Identification of Reprogramming of the Kinome following Vemurafenib Treatment in BRAF mutant Colorectal Cancer Cells

Robbie Carson, Murugan Kalimutho, Philip Dunne, Catherine Fenning, Patrick Johnston, Sandra Van Schaeybroeck

Research output: Chapter in Book/Report/Conference proceedingConference contribution

Abstract

Background
Oncogenic mutations in BRAF occur in 8% of patients with advanced colorectal cancer (CRC) and have been shown to correlate with poor prognosis. In contrast to BRAF mutant (MT) melanoma, where the BRAF inhibitor Vemurafenib (PLX4032) has shown significant increases in response rates and overall survival compared to standard Dacarbazine treatment, only minor responses to Vemurafenib treatment have been reported in BRAFMT CRC. Clear understanding of the vulnerabilities of BRAFMT CRC is important, and identification of druggable targets uniquely required by BRAFMT CRC tumours has the potential to fill a gap in the therapeutic armamentarium of advanced CRC. The aim of this study was to identify novel resistance mechanisms to vemurafenib treatment in BRAFMT CRC by examining the Vemurafenib kinome response signature.

Method
Isogenic paired BRAFMT/WT RKO and BRAFMT/WT VACO 432 cells were used. Protein activity/expression was determined using receptor tyrosine kinase arrays and Western blotting.

Results
The BRAFMT RKO and VACO432 cells were significantly more sensitive (1.5- and 3-lower IC50; 5- and 20-fold lower IC20 dose) to Vemurafenib treatment than the BRAFWT RKO and VACO432 cell lines respectively. Using receptor tyrosine kinase (RTK) arrays, we found acute increases in activity of a number of RTKs with a critical role in EMT-cell adhesion/migration following Vemurafenib treatment, especially in the BRAFMT CRC cells. In particular, down-regulation of members of the EpH (EpHA4, EpHA2) family and AXL using RNAi or small molecule inhibition, resulted in strong synergistic increase in apoptosis when combined with Vemurafenib treatment in the BRAFMT cells. Interestingly, EpHA2 and AXL silencing also inhibited migration of BRAFMT cells, alone and in context of Vemurafenib treatment.

Conclusion
This study demonstrates the utility of RTK profiling to identify novel mechanisms of resistance to Vemurafenib treatment and novel treatment strategies for BRAFMT CRC tumours.
Original languageEnglish
Title of host publicationIdentification of Reprogramming of the Kinome following Vemurafenib Treatment in BRAF mutant Colorectal Cancer Cells
Place of PublicationProffered paper sessions
PublisherNational Cancer Research Institute
Publication statusPublished - Nov 2012

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