Development and characterization of chronic exposure models to polycyclic aromatic hydrocarbon (PAH) complex mixture in estrogen receptor-negative and -positive breast cancer cell lines

Polycyclic aromatic hydrocarbons (PAHs) are a class of carcinogenic endocrine disrupting chemicals (EDCs), produced from incomplete organic fuel combustion. Human exposure is often chronic in response to complex chemical mixtures. Although multiple studies study the effects of single EDCs such as bisphenol A and benzo(a)pyrene on cancer incidence and cell growth characteristics, the mechanistic effects of complex mixtures of EDC/PAH are largely unknown. In order to test the hypothesis that chronic treatment with a physiologically relevant mixture and dose will increase mitogenic signaling resulting in cancer cell proliferation, this study developed two breast cancer cell chronic exposure models to test a PAH mixture derived from a former USEPA Superfund site. Treatment dosage were determined by assessing U.S. adult exposure metabolite data from National Health and Nutrition Examination Survey (NHANES). Following treatment (12 weeks), clonal population of estrogen receptor/ER+MCF- 7-Pmix(3nM) and ER-SUM149-Pmix(6nM) were isolated. The MCF-7-Pmix(3nM) and SUM149-Pmix(6nM) variants had decreased AhR, ER and antioxidant (SOD1) levels. Decrease in AhR corresponded with suppressed target CYP1A1 activity. Additionally, imaging of tumor organoids derived from the SUM149 and SUM149-Pmix(6nM) cells revealed differential morphological characteristics. These signaling and phenotypic effects in the chronic PAH mixture variant cells were not observed in cells treated with acute (24h) treatment at similar doses. In conclusion, this study has led to the generation of PAH-tolerant breast cancer cell lines that can serve as models to further elucidate effects of low dose environmental chemicals on aggressive characteristics of breast cancer progression and resistance to targeted therapeutics like AhR and ER antagonists.