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Germline MBD4 Mutations and Predisposition to Uveal Melanoma

ABSTRACT: Uveal melanoma (UM) arises from malignant transformation of melanocytes from the uveal tract. This rare tumor has a poor outcome with frequent liver metastases and primary resistance to treatment1. The only strong predisposing condition for UM is the BAP1 tumor predisposition syndrome due to germline BAP1 deleterious mutations. UMs are generally characterized by a very low tumor mutation burden (TMB). However, some UMs display a high level of CpG to TpG mutations associated with MBD4 inactivation. Here, we explored the incidence of germline MBD4 variants in a consecutive series of 1, 099 primary UMs, and identified 8 deleterious MBD4 mutations, an aprox 10-fold increased incidence compared with the general population. These mutations were associated with a high TMB in tested UMs. We thus demonstrated that MBD4 is the second major predisposing gene for UM.

PROVIDER: EGAS00001003941 | EGA |

REPOSITORIES: EGA

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Project description:Background and Aims: Uveal melanoma (UM), the most common primary intraocular tumor in adults, is characterized by marked variability in its ability to metastasize. In fact, up to half the patients with UM develop distant metastases, most commonly to the liver. Mutations in alpha G-protein subunits, GNAQ and GNA11, are found in most primary UM, in a mutually exclusive pattern. Also, mutations in SF3B1, EIF1AX, and BAP1, are associated with markedly distinct prognoses Targeted therapy with MAP kinase inhibitors has been unsuccessful in the treatment of uveal melanoma (UM). The constitutive activation of GNAq and GNA11, typical of MU, determines the activation not only of the MAP kinases but also of the transcription factors YAP / TAZ. It is known that when statins are used to inhibit the HMGCR activity in the mevalonate pathway, the nuclear localization and transcriptional activity of YAP-TAZ are also inhibited mediating a potential anti-cancer activity Methods: We investigated the sensitivity to drugs of a panel of 6 lines of MU, two metastatic and 4 derived from primary tumors, of the latter two were monosomic. We established the IC50s of the individual drugs and the effects of the combinations. The synergistic effects of drugs were studied using MTT proliferation tests, cell cycle and apoptosis. The most synergistic combination was tested in vivo in NSG mice. Results: The synergistic concentrations of trametinib and cerivastatin (T+C) induced a massive arrest of proliferation and cell cycle and an increase of apoptosis 72 hours after the start of treatment particularly in the monosomic, BAP1 mutated UPMM3 cell line. The synergistic effect of T+C was reached after 7 instead of 3 days. In the metastatic OMM2.5 cell line. T+C treatments reduced ERK and AKT phosphorylation and increased the cytoplasmatic, inactive form of YAP. T+C treatment of NSG mice transplanted with the monosomic UM cell line reduced significantly tumor growth. Conclusion: This study suggests that statins potentiate the efficacy of MEK inhibitors in the therapy of UM

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Germline MBD4 Mutations and Predisposition to Uveal Melanoma

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