Monoclonal circulating B cells in multiple myeloma. A continuously differentiating, possibly invasive, population as defined by expression of CD45 isoforms and adhesion molecules.

The origin of the malignant stem cell in multiple myeloma, despite years of investigation by many laboratories, remains elusive. We have described a population of monoclonal circulating B-lineage lymphocytes that has been detected in all myeloma patients analyzed, both at diagnosis and after chemotherapy, and that has many properties consistent with its definition as either a stem cell compartment or an intermediate between the stem cell and the bone marrow localized plasma cells. On average, 40% to 50% of peripheral blood mononuclear cells are abnormal B cells that express CD10 and PCA-1 in conjunction with B-lineage markers CD19, CD20, and CD24 and variable expression of CD5. The B cells are monoclonal by Southern blot analysis and represent a highly pleiomorphic population. The migratory patterns of these cells are unknown, and their presence in blood may reflect cells in transit from a parent organ such as spleen to bone marrow for terminal differentiation, or they may originate in the bone marrow prior to circulation and seeding of other skeletal or extraskeletal sites. The working hypothesis underlying this work postulates that these abnormal B cells originate outside the marrow, giving rise to plasma cells only after migration to the bone marrow, which provides a microenvironment conducive to terminal plasma cell differentiation. Bone marrow plasma cells do not include an actively proliferating component and are terminally differentiated end stage cells. In contrast, the circulating abnormal B cells include proliferating cells and appear to be heterogeneous in differentiation stage. Analysis of CD45 isoform expression indicates a population continuously differentiating from a late B-cell stage through the early plasma cell stages to an end stage plasma cell. Quantitative and qualitative expression of CD45 has been shown to characterize B-cell development, with a high density of the CD45RA isoform on mature resting B cells, a transition to CD45R0 on activated B cells, and a gradual loss of total CD45, predominantly of the CD45R0 isoform, during plasma cell development until, on end stage plasma cells, all CD45 expression is lost. In myeloma patients, all of these B-cell stages are represented, with the least differentiated B cells occurring in blood, intermediate stages in both blood and marrow, the most differentiated B and/or plasma cells in the bone marrow.(ABSTRACT TRUNCATED AT 400 WORDS)     

Granulocyte-colony Stimulating Factor and Retinoic Acid Cooperatively Induce Granulocytic Differentiation of Acute Promyelocytic Leukemia Cells in vitro

The interaction of granulocyte-colony stimulating factor (G-CSF) and retinoic acid (RA) in proliferation and differentiation of acute promyelocytic leukemia (APL) cells was examined. G-CSF stimulated proliferation of APL cells at concentrations of 0.1 to 50 ng/ml in a dose dependent manner. More than 10⁻⁸ M RA induced granulocytic differentiation of APL cells. Although G-CSF induced lysozyme activities in APL cells, it alone did not induce terminal differentiation of APL cells. G-CSF significantly enhanced the RA-induced granulocytic differentiation of APL cells in vitro. Enhancement by G-CSF was not due to the prolongation of survival of RA-induced differentiated cells, but the differentiation-inducing effects of G-CSF might be evident only in the presence of RA. Since G-CSF has a potential to induce the granulocytic differentiation of myeloid leukemia cells, G-CSF in combination with RA may be applicable in differentiation induction therapy for some types of myeloid leukemia.     

The role of human and viral cytokines in the pathogenesis of multiple myeloma

Multiple myeloma (MM) is characterized by the accumulation of monoclonal plasma cells, a terminally differentiated form of B lymphocyte, in the bone marrow. This disease is most often associated with bone destruction, anemia and renal failure. Besides the malignant plasma cells, it has become clear that nonmalignant cells in the bone marrow also contribute to the development of this malignancy by the release of cytokines. Further support for the importance of the supporting cells comes from our recent finding of the human herpesvirus 8 (HHV-8) in the nonmalignant bone marrow stromal cells from these patients.     

Alterations in Fas (CD 95/Apo-1) and Fas ligand (CD178) expression in acute promyelocytic leukemia during treatment with ATRA

Over the recent years, treatment of acute promyelocytic leukemia (APL) with all-trans retinoic acid (ATRA) has become a widely accepted therapeutic regimen and is considered a model of differentiation therapy in malignant diseases. However, the role of ATRA treatment beyond that of the induction of differentiation of leukemic blasts is still far from being fully understood. Data from in vivo and in vitro studies have demonstrated that during ATRA treatment of APL there are significant changes not only in the expression of the apoptotic molecules Fas and Fas ligand, but also in the expression of other molecules involved both in the regulation of apoptosis and in interactions between host immune and leukemia cells. These effects may thus contribute, at least in part, to the beneficial effects of ATRA therapy in APL. In this report we review the current status of studies that contribute to our understanding of treatment with ATRA. We focus on ATRA-induced changes in apoptotic pathways, particularly as it relates to the Fas/Fas ligand system.     

应用细胞形态学、细胞化学和电镜动态观察维甲酸对骨髓APL细胞的诱导分化作用

用以维甲酸为主的联合诱导分化方案治疗５０例初治ＡＰＬ，ＣＲ率为８８％（４４／５０）。在治疗前、治疗中、骨髓ＣＲ期，应用细胞形态学、细胞化学和电镜动态观察。ＣＲ病例ＡＰＬ细胞有明显成熟分化表现。４例ＰＲ病人，成熟分化改变不明显，有一定判断预后意义     

砷剂治疗急性早幼粒细胞白血病过程中细胞形态学及遗传学变化

目的 观察四硫化四砷(TATS)治疗初治和复发急性早幼粒细胞白血病(APL)过程中细胞形态学及细胞遗传学变化,探讨其作用机制。方法 应用骨髓短期培养法、染色体荧光原位杂交(FISH)技术及形态学技术,对13例初治及7例复发APL患者进行细胞遗传学和形态学分析。结果 8例患者的骨髓APL细胞中均出现分化现象。20例患者中,19例在TATS治疗过程中t(15;17)阳性细胞呈逐渐下降,与形态学风细胞百分比的下降具有相关性(r值范围0．7298—0．9989)。19例具有t(15;17)染色体易位的患者治疗后均达血液学完全缓解(CR),16例达细胞遗传学CR,1例具有t(11;17)易位的患者未达血液学CR。结论 TATS对初治及复发APL有一定的诱导分化作用,单药TATS治疗初治及复发APL患者可达到血液学和细胞遗传学缓解。应用FISH技术监测t(15;17)阳性细胞可以客观反映APL细胞变化规律。     

DCC (Deleted in Colorectal Cancer) Inactivation in Hematological Malignancies

DCC (Deleted in Colorectal Cancer) is a putative tumor suppressor gene located on chromosome band 18q21. Allelic deletions of one DCC locus have been found in more than 70% of colorectal carcinomas. Loss of DCC expression has been detected in 80% of all colorectal cancers and in many other types of tumor. DCC is expressed in normal bone marrow and peripheral lymphocytes, nevertheless DCC expression was absent or greatly reduced in 30% of acute leukemias and in 25% of Chronic Myelogenous Leukemias (CML). DCC encodes a transmembrane glycoprotein closely related to the adhesion molecules of the Neural Cell Adhesion Molecule (N-CAM) family. Glycoproteins of this family function like cell surface receptors and are involved in the regulation of many functions including cell recognition and cell differentiation. Highly specialized adhesion molecules participate in the regulation of hemopoiesis by mediating the interactions of hemopoietic cells with the components of the bone marrow microenvironment. Therefore, loss of DCC, as well as loss or alteration of other adhesion receptors, could contribute to leukemogenesis by impairing the interactions of the hemopoietic cells with the bone marrow microenvironment.     

Methylated metabolites of arsenic trioxide are more potent than arsenic trioxide as apoptotic but not differentiation inducers in leukemia and lymphoma cells

Treatment with arsenic trioxide (As(2)O(3)) by inducing apoptosis and partial differentiation of acute promyelocytic leukemia (APL) cells results in clinical remission in APL patients resistant to chemotherapy and all-trans-retinoic acid. As(2)O(3) (iAs(III)) is methylated in the liver to mono- and dimethylated metabolites, including methylarsonic acid, methylarsonous acid, dimethylarsinic acid, and dimethylarsinous acid. Methylated trivalent metabolites that are potent cytotoxins, genotoxins, and enzyme inhibitors may contribute to the in vivo therapeutic effect of iAs(III). Therefore, we compared the potency of iAs(III) and trivalent metabolites using chemical precursors of methylarsonous acid and dimethylarsinous acid to induce differentiation, growth inhibition, and apoptosis. Methylarsine oxide (MAs(III)O) and to a lesser extent iododimethylarsine were more potent growth inhibitors and apoptotic inducers than iAs(III) in NB4 cells, an APL cell line. This was also observed in K562 human leukemia, lymphoma cell lines, and in primary culture of chronic lymphocytic leukemia cells, but not human bone marrow progenitor cells. Apoptosis was associated with greater hydrogen peroxide accumulation and inhibition of glutathione peroxidase activity. MAs(III)O, in contrast to iAs(III), did not induce PML-retinoic acid receptor alpha degradation, or restore PML nuclear bodies or differentiation in NB4 cells. In a cocultivation experiment, hepatoma-derived HepG2 cells, but not NB4 cells, methylate radiolabeled iAs(III). Methylated metabolites released from HepG2 cells are preferentially accumulated by NB4 cells. This experimental model suggests that in vivo hepatic methylation of iAs(III) may contribute to As(2)O(3)-induced apoptosis but not differentiation of APL cells. MAs(III)O as an apoptotic inducer should be considered in the treatment of other hematologic malignancies like lymphoma.     

Enhancement of sensitivity by bestatin of acute promyelocytic leukemia NB4 cells to all-trans retinoic acid

All-trans retinoic acid (ATRA) induces the differentiation of acute promyelocytic leukemia (APL) cells into neutrophils. We found that bestatin, an inhibitor of CD13/aminopeptidase N, enhanced the sensitivity of APL NB4 cells to ATRA at concentrations of 0.1–1000 ng/ml. A structurally different aminopeptidase N inhibitor, actinonin, also increased the effect of ATRA on differentiation, but an inactive stereoisomer of bestatin, (2R,3S)-AHPA-(R)-Leu, did not. Bestatin synergistically enhanced the cytostatic effect of ATRA on NB4 cells. Masking of the cell-surface CD13 by anti-CD13 antibody WM15 blocked the synergistic effect of bestatin and ATRA on differentiation. Thus bestatin, an immunomodulator clinically used for nonlymphocytic leukemia, synergistically increased the ATRA-induced differentiation of NB4 cells by inhibiting CD13/aminopeptidase N on the cell-surface.     

A metal chelator,diphenylthiocarbazone, induces apoptosis in acute promyelocytic leukemia (APL) cells mediated by a caspase-dependent pathway without a modulation of retinoic acid signaling pathways

A metal chelator, diphenylthiocarbazone (dithizone), has been reported to induce differentiation and apoptosis of the human myeloid leukemia cell line HL-60, however, very little is known about the mechanism of dithizone-induced apoptosis. Here, we report for the first time that dithizone can induce inhibition of cellular growth of retinoic acid (RA)-sensitive NB4 and RA-resistant UF-1 APL cells via induction of apoptosis but not differentiation. Treatment of NB4 cells with dithizone markedly-induced apoptosis, which was associated with the loss of mitochondrial transmembrane potentials (Delta Psi(m)) and activation of caspase-3 and -9. Further investigation of the RA-resistant UF-1 APL cells showed that dithizone-induced apoptosis to a lesser extent. However, neither dithizone alone nor in combination with all-trans RA induced the expression of myeloid differentiation antigen CD11b. Concomitantly, the degradation of PML/RARalpha fusion protein was not observed after treatment with dithizone alone, and the degradation was not enhanced by the combination of dithizone and all-trans RA. We conclude that dithizone, a metal chelator, induced apoptosis without differentiation in APL cells in association with Delta Psi(m) collapse and caspase-3 and -9 activation.     

Inhibition of granulocytic differentiation of acute promyelocytic leukemia cells in primary culture by transforming growth factor-β

We investigated the effect of transforming growth factor-β₁ (TGFβ) on the proliferation and differentiation of cultured acute promyelocytic leukemia (APL) cells with the chromosomal t(15;17) translocation obtained from four patients to determine the role of TGFβ on growth and differentiation of APL cells.

DNA synthesis, determined by ³H-thymidine uptake, was inhibited in the presence and absence of granulocyte colony-stimulating factor (G-CSF) in a dose-dependent manner by TGFβ in APL cells obtained from three of the four cases. TGFβ and G-CSF did not significantly affect the differentiation of APL cells, but all-trans retinoic acid (RA) induced morphological and functional differentiation in all APL cells tested. G-CSF markedly enhanced RA-induced granulocytic differentiation in APL cells obtained from all four cases. In cells in which TGFβ inhibited DNA synthesis, it also inhibited RA-induced granulocytic differentiation of APL cells and, to a greater degree, granulocytic differentiation induced by RA plus G-CSF.

These results suggest that TGFβ is a negative regulator of the proliferation and differentiation of APL cells. The significance of TGFβ as an endogenous regulator in differentiation therapy with RA of APL patients is discussed.     

CCAAT增强子结合蛋白同源蛋白在丹参酮ⅡA诱导急性早幼粒细胞白血病细胞分化中的作用

 目的　探索CCAAT增强子结合蛋白同源蛋白（CHOP）在丹参酮ⅡA（TanⅡA）诱导急性早幼粒细胞白血病（APL）细胞分化中的作用。方法　反转录-聚合酶链反应（RT-PCR）及Western blot测定TanⅡA干预的NB4细胞的CHOP表达,通过形态学和膜表面标志检测APL细胞的分化,RNA干扰抑制CHOP表达。结果　TanⅡA诱导APL分化过程中伴有CHOP蛋白表达（1.933±0.987）和mRNA表达（1.587±0.815）的增加,相对于对照组蛋白和mRNA表达（0.537±0.110和0.713±0.090）,差异有统计学意义（mRNA水平F＝52.256,P＜0.01;蛋白水平F＝114.852,P＜0.01）;TanⅡA联合RNA干扰抑制CHOP的表达能更加有效的提高APL的分化[（50.767±1.241）% 与（16.167±2.122）%]（F＝989.431,P＜0.05）和凋亡[（89.233±5.581）%与（27.433±2.957）%]（F＝308.961,P＜0.05）。结论　CHOP在TanⅡA诱导APL分化过程中起着负向调节作用,抑制CHOP表达联合TanⅡA可能成为一个更好的治疗策略。     

Detection of apoptosis in acute promyelocytic leukemia cells in vivo during differentiation-induction with all-trans retinoic acid in combination with chemotherapy.

In two patients with acute promyelocytic leukemia (APL) treated with all-trans retinoic acid (ATRA) in combination with chemotherapy, we demonstrated that cells with apoptotic morphology were recognized in a small fraction of whole blood cells (0.2-0.4%) at the regression phase of leukocytosis with mostly maturing aberrant granulocytes of APL clone origin. Moreover, in a light-density cell fraction ( < 1.077) of peripheral blood or marrow cells obtained from three patients, DNA fragmentation was detected by agarose gel electrophoresis temporarily. These findings may suggest that, during the treatment with ATRA, a small fraction of APL cells maturing toward the stage of terminal differentiation underwent apoptosis in vivo, which might be enriched by the combination of chemotherapy to ATRA administration.     

The developmental program of murine erythroleukemia cells

Hematopoietic stem cells (HSCs) or early progenitors respond to external stimuli in bone marrow and differentiate into cell-restricted lineages of blood cells of limited life span. In leukemias, however, early hematopoietic progenitors self-renew themselves, fail to respond to differentiation signals, and do not undergo programmed cell death (apoptosis). The basic mechanisms of differentiation and apoptosis of leukemia cells have been the long-term objective of our work. By exploiting widely studied murine and human leukemic cell systems as models of hematopoietic cell differentiation, we explored the mechanisms by which pharmaceutical agents initiate differentiation in leukemic systems. In this article, we present the developmental program of MEL cells with emphasis given on the role of commitment to terminal maturation. Commitment is initiated via inducer-receptor-mediated processes and leads to discrete patterns of expression of several genes that contribute to growth arrest at the G1 phase, expression of differentiated phenotype, and differentiation-dependent apoptosis (DDA). Overall, MEL erythroid cell differentiation represents a developmental program with a highly coordinated set of processes that is "triggered" by an inducer and functions via a network of genes and proteins interacting with each other harmonically to give birth to lineage-restricted phenotype.