712
PU.1 expression is maintained at stable levels during differentiation of myeloid cell lines U937 and HL-60 to monocytic and neutrophilic cells .
 ( protein: PU.1, None) , ( cell line: myeloid cell lines, None) , ( cell line: HL-60, None) , ( cell line: U937, None) 
Locate the role in the text that participated in the event based on the event type and return it in the event list. 
 Option: Event type: RNA,cell type,protein,cell line,DNA, Arguments type: . 
Text: {0} 
Answer:
 ( protein: PU.1, None) , ( cell line: myeloid cell lines, None) , ( cell line: HL-60, None) , ( cell line: U937, None) 