Long Noncoding RNA MALAT-1 is a New Potential Therapeutic Target for Castration Resistant Prostate Cancer

Purpose: To understand the role of MALAT-1 in prostate cancer we evaluated its expression in prostate cancer tissues and cell lines. We also studied the therapeutic effects of MALAT-1 silencing on castration resistant prostate cancer cells in vitro and in vivo. Materials and Methods: Quantitative reverse transcriptase-polymerase chain reaction was used to detect MALAT-1 expression in prostate cancer tissues and cell lines. siRNA against MALAT-1 was designed and the silencing effect was examined by quantitative reverse transcriptase-polymerase chain reaction. The biological effects of MALAT-1 siRNA on cells were investigated by examining cell proliferation using a cell counting kit and cell colony assays as well as cell migration by in vitro scratch assay, cell invasion by Transwell (R) invasion assay and cell cycle by flow cytometry. We further investigated the effect of therapeutic siRNA targeting MALAT-1 on castration resistant prostate cancer in vivo. Results: MALAT-1 was up-regulated in human prostate cancer tissues and cell lines. Higher MALAT-1 expression correlated with high Gleason score, prostate specific antigen, tumor stage and castration resistant prostate cancer. MALAT-1 down-regulation by siRNA inhibited prostate cancer cell growth, invasion and migration, and induced castration resistant prostate cancer cell cycle arrest in the G0/G1 phases. Importantly, intratumor delivery of therapeutic siRNA targeting MALAT-1 elicited delayed tumor growth and reduced metastasis of prostate cancer xenografts in castrated male nude mice, followed by the concomitant prolongation of survival of tumor bearing mice. Conclusions: MALAT-1 may be needed to maintain prostate tumorigenicity and it is involved in prostate cancer progression. Thus, MALAT-1 may serve as a potential therapeutic target for castration resistant prostate cancer.