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MicroRNA in development and progression of prostate cancer

Final Activity Report Summary - MIRNAPROSTATECANCER (MicroRNA in development and progression of prostate cancer)

This project studied the miRNA expression in 27 primary prostate tumours, 5 normal prostates and 9 prostate cell lines by miRNA micro array screening. They gathered results showing that miR-16 is down regulated in prostate cancer. Further, deletion of 13q14, where one of the two the miR-16 encoding gene is located, is frequently deleted in prostate cancer (30-70%); however, no reasonable candidate has yet been identified in this region. The project optimised the in situ hybridisation on prostate formalin fixed paraffin embedded specimens for miR-16 and preliminary observations indicates that miR-16 is expressed in luminal epithelial cells and down regulated in cancerous tissues. They found that inhibitors of miR-16 in Du145 cells increase the proliferation rate by 254% (p=0.0017) in vitro, and when ectopically expressing miR-16 in PC3 cells (with low levels of miR-16) the proliferation rate decreases. In addition, we have also seen an increase of apoptosis when miR-16 is overexpressed in PC3 cells with 128-152% depending on method of analysis.

Using in silico analyses miR-16 was predicted to target the transcription factor E2F3 that is involved in cell cycle regulation, and has been shown to induce increased proliferation in prostate cancer cells5. It is also a prostate cancer marker, upregulated in 68% of prostate cancers, and correlated with poor survival. The project confirmed that miR-16 has a regulatory effect on E2F3 in vitro; the E2F3 levels are abolished when ectopically expressing miR-16, and when blocking miR-16 in Du145 the E2F3 levels increase with 240%. The Luciferase assay showed that miR-16 binds to the E2F3 3'utr, and that it is corresponding to increased levels of miR-16. Previously, we have found that the over expression of E2F3 protein in prostate cancer cannot been linked to DNA amplification of the E2F3 encoding gene or mRNA over expression, indicating that the deregulation of E2F3 might be caused by miRNAs. The protein levels of E2F3 in different prostate cell lines show an almost perfect negative correlation to the level of miR-16 detected by qRT-PCR Taqman. Hence, these results nicely ties in with this theory.