Down-regulation of KRAS-interacting miRNA-143 predicts poor prognosis but not response to EGFR-targeted agents in colorectal cancer

BACKGROUND: MicroRNA-143 (miRNA-143) is frequently down-regulated in colorectal cancer (CRC) and may influence CRC cell proliferation, apoptosis and sensitivity to 5-fluorouracil. mRNA encoded by the KRAS oncogene has been identified as a target of miRNA-143. However, the prognostic significance of miRNA-143 expression and the ability to predict patient response to epidermal growth factor receptor (EGFR)-targeted agents have not yet been explored. METHODS: We examined 77 CRC patients who were identified by pyrosequencing to have wild-type KRAS and were subsequently treated with EGFR-targeted therapy with the monoclonal antibodies cetuximab or panitumumab. MicroRNA-143 expression was measured in CRC tissue and corresponding non-neoplastic colon tissue by RT-PCR and its expression level was correlated with clinico-pathological characteristics. Univariate and multivariate analyses were used to calculate cancer-specific survival (CSS). The progression-free survival (PFS) and objective response rates on EGFR-targeted therapy were also evaluated. RESULTS: Down-regulation of miRNA-143 was observed in 47 out of 77 (61%) tumours. Multivariate Cox regression analysis identified low levels of miRNA-143 expression as an independent prognostic factor with respect to CSS (hazard ratio 1.92, confidence interval = 1.1-3.4, P = 0.024). A significant difference was also observed with regard to PFS on EGFR-targeted therapy (P = 0.031), but there were no significant differences with regard to the objective response rates. CONCLUSION: Our data indicate that miRNA-143 expression levels serve as an independent prognostic biomarker for CRC in KRAS wild-type patients. No role for miRNA-143 expression as a predictive biomarker for EGFR-targeted agents could be identified. Given its negative impact on CSS and PFS, miRNA-143 represents a novel prognosticator and a promising drug target for patients with CRC. British Journal of Cancer (2012) 106, 1826-1832. doi:10.1038/bjc.2012.175 www.bjcancer.com Published online 1 May 2012 (C) 2012 Cancer Research UK