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Mutant p53 initiates a feedback loop that involves Egr-1/EGF receptor/ERK in prostate cancer cells.

Sauer L, Gitenay D, Vo C, Baron VT - Oncogene (2010)

Bottom Line: Egr-1 increased the transcription of HB-EGF (epidermal growth factor), amphiregulin and epiregulin, resulting in autocrine activation of the EGF receptor (EGFR) and downstream MEK/ERK cascade.Thus, mutant p53 initiates a feedback loop that involves ERK1/2-mediated transactivation of Egr-1, which in turn increases the secretion of EGFR ligands and stimulates the EGFR signaling pathway.Finally, p53 may further regulate this feedback loop by altering the level of EGFR expression.

View Article: PubMed Central - PubMed

Affiliation: Vaccine Research Institute of San Diego, San Diego, CA 92121, USA.

ABSTRACT
Early growth response-1 (Egr-1) is overexpressed in human prostate tumors and contributes to cancer progression. On the other hand, mutation of p53 is associated with advanced prostate cancer, as well as with metastasis and hormone independence. This study shows that in prostate cell lines in culture, Egr-1 overexpression correlated with an alteration of p53 activity because of the expression of SV40 large T-antigen or because of a mutation in the TP53 gene. In cells containing altered p53 activity, Egr-1 expression was abolished by pharmacological inhibition or RNAi silencing of p53. Although forced expression of wild-type p53 was not sufficient to trigger Egr-1 transcription, four different mutants of p53 were shown to induce Egr-1. Direct binding of p53 to the EGR1 promoter could not be detected. Instead, Egr-1 transcription was driven by the ERK1/2 pathway, as it was abrogated by specific inhibitors of MEK. Egr-1 increased the transcription of HB-EGF (epidermal growth factor), amphiregulin and epiregulin, resulting in autocrine activation of the EGF receptor (EGFR) and downstream MEK/ERK cascade. Thus, mutant p53 initiates a feedback loop that involves ERK1/2-mediated transactivation of Egr-1, which in turn increases the secretion of EGFR ligands and stimulates the EGFR signaling pathway. Finally, p53 may further regulate this feedback loop by altering the level of EGFR expression.

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Constitutive activation of EGFR and ERK1/2 regulates Egr-1 expression(Panel A) DU145 and 22Rv1 cells were treated with PD168393 (2 μM) for 2 hrs. Cells were lysed and subjected to immunoprecipitation using anti-EGFR antibodies. Buffer alone (NS) or non-specific immunoglobulins (IgG) were negative controls. Whole cell lysates were loaded for positive control (input). (Panel B) DU145 (left) were treated with EGFR inhibitor PD168393 at 2 μM for the indicated times. 22Rv1 (right) were treated with PD168393 at 2 μM for 24 hrs.(Panel C) DU145 were incubated with increasing amounts of neutralizing anti-EGFR antibodies for 24 hours before lysis. (Panel D) Cells were treated with MEK inhibitor PD98059 for 2 hrs before lysis. All experiments were analyzed by western blot using the indicated antibodies. Actin or pan-ERK1 antibodies were used for loading controls. P-ERK: anti-phospho-ERK1/2; P-Tyr: anti-phospho-tyrosine.
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Figure 4: Constitutive activation of EGFR and ERK1/2 regulates Egr-1 expression(Panel A) DU145 and 22Rv1 cells were treated with PD168393 (2 μM) for 2 hrs. Cells were lysed and subjected to immunoprecipitation using anti-EGFR antibodies. Buffer alone (NS) or non-specific immunoglobulins (IgG) were negative controls. Whole cell lysates were loaded for positive control (input). (Panel B) DU145 (left) were treated with EGFR inhibitor PD168393 at 2 μM for the indicated times. 22Rv1 (right) were treated with PD168393 at 2 μM for 24 hrs.(Panel C) DU145 were incubated with increasing amounts of neutralizing anti-EGFR antibodies for 24 hours before lysis. (Panel D) Cells were treated with MEK inhibitor PD98059 for 2 hrs before lysis. All experiments were analyzed by western blot using the indicated antibodies. Actin or pan-ERK1 antibodies were used for loading controls. P-ERK: anti-phospho-ERK1/2; P-Tyr: anti-phospho-tyrosine.

Mentions: As shown in figure 4A, the EGFR was constitutively phosphorylated in DU145 but not in 22Rv1. A time-course of EGFR inhibitor PD168393 in DU145 rapidly reduced ERK1/2 phosphorylation and decreased Egr-1 expression, whereas it failed to do so in 22Rv1 (figure 4B).


Mutant p53 initiates a feedback loop that involves Egr-1/EGF receptor/ERK in prostate cancer cells.

Sauer L, Gitenay D, Vo C, Baron VT - Oncogene (2010)

Constitutive activation of EGFR and ERK1/2 regulates Egr-1 expression(Panel A) DU145 and 22Rv1 cells were treated with PD168393 (2 μM) for 2 hrs. Cells were lysed and subjected to immunoprecipitation using anti-EGFR antibodies. Buffer alone (NS) or non-specific immunoglobulins (IgG) were negative controls. Whole cell lysates were loaded for positive control (input). (Panel B) DU145 (left) were treated with EGFR inhibitor PD168393 at 2 μM for the indicated times. 22Rv1 (right) were treated with PD168393 at 2 μM for 24 hrs.(Panel C) DU145 were incubated with increasing amounts of neutralizing anti-EGFR antibodies for 24 hours before lysis. (Panel D) Cells were treated with MEK inhibitor PD98059 for 2 hrs before lysis. All experiments were analyzed by western blot using the indicated antibodies. Actin or pan-ERK1 antibodies were used for loading controls. P-ERK: anti-phospho-ERK1/2; P-Tyr: anti-phospho-tyrosine.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC2865566&req=5

Figure 4: Constitutive activation of EGFR and ERK1/2 regulates Egr-1 expression(Panel A) DU145 and 22Rv1 cells were treated with PD168393 (2 μM) for 2 hrs. Cells were lysed and subjected to immunoprecipitation using anti-EGFR antibodies. Buffer alone (NS) or non-specific immunoglobulins (IgG) were negative controls. Whole cell lysates were loaded for positive control (input). (Panel B) DU145 (left) were treated with EGFR inhibitor PD168393 at 2 μM for the indicated times. 22Rv1 (right) were treated with PD168393 at 2 μM for 24 hrs.(Panel C) DU145 were incubated with increasing amounts of neutralizing anti-EGFR antibodies for 24 hours before lysis. (Panel D) Cells were treated with MEK inhibitor PD98059 for 2 hrs before lysis. All experiments were analyzed by western blot using the indicated antibodies. Actin or pan-ERK1 antibodies were used for loading controls. P-ERK: anti-phospho-ERK1/2; P-Tyr: anti-phospho-tyrosine.
Mentions: As shown in figure 4A, the EGFR was constitutively phosphorylated in DU145 but not in 22Rv1. A time-course of EGFR inhibitor PD168393 in DU145 rapidly reduced ERK1/2 phosphorylation and decreased Egr-1 expression, whereas it failed to do so in 22Rv1 (figure 4B).

Bottom Line: Egr-1 increased the transcription of HB-EGF (epidermal growth factor), amphiregulin and epiregulin, resulting in autocrine activation of the EGF receptor (EGFR) and downstream MEK/ERK cascade.Thus, mutant p53 initiates a feedback loop that involves ERK1/2-mediated transactivation of Egr-1, which in turn increases the secretion of EGFR ligands and stimulates the EGFR signaling pathway.Finally, p53 may further regulate this feedback loop by altering the level of EGFR expression.

View Article: PubMed Central - PubMed

Affiliation: Vaccine Research Institute of San Diego, San Diego, CA 92121, USA.

ABSTRACT
Early growth response-1 (Egr-1) is overexpressed in human prostate tumors and contributes to cancer progression. On the other hand, mutation of p53 is associated with advanced prostate cancer, as well as with metastasis and hormone independence. This study shows that in prostate cell lines in culture, Egr-1 overexpression correlated with an alteration of p53 activity because of the expression of SV40 large T-antigen or because of a mutation in the TP53 gene. In cells containing altered p53 activity, Egr-1 expression was abolished by pharmacological inhibition or RNAi silencing of p53. Although forced expression of wild-type p53 was not sufficient to trigger Egr-1 transcription, four different mutants of p53 were shown to induce Egr-1. Direct binding of p53 to the EGR1 promoter could not be detected. Instead, Egr-1 transcription was driven by the ERK1/2 pathway, as it was abrogated by specific inhibitors of MEK. Egr-1 increased the transcription of HB-EGF (epidermal growth factor), amphiregulin and epiregulin, resulting in autocrine activation of the EGF receptor (EGFR) and downstream MEK/ERK cascade. Thus, mutant p53 initiates a feedback loop that involves ERK1/2-mediated transactivation of Egr-1, which in turn increases the secretion of EGFR ligands and stimulates the EGFR signaling pathway. Finally, p53 may further regulate this feedback loop by altering the level of EGFR expression.

Show MeSH
Related in: MedlinePlus