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In this study , we used the cytotoxicity IC ( 50 ) values and transcriptional expression changes as primary endpoints in a shorter 4 - day version of the EST , the molecular embryonic stem cell assay .
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Please list all entity words in the text that fit the category.Output format is "type1: word1; type2: word2". 
Option: Chemical 
Text: {0} 
Answer:
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