C4A and neoplasm: Further proteomic analysis of the biotinylated cytokines enriched by streptavidin magnetic beads (Fig. 5f, g) showed that complement proteins C1QA, C1QB, C1QC, C3, and C4 were all enriched in ascites-treated cells (Fig. 5h), demonstrating the direct crosstalk between components in the complement pathway and ascitic tumor cells.