nutlin-3a and Leukemia--Myeloid

A range of cell types of mesenchymal origin express α-smooth muscle actin (α-SMA), a protein that plays a key role in controlling cell motility and differentiation along the fibrocyte and myofibroblast lineages. Although α-SMA is often expressed in stromal cells associated to a variety of cancers including hematological malignancies, up to now the role of anti-cancer drugs on α-SMA has not been deeply investigated. In this study, we demonstrated that Nutlin-3, the small molecule inhibitor of the MDM2/p53 interactions, significantly up-regulated the mRNA and protein levels of α-SMA in normal macrophages as well as in p53(wild-type) but not in p53(mutated/null) myeloid leukemic cells. The p53-dependence of α-SMA up-regulation induced by Nutlin-3 was demonstrated in experiments performed with siRNA for p53. Of note, Nutlin-3 mediated up-regulation of α-SMA in OCI leukemic cells was accompanied by cell adhesion to plastic substrate and by reduced cell migratory response in transwell assays. Notably, the role of α-SMA induction in the modulation of myeloid cell migration was clearly documented in α-SMA gene knockdown experiments. In addition, Nutlin-3 significantly up-regulated α-SMA expression in primary endothelial cells, but not in fibroblasts and mesenchymal stem cells (MSC). Conversely, transforming growth factor-β1 up-regulated α-SMA in fibroblasts and MSC, but not in macrophages and endothelial cells. Taken together, these data indicate that Nutlin-3 is a potent inducer of α-SMA in both normal and leukemic myeloid cells as well as in endothelial cells.

Topics: Actins; Cell Movement; Cells, Cultured; Endothelial Cells; Fibroblasts; Humans; Imidazoles; Leukemia, Myeloid; Macrophages; Mesenchymal Stem Cells; Piperazines; Proto-Oncogene Proteins c-mdm2; RNA, Small Interfering; Signal Transduction; Transforming Growth Factor beta1; Tumor Suppressor Protein p53

Molecular aberrations of the Ras/Raf/mitogen-activated protein kinase/extracellular signal-regulated kinase (ERK) kinase (MEK)/ERK and/or Murine double minute (MDM2)/p53 signaling pathways have been reported in 80% and 50% of primary acute myeloid leukemia (AML) samples and confer poor outcome. In this study, antileukemic effects of combined MEK inhibition by AZD6244 and nongenotoxic p53 activation by MDM2 antagonist Nutlin-3a were investigated. Simultaneous blockade of MEK and MDM2 signaling by AZD6244 and Nutlin-3a triggered synergistic proapoptotic responses in AML cell lines [combination index (CI) = 0.06 +/- 0.03 and 0.43 +/- 0.03 in OCI/AML3 and MOLM13 cells, respectively] and in primary AML cells (CI = 0.52 +/- 0.01). Mechanistically, the combination upregulated levels of BH3-only proteins Puma and Bim, in part via transcriptional upregulation of the FOXO3a transcription factor. Suppression of Puma and Bim by short interfering RNA rescued OCI/AML3 cells from AZD/Nutlin-induced apoptosis. These results strongly indicate the therapeutic potential of combined MEK/MDM2 blockade in AML and implicate Puma and Bim as major regulators of AML cell survival.

Topics: Acute Disease; Apoptosis; Apoptosis Regulatory Proteins; Bcl-2-Like Protein 11; Benzimidazoles; Drug Synergism; Extracellular Signal-Regulated MAP Kinases; Forkhead Box Protein O3; Forkhead Transcription Factors; HL-60 Cells; Humans; Imidazoles; Leukemia, Myeloid; MAP Kinase Signaling System; Membrane Proteins; Myeloid Cell Leukemia Sequence 1 Protein; Phosphorylation; Piperazines; Proto-Oncogene Proteins; Proto-Oncogene Proteins c-bcl-2; Proto-Oncogene Proteins c-mdm2; U937 Cells

The survival of most patients with acute myelogenous leukemia (AML) remains poor, and novel therapeutic approaches are needed to improve outcomes. Given that the fraction of AML with mutated p53 is small ( approximately 10%), it appears rational to study MDM2 inhibitors as therapy for AML. Here, we report results of a detailed characterization of sensitivity and resistance to treatment ex vivo with the MDM2 inhibitor MI219 in AML blasts from 109 patients. In line with previous observations, all AML cases with mutated p53 were resistant to MI219. Importantly, approximately 30% of AML cases with unmutated p53 also demonstrated primary resistance to MI219. Analysis of potential mechanisms associated with MI219 resistance in AML blasts with wild-type p53 uncovered distinct molecular defects, including low or absent p53 protein induction after MDM2 inhibitor treatment or external irradiation. Furthermore, a separate subset of resistant blasts displayed robust p53 protein induction after MI219 treatment, indicative of defective p53 protein function or defects in the apoptotic p53 network. Finally, analysis of very sensitive AML cases uncovered a strong and significant association with mutated Flt3 status (Flt3-ITD), which for the first time identified a clinically high-risk group of AML that may particularly benefit from MDM2 inhibitor treatment.

Topics: Acute Disease; Adult; Aged; Aged, 80 and over; Apoptosis; Cell Cycle Proteins; Cell Line, Tumor; Cells, Cultured; Drug Resistance, Neoplasm; Female; Flow Cytometry; fms-Like Tyrosine Kinase 3; Humans; Imidazoles; Immunoblotting; Indoles; Leukemia, Myeloid; Male; Middle Aged; Nuclear Proteins; Piperazines; Proto-Oncogene Proteins; Proto-Oncogene Proteins c-mdm2; Reverse Transcriptase Polymerase Chain Reaction; Spiro Compounds; Tumor Cells, Cultured; Tumor Suppressor Protein p53; Young Adult

The small-molecule inhibitor of murine double minute (MDM-2), Nutlin-3, induced variable apoptosis in primary acute myeloid leukemia (AML) blasts and promoted myeloid maturation of surviving cells, as demonstrated by analysis of CD11b and CD14 surface antigens and by morphologic examination. Although the best-characterized activity of Nutlin-3 is activation of the p53 pathway, Nutlin-3 induced maturation also in one AML sample characterized by p53 deletion, as well as in the p53(-/-) human myeloblastic HL-60 cell line. At the molecular level, the maturational activity of Nutlin-3 in HL-60 cells was accompanied by the induction of E2F1 transcription factor, and it was significantly counteracted by specific gene knockdown with small interfering RNA for E2F1. Moreover, Nutlin-3, as well as tumor necrosis factor (TNF) alpha, potentiated the maturational activity of recombinant TNF-related apoptosis-inducing ligand (TRAIL) in HL-60 cells. However, although TNF-alpha significantly counteracted the proapoptotic activity of TRAIL, Nutlin-3 did not interfere with the proapoptotic activity of TRAIL. Taken together, these data disclose a novel, potentially relevant therapeutic role for Nutlin-3 in the treatment of both p53 wild-type and p53(-/-) AML, possibly in association with recombinant TRAIL.

Topics: Acute Disease; Antineoplastic Agents; Apoptosis; Blotting, Western; CD11b Antigen; Cell Differentiation; Cell Line, Tumor; Cell Survival; E2F1 Transcription Factor; Flow Cytometry; Humans; Imidazoles; Immunoprecipitation; Leukemia, Myeloid; Lipopolysaccharide Receptors; Piperazines; Proto-Oncogene Proteins c-mdm2; Retinoblastoma Protein; RNA, Small Interfering; TNF-Related Apoptosis-Inducing Ligand; Transfection; Tumor Necrosis Factor-alpha; Tumor Suppressor Protein p53