SOX2 and cancer: First, we found that the luciferase activity driven by the promoters of CD44, Sox2 and ALDH1 did not clearly change in E2-A549 (Additional file 4: Fig. S4A), GFP-Sp1-expressing and Sp1 knockdown A549 cancer cells (Additional file 4: Fig. S4B and C), implying that Sp1-mediated inhibition of EMT-related gene expression may occur through the 3′UTRs of CD44, β-catenin and ALDH1.