Breast cancer is the most common cancer in women, with more than 1.7 million diagnoses worldwide per annum. Metastatic breast cancer remains incurable, and the presence of triplenegative phenotypes makes targeted treatment impossible. The aryl hydrocarbon receptor (AhR), most commonly associated with the metabolism of xenobiotic ligands, has emerged as a promising biological target for the treatment of this deadly disease. Ligands for the AhR can be classed as exogenous or endogenous and may have agonistic or antagonistic activity. It has been well reported that agonistic ligands may have potent and selective growth inhibition activity in a number of oncogenic cell lines, and one (aminoflavone) has progressed to phase I clinical trials for breast cancer sufferers. In this study, we examine the current state of the literature in this area and elucidate the promising advances that are being made in hijacking the cytosolic-to-nuclear pathway of the AhR for the possible future treatment of breast cancer. K E Y W O R D S aryl hydrocarbon receptor, breast cancer, cancer drugs Abbreviations: 3MC, 3-methylcholanthrene; AF, aminoflavone; AF-1, activation function domain 1; AF-2, activation function domain 2; AhR, aryl hydrocarbon receptor; AhRR, aryl hydrocarbon receptor repressor; AIP, aryl hydrocarbon receptor-interacting protein; ANI-7, (Z)-2-(3,4-dichlorophenyl)-3-(1H-pyrrol-2-yl)acrylonitrile; ARNT, aryl hydrocarbon receptor nuclear translocator; BaP, benzo[a]pyrene; BE, botanical estrogen; bHLH, basic helixloop-helix; βNF, β-naphthoflavone; BRCA1, breast cancer susceptibility gene 1; BRCA2, breast cancer susceptibility gene 2; DNF, dinaphtho[1,2-b;1′2'-d] furan; ER, estrogen receptor; FDA, US Food and Drug Administration; FICZ, 6-formylindolo[3,2-b]carbazole; HAHs, halogenated aromatic hydrocarbons; HER-2, human epidermal growth factor receptor 2; HR, hormone receptor; Hsp90, heat shock protein 90; ITE, 2-(1′H-indole-3′-carbonyl)-thiazole-4carboxylic acid ester; LBD, ligand-binding domain; NLS, nuclear localization sequences; NSAID, nonsteroidal anti-inflammatory drug; p23, prostaglandin E synthase 3; PAHs, polycyclic aromatic hydrocarbons; PAS, period-aryl hydrocarbon receptor nuclear translocator-single minded; PAS-A, period-aryl hydrocarbon receptor nuclear translocator-single minded domain A; PAS-B, period-aryl hydrocarbon receptor nuclear translocator-single minded domain B; PCB, 3,3′,4,4′,5-pentachlorobiphenyl; PPI, proton pump inhibitor; PR, progesterone receptor; PR-A, progesterone receptor form A; PR-B, progesterone receptor form B; PR-C, progesterone receptor form C; ROS, reductive oxidative species; SERMs, selective estrogen receptor modulators; SULT1A1, sulfotransferase 1A1; TAD, transactivation domain; TCDD, 2,3,7,8-tetrachlorodibenzo-p-dioxin; TCDF, 2,3,7,8-tetrachlorodibenzofuran; TNBC, triplenegative breast cancer; Tregs, regulatory T cells; XAP-2, hepatitis B virus X-associated protein 2; XRE, xenobiotic response element.
| BREAST CANCER BACKGROUNDBreast cancer is the most common cancer in women. Of...