gms | German Medical Science

Medulloblastoma represents the most frequent malignant brain tumor of childhood. Its capacity to invade surrounding structures, especially brainstem is one of the most important limiting factors for survival. Experimentally, xenotransplanted cells gave rise to subcutaneous growth of tumors in some but not all medulloblastoma cell-lines. On specific extracellular matrix-proteins, medulloblastomas show few invasive characteristics compared to adult glioma invasion assays. The goal of our study was to evaluate the widely varying medulloblastoma invasion in cerebellar tissue in a new assay system in vitro.

As a matrix for invasion we used freshly prepared cerebellar parenchyma. Cut in 40µm – slices, it was fixed to a membrane only by mechanical manners, maintaining its structure without any chemical treatment for preservation. Spheroids of two established human medulloblastoma cell lines (MHH-Med 4, MEB-Med 8S), whose invasive potential in other assay systems is poor, were studied for their invasiveness into the brain-slice within 24 hours, as well as the optimal conditions for preservation of the slice. Vincristin, which blocks glioma cell motility, was used for negative controls.

Without any addition of chemoattractants to cause directional locomotion into the brain-slice, the medulloblastoma cells showed a strong adhesion to the cerebellar slice, as well as rapid, cluster-shaped invasion. Medulloblastoma cell invasion was inhibited in a dose dependent fashion by Vincristin, which validates this system for functional experiments. The invasive capacities of both cell-lines differed widely.

The newly developed invasion assay system provides reproducible means to investigate the varying invasive behavior of medulloblastomas. This is the first description of a medulloblastoma-specific in vitro invasion assay.