ESPE Abstracts

Introduction: Over-production of androgens is linked to prostate cancer (PCa) in men and polycystic ovary syndrome (PCOS) in women. CYP17A1 produces dehydroepiandrosterone (DHEA), the precursor for androgens, via its 17,20 lyase activity. CYP17A1 lyase activity is regulated by the amount of P450 reductase for electron transfer; the presence of cytochrome b5; and protein phosphorylation. High androgen levels were linked to the phosphorylation of CYP17A1 protein through an unknown signaling pathway. Regulation of CYP17A1 activity via post-translational mechanisms can be used to specifically inhibit its lyase activity.

Aims: To study changes in CYP17A1 lyase activity via selective regulation of protein phosphorylation.

Methods: We analyzed transcriptomic databases to identify differentially expressed genes in PCa and PCOS. Then, a pathway analysis was performed to outline the links between genes differentially expressed in hyperandrogenic states. Human adenocarcinoma, NCI H295R cells were transfected with a selected number of cDNA for kinases and phosphatases. CYP17A1 lyase activity was determined using a tritiated water release assay. Functional assays were also performed in cells treated with kinase and phosphatase inhibitors to determine their impact on CYP17A1 activities.

Results: A significant decrease in DHEA production was observed in cells overexpressing protein phosphatase (PPP) 2CA, glycogen synthase kinase 3 (GSK3), and dual-specificity phosphatase 6 and 10 (DUSP6/10). However, there was no change in the activity with PPP1CB. An inhibitor of polo-like kinase 1 (PLK1) specifically altered the lyase activity of CYP17A1. Protein-protein interaction database (STRING) search revealed that PPP2CA indirectly interacts with ROCK1 and PLK1 which are predicted to be involved in the signaling pathway leading to phosphorylation of CYP17A1.

Discussion: The dynamics between phosphorylated and dephosphorylated states of proteins vary in the cell. The change in the lyase activity of CYP17A1 shows a dependence on the expression of different kinases and phosphatases. We showed that signaling events can regulate CYP17A1 lyase activity either directly or indirectly through protein-protein interactions. Further analysis will establish whether PPP2CA, ROCK1, or PLK1 directly or indirectly interacts with CYP17A1.

Conclusion: Identification of missing links in the signaling pathways will help us understand mechanisms involved in the regulation of CYP17A1 activity during adrenarche as well as tumor progression in PCa. Selective inhibition of DHEA production by CYP17A1 via targeting phosphorylation mechanisms can be used for the development of drugs against PCa and PCOS with better efficacy and lesser side effects.