Exploring SLAMF5/CD84 in Cancer: Advancing the Frontiers of Tumor Immunology

The Signaling Lymphocytic Activation Molecule (SLAM) family receptors play essential roles in regulating immune cell activation, differentiation, and communication. SLAMF5, also known as CD84, has drawn increasing attention in cancer immunology due to its involvement in both tumor progression and immune modulation. This review explores the expression patterns, signaling mechanisms, and functional roles of SLAMF5/CD84 within the tumor microenvironment. SLAMF5/CD84 is expressed on multiple immune cell types and contributes to immune evasion by enhancing regulatory B cell function, promoting myeloid-derived suppressor cell expansion, and upregulating immune checkpoint molecules such as PD-L1. Its expression has been implicated in various hematologic malignancies and solid tumors, including chronic lymphocytic leukemia, multiple myeloma, and triple-negative breast cancer. Emerging therapeutic approaches targeting SLAMF5/CD84-such as monoclonal antibodies and CAR T-cell therapies-offer promising strategies to counteract immunosuppression and improve treatment outcomes. By highlighting recent findings and therapeutic developments, this review underscores the significance of SLAMF5/CD84 as both a prognostic biomarker and a novel target in cancer immunotherapy. Understanding SLAMF5/CD84's multifaceted roles in the tumor immune landscape could support the development of more effective and personalized cancer treatment strategies.