TREM2 and neoplasm: Furthermore, Maf, Atf3, and Hif1a are potential regulators of regulatory myeloid (Mreg) cells, while Hif1a is a potential regulator of tumor-associated macrophages in MCA205 mouse tumors; these two myeloid subpopulations share the expression of Arg1 and Trem2 (Arg1+Trem2+) (46).