PTEN and prostate cancer: Growth factor-independent activation of mTORC1 also occurs upon loss of the PTEN tumor suppressor, and rapamycin was found to decrease ATF4 protein levels and ATF4-dependent expression of representative gene targets in established PTEN-deficient prostate cancer cells, LNCaP and PC3 (Figure 3I–L, Figure 3—figure supplement 1G–J).