Federal agencies accept ICCVAM-recommended testing methods
By Debbie McCarley and Cathy Sprankle
U.S. federal agencies, including NIEHS, have agreed with recommendations on test methods using human cells that can screen substances for their potential to interact with the estrogen receptor. Chemicals that interact with hormone receptors, known as endocrine disruptors or endocrine-active substances, may result in abnormal growth, development, or reproduction.
The Interagency Coordinating Committee on the Validation of Alternative Methods (ICCVAM) evaluated the scientific validity of the proposed methods, the BG1Luc estrogen receptor (ER) transactivation (TA) agonist and antagonist assays, and recommended how they could be used to identify substances that induce or inhibit human ER activity in vitro. Representatives of U.S. Environmental Protection Agency (EPA) responded that they regard the BG1Luc ER TA test methods as an alternative to similar test methods currently used in their Endocrine Disruptor Screening Program. Several agencies also indicated that they would communicate the ICCVAM recommendations to stakeholders and encourage their appropriate use.
In her response to the ICCVAM Committee, NIEHS/NTP Director Linda Birnbaum, Ph.D., noted the advantages offered by the BG1Luc ER TA test methods compared to other methods used to measure interaction with the estrogen receptor. “NIEHS and the NTP will … promote and encourage the consideration and use of the BG1Luc ER TA for research and testing where determined appropriate,” she wrote. “These alternative test methods should be routinely considered and used where appropriate, in order to avoid or minimize animal use.”
Endocrine-active substances mimic or block the action of hormones, causing adverse health effects, by interfering with normal hormone function. Evidence suggests that environmental exposure to endocrine-active substances may cause reproductive and developmental problems in humans and wildlife. There is also concern that exposure to endocrine-active substances may increase cancer incidence in humans.
The Food Quality Protection Act of 1996 directed the EPA to screen pesticides and environmental contaminants for their potential to affect the endocrine systems of humans and wildlife. The EPA subsequently initiated an endocrine disruptor screening program, and began efforts to standardize and validate test methods to include in the program. At the request of EPA, ICCVAM and the NTP Interagency Center for the Evaluation of Alternative Toxicological Methods (NICEATM), which administers ICCVAM and provides scientific support for its activities, reviewed the validation status of in vitro test methods, and developed guidance for future validation studies. NICEATM then conducted validation studies of in vitro test methods that could identify potential endocrine disruptors without using animals.
The subject of one of these validation studies was the BG1Luc ER TA agonist and antagonist assays, also known as the LUMI-CELL® ER test method. Xenobiotic Detection Systems Inc. (XDS) developed the LUMI-CELL® ER test method with the support of an NIEHS Small Business Innovation Research grant. NICEATM coordinated an international validation study of the BG1Luc ER TA agonist and antagonist assays at laboratories in Europe, the United States, and Japan.
The ICCVAM recommendations on the BG1Luc ER TA test methods were based on data from the NICEATM-sponsored independent validation studies. In developing the recommendations, ICCVAM considered comments from its scientific advisory committee, an independent scientific peer review panel and members of the public.
NICEATM also nominated the BG1Luc ER TA test methods for evaluation in Tox21. The assays have now been adapted to a high-throughput format using 1536-well plates by the National Center for Advancing Translational Sciences and have been used to screen all compounds in the Tox21 10K chemical library.
Details on the ICCVAM evaluation of the BG1Luc ER TA test methods, including a recommended protocol, more information on the ICCVAM recommendations, and the agency responses, can be found on the NICEATM-ICCVAM website.
(Debbie McCarley is a special assistant to Stokes. Cathy Sprankle is a communications specialist with ILS, Inc., support contractor for NICEATM.)