Murine model of leptomeningeal dissemination using human medulloblastoma cells.

An experimental model of meningeal dissemination was developed by intracisternal inoculation of human medulloblastoma (ONS-76) cells into nude mice. All mice died within 65 days after inoculation of 1 x 10(7) tumor cells. The median survival time was 56 days. Clinical signs and histological findings were similar to those in medulloblastoma patients with meningeal dissemination. Immunohistochemical studies showed that ONS-76 cells in the subarachnoid space expressed major histocompatibility complex (MHC) class I antigens until 20 days after inoculation. After 30 days, expression of MHC class I antigens decreased and cells began to proliferate rapidly. Expression of MHC class I antigens on tumor cells may result in effective recognition by the host immune system.