23769
Immunohistochemical analysis was performed on Ki - 67 , p21 ( Cip1 ) and M phase proteins [ nuclear Cdc2 , phospho - Histone H3 ( p - Histone H3 ) , Aurora B and heterochromatin protein 1 alpha ( HP1 alpha ) ] with carcinogens targeting different organs .
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Please list all entity words in the text that fit the category. Output format is "word1, word2". 
Option: Chemical 
Text: {0} 
Answer:
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