Structure, Function, and Role of Schlafen 5 in Cancer

Schlafen 5 (SLFN5) is a member of the Schlafen protein family originally identified for its roles in immune regulation and cell cycle control. Structurally, SLFN5 contains an N-terminal Schlafen Core domain involved in nucleic-acid binding, a Linker domain, and a C-terminal Helicase domain required for efficient suppression of LINE-1 retrotransposition. In cancer, SLFN5 exhibits highly context-dependent functions, acting either as a tumor suppressor or as a pro-tumorigenic factor depending on tumor type and experimental conditions. It suppresses proliferation and invasion in breast cancer and renal cell carcinoma via PTEN/AKT signaling and downregulation of MMPs, while promoting progression in castration-resistant prostate cancer, glioblastoma, and colorectal cancer through AR/mTORC1, STAT1 co-repression, and IFN-JAK-STAT inhibition, respectively. Discrepant findings in lung cancer suggest that supraphysiological expression may trigger non-canonical effects. Clinically, SLFN5 expression correlates with tumor stage, metastasis, and patient survival, supporting further evaluation of SLFN5 as a potential prognostic biomarker, although its diagnostic utility remains to be established. This review summarizes the structural features, molecular functions, and tumor-type-specific roles of SLFN5, with an emphasis on recent advances in oncology research, providing insights that may contribute to personalized cancer therapy and prognostic evaluation.