HNF1B inhibits cell proliferation via repression of SMAD6 expression in prostate cancer

Prostate cancer is the most common malignancy in men in developed countries. In previous study, we identified HNF1B (Hepatocyte Nuclear Factor 1β) as a downstream effector of Enhancer of zeste homolog 2 (EZH2). HNF1B suppresses EZH2-mediated migration of two prostate cancer cell lines via represses the EMT process by inhibiting SLUG expression. Besides, HNF1B expression inhibits cell proliferation through unknown mechanisms. Here, we demonstrated that HNF1B inhibited the proliferation rate of prostate cancer cells. Overexpression of HNF1B in prostate cancer cells led to the arrest of G1 cell cycle and decreased Cyclin D1 expression. In addition, we re-explored data from ChIP-sequencing (ChIP-seq) and RNA-sequencing (RNA-seq), and demonstrated that HNF1B repressed Cyclin D1 via direct suppression of SMAD6 expression. We also identified CDKN2A as a HNF1B-interacting protein that would contribute to HNF1B-mediated repression of SMAD6 expression. In summary, we provide the novel mechanisms and evidence in support HNF1B as a tumour suppressor gene for prostate cancer.