Abstract 221: Investigating sex disparities in bladder cancer using carcinogen induced bladder cancer mouse model

Abstract DNA methylation plays a crucial role in regulating gene expression; thereby influencing tumor growth, progression, and response to treatment in muscle-invasive bladder cancer (MIBC). Intriguingly, methylation patterns may also underlie the pronounced sex disparities in MIBC incidence and outcomes; where men show a fourfold higher incidence rate. Still, female patients face higher risks of progression, recurrence, and mortality. Despite substantial documentation of DNA methylation patterns in patient tumors, translating these findings into actionable treatments requires reliable preclinical models that recapitulate the human methylation landscape. Such models offer a controlled environment to explore methylation-driven gene expression changes and evaluate potential therapeutic approaches that are otherwise challenging in clinical settings. Our research focuses on the BBN (N-butyl-N-(4-hydroxybutyl) nitrosamine)-induced bladder cancer mouse model. The BBN model mimics the histological and mutational features of human MIBC. We investigated whether the BBN induced bladder cancer model recapitulates the DNA methylation patterns found in clinical bladder cancer, and the use of the model to shed light on methylation-driven shifts in gene expression and pathways. By employing methylation arrays and RNA sequencing, we systematically compared DNA methylation profiles and gene expression patterns in MIBC tumors between BBN-induced mouse bladder tumors and human clinical samples. We identified 4, 250 common differentially methylated genes (DMGs) and 512 shared differentially expressed genes (DEGs) between human and BBN-induced mouse tumors. Notably, 280 sex-specific DMGs and four conserved sex-specific DEGs, including XIST, KDM5D, UTY, and DDX3Y, were identified, highlighting the ability of the BBN model to demonstrate sex-based epigenetic characteristics observed in human MIBC. Pathway analysis revealed that genes associated with mTOR signaling were hypomethylated and upregulated in male tumors. While the EMT pathway was upregulated in female tumors across both species. These findings confirm that the BBN model not only recapitulates the methylation patterns of human MIBC but can also serve as a valuable tool to investigate sex-specific methylation mechanisms in disease progression. The BBN model shows significant promise for advancing MIBC biology and guiding the development of sex-specific, methylation-targeted therapies. This abstract was reviewed and refined using AI-based tools to check grammar and improve clarity. Citation Format: Bhavisha Doshi, Eduardo Cortes, Bryan M. Gillard, Ellen Karasik, Norbert Sule, Barbara A. Foster, Jianmin Wang, Wendy J. Huss, Anna Woloszynska. Investigating sex disparities in bladder cancer using carcinogen induced bladder cancer mouse model [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2025; Part 1 (Regular Abstracts); 2025 Apr 25-30; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2025;85(8_Suppl_1):Abstract nr 221.