Medulloblastoma is a very aggressive childhood cerebellum cancer and the most common brain tumor in children. One of the major causes of medulloblastoma is aberrant activation of the Sonic hedgehog (Shh) signaling pathway. Our lab recently identified a novel marker which is a target of the Shh signaling pathway and which is expressed by medulloblastoma tumors. We aim to test whether this marker can be used to detect medulloblastoma at early (pre-malignant) stages and to monitor the transition of tumors from pre-malignant to malignant. Furthermore, we will also test whether this marker can be used to identify patients with tumors that result from Shh pathway misregulation, thus informing us of which patients will respond to drugs that specifically target Shh signaling. Developing a marker for medulloblastoma will facilitate the detection and improve the treatment of medulloblastoma and possibly other cancers that result from aberrant Shh signaling.