7475
Treatment with E2 was also associated with a time-dependent decrease in the mRNA level of the proapoptotic Nip-2 protein , supporting the hypothesis that hormone responsiveness of U937 cells is mediated by target gene transcription.
 U937 cells, proapoptotic Nip-2 protein
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:
 U937 cells, proapoptotic Nip-2 protein