title: The Role of HMGB1 in Radioresistance of Bladder Cancer.
abstract: Although radical cystectomy surgery is the standard-of-care for muscle-invasive bladder cancer, it entails complete removal of the bladder and surrounding organs which leads to substantial loss in the quality-of-life of patients. Radiotherapy, which spares the bladder, would be a more appropriate treatment modality if we can utilize molecular markers to select patients with better response to radiation. In this study, we investigate a protein called high mobility group box protein 1 (HMGB1) as a predictive marker for radiotherapy response in bladder cancer. Our in vitro results indicate a positive correlation between higher levels of HMGB1 protein and resistance to radiation in various cell lines. Upon HMGB1 protein knockdown, highly significant (>1.5-fold) sensitization to radiotherapy was achieved. We saw that loss of HMGB1 was associated with at least two times higher (P < 0.001) DNA damage in cell lines postradiation. Our results also depicted that autophagy was inhibited more than 3-fold (P < 0.001) upon HMGB1 knockdown, implicating its role in autophagy as another cause of bladder cancer radioresistance. Further validation was done in vivo by conducting mouse tumor xenograft experiments, where HMGB1 knockdown tumors showed a significantly better (P < 0.001) response to radiotherapy and decreased autophagy (shown by P62 staining) as compared with controls. The cumulative findings of our in vitro and in vivo studies highlight the significance of HMGB1 as a radiation response marker as well as its utility in radiosensitization of bladder cancer.
authors.affiliation: Urologic Oncology Research Division, McGill University, Montréal, Quebec, Canada.
authors.forename: Sanhita
authors.initials: S
authors.lastname: Shrivastava
authors.affiliation: Urologic Oncology Research Division, McGill University, Montréal, Quebec, Canada.
authors.forename: Jose Joao
authors.initials: JJ
authors.lastname: Mansure
authors.affiliation: Urologic Oncology Research Division, McGill University, Montréal, Quebec, Canada.
authors.forename: Wael
authors.initials: W
authors.lastname: Almajed
authors.affiliation: Department of Radiation Oncology, McGill University Health Center, Montréal, Quebec, Canada.
authors.forename: Fabio
authors.initials: F
authors.lastname: Cury
authors.affiliation: Department of Biochemistry, University of Montreal, Montréal, Quebec, Canada.
authors.forename: Gerardo
authors.initials: G
authors.lastname: Ferbeyre
authors.affiliation: Department of Medical Physics, McGill University Health Center, Montréal, Quebec, Canada.
authors.forename: Marija
authors.initials: M
authors.lastname: Popovic
authors.affiliation: Department of Medical Physics, McGill University Health Center, Montréal, Quebec, Canada.
authors.forename: Jan
authors.initials: J
authors.lastname: Seuntjens
authors.affiliation: Urologic Oncology Research Division, McGill University, Montréal, Quebec, Canada. wassim.kassouf@muhc.mcgill.ca.
authors.forename: Wassim
authors.initials: W
authors.lastname: Kassouf
mesh_terms: D000818:Animals; D001343:Autophagy / Q000235:genetics / Q000528:radiation effects; D045744:Cell Line, Tumor; D004249:DNA Damage / Q000528:radiation effects; D004195:Disease Models, Animal; D005260:Female; D015870:Gene Expression; D055785:Gene Knockdown Techniques; D024243:HMGB1 Protein / Q000235:genetics / Q000378:metabolism*; D006801:Humans; D007150:Immunohistochemistry; D051379:Mice; D034622:RNA Interference; D034741:RNA, Small Interfering / Q000235:genetics; D011836:Radiation Tolerance / Q000235:genetics; D047368:Tumor Burden / Q000235:genetics / Q000528:radiation effects; D001749:Urinary Bladder Neoplasms / Q000235:genetics / Q000378:metabolism* / Q000473:pathology / Q000532:radiotherapy; D023041:Xenograft Model Antitumor Assays
chemical_list: D024243:HMGB1 Protein; D034741:RNA, Small Interfering