The presence of catalase in PIWIL1-overexpressing HCC cells could significantly abolish Complement C3 expression (Supplementary Fig. S6b), which indicated that FAO-mediated ROS production is at least partially, if not all, involved as a potential mechanism of Complement C3 activation in PIWIL1-overexpressing HCC cells. The gene discussed is C3; the disease is hepatocellular carcinoma.