ERK signaling is an important regulator of cancer cell proliferation, as well as migration and invasion in many settings,28 and is activated by TNFα (100 ng/ml) in MC38 and LLC cells (Supplementary Figure 2), and in several other cancer cell lines.29, 30 Inhibition of ERK1/2 with 10 μm U0126 (Cell Signaling Technology) in MC38 and LLC cells suppressed tumor cell proliferation in response to monocyte/macrophage- and granulocyte-conditioned media (Figure 3b). The gene discussed is MAPK3; the disease is cancer.