Malignant melanomas account for a substantial proportion of cancers worldwide and are largely resistant to conventional therapy. The heterogeneity and the invasiveness of melanomas present notable challenges for anti-cancer treatment. Recently, several mutations in RAF, RAS, and PTEN were identified that allow for prognosis of cancer development and progression. Therefore, inhibitors of the RAF-MEK-ERK pathway form attractive candidates for molecular-based targeted treatment of melanoma cancer. Here, we present the molecular characterization and chemosensitivity profiling of 18 human melanoma cell lines. Eight of these were established by Oncotest from human tumor xenografts originally derived from primary patient material. The molecular profiling included mutational analysis for BRAF, PIK3CA, KRAS, NRAS, TP53, and PTEN by sequencing. The chemosensitivity profiles were determined in vitro using a fluorescence-based cytotoxicity assay and included commonly used chemotherapeutic agents for treatment of melanoma, targeted agents (sorafenib and bortezomib) and various BRAF (PLX-4032, PLX-4720, GDC-0879) and MEK (CI-1040, PD0325901) inhibitors. The clinically relevant BRAF V600E substitution was the most prevalent mutation and was found in more than 50% of the melanoma cell lines. The chemosensitivity profiling revealed diverse patterns of selectivity and potency with mean IC50 values between 0.4 nM (vinblastine) and 8.3 µM (carboplatin). Each of the BRAF inhibitors tested was clearly more active in melanoma cell lines carrying a BRAF mutation. On average, IC50 values of BRAF inhibitors were more than 20-fold lower for the BRAF V600E mutated cell lines compared to the wild type cell lines. However, the BRAF mutated cell line MEXF 462NL was resistant towards BRAF inhibitors and it is warranted to compare its gene expression profile and mutational status with BRAF mutated cell lines responding to BRAF inhibitors. By using an ex vivo clonogenic assay, similar activity patterns for BRAF inhibitors were found, with mutated BRAF tumor xenografts showing markedly higher sensitivity. Potential synergistic activity of BRAF inhibitors with other inhibitors of the RAF-MEK-ERK pathway or with standard chemotherapeutic agents will be presented. The mutational status of selected cancer related genes, as well as responsiveness towards many cytotoxic and targeted agents was analyzed for 18 melanoma cell lines. This extensive genotypic and phenotypic characterization makes this melanoma cell line panel a valuable tool for in vitro profiling of novel compounds, in particular inhibitors of the RAF-MEK-ERK pathway.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 4170. doi:1538-7445.AM2012-4170