Abstract 109: Y chromosome genes contribute to higher male bladder cancer incidence
Authors: Hsu Iawen , Railkar Reema , Li Quentin , Agarwal Piyush 
Published: August 2015

Introduction: Clinical reports show that males have a higher bladder cancer (BCa) incidence than females. The gender bias in BCa occurrence suggests that there may be genetic differences between males and females. One apparent factor important in sex differentiation is the existence of the Y chromosome in males. We sought to evaluate whether genes on the Y chromosome play a role in BCa development.

Methods: mRNA expression of Y chromosome genes from male and female BCa tissues were analyzed from the Oncomine database (http://www.oncomine.org). Real-time PCR (RT-PCR) was then used to analyze SMCY mRNA expression in all available BCa cell lines in our lab (RT4, T24, UMUC3, UOBL101, UOBL102, UOBL103, 647v, TCCSUP, 253J, J82, 5637, HT1197, SCaBer, TCCSUP, and SVHUC). Lentiviral vectors with SMCY shRNA were used for SMCY knockdown in 647v and RT4 (male-derived) BCa cell lines. Lentiviral vectors encoding SMCY cDNA were used for SMCY overexpression in T24 (female-derived) and UMUC-3 (Y chromosome-deleted male-derived) BCa cell lines. Cell proliferation was performed using the MTT assay. Anchorage independent cell growth was performed by plating 1% agarose on the bottom of plates, and then seeding the cell suspension in 0.35% of agarose in MEM. Cells were grown in agarose for two weeks and the number of colonies was counted.

Results: Oncomine analysis demonstrated that certain genes on the Y chromosome (SMCY, DDX3Y, and USP9Y) have higher expression in male tumors than in female tumors. RT-PCR confirmed this finding in BCa cell lines with respect to SMCY mRNA expression. Furthermore, knockdown of SMCY in the male-derived BCa cell lines reduced cell proliferation rates. Moreover, overexpression of SMCY in BCa cells derived from female patients or from Y chromosome deleted male patients (UMUC-3) increased the cell proliferation rates. Anchorage independent cell growth is a hallmark of higher tumorigenicity. Consistently, 647v with SMCY knockdown grow fewer colonies compared to control cells in anchorage independent cell growth assay. T24 and UMUC-3 with SMCY expression grow more colonies than control cells. SMCY is a histone H3 lysine 4 (H3K4) demethylase and plays a central role in histone code. It demethylates trimethylated and dimethylated but not monomethylated H3 lysine 4. H3K4 methylation is tightly associated with gene activation. Our preliminary data indicated that with SMCY knockdown, trimethylated and dimethylated H3K4 is increased in 647v and RT4 cells, suggesting that SMCY maintains its demethlyase activity in cancer cells.

Conclusions: Overall, we hypothesize that Y chromosome genes may contribute to cancer growth and tumorigenesis in men and partially account for higher male bladder cancer incidence rates. The finding that SMCY is implicated in histone modification also suggests the importance of chromatin remodeling genes in bladder cancer.

Citation Format: Iawen Hsu, Reema Railkar, Quentin Li, Piyush Agarwal. Y chromosome genes contribute to higher male bladder cancer incidence. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 109. doi:10.1158/1538-7445.AM2015-109