[Current situation and future prospect of cytoglobin research].

Cytoglobin was originally discovered from cultured rat hepatic stellate cells by using proteomics analysis in our laboratory in 2001. Cytoglobin is a hexacoordinate globin that is different from the traditional pentacoordinate globins like myoglobin and hemoglobin. Human cytoglobin has about 25% amino acid identity with vertebrate myoglobin and hemoglobin, and 16% with human neuroglobin that is another type of globin present specifically in the nervous system. Besides its function as O2, carbon monoxide, and nitric oxide-binding molecule, cytoglobin exhibits antioxidative properties under hypoxic condition. Recent analyses using clinical samples have indicated that cytoglobin may be a tumor suppressor gene because cytoglobin mRNA expression in cancer tissues is down-regulated through hypermethylation of cytoglobin gene promoter. In this review, the history of cytoglobin research, its current status and future prospects will be discussed.