PTCH1 and medulloblastoma: To determine whether Ahr has a role in SHH medulloblastoma, we deleted Ahr in these cells together with Ptch1. As previously reported35, 100% of Math1cre; Ptch1f/f (Ptch1 cKO) animals succumbed to medulloblastoma within 3 months of age, with a median survival of 63.5 days (Fig. 3a).