Although PTEN is a phosphatase widely known for its role as a tumor suppressor, nuclear PTEN is essential for maintaining genome stability by dephosphorylating MCM2, and modulating replication fork progression under conditions of DNA replication stress [48], suggesting that the loss of 45S rDNA repeats observed in the Pten-/- mouse HSCs could be attributed to DNA replication stress. This evidence concerns the gene MCM2 and neoplasm.