Abstract A27: TRIM29-mediated immune evasion in bladder cancer invasive progression


 Background: Progression from noninvasive to muscle-invasive and then metastatic bladder cancer causes >17,000 deaths each year in the United States. Unfortunately, the molecular drivers of progression remain poorly understood and no strategies to prevent progression exist. We have identified an E3 ubiquitin ligase, TRIM29, which is highly expressed in 70% of muscle invasive bladder cancers (MIBC). Global overexpression of TRIM29 in a genetically engineered mouse model (GEMM) is sufficient to induce urothelial cancer initiation and invasive progression. TRIM29 has also been shown to bind and ubiquitinate STING (Stimulator of Interferon Genes), a regulator of anti-tumor cytokine production. However, the role of TRIM29-mediated suppression of STING and innate immune responses in invasive progression was not previously understood. Hypothesis: Given the importance of Trim29 in invasive progression demonstrated in our GEMM, we hypothesized TRIM29-mediated degradation of STING creates an immune-privileged niche required for muscle invasion. Methods: To determine the requirement for Trim29-mediated immune suppression and bladder cancer invasive progression, we generated a urothelial specific tamoxifen inducible Trim29 knockout (KO) GEMM. To induce bladder tumorigenesis, N-butyl-N-(4-hydroxybutyl) nitrosamine (BBN), a urothelial specific chemical carcinogen with similarities to tobacco, was delivered to mice via drinking water. Results: As expected, BBN promoted development of muscle-invasive urothelial tumors in 50% of mice after 24 weeks. Tamoxifen-induced Trim29 KO completely blocked progression to muscle-invasion, although these mice did demonstrate development of low grade, non-muscle invasive tumors. BBN upregulated Trim29 expression in the urothelium, but only modestly increased Sting and infiltrating macrophage and T cells. In contrast, Trim29 KO mice, which did not develop invasive tumors, harbored substantially elevated Sting levels in the urothelium and substantially increased macrophage and T cell infiltration in the bladder and tumor. In vitro, TRIM29 promoted STING ubiquitination and TRIM29 knockdown increased STING protein levels in bladder cancer cell lines. TRIM29 KO in these cells also resulted in increased expression of innate immune cytokines. Conclusion: These results suggest that TRIM29-mediated downregulation of STING in the bladder results in decreased immune surveillance in the tumor microenvironment, contributing to the development of an immune privileged niche required for MIBC progression.
 Citation Format: Alan Kelleher, Yin Wang, Luke Broses, Yu Leo Lei, Phillip Palmbos. TRIM29-mediated immune evasion in bladder cancer invasive progression [abstract]. In: Proceedings of the AACR Special Conference: Tumor Immunology and Immunotherapy; 2022 Oct 21-24; Boston, MA. Philadelphia (PA): AACR; Cancer Immunol Res 2022;10(12 Suppl):Abstract nr A27.