Abstract 3867: Small molecule inhibitors targeting TG2 in ovarian cancer and identification of drug escape pathways

Abstract Ovarian cancer (OC) is the 8th most common cancer in women. Most patients with high-grade serous OC present with intraperitoneal disseminated disease when diagnosed, due to mild symptoms in earlier disease stages. They respond efficiently to cisplatin or taxol-based compounds in the front-line treatment; however, resistance emerges in the majority of cases, which allows tumors to progress. There is an urgent need for improved treatment to increase patients’ survival. Tissue transglutaminase (TG2) is a protein overexpressed in many solid tumors, including ovarian; it interacts with fibronectin (FN) in the extracellular matrix and promotes OC intraperitoneal dissemination. This makes TG2 a promising target for treatment. We previously identified MT4 as a promising small molecule inhibitor (SMI) able to disrupt TG2-FN protein-protein interaction, prevent cancer cell adhesion and spheroid formation, and sensitize OC cells to chemotherapeutic drugs, such as paclitaxel (Sima LE et al., Mol Cancer Ther., 2019). We recently investigated the effect of 5 new MT4 analogues on OC cells behavior. We found that compound #3011 completely prevented spheroids formation, similar to Tgm2 gene excision, while #3002 decreased cell adhesion onto FN. We used phosphoproteomics to analyze the adaptive signaling of OC cells treated with MT4 that escape treatment. New promising molecular TG2 co-targets for OC treatment have been identified as effectors of MT4 escape pathways: sirtuins and p21-activated kinases (PAKs). Combination of signaling inhibitors and TG2-directed SMIs induce OC cell death in both 2D and 3D conditions, with potential for future therapeutic use. Our multiplex IHC data shows that in OC tumors TG2 is expressed by cancer cells, as well as by α-SMA+ CAF subset. Therefore, we next sought to test the effect of TG2 drug targeting on OC cells-fibroblasts 3D co-cultures. Our results showed that MT4 prevents heterospheroid self-assembly in vitro, which indicates potential disruption in tumor-stroma communication using TG2-directed therapies. In parallel, we developed new tools to test drug combinations, as well as radiation therapy regimens for their potential to inhibit cancer spreading. We produced a new glass microfluidic chip and adapted a miniaturized mesothelial clearance assay for live cell imaging. We obtained new SKOV3 and SKOV3-TG2KO LifeAct+ stable cell lines to allow real time imaging measurements of OC cell behavior. Subpopulations were sorted based on actin-GFP expression level and characterized by cell motility quantification. Cell lines with behavior similar with parental cells were selected for further use. We currently use these tools to investigate the potential of TG2 targeting to enhance response of cancer cells to new FLASH radiation sources (Orobeti S et al, Sci. Rep., 2024), such as very high energy electrons generated with a high-intensity laser plasma accelerator system. Citation Format: Monica Tudor, Cristian Munteanu, Gabriela Chiritoiu, Stefana Orobeti, Alexandra Bran, Florin Jipa, Felix Sima, Gary E. Schiltz, Daniela Matei, Livia Elena Sima. Small molecule inhibitors targeting TG2 in ovarian cancer and identification of drug escape pathways [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 3867.