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Event: 941

Key Event Title

The KE title should describe a discrete biological change that can be measured. It should generally define the biological object or process being measured and whether it is increased, decreased, or otherwise definably altered relative to a control state. For example “enzyme activity, decreased”, “hormone concentration, increased”, or “growth rate, decreased”, where the specific enzyme or hormone being measured is defined. More help

Activation, EGFR

Short name
The KE short name should be a reasonable abbreviation of the KE title and is used in labelling this object throughout the AOP-Wiki. The short name should be less than 80 characters in length. More help
Activation, EGFR

Biological Context

Structured terms, selected from a drop-down menu, are used to identify the level of biological organization for each KE. Note, KEs should be defined within a particular level of biological organization. Only KERs should be used to transition from one level of organization to another. Selection of the level of biological organization defines which structured terms will be available to select when defining the Event Components (below). More help

Cell term

Further information on Event Components and Biological Context may be viewed on the attached pdf.The biological context describes the location/biological environment in which the event takes place.  For molecular/cellular events this would include the cellular context (if known), organ context, and species/life stage/sex for which the event is relevant. For tissue/organ events cellular context is not applicable.  For individual/population events, the organ context is not applicable. More help

Organ term

Further information on Event Components and Biological Context may be viewed on the attached pdf.The biological context describes the location/biological environment in which the event takes place.  For molecular/cellular events this would include the cellular context (if known), organ context, and species/life stage/sex for which the event is relevant. For tissue/organ events cellular context is not applicable.  For individual/population events, the organ context is not applicable. More help

Key Event Components

Further information on Event Components and Biological Context may be viewed on the attached pdf.Because one of the aims of the AOP-KB is to facilitate de facto construction of AOP networks through the use of shared KE and KER elements, authors are also asked to define their KEs using a set of structured ontology terms (Event Components). In the absence of structured terms, the same KE can readily be defined using a number of synonymous titles (read by a computer as character strings). In order to make these synonymous KEs more machine-readable, KEs should also be defined by one or more “event components” consisting of a biological process, object, and action with each term originating from one of 22 biological ontologies (Ives, et al., 2017; See List). Biological process describes dynamics of the underlying biological system (e.g., receptor signalling). The biological object is the subject of the perturbation (e.g., a specific biological receptor that is activated or inhibited). Action represents the direction of perturbation of this system (generally increased or decreased; e.g., ‘decreased’ in the case of a receptor that is inhibited to indicate a decrease in the signalling by that receptor).Note that when editing Event Components, clicking an existing Event Component from the Suggestions menu will autopopulate these fields, along with their source ID and description. To clear any fields before submitting the event component, use the 'Clear process,' 'Clear object,' or 'Clear action' buttons. If a desired term does not exist, a new term request may be made via Term Requests. Event components may not be edited; to edit an event component, remove the existing event component and create a new one using the terms that you wish to add. More help
Process Object Action
epidermal growth factor-activated receptor activity epidermal growth factor receptor occurrence

Key Event Overview

AOPs Including This Key Event

All of the AOPs that are linked to this KE will automatically be listed in this subsection. This table can be particularly useful for derivation of AOP networks including the KE. Clicking on the name of the AOP will bring you to the individual page for that AOP. More help
AOP Name Role of event in AOP Point of Contact Author Status OECD Status
Decreased lung function MolecularInitiatingEvent Karsta Luettich (send email) Under development: Not open for comment. Do not cite Under Development


This is a structured field used to identify specific agents (generally chemicals) that can trigger the KE. Stressors identified in this field will be linked to the KE in a machine-readable manner, such that, for example, a stressor search would identify this as an event the stressor can trigger. NOTE: intermediate or downstream KEs in one AOP may function as MIEs in other AOPs, meaning that stressor information may be added to the KE description, even if it is a downstream KE in the pathway currently under development.Information concerning the stressors that may trigger an MIE can be defined using a combination of structured and unstructured (free-text) fields. For example, structured fields may be used to indicate specific chemicals for which there is evidence of an interaction relevant to this MIE. By linking the KE description to a structured chemical name, it will be increasingly possible to link the MIE to other sources of chemical data and information, enhancing searchability and inter-operability among different data-sources and knowledgebases. The free-text section “Evidence for perturbation of this MIE by stressor” can be used both to identify the supporting evidence for specific stressors triggering the MIE as well as to define broad chemical categories or other properties that classify the stressors able to trigger the MIE for which specific structured terms may not exist. More help

Taxonomic Applicability

Latin or common names of a species or broader taxonomic grouping (e.g., class, order, family) can be selected from an ontology. In many cases, individual species identified in these structured fields will be those for which the strongest evidence used in constructing the AOP was available in relation to this KE. More help
Term Scientific Term Evidence Link
human Homo sapiens High NCBI
mouse Mus musculus High NCBI
rat Rattus norvegicus High NCBI

Life Stages

The structured ontology terms for life-stage are more comprehensive than those for taxa, but may still require further description/development and explanation in the free text section. More help
Life stage Evidence
Adult High

Sex Applicability

The authors must select from one of the following: Male, female, mixed, asexual, third gender, hermaphrodite, or unspecific. More help
Term Evidence
Unspecific Not Specified

Key Event Description

A description of the biological state being observed or measured, the biological compartment in which it is measured, and its general role in the biology should be provided. For example, the biological state being measured could be the activity of an enzyme, the expression of a gene or abundance of an mRNA transcript, the concentration of a hormone or protein, neuronal activity, heart rate, etc. The biological compartment may be a particular cell type, tissue, organ, fluid (e.g., plasma, cerebrospinal fluid), etc. The role in the biology could describe the reaction that an enzyme catalyses and the role of that reaction within a given metabolic pathway; the protein that a gene or mRNA transcript codes for and the function of that protein; the function of a hormone in a given target tissue, physiological function of an organ, etc. Careful attention should be taken to avoid reference to other KEs, KERs or AOPs. Only describe this KE as a single isolated measurable event/state. This will ensure that the KE is modular and can be used by other AOPs, thereby facilitating construction of AOP networks. More help

The EGF receptor family comprises 4 members, EGFR (also referred to as ErbB1/HER1), ErbB2/Neu/HER2, ErbB3/HER3 and ErbB4/HER4, all of which are transmembrane glycoproteins with an extracellular ligand binding site and an intracellular tyrosine kinase domain. Receptor-ligand binding induces dimerization and internalization, subsequently leading to activation of the receptor through autophosphorylation (Higashiyama et al., 2008).

EGFR signaling is central to airway epithelial maintenance and mucin production (Burgel and Nadel, 2004), and EGFR expression has been demonstrated in lung epithelial cells under physiological (albeit weakly) as well as pathological conditions in vitro and in vivo (Aida et al., 1994; Burgel and Nadel, 2008; O’Donnell et al., 2004; Polosa et al., 1999). Of note, lung epithelial EGFR phosphorylation (i.e., activation) was increased under conditions of oxidative stress including exposure to H2O2 (Goldkorn et al., 1998), naphthalene (Van Winkle et al., 1997), cigarette smoke (de Boer et al., 2006; Marinaş et al., 2011) and in the presence of neutrophils or neutrophil elastase (Kohri et al., 2002; Shao et al., 2004; Shao and Nadel, 2005; Shim et al., 2001; Takeyama et al., 2000). EGFR activation by oxidative stress may have a number of root causes: ROS were shown to increase production of EGF, the prime EGFR ligand, by lung epithelial cells (Casalino-Matsuda et al., 2004). Similarly, expression and secretion of TGF-α and AREG, also EGFR ligands, were elevated in human bronchial epithelial cells in response to fine particulate matter (PM2.5), diesel particulate matter and cigarette smoke exposure (Blanchet et al., 2004; Lemjabbar et al., 2003; Rumelhard et al., 2007). Mechanistically, this process is dependent on ROS-mediated activation of metalloproteinases or ADAMs which cleave membrane-bound EGFR ligand precursors, making them locally available to bind to and transactivate EGFR in an autocrine manner (Deshmukh et al., 2009; Kim et al., 2004b; Val et al., 2012; Yoshisue and Hasegawa, 2004). Furthermore, ligand binding to EGFR itself was shown to lead to H2O2 production, thereby facilitating receptor activation and downstream signaling (DeYulia et al., 2005; DeYulia and Cárcamo, 2005; Truong and Carroll, 2012). While it is tempting to speculate that the increase in H2O2 would perpetuate EGFR activation via the continuous proteolytic shedding of pro-ligands in an autocrine loop, multiple lines of evidence suggest that oxidative modification, specifically EGFR sulfenylation, contributes to enhanced tyrosine phosphorylation of the receptor and downstream signaling (Paulsen et al., 2011; Ravid et al., 2002; Truong and Carroll, 2012; Truong et al., 2016).

Classical EGFR downstream signaling involves activation of Ras which subsequently initiates signal transduction through the Raf-1/MEK/ERK pathway. MAP kinase activation in turn promotes airway epithelial cell proliferation and differentiation (Hackel et al., 1999; Kim et al., 2005; Lemjabbar et al., 2003) and facilitates epithelial wound repair (Allahverdian et al., 2010; Burgel and Nadel, 2004; Van Winkle et al., 1997).

How It Is Measured or Detected

One of the primary considerations in evaluating AOPs is the relevance and reliability of the methods with which the KEs can be measured. The aim of this section of the KE description is not to provide detailed protocols, but rather to capture, in a sentence or two, per method, the type(s) of measurements that can be employed to evaluate the KE and the relative level of scientific confidence in those measurements. Methods that can be used to detect or measure the biological state represented in the KE should be briefly described and/or cited. These can range from citation of specific validated test guidelines, citation of specific methods published in the peer reviewed literature, or outlines of a general protocol or approach (e.g., a protein may be measured by ELISA).Key considerations regarding scientific confidence in the measurement approach include whether the assay is fit for purpose, whether it provides a direct or indirect measure of the biological state in question, whether it is repeatable and reproducible, and the extent to which it is accepted in the scientific and/or regulatory community. Information can be obtained from the OECD Test Guidelines website and the EURL ECVAM Database Service on Alternative Methods to Animal Experimentation (DB-ALM). ?

Proof of EGFR activation can be derived from Western blots of e.g. untreated and treated cell or tissue lysates using specific antibodies targeting the phosphorylated EGFR epitopes. Densitometric evaluation of the colorimetrically stained, chemiluminescent or radioactive bands on the blot then permit a (semi-)quantitative measure of activation. Moreover, the addition of EGFR inhibitors such as AG1478 and BIBX 1522 or neutralizing antibodies is well suited to demonstrate causality.

Domain of Applicability

This free text section should be used to elaborate on the scientific basis for the indicated domains of applicability and the WoE calls (if provided). While structured terms may be selected to define the taxonomic, life stage and sex applicability (see structured applicability terms, above) of the KE, the structured terms may not adequately reflect or capture the overall biological applicability domain (particularly with regard to taxa). Likewise, the structured terms do not provide an explanation or rationale for the selection. The free-text section on evidence for taxonomic, life stage, and sex applicability can be used to elaborate on why the specific structured terms were selected, and provide supporting references and background information.  More help

EGFR activation in human, mouse and rat is well documented, and EGF ligands and EGFR are orthologous within these species. EGFR is a driver of human cancer in various tissues and numerous drugs are approved that inhibit EGFR activation (Ciardiello and Tortora, 2008). Although EGFR and its ligands are expressed in human, mouse and rat (Chen et al., 2007), species differences have been noted in binding and structure (Nexø and Hansen, 1985), and even can have opposite downstream effects in mouse and rat (Kiley and Chevalier, 2007).

Evidence for Perturbation by Stressor

Overview for Molecular Initiating Event

When a specific MIE can be defined (i.e., the molecular target and nature of interaction is known), in addition to describing the biological state associated with the MIE, how it can be measured, and its taxonomic, life stage, and sex applicability, it is useful to list stressors known to trigger the MIE and provide evidence supporting that initiation. This will often be a list of prototypical compounds demonstrated to interact with the target molecule in the manner detailed in the MIE description to initiate a given pathway (e.g., 2,3,7,8-TCDD as a prototypical AhR agonist; 17α-ethynyl estradiol as a prototypical ER agonist). Depending on the information available, this could also refer to chemical categories (i.e., groups of chemicals with defined structural features known to trigger the MIE). Known stressors should be included in the MIE description, but it is not expected to include a comprehensive list. Rather initially, stressors identified will be exemplary and the stressor list will be expanded over time. For more information on MIE, please see pages 32-33 in the User Handbook.

EGFR activation in lung epithelial cells can be triggered by exposure to H2O2 (Goldkorn et al., 1998; Takeyama et al., 2000), naphthalene (Van Winkle et al., 1997), cigarette smoke (Takeyama et al., 2001; de Boer et al., 2006; Marinaş et al., 2011; Yu et al., 2011; Yu et al., 2015), acrolein (Deshmukh et al., 2008), and TCDD (Lee et al., 2011). Mechanistically, this process is dependent on ROS-mediated activation of metalloproteinases or ADAMs which cleave membrane-bound EGFR ligand precursors, making them locally available to bind to and transactivate EGFR in an autocrine manner (Deshmukh et al., 2009; Kim et al., 2004b; Val et al., 2012; Yoshisue and Hasegawa, 2004). Furthermore, ligand binding to EGFR itself was shown to lead to H2O2 production, thereby facilitating receptor activation and downstream signaling (DeYulia et al., 2005; DeYulia and Cárcamo, 2005; Truong and Carroll, 2012).


List of the literature that was cited for this KE description. Ideally, the list of references, should conform, to the extent possible, with the OECD Style Guide ( (OECD, 2015). More help

Aida, S., et al., Distribution of epidermal growth factor and epidermal growth factor receptor in human lung: immunohistochemical and immunoelectron-microscopic studies. Respiration, 1994. 61(3):161-166.

Allahverdian, S., et al., Sialyl Lewis X modification of the epidermal growth factor receptor regulates receptor function during airway epithelial wound repair. Clin Exp Allergy, 2010. 40(4):607-618.

Blanchet, S., et al., Fine particulate matter induces amphiregulin secretion by bronchial epithelial cells. Am J Resp Cell Mol Biol, 2004. 30(4):421-427.

Burgel, P.-R. and J.A. Nadel, Epidermal growth factor receptor-mediated innate immune responses and their roles in airway diseases. Eur Resp J, 2008. 32(4):1068-1081.

Ciardiello, F., and Tortora, G. (2008). EGFR antagonists in cancer treatment. N Engl J Med, 2008. 358(11):1160–1174.

Casalino-Matsuda, S.M., et al., Role of hyaluronan and reactive oxygen species in tissue kallikrein-mediated epidermal growth factor receptor activation in human airways. J Biol Chem, 2004. 279(20):21606-21616.

Chen, H., et al., Epidermal growth factor receptor in adult retinal neurons of rat, mouse, and human. J Comp Neurol 2007. 500(2):299-310.

de Boer, W.I., et al., Expression of epidermal growth factors and their receptors in the bronchial epithelium of subjects with chronic obstructive pulmonary disease. American Journal of Clinical Pathology, 2006. 125(2):184-192.

Deshmukh, H.S., et al., Acrolein-activated matrix metalloproteinase 9 contributes to persistent mucin production. Am J Resp Cell Mol Biol, 2008. 38(4):446-454.

Deshmukh, H.S., et al., Matrix metalloproteinase-14 mediates a phenotypic shift in the airways to increase mucin production. Am J Respir Crit Care Med, 2009. 180(9):834-845.

DeYulia, G.J., et al., Hydrogen peroxide generated extracellularly by receptor–ligand interaction facilitates cell signaling. PNAS, 2005. 102(14):5044-5049.

DeYulia, G.J. and J.M. Cárcamo, EGF receptor-ligand interaction generates extracellular hydrogen peroxide that inhibits EGFR-associated protein tyrosine phosphatases. Biochem Biophys Res Commun, 2005. 334(1):38-42.

Goldkorn, T., et al., EGF-receptor phosphorylation and signaling are targeted by H2O2 redox stress. Am J Resp Cell Mol Biol, 1998. 19(5):786-798.

Hackel, P.O., et al., Epidermal growth factor receptors: critical mediators of multiple receptor pathways. Curr Opin Cell Biol, 1999. 11(2):184-189.

Higashiyama, S., et al., Membrane-anchored growth factors, the epidermal growth factor family: Beyond receptor ligands. Cancer Sci, 2008. 99(2):214-220.

Jorissen, R.N., et al., Epidermal growth factor receptor: mechanisms of activation and signalling. Exp Cell Res 2003. 284(1):31–53.

Kiley, S.C., and Chevalier, R.L., Species differences in renal Src activity direct EGF receptor regulation in life or death response to EGF. Am J. Physiol Renal Physiol, 2007. 293(3):F895–F903.

Kim, J.H., et al., Effects of matrix metalloproteinase inhibitor on LPS-induced goblet cell metaplasia. Am J Physiol Lung Cell Mol Physiol, 2004. 287(1):L127-L133.

Kim, S., et al., E-cadherin promotes EGFR-mediated cell differentiation and MUC5AC mucin expression in cultured human airway epithelial cells. Am J Physiol Lung Cell Mol Physiol, 2005. 289(6):L1049-L1060.

Kohri, K., et al., Neutrophil elastase induces mucin production by ligand-dependent epidermal growth factor receptor activation. Am J Physiol Lung Cell Mol Physiol, 2002. 283(3):L531-L540.

Lee, Y.C., et al., 2,3,7,8-Tetrachlorodibenzo-p-dioxin–Induced MUC5AC Expression Aryl Hydrocarbon Receptor-Independent/EGFR/ERK/p38-Dependent SP1-Based Transcription. Am J Respir Cell Mol Biol, 2011. 45(2):270-276.

Lemjabbar, H., et al., Tobacco smoke-induced lung cell proliferation mediated by tumor necrosis factor alpha-converting enzyme and amphiregulin. J Biol Chem, 2003. 278(28):26202-7.

Marinaş, A., et al., Expression of Epidermal Growth Factor (EGF) and its receptors (EGFR1 and EGFR2) in chronic bronchitis. Rom J Morphol Embryol, 2011. 53(4):957-966.

Nexø, E., and Hansen, H.F. (1985). Binding of epidermal growth factor from man, rat and mouse to the human epidermal growth factor receptor. Biochim Biophys Acta 843(1-2):101–106.

O’Donnell, R., et al., Expression of ErbB receptors and mucins in the airways of long term current smokers. Thorax, 2004. 59(12):1032-1040.

Paulsen, C.E., et al., Peroxide-dependent sulfenylation of the EGFR catalytic site enhances kinase activity. Nat Chem Biol, 2011. 8(1):57-64.

Polosa, R., et al., Expression of c-erbB receptors and ligands in human bronchial mucosa. Am J Resp Cell Mol Biol 1999. 20(5):914-923.

Ravid, T., et al., Epidermal growth factor receptor activation under oxidative stress fails to promote c-Cbl mediated down-regulation. J Biol Chem, 2002. 277(34):31214-31219.

Rumelhard, M., et al., Expression and role of EGFR ligands induced in airway cells by PM2.5 and its components. Eur Resp J, 2007. 30(6):1064-1073.

Shao, M.X.G., et al., Cigarette smoke induces MUC5AC mucin overproduction via tumor necrosis factor-alpha-converting enzyme in human airway epithelial (NCI-H292) cells. Am J Physiol Lung Cell Mol Physiol, 2004. 287(2), L420–L427.

Shao, M.X.G. and J.A. Nadel, Neutrophil Elastase Induces MUC5AC Mucin Production in Human Airway Epithelial Cells via a Cascade Involving Protein Kinase C, Reactive Oxygen Species, and TNF-α-Converting Enzyme. J Immunol, 2005. 175(6):4009-4016.

Shim, J.J., et al., IL-13 induces mucin production by stimulating epidermal growth factor receptors and by activating neutrophils. Am J Physiol Lung Cell Mol Physiol, 2001. 280(1):L134-L140.

Takeyama, K., et al., Oxidative stress causes mucin synthesis via transactivation of epidermal growth factor receptor: role of neutrophils. J Immunol, 2000. 164(3):1546-1552.

Takeyama, K., et al., Activation of epidermal growth factor receptors is responsible for mucin synthesis induced by cigarette smoke. Am J Physiol Lung Cell Mol Physiol, 2001. 280(1):L165-L172.

Truong, T.H. and K.S. Carroll, Redox regulation of EGFR signaling through cysteine oxidation. Biochemistry, 2012. 51(50):9954-9965.

Truong, T.H., et al., Molecular basis for redox activation of epidermal growth factor receptor kinase. Cell Chem Biol 2016. 23(7):837-848.

Val, S., et al., Fine PM induce airway MUC5AC expression through the autocrine effect of amphiregulin. Arch Toxicol, 2012. 86(12):1851-1859.

Van Winkle, L.S., J.M. Isaac, and C.G. Plopper, Distribution of epidermal growth factor receptor and ligands during bronchiolar epithelial repair from naphthalene-induced Clara cell injury in the mouse. Am J Pathol, 1997. 151(2):443-459.

Yoshisue, H. and K. Hasegawa, Effect of MMP/ADAM inhibitors on goblet cell hyperplasia in cultured human bronchial epithelial cells. Biosci Biotechnol Biochem, 2004. 68(10):2024-2031.

Yu, H., et al., Regulation of Cigarette Smoke-Induced Mucin Expression by Neuregulin1β/ErbB3 Signalling in Human Airway Epithelial Cells. Basic Clin Pharmacol Toxicol, 2011. 109(1):63-72.

Yu, Q., et al., Caveolin-1 aggravates cigarette smoke extract-induced MUC5AC secretion in human airway epithelial cells. Intl J Mol Med, 2015. 35(5):1435-1442.