EMSA using oligonucleotides of different TCF consensus binding sites in the ABCB1 promoter and protein extracts from K562 and Lucena cells. EMSAs to verify specific binding using the S4 and S5 oligonucleotides and protein extracts from K562 and Lucena cells. The specificity of the DNA-protein complex is demonstrated by competition reactions with 200-fold excess unlabeled oligonucleotide and by supershift assays. SL – Migration of the probe alone. “+C”- Competition reactions with 200-fold excess unlabeled probe. “+Opt” – Competition reactions with 200-fold excess unlabeled wild-type oligonucleotide for the TCF consensus binding site. EXT K – protein extract from K562 cells. EXT L – protein extract from Lucena cells. “+Smad 8”– Supershift reactions using Smad8 antibody. . “+ βcat” – Supershift reactions using β-catenin antibody. The arrows show specific binding.