Lack of BK virus DNA sequences in most transitional-cell carcinomas of the bladder

BK virus (BKV), a common human polyomavirus infection latent in the kidneys, can reactivate with immunosuppression to cause renal disease. Some have suggested that BKV may contribute to the development of bladder cancer, and BKV sequences have been reported from bladder tumors. To further examine the role of BKV in human bladder cancer, a series of bladder tumors was investigated for BKV genomic sequences. Fresh-frozen specimens from 76 transitional cell carcinoma tissues and 46 paired adjacent normal urothelial tissues archived at the H. Lee Moffitt Cancer Center were studied. All tissues were histopathologically reviewed. DNA extracted from the tissues was tested by quantitative real-time polymerase chain reaction (QPCR) assays to detect BKV DNA sequences in the VP1 coding region. Amplification of ERV-3 was conducted separately to quantify cell copy number. Conventional PCR targeting the BKV T-antigen (T-Ag) coding region and immunohistochemistry for BKV T-Ag were also conducted on all tissues that tested positive for BKV by QPCR. Seventy-three bladder tumors yielded ≥3,000 copies of ERV-3, 4 (5.5%) of which tested positive for BKV with average copy numbers of 7.9,15.8, 0.4 and 0.3 per 1,000 cells. Paired normal tissue was available for 2 of these BKV-positive tumors, 1 of which was BKV-positive (14.6 copies/1,000 cells). No other normal tissues were BKV-positive by QPCR. The 6 BKV-positive tissues by QPCR were also positive by conventional PCR, but all stained negative for BKV T-Ag by immunohistochemistry. BKV is unlikely to be involved in the etiology of most bladder tumors.