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Relationship: 774


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

Increase, Preneoplastic foci (hepatocytes) leads to Increase, hepatocellular adenomas and carcinomas

Upstream event
The causing Key Event (KE) in a Key Event Relationship (KER). More help
Downstream event
The responding Key Event (KE) in a Key Event Relationship (KER). 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

AOP Name Adjacency Weight of Evidence Quantitative Understanding Point of Contact Author Status OECD Status
Constitutive androstane receptor activation leading to hepatocellular adenomas and carcinomas in the mouse and the rat adjacent High Not Specified Brendan Ferreri-Hanberry (send email) Open for citation & comment Under Review
Androgen receptor activation leading to hepatocellular adenomas and carcinomas (in mouse and rat) adjacent Evgeniia Kazymova (send email) Open for adoption Under Development
Chronic cytotoxicity leading to hepatocellular adenomas and carcinomas (in mouse and rat) adjacent Cataia Ives (send email) Under Development: Contributions and Comments Welcome

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
rat Rattus norvegicus High NCBI
mouse Mus musculus High NCBI

Sex Applicability

An indication of the the relevant sex for this KER. More help
Sex Evidence
Mixed High

Life Stage Applicability

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

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

Clonally expanded cells (foci of cellular alteration – either eosinophilic, basophilic or clear cell) have been shown to be increased at tumorigenic dose levels of CAR activators such as phenobarbital, TCPOBOP and metofluthrin. As discussed for earlier key events, the CAR-mediated events that lead to an increase in altered foci lead to a greater abundance of cells with mutations in their DNA that are less responsive to normal cell-cell signaling and control mechanisms. As a result, these foci are considered preneoplastic lesions, and can progress with time into adenomas and carcinomas. The continued CAR-mediated stimulus for increased cell proliferation within these foci (e.g. as demonstrated in studies by Kolaja et al., 1996b) will also provide an environment where the mutant cells can survive and develop into tumors.

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

The development of liver tumors in rodents, whether spontaneously or induced by a non-genotoxic carcinogen, has consistently included the development of altered foci as a precursor step to hepatocellular adenomas and carcinomas (Goldsworthy and Fransson-Steen, 2002; Tamura et al., 2015). These foci are considered preneoplastic lesions, and their ability to progress to form adenomas and/or carcinomas in rodents has been previously recognized. In the case of CAR activators, an increased incidence of preneoplastic foci has been consistently shown to precede tumor development, and there is a high biological plausibility for this Key Event Relationship (Elcombe et al., 2014; Goldsworthy and Fransson-Steen, 2002; Jones et al., 2009; Lake, 2009).

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

The incidence of altered foci, and their staining properties (e.g. eosinophilic, basophilic, clear cell, mixed) are not always reported in published studies of carcinogenicity with CAR activation compounds. However, the consistent findings with well-known CAR activating compounds and their absence in CAR knockout mouse studies provide a strong basis for their existence in the CAR AOP.

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

Phenobarbital and other CAR activators do not produce liver tumors in long term studies in hamsters (Diwan et al., 1986; Elcombe et al., 2014). Consistent with the lack of effects on proliferation and on tumor development, Diwan et al. (1986) also reported that phenobarbital treatment at 500 ppm in the drinking water did not produce any increases in preneoplastic foci of cellular alteration compared to groups that received an initiator alone. Further, treatment of CAR knockout mice lacking the CAR nuclear receptor with phenobarbital or TCPOBOP produced none of the early key events (e.g. altered expression of CAR-responsive cell cycle genes, increased cell proliferation) and no increases in altered foci or tumors (Huang et al., 2005; Yamamoto et al., 2004). Therefore, the development of increased foci in the liver in response to treatment with CAR activators has strong data indicating it is specific to mice and rats, the species which also develop hepatocellular tumors in response to known CAR activators.


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

[see reference list at end of this AOP; it includes all cited references]