TGF-β1-regulated miR-3691-3p targets E2F3 and PRDM1 to inhibit prostate cancer progression

Transforming growth factor-β1(TGF-β1)acts as a tumor promoter in advanced prostate cancer(PCa).We speculated that microRNAs(miRNAs)that are inhibited by TGF-β1 might exert anti-tumor effects.To assess this,we identified several miRNAs downregulated by TGF-β1 in PCa cell lines and selected miR-3691-3p for detailed analysis as a candidate anti-oncogene miRNA.miR-3691-3p was expressed at significantly lower levels in human PCa tissue compared with paired benign prostatic hyperplasia tissue,and its expression level correlated inversely with aggressive clinical pathological features.Overexpression of miR-3691-3p in PCa cell lines inhibited proliferation,migration,and invasion,and promoted apoptosis.The miR-3691-3p target genes E2F transcription factor 3(E2F3)and PR domain containing 1,with ZNF domain(PRDM1)were upregulated in miR-3691-3p-overexpressing PCa cells,and silencing of E2F3 or PRDM1 suppressed PCa cell proliferation,migration,and invasion.Treatment of mice bearing PCa xenografts with a miR-3691-3p agomir inhibited tumor growth and promoted tumor cell apoptosis.Consistent with the negative regulation of E2F3 and PRDM1 by miR-3691-3p,both proteins were overexpressed in clinical PCa specimens compared with noncancerous prostate tissue.Our results indicate that TGF-β1-regulated miR-3691-3p acts as an anti-oncogene in PCa by downregulating E2F3 and PRDM1.These results provide novel insights into the mechanisms by which TGF-β1 contributes to the progression of PCa.