MAD2L1 (mitotic arrest deficient 2 like 1) is a critical component of the spindle-assembly checkpoint that prevents anaphase onset until chr4 are properly aligned at the metaphase plate 12. In its closed conformation (C-MAD2), it forms a heterotetrameric complex with MAD1L1 at unattached kinetochores, promoting the conversion of open conformation molecules (O-MAD2) to C-MAD2 2. MAD2L1 inhibits the anaphase promoting complex by sequestering CDC20, executing the mitotic checkpoint that monitors kinetochore-spindle attachment 341. Beyond its canonical checkpoint role, MAD2L1 is significantly dysregulated in multiple malignancies. It is upregulated in gastric cancer, associated with poor prognosis and tumor relapse 5. In breast cancer, high-glucose conditions drive MAD2L1 upregulation through RCC2 lactylation, promoting rapid proliferation 6. MAD2L1 is identified as a cancer-driver gene in malignant pleural mesothelioma, where its overexpression differentiates diseased from normal tissue 7. In hepatocellular carcinoma, MAD2L1 upregulation correlates with poor prognosis and is essential for MYC-driven tumorigenesis 89. Additionally, MAD2L1 stabilization via FXR1-dependent mechanisms drives soft tissue sarcoma growth and prevents senescence 10, while in multiple myeloma, MAD2L1 suppression effectively inhibits disease progression 11.