7754
Although MKK3 , MKK4 , and MKK6 all activated p38 MAPk in experimental models , only MKK3 was found to activate recombinant p38 MAPk in LPS -treated neutrophils.
 MKK4, p38 MAPk, MKK3, MKK6, MKK3, p38 MAPk
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:
 MKK4, p38 MAPk, MKK3, MKK6, MKK3, p38 MAPk