11320
Given the important role of the estrogen receptor ( ER ) in the development and physiology of the breast , it is essential to delineate the mechanisms responsible for its failed expression in some breast tumors .
 protein: estrogen receptor; protein: ER
Given options, please tell me the categories of all the listed entity words.Output format is "type1: word1; type2: word2". 
Option: cell line, protein, RNA, DNA, cell type 
Text: {0} 
 Entities: estrogen receptor, ER 
Answer:
 protein: estrogen receptor; protein: ER