Anti-proliferative and differentiation-inducing activities of the green tea catechin epigallocatechin-3-gallate (EGCG) on the human eosinophilic leukemia EoL-1 cell line H.L. Lung a , W.K. Ip a , C.K. Wong b , N.K. Mak c , Z.Y. Chen a , K.N. Leung a, * a Department of Biochemistry, The Chinese University of Hong Kong, Shatin, Hong Kong, China b Department of Chemical Pathology, The Chinese University of Hong Kong, Shatin, Hong Kong, China c Department of Biology, The Hong Kong Baptist University, Kowloon, Hong Kong, China Received 14 May 2002; accepted 17 July 2002 Abstract A novel approach for the treatment of leukemia is the differentiation therapy in which immature leukemia cells are induced to attain a mature phenotype when exposed to differentiation inducers, either alone or in combinations with other chemotherapeutic or chemopreventive drugs. Over the past decade, numerous studies indicated that green tea catechins (GTC) could suppress the growth and induce apoptosis on a number of human cancer cell lines. However, the differentiation-inducing activity of GTC on human tumors remains poorly understood. In the present study, the effect of the major GTC epigallocatechin-3-gallate (EGCG) on the proliferation and differentiation of a human eosinophilc leukemic cell line, EoL-1, was examined. Our results showed that EGCG suppressed the proliferation of the EoL-1 cells in a dose-dependent manner, with an estimated IC 50 value of 31.5 AM. On the other hand, EGCG at a concentration of 40 AM could trigger the EoL-1 cells to undergo morphological differentiation into mature eosinophil-like cells. Using RT-PCR and flow cytometry, it was found that EGCG upregulated the gene and protein expression of two eosinophil-specific granule proteins, the major basic protein (MBP) and eosinophil peroxidase (EPO), in EoL-1 cells. Taken together, our findings suggest that EGCG can exhibit anti- leukemic activity on a human eosinophilic cell line EoL-1 by suppressing the proliferation and by inducing the differentiation of the leukemia cells. D 2002 Elsevier Science Inc. All rights reserved. Keywords: Differentiation; Green tea catechin; Epigallocatechin-3-gallate (EGCG); Human eosinophilic leukemia EoL-1 cells 0024-3205/02/$ - see front matter D 2002 Elsevier Science Inc. All rights reserved. PII:S0024-3205(02)02236-1 * Corresponding author. Tel.: +852-26096802; fax: +852-26035123. E-mail address: knleung@cuhk.edu.hk (K.N. Leung). www.elsevier.com/locate/lifescie Life Sciences 72 (2002) 257 – 268