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Erk2 but not Erk1 regulates crosstalk between Met and EGFR in squamous cell carcinoma cell lines.

Gusenbauer S, Zanucco E, Knyazev P, Ullrich A - Mol. Cancer (2015)

Bottom Line: Met activation correlates with poor patient outcome.Amphiregulin is transcriptionally upregulated and is released into the supernatant.We show that Erk2 but not Erk1 mediates amphiregulin upregulation upon treatment with monocyte derived HGF.

View Article: PubMed Central - PubMed

Affiliation: Department of Molecular Biology, Max Planck Institute of Biochemistry, Am Klopferspitz 18, D-82152, Martinsried, Germany. gusenbau@biochem.mpg.de.

ABSTRACT

Background: Squamous cell carcinoma (SCC) is the most common type of tongue and larynx cancer and a common type of lung cancer. In this study, we attempted to specifically evaluate the signaling pathway underlying HGF/Met induced EGFR ligand release in SSCs. The Met proto-oncogene encodes for a tyrosine kinase receptor which is often hyperactivated in human cancers. Met activation correlates with poor patient outcome. Several studies revealed a role of Met in receptor-crosstalk inducing either activation of other receptors, or inducing their resistance to targeted cancer treatments. In an epithelial tumor cell line screen we recently showed that the Met ligand HGF blocks the EGFR tyrosine kinase and at the same time activates transcriptional upregulation and accumulation in the supernatant of the EGFR ligand amphiregulin (Oncogene 32:3846-56, 2013). In the present work we describe the pathway responsible for the amphiregulin induction.

Findings: Amphiregulin is transcriptionally upregulated and is released into the supernatant. We show that Erk2 but not Erk1 mediates amphiregulin upregulation upon treatment with monocyte derived HGF. A siRNA knockdown of Erk2 completely abolishes amphiregulin release in squamous cell carcinomas.

Conclusions: These results identify Erk2 as the key downstream signal transducer between Met activation and EGFR ligand upregulation in squamous cell carcinoma cell lines derived from tongue, larynx and lung.

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Related in: MedlinePlus

Paracrine interaction model between TAM, tumor cells and endothelial cells. TAMs and tumor-associated stromal fibroblasts release a variety of factors that support tumor growth and progression. HGF, one of these factors, prompts tumor cells to produce the EGFR ligand amphiregulin (AR). Importantly, once the tumor cells are activated by HGF, their EGF receptor cannot be activated by EGFR ligands anymore. However, tumor-associated endothelial cells express high levels of EGFR and have been shown to respond to EGFR activation [38,42,43]. Therefore, we propose, that the tumor vasculature represent a possible target for the produced EGFR ligands.
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Fig4: Paracrine interaction model between TAM, tumor cells and endothelial cells. TAMs and tumor-associated stromal fibroblasts release a variety of factors that support tumor growth and progression. HGF, one of these factors, prompts tumor cells to produce the EGFR ligand amphiregulin (AR). Importantly, once the tumor cells are activated by HGF, their EGF receptor cannot be activated by EGFR ligands anymore. However, tumor-associated endothelial cells express high levels of EGFR and have been shown to respond to EGFR activation [38,42,43]. Therefore, we propose, that the tumor vasculature represent a possible target for the produced EGFR ligands.

Mentions: In this study we have shown that HGF is a strong inducer of the EGFR ligand amphiregulin in different SCC cell lines and that amphiregulin acts as a potent activator of EGFR and HER2 in HGF untreated SCC9 cells. However in HGF treated cells EGFR and HER2 cannot be further activated by amphiregulin. Therefore it is likely, that the produced amphiregulin is provided for other cell types of the tumor stroma, which did not get in contact with HGF before or amphiregulin is provided for cell types, where the EGFR is not blocked by HGF. A second possibility is that amphiregulin might induce the recruitment and proliferation of stromal cells like endothelial cells and fibroblasts (FigureĀ 4) which promote tumor progression. Interestingly Amin et al. compared tumor-associated endothelial cells and normal endothelial cells and found that tumor-derived endothelial cells express EGFR, HER2 and HER4, whereas their normal counterparts express HER2, HER3 and HER4 [38]. As a consequence of the gain of EGFR and the loss of HER3, tumor vasculature responds to EGFR ligands. In their study they suggest that this receptor exchange promotes tumor angiogenesis. Similarly Cascone et al. showed in a mouse xenograft model of human lung andenocarcinoma an upregulation and hyperactivation of stromal EGFR in blood vessel pericytes of anti-VEGF treatment resistant tumors. In this elegant study they were able to distinguish between stromal (mouse) and cancer (human) cell specific changes of total and of phosphorylated EGFR levels [39]. Several other studies show a proangiogenic and tumor supporting effect of EGFR signaling inside the tumor vasculature [40,41]. A third possibility is, that the tumor-produced EGFR ligands exert their function in distant tissues and influence the generation of the metastatic niche. In this study, we identified MAPK signaling as the underlying pathway for new amphiregulin mRNA and protein syntheses. We intended to specifically inhibit Erk1 and 2 by siRNA knockdown and could demonstrate that Erk2 but not Erk1 is responsible for amphiregulin upregulation. In addition we demonstrate the ability of a monocytic cell line to induce amphiregulin release in a HGF/Met/MAPK-dependent manner. Our study grants further investigations which cell type in the tumor microenvironment or in distant tissues benefits from the released EGFR ligand amphiregulin during cancer progression. The detailed understanding of stromal signaling may be critical for the development of successful treatments and for the improvement of combination regimens.Figure 4


Erk2 but not Erk1 regulates crosstalk between Met and EGFR in squamous cell carcinoma cell lines.

Gusenbauer S, Zanucco E, Knyazev P, Ullrich A - Mol. Cancer (2015)

Paracrine interaction model between TAM, tumor cells and endothelial cells. TAMs and tumor-associated stromal fibroblasts release a variety of factors that support tumor growth and progression. HGF, one of these factors, prompts tumor cells to produce the EGFR ligand amphiregulin (AR). Importantly, once the tumor cells are activated by HGF, their EGF receptor cannot be activated by EGFR ligands anymore. However, tumor-associated endothelial cells express high levels of EGFR and have been shown to respond to EGFR activation [38,42,43]. Therefore, we propose, that the tumor vasculature represent a possible target for the produced EGFR ligands.
© Copyright Policy - open-access
Related In: Results  -  Collection

License 1 - License 2
Show All Figures
getmorefigures.php?uid=PMC4359546&req=5

Fig4: Paracrine interaction model between TAM, tumor cells and endothelial cells. TAMs and tumor-associated stromal fibroblasts release a variety of factors that support tumor growth and progression. HGF, one of these factors, prompts tumor cells to produce the EGFR ligand amphiregulin (AR). Importantly, once the tumor cells are activated by HGF, their EGF receptor cannot be activated by EGFR ligands anymore. However, tumor-associated endothelial cells express high levels of EGFR and have been shown to respond to EGFR activation [38,42,43]. Therefore, we propose, that the tumor vasculature represent a possible target for the produced EGFR ligands.
Mentions: In this study we have shown that HGF is a strong inducer of the EGFR ligand amphiregulin in different SCC cell lines and that amphiregulin acts as a potent activator of EGFR and HER2 in HGF untreated SCC9 cells. However in HGF treated cells EGFR and HER2 cannot be further activated by amphiregulin. Therefore it is likely, that the produced amphiregulin is provided for other cell types of the tumor stroma, which did not get in contact with HGF before or amphiregulin is provided for cell types, where the EGFR is not blocked by HGF. A second possibility is that amphiregulin might induce the recruitment and proliferation of stromal cells like endothelial cells and fibroblasts (FigureĀ 4) which promote tumor progression. Interestingly Amin et al. compared tumor-associated endothelial cells and normal endothelial cells and found that tumor-derived endothelial cells express EGFR, HER2 and HER4, whereas their normal counterparts express HER2, HER3 and HER4 [38]. As a consequence of the gain of EGFR and the loss of HER3, tumor vasculature responds to EGFR ligands. In their study they suggest that this receptor exchange promotes tumor angiogenesis. Similarly Cascone et al. showed in a mouse xenograft model of human lung andenocarcinoma an upregulation and hyperactivation of stromal EGFR in blood vessel pericytes of anti-VEGF treatment resistant tumors. In this elegant study they were able to distinguish between stromal (mouse) and cancer (human) cell specific changes of total and of phosphorylated EGFR levels [39]. Several other studies show a proangiogenic and tumor supporting effect of EGFR signaling inside the tumor vasculature [40,41]. A third possibility is, that the tumor-produced EGFR ligands exert their function in distant tissues and influence the generation of the metastatic niche. In this study, we identified MAPK signaling as the underlying pathway for new amphiregulin mRNA and protein syntheses. We intended to specifically inhibit Erk1 and 2 by siRNA knockdown and could demonstrate that Erk2 but not Erk1 is responsible for amphiregulin upregulation. In addition we demonstrate the ability of a monocytic cell line to induce amphiregulin release in a HGF/Met/MAPK-dependent manner. Our study grants further investigations which cell type in the tumor microenvironment or in distant tissues benefits from the released EGFR ligand amphiregulin during cancer progression. The detailed understanding of stromal signaling may be critical for the development of successful treatments and for the improvement of combination regimens.Figure 4

Bottom Line: Met activation correlates with poor patient outcome.Amphiregulin is transcriptionally upregulated and is released into the supernatant.We show that Erk2 but not Erk1 mediates amphiregulin upregulation upon treatment with monocyte derived HGF.

View Article: PubMed Central - PubMed

Affiliation: Department of Molecular Biology, Max Planck Institute of Biochemistry, Am Klopferspitz 18, D-82152, Martinsried, Germany. gusenbau@biochem.mpg.de.

ABSTRACT

Background: Squamous cell carcinoma (SCC) is the most common type of tongue and larynx cancer and a common type of lung cancer. In this study, we attempted to specifically evaluate the signaling pathway underlying HGF/Met induced EGFR ligand release in SSCs. The Met proto-oncogene encodes for a tyrosine kinase receptor which is often hyperactivated in human cancers. Met activation correlates with poor patient outcome. Several studies revealed a role of Met in receptor-crosstalk inducing either activation of other receptors, or inducing their resistance to targeted cancer treatments. In an epithelial tumor cell line screen we recently showed that the Met ligand HGF blocks the EGFR tyrosine kinase and at the same time activates transcriptional upregulation and accumulation in the supernatant of the EGFR ligand amphiregulin (Oncogene 32:3846-56, 2013). In the present work we describe the pathway responsible for the amphiregulin induction.

Findings: Amphiregulin is transcriptionally upregulated and is released into the supernatant. We show that Erk2 but not Erk1 mediates amphiregulin upregulation upon treatment with monocyte derived HGF. A siRNA knockdown of Erk2 completely abolishes amphiregulin release in squamous cell carcinomas.

Conclusions: These results identify Erk2 as the key downstream signal transducer between Met activation and EGFR ligand upregulation in squamous cell carcinoma cell lines derived from tongue, larynx and lung.

Show MeSH
Related in: MedlinePlus