ADRB2 and cancer: β-AR activation promotes the secretion of immunomodulatory cytokines, including IL-8 and IL-6, by cancer cells and myeloid cells.133–135 In addition, activation of β-AR can promote cancer growth via secretion of immunosuppressive factors like VEGF, MMP, and prostaglandin-endoperoxide synthase 2, IL-6, and TGF-β from macrophages.136 The immunosuppression in TME is further driven by a positive feedback mechanism promoted by GM-CSF secreted by carcinoma, resulting in elevated expression of β2-ARs on MDSCs.