laq824 and Leukemia--Myeloid--Acute

Hydroxamic acid analog pan-histone deacetylase (HDAC) inhibitors (HA-HDIs) have shown preclinical and clinical activity against human acute leukemia. Here we describe HA-HDI-resistant human acute myeloid leukemia (AML) HL-60 (HL-60/LR) cells that are resistant to LAQ824, vorinostat, LBH589, and sodium butyrate. HL-60/LR cells show increased expression of HDACs 1, 2, and 4 but lack HDAC6 expression, with concomitant hyperacetylation of heat shock protein 90 (hsp90). Treatment with HA-HDI failed to further augment hsp90 acetylation, or increase the levels of p21 or reactive oxygen species (ROSs), in HL-60/LR versus HL-60 cells. Although cross-resistant to antileukemia agents (eg, cytarabine, etoposide, and TRAIL), HL-60/LR cells are collaterally sensitive to the hsp90 inhibitor 17-AAG. Treatment with 17-AAG did not induce hsp70 or deplete the hsp90 client proteins AKT and c-Raf. HL-60/LR versus HL-60 cells display a higher growth fraction and shorter doubling time, along with a shorter interval to generation of leukemia and survival in nonobese diabetic/severe combined immunodeficient (NOD/SCID) mice. Thus, resistance of AML cells to HA-HDIs is associated with loss of HDAC6, hyperacetylation of hsp90, aggressive leukemia phenotype, and collateral sensitivity to 17-AAG. These findings suggest that an hsp90 inhibitor-based antileukemia therapy may override de novo or acquired resistance of AML cells to HA-HDIs.

Topics: Acetylation; Animals; Antineoplastic Agents; Apoptosis; Azacitidine; Benzoquinones; Cell Differentiation; Cell Proliferation; Decitabine; DNA-Binding Proteins; Drug Resistance, Neoplasm; Enzyme Inhibitors; Heat Shock Transcription Factors; Histone Deacetylase Inhibitors; HL-60 Cells; HSP70 Heat-Shock Proteins; HSP90 Heat-Shock Proteins; Humans; Hydroxamic Acids; Indoles; Lactams, Macrocyclic; Leukemia, Myeloid, Acute; Mice; Mice, Inbred NOD; Neoplasm Proteins; Panobinostat; S Phase; Transcription Factors; Tubulin; Vorinostat

Mutant FLT-3 receptor tyrosine kinase is a client protein of the molecular chaperone heat shock protein 90 and is commonly present and contributes to the leukemia phenotype in acute myelogenous leukemia (AML). LAQ824, a cinnamyl hydroxamate histone deacetylase inhibitor, is known to induce acetylation and inhibition of heat shock protein 90. Here, we determined the effects of LAQ824 and/or PKC412 (a FLT-3 kinase inhibitor) on the levels of mutant FLT-3 and its downstream signaling, as well as growth arrest and cell-death of cultured and primary human AML cells.. The effect of LAQ824 and/or PKC412 treatment was determined on the levels of FLT-3 and phosphorylated (p)-FLT-3, on downstream pro-growth and pro-survival effectors, e.g., p-STAT5, p-AKT, and p-extracellular signal-regulated kinase (ERK) 1/2, and on the cell cycle status and apoptosis in the cultured MV4-11 and primary AML cells with mutant FLT-3.. Treatment with LAQ824 promoted proteasomal degradation and attenuation of the levels of FLT-3 and p-FLT-3, associated with cell cycle G(1)-phase accumulation and apoptosis of MV4-11 cells. This was accompanied by attenuation of p-STAT5, p-AKT, and p-ERK1/2 levels. STAT-5 DNA-binding activity and the levels of c-Myc and oncostatin M were also down-regulated. Cotreatment with LAQ824 and PKC412 synergistically induced apoptosis of MV4-11 cells and induced more apoptosis of the primary AML cells expressing mutant FLT-3. This was also associated with more attenuation of p-FLT-3, p-AKT, p-ERK1/2, and p-STAT5.. The combination of LAQ824 and PKC412 is highly active against human AML cells with mutant FLT-3, which merits in vivo studies of the combination against human AML.

Topics: Antineoplastic Combined Chemotherapy Protocols; Apoptosis; Blotting, Western; Cell Cycle; Cell Line, Tumor; DNA; DNA-Binding Proteins; Dose-Response Relationship, Drug; Down-Regulation; Drug Synergism; Enzyme Inhibitors; Exons; Flow Cytometry; fms-Like Tyrosine Kinase 3; G1 Phase; Histone Deacetylase Inhibitors; Humans; Hydroxamic Acids; Leukemia, Myeloid, Acute; Milk Proteins; Mitogen-Activated Protein Kinase 1; Mitogen-Activated Protein Kinase 3; Mutation; Phosphorylation; Proteasome Endopeptidase Complex; Protein Binding; Protein Serine-Threonine Kinases; Protein Structure, Tertiary; Proto-Oncogene Proteins; Proto-Oncogene Proteins c-akt; Receptor Protein-Tyrosine Kinases; Reverse Transcriptase Polymerase Chain Reaction; RNA, Messenger; Signal Transduction; STAT5 Transcription Factor; Staurosporine; Time Factors; Trans-Activators