Cytokines released from tumor-residing cells including tumor cell–derived IL-4, IL-10, CCL2, CCL3, CCL4, and CSF1; Treg-derived IL-10; B cell–produced immunoglobulins; Th2-derived IL-4 and IL-13; and MSC-derived MFG-E8 promote the polarization into a protumor phenotype. The gene discussed is CSF1; the disease is neoplasm.