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In addition , we find that miR - 22 is activated by the transcription factor Myc when quiescent cells enter proliferation and that miR - 22 inhibits the Myc transcriptional repressor MXD4 , mediating a feed - forward loop to elevate Myc expression levels .
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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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