IMMUNOHISTOCHEMICAL EXPRESSION OF RETINOBLASTOMA AND P53 TUMOR-SUPPRESSOR GENES IN PROSTATIC INTRAEPITHELIAL NEOPLASIA - COMPARISON WITH PROSTATIC ADENOCARCINOMA AND BENIGN PROSTATE

Mutational alterations involving the p53 and retinoblastoma (RB) tumor suppressor genes are implicated in the oncogenesis of a variety of tu mors, Their role in the pathogenesis of prostatic adenocarcinoma remai ns to be fully elucidated, and their detection in high-grade prostatic intraepithelial neoplasia (HG-PIN) has not been closely examined. We studied the immunohistochemical expression of RB and p53 proteins in H G-PIN, benign prostate, and prostatic adenocarcinoma from 25 radical p rostatectomy specimens, Formalin-fixed, paraffin-embedded tissue secti ons pretreated with antigen retrieval in citrate buffer were stained w ith anti-RB antibody RB-WL-1 and anti-p53 antibody DO-7. RB immunoreac tivity was present in all of the cases in the foci of HG-PIN, benign p rostate, and prostatic adenocarcinoma. Mutant p53 protein was detected in 56% of HG-PIN, 72% of prostatic adenocarcinomas, and 20% of benign prostatic glands. A multivariate analysis of variance showed an overa ll difference in p53 immunoreactivity between HG-PIN, benign prostate, and prostatic adenocarcinoma (P < .001), There was a statistically si gnificant difference between immunoreactivity of the benign prostate a nd of HG-PIN (P < .001) and between the immunoreactivity of benign pro state and prostatic adenocarcinoma (P < .001), The immunoreactivities of HG-PIN and prostatic adenocarcinoma were not statistically differen t (P = .3). These data suggest that RB loss might not play a role in i nitiation of all cases of prostatic adenocarcinoma The p53 immunoreact ivity in HG-PIN was significantly different from that found in benign prostate and was similar to that of prostatic adenocarcinoma. This is in keeping with the putative premalignant character of HG-PIN.