To identify the E3 ligases involved in the proteasome-mediated degradation of RPN2, we performed co-IP experiments and mass spectrometry analysis and found that CUL2, a protective factor for GBM prognosis 28, that forms cullin-RING complexes to promote substrate ubiquitination and degradation 29, can bind to RPN2 (Figure 5I and Table S5). This evidence concerns the gene CACUL1 and glioblastoma.