The t(8;21) chromosomal translocation in acute myelogenous leukemia modifies intranuclear targeting of the AML1/CBFα2 transcription factor

Targeting of gene regulatory factors to specific intranuclear sites may be critical for the accurate control of gene expression. The acute myelogenous leukemia 8;21 (AML1/ETO) fusion protein is encoded by a rearranged gene created by the ETO chromosomal translocation. This protein lacks the nuclear matrix-targeting signal that directs the AML1 protein to appropriate gene regulatory sites within the nucleus. Here we report that substitution of the chromosome 8-derived ETO protein for the multifunctional C terminus of AML1 precludes targeting of the factor to AML1 subnuclear domains. Instead, the AML1/ETO fusion protein is redirected by the ETO component to alternate nuclear matrix-associated foci. Our results link the ETO chromosomal translocation in AML with modifications in the intranuclear trafficking of the key hematopoietic regulatory factor, AML1. We conclude that misrouting of gene regulatory factors as a consequence of chromosomal translocations is an important characteristic of acute leukemias.

A bcr-3 isoform of RARα-PML potentiates the development of PML-RARα-driven acute promyelocytic leukemia

Acute promyelocytic leukemia (APML) most often is associated with the balanced reciprocal translocation t(15;17) (q22;q11.2) and the expression of both the PML-RARα and RARα-PML fusion cDNAs that are formed by this translocation. In this report, we investigated the biological role of a bcr-3 isoform of RARα-PML for the development of APML in a transgenic mouse model. Expression of RARα-PML alone in the early myeloid cells of transgenic mice did not alter myeloid development or cause APML, but its expression significantly increased the penetrance of APML in mice expressing a bcr-1 isoform of PML-RARα (15% of animals developed APML with PML-RARα alone vs. 57% with both transgenes, P < 0.001). The latency of APML development was not altered substantially by the expression of RARα-PML, suggesting that it does not behave as a classical “second hit” for development of the disease. Leukemias that arose from doubly transgenic mice were less mature than those from PML-RARα transgenic mice, but they both responded to all-trans retinoic acid in vitro. These findings suggest that PML-RARα drives the development of APML and defines its basic phenotype, whereas RARα-PML potentiates this phenotype via mechanisms that are not yet understood.

The TEL/platelet-derived growth factor β receptor (PDGFβR) fusion in chronic myelomonocytic leukemia is a transforming protein that self-associates and activates PDGFβR kinase-dependent signaling pathways

The TEL/PDGFβR fusion protein is the product of the t(5;12) translocation in patients with chronic myelomonocytic leukemia. The TEL/PDGFβR is an unusual fusion of a putative transcription factor, TEL, to a receptor tyrosine kinase. The translocation fuses the amino terminus of TEL, containing the helix-loop-helix (HLH) domain, to the transmembrane and cytoplasmic domain of the PDGFβR. We hypothesized that TEL/PDGFβR self-association, mediated by the HLH domain of TEL, would lead to constitutive activation of the PDGFβR tyrosine kinase domain and cellular transformation. Analysis of in vitro-translated TEL/PDGFβR confirmed that the protein self-associated and that self-association was abrogated by deletion of 51 aa within the TEL HLH domain. In vivo, TEL/PDGFβR was detected as a 100-kDa protein that was constitutively phosphorylated on tyrosine and transformed the murine hematopoietic cell line Ba/F3 to interleukin 3 growth factor independence. Transformation of Ba/F3 cells required the HLH domain of TEL and the kinase activity of the PDGFβR portion of the fusion protein. Immunoblotting demonstrated that TEL/PDGFβR associated with multiple signaling molecules known to associate with the activated PDGFβR, including phospholipase C γ1, SHP2, and phosphoinositol-3-kinase. TEL/PDGFβR is a novel transforming protein that self-associates and activates PDGFβR-dependent signaling pathways. Oligomerization of TEL/PDGFβR that is dependent on the TEL HLH domain provides further evidence that the HLH domain, highly conserved among ETS family members, is a self-association motif.

The human formin-binding protein 17 (FBP17) interacts with sorting nexin, SNX2, and is an MLL-fusion partner in acute myelogeneous leukemia

We have cloned a fusion partner of the MLL gene at 11q23 and identified it as the gene encoding the human formin-binding protein 17, FBP17. It maps to chromosome 9q34 centromeric to ABL. The gene fusion results from a complex chromosome rearrangement that was resolved by fluorescence in situ hybridization with various probes on chromosomes 9 and 11 as an ins(11;9)(q23;q34)inv(11)(q13q23). The rearrangement resulted in a 5′-MLL/FBP17-3′ fusion mRNA. We retrovirally transduced murine-myeloid progenitor cells with MLL/FBP17 to test its transforming ability. In contrast to MLL/ENL, MLL/ELL and other MLL-fusion genes, MLL/FBP17 did not give a positive readout in a serial replating assay. Therefore, we assume that additional cooperating genetic abnormalities might be needed to establish a full malignant phenotype. FBP17 consists of a C-terminal Src homology 3 domain and an N-terminal region that is homologous to the cell division cycle protein, cdc15, a regulator of the actin cytoskeleton in Schizosaccharomyces pombe. Both domains are separated by a consensus Rho-binding motif that has been identified in different Rho-interaction partners such as Rhotekin and Rhophilin. We evaluated whether FBP17 and members of the Rho family interact in vivo with a yeast two-hybrid assay. None of the various Rho proteins tested, however, interacted with FBP17. We screened a human kidney library and identified a sorting nexin, SNX2, as a protein interaction partner of FBP17. These data provide a link between the epidermal growth factor receptor pathway and an MLL fusion protein.

Abr and Bcr are multifunctional regulators of the Rho GTP-binding protein family.

Philadelphia chromosome-positive leukemias result from the fusion of the BCR and ABL genes, which generates a functional chimeric molecule. The Abr protein is very similar to Bcr but lacks a structural domain which may influence its biological regulatory capabilities. Both Abr and Bcr have a GTPase-activating protein (GAP) domain similar to those found in other proteins that stimulate GTP hydrolysis by members of the Rho family of GTP-binding proteins, as well as a region of homology with the guanine nucleotide dissociation-stimulating domain of the DBL oncogene product. We purified as recombinant fusion proteins the GAP- and Dbl-homology domains of both Abr and Bcr. The Dbl-homology domains of Bcr and Abr were active in stimulating GTP binding to CDC42Hs, RhoA, Rac1, and Rac2 (rank order, CDC42Hs > RhoA > Rac1 = Rac2) but were inactive toward Rap1A and Ha-Ras. Both Bcr and Abr acted as GAPs for Rac1, Rac2, and CDC42Hs but were inactive toward RhoA, Rap1A, and Ha-Ras. Each individual domain bound in a noncompetitive manner to GTP-binding protein substrates. These data suggest the multifunctional Bcr and Abr proteins might interact simultaneously and/or sequentially with members of the Rho family to regulate and coordinate cellular signaling.

Cell cycle-related shifts in subcellular localization of BCR: association with mitotic chromosomes and with heterochromatin.

The disruption of the BCR gene and its juxtaposition to and consequent activation of the ABL gene has been implicated as the critical molecular defect in Philadelphia chromosome-positive leukemias. The normal BCR protein is a multifunctional molecule with domains that suggest its participation in phosphokinase and GTP-binding pathways. Taken together with its localization to the cytoplasm of uncycled cells, it is therefore presumed to be involved in cytoplasmic signaling. By performing a double aphidicolin block for cell cycle synchronization, we currently demonstrate that the subcellular localization of BCR shifts from being largely cytoplasmic in interphase cells to being predominantly perichromosomal in mitosis. Furthermore, with the use of immunogold labeling and electron microscopy, association of BCR with DNA, in particular heterochromatin, can be demonstrated even in quiescent cells. Results were similar in cell lines of lymphoid or myeloid origin. These observations suggest a role for BCR in the phosphokinase interactions linked to condensed chromatin, a network previously implicated in cell cycle regulation.

Interferon-α-2b and oral cytarabine ocfosfate for newly diagnosed chronic myeloid leukaemia

Background: Treatment with interferon and subcutaneous cytarabine produces superior cytogenetic responses in chronic myeloid leukaemia (CML) than treatment with interferon alone, but at the expense of greater toxicity. Cytarabine ocfosfate (YNK01) is an oral precursor of cytarabine that may overcome some of the inconvenience and toxicities associated with subcutaneous cytarabine administration. Patients and methods: We studied the efficacy and tolerability of combination therapy with interferon-alpha-2b and YNK01 in patients with newly diagnosed, untreated CML. Forty patients were treated with interferon-alpha-2b (5 MU/m(2)/day) plus monthly courses of YNK01 (600 mg/day for 10 days) for I year. Results: The 6-month complete haematological response rate was 63% and the 1-year major cytogenetic response rate was 30%, with 10% of cytogenetic responses being complete. With a median follow-up of 57 months, the estimated 5-year overall survival was 86% (95% confidence interval 70% to 94%). Treatment tolerability was poor, with toxicity leading to discontinuation of one or both drugs in 60% of cases. The median daily dose of interferon alpha-2b was 7.75 MU and the median dose of YNK01 was 600 mg/day for each 10-day treatment cycle. Conclusions: Interferon-alpha-2b and YNK01 produce cytogenetic responses comparable to those achieved with interferon-alpha-2b and parenteral cytarabine, although toxicity was excessive. Alternate dosing strategies may enhance the tolerability of YNK01.

Loss of PKR Activity in Chronic Lymphocytic Leukemia

There are a number of observations that suggest the dsRNA-activated protein kinase, PKR, may play an active role in formation and maintenance of leukemia, including nonrandom chromosomal deletions in acute leukemia as well as truncations and deletions of the PKR gene in some leukemia cell lines. However, there is little direct evidence from patient material that this is so. Here we show that full-length PKR is present but not active in 21 of 28 patient samples from B-cell chronic lymphocytic leukemia (B-CLL). PKR from these patients was unable to auto-activate or phosphorylate substrates but was able to bind dsRNA. Furthermore, the lack of PKR activation was not due to differing levels of the PKR activator, PACT nor of the PKR inhibitor, p58(IPK). We compared PKR status with clinical parameters and disease staging. No differences were found between the 2 groups in terms of staging (modified Rai or Binet), age, CD38 status, p53 status, 11q23 deletion status or CEP12 deletion status. However, there was a significant correlation between deletion in 13q14.3 and lack of PKR activity. We show that B-CLL cells appear to contain a soluble inhibitor of PKR, as lysates from cells lacking PKR activity were able to inhibit exogenous PKR in mixing experiments. Finally, we show suppression of PKR activity was still present following ultrafilitration through a 10,000 Da cutoff filter but was lost upon extraction with phenol/chloroform or by high salt washing. This data suggests loss of PKR activity may contribute to the formation and/or maintenance of CLL. (C) 2004 Wiley-Liss, Inc.

A systematic review of the adverse events of imatinib mesylate in the treatment of chronic myeloid leukemia.

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HIV, cardiovascular diseases, and chronic arsenic exposure co-exist in a positive synergy

Recent epidemiological evidences indicate that arsenic exposure increases risk of atherosclerosis, cardio vascular diseases (CVD) such as hypertension, atherosclerosis, coronary artery disease (CAD) and microangiopathies in addition to the serious global health concern related to its carcinogenic effects. In experiments on animals, acute and chronic exposure to arsenic directly correlates with cardiac tachyarrhythmia, and atherogenesis in a concentration and duration dependent manner. Moreover, the other effects of long-term arsenic exposure include induction of non-insulin dependent diabetes by mechanisms yet to be understood. On the other hand, there are controversial issues, gaps in knowledge, and future research priorities in accelerated incidences of CVD and mortalities in patients with HIV who are under long-termanti-retroviral therapy (ART). Although, both HIV infection itself and various components of ART initiate significant pathological alterations in the myocardium and the vasculature, simultaneous environmental exposure to arsenic which is more convincingly being recognized as a facilitator of HIV viral cycling in the infected immune cells, may contribute an additional layer of adversity in these patients. A high degree of suspicion and early screening may allow appropriate interventional guidelines to improve the quality of lives of those affected. In this mini-review which have been fortified with our own preliminary data, we will discuss some of the key current understating of chronic arsenic exposure, and its possible impact on the accelerated HIV/ART induced CVD. The review will conclude with notes on recent developments in mathematical modeling in this field that probabilistically forecast incidence prevalence as functions of aging and life style parameters, most of which vary with time themselves; this interdisciplinary approach provides a complementary kernel to conventional biology.

Chronic smartphone gaming consumption and positive coping practice

Purpose - Chronic consumption practice has been greatly accelerated by mobile, interactive and smartphone gaming technology devices. This study explores how chronic consumption of smartphone gaming produces positive coping practice. Design/methodology/approach - Underpinned by cognitive framing theory, empirical insights from eleven focus groups (n=62) reveal how smartphone gaming enhances positive coping amongst gamers and non-gamers. Findings - The findings reveal how the chronic consumption of games allows technology to act with privileged agency that resolves tensions between individuals and collectives. Consumption narratives of smartphone games, even when play is limited, lead to the identification of three cognitive frames through which positive coping processes operate: (a) the market generated frame, (b) the social being frame, and (c) the citizen frame. Research limitations/implications – This paper adds to previous research by providing an understanding of positive coping practice in the smartphone chronic gaming consumption. Originality/value - In smartphone chronic gaming consumption, cognitive frames enable positive coping by fostering appraisal capacities in which individuals confront, hegemony, culture and alterity-morality concerns. 

Mutational Status of the TP53 Gene As a Predictor of Response and Survival in Patients With Chronic Lymphocytic Leukemia: Results From the LRF CLL4 Trial

PurposeTP53 mutations have been described in chronic lymphocytic leukemia (CLL) and have been associated with poor prognosis in retrospective studies. We aimed to address the frequency and prognostic value of TP53 abnormalities in patients with CLL in the context of a prospective randomized trial.Patients and MethodsWe analyzed 529 CLL samples from the LRF CLL4 (Leukaemia Research Foundation Chronic Lymphocytic Leukemia 4) trial (chlorambucil v fludarabine with or without cyclophosphamide) at the time of random assignment for mutations in the TP53 gene. TP53 mutation status was correlated with response and survival data.ResultsMutations of TP53 were found in 40 patients (7.6%), including 25 (76%) of 33 with 17p deletion and 13 (3%) of 487 without that deletion. There was no significant correlation between TP53 mutations and age, stage, IGHV gene mutations, CD38 and ZAP-70 expression, or any other chromosomal abnormality other than 17p deletion, in which concordance was high (96%). TP53 mutations were significantly associated with poorer overall response rates (27% v 83%; P <.001) and shorter progression-free survival (PFS) and overall survival (OS; 5-year PFS: 5% v 17%; 5-year OS: 20% v 59%; P <.001 for both). Multivariate analysis that included baseline clinical variables, treatment, and known adverse genetic factors confirmed that TP53 mutations have added prognostic value.ConclusionTP53 mutations are associated with impaired response and shorter survival in patients with CLL. Analysis of TP53 mutations should be performed in patients with CLL who have progressive disease before starting first-line treatment, and those with mutations should be selected for novel experimental therapies. J Clin Oncol 29: 2223-2229. (C) 2011 by American Society of Clinical Oncology

Two new 3' PML breakpoints in t(15;17)(q22;q21)-positive acute promyelocytic leukemia.

In the present article, two new types of PML/RARA junctions are described. Both were identified in diagnostic samples from two t(15;17)(q22;q21)-positive acute promyelocytic leukemia (APL) patients who failed to achieve complete remission. By using different sets of primers, reverse transcriptase polymerase chain reaction (RT-PCR) of PML/RARA junctions showed atypical larger bands compared with those generated from the three classical PML breakpoints already described. Sequence analysis of the fusion region of the amplified cDNAs allowed us to determine the specificity of these fragments in both patients. This analysis showed two new hybrid transcripts that were 53 and 306 base pairs (bp) longer than that expressed by the NB4 cell line (PML breakpoint within intron 6), and are the result of the direct joining of RARA exon 3 with PML exon 7a (patient 2) or the 5' portion of PML exon 7b (patient 1), respectively. In patient 1, RT-PCR analysis of the reciprocal RARA/PML junction showed a smaller transcript than that expected in bcr1 cases, while in patient 2 no amplified fragment was obtained. Cytogenetic analysis and/or fluorescence in situ hybridization (FISH) showed that both patients had the t(15;17) translocation. The clinical and hematological profiles expressed by the two patients carrying these unexpected types of PML/RARA rearrangement did not differ significantly from that commonly seen in other APLs with the exception of the poor outcome. Genes Chromosomes Cancer 27:35-43, 2000.