Semi-Quantitative Analyses of Protein Expression in Polyphenon E-Treated PC-3 Cells

In the United States, approximately 1 in 9 men will be diagnosed with prostate cancer (PCa) during their lifetime. Furthermore, PCa is the second leading cause of malignant‐related death in the United States. Polyphenon E (Poly E) is a standardized, caffeine‐free, green tea extract reported to inhibit the progression of PCa. The chemopreventive mechanisms of action for Poly E are not fully understood. In an attempt to further understand the role of Poly E in PCa, we sought to identify its potential molecular targets. The aim of this study was to detect changes in protein expression levels in Poly E‐treated PC‐3 cells. We previously obtained DNA microarray and qRT‐PCR data from PC‐3 cells treated with increasing concentrations of Poly E (100, 200, 300 mg/L) to identify potential molecular targets. We extracted total cellular protein from Poly‐E treated PC‐3 cells and performed immunoblot analysis for RGCC, ATM, RB1, and beta‐tubulin. Immunoblotting data was used in semi‐quantitation analyses of protein expression to determine fold changes in protein levels compared to the reference sample (untreated control). Immunoblotting data was normalized against beta‐actin protein loading control. Data obtained from semi‐quantification of protein levels for selected genes was compared to qRT‐PCR data obtained previously. RB1 protein expression levels for exhibited dose‐dependent decreases upon increasing Poly E treatment. At the highest concentration of Poly E treatment (300 mg/L), RB1 protein expression decreased by 44% compared to untreated cells, and was consistent with qRT‐PCR data. RGCC protein expression levels did not exhibit dose dependency, with 1.2 and 1.1‐fold increases in protein expression upon 200 and 300 mg/L Poly E treatment, respectively, which was consistent with observed trends for the corresponding qRT‐PCR data. A dose‐dependent decrease in ATM protein expression was observed for the Poly E‐treated PC‐3 cells. At the highest concentration of Poly E treatment (300 mg/L), ATM protein expression decreased 2‐fold. However, qRT‐PCR data obtained for ATM indicated marginal changes in gene expression in Poly E‐treated PC‐3 cells. Our semi‐quantitative immunoblotting data for RGCC and RB1 protein expression in Poly E‐treated PC‐3 cells was generally consistent with our qRT‐PCR data. However, the dose dependent decreased ATM protein expression observed did not comport with the lack of gene expression level changes observed by qRT‐PCR. Support or Funding Information This work was supported by a University of Tampa David Delo Research Professor Grant (to: L. M. C.). This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal .