Supplementary Figure S1. Copy number increase of MDM2 gene at progression after vemurafenib+panitumumab. Supplementary Figure S2. Representative examples of colorectal carcinomas bearing BRAF mutations and MET gene copy number gain. Supplementary Figure S3. Untreated WiDr parental cells exhibit similar levels of activated RAS-GTP protein compared to their MET-amplified resistant derivatives treated with encorafenib+cetuximab+alpelisib (E+C+A).
Funding
AIRC
Fondo per la Ricerca Locale
Universitá di Torino
the Fondazione Piemontese per la Ricerca sul Cancro
European Community's Seventh Framework Programme
ARTICLE ABSTRACT
A patient with metastatic BRAF-mutated colorectal cancer initially responded to combined EGFR and BRAF inhibition with panitumumab plus vemurafenib. Pre-existing cells with increased MET gene copy number in the archival tumor tissue likely underwent clonal expansion during treatment, leading to the emergence of MET amplification in the rebiopsy taken at progression. In BRAF-mutated colorectal cancer cells, ectopic expression of MET conferred resistance to panitumumab and vemurafenib, which was overcome by combining BRAF and MET inhibition. Based on tumor genotyping and functional in vitro data, the patient was treated with the dual ALK–MET inhibitor crizotinib plus vemurafenib, thus switching to dual MET and BRAF blockade, with rapid and marked effectiveness of such strategy. Although acquired resistance is a major limitation to the clinical efficacy of anticancer agents, the identification of molecular targets emerging during the first treatment may afford the opportunity to design the next line of targeted therapies, maximizing patient benefit.Significance: MET amplification is here identified—clinically and preclinically—as a new mechanism of resistance to EGFR and BRAF dual/triple block combinations in BRAF-mutated colorectal cancer. Switching from EGFR to MET inhibition, while maintaining BRAF inhibition, resulted in clinical benefit after the occurrence of MET-driven acquired resistance. Cancer Discov; 6(9); 963–71. ©2016 AACR.This article is highlighted in the In This Issue feature, p. 932
