The oncogenic function of HH was initially suggested by the observation that loss of heterozygosity (LOH) and germline inactivating mutations in PTCH1 are associated with the Gorlin syndrome, a hereditary disorder that predisposes patients to basal cell carcinomas (BCCs), medulloblastomas, and rhabdomyosarcomas (Hahn et al., 1996; Johnson et al., 1996). Here, PTCH1 is linked to medulloblastoma.