Abstract 2127: Enhancing radiosensitivity in biliary tract cancer: The dual role of surufatinib in tumor suppression and macrophage reprogramming

Abstract Background: Biliary tract cancer (BTC) is notorious for its unfavorable clinical outcomes. Radiotherapy (RT) is a crucial component in BTC treatment. This study explores the radiosensitizing potential and mechanisms of Surufatinib (SF), an oral tyrosine kinase inhibitor, distinguished by its anti-angiogenic and immunomodulatory effects. Methods: In a NOZ mouse xenograft model, tumor growth and expressions of Ki-67, CD31 were analyzed. NOZ and TFK1 BTC cells treated with SF and/or RT underwent assessments for viability, cycle, and apoptosis using CCK8, colony formation, and flow cytometry. Macrophage polarization in SF/RT-treated tumor cell-macrophage co-cultures was studied using Elisa, qRT-PCR, and flow cytometry. Results: In vivo, SF impeded angiogenesis and bolsters the anti-tumor effect of radiotherapy. SF combined with RT significantly reduced subcutaneous tumor growth in nude mice, and diminished Ki-67 and CD31 expressions. In vitro, SF heightened cholangiocarcinoma cells' radio-sensitivity, causing DNA double-strand breaks and apoptosis. SF and radiotherapy combined notably increased γ-H2A expression and apoptosis levels (P0. 05). SF induced inflammatory response changes, favoring M2 to M1 macrophage polarization. In a tumor cell-macrophage co-culture, the SF-radiotherapy group showed increased IL-6 and decreased TGF-β (P0. 05), with upregulated M1 markers (IL-6, CXCL10) and downregulated M2 markers (TGF-β, CCL22, Arg-1) in macrophages (P0. 05). Both in vivo and in vitro, SF significantly reduced CD206+ M2-type macrophages (P0. 05). Conclusion: Surufatinib alters the immune microenvironment in cholangiocarcinoma, reversing the immunosuppressive macrophage polarization induced by radiotherapy and reprogramming M2-type macrophages into M1-type, thereby enhancing the radiosensitivity of cholangiocarcinoma. Citation Format: Ningyu Wang, Hong Ma, Xiangping Mei, Ai Huang, Yong Xiao, Jing Yao. Enhancing radiosensitivity in biliary tract cancer: The dual role of surufatinib in tumor suppression and macrophage reprogramming 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 2127.