Reviewed by:

The phosphatase and tensin homolog gene (PTEN) on chromosome 10q23.3 is a nega-tive regulator of the PIK3/Akt survival pathway and is the most frequently deleted tumor suppressor gene in prostate cancer. Monoallelic loss of PTEN is present in up to 60 % of localized prostate cancers and complete loss of PTEN in prostate cancer is linked to metas-tasis and androgen-independent progression. Studies on the genomic status of PTEN in prostate cancer initially used a two-color fluorescence in situ hybridization (FISH) assay for PTEN copy number detection in formalin fixed paraffin embedded tissue preparations. More recently, a four-color FISH assay containing two additional control probes flanking the PTEN locus with a lower false-positive rate was reported. Combined with the detection of other critical genomic biomarkers for prostate cancer such as ERG, androgen receptor, and MYC, the evaluation of PTEN genomic status has proven to be invaluable for patient strat-ification and management. Although less frequent than allelic deletions, point mutations in the gene and epigenetic silencing are also known to contribute to loss of PTEN func-tion, and ultimately to prostate cancer initiation. Overall, it is clear that PTEN is a powerful biomarker for prostate cancer. Used as a companion diagnostic for emerging therapeutic drugs, FISH analysis of PTEN is promisingly moving human prostate cancer closer to more effective cancer management and therapies