9519
RXR-alpha mRNA was present in untreated U937 cells , and levels increased after induction of differentiation with phorbol ester .
 RXR-alpha, U937 cells, RXR-alpha mRNA
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:
 RXR-alpha, U937 cells, RXR-alpha mRNA