Vemurafenib resistance reprograms melanoma cells towards glutamine dependence

Abstract

BackgroundV600BRAF mutations drive approximately 50% of metastatic melanoma which can be therapeutically targeted by BRAF inhibitors (BRAFi) and, based on resistance mechanisms, the combination of BRAF and MEK inhibitors (BRAFi + MEKi). Although the combination therapy has been shown to provide superior clinical benefits, acquired resistance is still prevalent and limits the overall survival benefits. Recent work has shown that oncogenic changes can lead to alterations in tumor cell metabolism rendering cells addicted to nutrients, such as the amino acid glutamine. Here, we evaluated whether melanoma cells with acquired resistance display glutamine dependence and whether glutamine metabolism can be a potential molecular target to treat resistant cells.MethodsIsogenic BRAFi sensitive parental V600BRAF mutant melanoma cell lines and resistant (derived by chronic treatment with vemurafenib) sub-lines were used to assess differences in the glutamine uptake and sensitivity to glutamine deprivation. To evaluate a broader range of resistance mechanisms, isogenic pairs where the sub-lines were resistant to BRAFi + MEKi were also studied. Since resistant cells demonstrated increased sensitivity to glutamine deficiency, we used glutaminase inhibitors BPTES [bis-2-(5 phenylacetamido-1, 2, 4-thiadiazol-2-yl) ethyl sulfide] and L–L-DON (6-Diazo-5-oxo-l-norleucine) to treat MAPK pathway inhibitor (MAPKi) resistant cell populations both in vitro and in vivo.ResultsWe demonstrated that MAPKi-acquired resistant cells uptook greater amounts of glutamine and have increased sensitivity to glutamine deprivation than their MAPKi-sensitive counterparts. In addition, it was found that both BPTES and L-DON were more effective at decreasing cell survival of MAPKi-resistant sub-lines than parental cell populations in vitro. We also showed that mutant NRAS was critical for glutamine addiction in mutant NRAS driven resistance. When tested in vivo, we found that xenografts derived from resistant cells were more sensitive to BPTES or L-DON treatment than those derived from parental cells.ConclusionOur study is a proof-of-concept for the potential of targeting glutamine metabolism as an alternative strategy to suppress acquired MAPKi-resistance in melanoma.

A Tale of Two Glutaminases: Homologous Enzymes with Distinct Roles in Tumorigenesis

“…The Cancer Genome Atlas (TCGA) pan-cancer gene expression data show high expression of GLS in acute myeloid leukemia, adrenocortical cancer, triple-negative breast cancer, colorectal cancer, kidney clear or papillary cell carcinoma, lung adenocarcinoma, melanoma, mesothelioma, pancreatic cancer, sarcoma and thyroid cancer [78,79]. Of these, GLS activity has been shown to be important for growth of acute myeloid leukemia [80][81][82], breast cancer [61,64,83,84], colorectal cancer [85], kidney cancer [86,87], lung cancer [88], melanoma [89,90] and pancreatic cancer cells [91] in studies that utilized smallmolecule inhibitors or gene-silencing approaches in cell lines. Further, glioblastoma cell lines have been found to be sensitive to glutaminase inhibitors in vitro, despite having relatively low GLS expression according to TCGA data [80,92].…”

Translation reprogramming is an evolutionarily conserved driver of phenotypic plasticity and therapeutic resistance in melanoma

“…Although it can be synthesized de novo, many cells, especially cancer cells (Wise and Thompson 2010), including melanoma , require its exogenous supply, and glutamine is among one of five key amino acids depleted in melanoma tumor cores (Pan et al 2016). Moreover, BRAF inhibitorresistant melanomas exhibit a strong glutamine addiction (Hernandez-Davies et al 2015;Baenke et al 2016).…”

Erratum: From Krebs to clinic: glutamine metabolism to cancer therapy

“…BRAF inhibition BRAF inhibition resistance causes a shift to glutamine dependence, and so combination therapy may be used to combat this resistance 254 .…”