PTEN and neoplasm: The mechanism of plasticity is postulated to be produced by astrocyte-dependent, epigenetically regulated protein downregulation, where astrocyte-derived exosomes arbitrate an intercellular exchange of PTEN-targeting microRNAs to metastatic tumor cells, while depletion of these microRNAS or blockade of astrocyte exosome secretion effectively “rescues” PTEN expression and suppresses brain metastasis [62].