Clinical Acquired Resistance to RAF Inhibitor Combinations in BRAF-Mutant Colorectal Cancer through MAPK Pathway Alterations
- PMID: 25673644
- PMCID: PMC4390490
- DOI: 10.1158/2159-8290.CD-14-1518
Clinical Acquired Resistance to RAF Inhibitor Combinations in BRAF-Mutant Colorectal Cancer through MAPK Pathway Alterations
Abstract
BRAF mutations occur in approximately 10% of colorectal cancers. Although RAF inhibitor monotherapy is highly effective in BRAF-mutant melanoma, response rates in BRAF-mutant colorectal cancer are poor. Recent clinical trials of combined RAF/EGFR or RAF/MEK inhibition have produced improved efficacy, but patients ultimately develop resistance. To identify molecular alterations driving clinical acquired resistance, we performed whole-exome sequencing on paired pretreatment and postprogression tumor biopsies from patients with BRAF-mutant colorectal cancer treated with RAF inhibitor combinations. We identified alterations in MAPK pathway genes in resistant tumors not present in matched pretreatment tumors, including KRAS amplification, BRAF amplification, and a MEK1 mutation. These alterations conferred resistance to RAF/EGFR or RAF/MEK combinations through sustained MAPK pathway activity, but an ERK inhibitor could suppress MAPK activity and overcome resistance. Identification of MAPK pathway reactivating alterations upon clinical acquired resistance underscores the MAPK pathway as a critical target in BRAF-mutant colorectal cancer and suggests therapeutic options to overcome resistance.
Significance: RAF inhibitor combinations represent promising approaches in clinical development for BRAF-mutant colorectal cancer. Initial characterization of clinical acquired resistance mechanisms to these regimens identified several MAPK pathway alterations driving resistance by reactivating MAPK signaling, highlighting the critical dependence of BRAF-mutant colorectal cancers on MAPK signaling and offering potential strategies to overcome resistance.
©2015 American Association for Cancer Research.
Figures
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Comment in
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Old Habits Die Hard: Addiction of BRAF-Mutant Cancer Cells to MAP Kinase Signaling.Cancer Discov. 2015 Apr;5(4):348-50. doi: 10.1158/2159-8290.CD-15-0221. Cancer Discov. 2015. PMID: 25847954 Free PMC article.
References
-
- Davies H, Bignell GR, Cox C, Stephens P, Edkins S, Clegg S, et al. Mutations of the BRAF gene in human cancer. Nature. 2002;417:949–54. - PubMed
-
- Richman SD, Seymour MT, Chambers P, Elliott F, Daly CL, Meade AM, et al. KRAS and BRAF mutations in advanced colorectal cancer are associated with poor prognosis but do not preclude benefit from oxaliplatin or irinotecan: results from the MRC FOCUS trial. Journal of clinical oncology : official journal of the American Society of Clinical Oncology. 2009;27:5931–7. - PubMed
-
- Montagut C, Settleman J. Targeting the RAF-MEK-ERK pathway in cancer therapy. Cancer letters. 2009;283:125–34. - PubMed
-
- Long GV, Stroyakovskiy D, Gogas H, Levchenko E, de Braud F, Larkin J, et al. Combined BRAF and MEK inhibition versus BRAF inhibition alone in melanoma. The New England journal of medicine. 2014;371:1877–88. - PubMed
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