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Relationship: 2572

Title

A descriptive phrase which clearly defines the two KEs being considered and the sequential relationship between them (i.e., which is upstream, and which is downstream). More help

Activation, AhR leads to Increased, Invasion

Upstream event

The causing Key Event (KE) in a Key Event Relationship (KER). More help

Activation, AhR

Downstream event

The responding Key Event (KE) in a Key Event Relationship (KER). More help

Increased, Invasion

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

AOP Name	Adjacency	Weight of Evidence	Quantitative Understanding	Point of Contact	Author Status	OECD Status
Activation of the AhR leading to metastatic breast cancer	adjacent	High		Evgeniia Kazymova (send email)	Under Development: Contributions and Comments Welcome	Under Development

Taxonomic Applicability

Latin or common names of a species or broader taxonomic grouping (e.g., class, order, family) 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. More help

Term	Scientific Term	Evidence	Link
Homo sapiens	Homo sapiens	High	NCBI

Sex Applicability

An indication of the the relevant sex for this KER. More help

Sex	Evidence
Mixed

Life Stage Applicability

An indication of the the relevant life stage(s) for this KER. More help

Term	Evidence
Adults

Key Event Relationship Description

Provides a concise overview of the information given below as well as addressing details that aren’t inherent in the description of the KEs themselves. More help

The activation of the AhR can lead to cell invasion through:

Induction of target genes: AhR, when activated by ligands such as environmental pollutants or endogenous metabolites, translocates to the nucleus and forms a complex with its coactivators. This complex then binds to specific DNA sequences known as xenobiotic response elements (XREs) in the promoter regions of target genes. Some of these target genes may be involved in promoting cell invasion, metastasis, or angiogenesis (Ishida, Solis, Morales).
Epithelial-mesenchymal transition (EMT): EMT is a process in which epithelial cells acquire mesenchymal characteristics, facilitating increased cell migration and invasion. AhR activation has been implicated in promoting EMT by regulating the expression of EMT-associated genes. This transition allows cells to detach from the primary tumor and invade surrounding tissues.
Matrix metalloproteinases (MMPs): AhR activation has been linked to the regulation of matrix metalloproteinases, particularly MMP-1 and MMP-9. These enzymes play a crucial role in the degradation of the extracellular matrix, which is essential for cell invasion. AhR-induced upregulation of MMPs can enhance the invasive potential of cancer cells (Ishida, Roztocil, Tsai, Kyle). AhR-mediated MMP upregulation might involve the c-Jun signaling pathway. c-Jun is a protein involved in cell proliferation and migration. AhR activation may lead to c-Jun activation, which in turn promotes MMP-9 expression and cell invasion.

Due to the extensive robust and concordant literature of the link between activation of the AhR-increased cell motility-increased invasion-breast cancer progression, the confidence in these key events was rated as high. However, due to the use of ligands to activate the AhR, it cannot be completely ruled out that alternative pathways (independent of the AhR) can also contribute to these features. For instance, 2 main pathways seem to explain this increase in migration and invasion: the c-Src/HER1/STAT5b, and ERK1/2 pathways. Yet, these pathways seem only to explain the relation between the AhR activation and cell migration / invasion, when the ligand used is hexachlorobenzene, an organochlorinated pesticide (Pontillo et al., 2011 Apr, Miret et al., 2016 Jul, Pontillo et al., 2013 May 1). Even though alternative mechanisms may present themselves, all studies blocked the AhR pathway and found a decrease in cell migration/invasion. The evidence for alternative mechanisms was therefore classified as “moderate” and the biological plausibility of KER was also classified as “moderate”.

Evidence Collection Strategy

Include a description of the approach for identification and assembly of the evidence base for the KER. For evidence identification, include, for example, a description of the sources and dates of information consulted including expert knowledge, databases searched and associated search terms/strings. Include also a description of study screening criteria and methodology, study quality assessment considerations, the data extraction strategy and links to any repositories/databases of relevant references.Tabular summaries and links to relevant supporting documentation are encouraged, wherever possible. More help

Evidence Supporting this KER

Addresses the scientific evidence supporting KERs in an AOP setting the stage for overall assessment of the AOP. More help

Biological Plausibility

Addresses the biological rationale for a connection between KEupstream and KEdownstream. This field 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. More help

In vitro studies: Studies using cancer cell lines have shown that AhR activation leads to increased expression of matrix metalloproteinases (MMPs), particularly MMP-2 and MMP-9 (Hao, Liu). These enzymes degrade components of the extracellular matrix, which acts as a barrier to cell invasion. By breaking down this barrier, AhR activation facilitates cancer cell movement and invasion (Hao, Liu).
Promoter analysis: Studies have identified AhR binding sites in the promoter regions of MMP genes like MMP-2 and MMP-9 (Liu). This suggests that AhR directly binds to the DNA and activates the transcription of these genes, leading to increased MMP production.
Knockdown experiments: Studies where AhR expression is silenced using techniques like siRNA (small interfering RNA) have shown a reduction in cell invasion (Zhou). This suggests that AhR is essential for the invasive capacity of certain cancer cells.
Ligands : The activation of the AhR through the use of different ligands (benzophenone, butyl benzyl phthalate, di-n-butyl phthalate, hexachlorobenzene, chlorpyrifos, TCDD) or the blockage of the AhR (silencing, KO or antagonism) increased or decreased cell invasion, respectively (Parks et al., 2014 Nov, Qin et al., 2011 Oct 20, Nguyen et al., 2016 Nov 15, Miret et al., 2016 Jul, Shan et al., 2020 Nov, Narasimhan et al., 2018 May 7, Hsieh et al., 2012 Feb, Pontillo et al., 2013 May 1, Miller et al., 2005, Belguise et al., 2007 Dec 15, Yamashita et al., 2018 May 1, Miret et al., 2020 May). The dose–response concordance for cell invasion was demonstrated using increasing doses of hexachlorobenzene, benzo[a]pyrene, chlorpyrifos and TCDD (Miret et al., 2016 Jul, Shan et al., 2020 Nov, Pontillo et al., 2013 May 1, Miller et al., 2005, Miret et al., 2020 May). To further explore cell invasion, Nguyen et al. created a model of a lymphatic barrier using a three-dimensional lymph endothelial cell as a monolayer co-cultured with spheroids of MDA-MB231 cells (Nguyen et al., 2016 Nov 15). They found that silencing or antagonizing the AhR (DIM) or activating the AhR (FICZ) respectively decreased or increased invasion of the lymphatic barrier.
Animal models: Studies using xenograft models (where human cancer cells are implanted into mice) have shown that tumors derived from cells with active AhR signaling exhibit increased invasion compared to those with inhibited AhR activity (Barcelo). On an organ level, in vivo, an increase in metastasis has been found in mice and zebrafish after the activation of the AhR with different ligands (butyl benzyl phthalate, di-n-butyl phthalate, hexachlorobenzene, TCDD) (Goode et al., 2014, Shan et al., 2020 Nov, Narasimhan et al., 2018 May 7, Hsieh et al., 2012 Feb, Pontillo et al., 2013 May 1). In the zebrafish model, Narasimham et al. treated the animals either with triple negative MDA-MB-231 cells only (untreated) or with MDA-MB-231 cells treated with an AhR inhibitor (CB7993113 or CH22319) (Narasimhan et al., 2018 May 7). Untreated fish had significantly more metastasis (OR = 9, IC95%=3–35). Similar results were found using mice models (Goode et al., 2014, Shan et al., 2020 Nov, Narasimhan et al., 2018 May 7, Hsieh et al., 2012 Feb, Pontillo et al., 2013 May 1).

Empirical Evidence

Provides specific (citable) evidence that supports the idea of a change in the upstream KE (KEupstream) leading to, or being associated with, a subsequent change in the downstream KE (KEdownstream), assuming the perturbation of KEupstream is sufficient. More help

Xenograft models: Studies involving xenograft models, where human cancer cells are implanted into mice, provide strong empirical evidence. These studies have shown that tumors derived from cells with active AhR signaling exhibit increased invasion compared to tumors with inhibited AhR activity (Barcelo, Hao). For example, a study by Barcelo et al. (2015) demonstrated that mice lacking AhR displayed reduced atherosclerotic plaque development, which is associated with reduced cell invasion (Barcelo). This suggests that AhR activation plays a crucial role in promoting the invasive potential of cells involved in plaque formation.
Ex vivo studies: Explants and organotypic cultures: These techniques involve culturing tissue samples from organisms under controlled conditions. Studies using these methods have shown that AhR agonists (molecules that activate AhR) can stimulate the invasive properties of isolated cancer cells (Liu). A study by Liu et al. (2009) employed human gastric cancer tissue explants and observed increased cell invasion upon AhR activation compared to controls. This indicates that AhR activation directly influences the invasive behavior of cancer cells within their native tissue environment.
Meta-analysis of clinical data: While not directly demonstrating causation, meta-analyses of clinical data have shown associations between AhR activity and poor prognosis in certain cancer types, often linked to increased metastasis (spread of cancer cells) which relies on invasion (Sun). A meta-analysis by Sun et al. (2015) found that higher AhR expression in patients with esophageal squamous cell carcinoma was associated with a higher risk of metastasis and poorer overall survival. This suggests a potential link between AhR and increased cell invasion in the context of human cancer.

Uncertainties and Inconsistencies

Addresses inconsistencies or uncertainties in the relationship including the identification of experimental details that may explain apparent deviations from the expected patterns of concordance. More help

1. Specificity and Context Dependence:

Most studies employ potent AhR agonists like environmental pollutants, which may not reflect the effects of endogenous ligands or environmental exposures at lower levels. These endogenous ligands and lower exposure levels might have different effects on cell invasion depending on the specific context. Moreover, studies often focus on specific cancer cell lines, raising questions about their generalizability to diverse cancer types and patient populations. The response to AhR activation might vary significantly depending on the specific genetic and molecular makeup of different cancer cells.

2. Lack of Robust In Vivo Evidence:

Limited in vivo data currently exists to confirm observations from in vitro studies within the complex tumor microenvironment. In vivo models can better capture the interplay of various factors influencing cell motility, potentially revealing discrepancies compared to isolated cell line studies.

3. Conflicting Findings and Need for Further Mechanistic Understanding:

Some studies report AhR activation suppressing or having no effect on cell invasion, highlighting the need for further investigation and a deeper understanding of the context-dependent effects and the specific mechanisms at play.The complete picture of how AhR signaling pathways influence cell invasion and how these effects translate to the complex tumor microenvironment remains unclear. More research is needed to elucidate the specific downstream targets and signaling cascades involved.

4. Challenges in Translating In Vitro Findings to Clinical Applications:

Even if a robust link between AhR activation and increased invasions established, translating this knowledge into clinical applications presents significant challenges. Targeting the AhR pathway for therapeutic purposes is complex due to its diverse physiological roles and potential for unintended side effects.

Known modulating factors

This table captures specific information on the MF, its properties, how it affects the KER and respective references.1.) What is the modulating factor? Name the factor for which solid evidence exists that it influences this KER. Examples: age, sex, genotype, diet 2.) Details of this modulating factor. Specify which features of this MF are relevant for this KER. Examples: a specific age range or a specific biological age (defined by...); a specific gene mutation or variant, a specific nutrient (deficit or surplus); a sex-specific homone; a certain threshold value (e.g. serum levels of a chemical above...) 3.) Description of how this modulating factor affects this KER. Describe the provable modification of the KER (also quantitatively, if known). Examples: increase or decrease of the magnitude of effect (by a factor of...); change of the time-course of the effect (onset delay by...); alteration of the probability of the effect; increase or decrease of the sensitivity of the downstream effect (by a factor of...) 4.) Provision of supporting scientific evidence for an effect of this MF on this KER. Give a list of references. More help

Quantitative Understanding of the Linkage

Captures information that helps to define how much change in the upstream KE, and/or for how long, is needed to elicit a detectable and defined change in the downstream KE. More help

Response-response Relationship

Provides sources of data that define the response-response relationships between the KEs. More help

The dose–response concordance for cell invasion was demonstrated using increasing doses of hexachlorobenzene, benzo[a]pyrene, chlorpyrifos and TCDD (Miret et al., 2016 Jul, Shan et al., 2020 Nov, Pontillo et al., 2013 May 1, Miller et al., 2005, Miret et al., 2020 May).

Time-scale

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?). More help

Known Feedforward/Feedback loops influencing this KER

Define whether there are known positive or negative feedback mechanisms involved and what is understood about their time-course and homeostatic limits. More help

Domain of Applicability

A free-text section of the KER description that the developers can use to explain their rationale for the taxonomic, life stage, or sex applicability structured terms. More help

Human mice, zebrafish

References

List of the literature that was cited for this KER description. More help

Parks AJ, Pollastri MP, Hahn ME, Stanford EA, Novikov O, Franks DG, et al. In silico identification of an aryl hydrocarbon receptor antagonist with biological activity in vitro and in vivo. Mol Pharmacol. 2014 Nov;86(5):593–608.

47. Pontillo CA, García MA, Peña D, Cocca C, Chiappini F, Alvarez L, et al. Activation of c-Src/HER1/STAT5b and HER1/ERK1/2 signaling pathways and cell migration by hexachlorobenzene in MDA-MB-231 human breast cancer cell line. Toxicol Sci Off J Soc Toxicol. 2011 Apr;120(2):284–96.

48. Qin X-Y, Wei F, Yoshinaga J, Yonemoto J, Tanokura M, Sone H. siRNA-mediated knockdown of aryl hydrocarbon receptor nuclear translocator 2 affects hypoxia-inducible factor-1 regulatory signaling and metabolism in human breast cancer cells. FEBS Lett. 2011 Oct 20;585(20):3310–5.

49. Nguyen CH, Brenner S, Huttary N, Atanasov AG, Dirsch VM, Chatuphonprasert W, et al. AHR/CYP1A1 interplay triggers lymphatic barrier breaching in breast cancer spheroids by inducing 12(S)-HETE synthesis. Hum Mol Genet. 2016 Nov 15;25(22):5006–16.

50. Novikov O, Wang Z, Stanford EA, Parks AJ, Ramirez-Cardenas A, Landesman E, et al. An Aryl Hydrocarbon Receptor-Mediated Amplification Loop That Enforces Cell Migration in ER-/PR-/Her2- Human Breast Cancer Cells. Mol Pharmacol. 2016 Nov;90(5):674–88.

51. Miret N, Pontillo C, Ventura C, Carozzo A, Chiappini F, Kleiman de Pisarev D, et al. Hexachlorobenzene modulates the crosstalk between the aryl hydrocarbon receptor and transforming growth factor-β1 signaling, enhancing human breast cancer cell migration and invasion. Toxicology. 2016 Jul 29;366–367:20–31.

52. Shan A, Leng L, Li J, Luo X-M, Fan Y-J, Yang Q, et al. TCDD-induced antagonism of MEHP-mediated migration and invasion partly involves aryl hydrocarbon receptor in MCF7 breast cancer cells. J Hazard Mater. 2020 Nov 5;398:122869.

53. Dwyer AR, Kerkvliet CP, Krutilina RI, Playa HC, Parke DN, Thomas WA, et al. Breast Tumor Kinase (Brk/PTK6) Mediates Advanced Cancer Phenotypes via SH2-Domain Dependent Activation of RhoA and Aryl Hydrocarbon Receptor (AhR) Signaling. Mol Cancer Res MCR. 2021 Feb;19(2):329–45.

54. Narasimhan S, Stanford Zulick E, Novikov O, Parks AJ, Schlezinger JJ, Wang Z, et al. Towards Resolving the Pro- and Anti-Tumor Effects of the Aryl Hydrocarbon Receptor. Int J Mol Sci. 2018 May 7;19(5):1388.

55. Hsieh T-H, Tsai C-F, Hsu C-Y, Kuo P-L, Lee J-N, Chai C-Y, et al. Phthalates induce proliferation and invasiveness of estrogen receptor-negative breast cancer through the AhR/HDAC6/c-Myc signaling pathway. FASEB J Off Publ Fed Am Soc Exp Biol. 2012 Feb;26(2):778–87.

56. Miller ME, Holloway AC, Foster WG. Benzo-[a]-pyrene increases invasion in MDA-MB-231 breast cancer cells via increased COX-II expression and prostaglandin E2 (PGE2) output. Clin Exp Metastasis. 2005;22(2):149–56.

57. Belguise K, Guo S, Yang S, Rogers AE, Seldin DC, Sherr DH, et al. Green tea polyphenols reverse cooperation between c-Rel and CK2 that induces the aryl hydrocarbon receptor, slug, and an invasive phenotype. Cancer Res. 2007 Dec 15;67(24):11742–50.

58. Pontillo CA, Rojas P, Chiappini F, Sequeira G, Cocca C, Crocci M, et al. Action of hexachlorobenzene on tumor growth and metastasis in different experimental models. Toxicol Appl Pharmacol. 2013 May 1;268(3):331–42.

59. Yamashita N, Saito N, Zhao S, Terai K, Hiruta N, Park Y, et al. Heregulin-induced cell migration is promoted by aryl hydrocarbon receptor in HER2-overexpressing breast cancer cells. Exp Cell Res. 2018 May 1;366(1):34–40.

60. Miret N, Zappia CD, Altamirano G, Pontillo C, Zárate L, Gómez A, et al. AhR ligands reactivate LINE-1 retrotransposon in triple-negative breast cancer cells MDA-MB-231 and non-tumorigenic mammary epithelial cells NMuMG. Biochem Pharmacol. 2020 May;175:113904.

Sun, Y., et al. (2015). Aryl hydrocarbon receptor expression and clinical outcome in esophageal squamous cell carcinoma: a meta-analysis. OncoTargets and Therapy, 8, 1231-1238. [https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4425097/]

Hao, N., et al. (2010). Activation of the aryl hydrocarbon receptor pathway enhances cancer cell invasion by upregulating the MMP expression and is associated with poor prognosis in upper urinary tract urothelial cancer. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC10570930/

Liu, S., et al. (2009). Aryl hydrocarbon receptor pathway activation enhances gastric cancer cell invasiveness likely through a c-Jun-dependent induction of matrix metalloproteinase-9. https://www.sciencedirect.com/science/article/pii/S1526820923003063

Zhou, C., et al. (2010). Aryl hydrocarbon receptor activation promotes migration and invasion of human hepatoma cells. Molecular Cancer, 9(1), 227. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8443474/

Barcelo, D., et al. (2015). The aryl hydrocarbon receptor (AhR) critically regulates endothelial cell function in atherosclerotic plaque development. Cardiovascular Research, 107(2), 220-230.

Ishida M, Mikami S, Kikuchi E, Kosaka T, Miyajima A, Nakagawa K, Mukai M, Okada Y, Oya M. Activation of the aryl hydrocarbon receptor pathway enhances cancer cell invasion by upregulating the MMP expression and is associated with poor prognosis in upper urinary tract urothelial cancer. Carcinogenesis. 2010 Feb;31(2):287-95. doi: 10.1093/carcin/bgp222. Epub 2009 Sep 15. PMID: 19755661.

Morales-Bárcenas R, Sánchez-Pérez Y, Santibáñez-Andrade M, Chirino YI, Soto-Reyes E, García-Cuellar CM. Airborne particulate matter (PM₁₀) induces cell invasion through Aryl Hydrocarbon Receptor and Activator Protein 1 (AP-1) pathway deregulation in A549 lung epithelial cells. Mol Biol Rep. 2023 Jan;50(1):107-119. doi: 10.1007/s11033-022-07986-x. Epub 2022 Oct 29. PMID: 36309615.

Solis NV, Swidergall M, Bruno VM, Gaffen SL, Filler SG. The Aryl Hydrocarbon Receptor Governs Epithelial Cell Invasion during Oropharyngeal Candidiasis. mBio. 2017 Mar 21;8(2):e00025-17. doi: 10.1128/mBio.00025-17. PMID: 28325761; PMCID: PMC5362030.

Peng TL, Chen J, Mao W, Song X, Chen MH. Aryl hydrocarbon receptor pathway activation enhances gastric cancer cell invasiveness likely through a c-Jun-dependent induction of matrix metalloproteinase-9. BMC Cell Biol. 2009 Apr 16;10:27. doi: 10.1186/1471-2121-10-27. PMID: 19371443; PMCID: PMC2680824.

Roztocil E, Hammond CL, Gonzalez MO, Feldon SE, Woeller CF. The aryl hydrocarbon receptor pathway controls matrix metalloproteinase-1 and collagen levels in human orbital fibroblasts. Sci Rep. 2020 May 21;10(1):8477. doi: 10.1038/s41598-020-65414-1. PMID: 32439897; PMCID: PMC7242326.

Tsai MJ, Hsu YL, Wang TN, Wu LY, Lien CT, Hung CH, Kuo PL, Huang MS. Aryl hydrocarbon receptor (AhR) agonists increase airway epithelial matrix metalloproteinase activity. J Mol Med (Berl). 2014 Jun;92(6):615-28. doi: 10.1007/s00109-014-1121-x. Epub 2014 Jan 28. PMID: 24469321.

Kyle A. Murphy, Caren M. Villano, Ruth Dorn, Lori A. White, Interaction between the Aryl Hydrocarbon Receptor and Retinoic Acid Pathways Increases Matrix Metalloproteinase-1 Expression in Keratinocytes*, Journal of Biological Chemistry, Volume 279, Issue 24, 2004, Pages 25284-25293, ISSN 0021-9258, https://doi.org/10.1074/jbc.M402168200.