic effects in humans, together with Epstein–Barr virus (EBV) 35. , inflammatory disorders, especially uveitis, arthritis, and dermatitis, and an immune-deficient state, resulting in bronchiectasis that is causing high mortality in Central Northern Australia36 from Taylor’s group suggests an intriguing re-estimation. Most ATL cases develop from those who contracted HTLV-1 at birth, through mother-to-child infection, but ATL is rarely seen in HTLV-1 carriers who have been infected in adulthood. This is an interesting contrast with the myelopathy HAM/TSP, the second major HTLV-1 disease, which is seen with higher prevalence and accelerated disease progression in those who were infected by HTLV-1 in adulthood because of a blood transfusion or organ-transplantation involving infected T-lymphocytes than those who were infected in the perinatal period. It is also known that perinatal infection accounts for about 20 to 25% of all HTLV-1 infections. Thus, the Taylor group estimates that the true risk of ATL among perinatally infected carriers could be as high as 25%36, a striking number outweighing even the risk of lung cancer associated with tobacco smoking (around 16%37). Earlier, we reported that HTLV-1 displays higher carcinogenic potential than that of any known human oncovirus. This new study suggests that HTLV-1 is arguably one of the most carcinogenic agents known to humans (but thankfully it is not easily transmitted from person to person). Another unique oncogenic nature of HTLV-1 is that it is a direct mechanism (see below for details). Because of the outstanding transforming capability of HTLV-1, we recently returned to its original name (human T-cell leukemia virus-1) and away from human T-lymphotropic virus-1. This was supported by a large majority vote at the 2017 HTLV-1 international meeting in Tokyo38. The major manifestation is the T-cell leukemia (ATL), and the lifetime risk of HTLV-1–infected people to develop ATL is estimated to be around 5%. However, a recent publication39 predates that of HTLV-11. The geographical distribution of patients with ATL, in Japan and in other parts of the world , prompted researchers to hypothesize that an infectious microorganism causes the disease. As shown in40 and the publisher for adoption here), HTLV-1 shows a unique endemic distribution on a global scale, involving Japan, the Caribbean islands, South America , West and Central Africa, Romania, parts of the Middle East , and Central Australia. As discussed below, HTLV-1 is unusually inactive in replication as a virus and rather exists as a genetic element in infected cells after integration. This behavior of HTLV-1 has been used for anthropology studies as well41 to track historical migration of humans. For example, the high prevalence of Asian type HTLV-1 in Japan and among the indigenous people of North and South America suggests that the migration of HTLV-1 (subtype B) infected humans from Asia to America when these two parts were connected through land bridge during the last ice age almost 10,000 years ago. The map, however, also suggests that global epidemiology studies are still to be completed. For example, some heavily populated areas such as India, China, much of Russia, and Sub-Saharan Africa do not offer detailed epidemiologic information on HTLV-1 infection. The strange lack of appropriate funding for such studies is a common obstacle on a global scale for HTLV research.The discovery of ATL42 but that cell-free virions generally do not cause infection. Shortly after the discovery of HTLV-1, many countries adopted HTLV-1 screening in donated blood, effectively reducing the risk of HTLV-1 transmission by transfusion. However, such screening is not yet performed all over the world. Moreover, only few countries (the UK and France) perform HTLV-1 screening on individuals who donated organs. The US has dropped similar screening because of the concerns over losing intact organ sources43 and the argument that HTLV-1 infection in adulthood should not be a medical threat because the prevalence of ATL is low and requires a latency period of four to five decades . Recent studies in Japan, however, provide a different view on this. Yamano and co-workers have studied the post-transplantation development of HAM/TSP by infected organs, which suggests that the myelopathy occurs at about 20 times higher risk (nearly 10% of post-transplantation over 0.3% of mother-to-child transmission). Additionally, the disease rapidly progresses to morbidity within 5 years of infection, which is a striking contrast to the two to three decades of delayed onset and additional two decades of disease development for reaching the final stage of HAM after perinatal infection. This new study (https://www.mhlw.go.jp/file/04-Houdouhappyou-10905500-Kenkoukyoku-Zoukiishokushitsu/0000068136.pdf) may be a serious alert to the global medical community to review and revise their policy on HTLV-1’s threat as a blood-borne pathogen.HTLV-1 can be transmitted from carrier mother to the baby mainly through breast feeding. Equally important is the horizontal transmission by sex and transfer of infected lymphocytes, such as blood transfusion and organ transplant. It is important to emphasize that HTLV-1 infection requires absolute cell-to-cell contact44  and hence named subtype C. Like subtype A and B, subtype C appears to have evolved from simian T-cell leukemia viruses (STLVs) , but intriguingly genetic analysis suggests that the evolution of subtype C might have been independent of other subtypes45. Recent studies revealed that the divergence is highest in a part of thepX region near the 3’ end of the virus. This region encodes for small HTLV-1 proteins such as p30, p12, p13, and p8 that have been extensively studied by the Franchini group (NCI), which showed that these proteins expressed from the open reading frame (ORF) I or II display diverse regulatory functions46. How this would affect the pathogenesis of subtype C is still under investigation.One of the most recent additions to the HTLV-1 epidemiology is Central Australia. Early in the ’90s, HTLV-1 infection in Melanesia was observed. Furthermore, Melanesian HTLV-1 is genetically divergent from major subtypes found in other parts of the worldet al. demonstrated that some communities of Aboriginal people showed 45% HTLV-1 sero-positivity47. The Central Australian HTLV-1 infection presents two emerging issues for the HTLV-1 community. One is the opportunity to study differences of new subtype C and other subtypes and connect them to its pathogenicity. As described below, HTLV-1 subtype C may be distinct from major subtypes in terms of the diseases it causes. In addition, as discussed below, it is a challenge because solving this issue requires not just biological research and medical treatment but social support as well. Again, the threat of HTLV-1 to humankind has been severely underestimated. So it is good news that the Australian government has announced new funding to address the issue.The profound impact of HTLV-1 on the indigenous people of Australia was not recognized until recently, which is another testimony that our understanding of global HTLV-1 infection is still incomplete. Einsiedel48 before HTLV-1 was discovered; then another HTLV-1 disease was identified around 1985. A unique myelopathy called TSP was described in the Caribbean area49. Gessain and de Thé demonstrated that HTLV-1 infection is associated with this neuronal disease50. In 1986, Osameet al. showed that HTLV-1–infected individuals develop a unique myelopathy (HAM)51. The two diseases are identical and hence the name HAM/TSP was adopted. Later studies show that HTLV-1 is also associated with inflammatory diseases53 other than the two diseases already mentioned, such as uveitis55, arthropathy, pneumopathy, dermatitis, exocrinopathy, and myositis. Furthermore, HTLV-1 may cause immunodeficiency. Clinicians earlier observed that ATL is often associated with immunodeficiency which may cause opportunistic infections, but even asymptomatic carriers (ASCs) have mild immunodeficiency . This is being revisited from a new perspective in light of the recent finding that infection of HTLV-1 subtype C among Australian indigenous people is causing high morbidity/mortality by triggering chronic lung infections, including bronchitis, bronchiolitis, and bronchiectasis56.The disease concept of ATL was established in the mid-’70s by Takatsuki and co-workers57, smoldering58, acute48, and lymphoma59 (reviewed by Takatsuki60). The direct causative role of HTLV-1 for this leukemia is solid. Shortly after the discovery of the virus, thein vitro transforming ability of this virus was reported61. The transforming ability of HTLV-1 was subsequently mapped to a region between thepol and 3’ long terminal repeat (LTR), named thepX region, and a non-canonical oncogenic component was identified and named Tax-1. Tax-1 does not show sequence homology to any mammalian gene including known oncogenes. Tax-1 strongly activates the transcription of many host genes64 in addition to HTLV-1’s 5’LTR65. Soon, it was shown that the transcriptional activation by Tax-1 is mediated by nuclear factors, including nuclear factor kappa B (NFκB)67. Subsequent studies depicted how Tax-1 activates the NFκB pathway68. Tax binds to IKKγ (inhibitor of NFκB kinase gamma) and activates the IKKα/β/γ complex71, which facilitates the nuclear translocation of p50/p60 of NFκB. Tax also enhances the processing of NFκB p100 into the active p52 form and thereby activates the “non-canonical” NFκB pathway68. Alternatively, TaxBP1, a cellular binding protein to Tax which functions as an autophagy receptor, is known to repress TRAF-6 (TNF receptor-associated factor-6)/NFκB signaling. Tax can restore NFκB signaling by binding to TaxBP1 and modulating its function.Globally, ATL is the major manifestation of HTLV-1. ATL is now categorized into four types: chronicin vivo, Tax transgenic mice were generated. Using the 5’ LTR of HTLV-1 as enhancer/promoter, Tax expression caused mesenchymal tumors in mice72. Another study demonstrated that Tax transformation is mediated by the downstream activation of NFκB73. More recently, Bazarbachi and co-workers showed that Tax transforms Drosophila eye cells74 and Chenget al. showed that Tax immortalizes human dendritic cellsex vivo75. Thus, Tax has broad transforming effects in a variety of cells across species. However, the development of T-cell malignancy by Tax requires the T cell–specific expression of this gene . A small caveat of this study was that the malignant cells do not express CD4 or CD8; thus, they resemble pre–T cell leukemia/lymphoma whereasin vivo ATL cells show a mature regulatory T (Treg)-like phenotype, although expression of CD4 may not be found in all tumor cells of patients with ATL77. These studies show that Tax is oncogenic but does not determine cell specificity of ATL.To validate the transforming role of Taxet al. discovered that HTLV-1’s minus strand contains a reading frame which encodes a potential transcription factor named HBZ (HTLV-1 bZIP factor)78. Subsequent studies by a group led by one of the authors (MM) demonstrated that HBZ is a very complex gene with many intriguing facets83. It appears to function not only as a protein but also as a regulatory RNA which promotes proliferation of host cells84. As a protein, HBZ activates the transforming growth factor beta (TGF-β)/Smad pathway, which leads to transcriptional activation of theFoxp3 gene85. This finding explains whyin vivo ATL leukemic cells are Foxp3-positive and HTLV-1–infected cells in ASCs and patients with HAM/TSP are within the Foxp3+ subpopulation of CD4 T cells 90, by infected CD4 T cells and non-infected blood cells. Additionally, HBZ inhibits canonical NFκB and Wnt pathways91. HBZ also induces expression of CCR4 and TIGIT at the cell surface93. Importantly, CCR4 is implicated not only in migration but also in the proliferation of T cells94. Likewise, the upregulation of TIGIT, a co-inhibitory molecule, may help evade anti-ATL/HTLV-1 immunity and facilitate the propagation of ATL leukemic cells92. Finally, evidence that HBZ can also cause CD4 T-cell malignancy was provided when this gene was expressed as a transgene in mouse T cells87. Curiously, malignant T cells in HBZ transgenic mice express markers  which are commonly seen within vivo ATL cells. So what is the indispensable transforming component of HTLV-1? At the moment, this remains an open question. Earlier studies revealed that HTLV-1 is quite often (>40%) integrated as a defective provirus which still later helps in the development of ATL95. In many cases, the deletion involves the 5’ LTR and cripples the capacity of the virus to express components in the positive strand including Tax. Such defective viruses are much more commonly seen among patients with ATL than in ASCs96. Curiously, no deletion of 3’ LTR was found, suggesting the critical need for HTLV-1 to retain an antisense-encoded gene (or genes). Also, recent analyses using the next-generation sequencing technology demonstrate that the majority of the HTLV-1 transcripts inin vivo leukemic cells are driven by the 3’LTR, but not by the 5’LTR (see below for more). Antisense genes appear to be a common and critical element of retroviridae. Bovine leukemia virus (BLV), HTLV-1’s sibling virus in cows, also expresses antisense transcripts which are expressed in bovine tumors and associated with cellular transformation97. HIV-1 also encodes an antisense gene and uses it to mediate critical functions for the virus98. So we ask the question again, Tax or HBZ? Curiously, HTLV-1’s sister virus HTLV-2 shows no oncogenic capability, although HTLV-2 also encodes aTax gene (Tax-2), which is a potent transforming genein vitro99. WhereasTax-1 and-2 are highly conserved (>89% identity)17, the antisense genes (HBZ and APH-2 of HTLV-2) are very divergent. The Green lab has shown that APH-2 of HTLV-2 functions as a regulatory factor in host cells101 and is functionally very different from HBZ. These results favor HBZ as the dominant factor in the leukemic transformation. However, the activation of NFκB, which has been considered an essential part of HTLV-1-related cellular transformation, is only caused by Tax, but not by HBZ93, which is seen as a caveat of “the HBZ hypothesis”. Two recent studies indicate that Tax expressionin vivo is transient and seen as only a burst during the cell cycle103. The pulsive expression of Tax, however brief, facilitates the survival of HTLV-1–infected cells by minimizing the alert to the host immune surveillance mechanism103 since the Tax proteinper se is strongly immunogenic105. Moreover, host restriction factors play a role in silencing the function of Tax and viral replication108 and conceals the role Tax might have played in the early phase of cellular transformation. Similar to many other cancer cells, HTLV-1–inserted/transformed cells accumulate somatic mutations. The advancement of next-generation sequencing technology has accelerated the research addressing host genomic alterations caused by HTLV-1. An integrated molecular analysis109  highlighted that alterations were frequently found in Tax-interactome and T-cell activation pathways, including NFκB signaling, trafficking, and immunosurveillance pathways. Gain-of-function mutations were also seen in association with various T-cell signaling molecules, observations that are consistent with previous consensus on the importance of the Tax-NFκB axis in the cellular transformation by HTLV-1. Curiously, this study also recapitulated the above-mentioned reports96 that integrated HTLV-1 proviral genome often displays deletions in the 5’ viral segments, resulting in defective viral replication and production. Moreover, viral transcripts are produced predominantly from the antisense strand, consistent with the importance of HBZ in the development and maintenance of established ATL cells. It is also of note that most antisense transcripts extend beyond the 5’ LTR of HTLV-1 and include neighboring host genes juxtaposed to the integration site109, suggesting the novel role for 3′ LTR as the driver of HTLV-1–related transcriptome. It has been held that the integration of HTLV-1 into the host genome is random. However, new studies challenge this paradigm111. Most recently, Rosewick and van den Broekeet al. showed that integration of HTLV-1 and BLV preferentially occurs near cancer drivers and that insertional mutagenesis appears to drive the clonal persistence and expansion of transformed T cells112. All of these findings were supported by another recent publication113. In addition, Satou and Banghamet al.114 demonstrated that HTLV-1 has a binding site for CTCF, a regulator of chromatin structure. They showed evidence that the insertion of HTLV-1 creates a novel loop structure between the provirus and host genome by recruiting CTCF, which naturally alters the expression of proviral and host genes. Collectively, the characterization of HTLV-1 integration and its impact on the host transcriptional and epigenetic regulations constitute an emerging research field, as is the role of Tax and HBZ for cellular transformation. Even the once-accepted paradigm of the necessity of NFκB activation, may need to be further investigated in light of these new findings.However, a completely independent scenario was presented through studies conducted recently. In 2002, Gaudray and MesnardT cells . It is n115. In HAM/TSP, the major symptoms appear to be caused by the damages to spinal neuronal cells by inflammatory T cells. The suggested mechanism includes the acquisition of an inflammatory nature by HTLV-1–infected CD4 T cells and non-leukemic CD8 T cells. As discussed earlier, HBZ of HTLV-1 facilitates the generation of inflammatory CD4 T cells91. Possibly relevant to the pathogenesis of HAM/TSP is the recent observation that the HBZ protein localizes exclusively in the cytoplasm of lymphocytes in patients with HAM/TSP116, as opposed to the predominant nuclear localization of HBZ in leukemic cells in patients with ATL, suggesting the presence of a HAM/TSP specific use of HBZ in the development of the disease. In addition to cytokines, chemokines CXCL-9 and -10 are produced by HTLV-1–infected CD4 T cells and play important roles in recruiting inflammatory T cells to the site of neuronal destruction117. Furthermore, Azimi, Jacobson, and Waldmann have suggested that γc-cytokines, in particular IL-2 and IL-15, are produced by HTLV-1–infected CD4 T cells via the transcriptional trans-activation by Tax and in turn activate CD8 T cells into inflammatory T cells121 which produce tissue-damaging cytokines such as IFNγ. These molecules are attractive therapeutic targets in treating HAM/TSP, as discussed below.Whereas the oncogenic process of ATL appears mainly molecular and virologic, the pathogenesis of HAM/TSP is more immunologic122 . Anti-IL-2Rα/Tac therapy, including the conjugation of the antibody to toxins or α/β-emitters, has been tried with some success127, but resistant leukemic clones quickly emerged. More recently, CCR4, a chemokine receptor, was identified as an ATL-specific marker132 and anti-CCR4 therapy (using a defucosylated anti-CCR4 antibody) has been clinically tested in Japan with promising results136. The only caveat was that anti-CCR4Ab (mogamulizumab) also depleted natural regulatory T cells (nTregs) and caused hyper-autoimmunity (Stevens–Johnson syndrome) in some cases, which led to one fatal case in the treatment137. Nevertheless, it has been approved as an anti-ATL drug in Japan and clinical trials are being performed in the US as well. Arsenic trioxide, which has been used for AML treatment, was also shown to have anti-ATL effects139 and showed therapeutic effects on chronic ATL cases140, and there is suggestive evidence that this treatment might eradicate “leukemia-initiating cells”141. Also, anti-viral drugs have been tested. Previous findings suggest that HTLV-1 does not actively replicate in CD4 T cells in carriers and patients, prompting the field to consider that anti-viral therapy is not an option in treating HTLV-1 diseases. However, recent research presents more diversified views on this topic146 as anti-viral treatments show some promising results in clinical trials. Collectively, it is fair to say that promising treatments are developing for ATL, but additional strategies should be encouraged as well, including T cell–mediated immunotherapies targeting HTLV-1 components. Historically, it has been repeatedly shown that Tax of HTLV-1 is highly immunogenic and that HTLV-1–infected individuals have anti-Tax Ab and anti-Tax T cells in their circulation, which prompted the field to explore anti-Tax strategies. However, Asquith and Banghamet al.147 investigated which epitope of HTLV-1 would elicit T-cell immunity leading to decreased proviral load of HTLV-1. Surprisingly, it was not anti-Tax or anti-Env but anti-HBZ immune responses which correlated with protective effects147. Additional work by Sugata and Matsuokaet al. appears to solidify this possibility148 and offers a promising new venue for the future. As in many other leukemias, bone marrow transplantation (BMT) is being used. Curiously, attempts of autologous BMT were unsuccessful149. In contrast, allogeneic BMT resulted in complete remission in some cases, and it has been suggested that the extent of graft-versus-host response correlates with a favorable outcome150. Immune cells in patients with ATL may be tolerized against HTLV-1, most likely because their immune system has developed in the presence of HTLV-1.As mentioned earlier, the prognosis for HTLV-1 diseases is still poor despite almost 40 years of studies on mechanisms and efforts to develop therapeutic strategies. The acute/lymphomatous ATL is very resistant to conventional chemo/radiation therapy. Thus, surface markers specific for HTLV-1–infected CD4 T cells were sought after to enable targeting. The first marker was IL-2Rα/CD25151. So strategies targeting both CD4 and CD8 could be pursued. Here again, anti-CCR4 therapy, which should help eliminate HTLV-1–infected CD4 T cells152, was recently tried with intriguing results in a clinical trial in Japan153. First, the treatment showed quick improvements of clinical symptoms, prompting the field that the presumed low replication of HTLV-1in vivo may need reinvestigation. Anti-CCR4 strategy was among the first to show therapeutic efficacy, so the completion of the clinical trial, including the monitoring of long-term effects, is keenly awaited. As mentioned above, CD8 T cells play as important a role as CD4 T cells in HAM/TSP, so the CD8 targeted therapy can be pursued as well. Studies from NIH labs  demonstrated that one unique characteristic of T cells from patients with HAM/TSP is that they growex vivo without any exogenous stimulation , which they named spontaneous proliferation118, which presumably reflects the constitutive activation of T cells in patients with HAM/TSP. This is because HTLV-1 infection causes CD4 T cells to produce T-cell growth factors such as IL-2 and IL-15155. Thus, inhibition of these cytokines by antibodies121, Jak inhibitors156, or newly described multi-cytokine inhibitory peptide (BNZ132-1or BNZ-1155) synthesized by one of the authors (YT) can subside the T-cell activation in patients with HAM/TSP and is a viable option for treating HAM/TSP for which no established therapy is yet available. In summary, recent years have seen more promising developments for HTLV-1 diseases. The time has come for more testing of novel ideas to cure or reduce morbidity from these diseases.Compared with the pathogenesis of ATL, the pathogenesis of HAM/TSP is more complicated as the damage of spinal cord neuronal cells, the core event causing myelopathy, is mediated by inflammatory responses involving CD8 T cells triggered by HTLV-1–infected CD4 T cells in a bystander manner157; for example, it was not on the WHO’s list of sexually transmitted diseases, and remarkably in recent years under Director Harold Varmus (who was a chicken retrovirologist and molecular biologist), the NCI did not even have it on the list of human tumor viruses. We argued that the mother-to-child transmission can be controlled by screening and educating HTLV-1 carrier pregnant women. Three decades ago, a prefecture in Japan (Nagasaki) started such an endeavor, which reduced the HTLV-1 prevalence in the area from 7.2 to 1.4%158. It is now adopted by the Japanese government into a nationwide anti-HTLV-1 strategy. The horizontal transmission of HTLV-1, by sex and transfer of infected blood cells, is equally preventable. To this end, some countries have initiated HTLV-1 screening in donated blood in the late ’80s. However, blood screening is not yet implemented in any nation in Africa, one of the most highly endemic regions of HTLV-1 infection. An additional emerging concern is the HTLV-1 infection upon organ transplantation which may cause increased development of HAM/TSP with rapid progression (described above). As of now, very few nations (only France and the UK) are conducting HTLV-1 screening in donated organs. Attempts to create funding to facilitate the screening as well as invention of new technologies to make such screening easier and attainable are still needed.As mentioned above, HTLV-1 is among the most carcinogenic agents known to humans and has the additional burden of causing other diseases. Yet owing to its extremely weak dissemination and to its ancient infection of humans (giving time for humans to adapt), HTLV-1 is not considered to be as much of a global threat as other viruses. However, we have seen an instantaneous burst of virulence with other viruses due to mutations , so we should not be so sure. Moreover, in several parts of the world, it is not as uncommon as previously noted. The modes of HTLV-1 transmission and replication suggest that the infection is preventable. Recently, we wrote an open letter to the World Health Organization (WHO), urging them to pay due awareness for HTLV-1, as we strongly feel that HTLV-1’s threat is vastly under-recognizedWhat about a vaccine? From the late ’80s to early ’90s, several groups came out with an HTLV-1 (and STLV) vaccination plan, which was effective but only partially so161. However, our knowledge of HTLV-1 biology, together with the maturation of the vaccination field in general, has vastly advanced since then. The Franchini group (NCI) has used more efficient adjuvants, and the vaccine was proven effective in macaques162. Recent studies suggest that targeting HBZ, a new strategy, may be more effective than conventional strategies163. However, development of anti-HTLV-1 therapeutic/preventive vaccination is severely hampered by the lack of funding for clinical trials.As the conclusion of this review, we argue, on behalf of the global HTLV-1 community, that efforts toward the eradication of HTLV-1 constitute a global health need. At the ninth annual meeting of the Global Virus Network in Melbourne, Australia in September 2017, we met representatives of the Aboriginal community who pleaded to be rescued from their sufferings from HTLV-1. We urge medical/health agencies all over the world that the threat of HTLV-1 is real and there are still unmet medical needs to be resolved and much more awareness is needed. Finally, progress in developing a vaccine for HTLV-1 should be easier than HIV because it has less variation, and may provide important lessons for HIV.


We describe a unique case of human T‐lymphotropic virus 1 (HTLV‐1)‐associated infective dermatitis‐like lesions in systemic lupus erythematosus. This suggests that some lupus patients may have immunological abnormalities resembling to those described in chronic HTLV‐1 infection. We describe a unique case of human T‐lymphotropic virus 1 (HTLV‐1)‐associated infective dermatitis‐like lesions in systemic lupus erythematosus. This suggests that some lupus patients may have immunological abnormalities resembling to those described in chronic HTLV‐1 infection. Lupus skin lesions include specific skin lesions histologically characterized by an interface dermatitis  and nonspecific symptoms such as alopecia, livedo, Raynaud's phenomenon, palmar erythema, periungual telangiectasia, purpura, and aseptic pustulosis of the folds. We report a case of a 17‐year‐old girl who initially presented a chronic exsudative eczematous eruption with lesions of the scalp, trunk, arm, and face with peri‐orifical distribution and frequent superinfections with staphylococcus aureus and b‐hemolytic‐streptococci. Skin lesions semiology mimicked clinical symptoms seen in Human T‐lymphotropic virus 1 (HTLV‐1)‐associated infective dermatitis (IDH). These skin lesions were associated with Evans syndrome  and atypical colitis with a nonspecific lymphocyte infiltrate histology and anti‐Saccharomyces cerevisiae antibodies positivity. Treatment consisted of oral corticosteroid for cutaneous, hematologic, and digestive diseases that allowed almost complete remission. Nine years later, she developed systemic lupus erythematosus with skin, articular, and hematological involvement.HTLV‐1 infection induces immune dysregulation that leads to IDH in infancy. We describe an original case of IDH‐like lesions in SLE, which suggests that some lupus patients may have immunological abnormalities resembling those described in chronic HTLV‐1 infection.Systemic lupus erythematosus (SLE) is a chronic autoimmune disease with a pathophysiology based on the formation of self‐antibodies and immune complexes, closely related to environmental factors and genetic predispositions.We report the case of a patient who had skin lesions clinically mimicking IDH and subsequently developed autoimmunity and SLE.2. A trunk lesion's biopsy showed spongiotic dermatitis. A pustule's histology showed ostio‐suppurative folliculitis. Several pustule samples were positive for staphylococcus aureus and b‐hemolytic‐streptococci superinfection. Multiple antibiotic treatments improved skin lesions over short periods.A 17‐year‐old girl, with Evans syndrome history  treated with oral prednisone and IV immunoglobulins, presented with papulo‐erythematous squamous, crusted and pruriginous skin lesions of the scalp, the trunk, the back, the arms, and the face with peri‐orifical distribution  antibodies and hypocomplementemia. She was diagnosed with SLE and hydroxychloroquine treatment was started (400 mg/d).One year later, while she had stopped hydroxychloroquine, she had a SLE flare with hematological, cutaneous Figure , and art3Thus, our patient presented two well‐distinct dermatological charts: first, an IDH‐like eruption with severe eczematous skin lesion with major facial involvement then secondarily systemic lupus erythematosus with typical cutaneous lesions.According to infective dermatitis diagnosis criteria proposed by La Grenade et al,+ T lymphocytes and can modify T‐lymphocyte cell function. HTLV‐1‐infected CD4+ T lymphocytes may exhibit altered signaling cascades and transcription factor activation, leading to changes in cell behavior that may trig inflammatory reactions that can break immune system tolerance.HTLV‐1 is known to induce several diseases such as HTLV‐I‐associated myelopathy/tropical spastic paraparesis (HAM/TSP) and adult T‐cell leukemia (ATL) but may also be associated with autoimmune disorders such as Sjogren's syndrome, polyarthritis, thyroiditis, or uveitis.Tax, an essential phosphoprotein playing a role in HTLV‐1 transcription, is known to affect several transcription factors including CREB/ATF, NF‐κB, AP‐1, SRF, and Nuclear factor of activated T cells (NFAT), as well as a number of signaling cascades involving Rho‐GTPases and Janus kinase (JAK)/signal transducer and activator of transcription (STAT), thus altering the transforming growth factor‐β (TGF‐β) cascades..The expression of forkhead/winged‐helix transcription factor (FOXP3), which is an important transcription factor, has also been reported to be altered in patients infected with HTLV‐1. FOXP3 is an essential transcription factor for the differentiation, function, and homeostasis of regulatory T cells (Tregs). Irregularities in the expression of FOXP3 may lead to loss of immune tolerance and the probable development of autoimmune diseasesFurthermore, SLE is an autoimmune disease with autoantibody formation and cell immunity disturbance. We currently find altered suppressor T‐cell to helper T‐cell ratios. Abnormalities in T‐cell function include T‐cell lymphopenia, impaired apoptosis, hyper‐reaction to signaling to T‐cell receptors, expression of activated antigens, defects in deletion of cells with high affinity for self‐antigens, and alteration of responses to cytokines and lymphokines.Thus, a possible association between SLE and HTLV‐1 has been discussed.In summary, we describe a unique case of IDH‐like lesions in SLE. This suggests that some lupus patients may have immunological abnormalities resembling to those described in chronic HTLV‐1 infection.None.First author: written the manuscript. Second author: edited and proofread the manuscript. Third and fourth authors: examined and treated the patient, analyzed and described anatomo‐pathological samples. Fifth and sixth authors: examined the patient and participated in therapeutic decisions. Seventh author: examined and followed the patient, edited and proofread the manuscript.


Drosophila developing ovarian soma through a Smad-independent pathway to shape the distribution of BMP signal within the niche, impacting germline stem cell (GSC) recruitment and maintenance. Somatic Tkv promotes Egfr signaling to silence transcription of Dally, which localizes BMP signals on the cell surface. In parallel, Tkv promotes Hh signaling, which promotes escort cell cellular protrusions and upregulates expression of the Drosophila BMP homolog, Dpp, forming a positive feedback loop that enhances Tkv signaling and strengthens the niche boundary. Our results reveal a role for non-canonical BMP signaling in the soma during GSC establishment and generally illustrate how complex, cell-specific BMP signaling mediates niche-stem cell interactions.In developing organisms, proper tuning of the number of stem cells within a niche is critical for the maintenance of adult tissues; however, the involved mechanisms remain largely unclear. Here, we demonstrate that Thickveins (Tkv), a type I bone morphogenetic protein (BMP) receptor, acts in the  •Tkv, a BMP receptor, in the developing ovarian soma controls fertility•Knockdown Tkv in the developing soma causes ectopic germline stem cell (GSC) accumulation•Tkv in the soma controls GSC number by limiting BMPs within the GSC niche•BMP-Tkv signaling in the soma limits GSC number via Egfr and Hh signaling In this article, Hsu and her colleagues show that Tkv, a type I BMP receptor, functions in the developing ovarian soma to control the size of germline stem cell (GSC) pool via a Smad-independent pathway. BMP-Tkv signaling in the soma limits BMP signals within the GSC niche via Egfr and Hh signaling to ensure that germ cells outside of the niche undergo proper differentiation. Drosophila ovary as a model because of its relatively simple architecture during developmental and adult stages, as well as its well-characterized germline stem cells (GSCs) and stem cell niche  stage . The antDrosophila ovary, the BMP homolog, Decapentaplegic (Dpp), is the major niche-derived stemness factor for GSC recruitment and maintenance. GSCs express Saxophone (Sax) and Thickveins (Tkv) as type I receptors and Punt as a type II receptor. To restrict delivery of the Dpp signal to GSCs, niche cap cells also express Division abnormally delayed , which is a glypican protein that binds and stabilizes Dpp on the extracellular matrix. After binding to receptors on GSCs, the Dpp signal is transmitted to Mothers against Dpp , which forms a complex with Medea  to silence transcription of Bag of marbles (Bam), a differentiation factor. While the canonical signaling pathway is the only previously identified mechanism by which Dpp regulates GSCs in the Drosophila ovary, BMP signaling is widely known to modulate gene expression in other biological systems via various non-canonical pathways, including the mitogen-activated protein kinase cascade (Bone morphogenetic protein (BMP) signaling is highly conserved and controls a variety of developmental processes, as wells as stem cell maintenance during tissue homeostasis . BMP sig cascade .tkv expression in larval gonadal somatic cells resulted in the appearance of ectopic GSCs at the adult; however, gene silencing in TF cells did not. Instead of signaling through BMP canonical proteins, genetic and RNA sequencing (RNA-seq) analyses revealed that ICs expressing Tkv had activated Hh and Egfr signaling in parallel to limit GSC number. As such, evidence of Hh and Egfr signaling was absent in gonads carrying tkv-knockdown (tkvKD) somatic cells. Moreover, compensatory stimulation of either Hh or Egfr signaling partially prevented the formation of ectopic GSCs in tkvKD background, but disruption of either signaling pathway did not affect signaling through the other pathway. Based on these findings, we conclude that Dpp signaling in the GSC niche shapes the Dpp tissue distribution via non-canonical modulation of Hh and Egfr signaling to limit the number of GSCs recruited to the niche.In this study, we found that, in addition to its known role in maintaining GSC identity via Smad signaling, Tkv plays a crucial role in gonadal somatic ICs to confine the Dpp signaling zone for GSC recruitment via a non-Smad pathway during ovary development. Tkv was present in TF and ICs of larval gonads, while in the adult ovary, Tkv was observed in TF, cap and ECs of the germarium. Silencing UAS-RNAi lines from the National Institute of Genetics (N). RNAi expression was driven by bab1-GAL4, which is expressed in all somatic cells, but specifically in TF cells, cap cells, and anterior ECs at the late pupal and adult stages  of newly eclosed (D1) flies carried two to three GSCs with anterior anchoring of fusomes that were directly adjacent to niche cap cells. Each germarium also carried 2 ± 1.1 CBs, the immediate daughter cells of GSCs, which were identified by the presence of a spherical fusome (spectrosome-containing cells), but were positioned distal to niche cap cells   F and 1K,587-GAL4 G and 1K,NAi line H and 1K. hh-GAL4 K and S1L hh-GAL4 I–1K. Notrphology .tkv mRNA transcripts were reduced in 1-day-old bab1>tkvRNAi (N) and c587>tkvRNAi (N) ovaries , which translocates to the nucleus, where it activates expression of daughter against Dpp (dad) and suppresses bam transcription (dad-lacZ), and Bam  and c587>tkvRNAi(N) germaria. In the control germaria  in 1-dagermaria A, pMad wgermaria A, while,he niche B and 2C.ermarium D, but, irm cells E and 2F.germaria G–2I. It germaria . To furtgermline J. In somgermaria K and 2L,bab1>tkvRNAi (N) and c587>tkvRNAi(N) ovaries at the LL3 stage  or bab1>tkvRNAi(N) germaria by qRT-PCR, RNA-seq, and a dpp transcriptional reporter, dpp2.0-lacZ . Knockdown of tkv alone, using bab1-GAL4, still resulted in few SCCs . Interestingly, simultaneous knockdown of tkv and dpp using bab1-GAL4 dramatically increased the number of SCCs   K–S3M. Thmulation M–3P. Sindally (encodes a glypican that facilitates distribution of Dpp) to sharpen the BMP gradient in the larval gonad, such that the first row of PGCs (next to TFs) will be recruited and maintained as GSCs  gonads (c587>tkvRNAi(N) germarium (bab1>tkvRNAi(N) ovaries  in somatic gonadal precursors after the mid-L3 stage driven by either bab1- or c587-GAL4 caused an elevation of Egfr signaling in adult ECs  or throughout development  ovaries as compared with control and bab1>tkvRNAi(N)  or tkvKD driven by c587-GAL4 (c587>tkvRNAi(N) germaria with dally sense probes did not show any signal  G. We con control H, dally 587-GAL4 I and 4J.y signal K, confirtkv with concurrent overexpression of a constitutively active form of Egfr, egfrλTop  germaria  in the soma, also caused SCC accumulation  ovaries  gonads by knockdown of ptc (encodes a Smo suppressor) from early pupal to adult stages, or during all developmental stages, also partially suppressed SCC accumulation  ovaries, wherein Egfr signaling was not affected. We also noticed that the blunted EC membrane protrusions in somatic bab1>tkvRNAi(V) germaria were rescued by ptcKD . This atkv-A isoform, induces canonical Dpp signaling in PGCs within the niche to specify a GSC fate, while tkv-D-encoded Tkv mediates non-canonical Dpp signaling through Egfr and Hh in the soma to prevent Dpp leaking from the niche. Although we do not know how Tkv affects hh transcription, our genetic data suggest that Tkv acts upstream of Egfr, since overexpressing a constitutively active form of Egfr suppressed tkvKD-induced SCC accumulation. However, our RNA-seq results revealed that transcript levels of egfr and genes encoding Egfr ligand (Spitz)   and modu (Spitz)  were nottkv knockdown was different. Luo et al. suppressed tkv expression in ECs at the adult stage, while we manipulated tkv expression in the soma during developmental stages. Second, the molecular action of Tkv in limiting GSC number is different. In the previous study, knockdown of tkv in adult ECs did not affect Egfr signaling or dally expression, and overexpressing the extracellular domain of Tkv significantly reduced SCC number in tkv-knockdown germaria. Therefore, the authors concluded that expression of Tkv in adult ECs serves as a sink to sequester Dpp signals that may spread outside of the niche. In contrast, our results showed that Egfr signaling is dramatically reduced, and that dally becomes ectopically expressed in ICs/ECs when tkv expression is eliminated in the ovarian soma during development. These events were shown to be functionally important, because activation of Egfr signaling or knockdown of dally expression in the tkvKD ovarian soma during development were sufficient to reduce SCC number. Lastly, we also found that, in the developing soma, Tkv promoted Hh signaling, which may control membrane extension of ECs for germ cell differentiation. Knockdown of tkv in the soma of larval ovaries resulted in decreased Hh signaling, and forcing Hh signaling in tkvKD somatic cells reduced SCC accumulation. Therefore, we conclude that, during developmental stages and at the adult stage, ovarian somatic cells most likely use different strategies to prevent Dpp leakage from the niche in order to maintain a proper number of GSCs. However, we could not rule out the possibility that Tkv may promote IC or EC proper differentiation, which is required for GSC progeny differentiation. In this case, SCC accumulation in the germaria developed from the somatic tkvKD gonad is a consequence of failed differentiation of ICs/or ECs.tkv in developing ovaries results in formation of ectopic GSCs. In addition, somatic tkvKD ovaries exhibit a reduction of hh transcript level, which may lead to a reduction of dpp transcript levels. These results suggest that Hh signaling is sandwiched by upstream and downstream Dpp signaling in the control of GSC number; as such, Dpp signaling activates transcription of hh to promote dpp transcription, which in turn activates Dpp signaling in the soma. In adult female flies, both promotion and suppression of Dpp have been reported as effects of Hh signaling in ECs  containing the first exons of tkv-B, -C, and –D transcripts, followed by a lacZ reporter. This construct was used to monitor tkv expression (UAS-RNAi lines against tkv (N no. 14026-R3 and V no. 3059), punt (V no. 107071), mad (B no. 31315 and V no. 12635), hh (N no. 4637-R2), smo (B no. 43134), dally (N no. 4974-R1), dpp (N no. 9885-R2), ptc (N no. 2411R1), and GFP (B no. 9331 and B no. 9330) were obtained from National Institute of Genetics (N), Vienna Drosophila Resource Center (V), or Bloomington Drosophila Stock Center (B). The efficiency of the dppRNAi line was examined in this study , UAS-egfrDN (B no. 5364), UAS-egfrA887T (B no. 9533), and UAS-egfrλTop 3.1  have been described previously .Fly stocks were maintained at 22°C–25°C on standard medium, unless otherwise indicated. activity . dpp2.0-y of dpp . P2-lacZpression . UAS-RNAtudy see I and S4Jeviously . UASp-mCeviously . Flies epression . Other gOther detail experimental procedures are shown in C.-Y.T., H.J.H., and Y.-H.S. conceived and designed the experiments. C.-M.L., C.-Y.T., Y. Cho, S.-M.Y, K.-Y.L., and Y.-H.S. performed the experiments. Y. Cai provided fly lines and reagents, discussed and interpreted results, and troubleshot experiments. C.-Y.T. and H.-J.H. analyzed the data and wrote the manuscript. O.A., K.-Y.L., and E.R. finalized the revised experiments.


Twenty-eight years (1984–2011) of broad-scale Landsat Thematic Mapper assessments confirm that shrub cover has been relatively stable in recent decades regardless of grazing regimes and landforms with the exception of the proliferation of succulents at lower elevations (verified by repeat photography acquired in 1987 and 2015) where the physical environment is the harshest, reflecting elevated temperature and winter precipitation deficit. Warmer, drier future climates are predicted to reduce woody plant carrying capacity and promote a shift to xerophytic succulents.Shifts in the abundance of grasses and woody plants in drylands have occurred several times during the Holocene. However, our understanding of the rates and dynamics of this state-change in recent decades is limited to scattered studies conducted at disparate spatial and temporal scales; the potential misperceptions of shrub cover change could be remedied using cross spatiotemporal scale analyses that link field observations, repeat ground-level photography and remote sensing perspectives. The study was conducted across a semi-arid landscape in southern Arizona. Local data from long-term transects revealed three distinct chronological phases of shrub cover change: expansion (1961–1991, 0.7% y Ecological stability is generally defined as a system maintaining a dynamic equilibrium through time . When ecAlthough the proliferation of woody vegetation in drylands is recognized as having potentially important impacts on terrestrial carbon pools, the lack of information on the trends of shrub abundance is a major source of uncertainty in assessing how this vegetation change has influenced the carbon cycle . In NortOur understanding of how fundamental ecosystem processes change with herbaceous-to-woody state-changes is inconclusive ; a synophttps://www.ag.arizona.edu/srer/) in southeastern Arizona, USA as a model system to investigate the stability of woody plant cover in an era of climate and land use change. Shrub encroachment at this semi-desert grassland ecosystem began in the early 1900s and has been well-documented with repeat ground photography and transects  occur across the elevation gradient. The range of vegetation types within the SRER encompasses about 20% of the total amount in Southwest, and is representative of many arid and semi-arid regions of the Sonoran Desert  . Establin Desert .P. velutina within a 71 ha area were cleared in 1976 by chaining. The main focus of this study was to investigate the recent trend of woody cover abundance afterseveral decades of woody plant encroachment. Therefore, these burned or shrub cleared areas of known destructive changes were excluded from our analyses since the systems may be still in the recovery phase.Prior to 1902 the southwestern USA experienced heavy, unregulated livestock grazing. Shortly after the SRER was established in 1902, livestock were excluded and then re-introduced in 1916. The site was then managed under yearlong (YL) livestock grazing until 1957 when various rotational grazing regimes were implemented. During 1972–2007, YL and the Santa Rita Grazing System (RG) have been consistently applied in one  = 1,092 ± 35 m a.s.l.) and four  designated pastures, respectively . Those rn = 132) representing a range of topo-edaphic settings. We used 81 transects widely distributed across the SRER, after excluding transects experiencing disturbance and those with prolonged data gaps (Projected shrub cover (defined as the planometric view of percentage of ground surface covered by shrub canopy) between 1957 and 2012 was assessed via archived data from permanent line transects  precipitation and temperature data for summer (April–September) and winter (from previous October to current March) were acquired from the Parameter-elevation Regressions on Independent Slopes Model PRISM, . Summer http://glovis.usgs.gov/) with minimum cloud contamination to quantify temporal changes in woody cover from 1984–2011. These images contain six 30 m visible, near infrared and shortwave infrared bands, and one thermal band. All images were geo-registered  by the provider prior to acquisition and converted to surface reflectance using ACORN .Greenness in drylands derived from pre-monsoon Landsat imagery can be treated as live woody cover since herbaceous plants are mostly senescent and only deep-rooted shrubs can sustain green leaves through the support of relatively stable ground water . The semR2, R2. Assumptions were also made that the same degree of decrease (less than the negative adjusted trend) were recognized as woody cover “decline” sites; areas with trends in between “increase” and “decline” were labelled as “stable”. Regions with apparent changes (increase or decline) in woody cover were further investigated by examining spatiotemporally corresponding field repeat ground-level photography from the SRER Digital Archive (https://www.ag.arizona.edu/srer/) and carrying out site visits.A probabilistic spectral mixture analysis model was used to unmix fractional green woody vegetation cover from each pixel on all images, and rectified to ground-measured projected woody cover by referring to ness R2, . This scChange or stability in woody cover was assessed in relation to grazing regimes  and landforms. Definitions of “stability” are varied and depend on the structural attributes or functional processes of interest and spatial/temporal scales . Here, w−1 (p = 0.002) or total 11.5% with the mean (± sd) woody cover of 22.4 ± 6.1%, −1 , 24.6% increase with the mean (± sd) woody cover of 21.4 ± 7.3%), followed by (ii) an abrupt decline phase  or 14.1% loss of shrub cover with the mean (± sd) woody cover of 25.2 ± 2.4%) and (iii) a stabilization phase , shrub cover fluctuated between 22% and 25% with no net change; mean (±  sd) woody cover = 23.6 ± 1.0%).A comparison of 1961 (the lowest starting point) and 2012 (end point) field transect data indicated little change in shrub cover over the 51 y period  mean summer and winter precipitation averaged 236 mm and 155 mm, respectively, with temperature averaging 23.8 °C and 12.7 °C, respectively. Deviations from these long-term means during the 1961–2012 period of field transect data are shown in p = 0.06) than the 26.6 ± 5.3% estimates from field transects during the corresponding time period (1984–2011). Woody cover was generally highest along arroyos and at upper elevations. Although mean woody cover values fluctuated from year to year, a tendency toward recession (about 14% decline and 0.5% y−1 (p = 0.01)) with lower year-to-year variation since 1984 was observed (Mean (± sd) woody cover across SRER was 20.6 ± 7.9% over the 28-year satellite record , which wobserved . The areobserved . Elevatiobserved  generallobserved  after thobserved  for modeobserved  to minim−1 during the field woody cover encroached period (1961–1991) (R2 = 0.14) (−1) (Opuntia engelmannii) proliferation in terms of its frequency of occurrence and % cover relative to that in 1984. Over the same period, these metrics of shrub (mainly P. velutina) abundance declined and then stabilized   by the m = 0.14)  of remot14) (−1) ; sites e14) (−1)  and 4A rabilized .−1 (or −0.27–0.08% of shrub cover during the satellite observation period), sd = 0.008–0.069% y−1) and grazing regimes , sd = 0.039–0.065% y−1). An evaluation of grazing regimes and landforms controlling for elevation also failed to reveal pronounced woody cover trends , sd = 0.008–0.072% y−1). Differences among these groups were negligible with no biological significance; therefore, no statistical analysis was performed.Directional trends in woody cover abundance were minimal to non-existent on all landforms , interacting with changes in disturbance  regimes  with no pronounced evidence of climatic anomalies  and 2C,  regimes . Compari regimes . The end regimes . The secnuisecta ; for longulation . Woody pgulation  and 2C bAfter the rapid period of woody cover decline, consecutive years (1998–2012) of drought occurred, especially during the winter months. Above-average temperature also occurred during this period. These regional meteorological records were in-sync with the broader trend in “global-change-type droughts” which have caused profound impacts on vegetation . DrylandOne advantage of remote sensing is to provide broad-scale and spatially continuous tracking of woody cover through time. In the Sonoran Desert, the orographic effect plays a crucial role in ecosystem productivity where more precipitation is received at higher elevation . The tenThis study highlights the strength of remote sensing techniques to produce spatially extensive information across different land uses, which is not feasible for a field inventory program even at this well-managed experimental site. A correction procedure Opuntia spp.). The proliferation of cacti might reflect elevated temperature and winter precipitation deficits  in recet growth . These cvelutina  and promvelutina . A similvelutina . Paleoecern Utah . This raern Utah . If this10.7717/peerj.5474/supp-1Supplemental Information 1Major landforms of the study site. The landform codes correspond to Click here for additional data file.


Various reports have suggested that secreted frizzled-related protein (SFRP) 5 (SFRP5) plays a regulatory role in the processes of cellular proliferation and differentiation, by means of inactivating the Wnt/β-catenin signaling pathway. Recently, SFRP5 has been identified as an anti-inflammatory adipokine, which may be induced during preadipocyte proliferation, differentiation, and maturation. This review aims to identify the recent progress in the research and development of SFRP5 that can play a role in influencing lipid metabolism, inflammation, and type 2 diabetes mellitus (T2DM). Recent evidence has indicated that SFRP5 is capable of stimulating adipocyte differentiation via inhibition of the Wnt/β-catenin signaling pathway. In addition, SFRP5 binding with wingless-type murine mammary tumor virus integration site family, member 5A (Wnt5a), inhibits the activation of c-Jun N-terminal kinase (JNK) downstream of the Wnt signaling pathway. An antagonistic relationship has been found between the reductions in inflammatory cytokine production and serine phosphorylation of insulin receptor substrate-1 (IRS-1) in regard to inhibition of insulin signaling network. By this mechanism, SFRP5 exerts its influence on metabolic function. Based on our review of the current available literature, we support the notion that SFRP5 can be used as a therapeutic target in the treatment of T2DM. SFRP5 gene is composed of three coding exons, all of which are located on chromosome 10q24.1. SFRP5 has been reported to exert its effects by regulating the Wnt signal transduction, by competing with membrane frizzled receptors that function as a binding domain for secreted Wnt ligands [Secreted frizzled-related proteins (SFRPs) consist of five identified secreted glycoproteins, which have been identified as negative modulators of the Wnt signal transduction pathway ,2. SFRP5 ligands .As functional antagonists, both the Wnt family and SFRPs control multiple biological processes, including that of embryonic development, inflammation, and immunity . SFRPs bCCND1, c-myc, Axin2, and MMP-7 [307 phosphorylation [Wnt signaling has been categorized into three distinct pathways: the canonical Wnt signaling pathway involving β-catenin signaling, the non-canonical planar cell polarity pathway, and the Wnt and calcium pathway . The Wntnd MMP-7 . Reportsrylation . Thus, Srylation . Anti-inrylation . SFRP5 nrylation . UnderstSFRP5 has been found to help increase lipid accumulation in adipocytes in order to allow adipose tissue expansion to occur. These effects are a result of increased mitochondrial respiration elicited by SFRP5 suppressive effects on oxidative metabolism by blocking Wnt signaling by means of preventing the binding of Wnt proteins to their respective receptors . The rolIdentification of increased levels of SFRP5 expression in the fat tissue of obese mice and humans have been reported. The expression of SFRP5 is slowly induced in the process of differentiation of white and brown adipocytes and highly elevated in mature adipocytes . MultiplSFRP5 accelerates adipocyte differentiation and lipid storage in adipocytes by repressing the Wnt signaling, thereby further attenuating inflammation . SFRP5 iAs an anti-inflammatory adipokine, SFRP5 could be negatively modulated in the development of obesity, contributing to an unfavorable metabolic phenotype . AccordiT2DM is significantly influenced by chronic low-grade inflammation as a response stimulated by metabolic stress . In respSFRPs share an antagonistic relationship with Wnt signaling through binding to Wnts or their receptors in the plasma membrane . SFRP5 iA majority of studies supported the beneficial action of SFRP5 in glucose tolerance . HoweverIn this review, we have speculated that the activation of the Wnt signaling pathway can facilitate chronic low-grade inflammation in adipose tissue. Despite the ongoing and available research, there is a need for further investigation to determine whether the Wnt signaling pathway can exclusively directly affect adipose tissue inflammation in obese individuals or physiological functions. However, the relationship between SFRP5 and the Wnt signaling pathway transduction in the liver and skeletal muscles as well as the insulin signaling network also requires further exploration. Do the intravenous injections of SFRP5 directly block the Wnt signaling pathway in the liver and skeletal muscles or do they indirectly enhance the insulin sensitivity? Further elucidation into whether SFRP5 levels are regulated during the development and progression of obesity and diabetes mellitus is required, since there remain elements of controversy as to whether they increase all the time or fall below at particular point, thereby influencing metabolism. In conclusion, this review speculates the role of SFRP5 in the pathogenesis of lipid metabolism, inflammation, and T2DM. Further understanding of the biological functions implicated may pave the way for SFRP5 to serve as a promising novel therapeutic target in the treatment of obesity, T2DM, and other metabolic diseases.