DDIT4 (DNA damage inducible transcript 4) is a stress-responsive regulator of cell growth and survival that functions primarily through inhibition of mammalian target of rapamycin complex 1 (mTORC1) 1. The protein mediates cellular responses to multiple stressors including DNA damage, hypoxia, and metabolic stress by suppressing mTORC1 activity, thereby controlling cell proliferation and apoptosis 2. DDIT4 acts as a licensing mechanism during injury-induced metaplasia, allowing only DNA-damage-free cells to proliferate through controlled mTORC1 reactivation; loss of DDIT4 results in increased mitosis despite unrepaired DNA damage and enhanced tumorigenesis risk 2. In cancer cachexia, disrupted methionine metabolism leads to DNA hypomethylation and excessive DDIT4 expression, driving muscle atrophy through mTORC1 inhibition; methionine supplementation restores DDIT4 silencing and alleviates atrophy 3. DDIT4 also protects against H. pylori-induced gastric metaplasia by metabolic regulation of ferroptosis, with DDIT4 loss increasing ferroptosis markers and metaplastic lesions 4. Additionally, in triple-negative breast cancer, DDIT4 mRNA stabilization promotes autophagy and chemoresistance, suggesting therapeutic potential for DDIT4 targeting 5. DDIT4 expression correlates with prognosis in acute myeloid leukemia, where KMT2D regulates DDIT4 as a negative mTOR pathway regulator 6.