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To explore the receptor signaling pathways involved in RA -induced apoptosis , we used selective ligands for retinoic acid receptors ( RARs ; RO13-7410) and retinoid X receptors ( RXRs ; RO 25-6603).
 RXRs, retinoic acid receptors, retinoid X 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:
 RXRs, retinoic acid receptors, retinoid X receptors