ABSTRACT. We examined microRNA-181b (miRNA) expression in prostate cancer tissues and its effect on the prostate cancer cell line PC-3. Tissues from 27 cases of prostate cancer and 30 samples of normal human prostate were collected by surgical removal. Total miRNA was extracted, and the relative expression of miR-181b was quantified using RT-PCR. miR-181b ASO was transfected into prostate cancer PC-3 cells. miR-181b expression in transfected and non-transfected cells was measured using RT-PCR. Changes in cell apoptosis were measured using flow cytometry. MTT and cell growth curve methods were used to assess the influence of miR-181b expression on cell proliferation. The changes in cell invasive ability in vitro were detected using the Transwell chamber method. miR-181b was up-regulated in the prostate cancer tissues compared with the normal prostate samples. It was down-regulated after miR-181b ASO MicroRNA-181b expression in prostate cancer transfection into the prostate cancer PC-3 cells. Down-regulation of miR-181b in the PC-3 cell induced apoptosis, inhibited proliferation, and depressed invasion of PC-3 cells in vitro. As miR-181b is overexpressed in prostate cancer, its down-regulation could have potential as gene therapy for prostate cancer by inducing apoptosis, inhibiting proliferation and depressing invasion by cancer cells.

Chidamide is a novel histone deacetylase (HDAC) inhibitor that increases the acetylation of histone H3 by inhibiting the activity of HDAC1 and HDAC2. We previously found that treatment of human colon cancer cells with chidamide led to cell apoptosis and cell cycle arrest at G0/1 phase in vitro. The present study extended the observations in vivo and explored the underlying molecular mechanisms. In nude mice bearing human colon cancer LoVo cell xenografts, chidamide alone or in combination with 5-flurouracil (5-Fu) reduced the expression of HDAC1 and HDAC2, accompanied with increased acetylation of histone H3. Chidamide alone inhibited the tumor growth and induce cell apoptosis in tumor-bearing mice. Combined treatment of chidamide with 5-Fu enhanced the anti-tumor activity of 5-Fu. Western blotting analysis showed that chidamide alone or in combination with 5-Fu upregulated the expressions of cleaved Caspase-3 and cleaved poly-ADP (adenosine diphosphate)-ribose polymerase (PARP). In addition, chidamide alone or in combination with 5-Fu increased the p53, phosphorylated-p53 (p-p53), p21 and γH2AX levels, but suppressed cyclin dependent kinase 4 (CDK4) expression in tumor cells. Chidamide alone or in combination with 5-Fu down regulated the expressions of p-AKT, p-mammalian target of rapamycin (mTOR), p-p70S6K, p-Raf, and p44/42 mitogen activated protein kinase (Erk1/2), indicating the blockage of these signaling pathways. The results demonstrated that chidamide alone or in combination with 5-Fu exerted anti-tumor activity in nude mice bearing human colon cancer LoVo cell xenografts, and several signaling pathways might be involved in the chidamide-induced tumor growth inhibition and tumor cell apoptosis.