7821
Comparison of tumor specimen from MM precursor lesions , primary tumors , and metastases revealed that CD40 surface expression is down-regulated during tumor progression .
 ( protein: CD40, None) 
Locate the role in the text that participated in the event based on the event type and return it in the event list. 
 Option: Event type: RNA,cell type,protein,cell line,DNA, Arguments type: . 
Text: {0} 
Answer:
 ( protein: CD40, None) 