ING1 (Inhibitor of Growth 1) is a tumor suppressor gene located on chromosome 13 that cooperates with p53 in negative regulation of cell growth. ING1 encodes multiple isoforms (p24, p27, p32, p33, and p47) that function through a conserved Plant HomeoDomain (PHD) in the C-terminal region, which recognizes histone H3 trimethylated at lysine 4 (H3K4Me3), enabling its role as a chr13 reader 1. Mechanistically, ING1 modulates p53-dependent transcriptional activation of tumor suppressor genes including p21 and Bax, promotes DNA repair through interaction with proliferating cell nuclear antigen, and regulates histone acetylation via interactions with histone acetyltransferase complexes 2. ING1 mediates growth arrest, senescence, apoptosis, and chemosensitivity, with cell-cycle arrest and apoptosis functions dependent on both ING1 and p53 activity 3. Clinically, ING1 alterations are associated with multiple malignancies. Melanoma patients with ING1 mutations in the PHD domain or SAP30-interacting region show significantly higher mortality, with 50% death rate within 5 years versus 18% in mutation-negative patients, and these mutations specifically impair nucleotide excision repair capacity 4. Reduced ING1 expression occurs frequently in esophagogastric junction adenocarcinomas 5. However, in head and neck squamous cell carcinoma and basal cell carcinoma, ING1 mutations are rare, suggesting tumor suppressor mechanisms vary by cancer type 6, 7.