PTEN and glioblastoma: PTEN is a ubiquitously expressed tumour suppressor that shows complete loss of expression in some cancers (e.g. prostate cancer and glioblastoma) and over-representation of missense variants in others (e.g. endometrial cancer) (Alvarez-Garcia et al., 2019; Li et al., 1997; Steck et al., 1997; Yehia et al., 2020).