Individual cell clones with confirmed loss of PD-L1 expression (Supplementary Fig. 3b–e) showed comparable proliferative capacity to wild-type cells in vitro (Supplementary Fig. 3f,g), and readily formed tumours when injected subcutaneously into immune-deficient hosts (Fig. 2d, Supplementary Fig. 4a). Here, CD274 is linked to neoplasm.