PTEN and central nervous system cancer: Suppressor cells (MDSCs), of myeloid derivation, are immunogenically immature cells; their differentiation and activity are inhibited by glioma cells that deliver to them, via EVs, a series of microRNAs, such as miRNA-10 (which acts via the RAR Related Orphan Receptor A, Rora), miRNA-21 (which acts via the phosphatase and tensin homolog, PTEN, oncosuppressor pathway), miRNA-29 (which acts via the HMG-Box transcription factor 1, Hbp1), and miRNA92 (which influences the pathway involving the protein kinase A regulatory subunit I alpha, PRKAR1A, pathway) [131].