Inhibition of apoptosis by BCR-ABL in chronic myeloid leukemia

BCR-ABL expression is presumed to effect clonal expansion in chronic myeloid leukemia (CML) by deregulation of cell proliferation. However, most studies have found that relative rates of cell proliferation are not increased in CML. Moreover, we found that CML progenitors display a normal proliferative response to growth factors and do not manifest greater proliferative potential than normal progenitors. Growth of malignancies depends on an imbalance between the rate of cell production and the rate of cell death. We found that BCR-ABL expression inappropriately prolongs the growth factor-independent survival of CML myeloid progenitors and granulocytes by inhibiting apoptosis, a genetically programmed process of active cell death; inhibition of BCR- ABL expression by antisense oligonucleotides reversed the suppression of apoptosis as well as the enhancement of survival. The decreased rate of programmed cell death appears to be the primary mechanism by which BCR-ABL effects expansion of the leukemic clone in CML.     

CYP1B1基因敲除对成年小鼠肝脏脂肪代谢的影响及可能机制

目的探讨CYP1B1对高脂膳食诱导的成年小鼠脂肪代谢的作用。方法 CYP1B1基因敲除(KO)和野生型(WT)雄性成年C57/BL小鼠(6 w龄)各16只,给予低脂(LFD,30%)、高脂肪(HFD,60%)饲料共6 w。小鼠处死后取血清、附睾脂肪和肝脏组织检测相应的生化和分子生物学指标。结果 6 w高脂膳食后,KO小鼠能量摄入总量稍高于WT小鼠,但其体重增量和附睾脂肪组织重量均显著低于WT小鼠;WT小鼠脂肪细胞直径明显大于KO小鼠,且血糖、血清及肝脏组织中甘油三酯(TG)水平亦明显高于KO小鼠;肝脏组织RT-PCR结果显示,CYP1B1基因敲除后,启动脂肪形成的核因子及脂肪合成相关基因如CD36、SREBP1c、SCD1等表达下降,而调控脂肪氧化分解的基因如CPT-1α,UCP-2表达显著上升;蛋白印迹结果显示,CYP1B1基因敲除增强腺苷-磷酸激酶(AMPK)的磷酸化。结论 CYP1B1基因敲除对成年小鼠营养性肥胖的保护作用可能与AMPK磷酸化增强并调控肝脏中脂肪代谢相关基因的表达有关。     

Improved thymopoietic potential in aviremic HIV infected individuals treated with HAART by intermittent IL-2 administration

OBJECTIVE: In HIV-positive individuals administration of intermittent interleukin (IL)-2 in addition to highly active antiretroviral therapy (HAART) induces expansion of the peripheral T cell pool with dilution of signal joint T cell receptor excision circles (sjTREC) that cannot be used to measure thymic output. We analysed whether in vitro thymopoiesis could be used to predict in vivo thymic output in IL-2 treated subjects. DESIGN AND METHODS: We correlated the relative variation of peripheral CD4 T cells over 12 months in HIV-positive subjects on HAART or HAART + IL-2 with the mean levels of both sjTREC and T cells developed in chimeric murine foetal thymic organ cultures (FTOC) reconstituted with circulating progenitors. RESULTS: In contrast with HAART treated individuals in which these values were directly correlated, in subjects receiving HAART + IL-2 the increase of CD4 T cells in vivo was correlated to neither sjTREC number nor to reconstitution of FTOC, probably reflecting a main effect of IL-2 in the expansion of the peripheral T cell pool. Nevertheless, addition of IL-2 to HAART determined a significant increase of in vitro thymopoietic potential in individuals with undetectable viraemia. CONCLUSIONS: The increased T cell development in vitro after addition of IL-2 to HAART suggests that intermittent IL-2 administration may exert a positive influence on lymphopoiesis. In two subjects with positive viraemia treated with IL-2 we observed reduced in vitro development of T cell precursors suggesting that the positive influence of IL-2 on thymopoiesis could be secondary to the control of viral replication by HAART. These observations provide novel evidence in support of the potential beneficial use of IL-2 in HAART treated individuals.     

Use of multiple T cell-directed intact ricin immunotoxins for autologous bone marrow transplantation

The monoclonal antibodies (MoAb) T101, G3.7, 35.1, and TA-1 were conjugated to intact ricin using a thioether linkage. These MoAb detect, respectively, the CD5[gp67], CD7[p41], CD2[p50], and [gp95, 170] determinants that are found in the vast majority of cases of T cell acute lymphocytic leukemia (T-ALL). The resulting immunotoxins (ITs) and an equimolar mixture of these ITs were evaluated as potential purgative reagents for autologous transplantation in T-ALL. Leukemic cell lines were used to compare the kinetics of protein synthesis inactivation mediated by each IT. The cells were treated with IT in the presence of lactose in order to block the native binding of ricin. The observed rates of protein synthesis inactivation correlated with target antigen expression detected by fluorescence-activated cell sorter analysis. Of the four ITs, T101-ricin (T101-R) exhibited the fastest rate of inactivation, followed in order by G3.7-ricin, TA-1-ricin, and 35.1-ricin. At concentrations greater than 300 ng/mL, a cocktail containing an equimolar amount of all four ITs (referred to as the four- IT cocktail) exhibited kinetics that were as fast or faster than those of T101-R. The long-term cytotoxic effects of individual ITs and the four-IT cocktail were evaluated using a sensitive clonogenic assay. Each IT was specifically cytotoxic and inhibited 1 to 4 logs of clonogenic leukemic cells at doses (300 to 600 ng/mL) that can be used clinically. The four-IT cocktail was highly cytotoxic; a concentration of 300 ng/mL inhibited greater than 4 logs of leukemic cells while sparing the majority of committed (CFU-GM, CFU-E) and pluripotent (CFU- GEMM) hematopoietic stem cells. The determination of both short-term kinetics of protein synthesis inactivation and longer-term inhibition of clonogenic growth allowed new insight into cell killing by IT. Our results suggest that ITs continue to act on clonogenic target cells for a period of three to five days. Interestingly, the four-IT cocktail was not as potent against clonogenic leukemic cells as T101-R alone, although it exhibited kinetics of protein synthesis inhibition that were as fast as those of T101-R alone. This finding suggests that internalized ITs may differ in the length of time they remain active within the cell. Our results also demonstrate the importance of using several different assays to evaluate IT reagents.     

Characterization of the IgG-Fc receptor on human platelets

To determine quantitatively the number and avidity of receptors for the Fc portion of IgG on human platelets, we have measured the binding to platelets of human monomeric monoclonal IgG, and of small covalently crosslinked polymers of IgG1 labeled with 125I. The binding of labeled IgG1 monomers to platelets is too weak to permit quantitation. The binding of dimers or larger polymers of IgG1 is much more avid (greater at 4 degrees C than 37 degrees C), is readily reversible, and is saturable. The number of receptor sites ranges from 400 to 2000 per platelet and the mean equilibrium association constant (Ka) for the binding of dimers at 4 degrees C is 2.2 x 10(7) M-1 +/- 0.9 x 10(7) M- 1. The binding is specific for the Fc portion of IgG, and IgG1 and IgG3 bind to the receptors much more avidly than IgG2 or IgG4. Unlabeled IgG1 dimers are about 7--8-fold more potent in inhibiting binding than are IgG1 monomers, and larger polymers are even more potent than dimers. Thus, the Fc receptors on platelets bind human IgG1 with the same specificity and similar avidity as Fc receptors on polymorphonuclear leukocytes (PMNs), but PMNs have about 300-fold more receptors per unit of surface area than platelets.     

Anti-graft-versus-host disease effect of DT390-anti-CD3sFv, a single- chain Fv fusion immunotoxin specifically targeting the CD3 epsilon moiety of the T-cell receptor

In a recent study, we showed that an immunotoxin (IT) made with a conventional monoclonal antibody targeting the CD3 epsilon moiety of the T-cell receptor (TCR) had a potent, but partial, graft-versus-host disease (GVHD) effect (Vallera et al, Blood 86:4367, 1995). Therefore, in this current study, we determined whether a fusion immunotoxin made with anti-CD3 single-chain Fv (sFv), the smallest unit of antibody recognizing antigen, would have anti-GVHD activity. A fusion protein was synthesized from a construct made by splicing sFv cDNA from the hybridoma 145-2C11 to a truncated form of the diphtheria toxin (DT390) gene. DT390 encodes a molecule that retains full enzymatic activity, but excludes the native DT binding domain. The DT390-anti-CD3sFv hybrid gene was cloned into a vector under the control of an inducible promoter. The protein was expressed in Escherichia coli and then purified from inclusion bodies. The DT390 moiety of the protein had full enzymatic activity compared with native DT and DT390-anti-CD3sFv, with an IC50 of 1 to 2 nmol/L against phytohemagglutinin-stimulated and alloantigen-stimulated T cells. Specificity was shown (1) by blocking the IT with parental anti-CD3 antibody, but not with a control antibody; (2) by failure of DT390-anti-CD3sFv to inhibit lipopolysaccharide-stimulated murine B cells; (3) by failure of an Ig control fusion protein, DT390-Fc, to inhibit T-cell responses; and (4) with in vivo immunohistochemisty studies. GVHD was studied in a model in which C57BL/6 (H-2b)-purified lymph node T cells were administered to major histocompatibility complex (MHC) antigen disparate unirradiated C.B.-17 scid (H-2d) mice to assess GVHD effects in the absence of irradiation toxicity. Flow cytometry studies showed that donor T cells were expanded 57-fold and histopathologic analysis showed the hallmarks of a lethal model of GVHD. Control mice receiving phosphate-buffered saline showed 17% survival on day 80 after bone marrow transplantation, and mice receiving 2 micrograms DT390-Fc fusion toxin control administered in 2 daily doses for 6 days (days 0 through 5) had a 43% survival rate. In contrast, 86% of mice receiving the same dose of DT390-anti-CD3sFv were survivors on day 80, a significant improvement, although survivors still showed histopathologic signs of GVHD. These findings suggest that new anti-GVHD agents can be genetically engineered and warrant further investigation of fusion proteins for GVHD treatment.     

Autologous and allogeneic bone marrow transplantation for poor prognosis patients with B-cell chronic lymphocytic leukemia

Twenty patients with poor prognosis B-cell chronic lymphocytic leukemia (B-CLL) underwent uniform high-dose chemoradiotherapy followed by rescue with multiple monoclonal antibody-purged autologous bone marrow (BM) (12 patients) or T-cell-depleted allogeneic BM from HLA-identical siblings (8 patients) in a pilot study to assess the feasibility of BM transplantation (BMT) in this disease. All had poor prognosis disease by either staging, BM pattern, tumor doubling time criteria, or cytogenetics. All patients achieved remission criteria (defined as < or = 2 adenopathy, absence of splenomegaly, < or = 20% of the intertrabecular space involved on BM biopsy) before BMT. Despite the use of fludarabine, a median of three treatment regimens were required to achieve BMT eligibility. After BMT, all patients achieved complete hematologic engraftment. Toxicities were not significantly different between autologous versus allogeneic BMT. Two toxic deaths were observed. Of 19 evaluable patients, 17 clinical complete clinical remissions (89%) were observed, with 2 patients (1 allogeneic and 1 autologous) exhibiting persistent BM disease. Complete clinical remissions were documented at the phenotypic and molecular level for the majority of patients in whom dual fluorescence for CD5 and CD20 (15 of 15; 100%) and Ig gene rearrangements (11 of 14; 79%) were performed. Although long-term follow-up is needed to assess any potential impact on the disease-free and overall survival of these patients, this study shows the feasibility of using high-dose chemoradiotherapy and BMT in patients with poor prognosis B-CLL.     

Efficacy of low-dose intermittent subcutaneous interleukin (IL)--2 in antiviral drug--experienced human immunodeficiency virus--infected persons with detectable virus load: a controlled study of 3 il-2 regimens with antiviral drug therapy

To evaluate the safety and efficacy of 3 regimens of intermittent subcutaneous (sc) interleukin (IL)--2 in a phase 2 study, 61 antiviral drug-experienced human immunodeficiency virus (HIV)--positive patients were randomly assigned to one of the following study arms: antiretroviral therapy (ART) plus IL-2 (12 million IU [MIU] by continuous intravenous infusion, followed by 7.5 MIU twice a day, sc, every 8 weeks); ART plus IL-2 (7.5 MIU twice a day, sc, every 8 weeks); ART plus IL-2 (3 MIU twice a day, sc, every 4 weeks); or ART alone. A significant increase of circulating CD4 cells was observed in IL-2--treated subjects, compared with those given ART alone. Low doses of IL-2 were better tolerated. Despite the incomplete suppression of viral replication, IL-2 with ART did not increase either plasma viremia or cell-associated HIV DNA levels. Low doses of intermittent sc IL-2 induced a stable increase of peripheral CD4 cells that was indistinguishable from those associated with higher, less well-tolerated doses of IL-2.