TRIM29 is Critical for Bladder Cancer Progression and Modulates the Tumor-Immune Niche

TRIM29 (Tripartite Motif-Containing Protein 29), also known as ATDC (Ataxia-Telangiectasia Group D-Complementing Protein), is an E3 ubiquitin ligase frequently upregulated in muscle-invasive bladder cancer (MIBC). We have previously shown that TRIM29 overexpression in a genetically engineered mouse model (GEMM) is sufficient to drive development of MIBC. We have also shown that TRIM29 is enriched in basal bladder cancer subtypes and is part of a TP63-regulated program that promotes migration and invasive progression. Prior studies suggest that Keratin 5/14 (K5+/K14+) expressing basal-stem progenitor cells in the urothelium are the cells of origin for MIBC in mice. However, whether Trim29 expression in these basal urothelial cells is required for MIBC development has not been established. In this study, we find that Trim29 expression in K5+ basal cells is linked to the inflammatory response and is critical for bladder tumor formation and invasive progression. We show that urothelial TRIM29 expression is enhanced during inflammation in humans and under inflammatory and genotoxic stress in mice. Knockout (KO) of Trim29 in the K5+ basal urothelium of a GEMM exposed to a bladder-specific chemical carcinogen blocked MIBC development. Further, urothelial Trim29 KO enriches immune cell recruitment to the bladder and upregulates STING and inflammatory signaling in mouse and human bladder cancers. These data reveal a critical role for TRIM29 in immunomodulation of the bladder tumor microenvironment (TME), which may act in concert with pro-migratory basal gene programs to expedite MIBC development.