CD8A and gastric cancer: Regarding PD-1 expression and its association with prognosis, only a few studies have investigated this in EG cancer, and no significant associations have been found besides from one Asian study on gastric cancer by Gao et al. (n = 119) wherein PD-1 expression on CD8+ T cells was found to be an unfavourable prognostic factor, but no other types of immune cells were explored regarding PD-1 expression (26).