EN incorporation into the exosomes. We treated the cells with the EGFR inhibitor CI-1033. Inhibiting EGFR decreased the incorporation of PTEN into MedChemExpress Butein exosomes in a concentration dependent 2199952 manner. PTEN Transferred through Exosomes Affects Biological Functions in the Acceptor Cells To assess whether the biochemical changes observed in PTEN Status in PC Patients can be Assessed Using Blood Exosomes To study the role of exosomes in the assessment of PTEN status in PC patients, we collected blood from 30 PC patients prior to prostatectomy, and 8 normal subjects matching the age of the patients. The normal volunteers had no history of cancer or previously documented elevated serum PSA. The blood was fractionated, and the plasma 
was used as a source for exosomes. PTEN-exosomes were immunoprecipitated using PTEN antibodies and Sepharose protein-G. The incorporation of PTEN into exosomes from PC patients’ blood was determined by immunoblotting, and different levels of expression were detected among patients. Interestingly, we found PTEN expression in exosomes from all PC patients, and no PTEN expression in the exosomes from the blood of the normal subjects; ttest analysis showed the results were highly significant P,0.001. In addition, we could assess the concentration of PTEN in PC patients’ exosomes by immunoblotting with standard concentra- Incorporation of PTEN into Exosomes is Regulated by Oncogenes To investigate the mechanism of incorporation of PTEN into exosomal cargo, we tested the role of the oncogenic receptor 10 Exosomal-PTEN in Prostate Cancer tions of recombinant PTEN, and the concentration of PTEN was determined as . Blood exosomal-PTEN Provides a Simple Tool to Assess PTEN Status PC tumors are heterogeneous in PTEN expression as seen in. PTEN status in the tumors of four PC patients was determined by immunohistochemistry. The figure demonstrates the difficulty of forming a conclusion about PTEN expression using this technique. PTEN expression in the blood exosomes of the same patients is assessed in Expression of PSA in Exosome Preparations from PC Patients and Normal Subjects Using 30 PC patients and 8 normal subjects, we detected PSA in exosomes from both PC patients and normal subjects: optical densities of the PSA bands were used for statistical analysis. The differences in exosomal PSA between PC patients and normal subjects were not significant. Detection of PSA in exosomes from normal subjects and PC patients points to a new fraction of PSA, which may be related to the lack of specificity associated with the PSA test. We assessed PSA status because it is the traditional biomarker used in PC diagnosis. We wanted to determine whether PSA is expressed on patients’ blood exosomes, and assess the differences in expression between PC patients and normal subjects. This allowed us to 3630970 compare the expression pattern of PSA and exosomal-PTEN in PC patients and normal subjects. We performed this comparison to assess the specificity of exosomal-PTEN compared to PSA, the traditional prostate cancer biomarker. Discussion An important observation made during the present study is that PTEN is expressed in exosomes derived from cancer cells, and it is not detected in exosomes from normal cells, although the normal cells themselves express PTEN. Thus, the incorporation of PTEN in exosomes may represent a characteristic of cancer cells not found in normal cells. This finding may suggest an exclusionary mechanism used by cancer cells to downregu
