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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. | ||||||||||||
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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. |
Molecular Profile | Treatment Approach |
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Therapy Name | Drugs | Efficacy Evidence | Clinical Trials |
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Gene | Variant | Impact | Protein Effect | Variant Description | Associated with drug Resistance |
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Molecular Profile | Indication/Tumor Type | Response Type | Therapy Name | Approval Status | Evidence Type | Efficacy Evidence | References |
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BRAF mutant | colorectal cancer | sensitive | AZ628 + Selumetinib | Preclinical - Cell culture | Actionable | In a preclinical study, Koselugo (selumetinib) and AZ628 synergistically inhibited Mapk signaling and cell proliferation in BRAF mutant colorectal cancer cell lines in culture (PMID: 26351322). | 26351322 |
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 |