Transforming growth factor­ß/miR­143­3p/cystatin B axis is a therapeutic target in human ovarian cancer.

ABSTRACT

We previously reported that cystatin B (CSTB) is a progression marker of human ovarian cancer (OC); however, the regulatory mechanism of CSTB and its function in OC remain unclear. The present study aimed to explore the mechanism underlying transforming growth factor-ß (TGF­ß) 1­mediated CSTB regulation, and to examine the function of CSTB on OC cell proliferation and apoptosis. Using the online program, miRWalk, a microRNA (miR)­143­3p was detected, which contains a homologous sequence of the potential binding site to the 3'­untranslated region (3'­UTR) of CSTB. A dual­luciferase reporter assay confirmed the interaction between miR­143­3p and CSTB 3'­UTR. Treating OC cells with miR­143­3p mimics or inhibitors resulted in a decrease or an increase of CSTB expression at mRNA and protein levels, respectively. Additionally, CSTB was significantly overexpressed, whereas miR­143­3p was downregulated in human OC tissues compared with normal ovarian tissues. A negative correlation between miR­143­3p and CSTB mRNA expression was observed in ovarian malignant tumors. The levels of primary and mature miR­143­3p expression were upregulated in OC cells after TGF­ß1 treatment; the action of TGF­ß1 was abolished in the presence of an inhibitor of TGF­ß type I receptor. These results indicated an axis between TGF­ß, miR­143­3p and CSTB in OC cells. Furthermore, high levels of CSTB expression were associated with the poor overall survival of patients with OC. Knockdown of CSTB resulted in a decrease in OC cell proliferation and arrested cells in G2/M phase. In addition, suppression of CSTB induced cell apoptosis. In conclusion, CSTB was overexpressed and miR­143­3p was downregulated in ovarian malignant tumors. Mature miR­143­3p directly bound CSTB 3'­UTR, leading to a decrease in CSTB expression in OC cells, which was regulated by TGF­ß1. Our findings suggest the potential therapeutic application of targeting the TGF­ß/miR­143­3p/CSTB axis for treating patients with OC.