PDCD1 and lung adenocarcinoma: While G12C is the most prevalent KRAS mutation, G12D is found in up to 3% in lung adenocarcinoma and is suspected to define a special subtype of KRAS/TP53 mutant tumors with low TMB, reduced PD-L1 expression and immune cell infiltration, so that this co-mutation status might be a negative predictive biomarker for PD-1 ICIs [73].