nitrophenols and Leukemia--Myeloid

Topics: Antineoplastic Agents; Azacitidine; Biphenyl Compounds; Bridged Bicyclo Compounds, Heterocyclic; Cell Line, Tumor; Humans; Leukemia, Myeloid; Nitrophenols; Piperazines; Proto-Oncogene Proteins c-bcl-2; Sulfonamides

Effects of concomitant inhibition of the PI3K/AKT/mTOR pathway and Bcl-2/Bcl-xL (BCL2L1) were examined in human myeloid leukemia cells. Tetracycline-inducible Bcl-2 and Bcl-xL dual knockdown sharply increased PI3K/AKT/mTOR inhibitor lethality. Conversely, inducible knockdown or dominant-negative AKT increased, whereas constitutively active AKT reduced lethality of the Bcl-2/Bcl-xL inhibitor ABT-737. Furthermore, PI3K/mTOR inhibitors (e.g., BEZ235 and PI-103) synergistically increased ABT-737-mediated cell death in multiple leukemia cell lines and reduced colony formation in leukemic, but not normal, CD34+ cells. Notably, increased lethality was observed in four of six primary acute myelogenous leukemia (AML) specimens. Responding, but not nonresponding, samples exhibited basal AKT phosphorylation. PI3K/mTOR inhibitors markedly downregulated Mcl-1 but increased Bim binding to Bcl-2/Bcl-xL; the latter effect was abrogated by ABT-737. Combined treatment also markedly diminished Bax/Bak binding to Mcl-1, Bcl-2, or Bcl-xL. Bax, Bak, or Bim (BCL2L11) knockdown or Mcl-1 overexpression significantly diminished regimen-induced apoptosis. Interestingly, pharmacologic inhibition or short hairpin RNA knockdown of GSK3α/β significantly attenuated Mcl-1 downregulation and decreased apoptosis. In a systemic AML xenograft model, dual tetracycline-inducible knockdown of Bcl-2/Bcl-xL sharply increased BEZ235 antileukemic effects. In a subcutaneous xenograft model, BEZ235 and ABT-737 coadministration significantly diminished tumor growth, downregulated Mcl-1, activated caspases, and prolonged survival. Together, these findings suggest that antileukemic synergism between PI3K/AKT/mTOR inhibitors and BH3 mimetics involves multiple mechanisms, including Mcl-1 downregulation, release of Bim from Bcl-2/Bcl-xL as well as Bak and Bax from Mcl-1/Bcl-2/Bcl-xL, and GSK3α/β, culminating in Bax/Bak activation and apoptosis. They also argue that combining PI3K/AKT/mTOR inhibitors with BH3 mimetics warrants attention in AML, particularly in the setting of basal AKT activation and/or addiction.

Topics: Animals; Apoptosis; Apoptosis Regulatory Proteins; bcl-2 Homologous Antagonist-Killer Protein; Bcl-2-Like Protein 11; bcl-X Protein; Biphenyl Compounds; Cell Line, Tumor; Female; Gene Knockdown Techniques; Glycogen Synthase Kinase 3; Humans; Imidazoles; Immunoblotting; Leukemia, Myeloid; Membrane Proteins; Mice; Mice, Inbred NOD; Mice, SCID; Myeloid Cell Leukemia Sequence 1 Protein; Nitrophenols; Phosphatidylinositol 3-Kinases; Piperazines; Proto-Oncogene Proteins; Proto-Oncogene Proteins c-akt; Proto-Oncogene Proteins c-bcl-2; Quinolines; Sulfonamides; TOR Serine-Threonine Kinases; Tumor Cells, Cultured; U937 Cells; Xenograft Model Antitumor Assays

FLT3 defines a promising target for the treatment of acute myeloid leukemia (AML). In contrast to their efficacy in cell lines, FLT3-specific inhibitors as single agents have only modest clinical activity in patients with AML. As demonstrated here, overexpression of anti-apoptotic proteins of the BCL2 family leads to resistance against FLT3 inhibitors in a hematopoietic cell line model with activating FLT3 mutations. The susceptibility to FLT3 inhibition could be restored by treatment with the novel BH3 mimetic ABT-737. Primary AML samples tested in our study showed a high expression of BCL2 protein, but not of BCL-xL or MCL1. BCL2 protein levels were not reduced after dephosphorylation of FLT3 and its downstream target STAT5 in patient samples with FLT3 internal tandem duplications. Interestingly, treatment with ABT-737 caused apoptotic cell death in all primary AML samples at submicromolar level and synergized efficiently with FLT3 inhibition in AML samples with activating FLT3 mutations. In contrast to AML cell lines, BCR-ABL transformed human cells showed resistance to ABT-737, which might be due to the induction of MCL1 by BCR-ABL. Inhibition of BCL2 family members might define a novel highly efficient and specific strategy in the combined or monotreatment of AML.

Topics: Acute Disease; Adult; Aged; Aged, 80 and over; Apoptosis; bcl-X Protein; Biphenyl Compounds; Blotting, Western; Cell Proliferation; Cells, Cultured; Drug Resistance, Neoplasm; Flow Cytometry; fms-Like Tyrosine Kinase 3; Humans; Karyotyping; Leukemia, Myeloid; Middle Aged; Molecular Mimicry; Myeloid Cell Leukemia Sequence 1 Protein; Neoplasm Proteins; Nitrophenols; Peptide Fragments; Piperazines; Proto-Oncogene Proteins; Proto-Oncogene Proteins c-bcl-2; Signal Transduction; STAT5 Transcription Factor; Sulfonamides; Trans-Activators

Topics: Acid Phosphatase; Adult; Alkaline Phosphatase; Bone Marrow Examination; Female; Humans; Leukemia, Myeloid; Leukocyte Count; Leukocytes; Male; Muramidase; Nitrophenols; Remission, Spontaneous; Sarcoidosis

Topics: Acid Phosphatase; Blood Platelets; Bone Marrow; Bone Marrow Cells; Chromatography, DEAE-Cellulose; Chromatography, Ion Exchange; Electrophoresis, Disc; Fluorides; Gaucher Disease; Histocytochemistry; Humans; Isoenzymes; Leukemia; Leukemia, Lymphoid; Leukemia, Myeloid; Leukemia, Myeloid, Acute; Leukocytes; Lymphatic Diseases; Lymphocytes; Lymphoma, Non-Hodgkin; Molecular Weight; Monocytes; Nitrophenols; Polycythemia Vera; Staining and Labeling; Tartrates