title: Correlation of in vitro and in vivo growth suppression of MCF-7 human breast cancer by 2,3,7,8-tetrachlorodibenzo-p-dioxin.
abstract: The purpose of this study was to compare the effect of 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) on the in vitro and in vivo 17 beta-estradiol (E2)-dependent growth of MCF-7 human breast cancer cells. In culture, a major component of postconfluent growth of MCF-7 cells is E2 dependent. In vivo, MCF-7 cells fail to grow as xenografts without exogenous E2 support. Thus the effect of TCDD on postconfluent MCF-7 growth in culture was compared with its effect on MCF-7 xenograft growth in immunosuppressed mice. A concentration of 10(-9) M E2 was optimal for supporting postconfluent growth of MCF-7 cells in culture into multicellular aggregates (foci) on a monolayer background. The 50% inhibitory dose of TCDD under these conditions was 3 x 10(-10) M, while E2-dependent focus development was completely inhibited by 10(-8) M TCDD. Weekly i.p. administration of TCDD (5 micrograms/kg) to mice bearing MCF-7 tumor xenografts resulted in inhibition of the tumor growth rate for the first 2 weeks, followed by recovery to the control growth rate during the third week. These recovered tumors were found to retain estrogen-dependent growth as shown by second generation transplantation studies. The p.o. route of TCDD administration yielded a similar 2-week transient suppression of growth with a concentration of 8 micrograms TCDD/kg body weight but only a 1-week growth rate latency with a 2-microgram/kg body weight dose. A single 5-micrograms/kg dose given 1 day after implantation was virtually noninhibitory. These results indicate that TCDD suppression of estrogen-dependent MCF-7 human breast cancer cell growth in vitro was predicative of a similar growth suppression of MCF-7 solid tumor xenografts in vivo. However, additional host-related factors must be involved in vivo, since suppression of tumor growth is transient. These studies provide a basis for future in vivo investigations of TCDD endocrine toxicity by using the MCF-7 tumor as a surrogate estrogen-responsive human organ and to examine the efficacy of TCDD and related Ah receptor-mediated compounds in the management of human estrogen-dependent breast cancer.
authors.affiliation: Wadsworth Center for Laboratories and Research, New York State Department of Health, Albany 12201-0509.
authors.forename: J F
authors.initials: JF
authors.lastname: Gierthy
authors.forename: J A
authors.initials: JA
authors.lastname: Bennett
authors.forename: L M
authors.initials: LM
authors.lastname: Bradley
authors.forename: D S
authors.initials: DS
authors.lastname: Cutler
mesh_terms: D000230:Adenocarcinoma / Q000188:drug therapy* / Q000473:pathology*; D000284:Administration, Oral; D000818:Animals; D001943:Breast Neoplasms / Q000188:drug therapy* / Q000473:pathology*; D002455:Cell Division / Q000187:drug effects; D004195:Disease Models, Animal; D004781:Environmental Exposure; D004958:Estradiol / Q000494:pharmacology; D004965:Estrogen Antagonists / Q000494:pharmacology*; D005260:Female; D006801:Humans; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D008811:Mice, Inbred DBA; D009376:Neoplasms, Hormone-Dependent / Q000188:drug therapy* / Q000473:pathology*; D000072317:Polychlorinated Dibenzodioxins / Q000494:pharmacology*; D013268:Stimulation, Chemical; D014183:Transplantation, Heterologous
chemical_list: D004965:Estrogen Antagonists; D000072317:Polychlorinated Dibenzodioxins; D004958:Estradiol