HPX and hepatocellular carcinoma: In addition, we carried out pilot studies to isolate heme–HPX-binding proteins (i.e., putative receptors and other biologically relevant HPX-interacting proteins—an “interactome”) using heme–HPX affinity chromatography of whole-cell extracts from three different human cell types: human promyelocytic HL-60 cells, human hepatoma HepG2 cells, and freshly isolated, plated human hepatocytes.