title: Exosomal ITGA3 interferes with non-cancerous prostate cell functions and is increased in urine exosomes of metastatic prostate cancer patients.
abstract: BACKGROUND
  Cancer cells are able to change the protein expression and behavior of non-cancerous surrounding cells. Exosomes, secreted by prostate cancer (PCa) cells, may have a functional role in cancer metastasis and present a promising source for protein biomarkers. The aim of the present study was to identify which proteins in exosomes can influence non-cancerous cells, and to determine whether we can use urine exosomal proteins to identify high-risk PCa patients.
  
  
  METHODS
  Exosomes were isolated by ultracentrifugation. Migration and invasion were studied by the transwell (invasion) assay. Proteomics was performed by LC-MS/MS and identified proteins were validated by Western blotting. Cellular uptake of fluorescent labeled PKH67-exosomes was measured by FACS.
  
  
  RESULTS
  Based on comparative protein profiling by mass spectrometry-based proteomics of LNCaP- and PC3-exosomes, we selected ITGA3 and ITGB1, involved in migration/invasion, for further analyses. Inhibition of exosomal ITGA3 reduced the migration and invasion of non-cancerous prostate epithelial cells (prEC) almost completely. Cellular uptake of exosomes by prEC was higher with PC3-exosomes compared to LNCaP exosomes. Finally, ITGA3 and ITGB1 were more abundant in urine exosomes of metastatic patients (p<0.05), compared to benign prostate hyperplasia or PCa.
  
  
  CONCLUSIONS
  These data indicate exosomal ITGA3 and ITGB1 may play a role in manipulating non-cancerous surrounding cells and that measurement of ITGA3 and ITGB1 in urine exosomes has the potential to identify patients with metastatic PCa in a non-invasive manner.
authors.affiliation: Department of Urology, VU University Medical Center, Amsterdam, The Netherlands.
authors.forename: Irene V
authors.initials: IV
authors.lastname: Bijnsdorp
authors.affiliation: Department of Urology, VU University Medical Center, Amsterdam, The Netherlands.
authors.forename: Albert A
authors.initials: AA
authors.lastname: Geldof
authors.affiliation: OncoProteomics Laboratory, Department of Medical Oncology, VU University Medical Center, Amsterdam, The Netherlands.
authors.forename: Mehrdad
authors.initials: M
authors.lastname: Lavaei
authors.affiliation: OncoProteomics Laboratory, Department of Medical Oncology, VU University Medical Center, Amsterdam, The Netherlands.
authors.forename: Sander R
authors.initials: SR
authors.lastname: Piersma
authors.affiliation: Department of Urology, VU University Medical Center, Amsterdam, The Netherlands.
authors.forename: R Jeroen A
authors.initials: RJ
authors.lastname: van Moorselaar
authors.affiliation: OncoProteomics Laboratory, Department of Medical Oncology, VU University Medical Center, Amsterdam, The Netherlands.
authors.forename: Connie R
authors.initials: CR
authors.lastname: Jimenez
keywords: biomarker; integrin; non-cancerous cells; prostate cancer; proteomics