Knockdown of MiR-20a Enhances Sensitivity of Colorectal Cancer Cells to Cisplatin by Increasing ASK1 Expression

Abstract

Background/Aims: Platinum-based chemotherapy is one of the most important strategies for treatment of colorectal cancer. To improve the therapeutic efficiency, adjuvant drugs were sought to sensitize colorectal cancer cells to platinum-based agents such as cisplatin. As previous research has shown that miRNAs are associated with chemosensitivity, we aimed to alter miRNA regulation in colorectal cancer cells to increase their chemosensitivity. Methods: MTT assays were performed to determine the viability of HT29, SW480, and LoVo cells. Quantitative real time polymerase chain reaction (qRT-PCR) was performed to examine the expression of miR-20a in these cell lines. Regulation of the miR-20a/ASK1 axis was confirmed by western blotting and luciferase reporter assays. After treatment with miR-20a inhibitor (anti-miR-20a) and cisplatin, production of reactive oxygen species (ROS), mitochondrial membrane potential, and apoptosis were measured by flow cytometry. Activation of ASK1, Bcl-xl, JNK, and caspase-9, -7, and -3 was detected by western blotting. Results: miR-20a was overexpressed in colorectal cancer cell lines. Furthermore, knockdown of miR-20a increased the sensitivity of colorectal cancer cells to cisplatin treatment in vitro and in vivo. We demonstrated that the ASK1 gene was the target of miR-20a, and knockdown of miR-20a increased the expression of ASK1 in colorectal cancer cells. As cisplatin treatment induced production of ROS, knockdown of miR-20a enhanced ROS signaling through promoting the phosphorylation of ASK1. Phosphorylation of JNK and the subsequent mitochondrial apoptosis were triggered by the combination of cisplatin and anti-miR-20a. Conclusions: Knockdown of miR-20a enhanced sensitivity of colorectal cancer cells to cisplatin through the ROS/ASK1/JNK pathway.