In this study, we screened 113 gastric adenocarcinomas from low- and high-incidence regions (United States and Central America) for the presence of EBV using a battery quantitative real-time PCR (Q-PCR) assays targeting disparate segments of the EBV genome (BamH1W, EBNA1, LMP1, LMP2, BZLF1, EBER1) and histochemical stains targeting EBV-encoded RNA (EBER), the latent proteins LMP1 and LMP2, and the lytic proteins BMRF1 and BZLF1.
Because BARF1 exerts immortalizing effects on human epithelial cells in vitro and EBV-carrying gastric adenocarcinomas lack the expression of LMP1, the BARF1 gene might act as the viral oncogene in EBV-carrying gastric carcinomas.
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.
To better understand the tumorigenic role of this LMP1 variant, we used PCR and sequencing to examine the LMP1 gene in 38 EBV-associated carcinomas (EBV-CAs) occurring in various organs (6 lung, 10 salivary gland, 5 sino-nasal, 16 gastric and 1 metastatic NPC), 55 reactive lymphoid tissues from tonsils (TON) and 67 EBV-negative tumours in various organs (22 adenolymphoma of salivary gland, 14 gastric and 31 colonic adenocarcinomas), where the virus was demonstrated in lymphocytes.