The mechanisms by which melanoma and other cancer cells evade anti-tumor immunity remain incompletely understood.,Here, we show that the growth of tumors formed by mutant BrafV600E mouse melanoma cells in an immunocompetent host requires their production of prostaglandin E2, which suppresses immunity and fuels tumor-promoting inflammation.,Genetic ablation of cyclooxygenases (COX) or prostaglandin E synthases in BrafV600E mouse melanoma cells, as well as in NrasG12D melanoma or in breast or colorectal cancer cells, renders them susceptible to immune control and provokes a shift in the tumor inflammatory profile toward classic anti-cancer immune pathways.,This mouse COX-dependent inflammatory signature is remarkably conserved in human cutaneous melanoma biopsies, arguing for COX activity as a driver of immune suppression across species.,Pre-clinical data demonstrate that inhibition of COX synergizes with anti-PD-1 blockade in inducing eradication of tumors, implying that COX inhibitors could be useful adjuvants for immune-based therapies in cancer patients.,•Cyclooxygenase in tumors induces PGE2 that subverts myeloid cell function•COX ablation in tumors enables immune control•COX inhibition synergizes with checkpoint blockade therapy•A COX inflammatory signature is conserved across mouse and human cancer biopsies,Cyclooxygenase in tumors induces PGE2 that subverts myeloid cell function,COX ablation in tumors enables immune control,COX inhibition synergizes with checkpoint blockade therapy,A COX inflammatory signature is conserved across mouse and human cancer biopsies,Cyclooxygenase-driven prostaglandin E2, produced by a variety of tumors, drives malignant growth through successful evasion of type I interferon and/or T-cell-dependent tumor elimination.,A remarkable synergy between cyclooxygenase inhibitors and checkpoint blockade immunotherapy results in tumor eradication.
Congenital melanocytic nevi (CMN) can be associated with neurological abnormalities and an increased risk of melanoma.,Mutations in NRAS, BRAF, and Tp53 have been described in individual CMN samples; however, their role in the pathogenesis of multiple CMN within the same subject and development of associated features has not been clear.,We hypothesized that a single postzygotic mutation in NRAS could be responsible for multiple CMN in the same individual, as well as for melanocytic and nonmelanocytic central nervous system (CNS) lesions.,From 15 patients, 55 samples with multiple CMN were sequenced after site-directed mutagenesis and enzymatic digestion of the wild-type allele.,Oncogenic missense mutations in codon 61 of NRAS were found in affected neurological and cutaneous tissues of 12 out of 15 patients, but were absent from unaffected tissues and blood, consistent with NRAS mutation mosaicism.,In 10 patients, the mutation was consistently c.181C>A, p.Q61K, and in 2 patients c.182A>G, p.Q61R.,All 11 non-melanocytic and melanocytic CNS samples from 5 patients were mutation positive, despite NRAS rarely being reported as mutated in CNS tumors.,Loss of heterozygosity was associated with the onset of melanoma in two cases, implying a multistep progression to malignancy.,These results suggest that single postzygotic NRAS mutations are responsible for multiple CMN and associated neurological lesions in the majority of cases.