2550
Hypoxia - inducible factor - 1 ( HIF - 1 ) is one of the key mammalian transcription factors and shows increased levels in both protein stability and intrinsic transcriptional activity during low oxygen tension .
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Please list all entity words in the text that fit the category. Output format is "word1, word2". 
Option: Anatomy 
Text: {0} 
Answer:
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