Identification of miR-205 targets using an RIP-Chip assay with AGO2 antibody

In this study, the prognostic properties of miR-205 expression levels are investigated in a well-documented prostate cancer cohort. We show that miR-205 is correlated to shortened overall survival, significantly dividing the PCa patients into high and low risk groups. Furthermore, miR-205 is shown to inversely correlate to occurrence of metastases. In situ hybridization is also performed, demonstrating high miR-205 expression in the basal cells of benign prostate tissue glands. A RIP-Chip assay using an AGO2 antibody was implemented and the miR-205 targets identified were found to be enriched in MAPK/ERK, Toll-like receptor and IL-6 signaling pathways. We also found individual targets involved in cancer and androgen receptor signaling. Ectopic levels of miR-205 are shown to decrease the level of androgen receptor both at the mRNA and protein levels in prostate cancer cell lines. This is further corroborated in the prostate cancer cohort were miR-205 expression levels in the prostatic tissues are found to inversely correlate to assessment of androgen receptor (AR) immunostaining and to serum levels of PSA, a protein regulated by AR signaling. The level of miR-205 is also found to be significantly lower in castration resistant prostate cancer patients than in hormone naïve patients. Our data indicates that miR-205 is regulated by androgens and act by different mechanisms in androgen depleted settings, e.g. giving opposite effects on adhesion. Taken together these findings imply that miR-205 might have therapeutic potential especially for the castration resistant and currently untreatable form of prostate cancer. Experiment done with biological triplicates. Three with miR-205 ectopic expression and three with negative control mimic ectopic expression. Followed by a RIP-Chip, ending with mRNA extraction and gene expression array.