6142
(2-Amino-3'-methoxyphenyl)oxanaphthalen-4-one ( PD 98059 ), an inhibitor of extracellular signal-regulated protein kinase ( ERK ) activation , blocked the serine phosphorylation of STAT3 induced by chemotactic factors or PMA .
 ( protein: STAT3, None) , ( protein: ERK, None) , ( protein: chemotactic factors, None) , ( protein: signal-regulated protein kinase, 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: STAT3, None) , ( protein: ERK, None) , ( protein: chemotactic factors, None) , ( protein: signal-regulated protein kinase, None) 