As a DNA methylcytosine dioxygenase, Tet2 is instrumental in DNA demethylation, by which maintains the expression of immunosuppressive genes comprising ARG1, MGL2, KLF4 and interferon regulatory factor 4 (IRF4) in TAMs and inhibits the antitumor function of tumor infiltrating T cells, resulting in significant tumor promotion in melanoma [33]. The gene discussed is IRF4; the disease is melanoma.