In an orthotopic HCC mouse model, Wang and colleagues reported that PIWIL1-mediated increased secretion of C3 from HCC promoted the infiltration of MDSCs in the tumour microenvironment of HCC via the p38/MAPK pathway, which suppressed T-cell proliferation and facilitated HCC development (60). The gene discussed is PIWIL1; the disease is hepatocellular carcinoma.