1680
Additionally , although c - fos and egr - 1 mRNAs are expressed at elevated levels in stimulated liver cells , fos - B , fra - 1 , and egr - 2 are not , which suggests that factors in addition to the serum response factor participate in the regulation of immediate - early gene induction .
 c - fos, egr - 1 mRNAs, fos - B, fra - 1, egr - 2, serum response factor, immediate - early gene
Please list all entity words in the text that fit the category. Output format is "word1, word2". 
Option: GENE 
Text: {0} 
Answer:
 c - fos, egr - 1 mRNAs, fos - B, fra - 1, egr - 2, serum response factor, immediate - early gene