Overall , the expression of the Smad 2 and Smad 3 proteins was low in the glioma cell lines , the phosphorylation and nuclear translocation of Smad 2 and Smad 3 were impaired , and the TGFbeta receptor signal did not affect the expression of the SnoN , p 21 , p 15 , cyclin D 1 , and CDK 4 proteins . ^^^