Abstract
Cancer progression is known to be promoted by increased body stress caused by elevated beta-adrenergic and opioidergic nervous system activities. The effects of β2-adrenergic blocker propranolol (PRO) and μ-opioid receptor antagonist naltrexone (NTX) were tested using a preclinical model of human breast cancer. These drugs, individually, and more potently when combined, inhibited the cell growth and progression of breast cancer cells in vitro in cultures, and in vivo in rat xenografts. The antitumor activities of these drugs were associated with direct cell intrinsic effects, including increased cell growth arrest, elevated levels of apoptotic proteins, and reduced production of epithelial-mesenchymal transition factors by the tumor cells, as well as effects on innate immune activation and reduced inflammatory cytokine levels in plasma. These data suggest that the combined treatments of PRO and NTX produce impressive antitumor effects in the preclinical breast cancer model, and thereby may provide a new combinatorial treatment strategy with more clinical treatment modalities.