Influence of chronic inflammation on Bcl-2 and PCNA expression in prostate needle biopsy specimens

摘要

The association between inflammation and cancer has been established in certain forms of human malignancies; however, its role in prostate cancer remains unclear. The present study investigates a possible association between chronic inflammation and the development of epithelial neoplasia in the prostate. Needle biopsy specimens were obtained from patients with serum prostate-specific antigen levels >4 ng/ml, evaluated for morphological findings, and immunostained for Bcl-2 and proliferating cell nuclear antigen (PCNA). Bcl-2 is a survival protein that appears to lie at a nodal point in pathways involved in cell survival, carcinogenesis, and development of therapeutic resistance in certain cancer types. Similarly, PCNA is a critical protein for DNA replication, repair of DNA damage, chromatin structure maintenance, chromosome segregation and cell-cycle progression. The association between these two proteins was examined in prostate tissues with and without chronic inflammation, as well as tissues with and without evidence of neoplastic changes. Of the 106 needle biopsies examined, 18% exhibited atrophy with inflammation. Proliferative inflammatory atrophy/post-atrophic hyperplasia were observed in 42%, high-grade prostatic intraepithelial neoplasia (HGPIN) in 8%, prostatic adenocarcinoma in 11%, and 2% had atypical acinar proliferation suspicious for malignancy. A total of 36 specimens were stained for Bcl-2 and PCNA. Bcl-2 was expressed widely in inflammatory and epithelial tissue; however, more intense expression was observed in the areas of chronic inflammation, predominantly in infiltrating immune cells. The highest proliferation index was observed in the epithelia of HGPIN and cancer. An inverse correlation between the expression of Bcl-2 and the expression of PCNA was observed in the epithelium. The areas of chronic inflammation were associated with increased Bcl-2 expression, whereas the highly proliferative epithelium minimally expressed Bcl-2. These results suggest that Bcl-2 alters the phenotype of particular epithelial cells with a gain in neoplastic characteristics, leading to a likely precursor that may later progress into HGPIN and cancer.