Cancer Letters

Cancer Letters

Volume 182, Issue 1, 8 August 2002, Pages 43-51
Cancer Letters

Gene expression profile in human prostate LNCaP cancer cells by (−) epigallocatechin-3-gallate

https://doi.org/10.1016/S0304-3835(02)00065-4Get rights and content

Abstract

Green tea is an effective chemopreventive agent in animal tumor bioassays and some human cancers. Much of its cancer preventive effects appear to be mediated by its major polyphenolic constituent (−) epigallocatechin-3-gallate (EGCG). In order to better understand the molecular regulation underlying the anti-proliferative activity of EGCG in prostate cancer, we have utilized cDNA microarray to elucidate how EGCG alters program of gene expression in prostate carcinoma LNCaP cells. Fluorophore-labeled cDNA probes synthesized from the untreated LNCaP cells or the cells treated for 12 h with EGCG (12 μM), a physiologically achievable dose, were competitively hybridized to the microarray that contained a total of 250 kinases and phosphatases genes. Such high-throughput screening has identified a number of EGCG-responsive gene candidates. Of these, we found that EGCG induced a subset of genes that functionally could exhibit inhibitory effects on cell growth. The genes repressed by EGCG mostly belonged to the G-protein signaling network. Interestingly, the protein kinase C-α (PKC-α) form, whose inhibition of expression has been shown to inhibit cell growth in some cancer cells, was selectively repressed by EGCG while the expression of six other PKC isoforms (β, δ, ϵ, μ, η and ζ) was unaffected. These EGCG-responsive genes may provide key insights from which to understand mechanisms of action of other polyphenolic compounds in prostate cancer chemoprevention.

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.

References (23)

  • V.W. Setiawan et al.

    Protective effect of green tea on the risks of chronic gastritis and stomach cancer

    Int. J. Cancer

    (2001)
  • Cited by (65)

    • Polyphenol compounds and PKC signaling

      2016, Biochimica et Biophysica Acta - General Subjects
      Citation Excerpt :

      EGCG competitively inhibited both ATP and phorbol ester binding to PKC [146,147]. In human prostate cancer cells, EGCG down-regulated the expression of PKCα at 12 μM, while the expression of PKCβ, PKCδ, PKCε, PKCμ, PKCη and PKCζ were unaffected [148]. There are multiple studies showing EGCG's involvement in neuroprotection by attenuating PKC signaling pathways.

    View all citing articles on Scopus
    View full text