PTEN and Familial prostate cancer: Loss of PTEN induces cellular senescence as a failsafe mechanism to defend against tumorigenesis.43 In prostate cancer, PTEN loss has been shown to activate p53-dependent cell senescence by mTOR kinase binding to p53.43,44 Concomitant loss of p53 allows cells to override the cytostatic effects of PTEN-induced senescence.