6648
N-formyl-methionyl-leucyl-phenylalanine ( FMLP ) and phorbol myristate acetate ( PMA ) induced tyrosine phosphorylation of 42- and 44- kDa proteins , which were identified as extracellular signal-regulated kinase ( ERK ), in human monocytes .
 ERK, human monocytes, extracellular signal-regulated kinase
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:
 ERK, human monocytes, extracellular signal-regulated kinase