Reference Detail

Ref Type Journal Article
PMID (26351322)
Authors Whittaker SR, Cowley GS, Wagner S, Luo F, Root DE, Garraway LA
Title Combined Pan-RAF and MEK Inhibition Overcomes Multiple Resistance Mechanisms to Selective RAF Inhibitors.
Journal Molecular cancer therapeutics
Vol 14
Issue 12
Date 2015 Dec
URL
Abstract Text RAF and MEK inhibitors are effective in BRAF-mutant melanoma but not in BRAF-mutant colorectal cancer. To gain additional insights into this difference, we performed a genome-scale pooled shRNA enhancer screen in a BRAF-mutant, RAF inhibitor-resistant colorectal cancer cell line exposed to the selective RAF inhibitor PLX4720. We identified multiple genes along the receptor tyrosine kinase (RTK)/mitogen-activated protein kinase (MAPK) signaling axis that, when suppressed, either genetically or pharmacologically, sensitized cells to the selective RAF inhibitor through sustained inhibition of MAPK signaling. Strikingly, CRAF was a key mediator of resistance that could be overcome by the use of pan-RAF inhibitors in combination with a MEK inhibitor. Furthermore, the combination of pan-RAF and MEK inhibitors displayed strong synergy in melanoma and colorectal cancer cell lines with RAS-activating events such as RTK activation, KRAS mutation, or NF1 loss-of-function mutations. Combinations of selective RAF inhibitors, such as PLX4720 or dabrafenib, with MEK inhibitors did not incur such profound synergy, suggesting that inhibition of CRAF by pan-RAF inhibitors plays a key role in determining cellular response. Importantly, in contrast to the modest activity seen with single-agent treatment, dual pan-RAF and MEK inhibition results in the induction of apoptosis, greatly enhancing efficacy. Notably, combined pan-RAF and MEK inhibition can overcome intrinsic and acquired resistance to single-agent RAF/MEK inhibition, supporting dual pan-RAF and MEK inhibition as a novel therapeutic strategy for BRAF- and KRAS-mutant cancers.

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Molecular Profile Treatment Approach
Gene Name Source Synonyms Protein Domains Gene Description Gene Role
Therapy Name Drugs Efficacy Evidence Clinical Trials
Drug Name Trade Name Synonyms Drug Classes Drug Description
Variant Impact Protein Effect Variant Description Associated with drug Resistance
Molecular Profile Indication/Tumor Type Response Type Therapy Name Approval Status Evidence Type Efficacy Evidence References
BRAF mutant colorectal cancer decreased response PLX4720 Preclinical - Cell culture Actionable In a preclinical study, BRAF mutant colorectal cancer cell lines demonstrated reduced sensitivity to PLX4720 in culture (PMID: 26351322). 26351322
BRAF mut PTPN11 dec exp colorectal cancer sensitive PLX4720 Preclinical - Cell culture Actionable In a preclinical study, knocking down of Ptpn11 expression via shRNA sensitized BRAF mutant colorectal cancer cell lines to PLX4720 in culture (PMID: 26351322). 26351322
BRAF mutant colorectal cancer sensitive AZ628 + Selumetinib Preclinical - Cell culture Actionable In a preclinical study, Selumetinib (AZD6244) and AZ628 synergistically inhibited Mapk signaling and cell proliferation in BRAF mutant colorectal cancer cell lines in culture (PMID: 26351322). 26351322