The Role of WFDC1/ps20 in Prostate Cancer

Abstract

In prostate cancer (PCa), stromal tissues co-evolve through reciprocal interactions with the tumour to support tumour growth and suppress the immune response. WFDC1/ps20 is a secreted whey acid protein (WAP) four-disulphide core (WFDC) family member highly expressed within the prostate stroma. Ps20 expression has been frequently observed to be down-regulated or lost in cancers including in prostate cancer, and numerous lines of evidence suggest that ps20 has intrinsic growth suppressive function in numerous tumour model systems. However, ps20 remains biochemically uncharacterised and the mechanisms by which it functions are unknown.

WFDC1/ps20 is expressed in numerous mRNA and protein isoforms some of which result from proteolytic cleavage. These post-translational modifications affect the ability of the protein to inhibit the proliferation of PCa cells. We demonstrated that ps20 undergoes oligomerisation by transglutaminase, and crosslinking to fibronectin. We show that ps20 is cleaved by cathepsin L, which while failing to abrogate function of the protein, does liberate cross-linked ps20 from solid phase fibronectin. We show that ps20 binds to glycosaminoglycans (GAG) and interacts with cell surfaces in a GAG dependent manner.

To further investigate the cellular effects of ps20 we overexpressed ps20 in PCa cell lines. Transgenic overexpression of WFDC1/ps20 reduced proliferation in WPMY-1 cells, and conditioned media (CM) from these cells had potent pro-apoptotic effects on a range of PCa cell lines. Whole genome differential transcriptome analysis of WPMY-1-EV v WPMY-1-ps20FL/WPMY-1-ps20TR cells identified numerous factors, including IL-8, IL-32, COX2, and SerpinF1 to be upregulated in WPMY-1 cells. Addition of a COX2 inhibitor reversed the suppressive effect of WPMY-1-ps20 CM, suggesting that expression of ps20 in the prostate stroma can regulate growth of epithelial and other tissues through the prostaglandin synthase pathway.

Lastly, using ps20 overexpression in WPMY-1 prostate stromal cells, we demonstrated that CM from ps20 expressing cells inhibits proliferation of CD4 and CD8 T cells. Using depletion of ps20 from CM we show that suppression is indirectly mediated. We show that ps20 expression in WPMY-1 cell CM inhibits both anti-CD3/28 and IL-7/15 dependent T cell. However no effect on the secretion of IFNγ or expression of common T cell activation markers is observed. We demonstrate that the suppression of T cell proliferation is partly due to enhanced COX-2 activity.

Date of Award	2015
Original language	English
Awarding Institution	King's College London
Supervisor	Prokar Dasgupta (Supervisor), Christine Galustian (Supervisor) & Annapurna Vyakarnam (Supervisor)