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To explore the molecular basis for CPT hypersensitivity in Top2 beta - deficient cells , we found that upon CPT exposure , the RNA polymerase II large subunit ( RNAP LS ) became progressively depleted , followed by recovery to nearly the original level in wild - type MEFs , whereas RNAP LS remained depleted without recovery in Top2 beta - deficient cells .
 Chemical: CPT; Chemical: CPT
Please list all entity words in the text that fit the category.Output format is "type1: word1; type2: word2". 
Option: Chemical 
Text: {0} 
Answer:
 Chemical: CPT; Chemical: CPT