Abstract SY27-02: Tumour heterogeneity and therapy resistance in melanoma

Abstract

Abstract Solid tumors are structurally very complex; they consist of heterogeneous cancer cell populations, other non-cancerous cell types and a distinct extracellular matrix. Interactions of cancer cells with non-cancerous cells is well investigated, and our recent work in melanoma has demonstrated that the cellular environment that surrounds cancer cells has a major impact on the way a patient responds to MAP-kinase pathway targeting therapy. We have shown that intra-tumor signaling within a heterogeneous tumor can have a major impact on the efficacy of BRAF and MEK inhibitors. With the increasing evidence of genetic and phenotypic heterogeneity within tumors, intra-tumor signaling between individual cancer-cell subpopulations is therefore a crucial factor that needs to be considered in future therapy approaches. Our work has identified the ‘melanocyte-lineage survival oncogene’ MITF as an important player in phenotypic heterogeneity (MITFhigh and MITFlow cells) in melanoma, and MITF expression levels are crucial for the response to MAP-kinase pathway targeted therapy. We found that ‘MITF heterogeneity’ can be caused by cell-autonomous mechanisms or by the microenvironment, including the immune-microenvironment. We have identified various mechanisms underlying MITF action in resistance to BRAF and MEK inhibitors in melanoma. In MITFhigh expressing cells, MITF confers cell-autonomous resistance to MAP-kinase pathway targeted therapy. Moreover, it appears that in melanomas heterogeneous for MITF expression (MITFhigh and MITFlow cells), individual subpopulations of resistant and sensitive cells communicate and MITF can contribute to overall tumor-resistance through intra-tumor signaling. Finally, we have identified a novel approach of interfering with MITF action, which profoundly sensitizes melanoma to MAP-kinase pathway targeted therapy. Citation Format: Claudia Wellbrock. Tumour heterogeneity and therapy resistance in melanoma. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr SY27-02. doi:10.1158/1538-7445.AM2015-SY27-02