11619
These E1a reiteration mutants could be propagated in HeLa , A549 , and KB cells ; they were genetically stable; and they killed CREF cells at a strikingly high frequency.
 ( cell line: KB cells, None) , ( cell line: A549, None) , ( cell line: HeLa, None) , ( cell line: CREF 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:
 ( cell line: KB cells, None) , ( cell line: A549, None) , ( cell line: HeLa, None) , ( cell line: CREF cells, None) 