Higher viral load of BK polyomavirus in urothelial bladder tumors compared with nontumoral bladder tissues

Aim: This study examined BK polyomavirus (BKPyV) genome and viral load in urothelial bladder carcinoma (UBC) and nontumoral bladder tissues. Materials & methods: Quantitative real-time PCR was used to measure viral LT-Ag copy number per cell in 114 fresh-frozen bladder biopsy samples (61 UBC and 53 nontumoral tissue samples). Results: Patients with UBC had a significantly higher mean BKPyV LT-Ag DNA load than those without UBC. In multivariate logistic regression analysis, BKPyV LT-Ag copies/cell and smoking/illicit use of drugs were associated with bladder cancer. Receiver operating characteristic curve analysis identified bladder cancer risk at 0.1 copies/cell. Conclusion: This study found high BKPyV LT-Ag DNA copy numbers in most UBC samples, supporting the hypothesis that BKPyV induces UBC tumorigenesis.