Hedgehog checkpoints in medulloblastoma: the chromosome 17p deletion paradigm.

Medulloblastomas often activate Hedgehog signaling inappropriately. The finding that mutations in components of this pathway are present only in few tumors suggests that additional genetic or epigenetic lesions can also lead to Hedgehog dysregulation. Chromosome 17p deletion, the most frequently detected genetic lesion in medulloblastoma, has recently been identified as a cause of unrestrained Hedgehog signaling. Such a deletion leads to the loss of REN(KCTD11), a novel Hedgehog antagonist, thus removing a checkpoint of Hedgehog-dependent events during cerebellum development and tumorigenesis. The disruption of additional Hedgehog modulators that map to 17p suggests a rationale for a multitargeted therapeutic strategy aimed at interrupting the cooperative activation of the Hedgehog pathway.