Fig. 2

Effects of complement activation on the TME. Activation of the complement system inside tumors releases complement components, such as C1q, C3a, and C5a, into the TME and promotes tumor carcinogenesis. These complement components induce the recruitment of immune cells, including TAMs, TANs, MDSCs, Tregs and DCs, into the tumor. These cells differentiate into tumor-promoting phenotypes and contribute to tumor progression at the following different levels: cell proliferation, angiogenesis, EMT, invasion and metastasis and the inhibition of antitumor immunity. Immunosuppressive cytokines, such as Arg-1, IL-10 and TGF-β, are also released. Imbalanced complement activation and inflammation also promote cancer metastasis into the brain, lung and liver by degrading the ECM and disrupting tissue barriers