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The reasons for the dissimilar oncogenicities of human adenoviruses and human papillomaviruses ( HPV ) in humans are unknown but may relate to differences in the capacities of the E1A and E7 proteins to target cells for rejection by the host natural killer (NK) cell response .
 cell type: host natural killer (NK) cell; protein: E7 proteins; cell type: target cells; protein: E1A
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: host natural killer (NK) cell; protein: E7 proteins; cell type: target cells; protein: E1A