Hematopoietic Tet2 inactivation enhances the response to checkpoint blockade immunotherapy

Somatic mutations inactivating TET2 are among the most common drivers of clonal hematopoiesis (CH). While TET2 inactivation is associated with monocyte-derived inflammation and improved chimeric antigen-receptor-T cell function, its impact on immunotherapy response is unknown. In murine models, hematopoietic Tet2 mutation enhanced the immune checkpoint blockade (ICB) response via the combined presence of phagocytes, CD4 and CD8 T cells. Mechanistically, in Tet2-mutant tumor-infiltrating leukocytes (TILs), ICB preferentially restricted cell states linked to tumor progression while inducing anti-tumor states. Tet2-mutant monocytes activated costimulatory programs, while Tet2-mutant T cells showed enhanced T cell memory signatures, alongside decreased exhaustion and regulatory phenotypes. This murine data was clinically relevant, since tumors from colorectal cancer and melanoma patients with TET2 driver mutation-CH (TET2-CH) showed enhanced immune infiltration, inflammation, and T cell activation. In melanoma patients treated with ICB, TET2-CH was associated with 6-fold greater odds of clinical benefit. Collectively, our data establishes that hematopoietic Tet2 inactivation primes leukocytes for anti-tumor states associated with immunotherapy response and provides a potential biomarker for personalized therapy.