Novel estrogenic action of the pesticide residue beta-hexachlorocyclohexane in human breast cancer cells.
The estrogenic action of some persistent organochlorine pesticide residues may play a role in the progression of hormonally responsive tumors of the breast and uterus. The prototypical xenoestrogen o,p'-dichlorodiphenyltrichloroethane (o,p'-DDT) acts by binding and activating the estrogen receptor (ER). The present study focuses attention on the mechanisms through which another organochlorine compound, beta-hexachlorocyclohexane (beta-HCH), exerts estrogen-like effects in human breast cancer cells. Both o,p'DDT and beta-HCH stimulated proliferation in a dose-dependent manner in the ER-positive cell lines MCF-7 and T47D but not in the ER-negative lines MDA-MB231, MDA-MB468, and HS578T. Both compounds produced an increase in the steady state level of pS2 mRNA in MCF-7 cells. These responses were equal in magnitude to the maximal effect of estradiol, and they were inhibited by inclusion of the antiestrogen ICI164384. On the other hand, when tested in a competitive binding assay, beta-HCH did not displace 17beta-[3H]estradiol from the ER even at a concentration that was 40,000-fold higher than the tracer steroid. Furthermore, nuclear retention of the ER during homogenization procedures was induced by a 2- or 24-h treatment of MCF-7 cells with o,p'-DDT and 17beta-estradiol but not by treatment with beta-HCH; this indicates that beta-HCH nether activates the ER, nor is it converted intracellularly to an ER ligand. Transcriptional activation by beta-HCH occurs in estrogen-responsive GH3 rat pituitary tumor cells transfected with a luciferase reporter construct driven by a complex 2500-bp portion of the PRL gene promoter; this trans-activation response is inhibited by inclusion of ICI164384. However, beta-HCH is ineffective in stimulating a reporter construct driven only by a consensus estrogen response element and a minimal promoter derived from the herpes simplex virus thymidine kinase gene. Thus, beta-HCH cannot act on a simple, single estrogen response element; rather, it requires the combinatorial regulation found in a complex promoter. These data are consistent with the notion that beta-HCH stimulation of cell proliferation and gene expression is ER dependent, but its action is not through the classic pathway of binding and activating the ER. beta-HCH may represent a new class of xenobiotic that produces estrogen-like effects through nonclassic mechanisms and, therefore, may be of concern with regard to breast and uterine cancer risk.
Steinmetz
R
R
Department of Obstetrics and Gynecology, Indiana University School of Medicine, Indianapolis 46202, USA.
Young
P C
PC
Caperell-Grant
A
A
Gize
E A
EA
Madhukar
B V
BV
Ben-Jonathan
N
N
Bigsby
R M
RM
D000230:Adenocarcinoma / Q000473:pathology*; D000818:Animals; D001667:Binding, Competitive; D001943:Breast Neoplasms / Q000473:pathology*; D004305:Dose-Response Relationship, Drug; D004958:Estradiol / Q000031:analogs & derivatives / Q000494:pharmacology; D004965:Estrogen Antagonists / Q000494:pharmacology; D004967:Estrogens; D005260:Female; D015972:Gene Expression Regulation, Neoplastic / Q000187:drug effects*; D001556:Hexachlorocyclohexane / Q000494:pharmacology*; D006801:Humans; D008297:Male; D051379:Mice; D008819:Mice, Nude; D009363:Neoplasm Proteins / Q000096:biosynthesis* / Q000235:genetics; D009368:Neoplasm Transplantation; D009376:Neoplasms, Hormone-Dependent / Q000473:pathology*; D010573:Pesticide Residues / Q000494:pharmacology*; D010911:Pituitary Neoplasms / Q000473:pathology; D053284:Polyunsaturated Alkamides; D011401:Promoter Regions, Genetic / Q000187:drug effects; D014176:Protein Biosynthesis; D011506:Proteins / Q000235:genetics; D012333:RNA, Messenger / Q000096:biosynthesis; D012334:RNA, Neoplasm / Q000096:biosynthesis; D051381:Rats; D011960:Receptors, Estrogen / Q000187:drug effects / Q000502:physiology; D011993:Recombinant Fusion Proteins / Q000096:biosynthesis; D014158:Transcription, Genetic / Q000187:drug effects; D000071163:Trefoil Factor-1; D014407:Tumor Cells, Cultured / Q000187:drug effects; D025521:Tumor Suppressor Proteins
D004965:Estrogen Antagonists; D004967:Estrogens; D009363:Neoplasm Proteins; D010573:Pesticide Residues; D053284:Polyunsaturated Alkamides; D011506:Proteins; D012333:RNA, Messenger; D012334:RNA, Neoplasm; D011960:Receptors, Estrogen; D011993:Recombinant Fusion Proteins; C051838:TFF1 protein, human; D000071163:Trefoil Factor-1; D025521:Tumor Suppressor Proteins; D004958:Estradiol; D001556:Hexachlorocyclohexane; C051781:ICI 164384; C023888:beta-hexachlorocyclohexane