SHH and pituitary tumor: Since GLI1/GLI1 expression was found in almost all human pituitary tumors studied, whereas SHH mRNA was present in few tumors samples (246) (see also (14)), the authors hypothesized that GLI1 expression in pituitary tumors is stimulated in a ligand-independent way and plays an important role in tumorigenesis, while the reduction in SHH expression is likely a compensatory mechanism.