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

Abstract

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.

Oxidative stress and antioxidants in the pathophysiology of malignant melanoma

“…Thus, suggesting an interorgan system where stress-related hormones, IL-6 and GSH coordinately regulate metastatic melanoma growth. Furthermore, GR knockdown decreased the expression and activity of γ-GCL in metastatic cells in an in vivo experiment, independently of the tumor location (liver, lung, or subcutaneous) (Obrador et al, 2014). The decrease in γ-GCL activity associated with lower intracellular GSH levels.…”

“…The decrease in γ-GCL activity associated with lower intracellular GSH levels. Nrf2-and p53-dependent down-regulation of γ-GCL associated with a decrease in the activities of SOD1 and SOD2, CAT, GPX and GSR, but not of the O 2˙− generating NADPH oxidase (Obrador et al, 2014). The 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.…”

Pterostilbene Decreases the Antioxidant Defenses of Aggressive Cancer Cells In Vivo: A Physiological Glucocorticoids- and Nrf2-Dependent Mechanism

“…Our group has pointed out the importance of stress-related signals in metastatic melanoma growth ( 51 , 67 ). Glucocorticoids in particular are used at high doses in cancer therapy, in conjunction with other treatments, because they have proapoptotic properties in different cancer cells ( 60 ).…”

“…Glucocorticoids in particular are used at high doses in cancer therapy, in conjunction with other treatments, because they have proapoptotic properties in different cancer cells ( 60 ). Nevertheless, at the pathophysiological levels measured in plasma of tumor-bearing models, glucocorticoids show tumor-promoting activities ( 51 , 70 ). For instance, results in animal models of human breast cancer suggest that glucocorticoids inhibit tumor cell apoptosis ( 70 ).…”

Preventive effect of insect tea primary leaf (Malus sieboldii (Regal) Rehd.) extract on D‐galactose‐induced oxidative damage in mice

“…It is impossible to supplement exogenous GSH or its precursor to affect GSH content in cells. The regulation of γ‐GCS is instrumental in the antioxidant role of GSH (Obrador et al, 2014). NQO1, which is downstream of Nrf2, triggers an antioxidant reaction and plays the role of Nrf2 (Jiang et al., 2017).…”