BMP4 and non-small cell lung carcinoma: In order to validate our hypothesis that SUV39H1 regulates the expression of BMP4 in NSCLC cells by suppressing Smad9 expression, Smad9 was silenced in A549 and H460 cells and the knockdown efficiency was evaluated by RT-qPCR (Fig. 6f, Additional file 3: Fig. 3e) and western blot analysis (Fig. 6g, Additional file 3: Figure S3F).