4371
Interferons as well as retinoids inhibit the growth of NB4 cells , although the 2 classes of compounds do not significantly interact in terms of anti-proliferative activity .
 NB4 cells, Interferons
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:
 NB4 cells, Interferons