Subcellular Localization of CD24 Is Associated with Integrin β1 Signaling, Immune Suppression, and Clinical Outcomes Across Human Cancers.

CD24 is an emerging innate immune checkpoint that regulates inflammatory and antiviral immune responses through interactions with Siglec family receptors. Although CD24 has been extensively studied in immune regulation and has recently gained attention as a therapeutic target in infectious and inflammatory diseases, its role in cancer remains incompletely understood. CD24 is overexpressed in multiple human malignancies, where accumulating evidence suggests that it promotes tumor progression and immune evasion through activation of diverse intracellular and extracellular signaling pathways. However, the importance of its subcellular localization and associated signaling remains poorly defined. Here, we investigated CD24 expression, localization, signaling associations, immune-cell infiltration, and clinical outcomes using publicly available cancer datasets, focusing on breast cancer (BRCA), cervical squamous cell carcinoma (CESC), and glioblastoma multiforme (GBM). Our analyses revealed prominent membrane-associated CD24 localization in BRCA and CESC, whereas CD24 was predominantly cytoplasmic in GBM. BRCA and CESC exhibited increased integrin β1 expression and distinct associations between CD24 and components of integrin β1/SRC and TGFβ-associated signaling networks, including MEK1 and SMAD7. In addition, we identified a structurally consistent and energetically favorable predicted interface between CD24 and Siglec-10, suggesting a mechanism by which CD24 may suppress anti-tumor immunity. Elevated CD24 expression was associated with immune-infiltration patterns consistent with an immunosuppressive tumor microenvironment in BRCA and CESC, including negative associations with M1 macrophage, CD8+ T-cell, and NK-cell infiltration. Importantly, high CD24 expression was associated with unfavorable overall survival in BRCA and CESC, whereas the opposite relationship was observed in GBM. Collectively, these findings suggest that the subcellular distribution of CD24 may be associated with distinct tumor signaling, the immune microenvironment, and prognostic profiles, highlighting the potential importance of CD24 localization in determining its tumor-type-specific biological functions.