1424
PKC-zeta cells expressed a more differentiated phenotype as assessed by changes in morphology, surface antigen expression, and lysosomal enzyme activities and were distinct from parental U937 cells stimulated to differentiate by exposure to phorbol esters .
 ( protein: PKC-zeta, None) , ( protein: lysosomal enzyme, None) , ( cell line: parental U937 cells, None) , ( cell line: PKC-zeta cells, None) , ( cell line: U937 cells, 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: PKC-zeta, None) , ( protein: lysosomal enzyme, None) , ( cell line: parental U937 cells, None) , ( cell line: PKC-zeta cells, None) , ( cell line: U937 cells, None) 