6622
Knockdown of estrogen receptor ( ER ) alpha and ER beta down - regulated E2 - induced SR - B1 expression .
 Chemical: estrogen
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: estrogen 
Answer:
 Chemical: estrogen