bms345541 and Leukemia--Myeloid--Acute

NF-κB mediates acquired resistance in acute myeloid leukemia (AML) cells treated with DNA-damaging agents. Because DNA repair is the major molecular shift that alters sensitivity to DNA-damaging agents, we explored whether activation of the NF-κB pathway promotes AML cell survival by regulating DNA repair after chemotherapy. Our results showed that RELA, an important subunit of NF-κB, regulated DNA repair by binding to the promoter region of the

Topics: Animals; DNA Damage; DNA Repair; Feedback, Physiological; Gene Knockdown Techniques; Heterografts; Humans; Imidazoles; Leukemia, Myeloid, Acute; Male; Mice; Mice, Inbred BALB C; Mice, Nude; NF-kappa B; Phthalazines; Piperazines; Poly (ADP-Ribose) Polymerase-1; Promoter Regions, Genetic; Quinoxalines; Transcription Factor RelA

Sustained NF-κB activation is often observed in acute myeloid leukemia (AML); therefore, proteasome inhibition has been proposed to efficiently target AML cells. In this study, we questioned whether leukemic stem cell-enriched CD34(+) cells are sensitive to the proteasome inhibitor bortezomib. Surprisingly, we observed in short-term and long-term culture assays that CD34(-) AML cells were more sensitive to bortezomib treatment compared with the CD34(+) AML cells at a clinical relevant dosage. Cotreatment with the apoptosis-inducing cytokine TRAIL did not enhance cell death in CD34(+) AML cells, in contrast to the effects in AML cell lines. The better survival of CD34(+) AML cells upon bortezomib treatment was due to a persisting NF-κB activity that could be overcome by the IKK inhibitor BMS-345541. This difference in sensitivity might be related to differences in NF-κB activation in AML CD34(+) versus CD34(-) cells, as suggested by a gene expression profiling study. Besides NF-κB, MCL-1 strongly determines the effectiveness of bortezomib. MCL-1 accumulated in CD34(+) AML cells upon bortezomib treatment and inhibition of MCL-1 by shRNA, or Obatoclax, significantly improved the sensitivity of CD34(+) AML cells to bortezomib. These results demonstrate that combining bortezomib with specific NF-κB or MCL-1 inhibitors might potentially target the leukemic stem cells.

Topics: Antigens, CD34; Boronic Acids; Bortezomib; Coculture Techniques; Drug Resistance, Neoplasm; Gene Expression Regulation, Leukemic; Hematopoietic Stem Cells; Humans; I-kappa B Kinase; Imidazoles; Leukemia, Myeloid, Acute; Myeloid Cell Leukemia Sequence 1 Protein; Neoplasm Proteins; Neoplastic Stem Cells; NF-kappa B; Primary Cell Culture; Protease Inhibitors; Proto-Oncogene Proteins c-bcl-2; Pyrazines; Quinoxalines; Recombinant Proteins; RNA, Small Interfering; Stromal Cells; TNF-Related Apoptosis-Inducing Ligand; Tumor Cells, Cultured

Despite progress in the treatment of acute myelogenous leukaemia (AML) the outcome often remains poor. Tumour necrosis factor related apoptosis-inducing ligand (TRAIL) is a promising therapeutic agent in many different types of tumours, but AML cells are relatively insensitive to TRAIL-induced apoptosis. Here we show that TRAIL-induced apoptosis in AML cells is predominantly mediated by death receptor 4 (DR4) and not DR5. Therefore, we constructed a variant of TRAIL (rhTRAIL-C3) that is a strong inducer of DR4-mediated apoptosis. TRAIL-C3 demonstrated much stronger pro-apoptotic activity than wild-type (WT) TRAIL in a panel of AML cell lines as well as in primary AML blasts. The higher pro-apoptotic potential was further enhanced when the TRAIL mutant was used in combination with BMS-345541, a selective inhibitor of inhibitor-κB kinases. It illustrates that combination of this TRAIL variant with chemotherapeutics or other targeted agents can kill AML with high efficacy. This may represent a major advantage over the currently used therapies that have serious toxic side effects. The high efficacy of rhTRAIL-C3 containing therapies may enable the use of lower drug doses to reduce the toxic side effects and improve patient outcome. Our findings suggest that the rational design of TRAIL variants that target DR4 potentiate the death-inducing activity of TRAIL and offer a novel therapeutic strategy for the treatment of AML.

Topics: Adult; Aged; Aged, 80 and over; Apoptosis; Cell Line, Tumor; Epidermal Cells; Female; Humans; Imidazoles; Keratinocytes; Leukemia, Myeloid, Acute; Leukocyte Count; Male; Membrane Potentials; Middle Aged; Quinoxalines; Receptors, TNF-Related Apoptosis-Inducing Ligand; TNF-Related Apoptosis-Inducing Ligand

The Tie-2 receptor can bind its agonistic ligand Angiopoietin-1 (Ang-1) and the potential antagonist Ang-2. Tie-2 can be expressed both by primary human acute myeloid leukaemia (AML) cells and endothelial cells, and Tie-2-blocking antibodies are now being evaluated in clinical trials for cancer treatment.. We investigated the effects of Tie-2-blocking antibodies, exogenous Ang-2 and pharmacological agents on AML cell proliferation and the release of angioregulatory mediators.. Tie-2-blocking antibodies had a growth inhibitory effect on human AML cells co-cultured with microvascular endothelial cells, but this inhibition was not observed when leukaemic cells were co-cultured with fibroblasts or osteoblasts. AML cell viability in co-cultures was not altered by anti-Tie-2. Furthermore, anti-Tie-2 decreased hepatocyte growth factor (HGF) levels and increased CXCL8 levels in co-cultures, whereas the levels of endocan (a proteoglycan released by endothelial cells) were not altered. The only significant effects of exogenous Ang-2 were decreased levels of HGF and endocan. Constitutive AML cell release of agonistic Ang-1 was decreased by the proteasomal inhibitor bortezomib and the specific IkappaB-kinase/NFkappaB inhibitor BMS-345541.. We conclude that various strategies for inhibition of Tie-2-mediated signalling should be considered in AML therapy, possibly in combination with other antiangiogenic strategies.

Topics: Adult; Aged; Aged, 80 and over; Angiopoietin-1; Angiopoietin-2; Antibodies; Boronic Acids; Bortezomib; Cell Proliferation; Cells, Cultured; Coculture Techniques; Endothelial Cells; Female; Fibroblasts; Hepatocyte Growth Factor; Humans; Imidazoles; Interleukin-8; Leukemia, Myeloid, Acute; Male; Middle Aged; Neoplasm Proteins; Osteoblasts; Proteoglycans; Pyrazines; Quinoxalines; Receptor Cross-Talk; Receptor, TIE-2; Signal Transduction