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Jan Vondráček, Alois Kozubík, Miroslav Machala, Modulation of Estrogen Receptor-Dependent Reporter Construct Activation and G0/G1–S-Phase Transition by Polycyclic Aromatic Hydrocarbons in Human Breast Carcinoma MCF-7 Cells, Toxicological Sciences, Volume 70, Issue 2, December 2002, Pages 193–201, https://doi.org/10.1093/toxsci/70.2.193
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Abstract
It has been suggested that the estrogenicity of PAHs could contribute to their carcinogenic effects via increased tissue-specific cell proliferation. Both benzo[a]pyrene (BaP) and benz[a]anthracene (BaA) are known to weakly activate estrogen receptor (ER)-dependent reporter constructs. In this study, several other PAHs, including fluorene, fluoranthene, pyrene, chrysene, phenanthrene and anthracene, were found to act as very weak inducers of ER-mediated activity in the MCF-7 cell line stably transfected with a luciferase reporter gene. The effects of PAHs were time-dependent and they were not completely inhibited by antiestrogen ICI 182,780. In addition, BaP and BaA, as well as weakly estrogenic fluoranthene, significantly potentiated the maximum ER-mediated activity of 17β-estradiol. Therefore, the effects of inhibitors of several types of protein kinases known to activate ERα in a ligand-independent manner were investigated. However, neither inhibitors nor inducers of extracellular signal-regulated kinases 1 and 2 (ERK1/2), phosphatidylinositol-3 kinase, protein kinase C, c-Src, or protein kinase A modified ER-mediated activity in this model. Neither estradiol nor BaA activated ERK1/2, two kinases suggested to play significant roles in ER signaling, suggesting that another kinase is involved in the observed phosphorylation of ERα. Similar to 17β-estradiol, BaA stimulated G0/G1–S-phase transition in MCF-7 cells, which was fully suppressed by ICI 182,780. In conclusion, some PAHs can potentiate 17β-estradiol-induced ER activation and stimulate cell cycle entry in vitro. However, their exact mode(s) of action and whether this phenomenon is of in vivo relevance remains to be elucidated.
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