A New Insight into the Effect of Heme Oxygenase-1 in Progress of Malignant Tumors

Heme Oxygenase-1 (HO-1 ) is a rate-limiting enzyme which catalyzes the oxidation of heme to biologically active products: ferrous iron, carbon monoxide (CO) and biliverdin. The biliverdin converts to bilirubin by biliverdin reductase. There are two isoforms of heme oxygenase. HO-1 is the highly inducible enzyme by heme and various other stimuli including oxidative stress. HO-2 is the constitutively expressed isoform. Since it had been found in 1986, a large number of studies have shown that HO-1 participated in various oxidative stress and inflammatory responses. The studies proved that it has anti-inflammatory, antiapoptotic and cell protective effect. In recent years, studies have shown that HO-1 was highly expressed in a variety of malignant tumors and participated in anti-apoptotic in tumors. Also, it plays a regulatory role in tumor angiogenesis and metastasis. This article is not exhaustive but seeks to summarize what is known about the function of HO-1 in the development of malignant tumors.