title: Mutant PIK3CA controls DUSP1-dependent ERK 1/2 activity to confer response to AKT target therapy.
abstract: BACKGROUND
  Alterations in the phosphoinositide 3-kinase/AKT/mammalian target of rapamycin (PI3K/AKT/mTOR) signalling pathway are frequent in urothelial bladder cancer (BLCA) and thus provide a potential target for novel therapeutic strategies. We investigated the efficacy of the AKT inhibitor MK-2206 in BLCA and the molecular determinants that predict therapy response.
  
  
  METHODS
  Biochemical and functional effects of the AKT inhibitor MK-2206 were analysed on a panel of 11 BLCA cell lines possessing different genetic alterations. Cell viability (CellTiter-Blue, cell counts), apoptosis (caspase 3/7 activity) and cell cycle progression (EdU incorporation) were analysed to determine effects on cell growth and proliferation. cDNA or siRNA transfections were used to manipulate the expression of specific proteins such as wild-type or mutant PIK3CA, DUSP1 or CREB. For in vivo analysis, the chicken chorioallantoic membrane model was utilised and tumours were characterised by weight and biochemically for the expression of Ki-67 and AKT phosphorylation.
  
  
  RESULTS
  Treatment with MK-2206 suppressed AKT and S6K1 but not 4E-BP1 phosphorylation in all cell lines. Functionally, only cell lines bearing mutations in the hotspot helical domain of PIK3CA were sensitive to the drug, independent of other genetic alterations in the PI3K or MAPK signalling pathway. Following MK-2206 treatment, the presence of mutant PIK3CA resulted in an increase in DUSP1 expression that induced a decrease in ERK 1/2 phosphorylation. Manipulating the expression of mutant or wild-type PIK3CA or DUSP1 confirmed that this mechanism is responsible for the induction of apoptosis and the inhibition of tumour proliferation in vitro and in vivo, to sensitise cells to AKT target therapy.Conclusion or interpretation:PIK3CA mutations confer sensitivity to AKT target therapy in BLCA by regulating DUSP1 expression and subsequent ERK1/2 dephosphorylation and can potentially serve as a stratifying biomarker for treatment.
authors.affiliation: Department of Urology, Klinikum rechts der Isar, Technische Universität München, Ismaninger Strasse 22, Munich 81675, Germany.
authors.forename: A
authors.initials: A
authors.lastname: Sathe
authors.affiliation: Department of Urology, Klinikum rechts der Isar, Technische Universität München, Ismaninger Strasse 22, Munich 81675, Germany.
authors.forename: F
authors.initials: F
authors.lastname: Guerth
authors.affiliation: Department of Urology, Ulm University Medical Center, Prittwitzstrasse 43, Ulm 89075, Germany.
authors.forename: M V
authors.initials: MV
authors.lastname: Cronauer
authors.affiliation: Department of Urology, Klinikum rechts der Isar, Technische Universität München, Ismaninger Strasse 22, Munich 81675, Germany.
authors.forename: M M
authors.initials: MM
authors.lastname: Heck
authors.affiliation: Department of Urology, Klinikum rechts der Isar, Technische Universität München, Ismaninger Strasse 22, Munich 81675, Germany.
authors.forename: M
authors.initials: M
authors.lastname: Thalgott
authors.affiliation: Department of Urology, Klinikum rechts der Isar, Technische Universität München, Ismaninger Strasse 22, Munich 81675, Germany.
authors.forename: J E
authors.initials: JE
authors.lastname: Gschwend
authors.affiliation: Department of Urology, Klinikum rechts der Isar, Technische Universität München, Ismaninger Strasse 22, Munich 81675, Germany.
authors.forename: M
authors.initials: M
authors.lastname: Retz
authors.affiliation: Department of Urology, Klinikum rechts der Isar, Technische Universität München, Ismaninger Strasse 22, Munich 81675, Germany.
authors.forename: R
authors.initials: R
authors.lastname: Nawroth
mesh_terms: D000818:Animals; D017209:Apoptosis / Q000187:drug effects; D045744:Cell Line, Tumor; D002645:Chickens; D049033:Chorioallantoic Membrane; D058534:Class I Phosphatidylinositol 3-Kinases; D054638:Dual Specificity Phosphatase 1 / Q000502:physiology*; D048049:Extracellular Signal-Regulated MAP Kinases / Q000378:metabolism*; D006575:Heterocyclic Compounds, 3-Ring / Q000494:pharmacology*; D006801:Humans; D058990:Molecular Targeted Therapy; D009154:Mutation; D019869:Phosphatidylinositol 3-Kinases / Q000235:genetics / Q000502:physiology*; D010766:Phosphorylation; D051057:Proto-Oncogene Proteins c-akt / Q000037:antagonists & inhibitors*; D001749:Urinary Bladder Neoplasms / Q000188:drug therapy* / Q000473:pathology
chemical_list: D006575:Heterocyclic Compounds, 3-Ring; C548887:MK 2206; D019869:Phosphatidylinositol 3-Kinases; D058534:Class I Phosphatidylinositol 3-Kinases; C484760:PIK3CA protein, human; D051057:Proto-Oncogene Proteins c-akt; D048049:Extracellular Signal-Regulated MAP Kinases; C517019:DUSP1 protein, human; D054638:Dual Specificity Phosphatase 1