GTSE1 (G2 and S-phase expressed 1) is a cytoplasmic microtubule-associated protein with dual roles in cell cycle regulation and disease pathogenesis. Functionally, GTSE1 regulates G2/M phase progression by interacting with microtubule-associated proteins and stabilizing cell cycle inhibitors 1. Mechanistically, GTSE1 maintains p21 stability to inhibit CDK1/2 activity and cooperates with MDM2 to promote p53 degradation, thereby modulating p53-dependent cell cycle checkpoints 1. In cancer, GTSE1 is upregulated across 33 cancer types and promotes tumor growth through ERK/MAPK-mediated regulation of microtubule proteins (tau and stathmin-1), correlating with lymph node metastasis and poor survival in NSCLC 2. GTSE1 expression associates with immunosuppressive tumor microenvironments, elevated tumor mutational burden, and TP53 mutations 3. Beyond cancer, GTSE1 drives pulmonary fibrosis by stabilizing ZEB1, promoting epithelial-to-mesenchymal transition 4, and contributes to liver fibrosis through mechanisms reversible by targeted siRNA delivery 5. Clinically, GTSE1 serves as a pan-cancer prognostic biomarker predictive of poor overall survival and reduced disease-free survival across multiple malignancies including lung adenocarcinoma and clear-cell renal carcinoma 6. These findings position GTSE1 as a promising therapeutic target for cancer immunotherapy and fibrotic disease treatment.