Abstract 831: The functional crosstalk between tissue transglutaminase (TG2) and CD24 enhances cancer stem cell traits and therapy resistance in high grade serous ovarian cancer.

Abstract High-grade serous ovarian cancer (HGSOC) remains one of the most lethal gynecologic malignancies, largely due to persistent cancer stem cells (CSCs) that drive disease progression. Our data revealed that tissue transglutaminase 2 (TG2) is a central mediator of OCSC biology through its interaction with fibronectin (FN) and integrins, activating oncogenic pathways, including Wnt signaling, that promote stemness and platinum resistance. We further identified that TG2 cooperates with the immune-regulatory receptor CD24 to anchor OCSCs to peritoneal organs, facilitating early metastatic implantation and ascites formation. To therapeutically disrupt this axis, we synthesized a selective peptide inhibitor (BP) that blocks the TG2-FN interaction and developed a CD24-neutralizing antibody (CD24-Ab), each of which suppresses CSC function in preclinical models. We then combined these modalities into a single first-in-class antibody-peptide conjugate, APC (CD24-Ab-TG2-BP), designed to simultaneously disrupt CD24 signaling and TG2-mediated CSC-tumor microenvironment (TME) interactions. TCGA analysis of HGSOC revealed TG2 and CD24 mRNA amplification in 3% and 2% of cases, respectively. Flow cytometry confirmed robust TG2 (58%, 51%) and CD24 (98%, 100%) expression, with substantial co-expression (55%, 45%) in OVCAR4 and OVCAR5 cells, respectively. APC treatment significantly downregulated CSC-associated markers (NANOG, OCT4, SOX2, ALDH1A1) and disrupted spheroid architecture. Co-immunoprecipitation demonstrated a specific TG2-CD24 interaction in SKOV3 and OVCAR4 cells, while biochemical fractionation localized the complex to lipid raft microdomains, signaling platforms that integrate receptors and downstream oncogenic effectors. In OC xenograft models, treatment with APC significantly reduced tumor volume (0.22 ± 0.11 mm3 vs. 1.7 ± 1.1 mm3; N =5, P 0.001), tumor weight (0.64 ± 0.21 gm vs. 1.53 ± 0.46 gm; N =5, P 0.01), and metastasis (5.3 + 3.6 vs. 10 + 3.6; N =5, P 0.001) when compared with IgG controls, thus demonstrating potent anti-tumor efficacy. Collectively, these findings identify a lipid raft-restricted TG2-CD24 complex as a novel driver of OCSC maintenance and chemoresistance in HGSOC. Targeting this interaction with APC effectively disrupts CSC-TME crosstalk and suppresses tumor progression, establishing TG2/CD24 axis as a novel therapeutic vulnerability for overcoming resistance and recurrence in HGSOC. Citation Format: Rohit Pravin Nagare, Habeebunnisa Begum, Ben Wamba, Jogender Tushir-Singh, Fabrizio Pin, Salvatore Condello. The functional crosstalk between tissue transglutaminase (TG2) and CD24 enhances cancer stem cell traits and therapy resistance in high grade serous ovarian cancer abstract. In: Proceedings of the American Association for Cancer Research Annual Meeting 2026; Part 1 (Regular Abstracts); 2026 Apr 17-22; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2026;86(7 Suppl):Abstract nr 831.