MicroRNA Expression in KRAS- and BRAF-mutated Colorectal Cancers.

Abstract

KRAS and BRAF are two genes commonly mutated in colorectal cancer (CRC). Even though BRAF is a downstream target of KRAS in the MAPK signalling pathway, KRAS- and BRAF-mutated CRCs are found to display several different clinical and histopathological features. We investigated whether a differential expression of microRNAs (miRNAs) could explain the clinicopathological differences seen between KRAS- and BRAF-mutated CRCs. Using a PCR array, we analyzed the expression of 84 different miRNAs in CRC cell lines wild-type in KRAS and BRAF, or mutated in KRAS or BRAF. Ten miRNAs were selected for further analyses in tumor tissue specimens (let-7a, let-7i, miR-10a, miR-10b, miR-31, miR-100, miR-181a, miR-181b, miR-372, and miR-373). BRAF-mutated tumors were found to express significantly higher levels of miR-31 as well as significantly lower levels of miR-373, compared to wild-type tumors. Our results suggest that KRAS- and BRAF-mutated CRCs may have different miRNA signatures compared to CRC tumors wild-type in KRAS and BRAF. However, no difference in expression levels between KRAS- and BRAF-mutated tumors was evident for the miRNAs analyzed in this study.