PDCD1 and squamous cell carcinoma: PDCD1 and CD274 differentially modulate the prognosis in lung adenocarcinoma or squamous cell carcinoma [31], and rational combinations of first series (CTLA-4, PD-1 and PD-L1) and second series (TIGIT, TIM-3 and LAG-3) of inhibitory receptors might be an optimal immunotherapy approach because of the coexpression or/and compensatory mechanisms in various cancers [32].