Comparative analysis of the expression of the Epstein-Barr virus (EBV) anti-apoptotic gene BHRF1 in nasopharyngeal carcinoma and EBV-related lymphoiddiseases

Epstein-Barr virus (EBV) has been identified in a wide range of neoplastic and non-neoplastic disorders. The EBV open reading frame BHRF1 encodes a pr otein with partial sequence and functional homology to the anti-apoptotic o ncoprotein Bcl-2 and may therefore have a role in the proliferation of EBV positive cells. We have developed a rat monoclonal antibody against pBHRF1, which can detect BHRF1 in paraffin sections. While a number of mutant vers ions of BHRF1 were recognised, the monoclonal did not detect the BHRF1 homo logue encoded by Herpesvirus papio or two mutants with deletions in the BH2 region. This novel rat monoclonal antibody (6A9) was used to examine tissu e sections from 39 cases of non-keratinising undifferentiated nasopharyngea l carcinoma (NPC), 6 cases of metastatic NPC, 7 cases of EBV-positive NPC w ith squamous differentiation from Chinese patients, 15 cases of EBV-positiv e post-transplant lymphoproliferative disorder (PTLD), 6 EBV-containing lym phoblastoid cell lines, and 2 cases of oral hairy leukoplakia (OHL). In 11 cases of undifferentiated NPC, RT-PCR data were available for comparison wi th the immunohistochemistry. Both cases of OHL and two cases of LCL were po sitive for BHRF1 but none of the PTLD showed positive staining. All cases o f undifferentiated NPC were positive for Bcl-2 but only one BHRF1 positive cell was identified in 1 of 39 cases of primary undifferentiated NPC. The 6 A9 antibody produced less background staining and no nuclear positivity com pared with the commercially available mouse monoclonal 5B11. It is conclude d that BHRF1 can not be detected by immunohistochemistry in NPC and therefo re it appears not to play a significant anti-apoptotic role in the progress ion of this EBV-associated tumour. The 6A9 monoclonal appears to be superio r to 5B11 for the detection of pBHRF1 in tissue sections. (C) 2001 Wiley-Li ss, Inc.