Figure 2.

A cartoon illustrating a putative mechanism by which heme fuels cancer cell progression. Heme from blood can be taken up by cells via heme transporters HCP1 and HRG-1. Cancer cells have intensified internal heme synthesis as well as increased heme uptake via heme transporters, whose expression is dramatically elevated in cancer cells, compared to normal cells. As a result, the levels of an array of hemoproteins involving oxygen transport and utilization, such as cytoglobin and cytochrome c, are strongly enhanced. Enhanced levels of hemoproteins lead to intensified oxygen consumption and cellular energy generation, which in turn fuel cancer cell proliferation and migration. HCP1, heme carrier protein 1; HRG-1, heme responsive gene-1; CYP1B1, Cytochrome P450, Family 1, Subfamily B, Polypeptide 1; Cox-2, cyclooxygenase-2; CYGB, cytoglobin; Nuc, nucleus; Mito, mitochondria; Cyto, cytoplasm.