9001
Serine phosphorylation of STAT1 and STAT3 was seen occasionally in other leukemias , but it was a universal finding only in CLL .
 STAT3, STAT1
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:
 STAT3, STAT1