To confirm the role of the AHR in an aggressive cancer phenotype, AHR expression or activity was downregulated in human ER−/PR−/Her2− (triple-negative breast cancer/TNBC) BP1 and Hs578T cell lines by transfection of an AHR repressor plasmid (AHRR), AHR-specific siRNA or by AHR deletion through CRISPR-Cas9-mediated AHR gene editing. The gene discussed is AHRR; the disease is cancer.