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Factors which regulate transcription in immature myeloid cells are of great current interest for the light they may shed upon myeloid differentiation. In the course of screening for transcription factors which interact with the human myeloperoxidase (MPO) promoter we, for the first time, identified and cloned the cDNA and genomic DNA for human HBP1 (HMG-Box containing protein 1), a member of the high mobility group of non-histone chromosomal proteins. HBP1 cDNA was initially cloned from rat brain in 1994, but its presence in human cells or in myeloid tissue had not been described previously. The sequence of human HBP1 cDNA shows 84% overall homology with the rat HBP1 cDNA sequence. We have subsequently cloned the gene, which is present as a single copy, 25 kbp in length. Northern blotting reveals a single 2.6 kb mRNA transcript which is expressed at higher levels in human myeloid and B lymphoid cell lines than in T cell lines tested and is present in several non-myeloid human cell lines. Comparison of the mRNA and genomic sequences reveals the gene to contain 10 exons and 9 introns. The sequence of human HBP1 mRNA contains a single open reading frame, which codes for a protein 514 amino acids in length. The amino acid sequence specified by the coding region shows 95% homology with the rat HBP1 protein. The human protein sequence exhibits a putative DNA-binding domain similar to that seen in rat HBP1 and shows homology with the activation and repressor domains previously demonstrated in the rat protein. We have expressed human HBP1 protein both in vitro and in prokaryotic and eukaryotic cells. The expressed fusion protein binds to a sequence in a functionally important region within the basal human MPO promoter. In transient co-transfection experiments HBP1 enhances MPO promoter activity. Human HBP1 appears to be a novel transcription factor which is likely to play an important role in regulating transcription in developing myeloid cells. [ABSTRACT FROM AUTHOR]

T-cell malignancies, mainly known as T-cell acute lymphoblastic leukemia (T-ALL) and T-cell non-Hodgkin's lymphoma (T-NHL), are aggressive tumors. Although the clinical outcome of the patients has improved dramatically with combination chemotherapy, significant challenges remain, including understanding of the factors that contribute to the malignant behavior of these tumor cells and developing subsequently optimal targeted therapy. Aberrant cell signal transduction is generally involved in tumor progression and drug resistance. This review describes the pathogenetic role of multiple cellular signaling pathways in T-cell malignancies and the potential therapeutic strategies based on the modulation of these key signaling networks. [ABSTRACT FROM AUTHOR]

Sorafenib, a novel drug for metastatic renal cancer, has broad-spectrum activity against multiple tyrosine kinases, including Raf-1, vascular endothelial growth factor receptor and platelet-derived growth factor receptor. However, little is known about its effects on the immune system. In this report, we examine the effects of sorafenib on the proliferation and activation of human peripheral blood T cells, as well as its effects on T-cell-mediated immune response in mice. At concentrations similar to those used in patients, sorafenib inhibited the proliferation of primary human T cells in vitro. At more than 10 microM, sorafenib caused an irrecoverable inhibition of proliferation, even after drug withdrawal. In addition, sorafenib induced T-cell apoptosis at concentrations higher than 10 muM. sorafenib also caused G(0)/G(1) phase arrest, inhibition of CD25 and CD69 expression, interleukin-2 production and LCK phosphorylation in the T cells; all of these effects exhibited dose and time dependence. When tested against contact dermatitis in mice, sorafenib significantly reduced the ear swelling induced by picryl chloride. These findings suggest that sorafenib may cause the loss of T-cell immune response by inducing apoptosis and targeting LCK. This could potentially lead to immunosuppression in patients with cancer. [ABSTRACT FROM AUTHOR]

Myelodysplastic syndrome (MDS) is a clonal hematopoietic stem cell disorder characterized by ineffective hematopoiesis and leukemia progression. Racial differences may exist on clinical pictures and the molecular events leading to MDS, which are heterogeneous. To better define the clinical and cytogenetic features in Chinese patients, a retrospective multicentric study was performed in 508 MDS cases. Compared with Western countries, Chinese patients showed younger age (median: 49 vs 65-73 years), lower percentages of RARS (2.8 vs 6.6-15.3%), and CMML (5.2 vs 11.7-30.6%). Cytogenetically, among 367 cases with evaluable data, abnormal karyotypes were found in 136 cases, including 56 numerical and 80 structural changes. Incidences of single chromosome 5 and 7 abnormalities were lower than those in Western countries (2.2 vs 17.8-42.5%). However, complex cytogenetic aberrations and chromosome translocations were frequently observed and related to poor prognosis. Both multiple chromosome deletions and translocations were detected in advanced subtypes (RAEB and RAEB-T). Analysis of 200 cases revealed a higher incidence of hepatitis-B-virus infection than that in non-MDS population (21.00 vs 9.75%). This study further confirmed: (1) different genetic/environmental backgrounds between Asian and Western MDS populations; (2) a strong predictive value of cytogenetic abnormalities on disease outcome and involvement of genomic instability in leukemia clone development.Leukemia (2005) 19, 767-775. doi:10.1038/sj.leu.2403688 Published online 10 March 2005 [ABSTRACT FROM AUTHOR]

Acute promyelocytic leukemia (APL) is characterized by typical morphological manifestation, t(15;17) translocation and active response to all-trans retinoic acid (ATRA) in the great majority of patients. However, a subset of APL cases may present atypical phenotypic, cytogenetic or molecular features at different stages of the disease. The biological and clinical significance of these features sometimes remains obscure. In this study, 284 APL patients were cytogenetically analyzed and precise diagnosis was performed according to the molecular cytogenetic results. Twenty-six APL patients were identified as having additional, complex and/or variant chromosomal abnormalities at diagnosis or at relapse, 16 of them being further analyzed using fluorescence in situ hybridization (FISH) or chromosome painting (CP). Interestingly, some of these chromosomal aberrations were found to be associated with atypical morphology and/or drug response, indicating a genotype-phenotype correlation. Analysis of the complex karyotype may also allow a better understanding of the levels of cellular origin of the leukemogenesis. Examination of the remission induction and survival data showed that the presence of the additional/complex chromosome abnormalities was related to the prognosis in both primarily diagnosed and relapsed patients in this series. [ABSTRACT FROM AUTHOR]

Myeloperoxidase (MPO) is an important component of the oxidative antibacterial defense system of granulocytes. Mammalian MPO gene expression has been most extensively studied in human and murine cells. Transcription of the human MPO gene appears to begin at a single initiation site and we have recently described the isolation and characterization of the corresponding human MPO promoter. On the other hand, MPO transcripts in murine myeloid cells show several distinct 5'-termini, suggesting the existence of multiple murine MPO promoters. However, significant levels of endogenous murine MPO promoter activity have not been demonstrated heretofore, although several murine MPO enhancers have been described. We now report the identification and preliminary functional characterization of four distinct murine MPO promoters. Sequence comparison of the human and murine MPO promoter regions reveals homologues of three out of four of these murine promoters within the human MPO gene. However, only one of these sites appears to be functionally active in human myeloid cells, possibly because of the interposition of Alu sequences between the putative promoter sites in the human gene. [ABSTRACT FROM AUTHOR]

A letter to the editor is presented in response to the article "Quantitative profiling of codon 816 KIT mutations can aid in the classification of systemic mast cell disease," published online in the April 5, 2007 issue of "Leukemia."

A letter to the editor is presented regarding the application of MassARRAY technique for mutation detection in patients with myeloproliferative disorders.

MicroRNAs (miRs) are involved in tumorigenesis by regulating tumor suppressor genes and/or oncogenes. MiR187 was overexpressed in peripheral T-cell lymphoma, not otherwise specified (PTCL-NOS) and associated with high Ki67 expression, elevated lactate dehydrogenase, advanced International Prognostic Index and poor prognosis of patients. In vitro, ectopic expression of miR187 in T-lymphoma cell lines accelerated tumor cell proliferation, whereas treatment with miR187 inhibitor reduced cell growth. MiR187 downregulated tumor suppressor gene disabled homolog-2 (Dab2), decreased the interaction of Dab2 with adapter protein Grb2, resulting in Ras activation, phosphorylation/activation of extracellular signal-regulated kinase (ERK) and AKT, and subsequent stabilization of MYC oncoprotein. MiR187-overexpressing cells were resistant to chemotherapeutic agents like doxorubicin, cyclophosphamide, cisplatin and gemcitabine, but sensitive to the proteasome inhibitor bortezomib. Bortezomib inhibited T-lymphoma cell proliferation by downregulating miR187, dephosphorylating ERK and AKT and degrading MYC. In a murine xenograft model established with subcutaneous injection of Jurkat cells, bortezomib particularly retarded the growth of miR187-overexpressing tumors, consistent with the downregulation of miR187, Ki67 and MYC expression. Collectively, these findings indicated that miR187 was related to tumor progression in PTCL-NOS through modulating Ras-mediated ERK/AKT/MYC axis. Although potentially oncogenic, miR187 indicated the sensitivity of T-lymphoma cells to bortezomib. Cooperatively targeting ERK and AKT could be a promising clinical strategy in treating MYC-driven lymphoid malignancies. [ABSTRACT FROM AUTHOR]

MicroRNAs (miRs) are involved in tumorigenesis by regulating tumor suppressor genes and/or oncogenes. MiR187 was overexpressed in peripheral T-cell lymphoma, not otherwise specified (PTCL-NOS) and associated with high Ki67 expression, elevated lactate dehydrogenase, advanced International Prognostic Index and poor prognosis of patients. In vitro, ectopic expression of miR187 in T-lymphoma cell lines accelerated tumor cell proliferation, whereas treatment with miR187 inhibitor reduced cell growth. MiR187 downregulated tumor suppressor gene disabled homolog-2 (Dab2), decreased the interaction of Dab2 with adapter protein Grb2, resulting in Ras activation, phosphorylation/activation of extracellular signal-regulated kinase (ERK) and AKT, and subsequent stabilization of MYC oncoprotein. MiR187-overexpressing cells were resistant to chemotherapeutic agents like doxorubicin, cyclophosphamide, cisplatin and gemcitabine, but sensitive to the proteasome inhibitor bortezomib. Bortezomib inhibited T-lymphoma cell proliferation by downregulating miR187, dephosphorylating ERK and AKT and degrading MYC. In a murine xenograft model established with subcutaneous injection of Jurkat cells, bortezomib particularly retarded the growth of miR187-overexpressing tumors, consistent with the downregulation of miR187, Ki67 and MYC expression. Collectively, these findings indicated that miR187 was related to tumor progression in PTCL-NOS through modulating Ras-mediated ERK/AKT/MYC axis. Although potentially oncogenic, miR187 indicated the sensitivity of T-lymphoma cells to bortezomib. Cooperatively targeting ERK and AKT could be a promising clinical strategy in treating MYC-driven lymphoid malignancies. [ABSTRACT FROM AUTHOR]

AML1-ETO fusion gene is generated from chromosomal translocation t(8;21) mainly in acute myeloid leukemia M2 subtype (AML-M2). Its spliced variant transcript, AML1-ETO9a, rapidly induces leukemia in murine model. To evaluate its clinical significance, AML1-ETO9a expression was assessed in 118 patients with t(8;21) AML-M2, using qualitative and nested quantitative reverse transcriptase (RT)–PCR methods. These cases were accordingly divided into the AML1-ETO9a-H group (n=86, positive for qualitative RT–PCR, with higher level of AML1-ETO9a by quantitative RT–PCR) and the AML1-ETO9a-L group (n=32, negative for qualitative RT–PCR, with lower but still detectable level of AML1-ETO9a by quantitative RT–PCR). C-KIT expression was significantly increased in the AML1-ETO9a-H group, as compared with the AML1-ETO9a-L group. Of the 36 patients harboring C-KIT mutations, 32 patients overexpressed AML1-ETO9a (P=0.0209). Clinically, AML1-ETO9a-H patients exhibited significantly elevated white blood cells count, less bone marrow aberrant myelocytes, increased CD56 but decreased CD19 expression (P=0.0451, P=0.0479, P=0.0149 and P=0.0298, respectively). Moreover, AML1-ETO9a overexpression was related to short event-free and overall survival time (P=0.0072 and P=0.0076, respectively). Taken together, these data suggest that AML1-ETO9a is correlated with C-KIT overexpression/mutations and indicates poor disease outcome in t(8;21) AML-M2. [ABSTRACT FROM AUTHOR]

Interactions between inhibitors of the proteasome and histone deacetylases have been examined in human T-leukemia/lymphoma cells both in vitro and in vivo. Co-exposure of cells to bortezomib and suberoylanilide hydroxamic acid (SAHA) synergistically induces T-leukemia/lymphoma cells to undergo apoptosis, consistent with a significant increase in mitochondrial injury and caspase activation. These events are accompanied by inhibition of cyto-protective signaling pathways, including the nuclear factor (NF)-κB, Raf-1/mitogen-induced extracellular kinase (MEK)/extracellular signal-related kinase (ERK) and AKT pathways, and activation of stress-related cascades, including the stress-activated kinases c-jun N-terminal kinase (JNK) and p38 mitogen-activated protein kinase (p38MAPK). Moreover, bortezomib in conjunction with SAHA efficiently induces apoptosis of primary T-leukemia/lymphoma cells and inhibits tumor growth in a murine xenograft model established with subcutaneous injection of Jurkat cells. Taken together, these findings confirm the synergistic anti-tumor effect of the proteasome and histone deacetylase inhibitors, and provide an insight into the future clinical applications of bortezomib–SAHA combining regimen in treating T-cell malignancies.Leukemia (2009) 23, 1507–1514; doi:10.1038/leu.2009.41; published online 12 March 2009 [ABSTRACT FROM AUTHOR]

A letter to the editor is presented on JAK2 mutation and overlapping myeloproliferative and myelodysplastic features in Refractory anemia with ringed sideroblasts.

Twenty cases of patients with relapsed acute promyelocytic leukemia (APL) were entered into this study for evaluating the clinical efficacy and pharmacokinetics of low-dose arsenic trioxide (As2O3). As2O3 was given at a daily dose of 0.08 mg/kg intravenously for 28 days. Pharmacokinetic study was carried out in eight patients. 16/20 (80%) patients achieved CR. The occurrence of some toxic events including gastrointestinal disturbance, facial edema and cardiac toxicity seemed reduced in the low-dose group than those in the standard-dose group. Differentiation changes were observed in peripheral blood, as well as in bone marrow (BM). Pharmacokinetic study showed that the plasma concentration increased soon after administration of As2O3 with the peak values of 1.535-3.424 micromol/l. After infusion, the plasma concentration was around 0.1-0.5 micromol/l. The arsenic concentration of the plasma of BM aspirates 24 h after administration in five patients was close to the level needed for differentiation-inducing effect. The estimated 2-year OS and RFS were 61.55+/-15.79% and 49.11+/-15.09% respectively, with no difference as compared with those in patients treated with conventional dose (P = 0.2865 and 0.7146, respectively). In conclusion, we demonstrated that low-dose As2O3 had the same effect as the conventional dosage and the mechanism of low-dose arsenic seemed to primarily induce differentiation of APL cells. [ABSTRACT FROM AUTHOR]

The aberrant expression of tissue factor (TF) in acute promyelocytic leukemia (APL) cells has been implicated in the pathogenesis of the APL coagulopathy. In this study, we found that in APL patients receiving ATRA or As2O3 treatment, the improvement in hypercoagulobility and hyperfibrinolysis paralleled the correction of plasma fibrinogen level and amelioration of bleeding symptoms. Notably, clinical improvement was also correlated to ATRA/As2O3-induced rapid decrease of membrane procoagulant activity (PCA) and TF contents of APL blasts. Consistent with the in vivo findings, the membrane PCA, TF antigen and its mRNA level within NB4 cells were rapidly down-regulated by 1 microM ATRA or As2O3, while 0.2 microg/ml DNR increased these TF parameters prior to its effect upon apoptosis induction. The down-regulation of TF mRNA by ATRA was partially de novo protein synthesis-dependent and at least partially attributed to a mechanism of destabilizing TF mRNA. On the other hand, in addition to its modulation on mRNA, As2O3 could also induce an accelerated TF protein turnover. These distinct effects were corroborated with the properties of these agents in causing the degradation of PML-RARalpha protein. All three therapeutic agents, however, enhanced the potential of NB4 cells to stimulate the expression of TF and PCA in endothelium. Taken together, our data suggest that the rapid and distinct regulation of TF on APL cells by these therapeutic agents might at least partially contribute to their effects on APL coagulopathy. [ABSTRACT FROM AUTHOR]