Absence of PIWIL2 (HILI) expression in human bladder cancer cell lines and tissues Parvaneh Nikpour a , Mehdi Forouzandeh-Moghaddam b , Seyed Amir-Mohsen Ziaee c , Olusola Y. Dokun d , Wolfgang Arthur Schulz d , Seyed Javad Mowla a, * a Department of Genetics, Faculty of Basic Sciences, Tarbiat Modares University, P.O. Box 14115-175, Tehran, Iran b Department of Biotechnology, Faculty of Medical Sciences, Tarbiat Modares University, P.O. Box 14115-115, Tehran, Iran c Urology and Nephrology Research Center and Shahid Labbafinejad Medical Center, Shahid Beheshti University of Medical Sciences, Tehran, Iran d Department of Urology, Heinrich Heine University, Moorenstr. 5, 40225 Du ¨sseldorf, Germany 1. Introduction Recent studies have shown many similarities between basic mechanisms mediating stem and cancer cell self-renewal [1,2]. The stem cell model for cancer hypothesizes that a key event in tumorigenesis is the disruption of genes involved in the regulation of stem cell self-renewal [1,2]. Therefore, the study of stem cell self-renewal genes has a great potential to expand our under- standing of carcinogenesis and to develop novel strategies for preventing and treating cancers [3]. Argonaute proteins, also known as PAZ (Piwi/Argonaute/Zwille) Piwi (P-element induced wimpy testis) domain (PPD) proteins, are members of a well-conserved family that is expressed in a variety of organisms, from fission yeasts to humans. The family can be divided into two subfamilies, Piwi and Ago, based on their primary sequence homology and expression pattern. Piwi subfamily members are expressed only in germ lineage cells, whereas members of the Ago subfamily are expressed ubiqui- tously [4–6]. The Piwi subfamily represents the first class of genes known to be essential for stem cell self-renewal in various organisms [5]. Members of Piwi family play important roles in RNA silencing [7], translational regulation [7], gametogenesis [8] as well as stem cell self-renewal [5]. In human, four members of the family have been identified: PIWIL1 (HIWI), PIWIL2 (HILI), PIWIL3 and PIWIL4 (HIWI2). All four members of Piwi family are primarily expressed in testis [4]. Expression of human PIWIL2 (HILI), located on 8p21.3, has been reported in a variety of tumor cells originating from not only germ but also somatic cells, including prostate, breast, gastrointestinal, ovarian and endometrial cancers [9]. Ectopic expression of the gene has also been reported in tumors of breast, rhabdomyosarcoma, and medulloblastoma of mouse, where it apparently inhibits apoptosis through activation of Stat3/Bcl-X L pathway [9]. To investigate a potential involvement of PIWIL2 in human bladder cancer, we examined the expression of the gene in bladder specimens with or without malignant lesions as well as a series of Cancer Epidemiology 33 (2009) 271–275 ARTICLE INFO Article history: Accepted 29 June 2009 Keywords: PIWIL2 Bladder cancer Gene expression Argonaute Testis Self-renewal ABSTRACT 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. ß 2009 Elsevier Ltd. All rights reserved. * Corresponding author. Tel.: +98 21 82883464; fax: +98 21 82883463. E-mail address: sjmowla@modares.ac.ir (S.J. Mowla). Contents lists available at ScienceDirect Cancer Epidemiology The International Journal of Cancer Epidemiology, Detection, and Prevention journal homepage: www.cancerepidemiology.net 1877-7821/$ – see front matter ß 2009 Elsevier Ltd. All rights reserved. doi:10.1016/j.canep.2009.06.011