3317
In the erythroleukemia cell line K562 , due to the absence of Spi-B , only PU.1 bound to the Btk promoter .
 Btk, PU.1, Spi-B, Btk promoter, erythroleukemia cell line K562
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:
 Btk, PU.1, Spi-B, Btk promoter, erythroleukemia cell line K562