PTEN and breast cancer: Thus, the dcas9-VRP system achieved unprecedented reactivation of tumor suppressor genes [84].Although dcas9/VPR can activate PTEN transcription in some tumors that cause AKT and mTOR pathway suppression [85], the use of the CRIPR/dCAS9 system to activate PTEN has been particularly effective in the melanoma cell line SK-MEL-28 and the breast cancer cell line SUM159,where PTEN levels have been elevated and tumorigenic pathways such as the PI3K/AKT/mTOR pathway have been inhibited [85].