1629
The cancer cell lines MDA - MB - 231 ( ER - ) , MCF - 7 ( ER + + + + ) and BT - 474 ( ER + + ) were used to explore the mechanisms regulating cell proliferation .
 None
Please list all entity words in the text that fit the category.Output format is "type1: word1; type2: word2". 
Option: Chemical 
Text: {0} 
Answer:
 None