Genomic and non-genomic effects of glucocorticoids: implications for breast cancer.

Glucocorticoids (GC) are essential steroid hormones for human life. They regulate a series of important processes by binding with three glucocorticoid receptors (GR) and activating genomic and non-genomic pathways. Activated cytoplasmic GR can directly bind DNA and transactivate or transrepress specific genes. Additionally, it can interact with other transcription factors to affect gene expression indirectly. The two membrane GR can interact with mitogen-activated protein (MAP) kinases or activate cAMP and Ca(2+)-dependent pathways, respectively. Glucocorticoids have been widely used as co-treatment of patients with breast cancer (BC) due to reduction of chemotherapy-induced side effects such as nausea, lack of appetite, and inflammation. However, GC may exert a direct effect on tumor response to chemotherapy. In vitro, GC inhibits chemotherapy, radiation and cytokine-induced apoptosis by upregulating antiapoptotic genes and detoxifying proteins. They also upregulate the proto-oncogene c-fms, tumor suppressor gene Nm23, several members of the epidermal growth factor (EGF) signaling pathway and the estrogen sulfotransferase signaling pathway, thus indirectly inhibiting estrogen receptor activation. They inhibit the proangiogenic gene (vascular endothelial growth factor (VEGF); Therefore, they could play a role in reducing angiogenesis. Interestingly, the phosphorylation status of ser-211 in the GR is dependent on the expression of the BRCA1 gene, a tumor suppressor gene that is mutated in the majority of patients with triple negative BC. Some clinical randomized trials have also attempted to address the effect of GC on patients with BC. Thus, in this review we summarize GC mechanisms of action and their participation in several facets of BC.