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Gamma (gamma) tocopherol upregulates peroxisome proliferator activated receptor (PPAR) gamma (gamma) expression in SW 480 human colon cancer cell lines.

Campbell SE, Stone WL, Whaley SG, Qui M, Krishnan K - BMC Cancer (2003)

Bottom Line: Upregulation of PPARgamma activity is anticarcinogenic through its effects on downstream genes that affect cellular proliferation and apoptosis.We show that the expression of PPARgamma mRNA and protein are increased and these effects are more pronounced with gamma-tocopherol.Further work on other colon cancer cell lines are required to quantitate differences in the ability of these forms of vitamin E to induce apoptosis, suppress cell proliferation and act as PPAR ligands as well as determine their effects in conjunction with other chemopreventive agents.

View Article: PubMed Central - HTML - PubMed

Affiliation: Division of Hematology-Oncology, Department of Internal Medicine, East Tennessee State University and James H, Quillen VA Medical Center, Johnson City, TN 37614, USA. campbese@etsu.edu

ABSTRACT

Background: Tocopherols are lipid soluble antioxidants that exist as eight structurally different isoforms. The intake of gamma-tocopherol is higher than alpha-tocopherol in the average US diet. The clinical results of the effects of vitamin E as a cancer preventive agent have been inconsistent. All published clinical trials with vitamin E have used alpha-tocopherol. Recent epidemiological, experimental and molecular studies suggest that gamma-tocopherol may be a more potent chemopreventive form of vitamin E compared to the more-studied alpha-tocopherol. Gamma-tocopherol exhibits differences in its ability to detoxify nitrogen dioxide, growth inhibitory effects on selected cancer cell lines, inhibition of neoplastic transformation in embryonic fibroblasts, and inhibition of cyclooxygenase-2 (COX-2) activity in macrophages and epithelial cells. Peroxisome proliferator activator receptor gamma (PPARgamma) is a promising molecular target for colon cancer prevention. Upregulation of PPARgamma activity is anticarcinogenic through its effects on downstream genes that affect cellular proliferation and apoptosis. The thiazolidine class of drugs are powerful PPARgamma ligands. Vitamin E has structural similarity to the thiazolidine, troglitazone. In this investigation, we tested the effects of both alpha and gamma tocopherol on the expression of PPARgamma mRNA and protein in SW 480 colon cancer cell lines. We also measured the intracellular concentrations of vitamin E in SW 480 colon cancer cell lines.

Results: We have discovered that the alpha and gamma isoforms of vitamin E upregulate PPARgamma mRNA and protein expression in the SW480 colon cancer cell lines. gamma-Tocopherol is a better modulator of PPARgamma expression than alpha-tocopherol at the concentrations tested. Intracellular concentrations increased as the vitamin E concentration added to the media was increased. Further, gamma-tocopherol-treated cells have higher intracellular tocopherol concentrations than those treated with the same concentrations of alpha-tocopherol.

Conclusion: Our data suggest that both alpha and gamma tocopherol can upregulate the expression of PPARgamma which is considered an important molecular target for colon cancer chemoprevention. We show that the expression of PPARgamma mRNA and protein are increased and these effects are more pronounced with gamma-tocopherol. Gamma-tocopherol's ability to upregulate PPARgamma expression and achieve higher intracellular concentrations in the colonic tissue may be relevant to colon cancer prevention. We also show that the intracellular concentrations of gamma-tocopherol are several fold higher than alpha-tocopherol. Further work on other colon cancer cell lines are required to quantitate differences in the ability of these forms of vitamin E to induce apoptosis, suppress cell proliferation and act as PPAR ligands as well as determine their effects in conjunction with other chemopreventive agents. Upregulation of PPARgamma by the tocopherols and in particular by gamma-tocopherol may have relevance not only to cancer prevention but also to the management of inflammatory and cardiovascular disorders.

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Tocopherol upregulation of PPARγ mRNA expression detected by QPCR after 24 hours of treatment with 10 μM tocopherol. A) Relative copy number of a representative QPCR AT 10 μM tocopherol concentration. B) Fold increase data of the representative QPCR data shown in figure 3A. C) Average fold increase data of three independent experiments at 10 μM tocopherol concentration. * shows sample statistical difference compared to the vehicle-treated.
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Figure 3: Tocopherol upregulation of PPARγ mRNA expression detected by QPCR after 24 hours of treatment with 10 μM tocopherol. A) Relative copy number of a representative QPCR AT 10 μM tocopherol concentration. B) Fold increase data of the representative QPCR data shown in figure 3A. C) Average fold increase data of three independent experiments at 10 μM tocopherol concentration. * shows sample statistical difference compared to the vehicle-treated.

Mentions: To determine whether α-tocopherol or γ-tocopherol could upregulate PPARγ mRNA expression, total RNA was isolated from SW480 colon cancer cells at 24 hours after treatment with α-tocopherol, γ-tocopherol (5 μM or 10 μM) or 100 μM troglitazone (positive control). The total RNA was reverse transcribed to cDNA. Changes in the mRNA expression were quantified using the cDNA and QPCR reaction with SYBR green. Figure 2a shows the differences in mRNA expression as a result of treatment with 5 μM tocopherols compared to the vehicle and troglitazone-treated cells. Figure 2b represents the 5 μM data normalized to the vehicle treatment and expressed as a fold increase in PPARγ copy number. Figure 2c is an average of three treatments at 5 μM normalized to the vehicle treatment and expressed as a fold increase in PPARγ copy number. Figure 3a shows the differences in mRNA expression as a result of treatment with 10 μM tocopherols compared to the vehicle and troglitazone-treated cells. Figure 3b represents the 10 μM data normalized to the vehicle treatment and expressed as a fold increase in PPARγ copy number. Figure 3c is an average of three treatments at 10 μM normalized to the vehicle treatment and expressed as a fold increase in PPARγ copy number. The results presented here (Figures 2a,2b, 3a and 3b) are representative of three independent experiments at the stated tocopherol concentrations. The relative copy number varies from cell population to cell population. According to Gupta, [17], the highest level of receptor expression in colonic tissue occur in postmitotic cells. The data represented in figure 2a and figure 3a are representative of two different cell populations seeded and treated on different days. For this reason we have averaged the fold increase data at each concentration (Figures 2b and 3b). The error bars in figure 2c and 3c are the Standard Error of the Mean for the three experiments. HCT-116 cells have been tested at each of these tocopherol concentrations with similar results (data not shown). α-Tocopherol and γ-tocopherol can upregulate mRNA expression when compared to the vehicle. However, at both concentrations tested, γ-tocopherol was more efficient at upregulation of PPARγ mRNA.


Gamma (gamma) tocopherol upregulates peroxisome proliferator activated receptor (PPAR) gamma (gamma) expression in SW 480 human colon cancer cell lines.

Campbell SE, Stone WL, Whaley SG, Qui M, Krishnan K - BMC Cancer (2003)

Tocopherol upregulation of PPARγ mRNA expression detected by QPCR after 24 hours of treatment with 10 μM tocopherol. A) Relative copy number of a representative QPCR AT 10 μM tocopherol concentration. B) Fold increase data of the representative QPCR data shown in figure 3A. C) Average fold increase data of three independent experiments at 10 μM tocopherol concentration. * shows sample statistical difference compared to the vehicle-treated.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC222914&req=5

Figure 3: Tocopherol upregulation of PPARγ mRNA expression detected by QPCR after 24 hours of treatment with 10 μM tocopherol. A) Relative copy number of a representative QPCR AT 10 μM tocopherol concentration. B) Fold increase data of the representative QPCR data shown in figure 3A. C) Average fold increase data of three independent experiments at 10 μM tocopherol concentration. * shows sample statistical difference compared to the vehicle-treated.
Mentions: To determine whether α-tocopherol or γ-tocopherol could upregulate PPARγ mRNA expression, total RNA was isolated from SW480 colon cancer cells at 24 hours after treatment with α-tocopherol, γ-tocopherol (5 μM or 10 μM) or 100 μM troglitazone (positive control). The total RNA was reverse transcribed to cDNA. Changes in the mRNA expression were quantified using the cDNA and QPCR reaction with SYBR green. Figure 2a shows the differences in mRNA expression as a result of treatment with 5 μM tocopherols compared to the vehicle and troglitazone-treated cells. Figure 2b represents the 5 μM data normalized to the vehicle treatment and expressed as a fold increase in PPARγ copy number. Figure 2c is an average of three treatments at 5 μM normalized to the vehicle treatment and expressed as a fold increase in PPARγ copy number. Figure 3a shows the differences in mRNA expression as a result of treatment with 10 μM tocopherols compared to the vehicle and troglitazone-treated cells. Figure 3b represents the 10 μM data normalized to the vehicle treatment and expressed as a fold increase in PPARγ copy number. Figure 3c is an average of three treatments at 10 μM normalized to the vehicle treatment and expressed as a fold increase in PPARγ copy number. The results presented here (Figures 2a,2b, 3a and 3b) are representative of three independent experiments at the stated tocopherol concentrations. The relative copy number varies from cell population to cell population. According to Gupta, [17], the highest level of receptor expression in colonic tissue occur in postmitotic cells. The data represented in figure 2a and figure 3a are representative of two different cell populations seeded and treated on different days. For this reason we have averaged the fold increase data at each concentration (Figures 2b and 3b). The error bars in figure 2c and 3c are the Standard Error of the Mean for the three experiments. HCT-116 cells have been tested at each of these tocopherol concentrations with similar results (data not shown). α-Tocopherol and γ-tocopherol can upregulate mRNA expression when compared to the vehicle. However, at both concentrations tested, γ-tocopherol was more efficient at upregulation of PPARγ mRNA.

Bottom Line: Upregulation of PPARgamma activity is anticarcinogenic through its effects on downstream genes that affect cellular proliferation and apoptosis.We show that the expression of PPARgamma mRNA and protein are increased and these effects are more pronounced with gamma-tocopherol.Further work on other colon cancer cell lines are required to quantitate differences in the ability of these forms of vitamin E to induce apoptosis, suppress cell proliferation and act as PPAR ligands as well as determine their effects in conjunction with other chemopreventive agents.

View Article: PubMed Central - HTML - PubMed

Affiliation: Division of Hematology-Oncology, Department of Internal Medicine, East Tennessee State University and James H, Quillen VA Medical Center, Johnson City, TN 37614, USA. campbese@etsu.edu

ABSTRACT

Background: Tocopherols are lipid soluble antioxidants that exist as eight structurally different isoforms. The intake of gamma-tocopherol is higher than alpha-tocopherol in the average US diet. The clinical results of the effects of vitamin E as a cancer preventive agent have been inconsistent. All published clinical trials with vitamin E have used alpha-tocopherol. Recent epidemiological, experimental and molecular studies suggest that gamma-tocopherol may be a more potent chemopreventive form of vitamin E compared to the more-studied alpha-tocopherol. Gamma-tocopherol exhibits differences in its ability to detoxify nitrogen dioxide, growth inhibitory effects on selected cancer cell lines, inhibition of neoplastic transformation in embryonic fibroblasts, and inhibition of cyclooxygenase-2 (COX-2) activity in macrophages and epithelial cells. Peroxisome proliferator activator receptor gamma (PPARgamma) is a promising molecular target for colon cancer prevention. Upregulation of PPARgamma activity is anticarcinogenic through its effects on downstream genes that affect cellular proliferation and apoptosis. The thiazolidine class of drugs are powerful PPARgamma ligands. Vitamin E has structural similarity to the thiazolidine, troglitazone. In this investigation, we tested the effects of both alpha and gamma tocopherol on the expression of PPARgamma mRNA and protein in SW 480 colon cancer cell lines. We also measured the intracellular concentrations of vitamin E in SW 480 colon cancer cell lines.

Results: We have discovered that the alpha and gamma isoforms of vitamin E upregulate PPARgamma mRNA and protein expression in the SW480 colon cancer cell lines. gamma-Tocopherol is a better modulator of PPARgamma expression than alpha-tocopherol at the concentrations tested. Intracellular concentrations increased as the vitamin E concentration added to the media was increased. Further, gamma-tocopherol-treated cells have higher intracellular tocopherol concentrations than those treated with the same concentrations of alpha-tocopherol.

Conclusion: Our data suggest that both alpha and gamma tocopherol can upregulate the expression of PPARgamma which is considered an important molecular target for colon cancer chemoprevention. We show that the expression of PPARgamma mRNA and protein are increased and these effects are more pronounced with gamma-tocopherol. Gamma-tocopherol's ability to upregulate PPARgamma expression and achieve higher intracellular concentrations in the colonic tissue may be relevant to colon cancer prevention. We also show that the intracellular concentrations of gamma-tocopherol are several fold higher than alpha-tocopherol. Further work on other colon cancer cell lines are required to quantitate differences in the ability of these forms of vitamin E to induce apoptosis, suppress cell proliferation and act as PPAR ligands as well as determine their effects in conjunction with other chemopreventive agents. Upregulation of PPARgamma by the tocopherols and in particular by gamma-tocopherol may have relevance not only to cancer prevention but also to the management of inflammatory and cardiovascular disorders.

Show MeSH
Related in: MedlinePlus