Glucocorticoid receptor knockdown decreases the antioxidant protection of B16 melanoma cells: an endocrine system-related mechanism that compromises metastatic cell resistance to vascular endothelium-induced tumor cytotoxicity

• Published in: PloS one 2014-05, Vol.9 (5), p.e96466-e96466
• Main Authors: Obrador, Elena, Valles, Soraya L, Benlloch, María, Sirerol, J Antoni, Pellicer, José A, Alcácer, Javier, Coronado, Javier Alcácer-F, Estrela, José M
• Format: Article
• Language: English
• Subjects: Animals; Antioxidants; Antioxidants (Nutrients); Antioxidants - metabolism; Apoptosis; Biocompatibility; Biology and Life Sciences; Cancer; Cancer metastasis; Cancer prevention; Catalase; Cell adhesion & migration; Cell death; Cell Death - genetics; Cell Line; Cell Line, Tumor; Cell survival; Cell Survival - genetics; Corticosterone; Cytotoxicity; Down-regulation; Down-Regulation - genetics; Endocrine system; Endocrine System - metabolism; Endothelial cells; Endothelial Cells - metabolism; Endothelium; Endothelium, Vascular - metabolism; Glucocorticoids; Glutamate-Cysteine Ligase - genetics; Glutamate-Cysteine Ligase - metabolism; Glutathione; Glutathione - metabolism; Glutathione peroxidase; Glutathione reductase; HEK293 Cells; Hormones; Humans; Interleukin 6; Laboratories; Liver; Liver cancer; Lungs; Male; Medicine and Health Sciences; Melanoma; Melanoma, Experimental - genetics; Melanoma, Experimental - metabolism; Metabolism; Metastases; Metastasis; Mice; Mice, Inbred C57BL; NAD(P)H oxidase; Neoplasm Metastasis - genetics; Neoplasms - genetics; Neoplasms - metabolism; Noradrenaline; Norepinephrine; Oxidases; Oxidative stress; p53 Protein; Pathology; Peroxidase; Physical Sciences; Physiology; Receptors, Glucocorticoid - genetics; Receptors, Glucocorticoid - metabolism; Research and Analysis Methods; Rodents; Signaling; Steroids (Organic compounds); Superoxide dismutase; Superoxides; Survival; Toxicity; Tumor proteins; γ-Glutamylcysteine
• ISSN: 1932-6203; 1932-6203
• DOI: 10.1371/journal.pone.0096466

We previously reported an interorgan system in which stress-related hormones (corticosterone and noradrenaline), interleukin-6, and glutathione (GSH) coordinately regulate metastatic growth of highly aggressive B16-F10 melanoma cells. Corticosterone, at levels measured in tumor-bearing mice, also induces apoptotic cell death in metastatic cells with low GSH content. In the present study we explored the potential role of glucocorticoids in the regulation of metastatic cell death/survival during the early stages of organ invasion. Glucocorticoid receptor (GCR) knockdown decreased the expression and activity of γ-glutamylcysteine synthetase (γ-GCS), the rate-limiting step in GSH synthesis, in metastatic cells in vivo independent of the tumor location (liver, lung, or subcutaneous). The decrease in γ-GCS activity was associated with lower intracellular GSH levels. Nrf2- and p53-dependent down-regulation of γ-GCS was associated with a decrease in the activities of superoxide dismutase 1 and 2, catalase, glutathione peroxidase, and glutathione reductase, but not of the O2--generating NADPH oxidase. The GCR knockdown-induced decrease in antioxidant protection caused a drastic decrease in the survival of metastatic cells during their interaction with endothelial cells, both in vitro and in vivo; only 10% of cancer cells attached to the endothelium survived compared to 90% survival observed in the controls. This very low rate of metastatic cell survival was partially increased (up to 52%) in vivo by inoculating B16-F10 cells preloaded with GSH ester, which enters the cell and delivers free GSH. Taken together, our results indicate that glucocorticoid signaling influences the survival of metastatic cells during their interaction with the vascular endothelium.