SPP1 and cancer: A recent study of human patients identified macrophage polarity defined by the expression ratio of the genes CXCL9 and SPP1 (but not by conventional M1 and M2 markers) as having a strong prognostic association with survival in human cancers, as well as associating with response to aPD1.57 To test whether our MC38 system recapitulated this association found in humans, we examined bulk transcriptomes of 23 MC38 tumors from responder and non-responder strain CCF1 mice treated with aPD1 or isotype control using the single-dose protocol previously described.