Studies on lung cancer demonstrated that the amount of oxygen-utilizing hemoproteins, such as cytoglobin, cytochrome c, cytochrome P450 family 1 subfamily B member 1 (CYP1B1) and prostaglandin-endoperoxide synthase 2 (COX2) are higher in tumor cells as compared to normal cells and that, at least for cytoglobin and cytochrome c, their levels depend on the rate of heme synthesis and cellular heme content (46). Here, CYCS is linked to lung cancer.