1303
If, as the literature suggests, NK activity is relevant to breast cancer control , and since ER -tumors have a worse prognosis, we suggest here that perhaps such tumors are resistant to control by NK cells because they lack the ability to attract an accumulation of effector cells to the tumor site , or because blocking factors at the site of the tumor prevent local tumor control at the site of action.
 cell type: NK cells; cell type: effector cells; protein: ER
Please list all entity words in the text that fit the category.Output format is "type1: word1; type2: word2". 
Option: cell line, protein, RNA, DNA, cell type 
Text: {0} 
Answer:
 cell type: NK cells; cell type: effector cells; protein: ER