Abstract
Abstract Melanoma patients experience inferior survival after bio-chemotherapy when their tumors contain numerous cells expressing the inducible isoform of NO synthase (iNOS), and elevated levels of nitrotyrosine, a product derived from nitric oxide (NO). Although several lines of evidence suggest that NO promotes tumor growth and increases resistance to chemotherapy, it is unclear how it shapes these outcomes. Here we demonstrate that modulation of NO-mediated S-nitrosation of cellular proteins is strongly associated with the pattern of response to the anti-cancer agent cisplatin in human melanoma cells in vitro. Cells were shown to express iNOS constitutively, and to generate sustained nanomolar levels of NO intracellularly. Inhibition of NO synthesis or scavenging of NO enhanced cisplatin-induced apoptotic cell death. Additionally, pharmacologic agents disrupting S-nitrosation markedly increased cisplatin toxicity, whereas treatments favoring stabilization of S-nitrosothiols decreased its cytotoxic potency. Activity of the pro-apoptotic enzyme caspase-3 was higher in cells treated with a combination of cisplatin and chemicals that decreased NO/S-nitrisothiols, whereas lower activity resulted from cisplatin combined with stabilization of S-nitrisothiols. Constitutive protein S-nitrosation in cells was detected by analysis with biotin switch and reduction/chemiluminescence techniques. Moreover, intracellular NO concentration increased significantly in cells that survived cisplatin treatment, resulting in augmented S-nitrosation of caspase-3 and prolyl-hydroxylase-2 (PHD2), the enzyme responsible for targeting the pro-survival transcription factor HIF-1α for proteasomal degradation. Because activities of these enzymes are inhibited by S-nitrosation, our data thus indicate that modulation of intrinsic intracellular NO levels substantially affects cisplatin toxicity in melanoma cells. The underlying mechanisms may thus represent potential targets for adjuvant strategies to improve the efficacy of chemotherapy. Citation Format: Luiz C. Godoy, Chase C.T. Anderson, Rajdeep Chowdhury, Laura J. Trudel, Gerald N. Wogan. Melanoma fights cisplatin with NO: S-nitrosation as a mechanism supporting drug-resistance. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 894. doi:10.1158/1538-7445.AM2013-894
Published Version
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