13942
Interestingly, the combination of the RAR-selective antagonist and 9-cis RA resulted in partial differentiation and apoptosis of HL-60 and NB4 cells , whereas the RAR antagonist completely blocked all-trans RA -induced differentiation and apoptosis of the cells.
 RAR
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:
 RAR