SNS activation can stimulate the generation (Powell 2013) and trafficking of myeloid cells to the tumor microenviroment and significantly influence tumor progression. For example, macrophages and neutrophils found within the tumor microenvironment, are known to stimulate the production of tumor factors that greatly influence tumor progression and metastasis such as pro-inflammatory cytokines, and matrix metalloproteinase enzymes (MMPs) (reviewed Hanahan and Weinberg 2011). Additionally, stress can also reduce the oxidative burst of neutrophils and macrophages,
leading to reduced phagocytic activity (Sa-Rocha 2006).
After a single dose of a short-acting GC, the concentration of neutrophils increases, whereas the lymphocytes, monocytes, eosinophils and basophils in the circulation decrease in number. The increase in neutrophils is due both to the increased influx from the bone marrow and to the demargination and impaired extravasation of neutrophils. The decreased migration of neutrophils from the blood vessels combined with diminished chemotaxis and adherence to vascular endothelium of neutrophils and monocytes results in inhibition of the accumulation of these cells at the site of inflammation. These effects underlie the potent anti-inflammatory properties of GCs. The reduction in circulating lymphocytes, monocytes, eosinophils and basophils is the result of their movement from the vascular bed to lymphoid tissue.