1700
As one test of this hypothesis, we compared the abilities of E1A -and E7 -expressing human fibroblastic or keratinocyte-derived human cells to be selectively killed by either unstimulated or interferon (IFN)-activated NK cells .
 protein: E1A; cell line: interferon (IFN)-activated NK cells; protein: E7; cell type: unstimulated
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:
 protein: E1A; cell line: interferon (IFN)-activated NK cells; protein: E7; cell type: unstimulated