1677
Retinoids , including all-trans-retinoic acid , its isomers, and fifty synthetic retinoids (retinobenzoic acids), were tested for differentiation-inducing activity on human leukemia cell lines HL-60 and NB4 .
 NB4, HL-60, human leukemia cell lines
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, HL-60, human leukemia cell lines