LIN9 is a core component of the DREAM complex that functions as a transcriptional regulator controlling cell cycle progression and mitotic gene expression. LIN9 plays essential roles in activating genes required for G2/M transition and mitosis, with depletion leading to mitotic defects, cell cycle arrest, and apoptosis 12. The protein acts through the Myb-MuvB (MMB) complex, where it serves as a scaffold protein that facilitates B-Myb recruitment to regulate cell-cycle-dependent gene expression 3. In cancer contexts, LIN9 exhibits dual roles: it can function as a tumor suppressor when properly regulated, but its overexpression contributes to oncogenesis and therapeutic resistance 45. High LIN9 expression is associated with poor clinical outcomes in breast cancer patients receiving chemotherapy and contributes to paclitaxel resistance in triple-negative breast cancer through upregulation of targets like CCSAP and NEK2 56. Conversely, reduced LIN9 expression in various cancers correlates with tumor suppression through mechanisms involving the retinoblastoma pathway 78. The protein is essential for embryonic development and maintaining genomic stability in stem cells by ensuring proper mitotic progression 12.