Infiltration of Epstein-Barr virus-harboring lymphocytes occurs in a large subset of bladder cancers

Objective: Epstein-Barr virus (EBV) has been implicated in the genesis of a variety of human cancers. We aimed to confirm the presence and define the role of EBV in bladder cancer. Methods: A total of 39 bladder cancer specimens were analyzed. Ten urinary bladder tissues obtained at autopsy were used as a normal control. EBV-encoded RNA (EBER) was evaluated by in situ hybridization (ISH). Frozen material available from 18 EBER-positive cases was analyzed by using reverse transcription-polymerase chain reaction for BZLF1, an early lytic gene product. The expression of CD20, CD3, ZEBRA (BZLF1 product) and transforming growth factor beta 1 (TGF beta-1) was assessed using an immunohistochemical technique. Results: Infiltration of EBER-expressing lymphocytes was detected in 26 of 39 bladder cancer cases (66.7%). A small fraction of the tumor cells as well as the infiltrating lymphocytes were positive in two cases. All normal urinary bladder specimens showed negative results. The incidence of EBV-positive lymphocyte infiltration was significantly higher for advanced stage cancers than those in earlier stages (Ta-152% vs T2-4 93%, P = 0.013). The presence of BZLF1 mRNA was demonstrated in seven out of the 18 EBER-positive cases. Conclusions: Infiltration of EBV-harboring lymphocytes occurs in a large subset of bladder cancers cases. It is more frequently associated with advanced stages. EBV infection in tumor cells is very limited. Our findings suggest that EBV-positive lymphocytes might play a role in bladder cancer progression.