Inhibition of proliferation and induction of apoptosis by gamma-tocotrienol in human colon carcinoma HT-29 cells

Nutrition. 2009 May;25(5):555-66. doi: 10.1016/j.nut.2008.10.019. Epub 2009 Jan 3.


Objective: gamma-Tocotrienol is a major component of the tocotrienol-rich fraction of palm oil, but there is limited evidence that it has antitumor activity. In particular, the effects of gamma-tocotrienol on human colon carcinoma cells have not been reported. To investigate the chemopreventive effects of gamma-tocotrienol on colon cancer, we examined its capacity to inhibit proliferation and induce apoptosis in HT-29 cells and explored the mechanism underlying these effects.

Methods: We cultured HT-29 cells in the presence of gamma-tocotrienol. The effect of gamma-tocotrienol on cell proliferation was investigated by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay, mitotic index, and colony formation. The cell-cycle distribution was investigated by flow cytometry. We measured apoptosis by nuclear staining, transmission electron microscopy, and DNA fragmentation. Apoptosis-related proteins and the nuclear factor-kappaB p65 protein were determined by western blotting and immunofluorescence.

Results: gamma-Tocotrienol inhibited cell growth and arrested HT-29 cells in G(0)/G(1) phase. The 50% inhibitory concentration was 31.7 micromol/L (48 h). gamma-Tocotrienol-induced apoptosis in HT-29 cells was accompanied by downregulation of Bcl-2, upregulation of Bax, and activation of caspase-3. Furthermore, we found that gamma-tocotrienol reduced the expression level of total nuclear factor-kappaB p65 protein and inhibited its nuclear translocation.

Conclusion: The results indicated that gamma-tocotrienol inhibits cell proliferation and induces apoptosis in HT-29 cells in a time- and dose-dependent manner, and that this process is accompanied by cell-cycle arrest at G(0)/G(1), an increased Bax/Bcl-2 ratio, and activation of caspase-3. Our data also indicated that nuclear factor-kappaB p65 protein may be involved in these effects.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Anticarcinogenic Agents / pharmacology
  • Anticarcinogenic Agents / therapeutic use
  • Apoptosis / drug effects*
  • Blotting, Western
  • Caspase 3 / metabolism
  • Cell Proliferation / drug effects*
  • Chromans / pharmacology
  • Chromans / therapeutic use*
  • Colonic Neoplasms / prevention & control
  • DNA Fragmentation
  • Dose-Response Relationship, Drug
  • Enzyme Activation
  • G1 Phase / drug effects
  • HT29 Cells
  • Humans
  • Inhibitory Concentration 50
  • Mitotic Index
  • Proto-Oncogene Proteins c-bcl-2 / metabolism
  • Resting Phase, Cell Cycle / drug effects
  • Transcription Factor RelA / drug effects
  • Transcription Factor RelA / metabolism*
  • Vitamin E / analogs & derivatives*
  • Vitamin E / pharmacology
  • Vitamin E / therapeutic use
  • bcl-2-Associated X Protein / metabolism


  • Anticarcinogenic Agents
  • BAX protein, human
  • Chromans
  • Proto-Oncogene Proteins c-bcl-2
  • Transcription Factor RelA
  • bcl-2-Associated X Protein
  • Vitamin E
  • plastochromanol 8
  • Caspase 3