Imbalance between nitric oxide and superoxide anion induced by uncoupled nitric oxide synthase contributes to human melanoma development.

Melanoma is the most aggressive type of cutaneous tumors due to its metastatic potential and high mortality. Increased levels of reactive oxygen species, including superoxide anion (O2-), and the consequent installation of a pro-oxidant environment are associated with melanoma development. The enzyme nitric oxide synthase (NOS), responsible for the production of nitric oxide (NO), when uncoupled is as a source of O2-, for example by the absence of its cofactor tetrahydrobiopterin (BH4). Western blot analysis showed increased expression of endothelial and inducible NOS in human melanoma cells, altering the stoichiometry between NOS levels and BH4 concentration and together with decreased BH4:BH2 ratio are contributing to NOS uncoupling. The treatment of melanoma cells with exogenous BH4 increased NO concentration and decreased O2- levels, leading to NOS coupling, which in turn reduced cell viability, cell proliferation and the ability of melanoma cells to form melanoma spheroids. Moreover, BH4 level restoration rendered melanoma cells more sensitive to apoptosis, demonstrating the role of dysfunctional NOS in melanoma genesis.

Downregulation of OCLN and GAS1 in clear cell renal cell carcinoma.

Clear cell renal cell carcinoma (ccRCC) is the most common histological subtype of kidney cancer. This carcinoma is histologically characterized by the presence of clear and abundant cytoplasm. In the present study, we sought to identify genes differentially expressed in ccRCC and build a molecular profile of this cancer. We selected genes described in the literature related to cellular differentiation and proliferation. We analyzed the gene and protein expression by quantitative PCR (qPCR) and immunohistochemistry, respectively, and examined possible epigenetic mechanisms that regulate their expression in ccRCC samples and cell lines. Occludin (OCLN) and growth arrest-specific 1 (GAS1) genes were underexpressed in ccRCC, and we report that miR-122 and miR-34a, respectively, may regulate their expression in this cancer. Furthermore, we showed by qPCR and immunohistochemistry that solute carrier family 2 member 1 (SLC2A1) was significantly overexpressed in ccRCC. The set of genes identified in the present study furthers our understanding of the molecular basis and development of ccRCC.