TET2 as a Context-Dependent Epigenetic Integrator in Clonal Hematopoiesis, Inflammation, Cancer, and Immunotherapy

Ten-Eleven Translocation 2 (TET2) is an Fe(II)- and α-ketoglutarate-dependent dioxygenase that initiates active DNA demethylation by oxidizing 5-methylcytosine (5mC). Beyond this enzymatic role, TET2 links DNA methylation dynamics with chromatin regulation, cellular metabolism, immune-cell identity, and treatment response in a context-dependent manner. Loss-of-function mutations in TET2 are among the most frequent genetic events in age-related clonal hematopoiesis of indeterminate potential (CHIP), where they are associated with higher risks of hematological malignancies and cardiovascular disease. Human genetic and clinical studies support these associations, while experimental models suggest that mutant hematopoietic clones can promote myeloid inflammatory programs through enhancer remodeling, NLRP3 inflammasome activation, IL-1β/IL-6 signaling, and altered inflammatory resolution. In solid tumors and cancer therapy, TET2 has more variable effects: tumor-cell-intrinsic TET2 loss can contribute to immune escape or therapeutic resistance in selected settings, whereas TET2 disruption in engineered T cells can enhance memory-like persistence and anti-tumor activity, with possible long-term oncogenic risk. This narrative, mechanism-oriented review integrates current evidence on TET2 biology across clonal hematopoiesis, inflammation, cancer, and immunotherapy. We focus on evidence level, cell type, direction of TET2 alteration, and metabolic or therapeutic context as determinants of divergent TET2 functions. TET2 has traditionally been described as a DNA demethylation enzyme, but recent studies increasingly place it among context-dependent regulators of immune and disease phenotypes. The unresolved issue is why TET2 loss, inhibition, activation, or engineered deletion can produce distinct, and sometimes opposing, effects in hematopoietic stem/progenitor cells, macrophages, tumor cells, neurons, microglia, and CAR-T cells. This review uses four variables-cell type, direction of alteration, functional layer, and microenvironmental or therapeutic context-to interpret evidence from CHIP, hematologic malignancies, cardiovascular inflammation, solid tumors, and immunotherapy.