The current standard treatment of prostate cancer by androgen deprivation therapy involves using drugs such as bicalutamide (Casodex) to antagonistically block androgen receptors that are normally present within prostate cells. Usually, the therapy is successful in the short run at limiting the growth of prostate cancer. However, in virtually all cases tumors begin to grow aggressively again after several months of treatment and new therapies must be started. The mechanism by which these prostate cells transform from androgen sensitive to androgen independent and anti-androgen resistant is unclear. In this study, we investigated the role of microRNAs, small 15 to 18 nucleotide regulatory RNAs, in regulating the desensitization of prostate cancer cells to the androgen receptor antagonist drug bicalutamide. In order to identify significant microRNAs, quantitative PCR was used to obtain genome-wide microRNA expression levels of 885 human microRNAs at different timepoints for androgen sensitive LNCaP cancer cells treated with bicalutamide and for untreated control cells in tissue culture. Analysis of microRNA expression by clustering analysis and by statistical comparisons of treatment groups resulted in identification of 28 microRNAs that have altered expression in the progression process. In silico target prediction analysis was performed with the microRNAs shown to have altered expression, and a group of genes predicted to be under microRNA regulatory control during cancer progression to resistance was identified. A microRNA expression profile can be useful in developing more effective prognostic and therapeutic tools for prostate cancer
