Phosphorylation of Smad2 and induction of SMAD7, one of the direct targets of TGF-β, were examined in human SCLC cells (H146, H82, H209 and H345) and in NSCLC cells (A549 and H441) with immunoblotting and quantitative real-time reverse transcription-PCR (qRT-PCR) analyses. Here, SMAD2 is linked to small cell lung carcinoma.