321 ANTISENSE INHIBITOR TARGETING FULL LENGTH ANDROGEN RECEPTOR AND ITS SPLICE VARIANTS SUPPRESSES MDV3100 RESISTANT PROSTATE CANCER CELL GROWTH

Abstract

in different cancer types. We previously found that miR-125b directly targets p53, Bak1 and Puma, and promoted prostatic tumor growth in both intact and castrated mice. In this study, we further underline the clinical importance of miR-125b by detecting miR-125b levels in prostate cancer (CaP) specimens. In addition, we conducted animal experiments to determine whether miR-125b has potential as a therapeutic target for treatment of CaP. METHODS: For detection of miR-125b expression, total RNA was isolated from cancer cell-enriched, fresh-frozen CaP tissues, as well as fresh-frozen BPH specimens, using TRIzol reagent. The miR125b level was measured using qPCR. Animal experiments were performed according to the protocols approved by the Animal Care and Use Committee at UCD, CA USA. Male nude mice implanted with testosterone pellets were inoculated s.c with CWR22 CaP cell suspensions and then treated with polyethylenimines (PEI)-complexed antimiR-125b (PEI-anti-miR-125b) or PEI-anti-miR-125b plus Taxol. PEI can form complexes with miRNA, increase internalization and facilitate miRNA release into cytoplasm. RESULTS: 133 prostate specimens (46 BPHs and 87 CaPs) were analyzed for their expression of miR-125b. The average miR125b level was 3.0-fold greater in CaPs than in BPHs. In 42 CaPs having Gleason score available, the miR-125 levels correlate with Gleason scores (103 18 relative fold in Gleason score 5-6 vs 160 16 in Gleason score 7-10, p 0.03), suggesting that miR-125b contributes to pathological progression of CaP. In animal studies, mice were treated with PEI-anti-miR-125b (10 g/day, thrice a week for 4 weeks) or PEI-anti-miRNA control, and significant tumor-inhibitory effects was observed in anti-miR-125b treatment group compared to control group. In addition, mice bearing CWR22 tumors were treated with PEI-antimiR-125b plus Paclitaxel (20 mg/kg/week for 4 weeks). It was found that anti-miR-125b significantly increased the therapeutic efficiency of Taxol. CONCLUSIONS: Data from qPCR provide evidence that dysregulation of miR-125b is common in CaP patients and the levels of miR-125b are correlated with pathological progression of CaP. Additionally, results from animal studies show that anti-miR-125b inhibited growth of CWR22 tumors and sensitized CaP cells to Taxol, suggesting that miR-125b can be used as a target for improved CaP treatment.