PPARδ deficiency disrupts hypoxia-mediated tumorigenic potential of colon cancer cells

Eunshil Jeong, Jung Eun Koo, Sang Hyeon Yeon, Mi Kyoung Kwak, Daniel H. Hwang, Joo Young Lee

Research output: Contribution to journalArticle

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Abstract

Peroxisome proliferator-activated receptor (PPAR) δ is highly expressed in colon epithelial cells and closely linked to colon carcinogenesis. However, the role of PPARδ in colon cancer cells in a hypoxic tumor microenvironment is not fully understood. We found that expression of the tumor-promoting cytokines, IL-8 and VEGF, induced by hypoxia (<1% O2) and deferoxamine (a hypoxia mimetic) was significantly attenuated in PPARδ-deficient HCT116 colon cancer cells. Consequently, PPARδ-knockout colon cancer cells exposed to hypoxia and deferoxamine failed to stimulate endothelial cell vascularization and macrophage migration/proliferation, whereas wild-type cells were able to induce angiogenesis and macrophage activation in response to hypoxic stress. Hypoxic stress induced transcriptional activation of PPARδ, but not its protein expression, in HCT116 cells. Exogenous expression of p300 potentiated deferoxamine-induced PPARδ transactivation, while siRNA knockdown of p300 abolished hypoxia- and deferoxamine-induced PPARδ transactivation. PPARδ associated with p300 upon hypoxic stress as demonstrated by coimmunoprecipitation studies. PI3K inhibitors or siRNA knockdown of Akt suppressed the PPARδ transactivation induced by hypoxia and deferoxamine in HCT116 cells, leading to decreased expression of IL-8 and VEGF. Collectively, these results reveal that PPARδ is required for hypoxic stress-mediated cytokine expression in colon cancer cells, resulting in promotion of angiogenesis, macrophage recruitment, and macrophage proliferation in the tumor microenvironment. p300 and the PI3K/Akt pathway play a role in the regulation of PPARδ transactivation induced by hypoxic stress. Our results demonstrate the positive crosstalk between PPARδ in tumor cells and the hypoxic tumor microenvironment and provide potential therapeutic targets for colon cancer.

Original languageEnglish (US)
Pages (from-to)926-937
Number of pages12
JournalMolecular Carcinogenesis
Volume53
Issue number11
DOIs
StatePublished - Nov 1 2014

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Peroxisome Proliferator-Activated Receptors
Colonic Neoplasms
Deferoxamine
Transcriptional Activation
Tumor Microenvironment
HCT116 Cells
Macrophages
Interleukin-8
Phosphatidylinositol 3-Kinases
Vascular Endothelial Growth Factor A
Small Interfering RNA
Hypoxia
Colon
Cytokines
Macrophage Activation
Neoplasms
Carcinogenesis
Endothelial Cells
Epithelial Cells

Keywords

  • Colon cancer
  • Hypoxia
  • IL-8
  • Peroxisome proliferator-activated receptor delta
  • VEGF

ASJC Scopus subject areas

  • Cancer Research
  • Molecular Biology
  • Medicine(all)

Cite this

Jeong, E., Koo, J. E., Yeon, S. H., Kwak, M. K., Hwang, D. H., & Lee, J. Y. (2014). PPARδ deficiency disrupts hypoxia-mediated tumorigenic potential of colon cancer cells. Molecular Carcinogenesis, 53(11), 926-937. https://doi.org/10.1002/mc.22144

PPARδ deficiency disrupts hypoxia-mediated tumorigenic potential of colon cancer cells. / Jeong, Eunshil; Koo, Jung Eun; Yeon, Sang Hyeon; Kwak, Mi Kyoung; Hwang, Daniel H.; Lee, Joo Young.

In: Molecular Carcinogenesis, Vol. 53, No. 11, 01.11.2014, p. 926-937.

Research output: Contribution to journalArticle

Jeong, E, Koo, JE, Yeon, SH, Kwak, MK, Hwang, DH & Lee, JY 2014, 'PPARδ deficiency disrupts hypoxia-mediated tumorigenic potential of colon cancer cells', Molecular Carcinogenesis, vol. 53, no. 11, pp. 926-937. https://doi.org/10.1002/mc.22144
Jeong, Eunshil ; Koo, Jung Eun ; Yeon, Sang Hyeon ; Kwak, Mi Kyoung ; Hwang, Daniel H. ; Lee, Joo Young. / PPARδ deficiency disrupts hypoxia-mediated tumorigenic potential of colon cancer cells. In: Molecular Carcinogenesis. 2014 ; Vol. 53, No. 11. pp. 926-937.
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AB - Peroxisome proliferator-activated receptor (PPAR) δ is highly expressed in colon epithelial cells and closely linked to colon carcinogenesis. However, the role of PPARδ in colon cancer cells in a hypoxic tumor microenvironment is not fully understood. We found that expression of the tumor-promoting cytokines, IL-8 and VEGF, induced by hypoxia (<1% O2) and deferoxamine (a hypoxia mimetic) was significantly attenuated in PPARδ-deficient HCT116 colon cancer cells. Consequently, PPARδ-knockout colon cancer cells exposed to hypoxia and deferoxamine failed to stimulate endothelial cell vascularization and macrophage migration/proliferation, whereas wild-type cells were able to induce angiogenesis and macrophage activation in response to hypoxic stress. Hypoxic stress induced transcriptional activation of PPARδ, but not its protein expression, in HCT116 cells. Exogenous expression of p300 potentiated deferoxamine-induced PPARδ transactivation, while siRNA knockdown of p300 abolished hypoxia- and deferoxamine-induced PPARδ transactivation. PPARδ associated with p300 upon hypoxic stress as demonstrated by coimmunoprecipitation studies. PI3K inhibitors or siRNA knockdown of Akt suppressed the PPARδ transactivation induced by hypoxia and deferoxamine in HCT116 cells, leading to decreased expression of IL-8 and VEGF. Collectively, these results reveal that PPARδ is required for hypoxic stress-mediated cytokine expression in colon cancer cells, resulting in promotion of angiogenesis, macrophage recruitment, and macrophage proliferation in the tumor microenvironment. p300 and the PI3K/Akt pathway play a role in the regulation of PPARδ transactivation induced by hypoxic stress. Our results demonstrate the positive crosstalk between PPARδ in tumor cells and the hypoxic tumor microenvironment and provide potential therapeutic targets for colon cancer.

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