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One of the prominent substrates for these kinases is the adaptor protein Cbl [3] and recent studies suggest that Cbl negatively regulates upstream kinases such as Syk and Zap-70 [4] [5].
 adaptor protein, kinases, upstream kinases, Zap-70, Syk, Cbl
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:
 adaptor protein, kinases, upstream kinases, Zap-70, Syk, Cbl