Combination therapy with vemurafenib (PLX4032/RG7204) and metformin in melanoma cell lines with distinct driver mutations

Abstract

BackgroundA molecular linkage between the MAPK and the LKB1-AMPK energy sensor pathways suggests that combined MAPK oncogene inhibition and metabolic modulation of AMPK would be more effective than either manipulation alone in melanoma cell lines.Materials and methodsThe combination of the BRAF inhibitor vemurafenib (formerly PLX4032) and metformin were tested against a panel of human melanoma cell lines with defined BRAF and NRAS mutations for effects on viability, cell cycle and apoptosis. Signaling molecules in the MAPK, PI3K-AKT and LKB1-AMPK pathways were studied by Western blot.ResultsSingle agent metformin inhibited proliferation in 12 out of 19 cell lines irrespective of the BRAF mutation status, but in one NRASQ61K mutant cell line it powerfully stimulated cell growth. Synergistic anti-proliferative effects of the combination of metformin with vemurafenib were observed in 6 out of 11 BRAFV600E mutants, including highly synergistic effects in two BRAFV600E mutant melanoma cell lines. Antagonistic effects were noted in some cell lines, in particular in BRAFV600E mutant cell lines resistant to single agent vemurafenib. Seven out of 8 BRAF wild type cell lines showed marginally synergistic anti-proliferative effects with the combination, and one cell line had highly antagonistic effects with the combination. The differential effects were not dependent on the sensitivity to each drug alone, effects on cell cycle or signaling pathways.ConclusionsThe combination of vemurafenib and metformin tended to have stronger anti-proliferative effects on BRAFV600E mutant cell lines. However, determinants of vemurafenib and metformin synergism or antagonism need to be understood with greater detail before any potential clinical utility of this combination.

Metformin Blocks Melanoma Invasion and Metastasis Development in AMPK/p53-Dependent Manner

“…These results were confirmed by retrospective epidemiologic studies that reported a decrease in cancer risk in patients with diabetes treated with metformin (12). In addition, metformin was reported by several groups, including ours, to inhibit melanoma cell proliferation (13)(14)(15)(16). In our previous study, we showed that metformin dramatically impairs the growth of melanoma tumors in vitro and in vivo by inducing autophagic cell death leading to massive apoptosis (13).…”

“…For this purpose, using in vitro and in vivo approaches, we and others previously showed the potent effects of the antidiabetic drug metformin on reduction of melanoma cells growth and xenograft development (13)(14)(15)(16). One crucial step of melanoma development appears to be promotion of an EMT-like transition, a process having central role during RGP and VGP progression, melanoma invasion, and metastatic dissemination of melanoma cells (19,20).…”

Metformin upregulates E-cadherin and inhibits B16F10 cell motility, invasion and migration

“…Studies have indicated that metformin efficiently suppresses the growth of various tumors, such as prostate carcinoma, and breast, lung and pancreatic cancer (11,12), which is in accordance with the results of a retrospective epidemiological study, showing a reduction in cancer risk in patients with diabetes who were receiving metformin (13). Furthermore, a number of studies have reported that metformin inhibits melanoma cell proliferation (14)(15)(16)(17).…”

Investigating Metformin for Cancer Prevention and Treatment: The End of the Beginning

“…A transformed cell adopting an "energy-saving" phenotype is unlikely to behave in an aggressive fashion, so a benefi cial cytostatic effect is plausible. However, in keeping with its evolutionary role, the activation of AMPK in certain contexts enhances survival (59)(60)(61). This may or may not have adverse clinical implications.…”

“…With VEGF inhibitors AMPK activation, which can be a consequence of metformin exposure, can lead to increased VEGF expression and enhanced survival under certain conditions. There is preclinical evidence that inhibition of VEGF expression synergizes with metformin exposure to reduce cancer growth and oppose prosurvival consequences of AMPK activation (59)(60)(61)(62).…”