Journal Article

Epigallocatechin-3-gallate-induced stress signals in HT-29 human colon adenocarcinoma cells

Chi Chen, Guoxiang Shen, Vidya Hebbar, Rong Hu, Edward D. Owuor and A.-N.Tony Kong

in Carcinogenesis

Volume 24, issue 8, pages 1369-1378
Published in print August 2003 | ISSN: 0143-3334
Published online August 2003 | e-ISSN: 1460-2180 | DOI: http://dx.doi.org/10.1093/carcin/bgg091
Epigallocatechin-3-gallate-induced stress signals in HT-29 human colon adenocarcinoma cells

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Epigallocatechin-3-gallate (EGCG), a major component in green tea polyphenols, has been proven to suppress colonic tumorigenesis in animal models and epidemiological studies. As EGCG is retained in the gastrointestinal tract after oral administration, this pharmacokinetics property gives it the potential to function as a chemopreventive agent against colon cancer. In this study, human colorectal carcinoma HT-29 cells were treated with EGCG to examine the anti-proliferative and pro-apoptotic effects of EGCG, as well as the molecular mechanism underlying these effects. Cell viability assay, nuclear staining, DNA fragmentation, caspase assay, cytochrome c release, DiOC6(3) staining, mitogen-activated protein kinases (MAPK) phosphorylation and trypan blue exclusion assays, were utilized to dissect the signaling pathways induced by EGCG. After 36 h treatment, EGCG inhibited HT-29 cell growth with an IC50 of ∼100 μM. HT-29 cells treated with doses higher than 100 μM showed apparent nuclear condensation and fragmentation, which was confirmed by DNA laddering. Caspase-3 and -9 activation was detected after 12 h treatment, accompanied by mitochondrial transmembrane potential transition and cytochrome c release. Activation of MAPKs was detected as early signaling event elicited by EGCG. Inhibition of c-Jun N-terminal kinase (JNK) pathway showed the involvement of JNK in EGCG-induced cytochrome c release and cell death. EGCG-induced JNK activation was blocked by the antioxidants glutathione and N-acetyl-l-cysteine, suggesting that the cell death signaling was potentially triggered by oxidative stress. In summary, our results from this study suggest that in HT-29 human colon cancer cells (i) EGCG treatment causes damage to mitochondria, and (ii) JNK mediates EGCG-induced apoptotic cell death.

Keywords: DAPI, diamidino-2-phenylindole; DMSO, dimethyl sulfoxide; EGCG, (–)-epigallocatechin-3-gallate; ERK, extracellular signal-regulated protein kinase; GSH, reduced glutathione; JNK, c-Jun N-terminal kinase; MAPKs, mitogen-activated protein kinases; NAC, N-acetyl-l-cysteine

Journal Article.  6716 words.  Illustrated.

Subjects: Clinical Cytogenetics and Molecular Genetics

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