C3 and neoplasm: PIWIL1 overexpressed HCC cells attract myeloid suppressor cells (MDSCs) to the tumor microenvironment. MDSCs consumption reduced the proliferation and growth of HCC tumors overexpressed by PIWIL1. Complement C3 induces the secretion of HCC cells through PIWIL1, mediates the interaction between HCC cells and MDSC by activating the P38 MAPK signal in MD38, and then initiates the expression of the immunosuppressive cytokine IL10.