Novel Techniques to Target Androgen Signalling in Prostate Cancer

Prostate cancer (PCa) is currently the second highest cause of male cancer related death in the UK. The majority of aggressive cases of PCa spread outside of the organ to areas such as the bone where it becomes difficult to treat. Current treatment options focus on targeting androgens, the male sex hormones. Reducing the levels or activity of androgens can shrink tumours significantly, however resistance is inevitable. Multiple mechanisms of resistance have been described, but often the tumours appear to remain dependent upon androgen signalling for growth. In these cases, a novel therapeutic approach is required. This project aimed to develop novel methods to target the androgen signalling axis. Specifically, this project aimed to identify target key metabolic proteins driving PCa growth and to design DNAzymes (single stranded antisense molecules constructed of DNA) to down-regulate androgen receptor (AR) expression. We identified a DNAzyme, AM-3 that can degrade AR RNA and inhibit the proliferation of the LNCaP PCa cell line. A program was also developed by our collaborator, Dr Antonio Marco that could predict the efficiency of DNAzymes based on their target RNA. We demonstrated that DNAzymes generated by the program are more efficient compared to a published DNAzyme (DT99), known to cleave the same RNA. We have also looked to expand on the knowledge gained by previous studies demonstrating that the AR regulates multiple metabolic enzymes to promote PCa growth. Hence an siRNA screen targeting 237 different genes involved in metabolism and cell traffic was performed in order to identify novel metabolic targets to inhibit PCa growth. LNCaP cells were transfected with the siRNAs and proliferation measured via crystal violet assays. A total of 15 potential target genes reduced LNCaP proliferation by more than 75%. The screen identified several previously characterized targets such as COX-2 and FASN, as well as novel targets AZIN2, STX8 and ALAS2 that have not been associated with PCa previously.