BMI1 and astrocytoma (excluding glioblastoma): For instance, in gliomas, Bmi-1 expression is prognostic in oligodendroglial tumours, in which its expression is abundant, whereas in the much more aggressive high-grade astrocytomas and glioblastomas, Bmi-1 expression is frequently very low and does not correlate with prognosis (Häyry et al, 2008).