title: Intensified autophagy compromises the efficacy of radiotherapy against prostate cancer.
abstract: BACKGROUND
  Radiotherapy is an equivalent alternative or complement to radical prostatectomy, with high therapeutic efficacy. High risk patients, however, experience high relapse rates, so that research on radio-sensitization is the most evident route to improve curability of this common disease.
  
  
  METHODS
  In the current study we investigated the autophagic activity in a series of patients with localized prostate tumors treated with radical radiotherapy, using the LC3A and the LAMP2a proteins as markers of autophagosome and lysosome cellular content, respectively. The role of autophagy on prostate cancer cell line resistance to radiation was also examined.
  
  
  RESULTS
  Using confocal microscopy on tissue biopsies, we showed that prostate cancer cells have, overall, high levels of LC3A and low levels of LAMP2a compared to normal prostate glands. Tumors with a 'highLC3A/lowLAMP2a' phenotype, suggestive of intensified lysosomal consumption, had a significantly poorer biochemical relapse free survival. The PC3 radioresistant cell line sustained remarkably its autophagic flux ability after radiation, while the DU145 radiosensitive one experiences a prolonged blockage of the autophagic process. This was assessed with aggresome accumulation detection and LC3A/LAMP2a double immunofluorescence, as well as with sequestrosome/p62 protein detection. By silencing the LC3A or LAMP2a expression, both cell lines became more sensitive to escalated doses of radiation.
  
  
  CONCLUSIONS
  High base line autophagy activity and cell ability to sustain functional autophagy define resistance of prostate cancer cells to radiotherapy. This can be reversed by blocking up-regulated components of the autophagy pathway, which may prove of importance in the field of clinical radiotherapy.
authors.affiliation: Department of Radiotherapy/Oncology, Democritus University of Thrace, Alexandroupolis, 68100, Greece. Electronic address: targ@her.forthnet.gr.
authors.forename: Michael I
authors.initials: MI
authors.lastname: Koukourakis
authors.affiliation: Department of Radiotherapy/Oncology, Democritus University of Thrace, Alexandroupolis, 68100, Greece.
authors.forename: Dimitra
authors.initials: D
authors.lastname: Kalamida
authors.affiliation: Department of Radiotherapy/Oncology, Democritus University of Thrace, Alexandroupolis, 68100, Greece.
authors.forename: Achilleas
authors.initials: A
authors.lastname: Mitrakas
authors.affiliation: Department of Radiotherapy/Oncology, Democritus University of Thrace, Alexandroupolis, 68100, Greece.
authors.forename: Stamatia
authors.initials: S
authors.lastname: Pouliliou
authors.affiliation: Department of Radiotherapy/Oncology, Democritus University of Thrace, Alexandroupolis, 68100, Greece.
authors.forename: Sofia
authors.initials: S
authors.lastname: Kalamida
authors.affiliation: Department of Pathology, Democritus University of Thrace, Alexandroupolis, 68100, Greece.
authors.forename: Efthimios
authors.initials: E
authors.lastname: Sivridis
authors.affiliation: Department of Pathology, Democritus University of Thrace, Alexandroupolis, 68100, Greece.
authors.forename: Alexandra
authors.initials: A
authors.lastname: Giatromanolaki
mesh_terms: D000368:Aged; D001343:Autophagy; D045744:Cell Line, Tumor; D006801:Humans; D052119:Lysosomal-Associated Membrane Protein 2 / Q000032:analysis; D008297:Male; D008869:Microtubule-Associated Proteins / Q000032:analysis; D008875:Middle Aged; D009364:Neoplasm Recurrence, Local / Q000473:pathology; D011467:Prostate / Q000473:pathology* / Q000528:radiation effects*; D011471:Prostatic Neoplasms / Q000473:pathology / Q000532:radiotherapy*
chemical_list: C497811:LAMP2 protein, human; D052119:Lysosomal-Associated Membrane Protein 2; C477012:MAP1LC3A protein, human; D008869:Microtubule-Associated Proteins
keywords: Aggresomes; Autophagy; LAMP2a; LC3A; Prostate cancer; Radiotherapy