Association of Epstein-Barr virus infection with p53 protein accumulation but not bcl-2 protein in nasopharyngeal carcinoma

Abstract

Aims: The aim of this study was to investigate the association of Epstein-Barr virus (EBV) infection with status of p53 protein expression in nasopharyngeal carcinoma (NPC). The expression of EBV gene and gene product, p53 protein and bcl-2 protein in NPC was histopathologically studied.

Methods and results: In-situ hybridization using oligonucleotide probe to EBV-encoded small RNAs (EBERs) and immunohistochemistry using monoclonal antibodies against EBV latent membrane protein 1 (LMP1), p53 protein and bcl-2 proteins were performed in 56 primary NPCs. EBERs were detected in 46 (82%) cases and LMP1 in 17 (30%) cases. While 30 of 32 (94%) cases in differentiated nonkeratinizing carcinoma (NKC, WHO type 2) and 16 of 17 (94%) cases in undifferentiated carcinoma (UC, WHO type 3) showed EBERs expression, neither five cases of keratinizing squamous cell carcinoma (KSCC, WHO type 1) nor two cases of adenocarcinoma showed EBERs. bcl-2 protein was detected in 50 (89%) cases, but its expression did not depend on expression of LMP1. p53 protein was detected in 31 (55%) cases, and there was a correlation between expression of EBERs and p53 protein (P < 0.05) but not between LMP1 and p53 protein.

Conclusion: In this study, close association of NKC and UC but not KSCC with the latent infection with EBV was demonstrated. The induction of bcl-2 protein by LMP1, as shown in vitro, was not demonstrated. The association between overexpression of p53 protein and the presence of EBV suggests that some EBV-encoded protein, which may be different from LMP1, may play a role for nuclear accumulation of p53 protein.