CTLA-4- and PD-1 expressing T-cells play a critical role in maintaining self-tolerance but are also responsible for non-responsiveness to tumour antigens. Cancer cells escape from im-mune surveillance by expressing immune checkpoint receptors. The goal of immune check-point inhibitor therapies is not to activate the immune system to attack particular targets on tumour cells, but rather to remove inhibitory pathways that block effective antitumour T cell responses.