Abstract 5096: G2.2, a synthetic mimetic of heparan sulfate hexasaccharide, inhibits chemotherapy-induced dormancy

Abstract Background: Tumor cells can enter distant sites and persist as disseminating tumor cells (DTCs). DTCs are known to remain dormant, exhibiting reversible cell cycle arrest/quiescence and anti-cancer therapy resistance. We and others have shown that Insulin-like Growth factor 1 (IGF1) - Receptor (IGF1R) is critical in therapy resistance and cancer stem cell (CSC) phenotype. We have recently discovered a novel role of sulfated glycosaminoglycan (sGAG) oligosaccharides, particularly heparan sulfate hexasaccharide (HS06), in regulating IGF1R signaling through direct binding to its extracellular domain in competition with IGF1. A structurally specific non-saccharide mimetic of HS06, called G2.2, potently inhibits CSC phenotype in various cancers. These observations led us to explore the possible involvement of IGF1R in dormancy phenotype and G2.2 in targeting dormant cells. Methods: HT-29, as well as HCT-116 (wild type, IGF1R KO (CRISPR), and IGF1R KO + GAG binding site mutant IGF1R (R107H) expressing) cells were studied. Cells were treated with clinically relevant oxaliplatin and 5-fluorouracil (FUOX) (5µM and 125µM, respectively) for 48 hours. They were reseeded in the presence and absence of IGF1 (20 ng/ml) or G2.2 (0→100 µM) to monitor growth and characterize dormancy - DEC2, p27, and Ki-67 (Flow and IF) as well as sGAG expression. Furthermore, FUOX-treated HT-29 cells were harvested on day 7 and implanted subcutaneously in nude mice (106 cells/mouse). Two weeks following s.c. injection, the animals were randomized to Vehicle or G2.2 (100 mg/kg, three times a week) for 10 weeks and monitored till euthanasia criteria were met. Results: The growth curve showed three phases- the initial dormancy induction (phase 1) followed by a growth arrest/dormancy maintenance (phase 2), which was promptly followed by an exponential growth/dormancy escape (phase 3) representing the dormant cell cycle. Indeed, DEC2, p27 expression, and % of Ki-67 negative cells were higher during phase 2 and decreased before phase 3. Interestingly, sGAG and pIGF1R levels were significantly higher in Phase 1 and Phase 2. Consequently, in the presence of IGF-1, cells failed to enter phase 2. On the other hand, G2.2 treatment resulted in a prompt entry into phase 2 but failure to exit phase 3 in cells expressing wild-type IGF1R but not R107H mutant IGF1R. In the HT-29 DTC-induced xenograft model, we observed 100% inhibition of tumor recurrence in the G2.2 treated group, but all the animals in the treated group eventually succumbed to tumor regrowth (with a latent phase). Conclusions: Our in vitro model is representative of therapy-induced tumor arrest followed by spontaneous recurrences observed in the clinic. sGAG-IGF1R interaction may be a critical regulator of DTC survival, and G2.2 represents a novel therapy for targeting DTC, partially through IGF1R inhibition. Citation Format: Shoja M. Haneefa, Rio Boothello, Bharath Villuri, Rawan Fayyad, Priyanka Mishra, Sajni Vora, Umesh R. Desai, Bhaumik B. Patel. G2.2, a synthetic mimetic of heparan sulfate hexasaccharide, inhibits chemotherapy-induced dormancy [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 5096.