Journal of Cellular Biochemistry 82:387±398 (2001) Green Tea Extracts Decrease Carcinogen-Induced Mammary Tumor Burden in Rats and Rate of Breast Cancer Cell Proliferation in Culture Kathryn T. Kavanagh, 1,2 Laurie J. Hafer, 1,2 Dong W. Kim, 1,3 Koren K. Mann, 2,4 David H. Sherr, 2,4 Adrianne E. Rogers, 1,2 and Gail E. Sonenshein 2,3 * 1 Department of Pathology and Laboratory Medicine, Boston University School of Medicine, Boston, Massachusetts 02118 2 Program in Research on Women's Health, Boston University School of Medicine, Boston, Massachusetts 02118 3 Department of Biochemistry, Boston University School of Medicine, Boston, Massachusetts 02118 4 Department of Environmental Health, Boston University School of Public Health, Boston, Massachusetts 02118 Abstract Epidemiological evidence suggests tea (Camellia sinensis L.) has chemopreventive effects against various tumors. Green tea contains many polyphenols, including epigallocatechin-3 gallate (EGCG), which possess anti- oxidant qualities. Reduction of chemically induced mammary gland carcinogenesis by green tea in a carcinogen- induced rat model has been suggested previously, but the results reported were not statistically signi®cant. Here we have tested the effects of green tea on mammary tumorigenesis using the 7,12-dimethylbenz(a)anthracene (DMBA) Sprague- Dawley (S-D) rat model. We report that green tea signi®cantly increased mean latency to ®rst tumor, and reduced tumor burden and number of invasive tumors per tumor-bearing animal; although, it did not affect tumor number in the female rats. Furthermore, we show that proliferation and / or viability of cultured Hs578T and MDA-MB-231 estrogen receptor- negative breast cancer cell lines was reduced by EGCG treatment. Similar negative effects on proliferation were observed with the DMBA-transformed D3-1 cell line. Growth inhibition of Hs578T cells correlated with induction of p27 Kip1 cyclin-dependent kinase inhibitor (CKI) expression. Hs578T cells expressing elevated levels of p27 Kip1 protein due to stable ectopic expression displayed increased G1 arrest. Thus, green tea had signi®cant chemopreventive effects on carcinogen-induced mammary tumorigenesis in female S-D rats. In culture, inhibition of human breast cancer cell proliferation by EGCG was mediated in part via induction of the p27 Kip1 CKI. J. Cell. Biochem. 82: 387±398, 2001. ß 2001 Wiley-Liss, Inc. Key words: green tea; breast cancer; EGCG; DMBA; p27 Kip1 The incidence of breast cancer, the second leading cause of death from cancer among women in the United States, has been increas- ing since the 1980s. Interestingly, breast cancer mortality rates are race-dependent. In 1999, the mortality rate of breast cancer per 100,000 Caucasians was 26.0, of African±Americans 31.5, and of Asian±Americans 11.6. Studies show that migration of young Asian women to the United States dramatically increases their risk of breast cancer and mortality from breast cancer [Haenszel and Kurihara, 1968; Kelsey and Gannon, 1990; Ziegler et al., 1993]. In an effort to explain this phenomenon, epidemiolo- gists have put forth various hypotheses, includ- ing differences in diet and environmental ß 2001 Wiley-Liss, Inc. Abbreviations used: GTP, green tea polyphenol; EGCG, epigallocatechin-3 gallate; DMBA, 7,12-dimethylbenz(a) anthracene; S-D, Sprague-Dawley; FBS, fetal bovine serum; MTS, (3-(4,5-dimethylthiazol-2-yl)-5-(3-carboxyme- thoxyphenyl)-2-(4-sulfophenyl)-2H-tetrazolium inner salt; ER, estrogen receptor; CDK, cyclin-dependent kinase; CKI, cyclin-dependent kinase inhibitor; IPTG, isopropyl-beta-D- thiogalactopyranoside. Kathryn T. Kavanagh and Dong W. Kim were the recipients of the Karin Grunebaum Cancer Research Fellowship. Grant sponsor: Department of Army; Grant numbers: DAMD17-94-J-4468, DAMD17-98-1, DAMD17-98-1-8034, DAMD17-99-1-9083, DAMD17-94-J-442194; Grant spon- sor: N.I.H.; Grant number: CA82742. *Correspondence to: Gail E. Sonenshein, Department of Biochemistry, Boston University School of Medicine, 715 Albany Street, Boston, MA 02118. E-mail: gsonensh@bu.edu Received 9 January 2001; Accepted 23 February 2001