Abstract 5306: Tissue-specific prostate specific antigen (PSA).

Abstract

Abstract We attempted to isolate and characterize PSA from prostate tissue. The aim was to isolate tissue-specific PSA and its initial characterization. This included: (i) determination of PSA molecular forms (free and complexed PSA), (ii) enzymatic activity, and its inhibition by metal ions, (iii) and their relative anti-angiogenic activity. Prostate, tumor and non-tumor, tissue was acquired under IRB approved protocol. PSA was isolated from prostate non-tumor (NT-PSA) and tumor tissue (T-PSA) and characterized using various chromatographic techniques including ligands such as Thiophilic gel, Concanavalin-A agarose, Protein-A agarose, and other lectins. The average NT-PSA concentration was 25±6.3ng PSA/μg of DNA (p=0.0001) and the average T-PSA concentration was 13±5.7ng PSA/μg of DNA (p=0.0001). On an average, tumor PSA (EA=29.64±11.34 p=0.0001)) had twice as much enzymatic activity as compared to non-tumor PSA (EA=13.29±3.300 p=0.001). The inhibition of enzymatic activity of PSA by metal ion (Zn2+)showed that seminal plasma-PSA (SP-PSA) and NT-PSA were inhibited to the same degree [85.3% and 87.0% respectively (p<0.05)]. However, the level of EA of T-PSA was significantly lower (52.4%) as compared to T-PSA. In regards to its molecular complexes, a higher ratio of free to complex-PSA (ACT and A2M) was obtained from non-tumor prostate tissue-PSA (1.51 p=0.0001) as compared to tumor prostate tissue-PSA (1.15 p=0.0001). Initial studies on the effect of SP-PSA on in vitro angiogenesis revealed a dose-dependent inhibitory effect (1μM, 5μM, 10μM concentrations) on the formation of tubular structures in HUVEC-Matrigel assay. The inhibitory effect of T-PSA & NT-PSA was examined and compared to the effect obtained from SP-PSA. Concentrations of 0.1μM, 1μM and 5μM gave similar levels of inhibition for SP-PSA, NT-PSA, and T-PSA (NT-PSA p-values for 1μM and 5μM: p=0.0057, p=0.0006, respectively; T-PSA p-values for 1μM and 5μM: p=0.0038, p=0.0002, respectively). At 0.1 μM concentration, both T-PSA and NT-PSA were not statistically different from control (p=0.3561 and p=0.2532, respectively). A 10μM concentration of both SP-PSA and NT-PSA displayed similar results (p=0.0001). When comparing the effects between NT-PSA and T-PSA, only 0.1μM concentration produced statistically significant results (p=0.0149; 1μM and 5μM: p=0.2301 and p=0.0752, respectively). We found that both NT-PSA and T-PSA also produced significant dose-dependent inhibition (1μM and 5μM NT-PSA and T-PSA (% inhibition): 76.21, 72.58, and 55.07, 54.98, respectively (p<0.05)). A larger sample size is needed to further assess the differences between the two groups. Our results provide some insight into the role of PSA in pathobiology of prostate cancer. PSA levels in prostate cancer tissue are lower as disease progresses suggesting that PSA has a role in prostate pathology. Citation Format: Srikant S. Chakravarthi, Kailash C. Chadha, Gary J. Smith. Tissue-specific prostate specific antigen (PSA). [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 5306. doi:10.1158/1538-7445.AM2013-5306