CDC91L1 (PIG-U) mRNA expression in urothelial cell carcinomas

CDC91L1 (PIG-U) was recently discovered as a new oncogene in human bladder cancer and showed mRNA overexpression in 36% of primary bladder tumor tissues compared to normal urothelium. We further investigated CDC91L1 mRNA expression in 8 bladder cancer cell lines, 14 normal bladder tissues and 42 urothelial cell carcinomas by real-time quantitative PCR. The prognostic value of CDC91L1 mRNA expression was also investigated. Surprisingly, only one (2.4%) tumor tissue showed overexpression compared to normal urothelium. No significant relationship of CDC91L1 mRNA expression with increasing pathologic stage (p = 0.962) or grade (p = 0.557) was observed. Median normalized CDC91L1 mRNA expression values were 0.19 for superficial tumors (n = 21) and 0.18 for invasive tumors (n = 21). Grade I, grade II and grade III tumors had median normalized expression values of 0.26, 0.18 and 0.33, respectively. CDC91L1 mRNA expression level was not indicative of early tumor recurrence (log rank p = 0.1629), tumor progression (log rank p = 0.9307) or overall and disease-specific survival (log rank p = 0.9193 and 0.4710, respectively). Our results suggest, in contrast to those of Guo et al. (Nat Med 2004;10:374-81), that the oncogene CDC91L1 is not overexpressed at the mRNA level in urothelial cell carcinomas and cannot be used to predict the course of the disease.