PKHD1 and glioblastoma: However, Draaisma et al. demonstrated that mutations in the PKHD1 gene is associated with poor prognosis in glioma patients [35], while studies have shown that mutations in the CDKN2A gene results in a loss of expression in the p16 protein, an inhibitor of cell cycle progression, and is associated with a significantly shorter survival in GBM patients [36,37,38].