SMAD2 and neoplasm: There was no differences in the invasion rate between PC3 cells co-expressing cystatin C siRNA and Smad 2 siRNA and PC3 cells co-expressing cystatin C siRNA and control siRNA (Figure 6B–C), suggesting that inhibition of Smad2 had no additional effects on modulating invasion of PC3 cells expressing cystatin C siRNA and that Smad2 may be not involved in cystatin C-mediated tumor cell invasion.