PDCD1 and cancer: In 1957, Macfarlane Burnet wrote ‘The failure in cancer is due not to any weakness of the organism, but to a change in the character of the cells, rendering them in one way or another insusceptible to the normal control’.1 Subsequently, evading immune destruction was identified as a critical hallmark of cancer.2 The 2018 Nobel Prize was awarded to James Allison and Tasuku Honjo for the discovery that cancer cells could exploit programmed cell death protein 1 (PD-1) and cytotoxic T-lymphocyte associated protein 4 (CTLA-4) signalling to avoid immune destruction.3