Heparanase, TrkC and p75^NTR: Their functional involvement in human medulloblastoma cell invasion

Medulloblastoma is the most common malignant childhood brain tumor. Although some previous reports have shown up to a 70% 5-year survival for some of these patients, it is at the cost of significant long-term treatment-related morbidity. The cellular mechanisms leading to metastatic disease in medulloblastoma are mainly unknown. For the first time, we demonstrate the differential expression of heparanase in medulloblastomas and how these differences at the mRNA and protein levels affect the activity and invasive properties of three newly developed cell lines. Furthermore, heparanase expression was confirmed in 7 (88%) of 8 medulloblastoma clinical samples by immunohistochemical staining. Heparanase was found to be localized in the cytoplasm and nucleus. Quantitative polymerase chain reaction revealed a negative correlation between heparanase and TrkC (which is associated with a favorable clinical outcome). The activation of TrkC or TrkC/p75^NTR by NT-3 affected heparanase activity and cell-invasive properties of medulloblastoma cells in vitro. Taken together, our data extend the body of evidence that invasion and expression/functionality of heparanase, in a context linked to TrkC and p75^NTR, may play critical roles in the disease progression of medulloblastoma.