Abstract 5108: Immunomodulatory and anti-tumor effect of radiation and induced telomere damage to treat pediatric high-grade gliomas

Abstract Pediatric high-grade gliomas (pHGGs), including diffuse intrinsic pontine glioma (DIPG) are among the most treatment refractory cancers in children. Despite multimodal therapy, prognosis is dismal with survival of 1 year for DIPG and a 5-year overall survival 10% for other pHGGs. Radiotherapy remains the only standard of care for DIPG that extends the survival by few months. In recent years, immunotherapy is emerging as a potential alternative treatment option. However, several factors have hindered the use of immunotherapy for pHGGs including “cold” immune environment with lack of immune cells infiltration, low tumor mutational burden, and lack of neo-antigen expression that prevents tumor recognition by the immune system. Therefore, novel therapies that activate the immune system while evading the tumor immunosuppression are highly needed. Here, we aim to demonstrate the immunomodulatory anti-tumor effects of THIO (6-thio-2’deoxyguanosine), a nucleoside analog and a telomerase-dependent telomere targeting agent, in DIPG mouse models. Our preclinical in vitro and in vivo data have demonstrated the efficacy of THIO in inducing telomeric damage, G2/M cell cycle arrest, and apoptosis in high-risk medulloblastoma and DIPG. Importantly, we have demonstrated that THIO crosses the blood-brain barrier and specifically targets tumor cells in an orthotopic mouse model of DIPG. THIO was shown to induce anti-tumor immunity through micronuclei formation leading to cGAS-STING pathway mediated activation of the innate and adaptive immune response in colon, lung, and hepatocellular carcinoma tumor models. Our preliminary data demonstrate the THIO-dependent induction of micronuclei formation co-localizing with cGAS and leading to STAT1 activation in DIPG cell lines. We have also shown that THIO synergistically sensitizes DIPG cells to ionizing radiation (IR), significantly decreasing cell proliferation. We are currently testing the combination of THIO+IR in an orthotopic mouse model for DIPG. We will present results on the potential of THIO and IR treatments to stimulate anti-tumor immunity through the activation of STING pathway in a syngeneic mouse model of DIPG. These preclinical studies will support the potential use of THIO and IR to treat children with high-risk pediatric brain tumors. Citation Format: Umaru Banlanjo, Shiva Senthil Kumar, Sergei Gryaznov, Rachid Drissi. Immunomodulatory and anti-tumor effect of radiation and induced telomere damage to treat pediatric high-grade gliomas abstract. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts) ; 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84 (6Suppl): Abstract nr 5108.