Suppressed miR-424 expression via upregulation of target gene Chk1 contributes to the progression of cervical cancer

Abstract

MicroRNAs (miRNAs) act as important gene regulators in human genomes and their aberrant expression links to many malignancies. We previously identified a different characteristic miRNA expression profile in cervical cancer from that in cervical normal tissues, including the downregulated miR-424. However, the role and mechanism of miR-424 in cervical cancer still remain unknown. Here, we focused on identifying the tumor-suppressive function and clinical significance of miR-424 and exploring the mechanistic relevance by characterizing its target. We showed a significantly decreased expression of miR-424 in 147 cervical cancer tissues versus 74 cervical normal tissues by performing quantitative RT-PCR. In 147 cervical cancer tissue samples, low-level expression of miR-424 was positively correlated with poor tumor differentiation, advanced clinical stage, lymph node metastasis and other poor prognostic clinicopathological parameters. Further in vitro observations showed that enforced expression of miR-424 inhibited cell growth by both enhancing apoptosis and blocking G1/S transition, and suppressed cell migration and invasion in two human cervical cancer cell lines, SiHa and CaSki, implying that miR-424 functions as a tumor suppressor in the progression of cervical cancer. Interestingly, overexpression of miR-424 inhibited the expression of protein checkpoint kinase 1 (Chk1) and phosphorylated Chk1 (p-Chk1) at residues Ser345 and decreased the activity of luciferase-reporter containing the 3'-untranslated region (UTR) of Chk1 with predicted miR-424-binding site. Moreover, miR-424 expression levels were inversely correlated with Chk1 and p-Chk1 protein levels in both cervical cancer and normal tissues. Furthermore, RNAi-mediated knockdown of Chk1 decreased matrix metalloproteinase 9 expression and phenocopied the tumor suppressive effects of miR-424 in cell models. Taken together, our results identify a crucial tumor suppressive role of miR-424 in the progression of cervical cancer at least partly via upreglating the expression of Chk1 and p-Chk1, and suggest that miR-424 might be a candidate of prognostic predictor or an anticancer therapeutic target for cervical cancer patients.