Estrogenic and antiproliferative properties of soy sapogenols in human breast cancer cells in vitro § J.C. Rowlands a, *, M.A. Berhow b , T.M. Badger a a Arkansas Children’s Nutrition Center and Department of Pediatrics, University of Arkansas for Medical Sciences, Little Rock, Arkansas, USA b United States Department of Agriculture, Agricultural Research Service National Center for Agricultural Utilization Research, Peoria, Illinois, USA Accepted 22 April 2002 Abstract Two soy sapogenols, soyasapogenol A (SA) and soyasapogenol B (SB) were tested for their estrogenic activities in estrogen responsive MCF-7 or estrogen-insensitive MDA-MB-231 (MDA) human breast cancer cells. SB and SA had differential actives on cell proliferation with 10 mm SB being growth inhibitory to MDA cells with no significant effect at any concentration on MCF-7 cells. SA also inhibited MDA cell proliferation at 10 mm, but at this same dose stimulated a 2.5-fold increase in MCF-7 prolifera- tion. SA (0.1–10 mm) induced pS2 mRNA levels and the induction was blocked by co-treatment of cells with the anti-estrogen ICI 182,780. SA also induced the formation of an ER–ERE DNA complex measured by electrophoretic mobility shift assay. In sum- mary, these results show that soyasapogenol A is estrogenic, whereas soyasapogenol B is growth inhibitory. # 2002 Elsevier Science Ltd. All rights reserved. Keywords: Soy; Estrogen receptor; Estrogen; Anti-estrogen; Gene expression; Human breast cancer cells 1. Introduction Diet is considered an important factor in cancer risk. Plant proteins and/or their associated protein bound factors and chemicals (phytochemicals) are reported to reduce the risk of some cancers. For example, dietary soy protein isolate prevented 7,12-dimethylbenz[a]an- thracene (DMBA)-induced mammary cancers in adult female Sprague–Dawley rats (Hakkak et al., 2000). Soy contains numerous phytochemicals including iso- flavones, phytic acid, phytosterols and saponins (Barnes et al., 1995). Much attention has been focused on the isoflavones such as genistin that are estrogenic in their aglycone form (genistein), and some studies have repor- ted that genistein consumption stimulates mammary gland differentiation and prevents DMBA-induced mammarycancer(Lamartiniereetal.,1995;Murrilletal., 1996; Fritz et al., 1998). Less attention has been given to the other soy photochemicals such as the saponins, even thoughtheyresembletheisoflavonesinthattheyarealso reported to possess antineoplastic activity (Kennedy, 1995;RaoandSung1995;Berhowetal.,2000). Saponins have been reported to possess several health beneficial activities including hypocholesterolemic (Oakenfull and Sidhu, 1990), immune-stimulatory (Chavali et al., 1987, 1988; Chavali and Campbell 1987a,b; Wu et al., 1990) and anticarcinogenic (Oda- shima et al., 1979; Sati et al., 1985; Konoshima and Lee, 1986; Abe et al., 1987; Ota et al., 1987; Tokuda et al., 1991; Yu et al., 1994). The mechanism for the choles- terol-lowering effects has been attributed to saponin precipitation of intestinal cholesterol thereby preventing absorption (Oakenfull and Sidhu, 1990). Saponins induce cell membrane disruption and/or induction of apoptosis in vitro (Khalil and El-Adaway, 1994; Kim et al., 1999a,b) and this may be responsible for their cyto- toxic and anticarcinogenic activities. The soy saponins are divided into three groups, based on the structure of the aglycone moiety, the A, B and E 0278-6915/02/$ - see front matter # 2002 Elsevier Science Ltd. All rights reserved. PII: S0278-6915(02)00181-3 Food and Chemical Toxicology 40 (2002) 1767–1774 www.elsevier.com/locate/foodchemtox § Presented in part at Experimental Biology, Orlando, FL, USA, 2001. Abbreviations: DMBA, 7,12-dimethylbenz[a]anthracene; DMEM, Dulbecco’s modified Eagle’s medium; DMSO, dimethyl sulfoxide; EMSA, electrophoretic mobility shift assay; ERE, ER response ele- ment; FBS, fetal bovine serum; SA, soyasapogenol A; SB, soyasapo- genol B. * Corresponding author at: Burdock Group, 780 US Hwy 1, Suite 300, Vero Beach, FL 32962, USA. Tel.: +1-561-561-3900; fax: +1- 561-561-3908. E-mail address: crowlands@burdockgroup.com (J.C. Rowlands).