miR-203 reverses chemoresistance in p53-mutated colon cancer cells through downregulation of Akt2 expression

In this study, we explored miR-203's role in the chemoresistance of colon cancer. We found that overexpression of miR-203 significantly decreased cell proliferation and survival, and induced cell apoptosis in the p53-mutated colon cancer cells. Importantly, miR-203 overexpression increased the cytotoxic role of paclitaxel in the p53-mutated colon cancer cells, but not in the p53 wild-type cells. We further demonstrated that the tumor suppressive role of miR-203 was mediated by negatively regulating Akt2 protein expression through mRNA degradation. The inhibition of Akt2 activity downregulated the protein expression of its downstream molecules involved in chemoresistance, such as MTDH and HSP90 genes. Also, overexpression of miR-203 decreased anti-apoptotic gene Bcl-xL expression and increased apoptotic proteins Bax and active caspase-3 levels. Our study is the first to identify the tumor suppressive role of overexpressed miR-203, describe its associated signaling pathways, and highlight the role of miR-203 in chemoresistance. (C) 2011 Elsevier Ireland Ltd. All rights reserved.