Dysregulated metabolism can broadly affect therapy resistance by influencing compensatory signaling and expanding proliferation.,Given many BRAF-mutated melanoma patients experience disease progression with targeted BRAF inhibitors, we hypothesized therapeutic response is related to tumor metabolic phenotype, and that altering tumor metabolism could change therapeutic outcome.,We demonstrated the proliferative kinetics of BRAF-mutated melanoma cells treated with the BRAF inhibitor PLX4720 fall along a spectrum of sensitivity, providing a model system to study the interplay of metabolism and drug sensitivity.,We discovered an inverse relationship between glucose availability and sensitivity to BRAF inhibition through characterization of metabolic phenotypes using nearly a dozen metabolic parameters in Principle Component Analysis.,Subsequently, we generated rho0 variants that lacked functional mitochondrial respiration and increased glycolytic metabolism.,The rho0 cell lines exhibited increased sensitivity to PLX4720 compared to the respiration-competent parental lines.,Finally, we utilized the FDA-approved antiretroviral drug zalcitabine to suppress mitochondrial respiration and to force glycolysis in our cell line panel, resulting in increased PLX4720 sensitivity via shifts in EC50 and Hill slope metrics.,Our data suggest that forcing tumor glycolysis in melanoma using zalcitabine or other similar approaches may be an adjunct to increase the efficacy of targeted BRAF therapy.
Despite the discovery of heterotrimeric αβγ G proteins ∼25 years ago, their selective perturbation by cell-permeable inhibitors remains a fundamental challenge.,Here we report that the plant-derived depsipeptide FR900359 (FR) is ideally suited to this task.,Using a multifaceted approach we systematically characterize FR as a selective inhibitor of Gq/11/14 over all other mammalian Gα isoforms and elaborate its molecular mechanism of action.,We also use FR to investigate whether inhibition of Gq proteins is an effective post-receptor strategy to target oncogenic signalling, using melanoma as a model system.,FR suppresses many of the hallmark features that are central to the malignancy of melanoma cells, thereby providing new opportunities for therapeutic intervention.,Just as pertussis toxin is used extensively to probe and inhibit the signalling of Gi/o proteins, we anticipate that FR will at least be its equivalent for investigating the biological relevance of Gq.,Pertussis toxin is used extensively for perturbing Gαi/o pathways in the study of physiology and disease, but an equivalent inhibitor of Gαq signalling is not currently available to the research community.,Here the authors characterize FR900359 as a specific Gq inhibitor and demonstrate its utility to dissect GPCR signalling and its potential to inhibit melanoma cells.