3704
The NB4 cell line , which is derived from the bone marrow of a patient with APL during relapse, can be used as a model system to study the growth and differentiation of APL cells .
 APL cells, NB4 cell line
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:
 APL cells, NB4 cell line