CD274 and cancer: Using the Phosphonet dataset (http://www.phosphonet.ca (accessed on 12 December 2021)), we observed that several PD-L1 residues may undergo phosphorylation; screening studies of cancer phospho-proteome by mass spectrometry indicated that the intracellular serine 283 (S283) residue is a key phosphorylation site in PD-L1 (https://www.phosphosite.org/proteinAction.action?id=19198&showAllSites=true (accessed on 12 December 2021)).