Abstract 5297: Immune profiling of CRC identifies a potential signature associated with immunosuppression

Abstract Colorectal Cancer (CRC) shows limited response to immunotherapies due to 85% of cases involving proficient mismatch repair. The immune profile of CRC remains poorly understood, making it critical to investigate immune infiltration patterns in the tumor microenvironment (TME) of CRC to improve therapeutic outcomes. Adenosine accumulates at high levels in the TME, suppressing immune responses via the A2A receptor (A2AR) on immune cells, a crucial pathway in immune suppression. This study aims to characterize the immune profile of CRC and identify the immune signature associated with adenosine-mediated immunosuppression. Multiplex immunofluorescence staining was performed on 170 CRC samples from 85 patients on 12 immune markers, including CD4+ and CD8+ for T cells, CD56+ NK cells, CD68+ macrophages, CD11b+ dendritic cells, FOXP3 for Treg cells, Glut-1 (hypoxia), Ki67, IDO and PD-1 (immune checkpoints), and CD73 and A2AR of the adenosine pathway. These markers provided a comprehensive assessment of immune suppression mechanisms. Our findings showed CRC tumors with specific immune infiltrates, including high levels of CD4+ and CD8+ T cells, CD11b+ dendritic cells, and CD68+ macrophages, alongside elevated Glut-1 and A2AR expression, marking A2AR’s role in the adenosine-mediated suppression in CRC. Conversely, low levels of infiltrates were observed for CD56+, CD73+, FOXP3+, IDO+, Ki67+, and PD-1+ cells. Subdividing patients into A2AR-high and A2AR-low groups revealed that A2AR-high tumors exhibited significantly higher CD68+ macrophage infiltration, suggesting A2AR may mediate adenosine effects primarily through macrophages. Notably, A2AR was predominantly expressed on CD8+ T cells in CRC tumors, suggesting that infiltrating CD8+ cells are suppressed by adenosine signaling. Markedly, high A2AR expression was observed despite significant CD73 deficiency in CRC tumors. On average, only 0.09% CD73+ cells. with 39% of tumor cores showing no CD73 expression. Moreover, 40% of CD73-deficient tumors retained high A2AR expression, indicating the presence of alternative adenosine-producing pathways independent of CD73. Significant differences in immune infiltrates were also noted between CRC subtypes. Colon adenocarcinomas (n=50) exhibited higher A2AR+ infiltrates and lower CD4+ T cell infiltration compared to rectal adenocarcinomas (n=35), suggesting stronger adenosine-mediated immunosuppression in colon adenocarcinomas. These findings provide valuable insights into the role of adenosine-driven immunosuppression in CRC and highlight potential therapeutic targets to counter immune suppression. The observed CD73 deficiency suggests the need to explore alternative adenosine-producing pathways in CRC. Continued investigation into CRC immune signatures will aid in identifying new biomarkers and developing improved immunotherapy strategies for CRC patients. Citation Format: Dongyu Han, Yong Qin. Immune profiling of CRC identifies a potential signature associated with immunosuppression [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 5297.