1129
Human RAR alpha was expressed in H9 , U937 and THP-1 cells , but almost undetectable in CEM cells .
 Human RAR alpha, H9, THP-1 cells, CEM cells, U937
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:
 Human RAR alpha, H9, THP-1 cells, CEM cells, U937