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Indeed , alteration of the pattern of DNA methylation has been a constant finding in cancer cells of the same type and differences in the pattern of DNA methylation not only occur in a variety of tumor types , but also in developmental processes Furthermore , the pattern of histone modification appears to be a predicator of the risk of recurrence of human cancers .
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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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