RB1 and glioblastoma: Sun et al. 43 proposed that males are at higher risk of developing GBM due to an intrinsic sexual dimorphism in astrocyte transformation, as male GBM astrocytes exhibit higher proliferation rates, greater inactivation of the retinoblastoma tumour suppressor protein (RB), as well as increased tumourigenesis in vivo than female GBM astrocytes.