Abstract 3282: Does the catalytic activity of prostate-specific antigen (PSA) or kallikrein-related peptidase 2 (hK2) secreted by novel transgenic mice models critically influence development of prostate cancer or release of PSA or hK2 in blood

Abstract

Abstract INTRODUCTION AND OBJECTIVES Transcription of PSA and hK2 is governed by androgens, restricting high-level production to the prostate. Blood levels of PSA and hK2 are very strongly associated with risk and outcome of prostate cancer (PCa) in men not subject to PSA-based screening and genetic variation in or around genes encoding PSA or hK2 have also been associated with risk or outcome of prostate cancer. Functional orthologs to PSA or hK2 are absent in most mammals (including rodents) and present only in dogs and certain primates, which spontaneously develop PCa. Little is known of the role of PSA or hK2 in carcinogenesis or the mechanism of release of PSA in the blood, as prior investigations did not enable expression of functional, catalytic PSA. METHODS We generated a furin recognition site in proPSA through site-specific mutagenesis to enable the protease furin to convert proPSA to functional, catalytic PSA. A corresponding construct was also generated for hK2. We also generated a non-catalytic control through mutagenesis of 2/3 amino acid residues in the catalytic triad of PSA to abolish any catalytic function of PSA. Transgenic mice were generated by cloning either of these constructs downstream of a probasin promoter enabling abundant prostate-specific expression. Blood and prostate tissue samples of our PSA producing transgenic mice were evaluated in terms of catalytic function. RESULTS Catalytic PSA and hK2 and non catalytic PSA producing mice were generated successfully, and genotype was confirmed by PCR analysis. Specific hydrolytic activity was confirmed in prostate tissue harvested from transgenic mice. We found no macroscopic or histo-pathologic evidence of significant pathology in transgenic mice expressing either catalytic PSA or catalytic hK2. However, release of PSA in blood was associated with whether catalytic or non-catalytic PSA was expressed by the transgenic mice. Hence, detectable levels of PSA released in blood were found in a majority of male offspring (62/76) from two independent founder lines expressing functional (i.e. catalytic) PSA (81.5%). Despite similarly abundant secretion of PSA or hK2 from the mouse prostate, there was no detectable amount of PSA or hK2 released in blood from mice expressing non-catalytic PSA (0/71) or catalytic hK2 (0/59). CONCLUSIONS We have developed and validated novel models enabling over-expression of either catalytic or non-catalytic PSA in different cancer cell lines and transgenic mice. The current data from our unique transgenic mice models suggest that (a) abundant expression of catalytic PSA or hK2 does not result in any notable pathology in the mouse prostate, but that (b) release of detectable levels of PSA in blood may be contingent of the catalytic activity of PSA. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 3282. doi:1538-7445.AM2012-3282