Abstract 1373: Adenosine-driven immune profile in breast cancer

Abstract Adenosine accumulation in tumor microenvironment (TME) suppresses T cell activation and effector functions, posing challenges for immune therapies in cancers, including breast cancer (BC). Upregulated adenosine A2A receptor (A2AR) has been observed in BC tumors compared to normal tissues. However, the immune patterns shaped by adenosine signaling across BC subtypes, particularly triple-negative breast cancer (TNBC), remain poorly understood. To examine adenosine-driven immune profile in BC, we analyzed 138 tumor cores from 69 BC patients using multiplex immunofluorescence staining for 12 markers: CD73, A2AR, CD8, CD4, CD56, FOXP3, CD68, CD11b, Ki67, PD-1, Glut-1, and IDO, alongside the nuclear marker DAPI. Our findings revealed elevated levels of A2AR, CD68, CD4, CD8, Ki67, PD-1, and Glut-1 in BC tumors, indicating a TME enriched with CD4+ T helper cells, C8+ cytotoxic T cells, and CD68+ macrophages. Tumors with high A2AR expression exhibited increased PD-1+ immune infiltrates and elevated Ki67 levels, suggesting that A2AR activation impairs T cell function and promotes tumor proliferation. A2AR was predominantly expressed on CD4+ and CD8+ T cells, suggesting the connection among adenosine receptor activation, immunosuppression, and tumor growth. We further explored the role of CD73, an enzyme converting AMP to adenosine, in the BC TME. CD73+ tumors showed significantly higher infiltration of CD4+ cells, CD56+ NK cells, CD68+ macrophages, and PD-1+ immune cells compared to CD73- tumors. CD73 expression, linked to adenosine production, was tied to an adenosine-rich TME increasing immune infiltration but reducing immune functionality, characterized by elevated PD-1 and IDO expression. Additionally, PD-1+ immune infiltrates correlated with higher levels of CD4+, CD8+, CD68+, and CD11b+ cells and increased IDO expression. High CD73 levels correlated with elevated CD68+ macrophage and PD-1 expression, despite greater CD4+ T cell infiltration. These findings suggest that CD73-driven adenosine signaling contributes to an immunosuppressive TME, even with immune cell presence. In TNBC tumors (n=16), Glut-1 expression, a hypoxic marker, was significantly higher than in non-TNBC tumors (n=49), indicating a more hypoxic and adenosine-rich TME. TNBC tumors also showed a higher proportion of CD73+ tumor cells. Ki67 analysis levels revealed higher cancer cell proliferation in TNBC compared to HER2+ tumors (n=17), indicating TNBC’s aggressive nature. In conclusion, BC tumors display unique immune profiling linked to adenosine signaling within the TME. High A2AR and CD73+ expressions are associated with tumor proliferation and immunosuppressive infiltrates driven by adenosine and PD-1 signaling. The hypoxic, adenosine-rich TME in TNBC highlights adenosine regulation's critical role in progression. These findings underscore adenosine as a promising therapeutic target for developing anti-tumor strategies, particularly for TNBC patients. Citation Format: Xi Chen, Yong Qin. Adenosine-driven immune profile in breast cancer [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 1373.