Green tea has shown remarkable anti-inflammatory and cancer chemopreventive effects in many animal tumor bioassays, cell culture systems and epidemiological studies. Many of these biological effects of green tea are mediated by epigallocatechin 3-gallate, the major polyphenol present therein. In this study, the differential biological responses of green tea polyphenols (GTP) were examined in normal rat osteoblasts (NRO) vs. human osteosarcoma (MG-63 and Saos-2) cells. The GTP treatment with micromolar concentrations (0.1, 1, 10 and 100 mu M for 24 h) resulted in dose-dependent inhibitions of cell growth and alkaline phosphatase activity, morphological alterations, GO/G1-phase arrest of the cell cycle and induction of apoptosis in both osteosarcoma cells, but not in the NRO. These results suggest that the GTP treatment may be contributed to the differential regulation of cell cycle in normal cells and cancer cells, which can be exploited to craft strategies for the physiological preservation of cells or tissues by GTP. (c) 2005 Elsevier B.V. All rights reserved.