SUMO1 and glioblastoma: Protein levels of SUMO1, SUMO2/3 and Ubc9 are upregulated in patient samples derived from astrocytic tumors, with a moderate upregulation in low-grade astrocytoma (grade 2) and anaplastic astrocytoma (grade 3), and a massive upregulation in glioblastoma multiforme (GBM; grade 4) [258].