Gene expression profile in human prostate LNCaP cancer cells by (−) epigallocatechin-3-gallate
Introduction
Green tea is a popular beverage in some parts of the world. In recent years cancer chemopreventive and chemotherapeutic effects of green tea in cell culture systems and in many animal tumor bioassay systems are well described (refs. [1], [2] and references therein). The relevance of these data to human cancer is appreciated for the fact that some studies suggest that green tea consumption by the human population is associated with reduced cancer risk at some body sites (refs. [3], [4] and references therein). Much of its cancer preventive effects appear to be mediated by the polyphenols, most notably (−) epigallocatechin-3-gallate (EGCG) present therein. Our most recent studies have shown that oral infusion of a polyphenolic mixture of green tea to TRAMP mice, a mouse model that emulates human prostate cancer progression, results in remarkable chemopreventive effects [5].
Our earlier studies using tissue culture models showed that EGCG causes dysregulation of cell cycle and apoptosis in human prostate cancer cells [1], [2]. Biological effects of EGCG have also been studied at the cellular and tissue levels by other laboratories where they show the ability of EGCG to modulate endocrine systems [6] and activity of some signaling proteins such as STAT1 ([7] and references therein), and regulate expression of a number of genes ([2] and references therein). Nuclear factors such as Sp-1 and NF-κB have been implicated in the involvement of EGCG regulation [8], [9].
Regulatory events at the molecular level that govern the cancer preventive effect of EGCG remain to be delineated. Here, for the first time, using cDNA microarray technology, we determined the effect of EGCG on enhancement and repression of transcription of genes that have biological functions in cellular regulatory pathways. Our results suggest that transcriptional regulation of some signaling proteins is also part of the regulatory events by which EGCG initiates its anti-proliferative effect in prostate cancer.
Section snippets
Tissue culture
Human prostate carcinoma cells LNCaP were maintained in RPMI medium with 10% fetal bovine serum (Hyclone) and streptomycin and penicillin at 37°C in a humidified chamber. Approximately 1×106 cells per T75 flask were set up in duplicate and grown for 4–5 days to 80% confluence. For the treated cells, EGCG dissolved in water was added in the medium to a final concentration of 12 μM and cells were incubated for an additional 12 h before harvest. Only water was added to the control flask.
Probe preparation and hybridization
Total RNA
A high-throughput approach to reveal gene regulation by EGCG
Molecular regulation underlying the cancer chemoprevention of EGCG in prostate cancer remains unclear. In order to better understand the molecular regulation underlying the anti-proliferative activity of EGCG in prostate cancer, we have utilized cDNA microarray technology to elucidate how EGCG alters program of gene expression in human prostate carcinoma LNCaP cells. We hypothesized that such high-throughput approach should reveal the identity of the regulatory genes involved in the
Acknowledgements
We thank Dr Nihal Ahmad for his careful reading on this manuscript. Steven I. Wang is a NRSA postdoctoral fellow supported by USPHS grant NIH T32CA59366. This study used resources of P-30AR39750 and was supported by USPHS grant CA78809.
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