C4A and cancer: Interestingly, C4A and MDK are previously characterized circulating biomarkers for HCC [1] whereas SERPINC1 (also prioritized as a potential biomarker in our study) is an interacting partner of AFP, C8A, F2, UPB1, F10, AHSG, APOA5, APOC3 and IGFBP1 (involved in cancer progression) (Fig 4).