Antiestrogenic Activity of Hydroxylated Polychlorinated Biphenyl Congeners Identified in Human Serum

Abstract

Several hydroxylated polychlorinated biphenyls (PCBs) identified in human serum have been synthesized and these include 2,2′,3,4′,5,5′-hexachloro-4-biphenylol; 2,3,3′,4′,5-pentachloro-4-biphenylol; 2′,3,3′,4′,5-pentachloro-4-biphenylol; 2,2′,3,3′,4′,5-hexachloro-4-biphenylol; 2,2′,3,3′,4′,5,5′-heptachloro-4-biphenylol; 2,2′,3,4′,5,5′,6-heptachloro-4-biphenylol; and 2,2′,3′,4,4′,5,5′-heptachloro-3-biphenylol. The hydroxy-PCBs exhibited minimal binding to the rat uterine cytosolic estrogen receptor (ER) and did not induce proliferation of estrogen-responsive MCF-7 human breast cancer cells at concentrations ranging from 10−5to 10−8m. The estrogenic activity of these compounds was further investigated utilizing two estrogen-responsivein vitrobioassays, namely, (i) HeLa cells stably transfected with a Gal4:human ER chimera and a 17-mer-regulated luciferase reporter gene, and (ii) MCF-7 cells transiently transfected with a full-length human ER expression plasmid and a plasmid containing an estrogen-responsive vitellogenin A2 promoter linked to a chloramphenicol acetyl transferase (CAT) reporter gene. None of the hydroxy-PCBs significantly induced luciferase activity in the stably transfected HeLa cells or CAT activity in MCF-7 cells at concentrations as high as 10−5m. The antiestrogenic effects of the hydroxy-PCBs were also investigated using the same bioassays in which the cells were cotreated with 17β-estradiol plus the hydroxy-PCBs. All of the hydroxy-PCB congeners inhibited one or more estrogenic response, and one congener, 2,2′,3,4′,5,5′,6-heptachloro-4-biphenylol, inhibited 17β-estradiol-induced cell proliferation and CAT activity in MCF-7 cells and luciferase activity in HeLa cells.