A subset of colorectal carcinomas express c-KIT protein independently of BRAF and/or KRAS activation.

c-KIT is a tyrosine kinase receptor found to be overexpressed in several tumours, namely, GISTs, breast, lung, prostate, ovarian and colorectal carcinomas (CRC). We aimed at determining the frequency of c-KIT expression and mutations in a series of 109 CRC cases (73 primary tumours and 36 lymph node metastases) characterised for KRAS and BRAF mutations. We also aimed at analysing the cellular effects of STI571/Gleevec in CRC-derived cell lines displaying c-KIT expression and KRAS or BRAF mutations. By immunohistochemistry, we found c-KIT overexpression in 15% (11/73) of primary tumours and in 14% (5/36) of metastasis; however, cases showing overexpression did not show c-kit mutations in hotspot regions. The majority (64%) of primary tumours with c-KIT overexpression had mutations at KRAS-BRAF genes. The same was true for 60% of the metastases. We treated CRC cell lines with STI571/Gleevec and verified that it inhibits proliferation and induces apoptosis in all cell lines. In conclusion, overexpression of c-KIT is observed in a subset of primary and CRC metastases in the absence of c-kit mutations. STI571/Gleevec increases apoptosis in CRC cell lines independently of its genetic profile, suggesting that STI571/Gleevec is likely to be an alternative drug for the clinical trials of CRC.