Protein-protein interaction network (Figure 5) generated using ToppGenet (https://toppgene.cchmc.org) and complement genes showed close associations with several molecules that either positively (ADM, APOA1, ATP12A, BIRC5, CFB, CHD1, DLG4, GRB2, ITGA2, ITGB1, KRAS, LCK) or negatively (APCS, BRCA2, CASK, CD27, CD81, CD82, DMP1, FCN2, GRK2, LLGL1) regulate the pathogenesis of HCC. The gene discussed is FCN2; the disease is hepatocellular carcinoma.