Molecular basis of the nevoid basal cell carcinoma syndrome

Many genes originally identified because of their role in embryonic development are also important in control of cell growth and differentiation postnatally. Mutations in some of these genes have been shown to contribute to carcinogenesis. The nevoid basal cell carcinoma syndrome is an autosomal dominant disorder that predisposes to basal cell carcinomas of the skin as well as widespread developmental defects. The gene for this disorder, NBCCS, maps to chromosome 9q22.3, and loss of heterozygosity at this site in both sporadic and hereditary basal cell carcinomas suggests that it functions as a tumor suppressor. NBCCS was positionally cloned and shown to be the human homologue of the Drosophila gene, patched. Drosophila patched is part of the hedgehog signaling pathway, important in determining embryonic patterning and cell fate in multiple structures of the developing embryo. That mutations in human patched result in dysregulation of several genes known to play a role in both organogenesis and carcinogenesis may explain both the birth defects and the cancer predisposition seen in the nevoid basal cell carcinoma syndrome.