The use of genome editing technology to directly reactivate PTEN is a relatively new approach being investigated to treat PTEN-deficient cancer that is not caused by a genetic alteration in PTEN, although this approach may only be applicable for up to 10% of PTEN-deficient prostate cancers in which PTEN transcription is suppressed by negative transcriptional regulators of PTEN or via promoter methylation [2]. The gene discussed is PTEN; the disease is cancer.