SMO and neoplasm: Analysis of human cancer tissue and mouse models of Hh pathway activation have revealed that inactivating mutations, including deletions, mRNA splice-site and nonsense mutations in PTCH1 [66], SUFU [67,68,69] or activating missense mutations in SMO, SmoM2 (Trp535Leu) [70,71], or gene amplifications and translocations of GLI1 or GLI2 [72], usually in combination with the inactivation of additional tumour suppressor genes [73], are sufficient to form a variety of sporadic tumours [74].