Cell-cycle regulators, bcl-2 and NF-κB in Epstein-Barr virus-positive gastric carcinomas

Abstract

The mechanism by which Epstein-Barr virus (EBV) contributes to the carcinogenesis of gastric mucosa remains unanswered. In this study, the role of cell-cycle regulators (p53, p21, p27, p16, cyclin D1, Rb), bcl-2 and NF-kappaB p65 (Rel A) was evaluated. Immunohistochemistry for these proteins was performed in EBV-positive (n=55) and EBV-negative gastric carcinomas (n=72). The bcl-2 protein by western blot and EBV transcripts using RT-PCR were studied in cell lines. The p27 loss, p16 loss, cyclin D1 expression and NF-kappaB nuclear positivity were more frequent in EBV-positive gastric carcinomas than those in EBV-negative gastric carcinomas, while p53 overexpression seldom occurred in EBV-positive carcinomas (p<0.001). EBV-positive gastric carcinoma showed unique p53 immunostaining (heterogeneous, weak to moderate, focal staining), and rare bcl-2 positivity (1 case). Western blot showed bcl-2 to be irrespective of EBV status in stomach cancer cell lines. However, bcl-2 was highly expressed in EBV-positive lymphoma or EBV-positive lymphoblastoid cell lines. The BARF1 transcript was confirmed in both EBV-positive stomach cancer and EBV-positive lymphoma, suggesting tissue type-specific bcl-2 activation by BARF1. The pathological tumor stage was the only independent prognostic factor. A small size of tumor, p16 preservation and NF-kappaB nuclear positivity were associated with a good prognosis in univariate analysis (p<0.05). p27, p16, cyclin D1 and NF-kappaB may be associated with oncogenesis in EBV-positive gastric carcinomas. EBV-positive gastric carcinomas showed infrequent p53 overexpression, wild-type p53 stabilization and rare bcl-2 involvement. The characteristic expression of proteins may relate to both EBV and tissue type.