title: Phenformin enhances the therapeutic benefit of BRAF(V600E) inhibition in melanoma.
abstract: Biguanides, such as the diabetes therapeutics metformin and phenformin, have demonstrated antitumor activity both in vitro and in vivo. The energy-sensing AMP-activated protein kinase (AMPK) is known to be a major cellular target of biguanides. Based on our discovery of cross-talk between the AMPK and v-Raf murine sarcoma viral oncogene homolog B1 (BRAF) signaling pathways, we investigated the antitumor effects of combining phenformin with a BRAF inhibitor PLX4720 on the proliferation of BRAF-mutated melanoma cells in vitro and on BRAF-driven tumor growth in vivo. Cotreatment of BRAF-mutated melanoma cell lines with phenformin and PLX4720 resulted in synergistic inhibition of cell viability, compared with the effects of the single agent alone. Moreover, treatment with phenformin significantly delayed the development of resistance to PLX4720 in cultured melanoma cells. Biochemical analyses showed that phenformin and PLX4720 exerted cooperative effects on inhibiting mTOR signaling and inducing apoptosis. Noticeably, phenformin selectively targeted subpopulations of cells expressing JARID1B, a marker for slow cycling melanoma cells, whereas PLX4720 selectively targeted JARID1B-negative cells. Finally, in contrast to their use as single agents, the combination of phenformin and PLX4720 induced tumor regression in both nude mice bearing melanoma xenografts and in a genetically engineered BRAF(V600E)/PTEN(null)-driven mouse model of melanoma. These results strongly suggest that significant therapeutic advantage may be achieved by combining AMPK activators such as phenformin with BRAF inhbitors for the treatment of melanoma.
authors.affiliation: Cutaneous Biology Research Center, Massachusetts General Hospital and Harvard Medical School, Charlestown, MA 02129.
authors.forename: Ping
authors.initials: P
authors.lastname: Yuan
authors.forename: Koichi
authors.initials: K
authors.lastname: Ito
authors.forename: Rolando
authors.initials: R
authors.lastname: Perez-Lorenzo
authors.forename: Christina
authors.initials: C
authors.lastname: Del Guzzo
authors.forename: Jung Hyun
authors.initials: JH
authors.lastname: Lee
authors.forename: Che-Hung
authors.initials: CH
authors.lastname: Shen
authors.forename: Marcus W
authors.initials: MW
authors.lastname: Bosenberg
authors.forename: Martin
authors.initials: M
authors.lastname: McMahon
authors.forename: Lewis C
authors.initials: LC
authors.lastname: Cantley
authors.forename: Bin
authors.initials: B
authors.lastname: Zheng
mesh_terms: D000704:Analysis of Variance; D000818:Animals; D000971:Antineoplastic Combined Chemotherapy Protocols / Q000494:pharmacology; D017209:Apoptosis / Q000187:drug effects; D049109:Cell Proliferation / Q000187:drug effects; D004268:DNA-Binding Proteins / Q000378:metabolism; D007150:Immunohistochemistry; D007211:Indoles / Q000008:administration & dosage / Q000494:pharmacology*; D056484:Jumonji Domain-Containing Histone Demethylases / Q000378:metabolism; D008545:Melanoma / Q000188:drug therapy* / Q000235:genetics; D051379:Mice; D020125:Mutation, Missense / Q000235:genetics; D010629:Phenformin / Q000008:administration & dosage / Q000494:pharmacology*; D048493:Proto-Oncogene Proteins B-raf / Q000037:antagonists & inhibitors* / Q000235:genetics; D013449:Sulfonamides / Q000008:administration & dosage / Q000494:pharmacology*
chemical_list: D004268:DNA-Binding Proteins; D007211:Indoles; C528407:PLX 4720; D013449:Sulfonamides; D010629:Phenformin; D056484:Jumonji Domain-Containing Histone Demethylases; C485614:Kdm5b protein, mouse; C482120:Braf protein, mouse; D048493:Proto-Oncogene Proteins B-raf
keywords: LKB1; Vemurafenib