e. U87 cells, which do not express PTEN as they have mutations in both PTEN alleles, acquired PTEN expression. doi:10.1371/journal.pone.0070047.g002 a control to show the ability of exosomes to compensate for PTEN downregulation in DU145Kd. This procedure was used for U87 and PC-3 cells. Prostate Cancer Patients and Normal Subjects This study is supported by ethical approval from the McMaster University ethical board. The participants were informed about the purpose of the study, and written consent has 5 Exosomal-PTEN in Prostate Cancer 6 Exosomal-PTEN in Prostate Cancer after surgery and snap frozen in liquid nitrogen. Clinical records such as Gleason score, PSA, tumor size, tumor histopathological grade and metastasis were collected. Samples were collected according to the McMaster University ethical standards, and 11182320 patient consent was obtained before sampling. Eight healthy volunteer men aged 5065 were used in this study; all were without any history of cancer and with normal PSA levels. Statistical Analysis All experiments were reproduced at least three times with similar results. The quantitative data are 
presented as the average value of the replicates within the representative experiment 6 SEM. Statistical significance was evaluated using a computerized 2-tailed Student’s t-test. The differences were considered significant at P,0.05. Results PTEN is Expressed in Exosomes from PC Cells, but not Normal Cells We determined the status of PTEN in the following PC cells: DU145, DU145 stably transfected with PTEN siRNA for PTEN downregulation or knockdown, and DU145 transfected with control siRNA. Exosomes were collected from the conditioned media of each cell type, and equal protein concentrations from the cells and the exosomes were subjected to SDSPAGE and immunoblotting, then probed with PTEN antibodies. Both DU145Kd cells and exosomes showed a downregulation of PTEN expression compared to the wild type DU145 cells and DU145 cells transfected May 2026