SMAD3 and glioblastoma: This result verifies that HOXA13, SMAD2/p-SMAD2 and SMAD3/p-SMAD3 primarily co-localize in the nucleus in GBM cells and that HOXA13 may stabilize phosphorylated R-SMAD by interacting with the MH2 domain in order to activate the TGF-β signaling pathway.