TGFB1 and small cell lung carcinoma: Since TGF-β signal is transduced even in the low expression levels of Smad3 if Smad2 is expressed in H146 cells (Figure 1b), we assumed that TGF-β signal transduction was attenuated in SCLC cells through the decreased expression of TβRII, and therefore, we decided to focus on the roles of TβRII in SCLC in the present study.