Absence of PIWIL2 (HILI) expression in human bladder cancer cell lines and tissues

Background: PIWIL2, a member of Argonaute family of proteins, is exclusively expressed in testis and functions in development and maintenance of germline stem cells. Recently, ectopic expression of PIWIL2 has been reported in a variety of human and mouse tumors. To investigate a potential involvement of PIWIL2 in human bladder cancer, we examined its expression in several human bladder cancer cell lines, normal uroepithelial cell cultures, and some bladder tissues. Methods: Relative expression of PIWIL2 was determined by real-time quantitative RT-PCR in fifteen bladder carcinoma cell lines, six normal uroepithelial cell cultures and seventy tissue specimens of tumor, tumor margins and morphologically normal tissues of bladder. Specific primers for PIWIL2, TBP and GAPDH (as two internal controls) were used for reverse transcription polymerase chain reaction technique. Results: Real-time qRT-PCR demonstrated high PIWIL2 expression in testis tissue, but at least 240-fold lower expression in all examined cell lines. The highest expression outside testis was observed in one of six primary cultures of normal uroepithelial cells, but even lower expression of PIWIL2 was detected in any of the examined tumor and non-tumor tissues. Conclusion: Lack of PIWIL2 expression in most tissues along with its aberrant expression in some tumors candidate the gene as an attractive tumor marker for some neoplasms. However, our study indicates that PIWIL2 does not play a role in carcinogenesis of human bladder carcinoma.