Abstract 4699: Intratumoral adenosine: Contributions from host versus tumor and interaction with radiotherapy

Abstract Purpose: Tumor irradiation generates high levels of extracellular ATP that is metabolized to suppressive adenosine that is implicated in cancer progression. The relative contribution of host and cancer cell-derived adenosine and downstream signaling to radioresistance is unclear. Methods: In a murine model of breast cancer (EO771), we measured the expression of adenosine signaling proteins: CD73 that metabolizes AMP to adenosine and adenosine receptors, A2aR and A2bR by flow cytometry. We measured adenosine concentration by LC-MS in supernatants of WT tumor cells and those that lack CD73 (CD73-/-) grown in vitro. To understand the non-tumor cell-derived contribution to adenosine, we measured adenosine concentration in breast EO771 tumors grown in CD73-/-, A2aR-/-A2bR-/- or WT mice. Tumor growth studies were performed in the untreated and irradiated (8 Gy x 3) settings. In comparison, we conducted tumor growth experiments in CD73-/- & WT EO771 tumors grown in WT mice to understand the contribution of tumor-derived CD73 to tumor control. Results: In murine EO771 tumors, the proportion of viable non-immune (CD45-) cells that express CD73 was significantly higher than in the CD45+immune compartment (18.3% vs 5.7%). In contrast, the proportion of viable immune (CD45> +) cells that express A2aR was significantly higher than the CD45-compartment (7.8% vs 4.4%), suggesting complementary roles of the two compartments. In vitro, adenosine production was abrogated in CD73-/- EO771 tumor cells compared to WT controls (0.14µM vs 2.4µM). Tumor cell irradiation caused a significant increase in adenosine in WT EO771 but not CD73-/-EO771. When grown in WT mice, tumor growth was delayed in CD73-/- tumors compared to WT controls (306 mm3vs 1165 mm3 on day 22). Loss of CD73 in tumor cells significantly improved radiosensitivity and increased overall survival on 150-day by 50%. Quantification of adenosine in EO771 tumors grown in WT, CD73-/-& A2aR-/-A2bR-/-mice revealed that absence of host CD73 caused 3.5-fold decrease in intertumoral adenosine, while loss of A2aR and A2bR caused no significant change. Furthermore, tumor control in both CD73-/-& A2aR-/-A2bR-/-mice improved by 50% in the absence of radiation. However, after tumor irradiation, loss of host A2aR and A2bR but not CD73 improved tumor control. Conclusions: Results suggest that tumor cell expression of CD73 is integral for production of adenosine and loss of expression significantly improves radiosensitivity. Loss of CD73 from non-tumor cells did not influence radiosensitivity, whereas expression of A2aR and A2bR does. These data suggest that tumor-derived adenosine contributes to tumor growth and radioresistance and non-tumor cells in the TME are important for A2aR/A2bR-mediated effects of adenosine. CD73 & A2aR/A2bR offer an exciting therapeutic strategy to mitigate radiation-induced suppressive changes for improved radiosensitivity and tumor control. Citation Format: Shruti Bansal, Samantha Sarti, Namita Sen, Chelsea Rahiman, Brian Ragaishis, Lindsay Caprio, Benjamin Izar, Catherine Spina. Intratumoral adenosine: Contributions from host versus tumor and interaction with radiotherapy [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 4699.