Clathrin Assembly Lymphoid Myeloid Leukemia (CALM) Protein: Localization in Endocytic-coated Pits, Interactions with Clathrin, and the Impact of Overexpression on Clathrin-mediated Traffic

The clathrin assembly lymphoid myeloid leukemia (CALM) gene encodes a putative homologue of the clathrin assembly synaptic protein AP180. Hence the biochemical properties, the subcellular localization, and the role in endocytosis of a CALM protein were studied. In vitro binding and coimmunoprecipitation demonstrated that the clathrin heavy chain is the major binding partner of CALM. The bulk of cellular CALM was associated with the membrane fractions of the cell and localized to clathrin-coated areas of the plasma membrane. In the membrane fraction, CALM was present at near stoichiometric amounts relative to clathrin. To perform structure-function analysis of CALM, we engineered chimeric fusion proteins of CALM and its fragments with the green fluorescent protein (GFP). GFP-CALM was targeted to the plasma membrane-coated pits and also found colocalized with clathrin in the Golgi area. High levels of expression of GFP-CALM or its fragments with clathrin-binding activity inhibited the endocytosis of transferrin and epidermal growth factor receptors and altered the steady-state distribution of the mannose-6-phosphate receptor in the cell. In addition, GFP-CALM overexpression caused the loss of clathrin accumulation in the trans-Golgi network area, whereas the localization of the clathrin adaptor protein complex 1 in the trans-Golgi network remained unaffected. The ability of the GFP-tagged fragments of CALM to affect clathrin-mediated processes correlated with the targeting of the fragments to clathrin-coated areas and their clathrin-binding capacities. Clathrin-CALM interaction seems to be regulated by multiple contact interfaces. The C-terminal part of CALM binds clathrin heavy chain, although the full-length protein exhibited maximal ability for interaction. Altogether, the data suggest that CALM is an important component of coated pit internalization machinery, possibly involved in the regulation of clathrin recruitment to the membrane and/or the formation of the coated pit.

Systemic in vivo lentiviral delivery of miR-15a/16 reduces malignancy in the NZB de novo mouse model of chronic lymphocytic leukemia.

Similar to human chronic lymphocytic leukemia (CLL), the de novo New Zealand Black (NZB) mouse model has a genetically determined age-associated increase in malignant B-1 clones and decreased expression of microRNAs miR-15a and miR-16 in B-1 cells. In the present study, lentiviral vectors were employed in vivo to restore miR-15a/16, and both the short-term single injection and long-term multiple injection effects of this delivery were observed in NZB. Control lentivirus without the mir-15a/16 sequence was used for comparison. We found that in vivo lentiviral delivery of mir-15a/16 increased miR-15a/16 expression in cells that were transduced (detected by GFP expression) and in sera when compared with control lentivirus treatment. More importantly, mice treated with the miR-expressing lentivirus had decreased disease. The lentivirus had little systemic toxicity while preferentially targeting B-1 cells. Short-term effects on B-1 cells were direct effects, and only malignant B-1 cells transduced with miR-15a/16 lentivirus had decreased viability. In contrast, long-term studies suggested both direct and indirect effects resulting from miR-15a/16 lentivirus treatment. A decrease in B-1 cells was found in both the transduced and non-transduced populations. Our data support the potential use of systemic lentiviral delivery of miR-15a/16 to ameliorate disease manifestations of CLL.

Monosomal karyotype in acute myeloid leukemia: a better indicator of poor prognosis than a complex karyotype.

PURPOSE: To investigate the prognostic value of various cytogenetic components of a complex karyotype in acute myeloid leukemia (AML). PATIENTS AND METHODS: Cytogenetics and overall survival (OS) were analyzed in 1,975 AML patients age 15 to 60 years. RESULTS: Besides AML with normal cytogenetics (CN) and core binding factor (CBF) abnormalities, we distinguished 733 patients with cytogenetic abnormalities. Among the latter subgroup, loss of a single chromosome (n = 109) conferred negative prognostic impact (4-year OS, 12%; poor outcome). Loss of chromosome 7 was most common, but outcome of AML patients with single monosomy -7 (n = 63; 4-year OS, 13%) and other single autosomal monosomies (n = 46; 4-year OS, 12%) did not differ. Structural chromosomal abnormalities influenced prognosis only in association with a single autosomal monosomy (4-year OS, 4% for very poor v 24% for poor). We derived a monosomal karyotype (MK) as a predictor for very poor prognosis of AML that refers to two or more distinct autosomal chromosome monosomies (n = 116; 4-year OS, 3%) or one single autosomal monosomy in the presence of structural abnormalities (n = 68; 4-year OS, 4%). In direct comparisons, MK provides significantly better prognostic prediction than the traditionally defined complex karyotype, which considers any three or more or five or more clonal cytogenetic abnormalities, and also than various individual specific cytogenetic abnormalities (eg, del[5q], inv[3]/t[3;3]) associated with very poor outcome. CONCLUSION: MK enables (in addition to CN and CBF) the prognostic classification of two new aggregates of cytogenetically abnormal AML, the unfavorable risk MK-negative category (4-year OS, 26% +/- 2%) and the highly unfavorable risk MK-positive category (4-year OS, 4% +/- 1%).

RANKL expression, function, and therapeutic targeting in multiple myeloma and chronic lymphocytic leukemia.

Bone destruction is a prominent feature of multiple myeloma, but conflicting data exist on the expression and pathophysiologic involvement of the bone remodeling ligand RANKL in this disease and the potential therapeutic benefits of its targeted inhibition. Here, we show that RANKL is expressed by primary multiple myeloma and chronic lymphocytic leukemia (CLL) cells, whereas release of soluble RANKL was observed exclusively with multiple myeloma cells and was strongly influenced by posttranscriptional/posttranslational regulation. Signaling via RANKL into multiple myeloma and CLL cells induced release of cytokines involved in disease pathophysiology. Both the effects of RANKL on osteoclastogenesis and cytokine production by malignant cells could be blocked by disruption of RANK-RANKL interaction with denosumab. As we aimed to combine neutralization of RANKL with induction of antibody-dependent cellular cytotoxicity of natural killer (NK) cells against RANKL-expressing malignant cells and as denosumab does not stimulate NK reactivity, we generated RANK-Fc fusion proteins with modified Fc moieties. The latter displayed similar capacity compared with denosumab to neutralize the effects of RANKL on osteoclastogenesis in vitro, but also potently stimulated NK cell reactivity against primary RANKL-expressing malignant B cells, which was dependent on their engineered affinity to CD16. Our findings introduce Fc-optimized RANK-Ig fusion proteins as attractive tools to neutralize the detrimental function of RANKL while at the same time potently stimulating NK cell antitumor immunity.

Impact of HLA A2 and cytomegalovirus serostatus on outcomes in patients with leukemia following matched-sibling myeloablative allogeneic hematopoietic cell transplantation.

BACKGROUND AND OBJECTIVES: Donor cytomegalovirus seropositivity was reported to improve leukemia outcomes in HLA-A2 identical hematopoietic cell transplant (HCT) recipients, due to a possible cross-reactivity of donor HLA-A2-restricted CMV-specific T cells with minor histocompatibility (H) antigen of recipient cells. This study analyzed the role of donor CMV serostatus and HLA-A2 status on leukemia outcomes in a large population of HLA-identical HCT recipients. DESIGN AND METHODS: Leukemia patients transplanted between 1992 and 2003 at the Fred Hutchinson Cancer Research Center were categorized as standard risk [leukemia first remission, chronic myeloid leukemia in chronic phase (CML-CP)] and high risk (advanced disease) patients. Time-to-event analysis was used to evaluate the risk of relapse and death associated with HLA-A2 status and donor CMV serostatus. RESULTS: In standard risk patients, acute leukemia (p<0.001) and sex mismatch (female to male, p=0.004)) independently increased the risk of death, while acute leukemia increased the risk of relapse (p<0.001). In high risk patients acute leukemia (p=0.01), recipient age > or = 40 (p=0.005) and herpes simplex virus (HSV) seropositivity (p<0.001) significantly increased the risk death; HSV seropositivity (p=0.006) increased the risk of relapse. Donor CMV serostatus had no significant effect on mortality or relapse in any HLA group. INTERPRETATION AND CONCLUSION: This epidemiological study did not confirm the previously reported effect of donor CMV serostatus on the outcomes of leukemia in HLA-A2-identical HCT recipients. Addressing the question of cross-reactivity of HLA-A2-restricted CMV-specific T cells with minor H antigens in a clinical study would require knowledge of the patient's minor H antigen genotype. However, because of the unbalanced distribution of HLA-A2-restricted minor H antigens in the population and their incomplete identification, this question might be more appropriately evaluated in in vitro experiments than in a clinical study.

Canonical WNT signaling in hematopoiesis and leukemia

SummaryCanonical Wnt signaling is crucial for embryonic development and the homeostasis of certain adult tissues such as the gut and the skin. The role of canonical Wnt signaling in hematopoiesis is still debated. The expression of a dominant-active β-catenin in hematopoietic stem cells (HSCs) enhances the self-renewal capacity of HSCs but is detrimental for long-term hematopoiesis. In contrast, loss of function experiments show that absence of β- and γ-catenin does not impair steady-state hematopoiesis. It has been argued that the inducible deletion of β-catenin using the IFN-responsive Mx promoter may somehow influence stem cell fate. Herein we used the constitutive deletion of β-catenin specifically in hematopoietic cells to show that the absence of β- catenin, as well as γ-catenin deletion, does not impair normal hematopoiesis and self-renewal capacity of HSCs.Dysregulation of canonical Wnt signaling is causal for several types of cancer, including colon carcinoma or breast cancer. Recently, it was found that Wnt signal transduction was upregulated in certain leukemias. Based on these data, we have investigated whether β- and γ-catenin play a role for the induction of leukemias by oncogenic BCR-ABL translocation product. We show that the induction of B-ALL (B cell acute lymphocytic leukemia) is strongly reduced in the absence of γ-catenin, while the induction of CML (chronic myeloid leukemia) occurs at a normal rate. In the combined absence of β- and γ-catenin the induction of both CML and B-ALL is essentially blocked. Consistent with these data others have found that β-catenin is essential for the induction of CML by BCR-ABL.Collectively, we find that β- and γ-catenin are dispensable for normal hematopoiesis but essential for the development of BCR-ABL induced leukemias. These findings suggest that the canonical Wnt pathway may represent a promising target for the therapy of leukemia.RésuméLa voie de signalisation canonique Wnt est essentielle pour le développement embryonnaire ainsi que l'homéostasie de certains tissus adultes, comme les intestins et la peau. Le rôle de la voie canonique Wnt pour l'hématopoïèse est encore incertain. D'un coté l'expression d'une forme active de β-catenine dans les cellules souches de la moelle augmente leur potentiel d'auto- renouvellement mais est préjudiciable pour l'hématopoïèse à long terme. Par contre, l'absence de β- et γ-catenine n'empêche pas le déroulement normal de l'hématopoïèse. La façon dont est supprimée β-catenine, en utilisant le promoteur IFN-inductible Mx, pourrait influencer le sort des cellules souches. Ici nous détruisons β-catenine spécifiquement dans les cellules hématopoïétiques de manière constitutive et montrons que, en combinaison avec l'absence de γ-catenine, l'absence de β-catenine n'affecte pas le déroulement normal de l'hématopoïèse et la capacité des cellules souches de la moelle à se renouveler.Plusieurs sortes de cancers, comme celui du colon ou du sein, sont parfois dus à une dérégulation de la voie canonique Wnt. Récemment, certaines leucémies ont présenté une activation du signal Wnt. A partir de ces données, nous avons examiné si β- et γ-catenine jouent un rôle dans l'induction des leucémies causées par le produit de translocation BCR-ABL. Nous avons montré que l'induction de la leucémie aiguë lymphoïde de cellules Β (LAL-B) est grandement diminuée en l'absence de γ-catenin, alors que l'induction de la leucémie myéloïde chronique (LMC) n'est pas affectée. En l'absence des deux catenines, l'induction des deux leucémies LAL-B et LMC est presque complètement bloquée. En confirmation de nos données, un autre groupe a montré que β-catenine est essentielle pour le développement de la LMC. Ensemble, ces données nous montrent que β- et γ-catenine ne sont pas nécessaires pour l'hématopoïèse normale, mais essentielle pour le développement des leucémies induites par BCR-ABL. Cela suggère que la voie de signalisation canonique Wnt est une cible prometteuse pour de futures thérapies.

Receptor activator for NF-κB ligand in acute myeloid leukemia: expression, function, and modulation of NK cell immunosurveillance.

The TNF family member receptor activator for NF-κB ligand (RANKL) and its receptors RANK and osteoprotegerin are key regulators of bone remodeling but also influence cellular functions of tumor and immune effector cells. In this work, we studied the involvement of RANK-RANKL interaction in NK cell-mediated immunosurveillance of acute myeloid leukemia (AML). Substantial levels of RANKL were found to be expressed on leukemia cells in 53 of 78 (68%) investigated patients. Signaling via RANKL into the leukemia cells stimulated their metabolic activity and induced the release of cytokines involved in AML pathophysiology. In addition, the immunomodulatory factors released by AML cells upon RANKL signaling impaired the anti-leukemia reactivity of NK cells and induced RANK expression, and NK cells of AML patients displayed significantly upregulated RANK expression compared with healthy controls. Treatment of AML cells with the clinically available RANKL Ab Denosumab resulted in enhanced NK cell anti-leukemia reactivity. This was due to both blockade of the release of NK-inhibitory factors by AML cells and prevention of RANK signaling into NK cells. The latter was found to directly impair NK anti-leukemia reactivity with a more pronounced effect on IFN-γ production compared with cytotoxicity. Together, our data unravel a previously unknown function of the RANK-RANKL molecule system in AML pathophysiology as well as NK cell function and suggest that neutralization of RANKL with therapeutic Abs may serve to reinforce NK cell reactivity in leukemia patients.

Population pharmacokinetics in chronic myeloid leukaemia patients: observations under field-conditions

Introduction: Therapeutic drug monitoring (TDM) of imatinib has been increasingly proposed for chronic myeloid leukaemia (CML) patients, as several studies have found a correlation between trough concentrations (Cmin) >=1000ng/ml and improved response. The pharmacological monitoring project of EUTOS (European Treatment and Outcome Study) was launched to increase the availability of imatinib TDM, standardize labs, and validate proposed Cmin thresholds. Using the collected data, the objective of this analysis was to characterize imatinib Population pharmacokinetics (Pop-PK) in a large cohort of European patients, to quantify its variability and the influence of demographic factors and comedications, and to derive individual exposure variables suitable for further concentration-effect analyses.¦Methods: 4095 PK samples from 2478 adult patients were analyzed between 2006 and 2010 by LC-MS-MS and considered for Pop-PK analysis by NONMEM®. Model building used data from 973 patients with >=2 samples available (2590 samples). A sensitivity analysis was performed using all data. Available comedications (27%) were classified into inducers or inhibitors of P-glycoprotein, CYP3A4/5 and organic-cation-transporter-1 (hOCT-1).¦Results: A one-compartment model with linear elimination, zero-order absorption fitted the data best. Estimated Pop-PK parameters (interindividual variability, IIV %CV) for a 40-year old male patient were: clearance CL = 17.3 L/h (37.7%), volume V = 429L (51.1%), duration of absorption D1 = 3.2h. Outliers, reflecting potential compliance and time recording errors, were taken into account by estimating an IIV on the residual error (35.4%). Intra-individual residuals were 29.1% (proportional) plus ± 84.6 ng/mL (additive). Female patients had a 15.2% lower CL (14.6 L/h). A piece-wise linear effect of age estimated a CL of 18.7 L/h at 20 years, 17.3 L/h at 40 and 13.8 L/h at 60 years. These covariates explained 2% (CL) and 4.5% (V) of IIV variability. No effect of comedication was found. The sensitivity analysis expectedly estimated increased IIV, but similar fixed effect parameters.¦Conclusion: Imatinib PK was well described in a large cohort of CML patients under field conditions and results were concordant with previous studies. Patient characteristics explain only little IIV, confirming limited utility of prior dosage adjustment. As intra-variability is smaller than inter-patient variability, dose adjustment guided by TDM could however be beneficial in order to bring Cmin into a given therapeutic target.

In situ RHAMM protein expression in acute myeloid leukemia blasts suggests poor overall survival.

Treatment options for patients with high-risk acute myeloid leukemia (AML) include high-dose chemotherapy regimens in combination with allogeneic hematopoietic stem cell transplantation, which takes advantage of the donor T-cell-mediated graft-versus-leukemia effect. Together with beneficial responses observed in assays targeted at leukemia-associated antigens (LAA), this encouraged research on cancer vaccines and adoptive cellular therapies in AML. The receptor for hyaluronic acid-mediated motility (RHAMM, CD168) was identified as one of the most promising LAA in AML. Thus far, little is known about in situ expression in leukemic bone marrow blasts or the prognostic role of RHAMM and its interaction partners in AML. We immunohistochemically analyzed the expression and prognostic significance of RHAMM on trephine bone marrow biopsies from 71 AML cases that had been evaluated for cytogenetics and presence of FLT3-internal tandem duplications and NPM1 mutations. Fifty-five patients (77%) were treated with curative intent, while 16 (23%) received the most appropriate supportive care. Twenty of 71 (28%) AML cases were considered RHAMM+. Receiver operating characteristic curves showed significant discriminatory power considering overall survival (OS) in AML patients treated curatively for RHAMM (p = 0.015). Multivariable analysis revealed that expression of RHAMM in >5% of leukemic blasts identifies a subgroup of curatively treated cases with adverse OS independent of failures to achieve complete remission. RHAMM not only represents a promising LAA with specific T-cell responses in AML but, if assessed in situ on blasts, also a probable prognostic factor.

Azacytidine for acute myeloid leukemia in elderly or frail patients: a phase II trial (SAKK 30/07).

Abstract This phase II trial treated elderly or frail patients with acute myeloid leukemia (AML) with single-agent subcutaneous azacytidine at 100 mg/m(2), on 5 of 28 days for up to six cycles. Treatment was stopped for lack of response, or continued to progression in responders. The primary endpoint was response within 6 months. A response rate ≥ 34% was considered a positive trial outcome. From September 2008 to April 2010, 45 patients from 10 centers (median age 74 [55-86] years) were accrued. Patients received four (1-21) cycles. Best response was complete response/complete response with incomplete recovery of neutrophils and/or platelets (CR/CRi) in eight (18%; 95% confidence interval [CI]: 8-32%.), 0 (0%) partial response (PR), seven (16%) hematologic improvement, 17 (38%) stable disease. Three non-responding patients stopped treatment after six cycles, 31 patients stopped early and 11 patients continued treatment for 8-21 cycles. Adverse events (grade ≥ III) were infections (n = 13), febrile neutropenia (n = 8), thrombocytopenia (n = 7), dyspnea (p = 6), bleeding (n = 5) and anemia (n = 4). Median overall survival was 6 months. Peripheral blood blast counts, grouped at 30%, had a borderline significant association with response (p = 0.07). This modified azacytidine schedule is feasible for elderly or frail patients with AML in an outpatient setting with moderate, mainly hematologic, toxicity and response in a proportion of patients, although the primary objective was not reached.

G-CSF-induced remission in two cases of acute myeloid leukemia.

We report on two elderly patients with newly diagnosed acute myeloid leukemia (AML) who were treated in palliative intention because of comorbidities and intermediate or poor risk cytogenetics. Both received G-CSF to reduce the risk of infection related to neutropenia. Interestingly, one patient achieved a full hematological remission and the other a peripheral remission with dramatic reduction of the bone marrow blast count. Although a direct therapeutic effect of myeloid growth factors seems to be unusual in AML, the use of G-CSF or GM-CSF may be recommended in patients such as elderly patients who are not suited for intensive chemotherapy.

Neutralization of (NK-cell-derived) B-cell activating factor by Belimumab restores sensitivity of chronic lymphoid leukemia cells to direct and Rituximab-induced NK lysis.

Natural killer (NK) cells are cytotoxic lymphocytes that substantially contribute to the therapeutic benefit of antitumor antibodies like Rituximab, a crucial component in the treatment of B-cell malignancies. In chronic lymphocytic leukemia (CLL), the ability of NK cells to lyse the malignant cells and to mediate antibody-dependent cellular cytotoxicity upon Fc receptor stimulation is compromised, but the underlying mechanisms are largely unclear. We report here that NK-cells activation-dependently produce the tumor necrosis factor family member 'B-cell activating factor' (BAFF) in soluble form with no detectable surface expression, also in response to Fc receptor triggering by therapeutic CD20-antibodies. BAFF in turn enhanced the metabolic activity of primary CLL cells and impaired direct and Rituximab-induced lysis of CLL cells without affecting NK reactivity per se. The neutralizing BAFF antibody Belimumab, which is approved for treatment of systemic lupus erythematosus, prevented the effects of BAFF on the metabolism of CLL cells and restored their susceptibility to direct and Rituximab-induced NK-cell killing in allogeneic and autologous experimental systems. Our findings unravel the involvement of BAFF in the resistance of CLL cells to NK-cell antitumor immunity and Rituximab treatment and point to a benefit of combinatory approaches employing BAFF-neutralizing drugs in B-cell malignancies.