In recent years, post-installed anchors are widely used to connect structural members and to fix appliances to load-bearing elements. A bonded anchor typically denotes a threaded bar placed into a borehole filled with adhesive mortar. The high complexity of the problem, owing to the multiple materials and failure mechanisms involved, requires a numerical support for the experimental investigation. A reliable model able to reproduce a system’s short-term behavior is needed before the development of a more complex framework for the subsequent investigation of the lifetime of fasteners subjected to various deterioration processes can commence. The focus of this contribution is the development and validation of such a model for bonded anchors under pure tension load. Compression, modulus, fracture and splitting tests are performed on standard concrete specimens. These serve for the calibration and validation of the concrete constitutive model. The behavior of the adhesive mortar layer is modeled with a stress-slip law, calibrated on a set of confined pull-out tests. The model validation is performed on tests with different configurations comparing load-displacement curves, crack patterns and concrete cone shapes. A model sensitivity analysis and the evaluation of the bond stress and slippage along the anchor complete the study. Post-installed mechanical and adhesive anchors provide the opportunity to design and build flexible new structures, but also to renovate or strengthen old buildings. The usage of fastening systems has been increasing steadily during the last few decades. In particular, bonded anchors are a valuable and relatively cost-effective fastening type with a different working principle compared to more traditional mechanical anchors. Mechanical anchors typically transfer load to concrete at the anchor’s lower end due to mechanical interlocking and/or friction. For bonded anchors, the load is transferred through the thin adhesive mortar layer along the entire bonded length. The different working principle introduces other failure mechanisms that are not present for mechanical anchors, as they are related to  bond failure (see ).Different ways have been pursued in the literature to predict the performance of adhesive adhesive anchors. They can be classified into (a) empirical  models calibrated on databases and (b) numerical models. Among the analytical models proposed for the combined concrete cone-bond failure mechanism, summarized by Cook et al. in , the simWith increasing computational resources and steadily improving modeling concepts, numerical modeling has become a reliable tool for structural analysis, but also for the investigation of local details such as fastening systems. Many concrete models have been developed during the last few years to describe the behavior of concrete, both for design and research purposes. Finite element models and discrete models approach the problem from different perspectives, and each one of them has advantages and disadvantages. Software used by engineers for structural analysis often does not contain accurate enough constitutive models for the base material as shown in , where nFinite element models based on the damage plasticity theory such as the CC3DNonLinCementitious2implemented in ATENA (see ), have aOther classes of finite element constitutive models are based on the microplane theory  are a valuable alternative for concrete modeling. The LDPM developed by Cusatis and co-workers (see ) is a diThe approach followed by this research team is to model the complete behavior of the singular components. Concrete and adhesive mortar are tested in order to determine their respective mechanical properties, depending on their curing degree, which is affected by time and the history of environmental conditions. Different geometries and curing conditions were tested for different ages of concrete. Compressive and tensile strength, elastic modulus and fracture energy were determined at 3, 8 and 28 days. Additionally, creep and shrinkage tests were performed to gain insights into the long-term behavior of concrete under sustained loads. Dog-bone specimens and compact tension specimens are tested for different curing levels to obtain elastic and fracture properties of the adhesive mortar. Furthermore, accelerated creep tests were performed to obtain the multi-decade creep behavior of this particular material. In order to transfer all of the material information to the system response, numerical simulations are required. The ultimate goal is to create a tool that is able to predict reliably the life-span of bonded anchor systems under sustained load, also in the presence of deterioration processes of various types, which can involve all or only single system components, i.e., the mortar layer, steel bar or the concrete member. However, a reliable long-term prediction model needs to be able to accurately predict the short-term behavior first. This publication focuses on the calibration and validation of a numerical model for bonded anchors under quasi-static tensile loading. For the first time, a discrete concrete model is used to systematically study the behavior of bonded anchors due to its realistic prediction of damage localization and propagation. Most likely, this is the source of the achieved excellent prediction quality, both in terms of load displacement response and failure mechanism. The experimental data used for this paper are created internally ensuring consistency and quality of the results and, thus, provide a reliable basis for the model development and validation.Fastening systems can be represented, as any other structural system, at different scales, according to the scope of the investigation. In order to design a building, for instance, concrete is taken as a continuum elastic material. For local problems, such as moisture transport and concrete hydration in structural details on the other end, the cement paste and aggregates should be modeled, and the concrete should no longer be considered a continuum. A bonded anchor pull-out problem could be modeled with 2D axisymmetric elements or 3D elements. With the help of 2D axisymmetry, as for other 2D approximations such as plane stress or plane strain, a 3D problem can be reduced to a 2D problem. The necessary, but also sufficient conditions to simulate a real 3D problem via an axisymmetric 2D reduction are the symmetry of loads, geometry and material. Depending on the level of detail that one wants to meet, all three aspects of the problem or none of them can be considered axisymmetric. The intent of this paper is to propose a model that can be used later on e.g. for sustained load simulations, which involve the aging of the components, heat transfer and moisture diffusion, concrete pre-damage and different loading conditions. The hypothesis of perfect symmetry would be ideal for the specific case of pure tension, but too restrictive or even prohibitive for more general future applications. Derived from the above-mentioned considerations, a 3D model for the concrete base material seems to be required to deal with fastening system problems. Regarding the anchor and the mortar layer, as can be seen in Generally, the best choice is the simplest model that satisfies a given set of constraints, and since, at the moment, the interaction with the steel failure and micro-cracking of the adhesive mortar layer are not of interest, the modeling concept based on a 1D threaded bar and a 2D mortar interface have been selected.One of the assumptions of the experimental campaign is that in all of the pull-out tests, the threaded bar remains in its linear elastic regime. For this specific reason, threaded bars of steel class 12.9 have been used for all of the pull-out tests. To simulate the anchor, a simple linear elastic material and 1D beam elements (the formulation of which is based on the Bernoulli–Euler beam theory) have been used. However, for systems where the local stress in the steel elements reaches higher levels than the yield strength, a more realistic elasto-plastic behavior should be used instead of the simpler elastic relationship. The choice of the proper constitutive law, as shown in , is esseThe LDPM is a concrete model that simulates the mechanical interaction of coarse aggregates embedded in a cementitious matrix. The full description of LDPM is reported in Cusatis et al. see ,18). In . In 18])l is the distance between the two particles; The generation of the geometrical representation of the LDPM structure follows the procedure explained below. The discrete mesh is dependent on the mix design and particularly on the minimum aggregate size y Bažant  and alsoy Bažant . Before hrinkage , expansihrinkage  or corrohrinkage . Visco-eshown in .A stress-slip constitutive model  describex inside a cell, which moves rigidly with the cell, can be expressed in terms of velocity as: As already described above, the LDPM domain is composed of a number of cells that interact through contact facets used for the definition of constitutive equations. The movement of a general point c and a denote concrete and anchor points, respectively. The internal elastic energy of the constraints along the anchor axis is a bilinear positive definite symmetric operator: K is the stiffness of the concrete at the anchor interface and S is the entire bar length. The total work performed per unit of anchor length, added to the internal energy, must be zero. From this balance, for an arbitrary virtual displacement function, Having no borehole modeled, each point on the virtual anchor surface has a companion point that belongs to an LDPM cell. The relative displacement orrosion , fiber-rorrosion ,30 or ths is the slippage.What is macroscopically perceived as bond is the result of many mutually-interacting components and mechanisms. These are deformations in and the damage of a thin mortar layer, adhesion and interface damage between steel and mortar, as well as between mortar and concrete. In the latter case, also the surface roughness, depending on the borehole creation, the cleaning and the permeation of the mortar into the concrete may play a role. At later damage states, when the interface has failed, frictional effects further contribute to the load transfer. For the purpose of this investigation, all of the above phenomena are collectively captured by a shear stress-slip law, neglecting the effects of transversal stresses. The basic response is elastic, with stiffness slip law b. α is tA typical bonded anchor system describes a threaded steel bar that is installed in a typically drilled hole in a concrete member. Loads are transferred through a thin adhesive mortar layer. Unfortunately, direct system tests only allow limited insights into the behavior of such systems that are typically limited to surface deformations and global response quantities. Numerical simulations provide a remedy and can represent powerful tools that give direct access to the three-dimensional distribution of stresses and strains, if the model is properly calibrated. An unbiased model calibration is a prerequisite for truly predictive investigations, and it requires a number of different tests on all involved materials, as well as for the system in order to obtain unique estimates of all of the relevant concrete and bond properties. It is essential to keep some of the experimental data for the later validation. Concrete compressive strength, tensile strength, elastic modulus and fracture energy are obtained for the three concretes at 3, 8 and 28 days. On the same days, confined and unconfined pull-out tests (the explanation of the terminology is in the related paragraphs) were performed using M12 threaded bars with a 90-mm embedment depth. The steel class of the threaded bar used was 12.9 with a yield strength of 1080 MPa, which is the strongest commercially available steel quality in order to remain in the elastic regime throughout the entire test. For all of the pull-out tests, the borehole diameter was 14 mm. Additionally, at 28 days, tests on anchors with 20 mm of unbonded length at the loaded end were performed for three different embedment depths. The concrete cone shape was recorded by photogrammetric means. Additionally, some cores were taken from the concrete slab after the pull-out test, centered at the original location of the anchor, in order to compare the simulated and actual failure mechanisms.A complete characterization of concrete properties entails on top of standard tests such as cube compression and cylinder compression test  also notched three-point bending tests for the determination of fracture properties and Brazilian splitting tests to obtain the indirect tensile strength. The results of the tests that were performed at a concrete age of 28 days are shown as either stress-strain or load-CMOD (crack mouth opening displacement) curves.E and fracture energy K) of the linear part.imen see a. The elimen see b having imen see d accordid is the nominal diameter of the threaded bar and x-axis represent the average displacement measured by the two LVDTs. In the figures, the mean value is provided for the peak load, K, of the linear part.A thin layer of adhesive mortar is used to bond the threaded bar to the concrete. The bond behavior is determined by the material properties of the mortar, its geometry and the properties of the two interfaces between concrete and mortar and mortar and steel. The material properties of adhesive mortars include tensile, compressive and shear strength, two elastic constants and fracture properties. Reducing the mortar layer to an interface reduces the number of relevant properties to in-plane interface stiffness and strength and parameters describing its softening behavior. These properties were identified based on pull-out tests with close support, which are typically referred to as confined tests. For the confined test, a ring with an inner diameter of In In order to extend the model validation to different embedment depths, five pull-out tests were performed in a confined configuration for each of the three different bonded lengths The prerequisite concerning the modeling strategy is that, to obtain an accurate bonded anchor model response, all of the parameters of the materials involved in the fastening system need to be correctly calibrated, and experimental boundary conditions need to be well reproduced. As already mentioned in the introduction, the calibration will start from the concrete material. The calibration of the bond-law (stress-slip parameters) can only be performed after the concrete calibration and validation because the model used for the bond-law calibration involves concrete . Once all of the material properties are calibrated, the system model will be validated on a set of unused experimental data without changing or tuning any of the parameters.c), water to cement ratio  and pull-out tests with different embedment depth are available. Each one of these experimental results will be used for the comparison with the respective numerical results. A good model should be able to not only predict the correct peak loads, but should also reproduce accurately the deformations at peak, as well as in the softening branch of the experimental curve. Furthermore, the correct failure mechanisms should be numerically reproduced.After calibration and validation of the concrete and the calibration of the bond parameters, the quality of the model can be assessed by its ability to predict the response for pull-out tests with wide support for which either concrete cone failure or mixed failure can be expected. In the model, the wide ring support of the experiments is reproduced in order to obtain the experimentally seen combined concrete-bond failure. The anchor model for the unconfined configuration simulates also part of the original slab tested experimentally. The simulated slab was 0.7 × 0.7 × 0.3 m with the same mesh properties as used for the confined anchor model and the concrete characterization models. The boundary conditions have been defined in a similar fashion as for the confined model, but the selection of the nodes used to prescribe the vertical constraint was chosen in agreement with the dimensions of the ring used for the unconfined tests. The loading rates are consistent with those of the confined model.In order to assess the capability of the model to properly estimate the bonded anchor capacity for different embedment depths, the tests have been reproduced numerically and their results compared with the experimental ones. Simulations run for the three different embedment depths show good agreement with the experimental results. ests see a.y-axis, the embedment depth  and on the x-axis the radius of the concrete cone  are plotted. In x-axis starts at 7 mm, which is the radius of the borehole, and ends at 200 mm, which is the radius of the supporting ring. The y-axis starts from zero, which is the concrete surface, and ends at A photogrammetric tool was used to obtain a virtual three-dimensional representation of the conical void left in the concrete slab after the anchors have been pulled-out. The aim is to compare the real concrete cone shape to the concrete cone shape of the numerical simulation in an attempt to validate the failure mechanism of the numerical model. A series of pictures of the conical void needs to be taken from different positions and different distances from the area of interest after a number of targets are placed around it. The positions of the targets are identified in all of the pictures, defining a common coordinate system, according to which the position and direction of the cameras for every picture taken are determined. Once the relative positions of targets and cameras are obtained, the surface of the considered object can be determined based on image correlation yielding a point cloud that represents the concrete cone surface, which can be compared with the cone shapes obtained from numerical simulations. The point cloud coordinate system is transformed from Cartesian to polar coordinates in order to be able to create a 2D diagram see a. On theDepending on embedment depth and bond strength, the failure can range from complete concrete cone, to combined concrete cone-bond failure, to bond failure. For the combined failure, as can be seen in Different parameters influence a model differently; some of them can be critical, and some can be negligible. This concept applies also for experiments. A good understanding of the sensitivity between inputs and outputs allows a more accurate and efficient design of experiments or numerical campaigns. For this reason, a sensitivity study is performed on the numerical model varying the main meso-scale parameters.During calibration, the elastic modulus and those meso-scale parameters that directly govern the concrete failure in tension and shear were inversely identified based on simulated tests that are sensitive to those parameters, i.e., cylinder compression, cube compression and notched three-point bending. The other LDPM parameters are related to mechanisms that were not investigated in this experimental campaign, such as the triaxial behavior. Consequently, suggested parameters for similar concretes were taken from the original LDPM validation paper , and nonA two-step approach had to be followed for the study. In the first one, the relation between the LDPM meso-scale parameters and the macroscopic concrete properties are investigated. In the second one, the relation between the macroscopic concrete properties and the macroscopic system response are studied. Here, only the second part will be discussed, as illustrated in Generally, in As previously stated, more than one concrete cone is forming during the pull-out test, and all of them contribute to the system capacity. Concrete is a heterogeneous composite material. For normal to high strength concretes cracks mostly propagate along the aggregate interfaces and through the cement paste. The formulation of LDPM mimics this behavior and allows, together with the random placement of simulated aggregates following the actual sieve curve, to predict realistically the cone shapes. Tests on bonded anchors with various configurations have been performed along with a complete concrete characterization at the same concrete age. All specimens have been cast from the same batch. The tests have been used to calibrate concrete and slip-law parameters of a numerical model able to fit a designated sub-set of the available experiments. Using the same parameter set, the pull-out load, crack patterns and failure mechanisms of the unused control group have been predicted accurately. The simulated cone shapes are validated by photogrammetric measurements. Overall, the model shows a good predictive capability both in terms of anchor capacity, deformation behavior and failure mechanisms. The application of the numerical model provided novel insights into the failure mechanisms of the bonded anchor, namely the existence of multiple cones and the fact that the peak load is not correlated to the depth of the partial cone, which localizes in the case of mixed mode failure.


A full-scale experimental program was used in this study to investigate the structural behavior of novel insulated concrete sandwich wall panels (SWPs) reinforced with grid-type glass-fiber-reinforced polymer (GFRP) shear connectors. Two kinds of insulation-expanded polystyrene (EPS) and extruded polystyrene (XPS) with 100 mm thickness were incased between the two concrete wythes to meet the increasing demand for the insulation performance of building envelope. One to four GFRP shear grids were used to examine the degree of composite action of the two concrete wythes. Ten specimens of SWPs were tested under displacement control subjected to four-point concentrated loads. The test results showed that the SWPs reinforced with GFRP grids as shear connectors developed a high degree of composite action resulting in high flexural strength. The specimens with EPS foam exhibited an enhanced load-displacement behavior compared with the specimens with XPS because of the relatively stronger bond between insulation and concrete. In addition, the ultimate strength of the test results was compared to the analytical prediction with the mechanical properties of only GRFP grids. The specimens with EPS insulation presented higher strength-based composite action than the ones with XPS insulation. Insulated concrete sandwich wall panels (SWPs) generally consist of the inner/outer concrete wythes and the insulation between the concrete wythes. Various types of insulated concrete SWP systems have been developed to increase both the thermal and structural efficiency. In line with the increasingly growing demand for energy-efficient buildings throughout the world, insulated concrete SWP systems have been drawing more attention. These systems have been applied to various building structures, such as residential and office buildings, cold storages, and industrial buildings. They have been more commonly used for the exterior wall, but they have also been used for the interior wall. There are various insulation materials, including fiberglass, rock wool, and polystyrene. The extruded polystyrene (XPS) and expanded polystyrene (EPS) foams are most commonly used for the insulated concrete SWP systems because they have high thermal performance and workability. Their energy-saving effects are higher than those of fiberglass under the same environmental conditions . MoreoveInsulated concrete SWPs are categorized into a non-composite wall panel in which the inner/outer concrete wythes behave independently, a composite wall panel where an integrated wall panel behaves as a single member, and a partial composite wall panel depending on the degree of composite action. The inner and outer concrete wythes of the insulated concrete SWP are interlinked with various shear connectors, which are made from concrete, steel or fiber-reinforced plastic (FRP), including carbon, glass, and aramid fiber composites.The difference in composite action among the insulated concrete SWPs depends on the degree of shear flow capacity, which is determined by the shear connector’s material and the adhesive bond between the insulation and the concrete wythes. Pessiki and MIynarczyk  evaluateet al. [et al. [et al. [Unlike the previous studies that employed metal or concrete shear connectors, Salmon et al.  introduc [et al.  performe [et al. , the fle [et al. . Accordi [et al.  evaluate [et al. ,14,15, t [et al. , the stuIn this research, a novel insulated concrete SWP system, as seen in A shear connector for insulated concrete SWPs should play the role of enhancing the composite action and reducing the energy loss by thermal bridge. In the construction industry, where traditional concrete and steel have dominated for the last 160 years, FRP has been attracting attention mainly because of its relatively higher tensile strength compared to the traditional steel material, and its low conductivity, light weight, and anticorrosive advantage. As a shear connector for an insulated concrete SWP system, the weight of FRP is only one fourth that of steel thanks to the former’s low specific gravity (1.4–2.0) while its tensile strength is 2 to 10 times that of steel, as seen in The GFRP grid shear connector consists of vertical and horizontal strands, as seen in 1 and S2. S1 is the spacing distance between the GFRP shear grids, and S2 is the distance between the GFRP shear grids and the edges of the specimens. The values of S1 and S2 are presented in As seen in The specimen was set in the four-point loading condition, as seen in full is the experimental maximum load with full-composite action, Pnon is the experimental maximum load with non-composite action, and Pe is the experimental maximum load of the test specimen. As indicated in As seen in For all the XPS and EPS specimens, except for EPS4, the GFRP shear grids ruptured at the maximum load, and then the loading capacities rapidly dropped. At this maximum load, the composite behavior of the two concrete wythes were converted to independent (non-composite) behavior of each concrete wythe because the shear grids were ruptured. It was concluded that the maximum loads were governed mainly by the GFRP capacity. In addition, the concrete compressive strength could be an important factor influencing the pullout strength of the GFRP shear grids. In the preliminary test, pullout of the GFRP shear grids did not occur when the anchorage length of the GFRP shear grids was more than 20 mm, with f’c = 35 MPa or less. It was ensured that the anchorage length of the GFRP grids in this test was about 25 mm, and thus, no pullout failure occurred during the test. Therefore, as the concrete compressive strength was high enough to prevent the pullout failure of GFRP, the concrete compressive strength did not significantly affect the maximum load, which was governed by the capacity of the GFRP shear connectors.The load-deflection behaviors of the XPS and EPS specimens, where one GFRP grid on each shear span was used, are compared in The deformability of each specimen was calculated by subtracting the deflection at the crack initiation from the deflection at the ultimate state. The bracketed values present the extended deformability, which includes the ductile deformation until before the load capacity dropped abruptly due to the GFRP grid rupture.P and V are the maximum load and the maximum shear force in the four-point bending system. I and Q are the moment of inertia and the first moment of area at the interface between the insulation and the concrete, assuming full-composite action. NoGS is defined as the number of active strands per unit meter grid, which was determined to be 13 for the shear grids used in this experimental program. The active strands refer to the strands whose two ends are embedded in the inner/outer concrete wythes, as seen in I and Q were computed as 5,760,000 mm3 and 964,800,000 mm4, respectively. In the case of an SWP system reinforced with a shear grid per shear span, the SWP system is expected to resist a 19.4 kN load, and the expected maximum load for the four shear grids per shear span was computed as 77.6. To ensure the GFRP grid failure before flexural failure, a 7 mm-diameter wire mesh was selected because the specimen with the 7 mm-diameter wire mesh provided a more than 80 kN loading capacity. As only the shear connector is considered, without adhesion of the concrete and insulation, the expected load may be a lower limit (low bound). The expected maximum load increases linearly, as shown in The flexural capacity of the insulated concrete SWP with shear grids can be predicted using the shear flow strength of the GFRP shear grids in Equation (2).The shear flow capacities of the XPS specimens were improved by about 15 kN/m from the analytical prediction considering only the shear grids. This was approximately 20% of the shear flow strength of the unit grid. On the other hand, in the group of EPS specimens, the shear flow strength measured in the experimental test was much larger than that predicted analytically. As the adhesion characteristics seemed to govern the load capacity rather than the number of grids, it was very complex to quantify the insulation effects on the analytical prediction. It was noted that the shear flow strength for the EPS4 specimen might be underestimated because the EPS4 specimen exhibited the steel wire mesh fracture before the entire rupture of the GFRP shear grids. For further study, strength enhancement according to the type of insulation should be taken into account in the analytical prediction of the flexural strength.The purpose of this study was to develop a novel insulated concrete SWP system using GFRP grid shear connectors. A full-scale experimental program was performed to verify the structural performance of the insulated concrete SWPs. In addition, the analytical prediction was compared to the experiment results. Basically, the SWPs reinforced with GFRP grids as shear connectors hold an enhanced flexural capacity by developing a high degree of composite action. The other test results and findings from this study are outlined as follows.The degree of composite action and the flexural strength of the specimens with extruded polystyrene (XPS) insulation were increased in proportion to the number of GFRP grids, but the contribution of the adhesion between the concrete and the insulation was minor because of the smooth surface of the XPS foam. As for the specimens with expanded polystyrene (EPS) insulation, the in-plane shear strength was mainly dependent on the adhesion between the concrete and the insulation, and thus, the flexural strength was little affected by the number of shear grids. The maximum flexural strength was mostly dependent on the in-plane shear resistance provided by the bond between the insulation and the concrete, and a full-composite behavior was achieved when four or more GFRP grids were used in this experimental program.The strength-based degree of composite action in the insulated concrete SWP system was significantly influenced by the type of insulation, which had different adhesion properties to the concrete surface. The in-plane shear strength of the insulated concrete SWPs with EPS foam was much higher than that of the specimen with XPS foam because of the high bond capacity of EPS foam to concrete panels. Accordingly, it is a very good option to improve the interface adhesion between concrete and insulation when applying XPS foam to insulated concrete SWP systems.


Mesenchymal–epithelial transition factor also named c-MET is a receptor tyrosine kinase for the hepatocyte growth factor that plays a pivotal role in tumorigenesis. c-MET-targeted therapies have been tested in preclinical models and patients, with significant benefits for cancer treatment. In recent years, many studies have shown that the expression level and activation status of c-MET are closely correlated to c-MET-targeted therapy response and clinical prognosis, thus highlighting the importance of evaluating the c-MET status during and prior to targeted therapy. Molecular imaging allows the monitoring of abnormal alterations of c-MET in real time and in vivo.In this review, we initially summarize the recent advances in c-MET-targeted molecular imaging, with a special focus on the development of imaging agents ranging in size from monoclonal antibody to small molecule. The aim of this review is to report the preclinical results and clinical application of all molecular imaging studies completed until now for in vivo detection of c-MET in cancer, in order to be beneficial to development of molecular probe and the combination of molecular imaging technologies for in vivo evaluation of c-MET. Various molecular probe targeted to c-MET possesses distinctive advantages and disadvantages. For example, antibody-based probes have high binding affinity but with long metabolic cycle as well as remarkable immunogenicity.Although studies for c-MET-targeted molecular imaging have made many important advances, most of imaging agents specifically target to extracellular area of c-MET receptor; however, it is difficult to reflect entirely activation of c-MET. Therefore, small molecule probes based on tyrosine kinase inhibitors, which could target to intracellular area of c-MET without any immunogenicity, should be paid more attention. Mesenchymal–epithelial transition factor (c-MET) is a receptor tyrosine kinase (RTK) naturally activated by the binding of hepatocyte growth factor (HGF), and then regulates many essential cellular processes including cell proliferation, motility, invasion, angiogenesis, and apoptosis. The c-MET oncogene is located on chromosome 7q21-31 and was initially identified in an immortalized osteosarcoma cell line by Cooper et al. in the1980s [The mature form of the c-MET receptor is a disulfide-linked heterodimer consisting of a 50-kDa extracellular α-chain and a transmembrane 140-kDa β-chain. Both the α chain and the first 212 residues of the β chain constitute the Sema domain, which has an HGF-binding site in the extracellular region .2-terminal portion of the HGF α chain contains the high affinity c-MET binding domain, and the β chain is responsible for activating c-MET receptor via a direct interaction.HGF , 5, alsoAfter HGF-binding, the c-MET receptor undergoes homodimerization and phosphorylation at tyrosines 1234 and 1235 and subsequently at tyrosines 1349 and 1356 in the carboxy-terminal tail , SHC  is currently the standard diagnostic procedure, these methods require repeated biopsies that can be painful for the patient. Thus, the development of more effective noninvasive detection methods for accessing c-MET expression and activation is needed.Molecular imaging is a noninvasive method that can provide accurate information in vivo and in real time, and its application for detecting c-MET activation could represent a breakthrough in cancer diagnosis. Various c-MET-targeted tracers have been developed based on multiple molecular modalities, such as antibody, peptide, small protein, genetically encoded protein, and small molecule tyrosine kinase inhibitor (TKI). These tracers also have been further evaluated in preclinical studies or clinical setting. Recent studies acquired significant progress toward the development of molecular imaging probes for monitoring c-MET activation, but the imaging performance of these probes remains a critical issue. Here, we review and discuss these studies Fig. , Table 1It is well established that HGF can alter the hemodynamics and metabolism of normal and malignant c-MET-expressing tissues , 38, and64Cu-NOTA-rh-HGF (recombinant human hepatocyte growth factor) and evaluated its potential as a PET imaging radiotracer for c-MET-targeted molecular imaging [64Cu-NOTA-rh-HGF was accomplished by conjugating concentrated rh-HGF to p-SCN-Bn-NOTA and subsequently chelating with 64Cu. Flow cytometry examination in U87-MG (human glioblastoma) and MDA-MB-231(human breast cancer) cell lines, which have moderate level and low level expression of c-MET, respectively, confirmed the specific binding capacity of rh-HGF to c-MET. In vivo studies further revealed that tumor uptake of 64Cu-NOTA-rh-HGF was rapidly and clearly visible at 0.5 h post-injection (p.i.) and peaked at 9 h p.i. (6.7 ± 1.8%ID/g) in U87-MG xenografts in mice; however, it was significantly lower in MDA-MB-231 xenografts in mice (1.8 ± 0.6%ID/g at 9 h p.i.), with consistency between PET images and biodistribution data in both models  . Therefore, the smaller 64Cu-NOTA-rh-HGF displayed a faster circulation clearance than radiolabeled intact mAbs, which also obtained a higher optimal tumor/muscle ratio (13.5 ± 6.1 at 9 h p.i. in U87-MG xenografts) in less than a half-life period.More recently, in 2015, Luo et al. reported the synthesis of  imaging . The synThese studies demonstrate that imaging agents based on the endogenous HGF ligand could be a straightforward and effective approach to image c-MET. However, while HGF displays good pharmacokinetic properties and high selectivity to c-MET, it also presents significant disadvantages. For instance, endogenous ligands will inevitably induce biological effects such as increased cell proliferation and enhanced cell survival and could also stimulate tumor growth. In addition, the endogenous ligand will theoretically preclude the preferential uptake of the radiolabeled ligand versus the unlabeled ligand in animal tumor models and therefore reduce contrast ratio of the tumor PET or SPECT images . These lIn the past two decades, several monoclonal antibodies (mAbs) against the HGF/c-MET signaling pathway including rilotumumab, ficlatuzumab, DN30, and onartuzumab, among others, have been extensively studied in preclinical and clinical trials, with promising outcomes in cancer treatment. Consequently, antibodies have also become of interest in the search for viable imaging agents for c-MET-targeted molecular imaging.125I-mAb) consisted of anti-c-MET mAb and anti-HGF mAb. So they can target tumor cells directly and indirectly by binding to c-MET and HGF, respectively. The 125I-mAb mixture was synthesized with a radiolabeling efficiency of >60 and >85%, and the radioactivity was detected by whole body gamma camera imaging as early as 1 h p.i. in SK-LMS-1 (human leiomyosarcoma with high expression of c-MET) and S-114 (NIH 3T3 cells transformed with human HGF and human c-MET) murine models, whereas initial visualization of tumors in M-114 and DA3 murine models were at 1 day p.i. . Quantitative ROI (region of interest) analyses indicated that tumors with autocrine for human HGF and c-MET demonstrated more rapid uptake and clearance of the 125I-mAb mixture than tumors expressing one or both murine homologues, reaching a mean value of tumor-to-whole body activity ratio by >0.3 at 1 day p.i. Generally, mice bearing “human” tumors (SK-LMS-1 and S-114) display a faster uptake and a faster metabolism of tracer from body than mice bearing “murine” tumors , as shown in images (lower levels of splanchnic activity at 3 and 5 days p.i. and more conspicuous thyroid activity derived from uptake of free radioiodide released by mAb deiodination). This study did not however include a HGF/c-MET negative control group. In a follow-up study, Hay et al. compared two anti-c-MET mAbs, Met3 and Met5, for nuclear imaging of human and canine c-MET-expressing tumor xenografts in nude mice [125I by the same procedure described previously, with a radiolabeling efficiency of >60 and >90% [125I-Met3 exhibited the highest uptake value at the earliest imaging time point  and declined over time, similarly to previous research [125I-Met5-injected xenografts in mice models exhibited the highest uptake value at 1 day p.i., with respectively 13.3 ± 7.6%EIA (percentage of estimated injected activity) in SK-LMS-1/HGF, 7.5 ± 3.4%EIA in PC-3, and remained high until the final imaging point (5–6 days after injection). Although quantitative analysis indicated faster tumor uptake for 125I-Met3, 125I-Met5 obtained higher and more durable tumor uptake (at least 5 days). Therefore, Met5 might be more useful for radioimmunotherapy. Inevitably, distinct thyroid activity was observed since 1 day p.i. caused by deiodination from tracers. For 125I-LF7, a negative control mAb, the tumor uptake was <3% EIA at any time point. Ex vivo tissue uptake measurements were however not performed in this study.Preliminary work by Hay et al. tested a mAbs-based radiotracer mixture for molecular imaging of c-MET . The radude mice . Met5 anand >90% . In qualresearch . However125I-hFab-Met-1, it was highly accumulated at 5–8 h p.i. and persisted for at least 24 h in SK-LMS-1/HGF bearing mice models, with a mean tumor activity of about 6% of the estimated activity administrated. Particularly high accumulation of activity was detected in the thyroid region. Although possessing smaller molecular weight and therefore faster metabolism as well as tumor uptake than the whole antibody, the Fab single fragment has a lower binding affinity than the whole antibody, as we have seen for 125I-hFab-Met-1, obtained highest tumor uptake of 6%EIA which is lower than 125I-Met5 (~13%EIA).To reduce the effects of c-MET activation induced by mAbs or native ligands on c-MET expression in vivo, Jiao et al. assessed the feasibility of using a monovalent anti-c-MET antigen-binding fragment  as a molecular probe for targeted imaging of c-MET . hFab-Me125I was accomplished by direct electrophilic radioiodination, as described in a previous study [125I-MET4 were qualitatively and quantitatively comparable to the best images published previously [In 2009, Knudsen et al.  developeus study . Nucleareviously –45. More89Zr (t1/2 = 78.4 h) and 124I (t1/2 = 100.3 h). Perk et al. initially reported the radiolabeling of DN30, a mAb reactive to c-MET labeled with 89Zr for assessing c-MET expression status in vivo by PET imaging [89Zr into DN30 was accomplished through a bi-functional metal chelating moiety conjugated to the mAb (N-sucDf-DN30). The radiolabeling achieved moderate yields of >70%, radiochemical purity of >95%, and specific radioactivities ranging from 54 to 70 MBq/mg. In biodistribution studies of xenografts in mice models, the uptake of 89Zr-N-sucDf-DN30 (89Zr-DN30) in FaDu (human head-and-neck cancer with low c-MET expression) tumors was significantly lower than that in GTL-16 (human gastric cancer with high c-MET expression) tumors, specifically, at 3 days p.i. 7.8 ± 1.2%ID/g was detected in FaDu tumors and 18.1 ± 4.5%ID/g in GTL-16 tumors. Consistent with these results, the radioactivity was more pronounced in the GTL-16 tumors when compared to FaDu tumors, and it is noteworthy that GTL-16 tumors as small as 11 mg were clearly visualized. Although sensitive for detection of small tumors, 89Zr-DN30 displayed relatively high uptake in the liver and spleen, partly due to residualization of 89Zr after catabolism of the conjugate in these organs. In summary, the DN30 monoclonal antibody accurately measures c-MET expression, as confirmed by IHC, and can be used for molecular imaging in vivo.It is widely accepted that compounds labeled with positron-emitting radionuclides for PET imaging can produce images with higher resolution and which allow a more accurate quantitative analysis , 49. Cur imaging . The inc76Br or 89Zr and tested as a targeted molecular imaging agent in c-MET expressing cell lines and xenografts in mice models by Jagoda et al. in 2012 [89Zr-desferrioxamine (df)-onartuzumab was synthesized using a df-conjugate, with yields of >90% and specific radioactivities ranging from 0.037 to 0.185 MBq/μg. 76Br-onartuzumab was radiolabeled directly, with low yields of >45% and specific radioactivities of 0.118 ± 0.067 MBq/μg with high specific binding affinity for c-MET. In biodistribution studies, uptake in MKN-45 (human gastric carcinoma with high c-MET expression) tumors of 76Br-onartuzumab was about 2-fold higher than in U87-MG tumors (moderate level c-MET expression). However for 89Zr- df-onartuzumab, the uptake in the U87-MG tumors was 3-fold lower than that in the MKN-45 tumors at 5 days p.i., consistent with c-MET expression. Both 76Br-onartuzumab and 89Zr-df-onartuzumab had a similar uptake in non-target tissues in all tumor models. In blocking studies for MKN-45 xenografts, tumor uptake of 89Zr- df-onartuzumab decreased approximately 3.8-fold by plus of 10 nmol of unlabeled onartuzumab, suggesting that competitive blocking by unlabeled onartuzumab occurred in the tumor. In summary, 76Br-onartuzumab showed lower retention in the tumors when compared to 89Zr-df-onartuzumab, with clearance similar to the radioactivity in blood. For micro-PET imaging in MKN-45 xenografts, tumors injected with 76Br-onartuzumab could be detected as early as 18 h p.i., with optimal visualization at 24 h p.i. However, although tumors injected with 89Zr-df-onartuzumab could also be visualized at 18 h p.i., the image quality continued to improve over the 5-day period. 89Zr-df-onartuzumab accumulation in the normal tissues—blood, heart, lungs, gastrointestinal tract, and muscle—decreased slowly, with reduction of <50% from 18 h to 5 days, and in contrast, liver and kidney uptake increased over time, indicating hepatobiliary and renal clearance for 89Zr-df-onartuzumab. In addition, high bone uptake (up to 7%ID/g) at 5 days p.i. was observed, due to free 89Zr from the chelated tracer.Onartuzumab, an experimental therapeutic 1-armed monoclonal antibody, was radiolabeled with  in 2012 . 89Zr-de89Zr for immuno-PET studies in xenografts in mice models expressing c-MET [89Zr-labeled H2 cys-diabody (89Zr-DFO-H2 cys-diabody) was site-specifically conjugated with maleimide-DFO, and prepared with labeling efficiency of 49%, radiochemical purity of 95%, and specific activity of 0.13 MBq/μg. The 89Zr-DFO-H2 cys-diabody showed a specific uptake in Hcc827-GR6 tumors  with high c-MET expression) that was higher than the uptake in Hcc827 (human NSCLC with low c-MET expression) tumors in PET scans at both 4 and 20 h p.i.; high-contrast images were obtained as early as 4 h p.i. In ex vivo biodistribution assays, at 4 h after injection, Hcc827-GR6 tumors had higher uptake levels at 1.8 ± 0.2%ID/g when compared to the negative control Hcc827 tumors at 0.65 ± 0.15%ID/g. High kidney uptakes observed in both biodistribution and PET images were induced by clearance of these low molecular weight cys-diabody proteins. The specificity of anti-c-MET targeting by the H2 minibody (antibody fragment reformatted from H2 but with larger molecular weight) was also assessed in immuno-PET studies. Biodistribution analyses revealed higher specific uptake levels in Hcc827-GR6 tumors than other groups. However, the image contrast was not improved due to higher background signal in the blood (Hcc827-GR6 tumor: blood = 4.2 ± 0.5) resulting from the longer persistence of the minibody in the serum. Overall, the H2 cys-diabody is the preferred choice for rapid immuno-PET applications because it has the unique advantage of cross-reacting with mouse c-MET, thus allowing more representative imaging studies in the presence of endogenous c-MET expression in normal mouse tissues.In 2014, Li et al. radiolabeled fully human single-chain variable fragments-cys-diabodies  with ng c-MET . The 89Z89Zr could precisely detect c-MET expression in vitro and in vivo in mice tumor model, and may prove to be an effective immuno-PET agent in humans.According to results of above studies, monoclonal antibodies or scFv specific to c-MET radiolabeled with the long half-life period positron-emitting radionuclide In addition to antibody-based radiotracers, antibody-based fluorescent tracers have also been used for c-MET-targeted molecular imaging in vivo to assess c-MET expression levels. In 2010, Lu et al. synthesized QD (quantum dot)-labeled anti-c-MET scFv (designated Ms20-QD) and tested its efficacy as an imaging agent in c-MET-expressing tumors . The Ms2Towner and his group made important breakthroughs in the domain of c-MET-targeted MRI, which offers better reproducibility without any radiation damage. In 2008, the team successfully visualized overexpressed c-MET in C6 (rat glioma) rat models in vivo by MRI based on a targeting contrast agent, anti-c-MET-Gd-DTPA-albumin, an anti-c-MET antibody linked to biotinylated Gd-DTPA-albumin . T2-weigl-amino acid (CDAA)-defined rat hepatocarcinogenesis model and, for the first time, the expression of c-MET was visualized in vivo. A decrease in T2-weighted MRI signal, as well as changes in T2 values, were detected within selected regions of the tumor (expressing high c-MET), while two negative control groups including choline-sufficient l-amino acid (CSAA)-defined rats  administered with the SPIO-anti-c-MET or with SPIO alone (without anti-c-MET antibody) showed no substantial changes in both T2 values or MRI signal intensities.In another study , Towner In 2010, Towner and colleagues reported another novel MRI molecular imaging probe for the in vivo detection of c-MET overexpression in C6 rat glioma models . This prBased on data from above studies, Towner et al. initially developed these MRI contrast agents targeted to c-MET, and further illustrated that these anti-c-MET antibody-based targeting agents were feasible for detection of c-MET overexpression in tumor in vivo with MRI by changes in signal intensity. Despite this very valuable preclinical attempt to visualize c-MET using MRI, some limitations need to be considered such as nephrogenic systemic fibrosis (NSF) associated with MRI contrast agent Gd, immunogenicity from intact antibody . On the Compared to antibody-based c-MET-targeted molecular imaging, with inherent long clearance half-life after injection and potential immunogenicity, smaller peptide-based molecular imaging agents, due to their low molecular weight, present some advantages such as favorable pharmacokinetic and tissue distribution patterns, higher permeability, lower toxicity, less immunogenicity, and easy accessibility for chemical modification . In rece125I as a diagnostic tracer in vivo in xenografts in mice models of human leiomyosarcoma derived from the cell line SK-LMS-1/HGF, which expresses c-MET/HGF. Tumor-associated radioactivity was detected by nuclear imaging as early as 1 h after injection of the tracer and remained visible up to 24 h p.i. Quantitative ROI analyses showed that tumor activity accounted for 4 to 5% of the estimated injected activity at 1 and 4 h p.i. but declined to 3% at 7 h p.i. However, tumor-associated radioactivity detected after injection of a control 125I-labeled non-avid peptide was significantly lower at all time points. These results demonstrated that Met-pep1 was specific to c-MET and might be a potential diagnostic agent for clinical applications. Activity was highest in the liver at all imaging time points, suggesting that the liver is major metabolic pathway for the tracer. Nevertheless, activity was also evident in the bladder at 4 and 7 h post-injection, whereas thyroid activity derived from deiodination of the tracer increased over time.In 2007, Zhao et al. searched for a cMBP from a random peptide phage display library using a subtractive planning approach on intact cells , and per125I directly, with a radiochemical purity of >90% [125I-cMBP had low tumor-to-blood ratios (tumor/blood = 1.89 at 4 h p.i.), but a GGG  or an AOC  were introduced as a linker to the structure of radiotracer enhance the tumor–cell binding affinity. Blocking assays showed that the specific binding to U87-MG cells was significantly blocked by unlabeled cMBP, cMBP-GGG, and cMBP-AOC, respectively, but not by the mismatched peptide. According to the biodistribution data, 125I-cMBP-GGG exhibited the highest tumor-to-blood ratios and tumor uptake over time. Consistent with these data, SPECT images of U87-MG xenografts were clearer in mice injected with 125I-cMBP-GGG. Unexpectedly, both cMBP-GGG and cMBP-AOC showed uniform high pancreatic uptake, which may be a result of peptide degradation, as there was very low c-MET expression in the pancreas compared to tumor tissue, as confirmed by RT-PCR. In addition, introduction of the linker did not affect specificity of the probe to c-MET, whereas a lower pancreatic uptake was observed. 125I-cMBP-GGG and 125I-cMBP-AOC could be cleared from body at 15 h p.i. mainly by renal metabolism. In the same year, based on the same peptide, Kim’s group reported two other c-MET-targeted probes labeled with cyanine dye 5.5 (Cy5.5), Cy5.5-cMBP-GGG, and Cy5.5-cMBP-AOC for optical imaging in athymic mice bearing U87-MG or Ramos (c-MET negative human B-lymphoma) xenografts [125I-radiolabeled cMBP-GGG showed higher tumor uptake than cMBP-AOC [125I-radiolabeled cMBPs showed high pancreatic uptake, Cy5.5 conjugates were instead rapidly eliminated via the renal metabolic pathway. These differences in retention might be related to the size or properties of Cy5.5, for instance, lower pancreatic uptake could be caused by Cy5.5 hydrolysis. In conclusion, Kim et al. tested this cMBP radiolabeled with 125I or conjugated to Cy5.5 as a tracer with a different linker for visualization of c-MET. Results from these cMBP-based nuclear and optical images are in concordance, demonstrating that the cMBP-based tracer could accurately detect c-MET overexpression.In 2009, Kim et al. reported a new cMBP identified on a peptide phage display system and then radiolabeled with  of >90% . As the nografts . The Cy5cMBP-AOC ; howeverKd = 2 nM) to a linker (GGGK) and subsequently to a modified Cy5 . Intravenous administration of GE-137 in mice bearing HT29 tumors  resulted in specific accumulation of the probe in c-MET expressing tumors, whereas Cy5**-labeled scrambled peptide as a control group was only visible in the kidneys. GE-137 has a dose-linear renal clearance, and the clearance rate was about 0.13 l/kg/h, and is comparable between dose groups. Plasma concentrations were 0.12–0.16 mg/L at 3 h after administration of 0.13 mg/kg. In addition, co-administration of GE-137 with an excess of unlabeled peptides significantly reduced tumor uptake. After being validated as safe and well tolerated in healthy volunteers, GE-137 was tested in cancer patients. GE-137 visualized by fluorescence colonoscopy could detect not only all neoplastic polyps that were visible with white light but also additional polyps with c-MET expression, as verified by immunohistochemical analyses. This landmark first-in-human pilot study conducted by Burggraaf et al. showed that molecular imaging using an intravenous fluorescent c-ME- targeted agent is a feasible and safe method for clinical applications.More recently, Burggraaf et al. reported a novel optically labeled c-MET-targeted molecular imaging probe, designated GE-137, which has been assessed in a preclinical study as well as in healthy volunteers . GE-137 Liu et al.  showed u18F, 99mTc) to detect expression of c-MET.In summary, the novel fluorescent tracer based on c-MET-targeted peptide (GE-137) has successfully visualized expression of c-MET in preclinical study and was further used to detect colorectal carcinoma overexpressing c-MET in clinical setting. Furthermore, the peptide targeted against c-MET was also labeled with radionuclides  by ex vivo analyses and PET imaging, Arulappu and colleagues demonstrated that 18F-AH113804-based PET imaging could detect loco-regional recurrences after surgical excision of orthotopically implanted HCC1954 human basal-like breast cancer with high c-MET expression in mice models as early as 6 days postoperatively, while with CT scanning, the recurrences could only be visualized after at least 20 days. These results showed that 18F-AH113804-based PET imaging has great potential as a clinical screening tool for earlier loco-regional recurrences of human basal-like breast cancer. Due to smaller molecular weight (~3.2 kDa), 18 F-AH113804 not only permitted early imaging after tracer administration (1 h p.i.) but also cleared fast from plasma and non-target tissues , allowing for high-contrast imaging after injection, and improving the sensitivity for tumor detection.Based on these studies, in 2016, Arulappu et al. developed a radiolabeled analogue of GE-137, GBq/μmol . After v99mTc, or with tetra SO3 for labeling with cy5** (653/675 nm). 99mTc-cMBP was synthesized with radiochemical purity of >90% and specific activity of 430 Ci/mmol, and with high affinity binding (nM) to c-MET observed in vitro in MKN-45 (high c-MET expression). In biodistribution assays of MKN-45 xenografts in mice models, higher uptake of 99mTc-cMBP was detected in MKN-45 xenografts than all organs except for the kidney. Blocking studies showed that tumor uptake decreased by 62% after coinjection of 99mTc-cMBP with 24 nmol of unlabelled cMBP. In initial microSPECT imaging studies, the tumor could be visualized as early as 30 min p.i. and clearly at 60 min p.i., and the images remained relatively constant until 120 min p.i. but then the signal significantly decreased. Measurements of tumor vs background signal indicated that the optimal imaging time for 99mTc-cMBP was 90 min p.i., and this time point was therefore adopted in subsequent longitudinal imaging studies for assessing the ability of 99mTc-cMBP to monitor targeted therapy in MKN-45 xenografts with c-MET TKI PHA665752. 99mTc-cMBP tumor uptake in the treated group, when compared to the vehicle group, was decreased by 43, 42, and 25% at days 8, 14, and 21, respectively. Notably, these results were comparable to cy5**-cMBP fluorescence imaging using the same treatment models with an optimal dose of 1 nmol and optimal imaging time of 60 min p.i.., and this was validated by histologic and immunohistochemical analyses. 99mTc-cMBP and cy5**-cMBP imaging may therefore have clinical applications in diagnostic and therapeutic monitoring in the future.Remarkably, Jagoda and colleagues not only conducted leading work in the development of antibody-based c-MET-targeted molecular imaging but they also performed extensive research on molecular imaging based on cMBP , 68. TheThe strategies that whole body optical  imaging based on genetically encoded proteins have been critically evaluated as a feasible molecular imaging modality in cells and transgenic animals, enabling noninvasive, longitudinal studies of dynamic biological processes in vivo , 70.In 2011, a study by Zhang et al. reported a novel method for c-MET-targeted molecular imaging and therapy monitoring based on gene transfected mice models . PlasmidIn 2006, another method for c-MET-targeted molecular imaging based on genetic engineering was developed . In this89Zr-PRS-110 with a specific activity of 100 MBq/mg and radiochemical purity of >95% and assessed its specific uptake in different human tumor xenograft models. Ex vivo assays showed that increasing doses of unlabeled PRS-110 led to tumor saturation and to specific blockade of 89Zr-PRS-110 uptake. PET imaging performed in H441 bearing mice (human NSCLC with high c-MET expression) with a suitable concentration of the tracer revealed that tumor uptake peaked at 48 h p.i. , in line with the ex vivo biodistribution data (5.9 vs. 3.9%ID/g). In A2780 bearing mice (human ovarian cancer with negative c-MET expression), both 89Zr-PRS-110 and 89Zr-Tlc-PEG were aggregated up to a similar extent (1.7 and 2.5%ID/g respectively), with lower uptake than H441 tumors. Overall, there was a significant correlation between ex vivo biodistribution and small-animal PET data quantification . In addition, uptake of 89Zr-PRS-110 and 89Zr-Tlc-PEG in various organs was comparable, except for the lung. Lung uptake of 89Zr-PRS-110 in mice bearing H441 tumors occurred neither in A2780 tumors with 89Zr-PRS-110 nor in any of the two xenografts with the negative control 89Zr-Tlc-PEG. The decreased uptake in the absence of c-MET and for the non-binding control demonstrates a c-MET-associated mechanism of uptake in the lung (possibly metastasis), which needs further investigation.Anticalins are a novel class of protein-based biopharmaceuticals that due to their small size (17 kDa) may have more favorable tumor uptake and penetration when compared with the much larger IgGs (150 kDa), and therefore display highly desirable attributes as molecular imaging agents. Terwisscha van Scheltinga et al. engineered PRS-110, an anticalin with monovalent specificity for c-MET (binding affinity of 0.6 nmol/L), which is site-specifically conjugated to a branched 40-kDa polyethyleneglycol (PEG) (2 · 20 kDa PEG) moiety for half-life prolongation , 74. A pAnticalin is a novel biopharmaceutical with good drug properties that may be applied extensively in the clinic, as anticalin-based molecular imaging could not only be useful for the diagnosis at the molecule level but also enable real-time monitoring of anticalin metabolic pathways  and pharmacokinetics, thus having a dual role in molecular imaging and drug development.The binding sites for the imaging tracers described above are all located on the extracellular domain of the c-MET receptor; however, the initial molecular event that leads to malignant development is the abnormal activation of the receptor’s tyrosine kinases, which are located in the intracellular domain of c-MET, and which will ultimately trigger downstream signaling pathways. Thus, molecular imaging based on small molecule probes with intracellular binding site can provide more roundly information about the c-MET activation status. Small molecule imaging probes, with their low molecular weight and size, are rapidly cleared and have higher permeability, and in particular, those based on c-MET-TKI have attractive properties, such as being non-toxic and easily accessible for clinical translation. However, to date, little progresses have been made in the development of small molecule imaging agents.11C-methyl iodide to produce 11C-SU11274 with radiochemical purity of ≥98% and a specific activity of 0.3–0.5 Ci/mmol. 11C-SU11274 has the same structure as SU11274, and therefore, its binding affinity and specificity was preserved. Then the authors tested 11C-SU11274 as a micro-PET imaging agent for c-MET expression in vivo. They showed that tumor uptake of 11C-SU11274 in c-MET-positive H1975 bearing mice (human NSCLC) was significantly higher than that in c-MET-negative H520 (human NSCLC) xenografts. Specifically, tumor uptake of 11C-SU11274 in H1975 peaked up at 80 min p.i. and was always higher than that in H520. These results not only confirmed the feasibility of using 11C-SU11274 as a PET tracer for c-MET activation but also revealed the importance of the tracer to study pharmacokinetics of SU11274.The first reported study by Wu et al. in 2010  describeThe slow progress in the development of small molecule imaging agents based on c-MET-TKI could mainly be attributed to challenges in the modification and synthesis of the probes. Indeed, the synthesis of the labeling precursor, which is modified from the small molecule c-MET-TKI, should produce a structure that is same or similar to the parent drug after labeling, in order to preserve the specificity to the target. Moreover, the labeling reaction requires a very complex and precise technique that is crucial to synthesize stable and pure imaging tracers.89Zr- df-onartuzumab have shown promise in preclinical studies, smaller structures like anticalin and peptides also demonstrated similarly desirable in vivo properties, making them compatible for radiolabeling with the more popular radionuclides 18F or 99mTc, which have shorter half-lives and have been extensively used in clinical applications.In this review, we have provided a brief historical overview of the development of c-MET-targeted imaging agents, from mAbs to small molecules. Evidently, each substrate, whether it is an endogenous ligand, antibody, peptide, or small molecule, has unique advantages and limitations. While radiolabeled mAbs such as In general, various types of molecular probe have distinctive advantages and disadvantages. For example, antibody-based probes have high binding affinity but with long metabolic cycle and immunogenicity. And small molecule probes have advantages in size, pharmacokinetics, and security, but are inadequate for delayed imaging after injection, due to fast clearance. Regarding the imaging technique, nuclear imaging  are useful for imaging whole body and deep viscera, whereas optical imaging  is mainly applied in detecting superficial organs and endoscopic procedures, due to weak penetrability of fluorescence signal.In our opinion, after clinical application of GE-137 with encouraging results for detection of malignant polyps, the field of c-MET-targeted molecular imaging will hopefully become established in the clinic with many expected research results in preclinical studies. Other strategies which might be relevant for translation into the clinic are antibody (fragment) tracers, as companion diagnostics for their parental antibody therapies . Althougc-MET-targeted molecular imaging makes it possible to visualize the abnormal alteration of c-MET expression in vivo and in real time, with the potential applications such as patient screening for c-MET-targeted therapeutics, monitoring therapeutic effects, evaluating prognosis, and analysis for resistance mechanism. Although the optimization of c-MET-targeted molecular imaging for clinical purposes still faces many challenges, the recent advances in the field, together with its potential clinical benefits, are highly encouraging for future research.


Background: The prevalence of human immunodeficiency virus (HIV)/acquired immune deficiency syndrome (AIDS) is higher among females than males in Sub-Saharan Africa. Education is associated with better health outcomes. For this and other reasons, African countries have made a concerted effort to increase youth education rates. However, in South Africa males have lower secondary education rates than females, yet females have a higher prevalence of HIV/AIDS. This study examines if a gender disparity exists in AIDS mortality rates among youth with secondary education in South Africa. Methods: This study uses descriptive statistics and life table techniques. A sample of 4386 deaths of youth with secondary education is used. Of this total sample, 987 deaths were among males and 340 were among females with secondary education. Results: This study shows that AIDS mortality is higher among females than males in South Africa. Males and females with secondary education have lower AIDS mortality than all males and females in the population, yet the rates are higher for females. Using cause-deleted life tables, the probability of youth dying from HIV/AIDS practically disappears for both males and females. Odds ratio calculations show that secondary education does not have a protective effect from AIDS mortality among male and female youth. Conclusion: Given the gendered difference in AIDS mortality among youth with secondary education, efforts to increase secondary education among males and further research into other factors exacerbating AIDS mortality among females with secondary education is needed in the country. The prevalence of human immunodeficiency virus (HIV)/acquired immune deficiency syndrome (AIDS) among youth in Sub-Saharan Africa is high. When young, economically active populations die from AIDS, production and development are hindered. In addition to affecting national economies, households are also affected by youth mortality due to AIDS. Loss of an income earner or a parent places financial and social strains on African households in economies where there is little government assistance. Efforts to increase access and availability to antiretroviral therapy (ART) across the continent have been made. In South Africa, programme and policy makers have attempted to expand treatment to all healthcare facilities and not restrict ART to a few accredited centres in order to reduce the severity of the disease  were HIV positive, that is a rate of about 10%  for 2009–2011 were analysed. Death registration takes place at the Department of Home Affairs, and these deaths are then updated on the national population register (NPR)  was less than 1% for sex, age and province of death , the code for AIDS deaths are B20–B24. From the variable ‘broad underlying cause of death’ on the DNFs, B20–B24 was used to identify AIDS deaths among the youth population.However, due to the reports of misclassification of AIDS deaths in the country, a second outcome variable was constructed which includes underlying causes of death related to AIDS: Tuberculosis (A15–A19), Candidiasis (B37), Cryptococcosis (B49), Toxoplasmosis (B58) and Pneumocytosis (B59). These related causes of death were added to the number of AIDS (B20–B24) deaths to create the variable ‘AIDS-related’. This variable is included in the cross-tabulation analysis to demonstrate the similarity in frequency distributions. However, in order to demonstrate the relationship between secondary education and AIDS mortality, AIDS specific underlying causes of death, coded as B20–B24 on DNFs, is used in the analysis of probability of dying  and oddsThe study also examined both AIDS and ‘AIDS-related’ causes of death in comparison to all other causes of death. AIDS and ‘AIDS-related’ deaths were removed and all other causes  were grouped together to form the variable ‘other death’.The main qualifying variable used in this study is secondary education. This variable was derived from the ‘highest level of education’ entry of the deceased on the DNF. Responses that the deceased’s highest level of education was Grade 12 were coded as ‘secondary education’. Education level that was unknown or missing was dropped from the analysis.The control variables in the study were age, sex and employment status. The latter variable is coded as 1 for ‘employed’ and 0 for ‘unemployed’. In combining age with employed status (1), the ‘economically active’ variable was created. This variable is the number of employed persons in each 5-year age group, starting from age 15.Both descriptive and inferential methods of data analysis have been used in this study.In addition to percentage distributions, death rates from AIDS, ‘AIDS-related’ and ‘other death’ were calculated. The general formula for the death rate from a specific cause is:This study then used standard life table techniques. The purpose of using life table techniques is to infer the survival chances of the youth population. Most commonly, life table techniques are used to measure actual life survival probabilities by taking into account the mortality experiences of a population. However, life tables have been adapted to serve different life events such as nuptiality and fertility  and the number of deaths from AIDS (ndix) in each age groups needs to be generatedThe number of deaths from all causes (nqx) and specifically that they will die from AIDS (nqix) is created using the following equations:The probability that people will die before entering the next age group from all causes (3) The number of survivors (nLx)(4) The stationary population (xT) is(5) The sum of years that people of a certain age are expected to live before they die (xe) and life expectancy if AIDS were eliminated from the population (e−xi) is(6) Life expectancy with AIDS in the population  is ranked as the 11th (2.34%) leading cause of male mortality amongst youth, in the period 2009–2011 . Male yoThe column percentage distribution of deaths by cause, age, sex and secondary education is seen in Death rates for persons with less than and secondary education (per 1000 youth) can be seen in nqx) is higher for females aged 20–24 years old and males aged 15–19 years old. The probability of dying from AIDS (nqix) for those with less than secondary education is higher for females at both 15–19 years old (0.0008 or 0.8%) and 20–24 years old (0.004 or 4.00%), than for males at both ages (0.0003 and 0.0011). The probability of dying of AIDS were eradicated from the population (nq−ix) for youth with less than secondary education, and this is same for males and females aged 15–19 years old (0.0000). However, this is higher for older females (20–24 years old) at 0.0003 or 0.3%. With secondary education, the probability of dying from AIDS (nqix) is higher for females at both ages (0.0029 or 2.9% and 0.0032 or 3.2%), than males at 1.4% and 2.7% respectively. Finally, if AIDS were eradicated from the mortality experience of youth with secondary education (nq−ix), the probability of dying is still higher among females (0.0001 and 0.0002), but lower than with AIDS in the population  and biological explanations for females having higher rates of infection than their male counterparts globally WHO, . The notFemales in this age group have a lower probability of survival, with and without AIDS as a cause of death, compared to males. These are females who are also reproductively active and therefore the competing cause of death is maternal mortality. In South Africa, maternal mortality for females is between 230 and 575 maternal deaths per 100,000 live births (Pattinson, The classification of AIDS deaths in South Africa has notably improved. Previous research found that as many as 94% of cause of death data from 1996 to 2006 was misclassified (Birnbaum, Murray, & Lozano, In conclusion, the benefit to survival if AIDS as a cause of death were eliminated is clear. Therefore efforts to reduce AIDS mortality in the country need to be strengthened. Efforts aimed at youth in particular are important, since this sub-population constitute the majority and are beneficial to South Africa’s future and sustainable development. In order to address and strengthen programmes and interventions however, the pathways through which secondary education acts as a prohibiting factor for female survival needs to be examined. Research on the specific mechanisms through which education, employment and other socioeconomic factors are associated with AIDS mortality needs to be conducted. For female youth, the quality of education and related knowledge of HIV infection and spread need to be assessed. It is possible that the education level of females is not the problem aggravating AIDS mortality, but rather the socioeconomic status of females in the country. There remains a need for continued investigation into this epidemic in order to fully understand and address the many complex ways in which AIDS continues to affect youth in all populations.


Bacterial antibiotic resistance is rapidly becoming a major world health consideration. To combat antibiotics, microorganisms employ their pre-existing defence mechanisms that existed long before man’s discovery of antibiotics. Bacteria utilise levels of protection that range from gene upregulation, mutations, adaptive resistance, and production of resistant phenotypes (persisters) to communal behaviour, as in swarming and the ultimate defence of a biofilm. A major part of all of these responses involves the use of antibiotic efflux transporters. At the single cell level, it is becoming apparent that the use of efflux pumps is the first line of defence against an antibiotic, as these pumps decrease the intracellular level of antibiotic while the cell activates the various other levels of protection. This frontline of defence involves a coordinated network of efflux transporters. In the future, inhibition of this efflux transporter network, as a target for novel antibiotic therapy, will require the isolation and then biochemical/biophysical characterisation of each pump against all known and new antibiotics. This depth of knowledge is required so that we can fully understand and tackle the mechanisms of developing antimicrobial resistance. Antimicrobial resistance (AMR) describes the ability of microbes to resist the growth inhibitory effects of antimicrobials or antibiotics. The rise of such organisms threatens many of the major advances in modern healthcare as the treatments rely on the implicit ability to allow the body to heal free from a serious infection  family, the Multidrug And Toxic compound Extrusion (MATE) family, the Major Facilitator Superfamily (MFS), the ATP-Binding Cassette (ABC) family and the Resistance-Nodulation-cell Division (RND) family Fig. . The divAll of the transporters listed above require the input of energy to move their target antibiotic out of the cell. SMR, MATE, MFS and RND families use the electrochemical gradient across the bacterial cell wall while the ABC family use the energy released from the hydrolysis of ATP. It is important to emphasise that bacteria therefore have to expend energy to remove these toxic compounds out of the cell. Another significant point is that bacteria are able to use several antibiotic efflux pathways Fig. . TherefoRalstonia metallidurans), nodulation (Mesorhizobium loti) and cell division (E. coli). These toxic elements are often present in their habitat hence the need for an efflux system  an inner oxygen- and nutrient-deprived region that contains dormant cells and (2) an aerobic outer layer that contains metabolically active cells. As such there will be a varied population of phenotypic and genotypic microorganisms that make up any mature biofilm (Stewart and Franklin Predictably, the microorganisms within biofilms combine a number of the already mentioned antimicrobial resistance strategies to protect themselves. They tend to be slow growing Lewis  with altThroughout the hundreds of millions of years of microbial existence, the exposure of microorganisms to potentially lethal chemicals such as antibiotics has, through evolution, resulted in a series of changes aimed at combating such threats. These alterations include physically moving away (Tso and Adler E. coli (Tal and Schuldiner E. coli pumps copper ions out of the periplasmic space (Delmar et al. It has been observed that, for many clinical isolates of antibiotic-resistant bacteria, there is an upregulation of efflux transporters. If we hypothesise that a transporter is central to the resistant phenotype, then deleting or disabling the transporter should result in a more sensitive antibiotic strain. However, this was not observed when one of these transporters was disabled; the level of antibiotic resistance remained almost unchanged (Yasufuku et al. Mycobacterium avium-M when treated with azithromycin (Schmalstieg et al. Helicobacter pylori eradication with metronidazole as part of triple therapy (Tsugawa et al. Taking this a step further, this network of efflux transporters is not only helping to protect against antimicrobials but is in fact the first line of defense of bacteria against a toxic chemical attack (Shuster et al. One of the standard methods of characterising drug efflux transporters is by recording minimal inhibitory concentrations in the presence and absence of the transporter in vivo. This has proved to be very successful and provided extensive information for many transporters (Edgar and Bibi


The Hepatocyte growth factor (HGF)—mesenchymal-epithelial transition (MET) pathway is deregulated in several cancers and is associated with aggressive phenotype and worse prognosis. MET, a tyrosine kinase receptor activated by HGF, plays a physiological role in embryogenesis, promoting cell growth, survival and motility. HGF–MET aberrant activation in tumorigenesis acts through various mechanisms: paracrine/autocrine HGF production, MET overexpression, MET germ-line and sporadic mutations and cross-talk with other growth factor receptors. In addition, MET activation could represent a mechanism of escape from other targeted therapies, through receptor amplification or over-stimulation by the ligand, as demonstrated in non-small cell lung cancer (NSCLC) and colorectal cancer (CRC) models with acquired resistance to epidermal growth factor receptor (EGFR) inhibitors and also in models of melanoma resistant to the BRAF inhibitor vemurafenib. As a consequence, a lot of molecules targeting MET signaling are under clinical investigation as single agent or in combination with other targeted drugs. Patient selection, based on MET expression on tumor samples , and pharmacokinetic/pharmacodynamic markers are needed. Authors review the latest data on the role of MET and the molecular mechanism underlying primary or acquired resistance to biological agents, focusing on NSCLC, CRC and melanoma. MET) gene encodes for a membrane-bound receptor tyrosine kinase (RTK) expressed predominantly by epithelial cells. The MET receptor, once activated by its physiological ligand, the hepatocyte growth factor (HGF), stimulates a complex system of intracellular signaling cascades: Src, extracellular signal-regulated kinase 1 and 2 (ERK1/2)/mitogen-activated protein kinases (MAPK), phosphoinositide 3-kinase (PI3K), protein kinase B (AKT), signal transducer/activator of transcription (STAT), nuclear-factor-κB, and mammalian target of rapamycin (mTOR) [The mesenchymal-epithelial transition factor  are the most widely developed targeted drugs in NSCLC, breast cancer and CRC treatment. Tumor responses to these drugs are reasonably higher than those obtained with conventional chemotherapy. As a consequence of this molecularly targeted therapeutic approach, the median progression free survival (PFS) of these patients has also significantly improved; however, most if not all of these patients experience disease progression due to innate or acquired resistance. The complex interactions among RTKs are one of the principal mechanisms of resistance to both anti-EGFR/HER1 monoclonal antibodies (cetuximab or panitumumab in CRC) and small inhibitors of the ATP binding pocket of the EGFR receptor (erlotinib and gefitinib in NSCLC). Recent findings evidenced a synergistic interaction between MET and other RTKs, like EGFR, vascular endothelial growth factor receptor (VEGFR) and insulin-like growth factor-1 receptor (IGF-1R), promoting cancer invasiveness and resistance to chemotherapy ,25. In vma cells  and promma cells . SimilarOvercoming the resistance to molecularly targeted agents toward personalized cancer treatment strategies is now a new interesting field of research in medical oncology.Despite the poor long-term outcome of lung cancer patients, a prolonged survival rate has been seen in some subgroups of patients in recent years. The most important reason of this slow improvement is the heterogeneity of NSCLC in terms of both histological and molecular features. Indeed comprehensive genome-wide studies have demonstrated recurrent genetic and epigenetic changes displaying oncogenic properties .The first of these changes has been represented by the discovery of EGFR activating kinase domain mutations, represented by exon 19 in-frame deletion of amino acids 746–750 or exon 21 L858R substitution in EGFR sequence, which identify a subset of patients who can greatly benefit from the treatment with EGFR tyrosine kinase inhibitors (TKIs), gefitinib and erlotinib, which are superior to standard doublet chemotherapy in terms of response rate and PFS ,30. Howede novo and acquired resistance to EGFR TKIs therapy in NSCLC include various molecular abnormalities in tumor cells: increased angiogenesis, constitutive activation of transducers located downstream to EGFR, overexpression of other tyrosine kinase receptors or secondary EGFR mutation. Among patients exhibiting acquired resistance, a secondary EGFR exon 20 mutation (T790M) occurs in about 50% of cases [Cellular mechanisms of of cases  and an aof cases . in vitro studies, conducted on the human NSCLC HCC827 cell line (harboring the activating EGFR mutation in exon 19) and made resistant to gefitinib, revealed that MET became amplified and caused resistance to TKI through an ErbB3-dependent activation of PI3K [In most MET-amplified cancers, MET signals are mediated through human epidermal growth factor receptor 3 (HER3/ErbB3). Indeed, in recent of PI3K ,34. ErbB versus erlotinib plus placebo in advanced NSCLC patients, at progression on first-line chemotherapy [ vs. 2.3 months for the placebo, HR = 0.81, p = 0.24), although not statistically significant. Unfortunately, the following phase III MARQUEE study (NCT01244191), comparing the same treatment in non-squamous NSCLC patients was early stopped because of negative results on overall survival (OS), the primary endpoint, at a planned interim analysis [versus erlotinib alone was studied in second line therapy of NSCLC patients [vs. 2.9 months; HR: 0.53; p = 0.04), while in MET IHC-negative tumors onartuzumab was detrimental. However, the following phase III study, the MetLung study (NCT01456325) in the same setting of patients did not confirm these positive data.Clinical trials have been conducted in recent years to test anti-MET agents, both TKIs and antibodies, for the treatment of NSCLC patients. In 2011 in a randomized phase II trial was evaluated the activity of the combination of Tivantinib (ARQ197), a highly selective MET TKI, with erlotinibotherapy ; resultsanalysis . Similarpatients : among 1CRC is the third leading cause of cancer related deaths worldwide ,39; manyKRAS) gene activating mutations, which prevent both anti-EGFR antibodies from working effectively [KRAS gene codons 12 and 13 were the first recognized mechanisms of primary resistance to anti-EGFR therapy and all patients are now screened for KRAS mutations prior to administration of anti-EGFR targeted therapies [Cetuximab and panitumumab are effective only in a minority of patients with metastatic CRC, because of primary resistance ,43,44,45ectively ,47,48,49herapies . More reherapies .However, even RAS wild type (RAS without mutations) patients can be anti-EGFR non-responders, due to additional mechanisms of intrinsic resistance, involving all components of EGFR signal transduction pathway, such as mutations in BRAF or phosphatidylinositol-4,5-bisphosphate 3-kinase, catalytic subunit alpha (PIK3CA) ,52, amplIn preclinical models, stimulation of MET receptor by HGF confers resistance to anti-EGFR monoclonal antibodies  and sensOf interest, overexpression of Transforming growth factor alfa (TGF-α), a specific EGFR ligand, induced EGFR–MET interaction, with subsequent MET phosphorylation and activation of downstream effectors in EGFR-independent manner causing cetuximab resistance in colorectal cancer cells . Thus, cHGF/MET mediates resistance to anti-EGFR inhibition mostly through ERK and AKT persistent phosphorylation . In addi versus panitumumab plus placebo in KRAS wild-type advanced CRC population [ versus 21% in control arm) and median duration of response , and a positive trend in median PFS [In a randomized phase Ib/II trial was tested AMG 102 , a humanized monoclonal antibody directed against HGF , in combpulation . Combinadian PFS ; howeverCurrently, rilotumumab is no longer under investigation in CRC, even if it could be proposed in selected MET positive tumors independently on KRAS status; we are waiting results of a recently completed phase II randomized study of the anti-MET antibody, onartuzumab, in association with standard first-line chemotherapy in CRC patients .Conversely, retrospective subgroup analysis of phase I/II randomized study proposing biweekly schedule of irinotecan and cetuximab plus the MET TKI tivantinib or placebo, in second line therapy of KRAS wild-type advanced CRC patients, failed to demonstrate a statistically significant increase in PFS ,65.Melanoma is a very poor prognosis cancer when diagnosed in advanced stage, with a median survival of 13 months. Treatment options are: chemotherapy with dacarbazine, monoclonal antibody anti- cytotoxic T-lymphocytes-associates antigen 4 (CTLA-4) ipililumab and vemurafenib for melanomas carrying BRAF V600E mutation ,67,68,69Among various RTKs studied in melanoma cells to explore pathways responsible for uncontrolled survival and growth, MET has emerged as one of the topmost mediator of proliferation and invasiveness stimulated by the paracrine or autocrine HGF production ,71.In vitro studies [ studies  revealedIn melanoma, V600E BRAF mutation results in constitutive activation of MAPK signaling and aberrant proliferation. PLX4032/vemurafenib, a BRAFV600E inhibitor, demonstrated good clinical activity in patients with BRAFV600E melanoma, although drug resistance occurs in almost all treated patients. Resistance to vemurafenib is associated with Mitogen-activated protein kinase kinase (MEK)-induced MAPK activation, independently from BRAF activation. MET amplification (at 7q21) has been identified as a mechanism of innate resistance to vemurafenib in one melanoma cell line, LM38, opening new possibilities for efficacious combinations of MET and BRAF inhibitors . et al analyzed in vitro and in vivo models of BRAF mutant cell lines correlating sensitiveness to vemurafenib and HGF expression. They confirmed that increased HGF reduces response to vemurafenib in BRAF mutant cell lines and similarly MET activation (by MET-agonistic antibody) in xenograft models blocked the anti-proliferative effect of vemurafenib. Moreover, the finding of higher plasma levels of circulating HGF in BRAF mutant melanoma patients suggested a trend toward a worse prognosis for these patients [More recently, Wilsonpatients .Apart of the cell autonomous mechanisms of drug resistance, some reports indicate an important role displayed by the stroma in the development of resistance. In particular, secretion of HGF by tumor surrounding stroma has been demonstrated, with the resulting activation of MET pathway leading to resistance to vemurafenib. As a result, the combination treatment with vemurafenib and MET inhibitors could represent a new therapeutic approach .MET gene transcription through chromatin looping, during treatment with vemurafenib. Interestingly, they demonstrated that, upon vemurafenib treatment of melanoma cells, the interaction between the DNA enhancer sequences MET + 63 kb and the MET transcription start site (TSS) significantly increased, suggesting an inducible chromatin looping downstream of BRAF inhibition [Recently, Webster ,75,76 inMET is considered a promising biomarker of worse prognosis in several human cancers. Prospective studies are needed to explore the potential predictive role of MET for benefit from molecularly targeted anti-MET agents. Preclinical studies identifying mechanisms of resistance to anti-EGFR drugs have been translated into several completed or ongoing clinical trials, including combinations of drugs targeting MET or HGF with known anti-EGFR agents.So far, however, early results from clinical trials have been disappointing. There are multiple potential reasons for these observations. Many clinical trials are undertaken without prospectively evaluating the specific subpopulation of drug-resistant patients: indeed, patients enrolled in most of these studies had not been selected by MET amplification/activation. So far, most studies have assessed the HGF/MET axis only in tumors at baseline, so excluding cases of secondary HGF/MET activation at metastatic progression and treatment resistance.Future studies should address the need to biopsy the most recent site of metastatic progression, since targeted therapy directed against HGF/MET may be of considerable value in surmounting both primary and acquired resistance in these selected populations.In addition, the optimal methods to assess MET are still under investigation, resulting in an inefficacious identification of tumors harboring MET activation.In conclusion, MET could be used as a “mixed” biomarker: negative prognostic value and positive predictive effect. For future analysis, appropriate selection of patient population who can effectively benefit from MET inhibitory treatment and adequate biomarker evaluation should be encouraged and strongly recommended.


U.S. Antibiotic Awareness Week is an annual observance to raise awareness about antibiotic resistance and the importance of appropriate antibiotic prescribing and use. This year’s observance coincides with the release of CDC’s updated educational initiative “Be Antibiotics Aware: Smart Use, Best Care,” and aims to engage health care professionals, advocacy groups, for-profit companies, state and local health departments, professional societies, the general public, the media, and others in efforts to improve antibiotic prescribing and use across all health care settings. This observance coincides with the World Health Organization’s World Antibiotic Awareness Week and European Antibiotic Awareness Day on November 18.Antibiotics save lives. When a patient needs antibiotics, the benefits outweigh the risks for side effects or antibiotic resistance. However, antibiotic resistance is one of the most urgent threats to the public’s health. Each year in the United States, approximately 2 million persons are infected with antibiotic-resistant bacteria, and approximately 23,000 die as a result.https://www.cdc.gov/antibiotic-use.Preventing antibiotic-resistant infections and protecting the nation’s health by improving antibiotic prescribing and use is a CDC priority. Additional information about “Be Antibiotics Aware” during U.S. Antibiotic Awareness Week is available at