Tumor Suppressor Roles of the Denitrosylase GSNOR

Nitric oxide (NO) is a gaseous pleiotropic molecule that can both induce irreversible oxidative damages and modulate physiological signal transductions by transient protein modifications, the most important of which is the S-nitrosylation of cysteine residues. Being noxious and healthy, the role of NO in cancer is seemingly contradictory, as at low concentrations it mediates tumor growth and proliferation whereas at high concentrations it promotes apoptosis and cancer growth inhibition. However, it is becoming evident that when endogenously produced, such as upon inducible nitric oxide synthase (NOS) activation, NO acts to sustain tumorigenesis. Similarly, although less explored, defects and deficiency in the denitrosylating enzyme S-nitrosoglutathione reductase (GSNOR) have been associated with the development and malignancy of liver and breast cancers, suggesting a primary role for NO signaling-that is, S-nitrosylation, being deeply involved in neoplastic transformation and progression. In this review, we summarize past and recent evidence on the role of S-nitrosylation and GSNOR in different processes that contribute to cell transformation when deregulated, such as DNA damage repair, energetic metabolism, and cell death. We also outline possible S-nitrosylation-targeted proteins that might contribute to tumorigenesis, and, finally, we speculate on the role of GSNOR in regulating the oncogenic effects induced downstream.