scholarly journals Epidermal Growth Factor Receptor Pathway Substrate 8 Is Overexpressed in Human Pituitary Tumors: Role in Proliferation and Survival

Endocrinology ◽  
2008 ◽  
Vol 150 (5) ◽  
pp. 2064-2071 ◽  
Author(s):  
Mei Xu ◽  
Lynnette Shorts-Cary ◽  
Aaron J. Knox ◽  
B Kleinsmidt-DeMasters ◽  
Kevin Lillehei ◽  
...  
Keyword(s):  
Growth Factor ◽  
Epidermal Growth Factor ◽  
Growth Factor Receptor ◽  
Pituitary Tumors ◽  
Pituitary Cells ◽  
Growth Factor Signaling ◽  
Fibroblast Growth Factor Receptors ◽  
Human Pituitary ◽  
Epidermal Growth ◽  
Induced Apoptosis

Based on prior work showing that human pituitary tumors overexpress epidermal and fibroblast growth factor receptors, we hypothesized that downstream components of growth factor signaling pathways may also be dysregulated. Epidermal growth factor pathway substrate number 8 (Eps8) was identified as a transcript overexpressed (5.9-fold) in human pituitary tumors compared with normal pituitary by DNA microarrays. Eps8 mRNA up-regulation was confirmed by semiquantitative RT-PCR. Immunoblot analysis showed that Eps8 protein levels and its downstream target phosphorylated ERK were also up-regulated in human pituitary tumors. Stable overexpression of Eps8 in LβT2 gonadotrope pituitary cells augmented colony formation in soft agar at d 21. Eps8 cells proliferated more robustly compared with controls in growth factor replete as well as growth-restricted conditions. In addition, the Eps8 overexpressing cells were protected from serum withdrawal-induced apoptosis compared with controls as assessed by caspase-3 cleavage. Epidermal growth factor activated a robust amplification of ERK and modest up-regulation of Akt in Eps8-overexpressing pituitary cells compared with vector controls. MAPK kinase inhibition or silencing of Eps8 blunted the proliferation of the cells in response to growth factor stimulation. Blockade of the phosphatidylinositol 3-kinase pathway or silencing of Eps8 resulted in a loss of the Eps8 protection from growth factor withdrawal-induced apoptosis. Together these data support a role of Eps8 in amplifying growth factor receptor signaling in human pituitary tumors to promote proliferation and cell survival.

scholarly journals Amphiregulin impairs apoptosis-stimulating protein 2 of p53 overexpression–induced apoptosis in hepatoma cells

Tumor Biology ◽  
2017 ◽  
Vol 39 (3) ◽  
pp. 101042831769502 ◽  
Author(s):  
Kai Liu ◽  
Dongdong Lin ◽  
Yabo Ouyang ◽  
Lijun Pang ◽  
Xianghua Guo ◽  
...  
Keyword(s):  
Hepatocellular Carcinoma ◽  
Epidermal Growth Factor Receptor ◽  
Growth Factor ◽  
Epidermal Growth Factor ◽  
Hepg2 Cells ◽  
Apoptotic Cell ◽  
Growth Factor Receptor ◽  
Hepatoma Cells ◽  
Epidermal Growth ◽  
Induced Apoptosis

Overexpression of apoptosis-stimulating protein 2 of p53 (ASPP2) induces apoptotic cell death in hepatoma cells (e.g. HepG2 cells) by enhancing the transactivation activity of p53, but long-term ASPP2 overexpression fails to induce more apoptosis since activation of the epidermal growth factor/epidermal growth factor receptor/SOS1 pathway impairs the pro-apoptotic role of ASPP2. In this study, in recombinant adenovirus-ASPP2-infected HepG2 cells, ASPP2 overexpression induces amphiregulin expression in a p53-dependent manner. Although amphiregulin initially contributes to ASPP2-induced apoptosis, it eventually impairs the pro-apoptotic function of ASPP2 by activating the epidermal growth factor/epidermal growth factor receptor/SOS1 pathway, leading to apoptosis resistance. Moreover, blocking soluble amphiregulin with a neutralizing antibody also significantly increased apoptotic cell death of HepG2 cells due to treatment with methyl methanesulfonate, cisplatin, or a recombinant p53 adenovirus, suggesting that the function of amphiregulin involved in inhibiting apoptosis may be a common mechanism by which hepatoma cells escape from stimulus-induced apoptosis. Thus, our data elucidate an apoptosis-evasion mechanism in hepatocellular carcinoma and have potential implications for hepatocellular carcinoma therapy.

Insulin-like growth factor-1 receptor/epidermal growth factor receptor (EGFR) heterodimerization and resistance to epidermal growth factor receptor tyrosine kinase inhibitors in non-small-cell lung cancer

2006 ◽  
Vol 24 (18_suppl) ◽  
pp. 13032-13032 ◽  
Author(s):  
F. Morgillo ◽  
W. K. Hong ◽  
H. Lee
Keyword(s):  
Lung Cancer ◽  
Epidermal Growth Factor Receptor ◽  
Growth Factor ◽  
Epidermal Growth Factor ◽  
Kinase Inhibitors ◽  
Growth Factor Receptor ◽  
Small Cell Lung ◽  
Epidermal Growth ◽  
Induced Apoptosis ◽  
Egfr Tkis

13032 Background: Epidermal growth factor receptor (EGFR) tyrosine kinase inhibitors (TKIs) have been used to treat lung cancers, but resistance to these agents has been observed. This study was designed to investigate whether the insulin-like growth factor (IGF)-mediated signaling pathway induces resistance to the EGFR TKIs in lung cancer. Methods: The antitumor activities and action mechanisms of EGFR inhibitors (erlotinib, gefinitib, cetuximab), single or in combination with IGF-IR inhibitors, were assessed in vitro in a subset of non-small-cell lung cancer (NSCLC) cell lines by the MTT assay, flow cytometry-based TUNEL assay, soft agar, confocal microscopy, metabolic labeling, coimmunoprecipitation, and northern and western blot analyses, and in vivo in animal models. Correlation of EGFR and IGF-1R expression was assessed using lung tissues from patients with NSCLC. Results: EGFR TKI inhibited the proliferation and anchorage-dependent and -independent colony-forming ability of NSCLC cells, which induced apoptosis, only when IGF-1R signaling was blocked. Treatment with EGFR TKIs, but not with the EGFR antibody, induced EGFR:IGF-1R heterodimerization on cell surface and activation of the IGF-1R, resulting in the stimulation of PI3K/Akt/ mTOR pathway, promoting the de novo protein biosynthesis of survivin and EGFR, resulting in the survival of NSCLC cells. When IGF-IR and mTOR were blocked, treatment of EGFR-TKIs induced apoptosis in NSCLC cells, resulting in suppression of the NSCLC tumor growth. When we tested the expression of IGF-R and EGFR in human lung tissue, 9/14 tumor samples exhibited increased expression of EGFR and 7/9 samples showed a correlative increases in IGF-IR protein levels compared to their paired normal counterparts. Conclusions: These findings suggest that simultaneous targeting of EGFR and IGF-1R signaling pathways might be an effective therapeutic strategy against NSCLC. No significant financial relationships to disclose.

scholarly journals Epidermal Growth Factor Signaling and Mitogenesis inPlcg1 Null Mouse Embryonic Fibroblasts

1998 ◽  
Vol 9 (4) ◽  
pp. 749-757 ◽  
Author(s):  
Qun-sheng Ji ◽  
Sandra Ermini ◽  
Josep Baulida ◽  
Feng-lei Sun ◽  
Graham Carpenter
Keyword(s):  
Growth Factor ◽  
Epidermal Growth Factor ◽  
Growth Factor Receptor ◽  
Receptor Activation ◽  
Mitogen Activated Protein Kinase ◽  
Null Mouse ◽  
Growth Factor Signaling ◽  
Mitogen Activated Protein ◽  
Epidermal Growth ◽  
Early Mouse

Gene targeting techniques and early mouse embryos have been used to produce immortalized fibroblasts genetically deficient in phospholipase C (PLC)-γ1, a ubiquitous tyrosine kinase substrate.Plcg1 −/− embryos die at embryonic day 9; however, cells derived from these embryos proliferate as well as cells from Plcg1 +/+ embryos. The null cells do grow to a higher saturation density in serum-containing media, as their capacity to spread out is decreased compared with that of wild-type cells. In terms of epidermal growth factor receptor activation and internalization, or growth factor induction of mitogen-activated protein kinase, c-fos, or DNA synthesis in quiescent cells, PLcg1 −/− cells respond equivalently to PLcg1 +/+ cells. Also, null cells are able to migrate effectively in a wounded monolayer. Therefore, immortalized fibroblasts do not require PLC-γ1 for many responses to growth factors.

Extracellular cysteine/cystine redox regulates the p44/p42 MAPK pathway by metalloproteinase-dependent epidermal growth factor receptor signaling

2005 ◽  
Vol 289 (1) ◽  
pp. G70-G78 ◽  
Author(s):  
Yvonne S. Nkabyo ◽  
Young-Mi Go ◽  
Thomas R. Ziegler ◽  
Dean P. Jones
Keyword(s):  
Epidermal Growth Factor Receptor ◽  
Growth Factor ◽  
Epidermal Growth Factor ◽  
Redox State ◽  
Mapk Pathway ◽  
Growth Factor Receptor ◽  
Mitogen Activated Protein Kinase ◽  
Growth Factor Signaling ◽  
Epidermal Growth ◽  
Mapk Inhibitors

Previous research shows that stimulation of proliferation of colon carcinoma (Caco-2) cells by a more reduced extracellular cysteine/cystine (Cys/CySS) redox state occurs with no apparent effect on intracellular glutathione and that this stimulation is lost on addition of epidermal growth factor. The purpose of the present study was to determine whether a more reduced extracellular Cys/CySS redox state activates the mitogenic p44/p42 mitogen-activated protein kinase (MAPK) pathway and whether this is signaled through the epidermal growth factor receptor (EGFR). Caco-2 cells were exposed to a range of physiological extracellular redox conditions from −150 to 0 mV. In the absence of added growth factors, the most reduced (−150 mV) redox state induced an 80% increase in EGFR phosphorylation, and this was followed by a marked increase in phosphorylation of p44/p42 MAPK. Inhibitors of EGFR (AG1478) and p44/p42 MAPK (U0126) phosphorylation blocked redox-dependent p44/p42 phosphorylation, indicating that signaling occurred by EGFR. These effects were inhibited by pretreatment with a nonpermeant alkylating agent, showing that signaling involved thiols accessible to the extracellular space. The EGFR ligand TGF-α was increased in culture medium at more reduced redox states. Redox-dependent phosphorylation of EGFR was completely prevented by a metalloproteinase inhibitor (GM6001), and an antibody to TGF-α partially inhibited the phosphorylation of p44/p42 MAPK by redox. Thus the data show that a redox-dependent activation of metalloproteinase can stimulate the mitogenic p44/p42 MAPK pathway by a TGF-α-dependent mechanism. Because Cys availability and Cys/CySS redox are dependent on nutrition, disease, and environmental exposures, the results suggest that cell proliferation could be influenced physiologically by Cys-dependent redox effects on growth factor signaling pathways.

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