NT5E and neoplasm: Genetic ablation or pharmacologic inhibition of A2A receptors restores the antitumour activity of T cells, suggesting potential strategy for the cancer immunotherapy.267,268 Given that ectoenzymes are largely responsible for the production of adenosine in tumour microenvironment, suppression of these ectoenzymes (for example of CD73) has been shown to have considerable effects to enhance antitumour immune responses, and CD73-null mice are resistant to tumourigenesis.269,270 Adenosine seems to regulate cancer development in a dose-dependent manner in this resembling ATP.