Polyphenon E Alters p53 and p73 Gene Expression
Authors: Cordova Ricardo A. , Carastro L. Michael , Barboto Daniel E. , Declet‐Bauzo Ricardo A. , Conelly Zachary M. , Park Jong Y 
Published: November 2023

Prostate cancer (PCa) is the most common malignancy among men in the USA. Polyphenon E (PolyE) is a standardized blend of polyphenols found in green tea extract, which has been shown to have chemoprevention value in PCa models, but the molecular mechanism(s) have not been elucidated. It has been reported that polyphenols from green tea alter the expression levels of p53 and p73 genes. The p53 tumor suppressor family of genes includes p53, p63 and p73. All p53 family members have both distal and proximal transcription initiation sites in their gene promoters, P1 and P2, from which mRNA isoforms are transcribed. The p73 gene produces two mRNAs from its P1 and P2 initiation sites, encoding TAp73 and ΔNp73 isoforms, respectively. TAp73 and DNp73 mRNAs each encode a different protein isoform which differ in their N‐termini. TAp73 isoforms include the full‐length N‐terminal sequence and are transcriptionally active. DNp73 isoforms lack the N‐terminal trans‐activation domain and are dominate negative. ΔNp73 isoforms are able to form tetramers with TAp73, as well as p53, but are not capable of trans‐activating transcription of p73‐ or p53‐target genes. We hypothesize that exposure to PolyE induces changes in the gene expression levels of p53 family members. Our goal for this study is to assess the effect of varied concentrations of PolyE on overall p53 mRNA levels, overall p73 mRNA levels, as well as TAp73/DNp73 mRNA isoform ratios using three human PCa cell lines (DU145, LNCaP and PC‐3) and a non‐cancerous primary prostate cell line. Cultured cells were treated with varied concentrations of PolyE for 24 hours. Cellular RNAs were converted into cDNA used in validated TaqMan qRT‐PCR assays (StepOneTM RT‐PCR System). RT‐PCR data was analyzed using StepOneTM software and the DDCt method. Our qRT‐PCR data from PolyE treated PC‐3, DU145, and primary prostate cells are consistent with decreased total p73 mRNA levels (0.89, 0.35, and 0.01‐fold) at the highest PolyE concentration tested. However, p73 mRNA levels (1.02‐fold) were unchanged at all PolyE concentrations tested with LNCaP cells. The TAp73/DNp73 ratios of mRNA expression changes decreased for PC‐3 (0.701‐fold) and DU‐145 (0.38‐fold), but increased (1.95‐ and 1.36‐fold, respectively) in LNCaP and primary prostate cells at the highest PolyE concentration tested. The p53 mRNA levels for DU145 increased (2.09‐fold) and for primary prostate cells decreased (0.0402‐fold) as PolyE treatment concentration increased. In conclusion, some notable patterns emerged from our data: PolyE treatment of LNCaP and primary prostate cell lines, both which possess normal p53 function, resulted in harbor higher TAp73/DNp73 isoform ratios, but conversely PC‐3 and DU 145 cell lines, which have lost normal p53 function, resulted in decreased TAp73/DNp73 isoform ratios. Furthermore, when normal primary prostate cells were treated with PolyE, overall p53 and p73 levels decreased drastically. These data could provide insights into the PolyE molecular mechanisms of observed prostate cancer risk reduction.