In addition, a ChIP assay conducted in HepG2 and human breast cancer MCF-7 cells treated with 100 nM TCDD showed the induction of various histone modifications, including H3K9Ac, H3K14Ac, H4Ac, and H3K4me3 at the CYP1A1 and CYP1B1 promoters in MCF-7 cells, and at the CYP1A1 promoter region in HepG2 cells only [92, 105]. Here, CYP1A1 is linked to breast cancer.