PTEN and cancer: In cancers with dysfunctional HR, such as those lacking BRCA1 [14], BRCA2 [14], PTEN [15] and RAD51D [16] function, PARP inhibitor-induced DSBs cannot be corrected by HR, and are repaired by error prone mechanisms (e.g. non-homologous end-joining), which result in high levels of genetic instability and eventually cell death.