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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 protein by Western Blot analysis of A) 24-hour tocopherol-treated SW480 nuclear extracts: lane 1 – 10 μM γ-tocopherol, lane 2 – 5 μM γ-tocopherol lane 3 – 10 μM α-tocopherol, lane 4 – 5 μM α-tocopherol, lane 5 – 100 μM troglitazone, lane 6 – blank, lane 7-ethanol carrier control.B) Bar graph of densitometries for Western Blot shown in figure 4A.
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Figure 4: Tocopherol upregulation of PPARγ protein by Western Blot analysis of A) 24-hour tocopherol-treated SW480 nuclear extracts: lane 1 – 10 μM γ-tocopherol, lane 2 – 5 μM γ-tocopherol lane 3 – 10 μM α-tocopherol, lane 4 – 5 μM α-tocopherol, lane 5 – 100 μM troglitazone, lane 6 – blank, lane 7-ethanol carrier control.B) Bar graph of densitometries for Western Blot shown in figure 4A.

Mentions: To determine whether there was a concomitant increase in PPARγ protein expression, Western blot analysis was performed at 24 or 48 hours after treatment with 5 μM or 10 μM tocopherols or 100 μM troglitazone. Figure 4a shows the Western Blot of the nuclear fraction of proteins extracted from SW480 cells after 24 hours of tocopherol treatment. Figure 4b is a bar graph representing the densitometry of the gel shown in figure 4a. This demonstrates that γ-tocopherol upregulates PPARγ protein expression in the nucleus where gene regulation occurs. The protein in the cytosolic fraction at this treatment time did not vary with respect to treatment (data not shown). Figure 5a shows the Western blot of a whole cell lysate after 48 hours of 10 μM tocopherols treatment. Figure 5b is a bar graph that represents the densitometry of figure 5a. γ-Tocopherol up regulates protein expression much more efficiently than does α-tocopherol or troglitazone at a concentration of 20 times in excess.


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 protein by Western Blot analysis of A) 24-hour tocopherol-treated SW480 nuclear extracts: lane 1 – 10 μM γ-tocopherol, lane 2 – 5 μM γ-tocopherol lane 3 – 10 μM α-tocopherol, lane 4 – 5 μM α-tocopherol, lane 5 – 100 μM troglitazone, lane 6 – blank, lane 7-ethanol carrier control.B) Bar graph of densitometries for Western Blot shown in figure 4A.
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Related In: Results  -  Collection

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

Figure 4: Tocopherol upregulation of PPARγ protein by Western Blot analysis of A) 24-hour tocopherol-treated SW480 nuclear extracts: lane 1 – 10 μM γ-tocopherol, lane 2 – 5 μM γ-tocopherol lane 3 – 10 μM α-tocopherol, lane 4 – 5 μM α-tocopherol, lane 5 – 100 μM troglitazone, lane 6 – blank, lane 7-ethanol carrier control.B) Bar graph of densitometries for Western Blot shown in figure 4A.
Mentions: To determine whether there was a concomitant increase in PPARγ protein expression, Western blot analysis was performed at 24 or 48 hours after treatment with 5 μM or 10 μM tocopherols or 100 μM troglitazone. Figure 4a shows the Western Blot of the nuclear fraction of proteins extracted from SW480 cells after 24 hours of tocopherol treatment. Figure 4b is a bar graph representing the densitometry of the gel shown in figure 4a. This demonstrates that γ-tocopherol upregulates PPARγ protein expression in the nucleus where gene regulation occurs. The protein in the cytosolic fraction at this treatment time did not vary with respect to treatment (data not shown). Figure 5a shows the Western blot of a whole cell lysate after 48 hours of 10 μM tocopherols treatment. Figure 5b is a bar graph that represents the densitometry of figure 5a. γ-Tocopherol up regulates protein expression much more efficiently than does α-tocopherol or troglitazone at a concentration of 20 times in excess.

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