ACOD1 and neoplasm: Furthermore, p-ERK was significantly elevated in B16 tumor cells cocultured in vitro with WT, but not Irg1–/–, pResMφ (Figure 6E), and treatment of B16 and ID8 tumors with PD98059, a selective inhibitor of the MAPK cascade, significantly inhibited tumor cell proliferation (Supplemental Figures 6, C and D).