SMAD3 and medulloblastoma: While we found slightly increased Smad3 and Smad4 levels in Smo/Smo medulloblastoma as compared to cerebellum from wild-type mice (Fig. 5a), TGF-β treatment of DAOY cells did not result in reduced β1-subunit promoter activity despite increased levels of phosphorylated Smad3 indicating activation of the TGF-β signaling pathway in these cells (data not shown).