CD274 and gastric cancer: In the KEYNOTE-012 phase IB trial (Clinical Trials.gov Identifier; NCT01848834) [21], patients with advanced gastric cancer were screened for PD-L1 expression (positivity was defined as PD-L1 expression in ≥ 1 % of cells in tumor nests or according to stromal staining using IHC with the 22C3 PD-L1 antibody), and 41 % were PD-L1-positive cases.