title: Selective Akt inhibitors synergize with tyrosine kinase inhibitors and effectively override stroma-associated cytoprotection of mutant FLT3-positive AML cells.
abstract: OBJECTIVE
  Tyrosine kinase inhibitor (TKI)-treated acute myeloid leukemia (AML) patients commonly show rapid and significant peripheral blood blast cell reduction, however a marginal decrease in bone marrow blasts. This suggests a protective environment and highlights the demand for a better understanding of stromal:leukemia cell communication. As a strategy to improve clinical efficacy, we searched for novel agents capable of potentiating the stroma-diminished effects of TKI treatment of mutant FLT3-expressing cells.
  
  
  METHODS
  We designed a combinatorial high throughput drug screen using well-characterized kinase inhibitor-focused libraries to identify novel kinase inhibitors capable of overriding stromal-mediated resistance to TKIs, such as PKC412 and AC220. Standard liquid culture proliferation assays, cell cycle and apoptosis analysis, and immunoblotting were carried out with cell lines or primary AML to validate putative candidates from the screen and characterize the mechanism(s) underlying observed synergy.
  
  
  CONCLUSIONS
  Our study led to the observation of synergy between selective Akt inhibitors and FLT3 inhibitors against mutant FLT3-positive AML in either the absence or presence of stroma. Our findings are consistent with evidence that Akt activation is characteristic of mutant FLT3-transformed cells, as well as observed residual Akt activity following FLT3 inhibitor treatment. In conclusion, our study highlights the potential importance of Akt as a signaling factor in leukemia survival, and supports the use of the co-culture chemical screen to identify agents able to potentiate TKI anti-leukemia activity in a cytoprotective microenvironment.
authors: Department of Medical Oncology, Dana Farber Cancer Institute, Harvard Medical School, Boston, Massachusetts, USA. ellen_weisberg@dfci.harvard.edu
authors: Ellen
authors: E
authors: Weisberg
authors: Qingsong
authors: Q
authors: Liu
authors: Xin
authors: X
authors: Zhang
authors: Erik
authors: E
authors: Nelson
authors: Martin
authors: M
authors: Sattler
authors: Feiyang
authors: F
authors: Liu
authors: Maria
authors: M
authors: Nicolais
authors: Jianming
authors: J
authors: Zhang
authors: Constantine
authors: C
authors: Mitsiades
authors: Robert W
authors: RW
authors: Smith
authors: Richard
authors: R
authors: Stone
authors: Ilene
authors: I
authors: Galinsky
authors: Atsushi
authors: A
authors: Nonami
authors: James D
authors: JD
authors: Griffin
authors: Nathanael
authors: N
authors: Gray
mesh_terms: D017209:Apoptosis / Q000187:drug effects; D052160:Benzothiazoles / Q000008:administration & dosage; D001854:Bone Marrow Cells / Q000166:cytology / Q000187:drug effects / Q000378:metabolism; D002450:Cell Communication / Q000187:drug effects; D002453:Cell Cycle / Q000187:drug effects; D049109:Cell Proliferation / Q000187:drug effects; D004354:Drug Screening Assays, Antitumor; D004357:Drug Synergism; D006801:Humans; D015470:Leukemia, Myeloid, Acute / Q000188:drug therapy / Q000378:metabolism / Q000473:pathology; D010671:Phenylurea Compounds / Q000008:administration & dosage; D047428:Protein Kinase Inhibitors / Q000008:administration & dosage*; D051057:Proto-Oncogene Proteins c-akt / Q000037:antagonists & inhibitors / Q000378:metabolism*; D019311:Staurosporine / Q000008:administration & dosage / Q000031:analogs & derivatives; D017154:Stromal Cells / Q000166:cytology* / Q000187:drug effects / Q000378:metabolism*; D051941:fms-Like Tyrosine Kinase 3 / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*
chemical_list: D052160:Benzothiazoles; D010671:Phenylurea Compounds; D047428:Protein Kinase Inhibitors; C544967:quizartinib; C497970:FLT3 protein, human; D051941:fms-Like Tyrosine Kinase 3; D051057:Proto-Oncogene Proteins c-akt; D019311:Staurosporine; C059539:midostaurin