Real-time PCR measures Epstein-Barr Virus DNA in archival breast adenocarcinomas

The role of Epstein-Barr Virus (EBV) in breast cancer pathogenesis remains controversial. Fifty-five cases of paraffin-embedded, formalin-fixed invasive breast cancer were screened for the presence of EBV using quantitative polymerase chain reaction (PCR) directed at five different targets within the EBV genome (BamH1W, LMP1, EBNA1, LMP2, and BZLF1 regions). In four tumors (7%), low level EBV DNA was detected by at least one of the assays, with levels of up to 11 copies of EBV DNA per 100,000 cells. Immunohistochemisty for viral BMRF1 and BZLF1 and in situ hybridization for lytic gene transcripts showed no evidence of replicative EBV gene expression. Lymphocytes and malignant cells were also negative for latent infection by EBER in situ hybridization. Laser capture microdissection followed by quantitative real-time PCR was not useful in localizing EBV DNA to malignant cells or bystander lymphocytes. In conclusion, EBV DNA is detectable in a fraction of breast cancer specimens using real-time PCR as a screening tool, albeit at quite low levels, which suggests that only rare cells are infected. The low levels probably confounded our ability to localize the virus to particular cell types or to characterize viral gene expression.