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PPARδ activation acts cooperatively with 3-phosphoinositide-dependent protein kinase-1 to enhance mammary tumorigenesis.

Pollock CB, Yin Y, Yuan H, Zeng X, King S, Li X, Kopelovich L, Albanese C, Glazer RI - PLoS ONE (2011)

Bottom Line: Peroxisome proliferator-activated receptorδ (PPARδ) is a transcription factor that is associated with metabolic gene regulation and inflammation.Transgene expression increased pT308AKT and pS9GSK3β, but did not alter phosphorylation of mTOR, 4EBP1, ribosomal protein S6 and PKCα.GW501516 treatment was accompanied by a distinct metabolic gene expression and metabolomic signature that was not present in untreated animals.

View Article: PubMed Central - PubMed

Affiliation: Department of Oncology, Georgetown University Medical Center, Washington, DC, United States of America.

ABSTRACT
Peroxisome proliferator-activated receptorδ (PPARδ) is a transcription factor that is associated with metabolic gene regulation and inflammation. It has been implicated in tumor promotion and in the regulation of 3-phosphoinositide-dependent kinase-1 (PDK1). PDK1 is a key regulator of the AGC protein kinase family, which includes the proto-oncogene AKT/PKB implicated in several malignancies, including breast cancer. To assess the role of PDK1 in mammary tumorigenesis and its interaction with PPARδ, transgenic mice were generated in which PDK1 was expressed in mammary epithelium under the control of the MMTV enhancer/promoter region. Transgene expression increased pT308AKT and pS9GSK3β, but did not alter phosphorylation of mTOR, 4EBP1, ribosomal protein S6 and PKCα. The transgenic mammary gland also expressed higher levels of PPARδ and a gene expression profile resembling wild-type mice maintained on a diet containing the PPARδ agonist, GW501516. Both wild-type and transgenic mice treated with GW501516 exhibited accelerated rates of tumor formation that were more pronounced in transgenic animals. GW501516 treatment was accompanied by a distinct metabolic gene expression and metabolomic signature that was not present in untreated animals. GW501516-treated transgenic mice expressed higher levels of fatty acid and phospholipid metabolites than treated wild-type mice, suggesting the involvement of PDK1 in enhancing PPARδ-driven energy metabolism. These results reveal that PPARδ activation elicits a distinct metabolic and metabolomic profile in tumors that is in part related to PDK1 and AKT signaling.

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PDK1 transgene expression and analysis of downstream signaling.(A) PCR analysis. DNA was prepared from tail DNA and transgene expression analyzed by PCR using primers specific for the MMTV-PDK1 transgene. The results indicate that MMTV-PDK1 is expressed in four founder lines. (B) IHC analysis indicates that pS241PDK1, pT308AKT and PPARδ were increased in the mammary gland of two iparous MMTV-PDK1 mice (+) vs. a wild-type littermate (−) from founder line 192. Magnification 600×. (C) Western analysis. Mammary gland lysates from two 7 week-old iparous MMTV-PDK1 (+) mice and one wild-type (−) littermate derived from founder line 192 were analyzed by western blotting. Founder line 192 expressed increased pT308AKT, pS9GSK3β and PPARδ. The bar graph represents quantitation of the western blots normalized to either non-phosphorylated protein or βactin levels.
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pone-0016215-g001: PDK1 transgene expression and analysis of downstream signaling.(A) PCR analysis. DNA was prepared from tail DNA and transgene expression analyzed by PCR using primers specific for the MMTV-PDK1 transgene. The results indicate that MMTV-PDK1 is expressed in four founder lines. (B) IHC analysis indicates that pS241PDK1, pT308AKT and PPARδ were increased in the mammary gland of two iparous MMTV-PDK1 mice (+) vs. a wild-type littermate (−) from founder line 192. Magnification 600×. (C) Western analysis. Mammary gland lysates from two 7 week-old iparous MMTV-PDK1 (+) mice and one wild-type (−) littermate derived from founder line 192 were analyzed by western blotting. Founder line 192 expressed increased pT308AKT, pS9GSK3β and PPARδ. The bar graph represents quantitation of the western blots normalized to either non-phosphorylated protein or βactin levels.

Mentions: MMTV-PDK1 transgenic mice were screened for transgene expression by PCR of tail DNA, and four founder lines were identified (Figure 1A). Founder line 192 expressed 8–10-fold higher pS241PDK1 and PDK1 levels vs. wild-type littermates, compared to a 1.5–2-fold change in other founder lines (results not shown), and thus, founder 192 was used for all subsequent studies. The mammary gland of iparous transgenic mice exhibited normal glandular structure and ductal elongation and branching at 3 and 12 weeks of age (Supporting information, Figure S1A). Lactating transgenic mice exhibited strong PDK1 expression (Supporting information, Figure S1B), but no delay in involution vs. wild-type littermates (Supporting information, Figure S1C). There were no differences between transgenic and wild-type mice in their hyperplastic response to medroxyprogesterone stimulation, and transgenic mice did not present with mammary tumors over their lifespan (results not shown).


PPARδ activation acts cooperatively with 3-phosphoinositide-dependent protein kinase-1 to enhance mammary tumorigenesis.

Pollock CB, Yin Y, Yuan H, Zeng X, King S, Li X, Kopelovich L, Albanese C, Glazer RI - PLoS ONE (2011)

PDK1 transgene expression and analysis of downstream signaling.(A) PCR analysis. DNA was prepared from tail DNA and transgene expression analyzed by PCR using primers specific for the MMTV-PDK1 transgene. The results indicate that MMTV-PDK1 is expressed in four founder lines. (B) IHC analysis indicates that pS241PDK1, pT308AKT and PPARδ were increased in the mammary gland of two iparous MMTV-PDK1 mice (+) vs. a wild-type littermate (−) from founder line 192. Magnification 600×. (C) Western analysis. Mammary gland lysates from two 7 week-old iparous MMTV-PDK1 (+) mice and one wild-type (−) littermate derived from founder line 192 were analyzed by western blotting. Founder line 192 expressed increased pT308AKT, pS9GSK3β and PPARδ. The bar graph represents quantitation of the western blots normalized to either non-phosphorylated protein or βactin levels.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC3020974&req=5

pone-0016215-g001: PDK1 transgene expression and analysis of downstream signaling.(A) PCR analysis. DNA was prepared from tail DNA and transgene expression analyzed by PCR using primers specific for the MMTV-PDK1 transgene. The results indicate that MMTV-PDK1 is expressed in four founder lines. (B) IHC analysis indicates that pS241PDK1, pT308AKT and PPARδ were increased in the mammary gland of two iparous MMTV-PDK1 mice (+) vs. a wild-type littermate (−) from founder line 192. Magnification 600×. (C) Western analysis. Mammary gland lysates from two 7 week-old iparous MMTV-PDK1 (+) mice and one wild-type (−) littermate derived from founder line 192 were analyzed by western blotting. Founder line 192 expressed increased pT308AKT, pS9GSK3β and PPARδ. The bar graph represents quantitation of the western blots normalized to either non-phosphorylated protein or βactin levels.
Mentions: MMTV-PDK1 transgenic mice were screened for transgene expression by PCR of tail DNA, and four founder lines were identified (Figure 1A). Founder line 192 expressed 8–10-fold higher pS241PDK1 and PDK1 levels vs. wild-type littermates, compared to a 1.5–2-fold change in other founder lines (results not shown), and thus, founder 192 was used for all subsequent studies. The mammary gland of iparous transgenic mice exhibited normal glandular structure and ductal elongation and branching at 3 and 12 weeks of age (Supporting information, Figure S1A). Lactating transgenic mice exhibited strong PDK1 expression (Supporting information, Figure S1B), but no delay in involution vs. wild-type littermates (Supporting information, Figure S1C). There were no differences between transgenic and wild-type mice in their hyperplastic response to medroxyprogesterone stimulation, and transgenic mice did not present with mammary tumors over their lifespan (results not shown).

Bottom Line: Peroxisome proliferator-activated receptorδ (PPARδ) is a transcription factor that is associated with metabolic gene regulation and inflammation.Transgene expression increased pT308AKT and pS9GSK3β, but did not alter phosphorylation of mTOR, 4EBP1, ribosomal protein S6 and PKCα.GW501516 treatment was accompanied by a distinct metabolic gene expression and metabolomic signature that was not present in untreated animals.

View Article: PubMed Central - PubMed

Affiliation: Department of Oncology, Georgetown University Medical Center, Washington, DC, United States of America.

ABSTRACT
Peroxisome proliferator-activated receptorδ (PPARδ) is a transcription factor that is associated with metabolic gene regulation and inflammation. It has been implicated in tumor promotion and in the regulation of 3-phosphoinositide-dependent kinase-1 (PDK1). PDK1 is a key regulator of the AGC protein kinase family, which includes the proto-oncogene AKT/PKB implicated in several malignancies, including breast cancer. To assess the role of PDK1 in mammary tumorigenesis and its interaction with PPARδ, transgenic mice were generated in which PDK1 was expressed in mammary epithelium under the control of the MMTV enhancer/promoter region. Transgene expression increased pT308AKT and pS9GSK3β, but did not alter phosphorylation of mTOR, 4EBP1, ribosomal protein S6 and PKCα. The transgenic mammary gland also expressed higher levels of PPARδ and a gene expression profile resembling wild-type mice maintained on a diet containing the PPARδ agonist, GW501516. Both wild-type and transgenic mice treated with GW501516 exhibited accelerated rates of tumor formation that were more pronounced in transgenic animals. GW501516 treatment was accompanied by a distinct metabolic gene expression and metabolomic signature that was not present in untreated animals. GW501516-treated transgenic mice expressed higher levels of fatty acid and phospholipid metabolites than treated wild-type mice, suggesting the involvement of PDK1 in enhancing PPARδ-driven energy metabolism. These results reveal that PPARδ activation elicits a distinct metabolic and metabolomic profile in tumors that is in part related to PDK1 and AKT signaling.

Show MeSH
Related in: MedlinePlus