+------SUBJ:V-N------+-COMP:V-N(in)+    
      +COMP:N-N(of)+       |        +MOD_+    
      |            |       |        |    |    
 Expression of __NODE__ occurs in U937 cells .
COMP:N-N(of) (expression,__NODE__)
SUBJ:V-N (occur,expression)
COMP:V-N(in) (occur,cell)
MOD_ATT:N-N (cell,U937)