NOTCH1 and medulloblastoma: Upon orthotopic transplantation, NOTCH1+ cells robustly generate cerebellar tumors and give rise to spontaneous spinal metastases upon primary and secondary transplantation, in contrast to NOTCH1− medulloblastoma cells, which are unable to produce metastases in the primary transplant and do not generate cerebellar tumors in the secondary re-transplant experiments.