Vitamin D-binding protein-derived macrophage-activating factor induces apoptosis and phagocytosis in breast cancer cells (Lopes et al., 2012; Thyer et al., 2013), whereas C3 is the foremost player in innate immune response manipulated in conventional chemotherapy (Michlmayr et al., 2010; Bauer et al., 2019; Shu et al., 2020). Here, C3 is linked to breast cancer.