Abstract A43: BRAF-mutated melanomas exhibit distinct metabolic programs that may determine therapeutic response

Abstract

Abstract Nearly 60% of melanomas have an activating mutation in the BRAF kinase. Targeted inhibition of mutant BRAF has prolonged overall survival, but responses are highly variable. To investigate the response variability, we utilized a panel of eight BRAF V600E or D mutated melanoma cell lines and treated them with the targeted mutant BRAF inhibitor, PLX4720. Under PLX4720 treatment, the cell lines exhibited a spectrum of concentration-dependent sensitivities based on measured proliferative rates over 96 hours of treatment. Since dysregulated metabolism has been shown to influence therapy resistance, we hypothesized that this spectrum of sensitivity would vary concordantly along a single metabolic phenotype. To test this hypothesis we measured glucose and amino acid uptake, lactate production, extracellular acidification upon mitochondrial inhibition, and proliferative rates under lactogenic glycolysis (oxamic acid) and ATP-synthase (oligomycin) inhibition in the cell lines. Interestingly, we did not find a single metabolic spectrum but rather unique clusters of metabolic phenotypes ranging from glycolysis-, amino-acid-, and oxidative phosphorylation-dependent to high metabolically flexible cell lines. Particularly, some cell lines were extremely sensitive to even low concentrations of oligomycin, whereas the majority of cell lines exhibited concentration-independent decreases of approximately ½ their proliferative rate under vehicle control. Metabolism and cell growth are intimately linked to cell cycle status, so we asked whether sensitivity to PLX4720 is abrogated when cells are selected under PLX4720 treatment. Using a fluorescence ubiquitination cell cycle indicator (FUCCI) to label dividing cells (G2/S/M phases), we pre-treated melanomas with PLX4720 or vehicle, flow-sorted FUCCI+ and FUCCI-cells, then re-treated with PLX4720. This revealed there was no positive selection for PLX4720-resistant subclones, as the PLX4720 treated FUCCI+/- cells pheno-copied the proliferative rates of the vehicle treated FUCCI+/- cells. Taken together, our results suggest that BRAF-mutated melanomas exist in a metabolically rich landscape that may be an important factor in response to targeted BRAF inhibition. The long-term goal is to translate these metabolic differences clinically, possibly by coupling metabolic and oncogene targeted therapies. Citation Format: Keisha N. Hardeman, Chengwei Peng, Bishal Paudel, Darren Tyson, Jamey D. Young, Vito Quaranta, Joshua P. Fessel. BRAF-mutated melanomas exhibit distinct metabolic programs that may determine therapeutic response. [abstract]. In: Proceedings of the AACR Special Conference: Metabolism and Cancer; Jun 7-10, 2015; Bellevue, WA. Philadelphia (PA): AACR; Mol Cancer Res 2016;14(1_Suppl):Abstract nr A43.