Disease relevance of EGFR

• Here we provide evidence that prostaglandin E2 (PGE2) rapidly phosphorylates EGFR and triggers the extracellular signal-regulated kinase 2 (ERK2)--mitogenic signaling pathway in normal gastric epithelial (RGM1) and colon cancer (Caco-2, LoVo and HT-29) cell lines [1].
• Our findings that PGE2 transactivates EGFR reveal a previously unknown mechanism by which PGE2 mediates trophic actions resulting in gastric and intestinal hypertrophy as well as growth of colonic polyps and cancers [1].
• In two cell lines that overexpress erbB2 but do not expresss EGFR (MDA-MB-453 breast cancer cells and a Chinese hamster ovary cell line that had been transfected with erbB2), phosphorylation of p185erbB2 was induced only by gp30 [2].
• Therefore, the EGFR retrovirus, which had a titer on NIH 3T3 cells that was greater than 10(7) focus-forming units per milliliter, can efficiently transfer and express this gene, and increased numbers of EGF receptors can contribute to the transformed phenotype [3].
• Multivariate classification and regression-tree analysis of all 174 patients identified EGFR amplification as an independent predictor of prolonged survival in patients with glioblastoma multiforme who were older than 60 years of age [4].

Psychiatry related information on EGFR

• Detection of EGFR mutations has become an important issue for therapeutic decision-making in non-small cell lung cancer [5].
• Our data suggest that ligand-independent phosphorylation of EGFR and likely dependent downstream signaling pathways regulate cellular defense mechanisms important for cell survival following oxidative stress [6].
• While a variety of factors may be responsible for these findings, endothelial EGFR expression cannot be used to confirm a premortem clinical diagnosis of dementia [7].
• CONCLUSIONS: Enhanced secretion of EGFR and Neu was found in a large cohort of retired asbestos workers with a wide range of exposure and latency periods [8].
• Our findings indicate a potential link between EGF-receptor activation and drug addiction [9].

High impact information on EGFR

• (2006) in this issue of Cell provides compelling evidence that the tyrosine kinase domain of the epidermal growth factor receptor (EGFR) is activated by the formation of an asymmetric dimer, with one kinase domain in the EGF-mediated dimer activating the other through an allosteric mechanism [10].
• We find that the EGFR kinase domain can be activated by increasing its local concentration or by mutating a leucine (L834R) in the activation loop, the phosphorylation of which is not required for activation [11].
• The mechanism by which the epidermal growth factor receptor (EGFR) is activated upon dimerization has eluded definition [11].
• Mathematical modeling of the EGF-EGFR binding kinetics measured at single molecule level using total internal reflectance fluorescence (TIRF) microcopy revealed that cells respond differently to the same concentration of EGF depending on the number of EGFRs expressed. Compared to the Hela cells (aproximately 50,000 receptors/cell), EGFR-overexpressing MDA-468 cells (>1 million receptors/cell) show; (a) higher number of pre-formed dimers, (b) improved EGF-EGFR interaction at lower ligand concentrations, and (c) shorter time-lapse between first and second EGF binding to the dimer [12] .
• Treatment with a pharmacological inhibitor of EGFR, AG1478, dramatically increases the extent of pre-formed EGFR dimers [12].
• These observations implicate altered EGFR signaling in genetic susceptibility to lung cancer [13].
• Inherited susceptibility to lung cancer may be associated with the T790M drug resistance mutation in EGFR [13].

Chemical compound and disease context of EGFR

• An antibody to EGFR abolished the tyrosine phosphorylation induced by EGF and transforming growth factor-alpha (TGF-alpha) but only partially blocked that produced by gp30 in SK-BR-3 breast cancer cells [2].
• Thus, EGFR blockade (using an irreversible EGFR kinase inhibitor designated EKB-569) prevents virus-induced increases in ciliated and goblet cells whereas IL-13 blockade (using s-IL-13Ralpha2-Fc) exacerbates ciliated cell hyperplasia but still inhibits goblet cell metaplasia [14].
• A novel acylglycerol kinase that produces lysophosphatidic acid modulates cross talk with EGFR in prostate cancer cells [15].
• Therapies that target the EGF receptor (EGFR), such as gefitinib (IRESSA), are effective in a subset of patients with advanced non-small cell lung cancer (NSCLC) [16].
• Non-small cell lung cancers (NSCLCs) with activating mutations in the kinase domain of the epidermal growth factor receptor (EGFR) demonstrate dramatic, but transient, responses to the reversible tyrosine kinase inhibitors gefitinib (Iressa) and erlotinib (Tarceva) [17].

Biological context of EGFR

• Epidermal growth factor (EGF) regulates cell proliferation and differentiation by binding to the EGF receptor (EGFR) extracellular region, comprising domains I-IV, with the resultant dimerization of the receptor tyrosine kinase [18].
• The epidermal growth factor receptor (EGFR) gene is frequently amplified and/or overexpressed in human malignancies [19].
• These observations demonstrate a role for SRC kinase in modification and recruitment of clathrin during ligand-induced EGFR endocytosis and thereby define a novel effector mechanism for regulation of endocytosis by receptor signaling [20].
• Finally, high levels of EGFR expression, which conferred a transformed phenotype to NIH 3T3 cells in the presence of ligand, were demonstrated in representative human tumor cell lines that contained amplified copies of the EGFR gene [19].
• The unique "receptor-mediated dimerization" was verified by EGFR mutagenesis [18].

Anatomical context of EGFR

• As activation of the epidermal growth factor receptor (EGFR) triggers mitogenic signaling in gastrointestinal mucosa, and its expression is also upregulated in colonic cancers and most neoplasms, we investigated whether PGs transactivate EGFR [1].
• Thus, SNX1 is likely to play a role in sorting EGFR to lysosomes [21].
• Neurite outgrowth was not observed with chimeric receptors that contained the transmembrane domain from the EGFR, suggesting that the membrane-spanning region and cytoplasmic domain of the low-affinity NGFR are necessary for signal transduction [22].
• Reduced expression of the EGFR also was observed in Ta fibroblasts and liver membranes [23].
• In three of the remaining six cases of small gestational age placentas with low EGFR phosphorylation, there was no maternal pathology or significant parenchymatous placental lesions [24].

Associations of EGFR with chemical compounds

• Inactivation of EGFR kinase with selective inhibitors significantly reduces PGE2-induced ERK2 activation, c-fos mRNA expression and cell proliferation [1].
• By use of a colony-forming assay, the 1-hour IC50 (i.e., the concentration of drug required for 1 hour to achieve 50% cell kill) for cisplatin was 2 microM or less for parental and vector-transfected clones (n = 4), whereas it was 25 microM or more for all MDA-468/AS-EGFR clones (n = 3) [25].
• We have identified a regulated interaction between parkin and Eps15, an adaptor protein that is involved in epidermal growth factor (EGF) receptor (EGFR) endocytosis and trafficking [26].
• EGFR-dependent adhesion was noted when the ligands were tethered to inert beads, simulating the physiologically relevant presentation of tenascin-C as hexabrachion, and suggesting an increase in avidity similar to that seen for integrin ligands upon surface binding [27].
• Transient expression of either Gq- or Gi-coupled receptors in COS-7 cells allowed GPCR agonist-induced EGFR transactivation, and lysophosphatidic acid (LPA)-generated signals involved the docking protein Gab1 [28].

Physical interactions of EGFR

• Shc immunoprecipitates performed after IGF-1 stimulation contain coprecipitated EGFR, suggesting that IGF-1R activation induces the assembly of EGFR.Shc complexes [29].
• We mapped the EGFR phosphotyrosine 1173 as the major binding site for SHP-1 by a combination of phosphopeptide activation, phosphopeptide competition, and receptor YF mutant analysis [30].
• By gel filtration chromatography, we show that Ent-1 and SNX1 co-eluted in macromolecular complexes containing part of EGFR [31].
• RGS16 co-immunoprecipitated with EGFR, and the interaction did not require EGFR activation [32].
• Finally, the PKAI-EGF-R association occurs through the binding of RIalpha to the SH3 domain(s) of Grb2 adaptor protein, thus allowing the recruitment of the PKAI holoenzyme to the activated EGF-R [33].

Enzymatic interactions of EGFR

• The protein-tyrosine phosphatase SHP-1 binds to and dephosphorylates the epidermal growth factor receptor (EGFR), and both SH2 domains of SHP-1 are important for this interaction (Tenev, T., Keilhack, H., Tomic, S., Stoyanov, B., Stein-Gerlach, M., Lammers, R., Krivtsov, A. V., Ullrich, A., and Böhmer, F. D. (1997) J. Biol. Chem. 272, 5966-5973) [30].
• Purified EGFR phosphorylated only recombinant RGS16 wild-type or Y177F in vitro, implying that EGFR-mediated phosphorylation depended on residue Tyr(168) [32].
• Combined cell lysates were affinity-purified over the SH2 domain of the adapter protein Grb2 (GST-SH2 fusion protein) that specifically binds phosphorylated EGFR and Src homologous and collagen (Shc) protein [34].
• Dok-R has previously been shown to associate with the epidermal growth factor receptor (EGFR) and become tyrosine phosphorylated in response to EGF stimulation [35].
• METHODS: Expression of EGFR and ligand-independent EGFRvIII mutant proteins and of phosphorylated protein kinase B (PKB)/Akt in specimens from glioma patients were assessed by immunohistochemistry [36].

Co-localisations of EGFR

• Moreover, activated endogenous epidermal growth factor receptor (EGFR) colocalizes markedly with SNX2-positive endosomes, but minimally with SNX1-containing vesicles [37].
• Grb2 and the EGFR are internalized and co-localized in endocytic vesicles in response to EGF [38].
• Furthermore, EGFR colocalized with IP receptor in the glandular epithelial compartment [39].
• The dexamethasone-induced block of Grb2 recruitment was parallelled by changes in phosphorylation status and subcellular localization of lipocortin 1 (LC1) and an increase in the amount of the tyrosine phosphoprotein co-localized with EGF-R [40].
• We also demonstrated up-regulated caveolin proteins were co-localized with EGFR proteins in detergent-insoluble fractions [41].

Regulatory relationships of EGFR

• The epidermal growth factor (EGF) family of receptors (EGFR) is overproduced in estrogen receptor (ER) negative (-) breast cancer cells [42].
• Remarkably, experiments in Cos cells show that this complex stimulates EGF-triggered EGFR tyrosine phosphorylation [43].
• Taken in combination, these results provide strong evidence of PTEN/MMAC's role in regulating glioma angiogenesis even in the presence of strong proangiogenic signals provided by constitutive EGFR activation or p53 inactivation [44].
• The induction of apoptosis in these EGFR-mutant cell lines corresponds to down-regulation of activated Akt and STAT3 survival proteins [45].
• Blockade of Src family kinases using an Src-specific tyrosine kinase inhibitor A-419259 decreased GRP-induced EGFR phosphorylation and MAPK activation [46].

Other interactions of EGFR

• PTEN mutation, EGFR amplification, and outcome in patients with anaplastic astrocytoma and glioblastoma multiforme [4].
• TxB regulation of EGFR-ERK1/2 signaling pathways was determined using immunoblot analysis, confocal microscopy, and enzyme-linked immunosorbent assay, whereas IL-8 gene expression was measured by luciferase promoter assay [47].
• Interestingly, DT-induced 22Na+ influx was weak in DTR-EGFR cells and not detectable in DTR-GPI cells [48].
• Furthermore, we have identified a short sequence motif (YV/IN) present in IRS-1, EGFR and Shc, which specifically binds the SH2 domain of GRB2 with high affinity [49].
• The transmission of mitogenic signal induced by EGF-EGFR interaction is mediated via activation of nuclear factor kappaB (NF-kappaB) [42].

Analytical, diagnostic and therapeutic context of EGFR

• A subset of signal transducers required the normal endocytic trafficking of EGFR for full activation [50].
• The sixth placenta yielded a single 145-kD EGFR band consistent with an abnormal EGFR structure; Western blot analysis showed no immunoreactive band [24].
• Placental EGFR phosphorylation was significantly decreased or absent in 12 cases of small for gestational age neonates, as shown by SDS-PAGE, autoradiography, and scanning analysis [24].
• By using chromatin immunoprecipitation assays, we further demonstrated that nuclear EGFR associated with promoter region of cyclin D1 in vivo [51].
• EGFR activation was examined by immunoprecipitation and Western blotting using antiphosphotyrosine antibody [52].

References