PDCD1 and lung adenocarcinoma: Additionally, studies have shown that patients with lung adenocarcinoma with TP53 and KRAS co-mutations have a higher programmed cell death-ligand 1 (PD-L1) expression than patients with either TP53 or KRAS mutation, suggesting that this population may benefit from anti-programmed cell death protein 1 (PD-1) immunotherapy (Dong et al., 2017).