PTEN and glioblastoma: On the other hand, GBMs that present PTEN deletion, considered to be a bad prognosis marker13,15–17, have higher PDGF family expression levels than the tumours with PTEN gain, which correlates with a better prognosis (Fig. 5a); analysis of each PDGF subunit separately reveals that PDGFA is differentially expressed between these two types of GBM (Fig. 5b).