The Central Role of Egf Receptor Blockade in the Inhibition of Mitogen-Activated Protein Kinase Pathways

Pütz, Thomas; Čulig, Zoran; Eder, Iris E.; Nessler-Menardi, Claudia; Bartsch, Georg; Grunicke, H.; Überall, Florian; Klocker, Helmut

doi:10.1097/00005392-199904010-00529

Cited by 8 publications

(15 citation statements)

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“…Cell lysates were prepared, Shc was immunoprecipitated using anti-Shc antibody, and following SDS-PAGE and Western blotting, membranes were probed with antiphosphotyrosine (a), anti-Shc (b) or anti-EGFR (C) antibody followed by peroxidase-conjugated appropriate secondary antibody and visualization by ECL detection system Grape seed extract modulates MAPKs in prostate cancer cells A Tyagi et al intensity as EGFR-Shc activation at most of the doses examined, we next assessed whether it has similar lack of effect on ERK1/2 kinase activity to Elk1. As shown in Figure 3b, sufficient ERK1/2 kinase activity was evidenced even in 24 h serum-starved DU145 cells that is consistent with a recent study showing a constitutively active ERK1/2 in DU145 cells (Putz et al, 1999;Segawa et al, 2001). However, treatment of starved cells with EGF resulted in a strong increase in ERK1/2 kinase activity to Elk1 (Figure 3b).…”

Section: Effect Of Gse On Egf-induced Egfr and Shc Activation As Wellsupporting

confidence: 91%

“…Consistent with this, there is enormous amount of renewed interest in targeting EGFR activation in both laboratory and clinical studies for the treatment of cancers with activated EGFR including human prostate cancer (Lin et al, 1999;Putz et al, 1999). Accordingly, the strong inhibitory effect of GSE on EGF-induced EGFR and Shc activation as well as EGFR-Shc binding is an important finding to be further explored in future studies.…”

Section: Discussionmentioning

confidence: 92%

“…Whereas GSEcaused robust increase in ERK1/2 phosphorylation possibly does not contribute significantly to a biological response because of a direct (third mechanism) inhibitory effect of GSE on the kinase activity of ERK1/2 to Elk1, GSE-caused robust and sustained JNK1/2 activation leads to a strong apoptotic death of DU145 cells (Figure 10). Several studies in recent years have shown that genetic alterations resulting in an enhanced expression of receptor and associated ligand lead to an epigenetic mechanism of autocrine growth loop via ligandreceptor interaction in advanced and androgen-independent PCA (Putz et al, 1999). For example, high levels of EGFR expression and autocrine secretion of its ligand have been reported in DU145 cells (Connolly and Rose, 1989;Tillotson and Rose, 1991).…”

Section: Discussionmentioning

confidence: 99%

“…Since GSE is rich in procyanidins that are monomer to polymers of catechins and epicatechins, the basic structure of epigallocatechin-3-gallate (Zhao et al, 1999), it was reasoned that a similar mechanism could be operational in this case. Secondly, we realized that since this mitogenic signaling pathway is constitutively active in DU145 cells (Putz et al, 1999;Segawa et al, 2001), it is equally important to define the inhibitory effect of GSE on constitutive activation of different signaling molecules in this cascade.…”

Section: Effect Of Gse On Egfr-shc-erk1/2-elk1-ap1 Activation In Serumentioning

confidence: 99%

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Grape seed extract inhibits EGF-induced and constitutively active mitogenic signaling but activates JNK in human prostate carcinoma DU145 cells: possible role in antiproliferation and apoptosis

2003

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A loss of functional androgen receptor and an enhanced expression of growth factor receptors and associated ligands are causal genetic events in prostate cancer (PCA) progression. These genetic alterations lead to an epigenetic mechanism where a feedback autocrine loop between membrane receptor and ligand (e.g. EGFR-TGFa) results in a constitutive activation of MAPK-Elk1-AP1-mediated mitogenic signaling in human PCA at an advanced and androgen-independent stage. We rationalized that inhibiting these epigenetic events could be useful in controlling advanced PCA growth. Recently, we found that grape seed extract (GSE), a dietary supplement rich in flavonoid procyanidins, inhibits advanced and androgenindependent human PCA DU145 cell growth in culture and nude mice. Here, we performed detailed mechanistic studies to define the effect of GSE on EGFR-Shc-MAPK-Elk1-AP1-mediated mitogenic signaling in DU145 cells. Pretreatment of serum-starved cells with GSE resulted in 70% to almost complete inhibition of EGF-induced EGFR activation and 50% to complete inhibition of Shc activation, which corroborated with a comparable decrease in EGF-induced Shc binding to EGFR. Conversely, EGF-induced ERK1/2 phosphorylation was inhibited only by lower doses of GSE; in fact, higher doses showed an increase. Additional studies showed that GSE alone causes a dose-and time-dependent increase in ERK1/2 phosphorylation in starved DU145 cells that is inhibited by an MEK1 inhibitor PD98059. Independent of this increase in ERK1/2 phosphorylation, GSE showed a strong inhibition of ERK1/2 kinase activity to Elk1 in both cellular and cell-free systems. GSE treatment of cells also inhibited both EGF-induced and constitutively active Elk1 phosphorylation and AP1 activation. GSE treatment also showed DNA synthesis inhibition in starved and EGF-stimulated cells as well as loss of cell viability and apoptotic death that was further increased by adding MEK1 inhibitor. Since GSE strongly induced apoptosis independent of its affect on an increase in phospho-ERK1/2, we hypothesized that apoptotic effect of GSE could be by other mechanism(s) including its effect on stress-associated MAPK, the JNK. Indeed, GSEtreated cells showed a strong and sustained increase in phospho-JNK1/JNK2 levels, JNK activity and phosphocJun levels. An inhibition of GSE-induced JNK activation by a novel JNK inhibitor SP600125 resulted in a significant reversal of GSE-induced apoptotic death suggesting the involvement of JNK activation by GSE in its apoptosis response. Together, these results suggest that anticancer effects of GSE in PCA be mediated via impairment of EGFR-ERK1/2-Elk1-AP1-mediated mitogenic signaling and activation of JNK causing growth inhibition and apoptosis, respectively.

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Section: Effect Of Gse On Egf-induced Egfr and Shc Activation As Wellsupporting

confidence: 91%

Section: Discussionmentioning

confidence: 92%

Section: Discussionmentioning

confidence: 99%

Section: Effect Of Gse On Egfr-shc-erk1/2-elk1-ap1 Activation In Serumentioning

confidence: 99%

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Grape seed extract inhibits EGF-induced and constitutively active mitogenic signaling but activates JNK in human prostate carcinoma DU145 cells: possible role in antiproliferation and apoptosis

2003

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“…Irradiation of tumor cells can both increase expression of TGFa and activate the EGFR, and this has been proposed to increase the proliferative rate of surviving cells (Levenson et al, 1998;Baselga et al, 1996;SchmidtUllrich et al, 1992;Putz et al, 1999). Increased proliferative rates and poor prognosis of carcinomas in vivo are also correlated with increased expression of the EGFR (Baselga et al, 1996;Schmidt-Ullrich et al, 1992;Putz et al, 1999). MAPK signaling has also been linked to increased expression of growth factors such as VEGF (Pages et al, 2000;Rak et al, 2000;Li et al, 2000).…”

Section: Introductionmentioning

confidence: 99%

Ionizing radiation modulates vascular endothelial growth factor (VEGF) expression through multiple mitogen activated protein kinase dependent pathways

et al. 2001

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PSK, a Novel STE20-like Kinase Derived from Prostatic Carcinoma That Activates the c-Jun N-terminal Kinase Mitogen-activated Protein Kinase Pathway and Regulates Actin Cytoskeletal Organization

Moore¹,

Garg²,

Johnson³

et al. 2000

Journal of Biological Chemistry

117

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1-349) did not localize to this compartment or induce a decrease in stress fibers demonstrating a requirement for the C terminus. Kinase-defective PSK (K57A) was unable to reduce stress fibers. PSK is the first member of the STE20 family lacking a Cdc42/Rac binding domain that has been shown to regulate both the c-Jun N-terminal kinase mitogen-activated protein kinase pathway and the actin cytoskeleton.

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The Central Role of Egf Receptor Blockade in the Inhibition of Mitogen-Activated Protein Kinase Pathways

Cited by 8 publications

References 0 publications

Grape seed extract inhibits EGF-induced and constitutively active mitogenic signaling but activates JNK in human prostate carcinoma DU145 cells: possible role in antiproliferation and apoptosis

Grape seed extract inhibits EGF-induced and constitutively active mitogenic signaling but activates JNK in human prostate carcinoma DU145 cells: possible role in antiproliferation and apoptosis

Ionizing radiation modulates vascular endothelial growth factor (VEGF) expression through multiple mitogen activated protein kinase dependent pathways

PSK, a Novel STE20-like Kinase Derived from Prostatic Carcinoma That Activates the c-Jun N-terminal Kinase Mitogen-activated Protein Kinase Pathway and Regulates Actin Cytoskeletal Organization

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