Abstract 4058: Second generation imidazolium compounds as tumor-specific intravesical therapeutic agents for non-muscle invasive bladder cancer
Authors: Satyal Uttam , Weader David , Valentine Henkel , Stromyer Michael , Youngs Wiley J. , Abbosh Philip H. 
Published: June 2022

Introduction: Intravesical therapy is critical in management of high-risk non-muscle invasive bladder cancer. The most effective intravesical therapy, BCG, has an ongoing shortage, while other second line therapies are not very effective, leaving radical cystectomy (RC) as the most effective option for cancer control. However, RC is a morbid, life-altering, and expensive procedure. Unfortunately, high-grade superficial disease is associated with cancer-specific mortality in 1/3 of the patients. Improved second line therapies or development of a BCG alternative would increase the rate of bladder preservation and survival, especially in light of the recurrent BCG shortages which have plagued bladder cancer patients. We earlier demonstrated that our first-generation imidazolium compounds are effective exfoliants that induce apoptosis via mitochondrial pathway and had potential to be used as intravesical therapy for bladder cancer. In this study, we developed and investigated second generation imidazolium compounds that have selective toxicity towards tumor tissues. We also investigated the mitochondrial target(s) of these imidazolium compounds.

Methods: Second generation imidazolium compounds were screened for their toxicity against various bladder cancer cell lines using CellTiter-Glo and colony forming assay. Apoptosis induction was confirmed using western blot and propidium-iodide incorporation analysis. In vitro toxicity comparison between BBN-tumor organoids and normal organoids was performed using confocal microscopy. In vivo toxicity of these compounds was studied in normal mice. For candidate target identification, mitochondria from cells grown in SILAC heavy/light media were treated with biotinylated imidazolium compound or a mixture of biotinylated compound plus TPP1 (a first-generation imidazolium compound). Lysates were subjected to streptavidin pull down followed by LC-MS/MS proteomics analysis. Shortlisted target candidates were knocked down using siRNA followed by imidazolium treatment to assess their candidacy as the imidazolium target.

Results: All second-generation imidazolium compounds had significantly higher toxicity to bladder cancer cell lines compared to first generation compounds. Compounds IS154 and IS155 were shown to be cancer selective. These two compounds showed no change in histopathology of murine bladder urothelium 24 h after intravesical instillation. Proteomics data from SILAC experiments prioritized three possible targets of the imidazolium compounds which are currently being explored.

Conclusions: Second generation imidazolium compounds are tumor-specific and highly potent compounds that are worthy of further study as an intravesical agent for the treatment of high grade superficial bladder cancer.

Citation Format: Uttam Satyal, David Weader, Henkel Valentine, Michael Stromyer, Wiley J. Youngs, Philip H. Abbosh. Second generation imidazolium compounds as tumor-specific intravesical therapeutic agents for non-muscle invasive bladder cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 4058.