Limits...
Resveratrol regulates the PTEN/AKT pathway through androgen receptor-dependent and -independent mechanisms in prostate cancer cell lines.

Wang Y, Romigh T, He X, Orloff MS, Silverman RH, Heston WD, Eng C - Hum. Mol. Genet. (2010)

Bottom Line: In contrast, resveratrol directly binds epidermal growth factor receptor (EGFR) rapidly inhibiting EGFR phosphorylation, resulting in decreased AKT phosphorylation, in an AR-independent manner.Thus, resveratrol may act as potential adjunctive treatment for late-stage hormone refractory prostate cancer.More importantly, for the first time, our study demonstrates the mechanism by which AR regulates PTEN expression at the transcription level, indicating the direct link between a nuclear receptor and the PI3K/AKT pathway.

View Article: PubMed Central - PubMed

Affiliation: Genomic Medicine Institute, Cleveland Clinic, 9500 Euclid Avenue, Cleveland, OH 44195, USA.

ABSTRACT
The tumor suppressor gene PTEN (phosphatase and tensin homolog deleted on chromosome 10) and the androgen receptor (AR) play important roles in tumor development and progression in prostate carcinogenesis. Among many functions, PTEN negatively regulates the cytoplasmic phosphatidylinositol-3-kinase/AKT anti-apoptotic pathway; and nuclear PTEN affects the cell cycle by also negatively regulating the MAPK pathway via cyclin D. Decreased PTEN expression is correlated with prostate cancer progression. Over-expression of AR and upregulation of AR transcriptional activity are often observed in the later stages of prostate cancer. Recent studies indicate that PTEN regulates AR activity and stability. However, the mechanism of how AR regulates PTEN has never been studied. Furthermore, resveratrol, a phytoalexin enriched in red grapes, strawberries and peanuts, has been shown to inhibit AR transcriptional activity in prostate cancer cells. In this study, we use prostate cancer cell lines to test the hypothesis that resveratrol inhibits cellular proliferation in both AR-dependent and -independent mechanisms. We show that resveratrol inhibits AR transcriptional activity in both androgen-dependent and -independent prostate cancer cells. Additionally, resveratrol stimulates PTEN expression through AR inhibition. In contrast, resveratrol directly binds epidermal growth factor receptor (EGFR) rapidly inhibiting EGFR phosphorylation, resulting in decreased AKT phosphorylation, in an AR-independent manner. Thus, resveratrol may act as potential adjunctive treatment for late-stage hormone refractory prostate cancer. More importantly, for the first time, our study demonstrates the mechanism by which AR regulates PTEN expression at the transcription level, indicating the direct link between a nuclear receptor and the PI3K/AKT pathway.

Show MeSH

Related in: MedlinePlus

Resveratrol inhibits AR transcriptional activity. (A) LNCaP and C4-2 cells were co-transfected with plasmids expressing hARE-Luc and Renilla-Luc and treated with DMSO (control) and different concentrations of resveratrol for 48 h before lysis of cells for luciferase assay. Data represent mean luciferase firefly luminescence + SD (n = 3) normalized to Renilla-luminescence. Right panel shows western blots demonstrating increasing concentrations of resveratrol associated with decreasing PSA expression in LNCaP cells. Parenthetically, at the 1 µm concentration, resveratrol may have slightly increased AR transcriptional activity and PSA expression in LNCaP cells. (B) LNCaP and (C) C4-2 cells were transfected with plasmids expressing hARE-Luc and Renilla-Luc and treated as indicated. AR activity was then measured by luciferase assay (*P < 0.005). (D) LNCaP cells were treated with DMSO (control) or different concentrations of resveratrol. Growth rate of the cells was assessed by the MTT assay over a period of 5 days. Note that resveratrol and Casodex induced cell growth inhibition and the two-drug combination had the same effect as resveratrol by itself (*P < 0.01).
© Copyright Policy - creative-commons
Related In: Results  -  Collection

License 1 - License 2
getmorefigures.php?uid=PMC2957324&req=5

DDQ354F2: Resveratrol inhibits AR transcriptional activity. (A) LNCaP and C4-2 cells were co-transfected with plasmids expressing hARE-Luc and Renilla-Luc and treated with DMSO (control) and different concentrations of resveratrol for 48 h before lysis of cells for luciferase assay. Data represent mean luciferase firefly luminescence + SD (n = 3) normalized to Renilla-luminescence. Right panel shows western blots demonstrating increasing concentrations of resveratrol associated with decreasing PSA expression in LNCaP cells. Parenthetically, at the 1 µm concentration, resveratrol may have slightly increased AR transcriptional activity and PSA expression in LNCaP cells. (B) LNCaP and (C) C4-2 cells were transfected with plasmids expressing hARE-Luc and Renilla-Luc and treated as indicated. AR activity was then measured by luciferase assay (*P < 0.005). (D) LNCaP cells were treated with DMSO (control) or different concentrations of resveratrol. Growth rate of the cells was assessed by the MTT assay over a period of 5 days. Note that resveratrol and Casodex induced cell growth inhibition and the two-drug combination had the same effect as resveratrol by itself (*P < 0.01).

Mentions: Next, we analyzed the effect of resveratrol on AR in both androgen-dependent LNCaP and androgen-independent C4-2 cells. We transfected each cell with a reporter plasmid, containing a promoter comprising six copies of androgen receptor response elements (AREs) tagged with a luciferase reporter gene. Luciferase assays showed that AR transcriptional activity was inhibited by resveratrol at both 10 and 50 µm concentrations in both LNCaP and C4-2 cells, while low concentrations of resveratrol (1 µm) slightly, but not significantly, increased AR activity in LNCaP (Fig. 2A). The expression of PSA transcript, which is regulated by AR, was inhibited by resveratrol (Supplementary Material, Fig. S1). Also, resveratrol inhibited the endogenous PSA protein expression at the two higher doses in both LNCaP and C4-2 cells (Fig. 2A, insert). DHT significantly increased AR transcriptional activity in both LNCaP and C4-2 cells, an effect that was abrogated by resveratrol (Fig. 2B and C). In contrast, an anti-AR drug bicalutamide (Casodex) inhibited AR activity, and resveratrol further enhanced this inhibitory effect (Fig. 2B and C).Figure 2.


Resveratrol regulates the PTEN/AKT pathway through androgen receptor-dependent and -independent mechanisms in prostate cancer cell lines.

Wang Y, Romigh T, He X, Orloff MS, Silverman RH, Heston WD, Eng C - Hum. Mol. Genet. (2010)

Resveratrol inhibits AR transcriptional activity. (A) LNCaP and C4-2 cells were co-transfected with plasmids expressing hARE-Luc and Renilla-Luc and treated with DMSO (control) and different concentrations of resveratrol for 48 h before lysis of cells for luciferase assay. Data represent mean luciferase firefly luminescence + SD (n = 3) normalized to Renilla-luminescence. Right panel shows western blots demonstrating increasing concentrations of resveratrol associated with decreasing PSA expression in LNCaP cells. Parenthetically, at the 1 µm concentration, resveratrol may have slightly increased AR transcriptional activity and PSA expression in LNCaP cells. (B) LNCaP and (C) C4-2 cells were transfected with plasmids expressing hARE-Luc and Renilla-Luc and treated as indicated. AR activity was then measured by luciferase assay (*P < 0.005). (D) LNCaP cells were treated with DMSO (control) or different concentrations of resveratrol. Growth rate of the cells was assessed by the MTT assay over a period of 5 days. Note that resveratrol and Casodex induced cell growth inhibition and the two-drug combination had the same effect as resveratrol by itself (*P < 0.01).
© Copyright Policy - creative-commons
Related In: Results  -  Collection

License 1 - License 2
Show All Figures
getmorefigures.php?uid=PMC2957324&req=5

DDQ354F2: Resveratrol inhibits AR transcriptional activity. (A) LNCaP and C4-2 cells were co-transfected with plasmids expressing hARE-Luc and Renilla-Luc and treated with DMSO (control) and different concentrations of resveratrol for 48 h before lysis of cells for luciferase assay. Data represent mean luciferase firefly luminescence + SD (n = 3) normalized to Renilla-luminescence. Right panel shows western blots demonstrating increasing concentrations of resveratrol associated with decreasing PSA expression in LNCaP cells. Parenthetically, at the 1 µm concentration, resveratrol may have slightly increased AR transcriptional activity and PSA expression in LNCaP cells. (B) LNCaP and (C) C4-2 cells were transfected with plasmids expressing hARE-Luc and Renilla-Luc and treated as indicated. AR activity was then measured by luciferase assay (*P < 0.005). (D) LNCaP cells were treated with DMSO (control) or different concentrations of resveratrol. Growth rate of the cells was assessed by the MTT assay over a period of 5 days. Note that resveratrol and Casodex induced cell growth inhibition and the two-drug combination had the same effect as resveratrol by itself (*P < 0.01).
Mentions: Next, we analyzed the effect of resveratrol on AR in both androgen-dependent LNCaP and androgen-independent C4-2 cells. We transfected each cell with a reporter plasmid, containing a promoter comprising six copies of androgen receptor response elements (AREs) tagged with a luciferase reporter gene. Luciferase assays showed that AR transcriptional activity was inhibited by resveratrol at both 10 and 50 µm concentrations in both LNCaP and C4-2 cells, while low concentrations of resveratrol (1 µm) slightly, but not significantly, increased AR activity in LNCaP (Fig. 2A). The expression of PSA transcript, which is regulated by AR, was inhibited by resveratrol (Supplementary Material, Fig. S1). Also, resveratrol inhibited the endogenous PSA protein expression at the two higher doses in both LNCaP and C4-2 cells (Fig. 2A, insert). DHT significantly increased AR transcriptional activity in both LNCaP and C4-2 cells, an effect that was abrogated by resveratrol (Fig. 2B and C). In contrast, an anti-AR drug bicalutamide (Casodex) inhibited AR activity, and resveratrol further enhanced this inhibitory effect (Fig. 2B and C).Figure 2.

Bottom Line: In contrast, resveratrol directly binds epidermal growth factor receptor (EGFR) rapidly inhibiting EGFR phosphorylation, resulting in decreased AKT phosphorylation, in an AR-independent manner.Thus, resveratrol may act as potential adjunctive treatment for late-stage hormone refractory prostate cancer.More importantly, for the first time, our study demonstrates the mechanism by which AR regulates PTEN expression at the transcription level, indicating the direct link between a nuclear receptor and the PI3K/AKT pathway.

View Article: PubMed Central - PubMed

Affiliation: Genomic Medicine Institute, Cleveland Clinic, 9500 Euclid Avenue, Cleveland, OH 44195, USA.

ABSTRACT
The tumor suppressor gene PTEN (phosphatase and tensin homolog deleted on chromosome 10) and the androgen receptor (AR) play important roles in tumor development and progression in prostate carcinogenesis. Among many functions, PTEN negatively regulates the cytoplasmic phosphatidylinositol-3-kinase/AKT anti-apoptotic pathway; and nuclear PTEN affects the cell cycle by also negatively regulating the MAPK pathway via cyclin D. Decreased PTEN expression is correlated with prostate cancer progression. Over-expression of AR and upregulation of AR transcriptional activity are often observed in the later stages of prostate cancer. Recent studies indicate that PTEN regulates AR activity and stability. However, the mechanism of how AR regulates PTEN has never been studied. Furthermore, resveratrol, a phytoalexin enriched in red grapes, strawberries and peanuts, has been shown to inhibit AR transcriptional activity in prostate cancer cells. In this study, we use prostate cancer cell lines to test the hypothesis that resveratrol inhibits cellular proliferation in both AR-dependent and -independent mechanisms. We show that resveratrol inhibits AR transcriptional activity in both androgen-dependent and -independent prostate cancer cells. Additionally, resveratrol stimulates PTEN expression through AR inhibition. In contrast, resveratrol directly binds epidermal growth factor receptor (EGFR) rapidly inhibiting EGFR phosphorylation, resulting in decreased AKT phosphorylation, in an AR-independent manner. Thus, resveratrol may act as potential adjunctive treatment for late-stage hormone refractory prostate cancer. More importantly, for the first time, our study demonstrates the mechanism by which AR regulates PTEN expression at the transcription level, indicating the direct link between a nuclear receptor and the PI3K/AKT pathway.

Show MeSH
Related in: MedlinePlus