CD274 and neoplasm: Association of PD-L1 expression per CPS and response to pembrolizumab was also reported in patients with advanced HNSCC in KEYNOTE-055.7 In addition, we demonstrated a significant association between PD-L1 and PD-L2 expression and found that PD-L2-expressing tumours were more likely to respond to pembrolizumab than non-PD-L2-expressing tumours.