Frequent Loss of pRb2/p130 in Human Ovarian Carcinoma

Abstract

Purpose: RB2/p130, a member of the retinoblastoma gene family, maps to human chromosome 16q12.2, a region in which deletions have been found in several human neoplasms including breast, prostatic, and ovarian carcinoma. We sought to evaluate pRb2/p130 protein expression and function in ovarian carcinoma. Experimental Design: pRb2/p130 expression was detected by immunohistochemical and Western blot analyses in 45 primary ovarian carcinoma samples. Results: Immunohistochemical analysis revealed loss or decrease of pRb2/p130 expression in 18 cases (40%). pRb2/ p130 expression was mostly nuclear and inversely correlated to the tumor grade (P < 0.05). Western blot analysis correlated with immunohistochemical expression. Reverse transcription-PCR followed by Southern blot analysis was performed on a representative set of 20 ovarian carcinomas. RB2/p130 mRNA levels were consistent with protein expression. We found a significant increase in the percentage of G1-phase-arrested cells in CAOV3 and A2780 ovarian carcinoma cell lines after transduction with an adenovirus carrying the RB2/ p130 gene (Ad-CMV-RB2/p130). Conclusions: These data indicate that loss or decrease of pRb2/p130 expression is a frequent event in ovarian carcinoma and is regulated mostly at the transcriptional level. Moreover, pRb2/p130 overexpression is able to arrest cell growth in ovarian carcinoma cells, suggesting the putative role of pRb2/p130 as a tumor suppressor in this malignancy.