MT1M (metallothionein 1M) is a cysteine-rich metal-binding protein encoded on chromosome 16 as one of eight MT1 isoforms 1. Primary function involves heavy metal detoxification and intracellular zinc homeostasis through high-affinity binding of heavy metals and zinc ions. MT1M is subject to autophagic degradation in cancer cells, where E2F4-mediated autophagy regulates zinc distribution within autophagosomes 2. MT1M acts as a tumor suppressor across multiple cancer types. In gastric cancer, MT1M expression is downregulated, and low expression correlates with poor prognosis and chemotherapy resistance 3. MT1M overexpression inhibits cancer cell proliferation, induces apoptosis, and enhances chemosensitivity by targeting GLI1 and modulating the Hedgehog pathway 3. Similarly, in breast cancer, MT1M downregulation promotes cell viability, migration, and invasion 4. Clinically, MT1M shows diagnostic value in hepatocellular carcinoma (HCC). Aberrant MT1M promoter methylation in serum distinguishes HCC from chr16 hepatitis B and controls with 94.6% specificity, and methylation status correlates with tumor size and metastatic risk 5. MT1M functions as a predictive biomarker for HCC development in patients with dermatomyositis 6. In hepatoma cells, MT1M activates NF-κB-dependent transcription and influences cell cycle regulation 7.