title: Synergistic anticancer efficacy of MEK inhibition and dual PI3K/mTOR inhibition in castration-resistant prostate cancer.
abstract: BACKGROUND
  PTEN deletion, mutation or reduced expression occurs in 63% of metastatic prostate tumors, resulting in the activation of PI3K and its downstream targets, AKT and mTOR. Inhibition of the PI3K pathway results in upregulation of the MAPK pathway. Therefore, co-administration of inhibitors of both pathways, GSK2126458 as a dual PI3K/mTOR inhibitor, and AZD6244 as a MEK inhibitor, is able to overcome resistance and increase anti-tumor efficacy.
  
  
  METHODS
  PC3, DU145, LNCaP, and CRPC patient-derived cells were used to assess apoptosis upon exposure to the drug combination. The human DU145 and PC3 tumor xenograft mouse model was employed to evaluate in vivo efficacy. CellTiter Glo® luminescent assay, annexin V-FITC apoptosis detection, cell cycle analysis, Western blotting and immunohistochemistry were conducted. Statistical evaluation of the results was performed by one-way ANOVA.
  
  
  RESULTS
  The combination of GSK2126458 and AZD6244 inhibited the growth of DU145 and PC3 prostate cancer cells in vitro and in vivo. GSK2126458 decreased phospho-AKT while increasing phospho-ERK and AZD6244 decreased phospho-ERK efficiently while increasing phospho-AKT. The combination of GSK2126458 and AZD6244 decreased both phospho-AKT and phospho-ERK effectively in vitro and in vivo. The combination treatment synergistically induced annexin V-positive cells, sub-G1 cells, and cleavage of caspase-9, caspase-3 and poly-ADP ribose polymerase (PARP) in DU145 cells in vitro. Moreover, the combination decreased the level of Ki-67, and increased TUNEL-positive cells and cleaved caspase-3 in DU145 xenograft tumors implanted in mice. In addition, this combination treatment inhibited both the PI3K and MEK pathway primary in cultures from CRPC patients harboring PTEN loss, leading to synergistic anti-tumor effect.
  
  
  CONCLUSIONS
  The combination of GSK2126458 and AZD6244 blocks both the RAS/RAF/MEK/ERK and PI3K/AKT/mTOR pathways simultaneously and is an effective strategy for the treatment of CRPCs.
authors.affiliation: Department of Urology, Kangwon National University Hospital, School of Medicine, Kangwon National University, Chuncheon, Gangwon-do, South Korea.
authors.forename: Hongzoo
authors.initials: H
authors.lastname: Park
authors.affiliation: Department of Urology, University of Ulsan College of Medicine, Asan Medical Center, Seoul, South Korea.|Institute for Innovative Cancer Research, University of Ulsan College of Medicine, Asan Medical Center, Seoul, South Korea.|Asan Institute for Life Sciences, University of Ulsan College of Medicine, Asan Medical Center, Seoul, South Korea.
authors.forename: Yunlim
authors.initials: Y
authors.lastname: Kim
authors.affiliation: Institute for Innovative Cancer Research, University of Ulsan College of Medicine, Asan Medical Center, Seoul, South Korea.|Asan Institute for Life Sciences, University of Ulsan College of Medicine, Asan Medical Center, Seoul, South Korea.
authors.forename: Jee-Won
authors.initials: JW
authors.lastname: Sul
authors.affiliation: Department of Urology, University of Ulsan College of Medicine, Asan Medical Center, Seoul, South Korea.
authors.forename: In Gab
authors.initials: IG
authors.lastname: Jeong
authors.affiliation: Institute for Innovative Cancer Research, University of Ulsan College of Medicine, Asan Medical Center, Seoul, South Korea.|Asan Institute for Life Sciences, University of Ulsan College of Medicine, Asan Medical Center, Seoul, South Korea.
authors.forename: Hye-Jin
authors.initials: HJ
authors.lastname: Yi
authors.affiliation: Asan Institute for Life Sciences, University of Ulsan College of Medicine, Asan Medical Center, Seoul, South Korea.
authors.forename: Jae Beom
authors.initials: JB
authors.lastname: Ahn
authors.affiliation: Bioevaluation Center, Korea Research Institute of Bioscience and Biotechnology, Ochang, Cheongwon, South Korea.
authors.forename: Jong Soon
authors.initials: JS
authors.lastname: Kang
authors.affiliation: Bioevaluation Center, Korea Research Institute of Bioscience and Biotechnology, Ochang, Cheongwon, South Korea.
authors.forename: Jieun
authors.initials: J
authors.lastname: Yun
authors.affiliation: Institute for Innovative Cancer Research, University of Ulsan College of Medicine, Asan Medical Center, Seoul, South Korea.|Asan Institute for Life Sciences, University of Ulsan College of Medicine, Asan Medical Center, Seoul, South Korea.
authors.forename: Jung Jin
authors.initials: JJ
authors.lastname: Hwang
authors.affiliation: Department of Urology, University of Ulsan College of Medicine, Asan Medical Center, Seoul, South Korea.|Institute for Innovative Cancer Research, University of Ulsan College of Medicine, Asan Medical Center, Seoul, South Korea.|Asan Institute for Life Sciences, University of Ulsan College of Medicine, Asan Medical Center, Seoul, South Korea.
authors.forename: Choung-Soo
authors.initials: CS
authors.lastname: Kim
mesh_terms: D000818:Animals; D017209:Apoptosis / Q000187:drug effects*; D001562:Benzimidazoles / Q000494:pharmacology* / Q000627:therapeutic use; D053148:Caspase 3 / Q000378:metabolism; D002453:Cell Cycle / Q000187:drug effects; D045744:Cell Line, Tumor; D004357:Drug Synergism; D006801:Humans; D008297:Male; D051379:Mice; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism; D000081082:Phosphoinositide-3 Kinase Inhibitors; D010766:Phosphorylation / Q000187:drug effects; D064129:Prostatic Neoplasms, Castration-Resistant / Q000188:drug therapy* / Q000378:metabolism / Q000473:pathology; D047428:Protein Kinase Inhibitors / Q000494:pharmacology* / Q000627:therapeutic use; D051057:Proto-Oncogene Proteins c-akt / Q000378:metabolism; D011724:Pyridazines; D011804:Quinolines / Q000494:pharmacology* / Q000627:therapeutic use; D013449:Sulfonamides / Q000494:pharmacology* / Q000627:therapeutic use; D058570:TOR Serine-Threonine Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism; D016896:Treatment Outcome; D023041:Xenograft Model Antitumor Assays; D000096926:Benzenesulfonamides
chemical_list: D001562:Benzimidazoles; D053148:Caspase 3; D019869:Phosphatidylinositol 3-Kinases; D000081082:Phosphoinositide-3 Kinase Inhibitors; D047428:Protein Kinase Inhibitors; D051057:Proto-Oncogene Proteins c-akt; D011724:Pyridazines; D011804:Quinolines; D013449:Sulfonamides; D058570:TOR Serine-Threonine Kinases; C517975:AZD 6244; C561454:omipalisib; D000096926:Benzenesulfonamides; C546842:MTOR protein, human
keywords: MEK inhibitor; PI3K inhibitor; castration-resistant prostate cancer; prostate cancer; targeted therapy