13937
The biological effects of RA are mediated by two distinct families of transcription factors : retinoic acid receptors ( RARs ) and retinoid X receptors ( RXRs ).
 RARs, transcription factors, retinoid X receptors, RXRs, retinoic acid receptors
Please list all entity words in the text that fit the category. Output format is "word1, word2". 
Option: cell line, protein, RNA, DNA, cell type 
Text: {0} 
Answer:
 RARs, transcription factors, retinoid X receptors, RXRs, retinoic acid receptors