title: Combined targeting of AKT and mTOR using MK-2206 and RAD001 is synergistic in the treatment of cholangiocarcinoma.
abstract: Cholangiocarcinoma (CCA) is a rare, but devastating disease arising from the epithelium of intrahepatic and extrahepatic bile ducts. There are neither effective systemic therapies nor satisfying treatment options for inoperable CCA. Histopathological and biochemical studies of CCA show frequent dysregulation of the phosphatidylinositol 3-kinase/AKT/mammalian target of rapamycin (mTOR) pathway. Therefore, we investigated the efficacy of the mTOR inhibitor RAD001 and the impact of AKT signaling following mTOR inhibition in the treatment of CCA. RAD001 significantly inhibits proliferation of CCA cell lines, however, a concentration-dependent and isoform specific feedback activation of the three AKT isoforms (AKT1, AKT2 and AKT3) was observed after mTOR inhibition. As activation of AKT might limit the RAD001-mediated anti-tumor effect, the efficacy of combined mTOR and AKT inhibition was investigated using the allosteric AKT inhibitor MK-2206. Our results show that inhibition of AKT potentiates the efficacy of mTOR inhibition both in vitro and in a xenograft mouse model in vivo. Mechanistically, the antiproliferative effect of the pan-AKT inhibitor MK2206 in the CCA cell line TFK-1 was due to inhibition of AKT1 and AKT2, because knockdown of either AKT1 or AKT2, but not AKT3, showed a synergistic reduction of cell proliferation in combination with mTOR treatment. Finally, using an AKT isoform specific in vitro kinase assay, enzymatic activity of each of the three AKT isoforms was detected in all tissue samples from CCA patients, analyzed. In summary, our preclinical data suggest that combined targeting of mTOR and AKT using RAD001 and MK-2206 might be a new, effective strategy for the treatment of CCA.
authors.affiliation: Department of Hepatobiliary and Transplant Surgery, University Medical Center Hamburg-Eppendorf, Hamburg, Germany.
authors.forename: Florian
authors.initials: F
authors.lastname: Ewald
authors.forename: Nicole
authors.initials: N
authors.lastname: Grabinski
authors.forename: Astrid
authors.initials: A
authors.lastname: Grottke
authors.forename: Sabine
authors.initials: S
authors.lastname: Windhorst
authors.forename: Dominik
authors.initials: D
authors.lastname: Nörz
authors.forename: Lisa
authors.initials: L
authors.lastname: Carstensen
authors.forename: Katharina
authors.initials: K
authors.lastname: Staufer
authors.forename: Bianca T
authors.initials: BT
authors.lastname: Hofmann
authors.forename: Frank
authors.initials: F
authors.lastname: Diehl
authors.forename: Kerstin
authors.initials: K
authors.lastname: David
authors.forename: Udo
authors.initials: U
authors.lastname: Schumacher
authors.forename: Björn
authors.initials: B
authors.lastname: Nashan
authors.forename: Manfred
authors.initials: M
authors.lastname: Jücker
mesh_terms: D000818:Animals; D017209:Apoptosis / Q000187:drug effects; D001650:Bile Duct Neoplasms / Q000188:drug therapy* / Q000378:metabolism / Q000473:pathology; D001653:Bile Ducts, Intrahepatic / Q000187:drug effects* / Q000378:metabolism / Q000473:pathology; D015153:Blotting, Western; D002453:Cell Cycle / Q000187:drug effects; D049109:Cell Proliferation / Q000187:drug effects; D018281:Cholangiocarcinoma / Q000188:drug therapy* / Q000378:metabolism / Q000473:pathology; D004357:Drug Synergism; D000068338:Everolimus; D005434:Flow Cytometry; D006575:Heterocyclic Compounds, 3-Ring / Q000494:pharmacology*; D006801:Humans; D047468:Immunoprecipitation; D051379:Mice; D058539:Phosphatidylinositol 3-Kinase / Q000378:metabolism; D047428:Protein Kinase Inhibitors / Q000494:pharmacology*; D051057:Proto-Oncogene Proteins c-akt / Q000037:antagonists & inhibitors* / Q000378:metabolism; D015398:Signal Transduction; D020123:Sirolimus / Q000031:analogs & derivatives* / Q000494:pharmacology; D058570:TOR Serine-Threonine Kinases / Q000037:antagonists & inhibitors* / Q000378:metabolism; D014407:Tumor Cells, Cultured; D014410:Tumor Stem Cell Assay
chemical_list: D006575:Heterocyclic Compounds, 3-Ring; C548887:MK 2206; D047428:Protein Kinase Inhibitors; D000068338:Everolimus; C546842:MTOR protein, human; D058539:Phosphatidylinositol 3-Kinase; D051057:Proto-Oncogene Proteins c-akt; D058570:TOR Serine-Threonine Kinases; D020123:Sirolimus
keywords: AKT; Cholangiocarcinoma; MK-2206; RAD001; mTOR