We analyzed the promoter methylation of the IRX1 promoter region of five NSCLC cell lines (A549, A427, HCC15, H322, and H358) and 11 SCLC cell lines (HTB171, HTB175, SCLC21H, SCLC22H, SCLC24H, H82, HTB187, H209, H510, H1092, and H1184) by combined bisulfite restriction analysis (Figure 1c,d). This evidence concerns the gene IRX1 and small cell lung carcinoma.