This study did not assess the effects of TGFβ-SMAD pathway modulation on apoptosis, however a significant decrease in Ahr cKO CPC number observed with SB43 and SIS3 treatment suggests that enhanced CPC survival may be an important mechanism of increased tumorigenicity in Ahr-deficient SHH medulloblastoma. This evidence concerns the gene TGFB1 and medulloblastoma.