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These results provide evidence that promonocytic THP-1 cells require prestimulation in order to activate HUVEC and that TNF alpha contributes to this phenomenon.
 promonocytic THP-1 cells, TNF alpha, HUVEC
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:
 promonocytic THP-1 cells, TNF alpha, HUVEC