2671
Studies on RA time-response or pulse treatment in semisolid or liquid culture show that early RA addition is most effective, thus indicating that early but not late HPC are sensitive to its action.
 ( cell type: HPC, 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 type: HPC, None) 