Session 1: High throughput screening assays
Chief Scientific Officer
The mode of action of steroid hormones and interacting “endocrine disrupting” compounds (EDCs) agents is well established.
To be able to accurately assess activation of these receptors in the context of risk assessment of chemicals and complex mixtures of compounds we have established a series of highly specific CALUX reporter gene assays1,2.
These assays have been validated extensively as animal experiment alternatives and submitted for inclusion in OECD guidelines3-12.
We next evaluated the use of estrogen reporter gene assays as a molecular initiating event linking to adversity in animal models, and preferably humans13.
Clearly, dozens of pathways can be drawn from the estrogen receptor alone, leading to beneficial effects and adversity, when addressed inappropriately.
This challenges the use of linear pathways with tests for all intermediate events as a practical tool in risk assessment. We, however, found that predictions of adversity in animal models using estrogen reporter gene assays needs different approaches using clusters of related adverse effects rather than a single type of adversity as an endpoints to validate these assays10,11.
This greatly improves predictions and reduces complexity. We also show that a single specific reporter gene assay gives at least as good prediction of estrogenicity of chemicals as a complex screening panel of 18 less selective assays, as currently used by the US-EPA.
Of further interest is that specificity of assays provides more reliable qualification and allows linkage of test results to adversity induced by the total effect of complex chemical mixtures in the environment14-18 and in epidemiological studies19-21.