A positive correlation between PD-L1 and phosphorylated Smad2 expression was found in non-small-cell lung cancer (NSCLC), in which TGF-β1 was found to upregulate PD-L1 gene transcription in a Smad2-dependent manner rather than Smad4 [19]. This evidence concerns the gene SMAD4 and non-small cell lung carcinoma.