12226
However , the mechanisms of ATP - induced cPLA2 and COX - 2 expression and PGE2 synthesis remain largely unclear .
 Chemical: ATP; Chemical: PGE2
Given options, please tell me the categories of all the listed entity words.Output format is "type1: word1; type2: word2". 
Option: Chemical 
Text: {0} 
 Entities: ATP, PGE2 
Answer:
 Chemical: ATP; Chemical: PGE2