title: Blocked autophagy using lysosomotropic agents sensitizes resistant prostate tumor cells to the novel Akt inhibitor AZD5363.
abstract: OBJECTIVE
  Prostate cancer development is often associated with deletion or silencing of tumor suppressor phosphatase and tensin homolog (PTEN), a negative regulator of the phosphoinositide 3 kinase (PI3K)-Akt pathway, leading to resistance to various therapies in both the preclinical and clinical setting. Therefore, the PI3K-Akt pathway plays a central role in various cellular processes promoting survival signaling that can contribute to the malignant phenotype, and, consequently, is an attractive pharmacologic target. However, as single agents, the efficacy of AKT inhibitors may be limited by resistance mechanisms that result in minimal cell death in tumor cells.
  
  
  METHODS
  We investigated the effects of the Akt inhibitor AZD5363 on cell proliferation, cell cycle, apoptosis, and Akt downstream pathway proteins. Survival mechanisms induced by AZD5363 were investigated. We then examined the impacts of inhibition of autophagy in combination with AZD5363 on cell proliferation and apoptosis. Furthermore, the anticancer activity of combination treatment of the lysosomotropic inhibitor of autophagy (chloroquine) with the Akt inhibitor AZD5363 was evaluated in PC-3 prostate cancer xenografts.
  
  
  RESULTS
  Here, we show that the Akt inhibitor AZD5363 affected the Akt downstream pathway by reducing p-mTOR, p-P70S6K, and p-S6K. While AZD5363 monotherapy induced G(2) growth arrest and autophagy, it failed to induce significant apoptosis in PC-3 and DU145 prostate cancer cell lines. Blocking autophagy using pharmacologic inhibitors (3-methyladenine, chloroquine, and bafilomycin A) or genetic inhibitors (siRNA targeting Atg3 and Atg7) enhanced cell death induced by Akt inhibitor AZD5363 in these tumor prostate cell lines. Importantly, the combination of AZD5363 with chloroquine significantly reduced tumor volume by 84.9% compared with the control group and by 77.5% compared with either drug alone in PC3 xenografts.
  
  
  CONCLUSIONS
  Taken together, these data show that the Akt inhibitor AZD5363 synergizes with the lysosomotropic inhibitor of autophagy chloroquine to induce apoptosis and delay tumor progression in prostate cancer models that are resistant to monotherapy AZD5363, providing a new therapeutic approach potentially translatable to patients.
authors.affiliation: The Vancouver Prostate Centre, University of British Columbia, Vancouver, British Columbia, Canada.
authors.forename: Francois
authors.initials: F
authors.lastname: Lamoureux
authors.forename: Christian
authors.initials: C
authors.lastname: Thomas
authors.forename: Claire
authors.initials: C
authors.lastname: Crafter
authors.forename: Masafumi
authors.initials: M
authors.lastname: Kumano
authors.forename: Fan
authors.initials: F
authors.lastname: Zhang
authors.forename: Barry R
authors.initials: BR
authors.lastname: Davies
authors.forename: Martin E
authors.initials: ME
authors.lastname: Gleave
authors.forename: Amina
authors.initials: A
authors.lastname: Zoubeidi
mesh_terms: D001343:Autophagy / Q000187:drug effects / Q000235:genetics*; D002453:Cell Cycle / Q000187:drug effects; D045744:Cell Line, Tumor; D049109:Cell Proliferation / Q000187:drug effects; D002738:Chloroquine / Q000008:administration & dosage; D019008:Drug Resistance, Neoplasm / Q000235:genetics; D004357:Drug Synergism; D006801:Humans; D008247:Lysosomes / Q000187:drug effects / Q000378:metabolism* / Q000473:pathology; D008297:Male; D051058:Oncogene Protein v-akt / Q000037:antagonists & inhibitors / Q000378:metabolism*; D051059:PTEN Phosphohydrolase / Q000235:genetics / Q000378:metabolism; D011471:Prostatic Neoplasms / Q000188:drug therapy* / Q000378:metabolism / Q000473:pathology; D011743:Pyrimidines / Q000008:administration & dosage*; D011758:Pyrroles / Q000008:administration & dosage*; D015398:Signal Transduction
chemical_list: D011743:Pyrimidines; D011758:Pyrroles; D002738:Chloroquine; D051058:Oncogene Protein v-akt; D051059:PTEN Phosphohydrolase; C494929:PTEN protein, human; C575618:capivasertib