1574
RNAase protection assays demonstrated that the MMP9 activity, unique to infected cells , is due to increased MMP9 mRNA levels .
 MMP9, MMP9, infected cells, RNAase
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:
 MMP9, MMP9, infected cells, RNAase