1749
The activity of constructs containing 5' deletion mutants of the alpha 4 gene promoter was compared in transfection assays into cell lines that express alpha 4 and cell lines that do not.
 alpha 4, cell lines, cell lines, alpha 4 gene promoter, 5' deletion mutants, alpha 4
Please list all entity words in the text that fit the category. Output format is "word1, word2". 
Option: cell line, protein, RNA, DNA, cell type 
Text: {0} 
Answer:
 alpha 4, cell lines, cell lines, alpha 4 gene promoter, 5' deletion mutants, alpha 4