9553
Notably, the lack of pRB in these U937-derived clones renders these p53-null cells highly resistant to apoptosis induced by serum withdrawal , calphostin C , and ceramide .
 ( protein: pRB, None) , ( cell line: p53-null cells, None) , ( cell line: U937-derived clones, 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: pRB, None) , ( cell line: p53-null cells, None) , ( cell line: U937-derived clones, None) 