Epstein-Barr virus (EBV) may be a cofactor in the development of different malignancies, including several types of carcinomas. We demonstrated the presence of EBV in human breast cancers. We detected the EBV genome by PCR in 51% of the tumor biopsies. In 90% of the cases studied, the virus was not detected in healthy tissue. The presence of the EBV genome in breast tumors was confirmed by Southern-blot analysis. The EBV latent protein EBNA-1 was observed in a fraction (5-30%) of tumor epithelial cells. Expression of the EBV genes BNLF1 and BARF0 will be reported. A statistical relationship was established between the presence of EBV and several poor prognostic factors. EBV may be a cofactor in the development of a subset of breast cancers.

Latently EBV infected breast undifferentiated human epithelial cell line, MDA-MB-231, was obtained and injected into nude mice. Tumors were obtained in which EBV persists. The persistence of EBV in nude mice tumors, in the absence of any selection, suggests that mammary epithelial cells could be a natural host for EBV. These models will be used for the elaboration of specific therapeutic targets. Normal breast mammary epithelial cells are now being infected by EBV in order to investigate the oncogenic potential of EBV in those epithelial cells.