plastochromanol-8 and Colonic-Neoplasms

There is increasing evidence supporting the concept of cancer stem cells (CSCs), which are responsible for the initiation, growth and metastasis of tumors. CSCs are thus considered the target for future cancer therapies. To achieve this goal, identifying potential therapeutic targets for CSCs is essential.. We used a natural product of vitamin E, gamma tocotrienol (gamma-T3), to treat mammospheres and spheres from colon and cervical cancers. Western blotting and real-time RT-PCR were employed to identify the gene and protein targets of gamma-T3 in mammospheres.. We found that mammosphere growth was inhibited in a dose dependent manner, with total inhibition at high doses. Gamma-T3 also inhibited sphere growth in two other human epithelial cancers, colon and cervix. Our results suggested that both Src homology 2 domain-containing phosphatase 1 (SHP1) and 2 (SHP2) were affected by gamma-T3 which was accompanied by a decrease in K- and H-Ras gene expression and phosphorylated ERK protein levels in a dose dependent way. In contrast, expression of self-renewal genes TGF-beta and LIF, as well as ESR signal pathways were not affected by the treatment. These results suggest that gamma-T3 specifically targets SHP2 and the RAS/ERK signaling pathway.. SHP1 and SHP2 are potential therapeutic targets for breast CSCs and gamma-T3 is a promising natural drug for future breast cancer therapy.

Topics: Antioxidants; Blotting, Western; Breast Neoplasms; Cell Death; Cell Line, Tumor; Chromans; Colonic Neoplasms; Extracellular Signal-Regulated MAP Kinases; Female; Flow Cytometry; Humans; Microscopy, Fluorescence; Protein Tyrosine Phosphatase, Non-Receptor Type 11; ras Proteins; Real-Time Polymerase Chain Reaction; Signal Transduction; Spheroids, Cellular; Uterine Cervical Neoplasms; Vitamin E

Colorectal cancer is one of the most serious illnesses among diagnosed cancer. As a new type of anti-cancer composition from tocotrienol-rich fraction of palm oil, γ-tocotrienol is widely used in anti-cancer research. The objectives of this study were to investigate the effects of γ-tocotrienol on human colon cancer SW620 and HCT-8 cells. We showed that treatment with different concentrations of γ-tocotrienol resulted in a dose dependent inhibition of cell growth. Cell death induced by γ-tocotrienol was mediated by a paraptosis-like cell death in SW620 and HCT-8 cells. Real-time RT-PCR and western blot analyses showed that γ-tocotrienol inhibited the expression level of β-catenin, cyclin D1 and c-jun. These data suggest that a paraptosis-like cell death induced by γ-tocotrienol in SW620 cells is associated with the suppression of the Wnt signaling pathway, which offers a novel tool for treating apoptosis-resistance colon cancer.

Topics: Antineoplastic Agents; Caspase 3; Cell Death; Cell Line, Tumor; Cell Proliferation; Chromans; Colonic Neoplasms; Enzyme Activation; Gene Expression Regulation, Neoplastic; Humans; Signal Transduction; Vacuoles; Vitamin E; Wnt Proteins

γ-Tocotrienol, a major component of the tocotrienol-rich fraction of palm oil, has been suggested to have antioxidant and anticancer activity as well as potent chemopreventive effects on tumor cells. In this study, the mechanisms underlying γ-tocotrienol-mediated growth inhibition of human carcinoma HT-29 cells were further investigated, especially in correlation with the involvement of β-catenin/T-cell factor (Tcf) signaling pathway. We found that γ-tocotrienol could strongly suppress the transcriptional activity of β-catenin/Tcf signaling pathway in HT-29 cells. γ-Tocotrienol inhibited the expression level of total β-catenin protein but did not significantly affect the phosphorylated β-catenin level. Meanwhile, γ-tocotrienol down-regulated the protein level of nuclear β-catenin and induced its redistribution to cell membrane. Furthermore, γ-tocotrienol suppressed the expression of downstream target genes such as c-myc, cyclin D1 and survivin. The results demonstrated that γ-tocotrienol-inhibited growth and -induced apoptosis in HT-29 cells were accompanied by significant inhibition of β-catenin/Tcf signaling. Blocking the expression of β-catenin with small interfering RNA significantly suppressed the ability of γ-tocotrienol to reduce viability and induce apoptosis in HT-29 cells. Thus, our data suggested that γ-tocotrienol exerts its anticancer activity through β-catenin/Tcf signaling, and β-catenin is a target for γ-tocotrienol in the Wnt/β-catenin signaling pathway.

Topics: Apoptosis; beta Catenin; Cell Survival; Chromans; Colon; Colonic Neoplasms; Cyclin D1; Down-Regulation; HT29 Cells; Humans; Inhibitor of Apoptosis Proteins; Palm Oil; Phosphorylation; Plant Extracts; Plant Oils; Survivin; TCF Transcription Factors; Vitamin E; Wnt Signaling Pathway

The synergistic actions of atorvastatin (ATST) with gamma-tocotrienol (gamma-TT) and celecoxib (CXIB) were studied in human colon cancer cell lines HT29 and HCT116. The synergistic inhibition of cell growth by ATST and gamma-TT was demonstrated by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay and isobologram analysis. delta-TT exhibited a similar inhibitory action when combined with ATST. Mevalonate and geranylgeranyl pyrophosphate eliminated most of the growth inhibitory effect of ATST, but only marginally decreased that of gamma-TT; whereas farnesyl pyrophosphate and squalene exhibited little effect on the inhibitory action of ATST and gamma-TT, indicating protein geranylgeranylation, but not farnesylation are involved in the inhibition of colon cancer cell growth. Both mevalonate and squalene restored the cellular cholesterol level that was reduced by ATST treatment, but only mevalonate eliminated the cell growth inhibitory effect, suggesting that the cholesterol level in cells does not play an essential role in inhibiting cancer cell growth. Protein level of HMG-CoA reductase increased after ATST treatment, and the presence of gamma-TT attenuated the elevated level of HMG-CoA reductase. ATST also decreased membrane-bound RhoA, possibly due to a reduced level of protein geranylgeranylation; addition of gamma-TT enhanced this effect. The mediation of HMG-CoA reductase and RhoA provides a possible mechanism for the synergistic action of ATST and gamma-TT. The triple combination of ATST, gamma-TT and CXIB showed a synergistic inhibition of cancer cell growth in MTT assays. The synergistic action of these three compounds was also illustrated by their induction of G(0)/G(1) phase cell cycle arrest and apoptosis.

Topics: Atorvastatin; Celecoxib; Cell Cycle; Cell Division; Cell Line, Tumor; Chromans; Colonic Neoplasms; Cyclooxygenase 2 Inhibitors; Drug Synergism; Heptanoic Acids; Humans; Hydroxymethylglutaryl-CoA Reductase Inhibitors; Mevalonic Acid; Polyisoprenyl Phosphates; Pyrazoles; Pyrroles; Sulfonamides; Vitamin E

Tumor necrosis factor-related apoptosis-inducing ligand (TRAIL), a member of the tumor necrosis factor superfamily, is in clinical trials for cancer therapy, but its anticancer potential is limited by the development of resistance. We investigated the ability of tocotrienol (T3), an unsaturated vitamin E present in palm oil, rice bran, barley, oats, and wheat germ, to sensitize tumor cells to TRAIL. Results from esterase staining, colony formation, caspase activation, and sub-G(1) cell cycle arrest revealed that gamma-T3 can sensitize human colon cancer cells to TRAIL. When examined for the mechanism, we found that gamma-T3 significantly downregulated the expression of antiapoptotic proteins (c-IAP2 and Bcl-xL). We also found that gamma-T3, but not tocopherol, induced the expression of the TRAIL receptors death receptor (DR)-4 and DR5. This induction was not cell type specific, as upregulation was also found in pancreatic, kidney, and leukemic cells. Upregulation of DRs by gamma-T3 required the production of reactive oxygen species (ROS), and sequestering of ROS abolished both upregulation of the receptors and potentiation of TRAIL-induced apoptosis. Induction of DRs by gamma-T3 also required activation of extracellular signal-regulated kinase 1 (ERK1), as silencing of ERK1 by specific siRNA abrogated the upregulation of TRAIL receptors. Further, induction of DRs by gamma-T3 required the expression of p53 and Bax, as no induction of the receptors was found in colon cancer cells with deletion of these genes. Overall, our results show that gamma-T3 sensitizes tumor cells to TRAIL by upregulating DRs through the ROS/ERK/p53 pathway and by downregulating cell survival proteins.

Topics: Apoptosis; bcl-2-Associated X Protein; Cell Line, Tumor; Cell Membrane; Cell Survival; Chromans; Colonic Neoplasms; Down-Regulation; Extracellular Signal-Regulated MAP Kinases; Humans; Reactive Oxygen Species; Receptors, Death Domain; TNF-Related Apoptosis-Inducing Ligand; Tumor Suppressor Protein p53; Up-Regulation; Vitamin E

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.. 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.. 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.. 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.

Topics: Anticarcinogenic Agents; Apoptosis; bcl-2-Associated X Protein; Blotting, Western; Caspase 3; Cell Proliferation; Chromans; Colonic Neoplasms; DNA Fragmentation; Dose-Response Relationship, Drug; Enzyme Activation; G1 Phase; HT29 Cells; Humans; Inhibitory Concentration 50; Mitotic Index; Proto-Oncogene Proteins c-bcl-2; Resting Phase, Cell Cycle; Transcription Factor RelA; Vitamin E