PTEN and neoplasm: At least one copy of the Pten locus is lost in up to 65% of prostate tumors and complete loss of Pten protein is seen in ∼60% of late stage tumors (57–62) Loss of one copy of Pten greatly increases PCa progression in the TRAMP mouse model and Pten dosage has a marked impact on tumor latency and progression (63, 64).