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Gene expression profiles of bone marrow (BM) CD34-derived megakaryocytic cells (MKs) were compared in patients with essential thrombocythemia (ET) and healthy subjects using oligonucleotide microarray analysis to identify differentially expressed genes and disease-specific transcripts. We found that proapoptotic genes such as BAX, BNIP3, and BNIP3L were down-regulated in ET MKs together with genes that are components of the mitochondrial permeability transition pore complex, a system with a pivotal role in apoptosis. Conversely, antiapoptotic genes such as IGF1-R and CFLAR were up-regulated in the malignant cells, as was the SDF1 gene, which favors cell survival. On the basis of the array results, we characterized apoptosis of normal and ET MKs by time-course evaluation of annexin-V and sub-G1 peak DNA stainings of immature and mature MKs after culture in serum-free medium with an optimal thrombopoietin concentration, and annexin-V–positive MKs only, with decreasing thrombopoietin concentrations. ET MKs were more resistant to apoptosis than their normal counterparts. We conclude that imbalance between proliferation and apoptosis seems to be an important step in malignant ET megakaryocytopoiesis.

The expression of cytotoxic T-lymphocyte antigen-4 (CTLA-4) molecule in human normal and neoplastic hematopoietic cells, both on the cell membrane and in the intracellular compartment, was evaluated. Flow cytometric analysis carried out with a panel of anti-CTLA-4 human single-chain fragment of variable domain (scFv) antibodies revealed that CTLA-4 was not expressed on the surface, whereas it was highly expressed within the cytoplasm, in freshly isolated peripheral blood mononuclear cells (PBMCs), T cells, B cells, CD34+ stem cells, and granulocytes. Various treatments with agents able to specifically activate each cell type induced CTLA-4 expression on the surface of these cells. Similarly, increased CTLA-4 expression Was observed in different hematopoietic cell lines although they also expressed surface CTLA-4, at different degrees of intensity, before activation. Surprisingly, CTLA-4 RNA transcripts were detectable in such cell lines only after nested polymerase chain reaction (PCR) specific for CTLA-4 extracellular domain, suggesting a very fast CTLA-4 RNA processing accompanied by prolonged CTLA-4 protein accumulation. We further demonstrated surface expression of CTLA-4 in a variety of acute and chronic myeloid leukemias (AMLs and CMLs) and B- and T-lymphoid leukemias, either adult or pediatric. CTLA-4 was expressed in 25% to 85% of AMLs and CMLs depending on the leukemia subtype and the epitope analyzed, whereas in acute B-and T-leukemias CTLA-4 expression was mainly cytoplasmic. Chronic B leukemias appeared to express CTLA-4, both on the surface and in cytoplasm, whereas few cases tested of chronic T leukemias were negative. Two anti-CTLA-4 immunotoxins (scFvs-saporin) induced in vitro apoptosis of neoplastic cells from a representative AML, suggesting a novel immunotherapeutic approach to AM L based on CTLA-4 targeting. © 2003 by The American Society of Hematology.

Background. Recently, gene expression profiling (GEP) indicated histone-deacetylases (HDAC) as potential therapeutic targets in peripheral T-cell lymphomas (PTCL) not otherwise specified (NOS), the commonest PTCL type. Consistently, phase II trials demonstrated the efficacy of some HDAC inhibitors (HDACi), including SAHA, which was approved for cutaneous T-cell lymphomas (CTCL) treatment. Aims and methods. We investigated the anti-tumour effects of ITF2357 (Italfarmaco, Italy), a novel hydroxamic acid HDACi, on PTCL primarily-cultured cells and cell lines (HH and FEDP), and in a xenografted mouse-model of CTCL. Cultured cells were incubated with different dosages of ITF2357 and SAHA (ranging from 0.5 to 2.5 mM). Cell viability, assessed by trypan-blue exclusion assay, cell-cycle progression, assessed by bromodeossiuridine assay, and apoptotic rate, determined by flow-cytometry analysis of annexin-V binding populations were determined at 48, 72 and 120 hours. Nude mice, injected with HH cells, received ITF2357 (10–20mg/Kg, per os) for 14 days. Micro-PET scan was adopted for disease measurement and treatment response evaluation. Finally, GEP of cell lines exposed to ITF2357 and SAHA were generated to elucidate their mechanisms of action. Results. Cell viability of HH cells treated with ITF2357 ranged from 50% (0.5 mM, at 48 h), to Conclusion. Taken together, these data demonstrate that ITF2357 is effective against PTCLs ex vivo and in vivo, by nominating it for clinical evaluation in this setting.

The PI3K/Akt pathway is a key mediator of proliferation and survival; its constitutive activation is implicated in pathogenesis and progression of a wide variety of hematological malignancies. Constitutively-activated Akt is a common feature of the T-ALL cell lines (MOLT-4, Jurkat, CEM). Hyperactivity of Akt leads not only to their growth and resistance to apoptosis but also to drug-resistance. In this study, we sought to examine the potential of a novel Akt inhibitor, A443654, in the therapy of T-ALL. A443654 led to rapid cell death of CEM, Jurkat, and MOLT-4. All three lines were sensitive to nanomolar (nM) doses of A443654 (IC50=60 nM, 120 nM and 900 nM for MOLT-4, CEM, and Jurkat, respectively). Effects were dose dependent and resulted in G2/M arrest. Indeed, approximately 39% of Jurkat cells treated with A443654 were in G2/M whereas only 11% of the untreated cells were in G2/M. Cell cycle arrest was followed by apoptotic cell death as determined by annexin V-PI and trypan blue staining. Treatment of CEM and Jurkat cells led to de-phosphorylation of the downstream Akt substrate GSK-3beta. Treatment of Jurkat cells with A443654 resulted in activation of caspase-2, -3, -8, and -9. Apoptotic cell death was greatly reduced by caspase-3 and -9 selective inhibitors. Additionally, A443654 was shown to be highly effective against the drug-resistant cell line CEM-VBL100 (CEM-R), which overexpresses Pgp. This Akt inhibitor initially (1 to 4 hour treatments) decreased Pgp activity, but not protein levels, further documenting a link between Akt and Pgp activity. While CEM-R cells displayed decreased sensitivity to A443654, treatment of CEM-R cells with sub-lethal doses of A443654 for 24 hours, reduced the surface expression of Pgp. Moreover, A443654 synergized with the DNA damaging agent etoposide, a substrate of Ppg, in both drug sensitive and resistant lines. At etoposide concentrations between 25 mM to 100 mM, A443654 enhanced the extent of cell killing from 25% to 45%. We then confirmed the effect of A443654 on human leukemia samples using blasts from 6 patients with T-ALL, all of whom displayed constitutive Akt activation. In a dose dependent fashion, A443654 was able to induce apoptotic cell death of T-ALL blast cells, as indicated by flow cytometric analysis of samples immunostained for active (cleaved) caspase-3. In contrast, this Akt inhibitor was determined to be minimally cytotoxic on normal CD34+ hematopoietic precursor cells isolated from cord blood. Taken together, our findings indicate that the Akt inhibitor, A443654, either alone or in combination with existing drugs, may in the future be a useful therapeutic option for primary and refractory T-ALL displaying activated Akt signaling. Furthermore, this novel Akt inhibitor was effective in suppressing the growth of multidrug resistant ALL cells while having minimal effects on normal hematopoietic precursor cells documenting its poteintial in the treatment of drug resistant leukemias.

The serine/threonine kinase Akt, a downstream effector of phosphatidylinositol 3-kinase (PI3K), is known to play an important role in antiapoptotic signaling and has been implicated in the aggressiveness of a number of different human cancers including acute myelogenous leukemia (AML). In the following study, we have investigated the therapeutic potential of the novel Akt inhibitor, perifosine, on human AML cells. Perifosine is a synthetic alkylphospholipid, a new class of antitumor agents which target the plasma membrane and inhibit signal transduction networks. Perifosine was tested on THP-1 and MV4-11 cell lines, as well as primary leukemia cells. The drug blocked AML cells in G2/M phase of the cell cycle and, at longer incubation times (24 hr), decreased survival and induced cell death by apoptosis, as demonstrated by MTT assays and flow cytometric analysis of annexin V-FITC/propidium iodide stained samples. The IC50 for perifosine with THP-1 cells was 15.8 microM, while MV4-11 cells were more sensitive to the drug, as the IC50 was 2.7 microM. In THP-1 cells, perifosine caused complete Akt dephosphorylation on Ser 473 and Thr 308, without affecting total Akt expression levels. Perifosine treatment also resulted in dephosphorylation of the Akt downstream target p70S6 kinase. Perifosine did not affect phosphorylation and activity of the Akt upstream kinase, PDK1 nor altered formation or equilibrium of mTORC1 and mTORC2 complexes. Perifosine induced activation of apical caspases-2, -8, -9, and of executioner caspases-3, -6-, and -7, as well as cleavage of PARP and Bid. In THP-1 cells, the proapoptotic effect of perifosine was partly dependent on Fas/FasL interactions, as blocking antibodies to either Fas or FasL significantly reduced perifosine mediated cytotoxicity. Perifosine also activated JNK, and a JNK selective inhibitor (SP600125) markedly reduced perifosine-dependent apoptosis. In MV4-11 cells, perifosine downregulated phosphorylated Akt, but not phosphorylated FLT3. Moreover, perifosine was cytotoxic for AML blasts with activated Akt (IC50 range: 5.6–7.8 microM). Perifosine also reduced the clonogenic activity of CD34+ cells from AML patients displaying constitutive Akt upregulation, but not the clonogenic activity of CD34+ cells from AML patients without Akt activation, or from healthy donors. The inhibitor markedly increased blast cell sensitivity to etoposide. Taken together, our findings indicate that perifosine, either alone or in combination with existing drugs, is a promising therapeutic agent for the treatment of those AML cases characterized by upregulation of the PI3K/Akt survival pathway. Furthermore this novel Akt inhibitor perifosine appeared not to affect normal human hematopoietic stem cells, further documenting its therapeutic potential.

Myelodysplastic syndromes (MDS) comprise a heterogeneous group of clonal stem cell disorders characterized by ineffective and inadequate hematopoesis. Early stages of MDS display an increased apoptosis, while later stages of MDS present an excessive survival and decreased apoptosis of progressing abnormal clonal cells. The identification of the signaling pathways responsible for increased survival of MDS cells is of high importance as they might represent promising targets for novel forms of therapy aimed at preventing MDS evolution in to acute myeloid leukaemia (AML). However, to date, very limited information is available on survival pathways activated in MDS patients. The phosphatidylinositol 3-kinase (PI3K)/Akt signalling pathway has been implicated in the aggressiveness of a number of different human cancers, and constitutive activation of the PI3K/Akt pathway has been shown to be necessary for the survival of AML cells. In this study, we have performed an immunocytochemical and flow cytometric staining analysis, using an antibody to Ser473 phosphorylated-At (p-Akt) recognizing the activated form of the Akt kinase, to evaluate the levels of p-Akt in MDS mononuclear cells from either bone marrow or peripheral bllod. We observed a high Ser473 p-Akt staining in 85 % of the patients (n=22) diagnosed as high risk MDS, whereas mononuclear cells from healthy donors or low risk MDS patients showed very low or absent Ser473 p-Akt staining. Furthermore, high levels of the class I PI3K p110d isoform was consistently observed in MDS samples also demonstrating high levels of p-Akt. PI3K p110d was recently shown to have a higher expression in contrast to other class I PI3K isoforms in AML blasts. Finally, the expression of PTEN was correlated to the elevated levels of Ser473 p-AKT and PI3K p110d detected in myeloid cells. PTEN is a lipid phosphatase having the PI3K downstream product phosphatidylinositol 3,4,5 triphosphate (PIP3) as one of its primary targets, thus negatively regulating Akt activity. We have found that PTEN is expressed in mononuclear cells from high risk MDS patients, albeit with a lower staining intensity when compared with peripheral blood mononuclear cells from healthy donors. These findings identify activated Akt and PI3K p110d as potential survival factors in high risk MDS and could be important as therapeutic targets for innovative strategies to treat MDS patients.

Imatinib mesylate (Novartis Pharma), an inhibitor of the bcr/abl tyrosine kinase, has rapidly become the first-line therapy for CML. Imatinib has proved remarkably effective at reducing the number of leukaemia cells in individual CML patients and promises to prolong life substantially in comparison with earlier treatments. However, in patients in advanced phases of the disease, the development of resistance to this drug is a frequent setback. Therefore, new inhibitors of bcr/abl are needed. Very recently, a new bcr/abl inhibitor, AMN107 (Novartis Pharma), has been developed. We have tested AMN107 on human leukaemia cell lines and on blasts isolated from imatinib-resistant CML patients. After a 24 h incubation, AMN107 (10 nM) blocked K562 cells in the G1 phase of the cell cycle. To obtain the same effect with imatinib, a 200 nM concentration was required. AMN107 had no affect on cell cycle progression of bcr/abl-negative cell lines such as HL60 and NB4, even if the concentration was raised to 500 nM. After 48 h incubation, AMN107 (10 nM) was capable of inducing a massive apoptosis of K562 cells whereas, once again, 200 nM imatinib was required to obtain the same effect. Western blot analysis with phosphospecific antibodies revealed that in K562 cells AMN107 (50 nM) markedly down-regulated autophosphorylation of bcr/abl Tyr177 and Tyr412, whereas autophosphorylation of Thr735 was unaffected. In contrast, imatinib even if used at 200 nM, did not diminish phosphorylation of either bcr/abl Tyr177 or Tyr412. This finding seems particularly important because recent evidence has demonstrated that the signalling pathway emanating from Tyr177 plays a major role in the pathogenesis of CML. Indeed, phosphorylated Tyr177 forms a high-affinity binding site for the SH2 domain of the adapter Grb2. The main effectors of Grb2 are Sos and Ras, however Grb2 also recruits the scaffolding adapter protein Gab2 to bcr/abl via a Grb2-Gab2 complex, which results in activation of phosphoinositide 3-kinase (PI3K)/Akt and Erk signalling networks. Consistently, we found by immunoprecipitation decreased levels of bcr/abl-associated Gab2, Grab2, and p85 regulatory subunit of PI3K in AMN107-treated cells. AMN107 treatment of K562 cells also caused a reduction of STAT5, cCBL, CRKL, and Akt phosphorylation levels, as well as Bcl-XL expression. AMN107 (5 μM for 24h) significantly increased the apoptosis rate of CML blasts isolated from patients resistant to imatinib. Therefore, AMN107 might represent a new bcr/abl selective inhibitor useful for overcoming imatinib resistance.

Imatinib mesylate (STI571), an inhibitor of the bcr/abl tyrosine kinase, is rapidly becoming the first-line therapy for chronic myeloid leukemia (CML). Imatinib has proved remarkably effective at reducing the number of leukemia cells in individual CML patients and promises to prolong life substantially in comparison with earlier treatments. However, the development of resistance to this drug is a frequent setback, particularly in patients in advanced phases of the disease. Therefore, new inhibitors of bcr/abl are needed. Very recently, a new bcr/abl inhibitor, AMN107, has been synthesized. We have tested AMN107 on leukemic cell lines and on blasts isolated from imatinib-resistant CML patients. Western blot analysis with phosphospecific antibodies revealed that in K562 cells AMN107 (10 nM) down-regulated phosphorylation of bcr/abl Tyr177, while the phosphorylation levels of Tyr412 were unaffected. This finding seems particularly important because recent evidence has demonstrated that the signaling pathway emanating from Tyr177 plays a major role in the pathogenesis of CML. Indeed, phosphorylated Tyr 177 forms a high-affinity binding site for the SH2 domain of the adapter protein Grb2. The main effectors of Brb2 are Sos and Ras, however Grb2 also recruits the scaffolding adapter protein Gab2 to bcr/abl via a Grb2,Gab2 complex. Which results in activation of the PI3K/Akt and Erk signalling networks. In contrast, STI571, even if used at 200 nM, did not diminish phosphorylation of bcr/abl Tyr177. At 10 nM AMN107 blocked K562 cells in the G1 phase of the cell cycle. To obtain the same effect with imatinib, a 200 nM concentration was required. AMN107 did not affect cell cycle progression of bcr/abl-negative cell lines such as HL60 and NB4, even if the concentration was raised to 200 nM. AMN107 (5 μM for 24 h) significantly increased apoptosis rate in CML blasts isolated from patients resistant to the same concentration of imatinib. Therefore, AMN107 might represent a new bcr/abl selective inhibitor useful for overcoming imatinib resistance.