By immunohistochemical analysis we observed that all the mice studied developed tumors, but brains xenografted with both GBM1- and GBM2-Scr cells showed the presence of large tumor masses, with a diffuse tumor invasion of the brain parenchyma (Figure 10A, 10B), while the injection of GBM1- and GBM2-PrP-KO cells, analyzed at the same time after the injection, caused the formation of very small tumors. Here, PRNP is linked to neoplasm.