13972
Here , we demonstrated that in rat embryonic - heart derived H9c2 cells , TNF - alpha could induce MMP - 9 mRNA expression associated with an increase in the secretion of MMP - 9 , determined by real - time PCR , zymography , and promoter activity assays .
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Please list all entity words in the text that fit the category. Output format is "word1, word2". 
Option: Chemical 
Text: {0} 
Answer:
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