A3 adenosine receptor is a G protein-coupled receptor belonging to P1 family of purinergic receptors. It is widely distributed in human organs and tissues with various expression levels. In particular, A3 adenosine receptor is highly expressed in several immune cells and cancer cell lines. For this reason its modulation is intensively studied for the involvement in inflammation and cancer. Ligands (agonists and antagonists) presenting high affinity and selectivity for the A3 adenosine receptor are essential for determining the role of such receptor in these pathophysiological conditions and, eventually, for the development of potential drugs for their treatment. In this review we summarize old and new discoveries on therapeutic applications of the A3 adenosine receptor in inflammation and cancer, and highlight the most important agonists and antagonists developed for the A3 adenosine receptor, explicitlythose in clinical trials for the treatment of inflammation and/or cancer.
