The NF-κB element was also found as a silencer of the chicken Abcg2 gene due to weakened chicken Abcg2 gene expression, similar to a study reported by Ogretmen and Safa [45], who found that a protein complex consisting of NF-κB exhibited a negative regulatory role on the Abcb1 gene promoter in MCF-7 cells (human breast adenocarcinoma cell line). This evidence concerns the gene ABCG2 and breast adenocarcinoma.