To the extent possible under law, AOP-Wiki has waived all copyright and related or neighboring rights to KER:970

Relationship: 970


The title of the KER should clearly define the two KEs being considered and the sequential relationship between them (i.e., which is upstream and which is downstream). Consequently all KER titles take the form “upstream KE leads to downstream KE”.  More help

Activation, EGFR leads to Increased goblet cell proliferation

Upstream event
Upstream event in the Key Event Relationship. On the KER page, clicking on the Event name under Upstream Relationship will bring the user to that individual KE page. More help
Downstream event
Downstream event in the Key Event Relationship. On the KER page, clicking on the Event name under Upstream Relationship will bring the user to that individual KE page. More help

Key Event Relationship Overview

The utility of AOPs for regulatory application is defined, to a large extent, by the confidence and precision with which they facilitate extrapolation of data measured at low levels of biological organisation to predicted outcomes at higher levels of organisation and the extent to which they can link biological effect measurements to their specific causes. Within the AOP framework, the predictive relationships that facilitate extrapolation are represented by the KERs. Consequently, the overall WoE for an AOP is a reflection in part, of the level of confidence in the underlying series of KERs it encompasses. Therefore, describing the KERs in an AOP involves assembling and organising the types of information and evidence that defines the scientific basis for inferring the probable change in, or state of, a downstream KE from the known or measured state of an upstream KE. More help

AOPs Referencing Relationship

This table is automatically generated upon addition of a KER to an AOP. All of the AOPs that are linked to this KER will automatically be listed in this subsection. Clicking on the name of the AOP in the table will bring you to the individual page for that AOP. More help
AOP Name Adjacency Weight of Evidence Quantitative Understanding Point of Contact Author Status OECD Status
EGFR Activation Leading to Decreased Lung Function adjacent Moderate Low Cataia Ives (send email) Under development: Not open for comment. Do not cite Under Development

Taxonomic Applicability

Select one or more structured terms that help to define the biological applicability domain of the KER. In general, this will be dictated by the more restrictive of the two KEs being linked together by the KER. Authors can indicate the relevant taxa for this KER in this subsection. The process is similar to what is described for KEs (see pages 30-31 and 37-38 of User Handbook) More help
Term Scientific Term Evidence Link
human Homo sapiens Moderate NCBI
mouse Mus musculus Moderate NCBI
rat Rattus norvegicus High NCBI

Sex Applicability

Authors can indicate the relevant sex for this KER in this subsection. The process is similar to what is described for KEs (see pages 31-32 of the User Handbook). More help
Sex Evidence
Mixed Moderate

Life Stage Applicability

Authors can indicate the relevant life stage for this KER in this subsection. The process is similar to what is described for KEs (see pages 31-32 of User Handbook). More help
Term Evidence
Adult Moderate

Key Event Relationship Description

Provide a brief, descriptive summation of the KER. While the title itself is fairly descriptive, this section can provide details that aren’t inherent in the description of the KEs themselves (see page 39 of the User Handbook). This description section can be viewed as providing the increased specificity in the nature of upstream perturbation (KEupstream) that leads to a particular downstream perturbation (KEdownstream), while allowing the KE descriptions to remain generalised so they can be linked to different AOPs. The description is also intended to provide a concise overview for readers who may want a brief summation, without needing to read through the detailed support for the relationship (covered below). Careful attention should be taken to avoid reference to other KEs that are not part of this KER, other KERs or other AOPs. This will ensure that the KER is modular and can be used by other AOPs. 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). Following EGFR activation, classical downstream activation of the mitogen-activated protein kinase (MAPK)/extracellular signal-regulated kinase (ERK) pathway, also known as Raf/Ras/MAPK/ERK pathway, increases airway epithelial cell proliferation (Lemjabbar et al., 2003; Kim et al., 2005; Hackel et al., 1999) and facilitates epithelial wound repair (Burgel & Nadel, 2004; Van Winkle et al., 1997; Allahverdian et al., 2010). While there is evidence that increased goblet cell proliferation may be the underlying cause of goblet cell hyperplasia (Silva et al., 2012), the key players mediating an increase in airway goblet cell numbers following EGFR activation are still largely unexplored.

Evidence Supporting this KER

Assembly and description of the scientific evidence supporting KERs in an AOP is an important step in the AOP development process that sets the stage for overall assessment of the AOP (see pages 49-56 of the User Handbook). To do this, biological plausibility, empirical support, and the current quantitative understanding of the KER are evaluated with regard to the predictive relationships/associations between defined pairs of KEs as a basis for considering WoE (page 55 of User Handbook). In addition, uncertainties and inconsistencies are considered. More help

Activation of EGFR through direct binding of its ligands EGF, TGFA or epigen or indirectly by oxidative stress following exposure to endotoxin, ozone, ultrafine particles or cigarette smoke induces airway epithelial cell proliferation. While not all studies specifically identify goblet cells as the proliferating cell population, others do - at least indirectly by quantifying the increase in MUC5AC expressing cells (Booth et al., 2001b; Booth et al., 2007; Taniguchi et al., 2011; Sydlik et al., 2006; Tamaoki et al., 2004; Tesfaigzi et al., 1998; Tesfaigzi et al., 2004; Harris et al., 2005; Tamiguchi et al., 2001).

Biological Plausibility
Define, in free text, the biological rationale for a connection between KEupstream and KEdownstream. What are the structural or functional relationships between the KEs? For example, there is a functional relationship between an enzyme’s activity and the product of a reaction it catalyses. Supporting references should be included. However, it is recognised that there may be cases where the biological relationship between two KEs is very well established, to the extent that it is widely accepted and consistently supported by so much literature that it is unnecessary and impractical to cite the relevant primary literature. Citation of review articles or other secondary sources, like text books, may be reasonable in such cases. The primary intent is to provide scientifically credible support for the structural and/or functional relationship between the pair of KEs if one is known. The description of biological plausibility can also incorporate additional mechanistic details that help inform the relationship between KEs, this is useful when it is not practical/pragmatic to represent these details as separate KEs due to the difficulty or relative infrequency with which it is likely to be measured (see page 40 of the User Handbook for further information).   More help

Although there are no studies providing direct evidence for proliferation of goblet cells in the lung following EGFR activation, there is direct in vitro evidence in conjunctival goblet cells (Gu et al., 2008; Shatos et al., 2008) and in murine embryonic colon (Duh et al., 2000). However, multiple studies indirectly demonstrate a link between exposure to stressors known to activate EGFR and increases in goblet cell numbers.

Uncertainties and Inconsistencies
In addition to outlining the evidence supporting a particular linkage, it is also important to identify inconsistencies or uncertainties in the relationship. Additionally, while there are expected patterns of concordance that support a causal linkage between the KEs in the pair, it is also helpful to identify experimental details that may explain apparent deviations from the expected patterns of concordance. Identification of uncertainties and inconsistencies contribute to evaluation of the overall WoE supporting the AOPs that contain a given KER and to the identification of research gaps that warrant investigation (seep pages 41-42 of the User Handbook).Given that AOPs are intended to support regulatory applications, AOP developers should focus on those inconsistencies or gaps that would have a direct bearing or impact on the confidence in the KER and its use as a basis for inference or extrapolation in a regulatory setting. Uncertainties that may be of academic interest but would have little impact on regulatory application don’t need to be described. In general, this section details evidence that may raise questions regarding the overall validity and predictive utility of the KER (including consideration of both biological plausibility and empirical support). It also contributes along with several other elements to the overall evaluation of the WoE for the KER (see Section 4 of the User Handbook).  More help

The majority of studies supporting this KER did not specifically measure goblet cell proliferation. Instead, many studies measured an increase in mucin production upon EGFR activation, equating this with an increase in goblet cell numbers (Takeyama, et al. 2008; Shim et al. 2001; Casalino-Matsuda et al. 2006).

Basal epithelial cells which exhibit stem cell-like properties have also been postulated to function as a source of goblet cells in injured airways, utilizing cell fate pathways that favor secretory cells over other cell populations (Rock et al., 2009). However, both in vitro studies and studies in mouse models of asthma, COPD, and viral infection indicate that EGFR activation leads to transdifferentiation of ciliated or club cells into goblet cells, which is referred to as goblet cell metaplasia, and that goblet cell metaplasia more likely contributes to the expansion of this cell population in the airways (Tyner et al., 2006; Lumsden et al., 1984; Reader et al., 2003; Turner et al., 2011; Evans et al., 2004; Lamb et al., 1968; Shimizu et al., 1998). 

Response-response Relationship
This subsection should be used to define sources of data that define the response-response relationships between the KEs. In particular, information regarding the general form of the relationship (e.g., linear, exponential, sigmoidal, threshold, etc.) should be captured if possible. If there are specific mathematical functions or computational models relevant to the KER in question that have been defined, those should also be cited and/or described where possible, along with information concerning the approximate range of certainty with which the state of the KEdownstream can be predicted based on the measured state of the KEupstream (i.e., can it be predicted within a factor of two, or within three orders of magnitude?). For example, a regression equation may reasonably describe the response-response relationship between the two KERs, but that relationship may have only been validated/tested in a single species under steady state exposure conditions. Those types of details would be useful to capture.  More help

Daily xanthine/xanthine oxidase treatment of human primary bronchial epithelial cells grown at the at the air-liquid interface for 3 days increased the number of MUC5AC-positive cells (from 3.3 ± 1.2% (PBS) to 21.6 ± 3.4%). This increase was prevented by pretreatment with anti-EGFR antibodies (Casalino-Matsuda et al., 2006).

Treatment of human primary bronchial epithelial cells with 1 ng/mL amphiregulin or HB-EGF for 24 h significantly increased the proportion of proliferating cells by approx. 20% (Ki-67 staining and flow cytometry). Treatments with higher concentrations of amphiregulin and HB-EGF did not further increase this proportion (Hirota et al., 2012).

Treatment of murine primary airway epithelial cells growing at the air-liquid interface with 20 ng/mL IL-13 for 14 days doubled the numbers of cells per 5 high-power fields (cell count on hematoxylin/eosin-stained culture sections) and the numbers of PCNA-positive cells by ca. 20% (immunohistochemistry) compared to PBS controls. In addition, [3H]-thymidine incorporation was significantly increased following IL-13 treatment (from ca. 22000 cpm in controls to ca. 33000 cpm). Co-treatment of cultures with IL-13 and the EGFR inhibitor AG1478 (0.25 µg/mL or  0.5 µg/mL) prevented the proliferative response, with greater effects seen at the higher AG1478 concentration (Taniguchi et al., 2011).

Treatment of rat conjunctival goblet cells with 0.1 µM EGF significantly increased phosphorylation of the EGFR by 28.6 ± 7.6- and 29.2 ± 3.2-fold at 1 and 5 minutes, respectively. At the same concentration, 24-hour EGF treatment increased proliferation 4.9 ± 1.8-fold. Pre-treatment with 0.1 µM AG1478 significantly inhibited the EGF response by 87% ± 8%. (Shatos et al., 2008). Similar observations were made with human conjunctival goblet cells: Treatment with 0.1 µM EGF significantly increased proliferation 1.5 ± 0.3-fold above basal (Li et al., 2013). In another study in rat conjunctival goblet cells, treatment with 0.1 µM EGF, TGF-α, or HB-EGF for 5 min significantly stimulated the phosphorylation of EGFR by 21.1 ± 2.5, 22.2 ± 6.7, and 19.9 ± 6.0 fold above basal level, and 24-h treatment stimulated cell proliferation 1.3 ± 0.1 fold, 1.2 ± 0.02 fold, and 1.1 ± 0.04 fold compared to untreated cells (WST-1 assay). These latter results were also confirmed by Ki-67 immunofluorescent staining, showing increases in positive cells by 61.4%, 38.1%, 27.8% following EGF, TGF-α, and HB-EGF treatment compared to untreated cells (Gu et al., 2008).

Approx. 50% of AB/PAS-positive cells were BrdU-positive in the airways of rats at day 2 following instillation of F344 rats with 1 mg LPS, suggesting that they may have been derived from proliferating cells (Tesfaigzi et al., 2004). Intranasal and intratracheal administration of LPS to rats have previously been shown to activate EGFR (Takezawa et a., 2016; Shan et al., 2017).

Treatment of primary human bronchial epithelial cells, grown at the air-liquid interface for 9 days, with 5 ng/mL TGFa or 10 ng/mL IL-13 for 24 h resulted in 1.5- to 2-fold increases in cell numbers (by [3H]thymidine incorporation). These increases were prevented by co-incubation with the EGFR inhibitor AG1478, with maximal decreases (approx. 30%) in cell numbers seen at 5 ng/mL AG1478 (Booth et al., 2001a). Although this study did not specify the affected cell type as goblet cells, another study by the same group using the same model showed that the percentage of AB/PAS–positive, mucus-producing cells increased following IL-13 treatment (Booth et al., 2001b).

This sub-section should be used to provide information regarding the approximate time-scale of the changes in KEdownstream relative to changes in KEupstream (i.e., do effects on KEdownstream lag those on KEupstream by seconds, minutes, hours, or days?). This can be useful information both in terms of modelling the KER, as well as for analyzing the critical or dominant paths through an AOP network (e.g., identification of an AO that could kill an organism in a matter of hours will generally be of higher priority than other potential AOs that take weeks or months to develop). Identification of time-scale can also aid the assessment of temporal concordance. For example, for a KER that operates on a time-scale of days, measurement of both KEs after just hours of exposure in a short-term experiment could lead to incorrect conclusions regarding dose-response or temporal concordance if the time-scale of the upstream to downstream transition was not considered. More help

Proliferation of rat conjunctival goblet cells was observed following stimulation with 100 µM EGF, TGFa or HB-EGF after 14 h, peaking at 18 h (Gu et al., 2008).

The average height of epithelial cells did not increase and hypertrophic airway remodeling was not seen until 48 h after instillation of F344 rats with 1 mg LPS, 46 mucous cells per millimeter of basal lamina (vs 17 in controls) of which 24 mucous cells per millimeter of basal lamina were BrdU-positive (vs 1 in controls) (Tesfaigzi et al., 2004). Intranasal and intratracheal administration of LPS to rats have previously been shown to activate EGFR (Takezawa et a., 2016; Shan et al., 2017).

Treatment of rat lung epithelial RLE-6TN cells with 10 μg/cm2 ultrafine particles moderately but significantly increased DNA synthesis after 24 h (approx. 1.6-fold, BrdU incorporation; approx. 1.5-fold, PCNA staining). Longer incubation did not increase proliferation further. A significant increase in pEGFR  (approx. 3-fold compared to untreated) was observed as early as 2 min following addition of ultrafine particles (10 μg/cm2), and a second more persistent signal was observed from 120 up to 480 min (Sydlik et al., 2006).

Known modulating factors
This sub-section presents information regarding modulating factors/variables known to alter the shape of the response-response function that describes the quantitative relationship between the two KEs (for example, an iodine deficient diet causes a significant increase in the slope of the relationship; a particular genotype doubles the sensitivity of KEdownstream to changes in KEupstream). Information on these known modulating factors should be listed in this subsection, along with relevant information regarding the manner in which the modulating factor can be expected to alter the relationship (if known). Note, this section should focus on those modulating factors for which solid evidence supported by relevant data and literature is available. It should NOT list all possible/plausible modulating factors. In this regard, it is useful to bear in mind that many risk assessments conducted through conventional apical guideline testing-based approaches generally consider few if any modulating factors. More help
Known Feedforward/Feedback loops influencing this KER
This subsection should define whether there are known positive or negative feedback mechanisms involved and what is understood about their time-course and homeostatic limits? In some cases where feedback processes are measurable and causally linked to the outcome, they should be represented as KEs. However, in most cases these features are expected to predominantly influence the shape of the response-response, time-course, behaviours between selected KEs. For example, if a feedback loop acts as compensatory mechanism that aims to restore homeostasis following initial perturbation of a KE, the feedback loop will directly shape the response-response relationship between the KERs. Given interest in formally identifying these positive or negative feedback, it is recommended that a graphical annotation (page 44) indicating a positive or negative feedback loop is involved in a particular upstream to downstream KE transition (KER) be added to the graphical representation, and that details be provided in this subsection of the KER description (see pages 44-45 of the User Handbook).  More help

Domain of Applicability

As for the KEs, there is also a free-text section of the KER description that the developer can use to explain his/her rationale for the structured terms selected with regard to taxonomic, life stage, or sex applicability, or provide a more generalizable or nuanced description of the applicability domain than may be feasible using standardized terms. More help

Epithelial cell proliferation mediated by EGFR has been studied in human (Booth et al., 2001; Booth et al., 2007), mouse (Taniguchi et al., 2011) and rat (Sydlik et al., 2006).


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

Allahverdian, S., Wang, A., Singhera, G.K., Wong, B.W., and Dorscheid, D.R. (2010). Sialyl Lewis X modification of the epidermal growth factor receptor regulates receptor function during airway epithelial wound repair. Clin. Exp. Allergy 40, 607-618.

Booth, B.W., Adler, K.B., Bonner, J.C., Tournier, F., and Martin, L.D. (2001a). Interleukin-13 induces proliferation of human airway epithelial cells in vitro via a mechanism mediated by transforming growth factor-alpha. Am. J. Respir. Cell Mol. Biol. 25, 739–743.

Booth, B., J. C. Bonner, K. B. Adler, and L. D. Martin. (2001b). Autocrine production of TGF mediates interleukin 13-induced proliferation of human airway epithelial cells during development of a mucous phenotype in vitro. Am. J. Respir. Crit. Care Med. 163, A738.

Booth, B.W., Sandifer, T., Martin, E.L., and Martin, L.D. (2007). IL-13-induced proliferation of airway epithelial cells: mediation by intracellular growth factor mobilization and ADAM17. Respir. Res. 8, 51.

Casalino-Matsuda, S., Monzón, M., and Forteza, R. (2006). Epidermal Growth Factor Receptor Activation by Epidermal Growth Factor Mediates Oxidant-Induced Goblet Cell Metaplasia in Human Airway Epithelium. Am. J. Respir. Cell Mol. Biol. 34, 581–591.

Duh, G., Mouri, N., Warburton, D., and Thomas, D.W. (2000). EGF regulates early embryonic mouse gut development in chemically defined organ culture. Pediatr. Res. 48, 794–802.

Gu, J., Chen, L., Shatos, M.A., Rios, J.D., Gulati, A., Hodges, R.R., and Dartt, D.A. (2008). Presence of EGF growth factor ligands and their effects on cultured rat conjunctival goblet cell proliferation. Exp. Eye Res. 86, 322–334.

Hackel, P.O., Zwick, E., Prenzel, N., and Ullrich, A. (1999). Epidermal growth factor receptors: critical mediators of multiple receptor pathways. Curr. Opin. Cell Biol. 11, 184-189.

Harris, J.F., Fischer, M.J., Hotchkiss, J.R., Monia, B.P., Randell, S.H., Harkema, J.R., and Tesfaigzi, Y. (2005). Bcl-2 sustains increased mucous and epithelial cell numbers in metaplastic airway epithelium. Am. J. Respir. Crit. Care Med. 171, 764-772.

Higashiyama, S., Iwabuki, H., Morimoto, C., Hieda, M., Inoue, H., and Matsushita, N. (2008). Membrane-anchored growth factors, the epidermal growth factor family: Beyond receptor ligands. Cancer Sci. 99, 214-220.

Hirota, N., Risse, P.A., Novali, M., McGovern, T., Al-Alwan, L., McCuaig, S., Proud, D., Hayden, P., Hamid, Q., and Martin, J.G. (2012). Histamine may induce airway remodeling through release of epidermal growth factor receptor ligands from bronchial epithelial cells. FASEB J. 26, 1704-1716.

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

Lamb, D., and Reid, L. (1968). Mitotic rates, goblet cell increase and histochemical changes in mucus in rat bronchial epithelium during exposure to sulphur dioxide. J. Pathol. Bacteriol. 96, 97–111.

Lemjabbar, H., Li, D., Gallup, M., Sidhu, S., Drori, E., and Basbaum, C. (2003). Tobacco smoke-induced lung cell proliferation mediated by tumor necrosis factor alpha-converting enzyme and amphiregulin. J. Biol. Chem. 278, 26202-26207.

Li, D., Shatos, M.A., Hodges, R.R., and Dartt, D.A. (2013). Role of PKCα activation of Src, PI-3K/AKT, and ERK in EGF-stimulated proliferation of rat and human conjunctival goblet cells. Invest. Ophthalmol. Vis. Sci. 54, 5661-5674.

Lumsden, A.B., McLean, A., and Lamb, D. (1984). Goblet and Clara cells of human distal airways: evidence for smoking induced changes in their numbers. Thorax 39, 844-849.

Reader, J.R., Tepper, J.S., Schelegle, E.S., Aldrich, M.C., Putney, L.F., Pfeiffer, J.W., et al. (2003). Pathogenesis of mucous cell metaplasia in a murine asthma model. Am. J. Pathol. 162, 2069-2078.

Rock, J.R., Onaitis, M.W., Rawlins, E.L., Lu, Y., Clark, C.P., Xue, Y., et al. (2009). Basal cells as stem cells of the mouse trachea and human airway epithelium. Proc. Natl. Acad. Sci. U.S.A. 106, 12771-12775.

Shan, X., Zhang, Y., Chen, H., Dong, L., Wu, B., Xu, T., et al. (2017). Inhibition of epidermal growth factor receptor attenuates LPS-induced inflammation and acute lung injury in rats. Oncotarget 8, 26648-26661. 

Shatos, M.A., Gu, J., Hodges, R.R., Lashkari, K., and Dartt, D.A. (2008). ERK/p44p42 mitogen-activated protein kinase mediates EGF-stimulated proliferation of conjunctival goblet cells in culture. Invest. Ophthalmol. Vis. Sci. 49, 3351-3359.

Shim, J.J., Dabbagh, K., Ueki, I.F., Dao-Pick, T., Burgel, P.R., Takeyama, K., Tam, D.C., and Nadel, J.A. (2001). IL-13 induces mucin production by stimulating epidermal growth factor receptors and by activating neutrophils. Am. J. Physiol. Lung Cell. Mol. Physiol. 280, L134–L140.

Shimizu, T., Takahashi, Y., Kawaguchi, S., and Sakakura, Y. (1996). Hypertrophic and metaplastic changes of goblet cells in rat nasal epithelium induced by endotoxin. Am. J. Respir. Crit. Care Med. 153, 1412–1418.

Silva, M.A., and Bercik, P. (2012). Macrophages are related to goblet cell hyperplasia and induce MUC5B but not MUC5AC in human bronchus epithelial cells. Lab. Invest. 92, 937-948.

Sydlik, U., Bierhals, K., Soufi, M., Abel, J., Schins, R.P.F., and Unfried, K. (2006). Ultrafine carbon particles induce apoptosis and proliferation in rat lung epithelial cells via specific signaling pathways both using EGF-R. Am. J. Physiol. Lung Cell. Mol. Physiol. 291, L725–L733.

Takeyama, K., Tamaoki, J., Kondo, M., Isono, K., and Nagai, A. (2008). Role of epidermal growth factor receptor in maintaining airway goblet cell hyperplasia in rats sensitized to allergen. Clin. Exp. Allergy 38, 857–865.

Takezawa, K., Ogawa, T., Shimizu, S., and Shimizu, T. (2016). Epidermal growth factor receptor inhibitor AG1478 inhibits mucus hypersecretion in airway epithelium. Am. J. Rhinol. Allergy 30, e1-e6.

Tamaoki, J., Isono, K., Takeyama, K., Tagaya, E., Nakata, J., and Nagai, A. (2004). Ultrafine carbon black particles stimulate proliferation of human airway epithelium via EGF receptor-mediated signaling pathway. Am. J. Physiol. Lung Cell. Mol. Physiol. 287, L1127–L1133.

Taniguchi, K., Yamamoto, S., Aoki, S., Toda, S., Izuhara, K., and Hamasaki, Y. (2011). Epigen is induced during the interleukin-13-stimulated cell proliferation in murine primary airway epithelial cells. Exp. Lung Res. 37, 461–470.

Tesfaigzi, J., Hotchkiss, J.A., and Harkema, J.R. (1998). Expression of the Bcl-2 protein in nasal epithelia of F344/N rats during mucous cell metaplasia and remodeling. Am. J. Respir. Cell Mol. Biol. 18, 794-799.

Tesfaigzi, Y., Harris, J.F., Hotchkiss, J.A., and Harkema, J.R. (2004). DNA synthesis and Bcl-2 expression during development of mucous cell metaplasia in airway epithelium of rats exposed to LPS. Am. J. Physiol. Lung Cell. Mol. Physiol. 286, L268-L274.

Turner, J., Roger, J., Fitau, J., Combe, D., Giddings, J., Heeke, G.V., and Jones, C.E. (2011). Goblet cells are derived from a FOXJ1-expressing progenitor in a human airway epithelium. Am. J. Respir. Cell Mol. Biol. 44, 276–284.

Tyner, J., Tyner, E., Ide, K., Pelletier, M., Roswit, W., Morton, J., Battaile, J., Patel, A., Patterson, G., Castro, M., et al. (2006). Blocking airway mucous cell metaplasia by inhibiting EGFR antiapoptosis and IL-13 transdifferentiation signals. J. Clin. Invest. 116, 309–321.

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