C3 and neoplasm: In this study, we demonstrated that deletion of the serine biosynthesis enzyme PHGDH effectively suppressed the immunosuppressive activity of M2-like TAMs and two other different macrophage subsets, Mφ-c2-C1QA and Mφ-c3-APOE, in tumor tissues and attenuated tumor growth in a murine mesothelioma model.