Abstract A37: Modulation of GSTP1 andNQO1 by plant-derived chemopreventive agents in human lung normal, immortalized, and malignant bronchial cells

Abstract

Abstract A37 Modulation of GSTP1 and NQO1 by plant-derived chemopreventive agents in human lung normal, immortalized, and malignant bronchial cells Xiang-Lin Tan 1, 2 Shengli Xiong 1, 2 Miao Shi 1 , Weiguo Han 1, 2 Simon D. Spivack 1, 2, 3, 4, 5 1 Division of Pulmonary Medicine, Albert Einstein College of Medicine, Bronx, NY, 2 Laboratory of Human Toxicology and Molecular Epidemiology, Wadsworth Center, New York State Department of Health, Albany, NY 3 Environmental Health Sciences, School of Public Health, University at Albany, Albany, NY 4 Department of Epidemiology, Albert Einstein College of Medicine, Bronx, NY, 5 Department of Genetics, Albert Einstein College of Medicine, Bronx, NY, Many phytochemicals possess putative cancer-preventive properties. However, none have yet demonstrated clear benefit for lung cancer prevention in clinical trials. In this study, we applied an in vitro system of assay to systematically investigate the influence of putative anti-mutagen, phase II metabolism inducing naturally-occurring mixtures and single compounds, including green tea extracts (GTE), broccoli sprout ITC extracts (ITCs), epigallocatechin gallate (EGCG), sulforaphane (SFN), phenethyl isothiocyanate (PEITC) and benzyl isothiocyanate (BITC), for phase II enzymes GSTP1 and NQO1 in the mRNA and protein level. Primary normal human bronchial epithelial cells (NHBE), immortalized human bronchial epithelial cells (HBEC), and overtly malignant lung adenocarcinoma cells (A549) were incubated with 0.5, 1.0, 5.0 µg/ml mixture or 0.5, 1.0, 2.0 µM single index compounds for 24h, 48h and 7 days, respectively. The proliferation of normal and malignant cells determined by MTT assay was significantly reduced by all studied agents, with relative activities of BITC > PEITC > ITCs > SFN > EGCG > GTE. We then determined the mRNA expression by RNA-specific quantitative RT-PCR previously developed in the laboratory, and the protein expression by conventional Western blot. Overall, the mixtures GTE and ITC increased GSTP1 and NQO1 mRNA levels up to two-fold (1ug/ml) to four-fold (5 ug/ml) increased. However, these mRNA levels were decreased by single compounds PEITC and BITC, in a time and dose dependent manner. EGCG and SFN did not show a consistent effect on the mRNA expression of both GSTP1 and NQO1 genes, although SFN showed two- to four-fold induction activity for NQO1 mRNA expression at 0.5-1.0 uM, uniquely for NHBE. The results were largely confirmed at the protein level, although there was some mRNA-protein discordance. Our results suggest that further in vitro and in vivo screening studies are needed to discover new, more potent phase II-inducing chemopreventive agents for lung cancer, along with mechanistic studies of gene regulation for these key upstream anti-carcinogenesis genes. Such studies are in process in the laboratory. 1 Citation Information: Cancer Prev Res 2008;1(7 Suppl):A37.