PTEN and cancer: In this study, using cancer cell line models and a preclinical genetic mouse model of endometrioid endometrial cancer, we show that PTEN-deficient endometrioid endometrial cancer cells are not responsive to the single treatment with PARP inhibitor Olaparib, but combined inhibition of PARP and PI3K results in a synergistic growth inhibitory effect in vitro as well as a cooperative antitumor effect in vivo.