Advances in melanoma treatment through targeted inhibition of oncogenic BRAF are limited owing to the development of acquired resistance.,The involvement of BRAFV600E in metabolic reprogramming of melanoma cells provides a rationale for co-targeting metabolism as a therapeutic approach.,We examined the effects of dichloroacetate (DCA), an inhibitor of pyruvate dehydrogenase kinase, on the growth and metabolic activity of human melanoma cell lines.,The combined effect of DCA and the BRAF inhibitor vemurafenib was investigated in BRAFV600E -mutated melanoma cell lines.,Vemurafenib-resistant cell lines were established in vitro and their sensitivity to DCA was tested.,DCA induced a reduction in glycolytic activity and intracellular ATP levels, and inhibited cellular growth.,Co-treatment of BRAFV600E-mutant melanoma cells with DCA and vemurafenib induced a greater reduction in intracellular ATP levels and cellular growth than either compound alone.,In addition, melanoma cells with in vitro acquired resistance to vemurafenib retained their sensitivity to DCA.,These results suggest that DCA potentiates the effect of vemurafenib through a cooperative attenuation of energy production.,Furthermore, the demonstration of retained sensitivity to DCA in melanoma cells with acquired resistance to vemurafenib could have implications for melanoma treatment.,The online version of this article (doi:10.1186/s12967-014-0247-5) contains supplementary material, which is available to authorized users.
Overcoming the notorious apoptotic resistance of melanoma cells remains a therapeutic challenge given dismal survival of patients with metastatic melanoma.,However, recent clinical trials using a BRAF inhibitor revealed encouraging results for patients with advanced BRAF mutant bearing melanoma, but drug resistance accompanied by recovery of phospho-ERK (pERK) activity present challenges for this approach.,While ERK1 and ERK2 are similar in amino acid composition and are frequently not distinguished in clinical reports, the possibility they regulate distinct biological functions in melanoma is largely unexplored.,Rather than indirectly inhibiting pERK by targeting upstream kinases such as BRAF or MEK, we directly (and near completely) reduced ERK1 and ERK2 using short hairpin RNAs (shRNAs) to achieve sustained inhibition of pERK1 and/or pERK2.,Using A375 melanoma cells containing activating BRAFV600E mutation, silencing ERK1 or ERK2 revealed some differences in their biological roles, but also shared roles by reduced cell proliferation, colony formation in soft agar and induced apoptosis.,By contrast, chemical mediated inhibition of mutant BRAF (PLX4032) or MEK (PD0325901) triggered less killing of melanoma cells, although they did inhibit proliferation.,Death of melanoma cells by silencing ERK1 and/or ERK2 was caspase dependent and accompanied by increased levels of Bak, Bad and Bim, with reduction in p-Bad and detection of activated Bax levels and loss of mitochondrial membrane permeability.,Rare treatment resistant clones accompanied silencing of either ERK1 and/or ERK2.,Unexpectedly, directly targeting ERK levels also led to reduction in upstream levels of BRAF, CRAF and pMEK, thereby reinforcing the importance of silencing ERK as regards killing and bypassing drug resistance.,Selectively knocking down ERK1 and/or ERK2 killed A375 melanoma cells and also increased the ability of PLX4032 to kill A375 cells.,Thus, a new therapeutic window is open for future clinical trials in which agents targeting ERK1 and ERK2 should be considered in patients with melanoma.