In the light of the recent data in prostate cancer discussed above, it is possible that these two events (PTEN loss of function and impaired HR DNA repair) may not be causally linked in isolation; PTEN loss of function may be a bystander event in these HR defective OCCC cell lines, or a hitherto as yet undiscovered epistatic interaction may be required for PTEN loss of function to be mechanistically linked to impaired HR DNA repair. This evidence concerns the gene PTEN and Familial prostate cancer.