Phenotypic screening of the ToxCast chemical library to classify toxic and therapeutic mechanisms.
Addressing the safety aspects of drugs and environmental chemicals has historically been undertaken through animal testing. However, the quantity of chemicals in need of assessment and the challenges of species extrapolation require the development of alternative approaches. Our approach, the US Environmental Protection Agency's ToxCast program, utilizes a large suite of in vitro and model organism assays to interrogate important chemical libraries and computationally analyze bioactivity profiles. Here we evaluated one component of the ToxCast program, the use of primary human cell systems, by screening for chemicals that disrupt physiologically important pathways. Chemical-response signatures for 87 endpoints covering molecular functions relevant to toxic and therapeutic pathways were generated in eight cell systems for 641 environmental chemicals and 135 reference pharmaceuticals and failed drugs. Computational clustering of the profiling data provided insights into the polypharmacology and potential off-target effects for many chemicals that have limited or no toxicity information. The endpoints measured can be closely linked to in vivo outcomes, such as the upregulation of tissue factor in endothelial cell systems by compounds linked to the risk of thrombosis in vivo. Our results demonstrate that assaying complex biological pathways in primary human cells can identify potential chemical targets, toxicological liabilities and mechanisms useful for elucidating adverse outcome pathways.
National Center for Computational Toxicology, Office of Research and Development, United States Environmental Protection Agency, Research Triangle Park, North Carolina, USA.
Nicole C
NC
Kleinstreuer
BioSeek, a division of DiscoveRx, Inc., S. San Francisco, California, USA.
Jian
J
Yang
BioSeek, a division of DiscoveRx, Inc., S. San Francisco, California, USA.
Ellen L
EL
Berg
National Center for Computational Toxicology, Office of Research and Development, United States Environmental Protection Agency, Research Triangle Park, North Carolina, USA.
Thomas B
TB
Knudsen
National Center for Computational Toxicology, Office of Research and Development, United States Environmental Protection Agency, Research Triangle Park, North Carolina, USA.
Ann M
AM
Richard
National Center for Computational Toxicology, Office of Research and Development, United States Environmental Protection Agency, Research Triangle Park, North Carolina, USA.
Matthew T
MT
Martin
National Center for Computational Toxicology, Office of Research and Development, United States Environmental Protection Agency, Research Triangle Park, North Carolina, USA.
David M
DM
Reif
National Center for Computational Toxicology, Office of Research and Development, United States Environmental Protection Agency, Research Triangle Park, North Carolina, USA.
Richard S
RS
Judson
BioSeek, a division of DiscoveRx, Inc., S. San Francisco, California, USA.
Mark
M
Polokoff
National Center for Computational Toxicology, Office of Research and Development, United States Environmental Protection Agency, Research Triangle Park, North Carolina, USA.
David J
DJ
Dix
National Center for Computational Toxicology, Office of Research and Development, United States Environmental Protection Agency, Research Triangle Park, North Carolina, USA.
Robert J
RJ
Kavlock
National Center for Computational Toxicology, Office of Research and Development, United States Environmental Protection Agency, Research Triangle Park, North Carolina, USA.
Keith A
KA
Houck
D000826:Animal Testing Alternatives / Q000379:methods*; D000818:Animals; D003198:Computer Simulation; D057166:High-Throughput Screening Assays / Q000379:methods*; D006801:Humans; D051379:Mice; D008954:Models, Biological; D010641:Phenotype; D051381:Rats; D054852:Small Molecule Libraries; D018675:Toxicity Tests / Q000379:methods*; D014481:United States; D014484:United States Environmental Protection Agency
D054852:Small Molecule Libraries