Abstract 4645: Dynamic post-translational events designate muscle invasion of non-muscle invasive bladder cancer

Abstract Bladder cancer (BC), the second most prevalent genitourinary malignancy where majority (∼70%) of the patients present with non-muscle invasive BC (NMIBC) while the rest (∼30%) present with muscle invasive BC (MIBC) at diagnosis. Despite the extensive clinical management, 50% of NMIBC relapses and progress to anew MIBC. Owing to the poor prognosis for progressive MIBC, it is indispensable to understand and mitigate the evolution of NMIBC to MIBC. In particular the intratumoral heterogeneity pre- and post-therapy in NMIBC, is crucial to pin the genetic, molecular and/or post-translational events and the mechanism(s) involved in this critical transformation. Studies have identified Promyelocytic leukemia factor (PML) as a defined proapoptotic protein that regulates BC cell growth and progression. Further, studies have identified that loss of PML-nuclear bodies (PML-NB) corresponds to a ‘low-is-worse’ association with BC clinical outcomes. Herein, we investigated the mechanism on how the PML-NB derails and its significance in disease prognosis. In this study, we identified a unique site specific post-translational modification (SSPT) in PML that leads to its destabilization and loss. Further, significance of this PML-SSPT in clinical outcomes were investigated in a test cohort of (n=112) BC patients. For this, MIBC and NMIBC tissues in triplicates were custom archived in tissue microarrays and were examined for PML-SSPT with Opal immunohistochemistry utilizing our custom synthesized antibody. The spatio-temporal PML-SSPT modification was analyzed in QuPath v 0.5.1 bioimage analysis platform with a modified fluorescence image analysis module. We observed a significantly higher PML-SSPT modification in MIBC compared to NMIBC and a relative increase in PML-SSPT modification associated with advanced disease stage defining its crucial role in cancer progression. More importantly, higher PML-SSPT in patients with metastatic disease as well as with relapsed disease highlighted its critical role in mediating disease dissemination and evolution to aggressive MIBC. Together, the outcomes identified a crucial post-translation modification event in PML that corresponds to the coordination of de novo MIBC from NMIBC. Further, these outcomes identified a novel molecular target and paves way to develop novel molecular tumor targeted maintenance therapeutic strategies for the cure of BC. Funding: This work was funded by the Department of Defense, DoD CA-210339; Oklahoma Center for the Advancement of Science and Technology, OCAST-HR19-045; and the National Institutes of Health P20GM103639 awarded to Dr. Aravindan. The work was also supported by the NCI Cancer Center Support Grant [P30CA225520], NIGMS [P30GM154635], and a grant from the Oklahoma Tobacco Settlement Endowment Trust [R23-03] awarded to the OU Health Stephenson Cancer Center. Citation Format: Sabir Salim, Sreenidhi Mohanvelu, Sheeja Aravindan, Poorvi Subramanian, Loganayaki Periyasamy, Natarajan Aravindan. Dynamic post-translational events designate muscle invasion of non-muscle invasive bladder cancer [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 4645.