CFU-megakaryocytic progenitors expanded ex vivo from cord blood maintain their in vitro homing potential and express matrix metalloproteinases.

BACKGROUND: In patients transplanted with cord blood (CB), prolonged thrombocytopenia is a major complication. However, this could be alleviated by supplementing the CB graft with ex vivo-expanded megakaryocytic progenitors (CFU-Meg), provided that the homing properties of these cells are not affected negatively by expansion. METHODS AND RESULTS: We assessed the in vitro homing potential of CFU-Meg progenitors expanded from CB and showed that the combination of thrombopoietin (TPO) with interleukin-3 (IL-3) used for expansion not only results in optimal proliferation of CFU-Meg but also protects these cells from apoptosis. Moreover, we found that ex vivo-expanded CFU-Meg maintained expression of the CXCR4 receptor throughout a 9-day culture and were chemoattracted towards a stromal cell-derived factor-1 (SDF-1) gradient. They also expressed matrix metalloproteinase-9 (MMP-9) and membrane-type (MT) 1-MMP, and transmigrated across the reconstituted basement membrane Matrigel. Finally, we observed that SDF-1 up-regulated the expression of both MMP-9 and MT1-MMP in CB CD34(+) cells and ex vivo-expanded CFU-Meg. DISCUSSION: We suggest that CB-expanded CFU-Meg, in particular those from day 3 of expansion, when their proliferation and in vitro homing potential are maximal, could be employed to supplement CB grafts and speed up platelet recovery in transplant recipients.

Membrane-derived microvesicles: important and underappreciated mediators of cell-to-cell communication.

Normal and malignant cells shed from their surface membranes as well as secrete from the endosomal membrane compartment circular membrane fragments called microvesicles (MV). MV that are released from viable cells are usually smaller in size compared to the apoptotic bodies derived from damaged cells and unlike them do not contain fragmented DNA. Growing experimental evidence indicates that MV are an underappreciated component of the cell environment and play an important pleiotropic role in many biological processes. Generally, MV are enriched in various bioactive molecules and may (i) directly stimulate cells as a kind of 'signaling complex', (ii) transfer membrane receptors, proteins, mRNA and organelles (e.g., mitochondria) between cells and finally (iii) deliver infectious agents into cells (e.g., human immuno deficiency virus, prions). In this review, we discuss the pleiotropic effects of MV that are important for communication between cells, as well as the role of MV in carcinogenesis, coagulation, immune responses and modulation of susceptibility/infectability of cells to retroviruses or prions.

A comparison of the abilities of nitrobenzylthioinosine, dilazep, and dipyridamole to protect human hematopoietic cells from 7-deazaadenosine (tubercidin).

Nitrobenzylthioinosine, dilazep, and dipyridamole are potent inhibitors of equilibrative transport of nucleosides that may have pharmacological applications in modulating the therapeutic index of nucleoside antimetabolites used in cancer chemotherapy. We have compared the relative abilities of these inhibitors to reduce the toxicity of in vitro exposures to tubercidin against clonogenic progenitor cells of normal human bone marrow (CFU-GEMM, BFU-E, CFU-GM) and of two leukemic human cell lines (HL-60/C1, CCRF-CEM) that differ in their expression of transporter subtypes. Short (1-h) exposures to 1 microM tubercidin alone inhibited colony formation (a) of normal human hematopoietic progenitors (CFU-GEMM, BFU-E, CFU-GM) by 100%, and (b) of HL-60/C1 and CCRF-CEM cells by > 90%. Pretreatment (30 min) with nitrobenzylthioinosine, dilazep, or dipyridamole followed by simultaneous treatment (1 h) with these transport inhibitors during tubercidin exposures reduced toxicity against hematopoietic progenitors and cell lines. Greater reductions of toxicity were consistently seen with bone marrow progenitors and CCRF-CEM cells than with HL-60/C1 cells. For CFU-GEMM, BFU-E, and CFU-GM cells, reductions in tubercidin toxicity of 50-100% were achieved at these concentrations: > or = 0.1 microM (nitrobenzylthioinosine); > or = 0.1 microM (dilazep); and > or = 3.0 microM (dipyridamole). Pretreatment (30 min) followed by simultaneous treatment (1 h) with any of the transport inhibitors (> or = 0.1 microM) and 0.1 microM [3H]-tubercidin blocked the uptake of radioactivity completely in CCRF-CEM cells and only partially in HL-60/C1 cells. These effects, which were consistent with the nucleoside transport phenotypes of CCRF-CEM cells (inhibitor-sensitive) and HL-60/C1 cells (inhibitor-sensitive and inhibitor-resistant), suggested that protection was due to the inhibition of tubercidin uptake via equilibrative nucleoside transport system(s). Light-density mononuclear cells from human bone marrow, of which the clonogenic progenitors represented only a minor (< 0.01%) subpopulation, possessed far fewer nitrobenzylthioinosine-binding sites (2 x 10(4) sites/cell, Kd = 0.7 nM) than either HL-60/C1 cells (1.7 x 10(5) sites/cell, Kd = 0.9 nM) or CCRF-CEM cells (3.3 x 10(5) sites/cell, Kd = 0.5 nM). Initial rates of uptake of 1 microM [3H]adenosine (0-6 s, 20 degrees C) by human bone marrow mononuclear cells were reduced partially by 0.1 microM inhibitor (nitrobenzylthioinosine > dipyridamole > dilazep) and completely by 10 microM inhibitor.(ABSTRACT TRUNCATED AT 400 WORDS)

Effect of duration of exposure to verapamil on vincristine activity against multidrug-resistant human leukemic cell lines.

Verapamil sensitizes multidrug-resistant cell lines to various heterocyclic anticancer drugs by inhibition of energy-dependent release of drug, presumably by interaction with membrane glycoproteins involved in drug efflux. This work assessed verapamil sensitization of human multidrug-resistant lymphocytic and myeloid leukemic cell lines (CEM/VLB100, HL-60/AR) to vincristine during exposures of short duration (4 h). When cells were transferred to drug-free medium immediately after simultaneous 4-h exposures to vincristine and verapamil, the antiproliferative activity of vincristine was not altered in CEM/VLB100 cells and was only moderately increased in HL-60/AR cells. In contrast, when cells were transferred to verapamil-containing medium, vincristine activity was greatly increased against both CEM/VLB100 and HL-60/AR cells. Verapamil enhanced accumulation and inhibited release of [3H]vincristine by CEM/VLB100 and HL-60/AR cells, indicating that the sensitization was due to an increase in cell-associated vincristine after transfer of cells to vincristine-free medium. Slot blot analysis of cellular RNA with the pMDR1 probe revealed high levels of expression of the mdr1 gene in CEM/VLB100 cells but no detectable expression in HL-60/AR cells. Consistent with this finding, polypeptides (Mr 170,000 to 180,000) that were recognized by a monoclonal antibody (C219) against P-glycoprotein were greatly overexpressed in CEM/VLB100 cells, but were expressed at low levels, if at all, in HL-60/AR cells. These results demonstrate the importance of duration of exposure to verapamil in reversing multidrug resistance, not only in cells that overexpress P-glycoprotein but also in cells, such as HL-60/AR, that express little, if any, P-glycoprotein.

Functional characterization of fibroblastic cells in long-term marrow cultures from patients with acute myelogenous leukemia.

We have investigated the role of acute myelogenous leukemia (AML) marrow-derived fibroblastic cells in the development of the hemopoietic microenvironment in vitro, and compared their functional integrity with that of their normal marrow-derived counterparts. Our results indicate that the development of stromal adherent layers in AML long-term marrow culture (LTMC) depends to a large extent on the presence of fibroblastic progenitors (fibroblast colony-forming units, CFU-F) in the bone marrow inoculum. Positive correlations were observed between the numbers of CFU-F in fresh AML marrow samples (nine cases studied) and the numbers of adherent nucleated cells (r = 0.91), adherent CFU-F (r = 0.87), adherent hemopoietic progenitors (r = 0.71), and colony-stimulating factor-1 (CSF-1) levels (r = 0.74) in LTMC. All the above parameters were drastically reduced in LTMC derived from AML marrows that contained low numbers of CFU-F (i.e. below the normal range of 76-130 CFU-F per 10(6) bone marrow cells) when compared with LTMC established from normal marrows. In contrast, no difference was observed in such parameters when normal LTMC and LTMC from AML patients with normal levels of marrow CFU-F were compared. Fibroblast adherent layers derived from AML patients with normal marrow CFU-F numbers produced normal levels of CSF-1 and showed a similar hemopoietic supportive capacity to that of fibroblast layers from normal bone marrow. Thus, our results suggest that (i) the presence of CFU-F in adequate levels in the bone marrow inoculum is critical for the adequate development of the hemopoietic microenvironment in LTMC, and (ii) AML marrow-derived fibroblasts seem to be functionally normal, at least in some AML patients.

Expression of beta 1 integrin mRNAs in human leukemic blasts.

Adhesion receptors from the very late activation (VLA) (beta 1) integrin subfamily play a role in the cooperation of hematopoietic progenitors with bone marrow stroma, and the disregulated expression of these molecules, as evaluated by immunophenotyping, has been implicated in the acquisition of the malignant phenotype by hematopoietic cells. In the present study, Northern hybridization was used to determine the pattern of expression of transcripts for VLA subunits in: (i) leukemic blasts obtained from the peripheral blood of ten patients with acute myelogenous leukemia (AML) of different FAB subclasses; (ii) the human leukemic cell lines KG-1, HL-60, K-562, HEL and U-937; and (iii) normal hematopoietic cells. Most of the AML blasts and the cultured leukemic cells expressed mRNAs for the beta 1 and alpha 5 subunits (the only exception among the cell lines was KG-1 cells) and these transcripts were also found in normal bone marrow progenitors, peripheral blood mononuclear cells (PBMNC), and peripheral blood monocytes. While the alpha 4 transcript was detected in all cultured cells but K-562, and in normal circulating monocytes, it occurred in blasts from only two AML patients and was weakly expressed in mature PBMNC. No specific pattern of expression of beta 1, alpha 5, and alpha 4 transcripts could be related to cell differentiation or maturation in the AML blasts and leukemic cell lines tested. None of the primary AML blasts or cultured cells showed mRNA messages for alpha 2, alpha 3 or alpha 6 chains of the beta 1 integrins. The results suggest that, in some cases of AML, the malignant phenotype of leukemic blasts may be associated with down-regulated transcription of the alpha 4 integrin subunit.

Production of tumor necrosis factor-alpha in human long-term marrow cultures from normal subjects and patients with acute myelogenous leukemia: effect of recombinant macrophage colony-stimulating factor.

We have recently reported that normal long-term marrow cultures (LTMC) treated with recombinant human macrophage colony-stimulating factor (rhCSF-1), as well as LTMC from patients with acute myelogenous leukemia (AML), produce a soluble activity capable of inhibiting hemopoietic colony formation in semisolid cultures. In the present study, we have found that such an activity is produced, both in normal and AML LTMC, by an adherent, nonfibroblastic cell population (most likely macrophages), and also by blast cells developed in AML LTMC. The presence of the inhibitory activity correlated with increased levels of tumor necrosis factor (TNF) in the culture supernatants. Part of the activity (30%) produced in rhCSF-1-treated normal LTMC was neutralized in colony assays by anti-TNF alpha monoclonal antibody. In contrast, the soluble inhibitory activity from AML LTMC was completely neutralized by anti-TNF alpha. However, addition of anti-TNF alpha (every 72 h, from day 0 to 21, at 125 ng/ml) to AML LTMC resulted in only partial neutralization of the inhibitory activity, indicating that production of TNF alpha is just one of the mechanisms by which normal hemopoiesis is inhibited in AML LTMC, and that other factors are involved in this process. In keeping with this idea, we found very high levels of prostaglandin E, a hemopoietic inhibitor, in the supernatant of cultures that contained the soluble inhibitory activity. Interestingly, rhCSF-1 showed opposite effects on TNF production in normal (up-regulation) and AML (down-regulation) LTMC, which suggests the presence of functionally abnormal, leukemia-derived macrophages in AML LTMC.

Effect of rhCSF-1 on human hemopoiesis in long-term cultures from patients with acute myelogenous leukemia.

Bone marrow and/or peripheral blood cells from seven patients with acute myelogenous leukemia (AML) were maintained for 7 weeks in Dexter-type long-term culture (LTC) in order to study the effect of exogenous recombinant human colony-stimulating factor-1 (rhCSF-1) and to quantitate endogenous levels of CSF-1. rhCSF-1 was added every 2 days during the first 3 weeks of culture at 15 ng/ml. In all but one culture, adding rhCSF-1 inhibited putative leukemic hemopoiesis [i.e. decreased numbers of abnormal (blast) colony-forming cells and blasts] and stimulated putative normal hemopoiesis (increased numbers of CFU-GM and macrophages). Our data, however, do not distinguish direct effects of rhCSF-1 on normal or leukemic cells from indirect effects mediated by accessory cells. In cultures with a poorly formed adherent layer (all derived from patients classified as M5), the endogenous levels of CSF-1 were lower than those in cultures with a good (confluent) adherent layer, indicating that the levels of CSF-1 in LTC from AML patients positively correlate with the formation of the adherent layer. Our data indicate that CSF-1 is an important modulator of human hemopoiesis in LTC established from AML bone marrow or peripheral blood, and that rhCSF-1 might be valuable for purging leukemic cells in LTC established from AML patients' bone marrow or peripheral blood for autologous transplantation.

Stem cell plasticity revisited: CXCR4-positive cells expressing mRNA for early muscle, liver and neural cells 'hide out' in the bone marrow.

It has been suggested that bone marrow (BM)-derived hematopoietic stem cells transdifferentiate into tissue-specific stem cells (the so-called phenomenon of stem cell plasticity), but the possibility of committed tissue-specific stem cells pre-existing in BM has not been given sufficient consideration. We hypothesized that (i) tissue-committed stem cells circulate at a low level in the peripheral blood (PB) under normal steady-state conditions, maintaining a pool of stem cells in peripheral tissues, and their levels increase in PB during stress/tissue injury, and (ii) they could be chemoattracted to the BM where they find a supportive environment and that the SDF-1-CXCR4 axis plays a prominent role in the homing/retention of these cells to BM niches. We performed all experiments using freshly isolated cells to exclude the potential for 'transdifferentiation' of hematopoietic stem or mesenchymal cells associated with in vitro culture systems. We detected mRNA for various early markers for muscle (Myf-5, Myo-D), neural (GFAP, nestin) and liver (CK19, fetoprotein) cells in circulating (adherent cell-depleted) PB mononuclear cells (MNC) and increased levels of expression of these markers in PB after mobilization by G-CSF (as measured using real-time RT-PCR). Furthermore, SDF-1 chemotaxis combined with real-time RT-PCR analysis revealed that (i) these early tissue-specific cells reside in normal murine BM, (ii) express CXCR4 on their surface and (iii) can be enriched (up to 60 x) after chemotaxis to an SDF-1 gradient. These cells were also highly enriched within purified populations of murine Sca-1(+) BM MNC as well as of human CD34(+)-, AC133(+)- and CXCR4-positive cells. We also found that the expression of mRNA for SDF-1 is upregulated in damaged heart, kidney and liver. Hence our data provide a new perspective on BM not only as a home for hematopoietic stem cells but also a 'hideout' for already differentiated CXCR4-positive tissue-committed stem/progenitor cells that follow an SDF-1 gradient, could be mobilized into PB, and subsequently take part in organ/tissue regeneration.

Bcr-abl-positive cells secrete angiogenic factors including matrix metalloproteinases and stimulate angiogenesis in vivo in Matrigel implants.

To further elucidate the role of angiogenesis in the pathogenesis of chronic myelogenous leukemia (CML) we evaluated the effects of the bcr-abl translocation on the secretion of the angiogenic factors VEGF, FGF-2, HGF, IL-8 and matrix metalloproteinases (MMPs) as well as on the angiogenic potential in vivo of bcr-abl+ cells. First, we examined murine FL5.12 cells transfected with the bcr-abl constructs p185, p210 and p230 and found that the transfected cells secreted as much as four-fold more VEGF (p185 > p210 >p230) than wild-type (wt) cells, as well as MMP-9 and MMP-2. When Matrigel fragments containing these bcr-abl+ cells were implanted subcutaneously in SCID or Balb-C mice they became significantly more vascularized and hemoglobinized than implants containing normal or wt cells (p185 > p210 > p230). Similarly, we found that myeloblasts expanded from bone marrow (BM) CD34+ cells derived from Philadelphia-positive CML patients secreted up to 10 times more VEGF, FGF-2, HGF and IL-8 compared to myeloblasts derived from normal donors' BM CD34+ cells and that BM mononuclear cells (MNC) isolated from CML patients induced vascularization of Matrigel implants in mice. Moreover, we found that peripheral blood MNC expressed MMP-2 and membrane-type (MT)1-MMP in about 50% of CML patients studied, and MMP-9 in all of them. Furthermore, VEGF stimulated the secretion of MMP-9 in these primary CML cells. We conclude that stimulation of angiogenesis by angiogenic factors, including MMPs, could play an important role in the pathogenesis of CML, suggesting that therapies targeting the newly formed endothelium could be developed for CML.

Use of the Matrigel-based assay to measure the invasiveness of leukemic cells.

The reconstituted basement membrane (Matrigel)-based assay was used to quantify the invasive potential of hematopoietic cells including cultured human leukemic cells (KG-1, K-562, HEL, HL-60, and U-937), normal bone marrow (BM) cells, and normal polymorphonuclear leukocytes (PMNL). We found that (i) in contrast to 6- to 72-hour incubation periods typically used in assays with solid tumor cells, most of the invasive cell populations tested here required only 2 to 4 hours to cross the Matrigel layer; (ii) unlike that of PMNL, whose invasiveness was stimulated by the addition of FMLP, the invasive rate of cultured leukemic cells was not affected by this chemoattractant; (iii) the rate of invasion was inversely proportional to the Matrigel concentration per filter but varied with the Matrigel batch used; (iv) the most consistent results were obtained when 2.5 to 4 x 10(5) cells were added to the top portion of the blind well; and (v) of all leukemic cells tested, the least differentiated myeloblastic KG-1 cells exhibited the highest invasive potential, which was comparable to that of normal PMNL. We conclude that the Matrigel-based assay can be used as a model system in studies of mechanisms regulating movement of hematopoietic cells across basement membrane barriers.

Heterotopically induced bone marrow formation: morphology and transplantation.

Following heterotopic osteogenesis by implantation of xenogeneic epithelia, established human amnion cell lines FL and WISH, and isolated transitional epithelium of dogs in mice, biogenesis of hematopoietic tissue among the induced bone ossicles was observed. Precursors and mature forms of erythroid, granuloid, lymphoid and megakaryocytic series were found in the induced bone marrow. The concentration of lymphocytes in the induced marrow was higher and that of erythropoietic cells lower as compared with orthotopic femur bone marrow. The yield of myeloid cells varied from 0.31 to 14.5 X 10(6) per induced bone nodule, and was higher when uroepithelium was used as an inductor. The induced bone marrow contained hemopoietic stem cells in concentration similar to that of medullar bone marrow and the induced bone marrow protected lethally irradiated syngeneic recipients when used in the same doses as orthotopic bone marrow.

Modulation of erythropoiesis and myelopoiesis by exogenous erythropoietin in human long-term marrow cultures.

In spite of their ability to support myelopoiesis for several months, human long-term marrow cultures (LTMC) are unable to sustain the production of mature erythroid cells for greater than 4 weeks. Because this preference correlates with the presence of myeloid growth factors and possible absence of erythroid factors in LTMC, we studied the effects of the erythroid growth and differentiation factor erythropoietin (Epo) on both erythropoiesis and myelopoiesis in human LTMC. Either natural or recombinant Epo was added weekly to LTMC for 10 weeks, and total cell number, numbers of hemopoietic progenitors (mixed lineage colony-forming units, CFU-MIX; erythroid burst-forming units, BFU-E; erythroid CFU, CFU-E; granulocyte-macrophage CFU (CFU-GM); granulocyte CFU, CFU-G; and macrophage CFU, CFU-M), erythroblasts (early and late), granulocytes, and macrophages were quantitated separately in the adherent and nonadherent layers of the cultures. In the absence of Epo, mature erythroid cells disappeared within the first 3-4 weeks, whereas in cultures supplemented with Epo, erythropoiesis was supported for up to 8 weeks. Results indicate that erythroid maturation is blocked at the BFU-E stage and that exogenous Epo may act on a mature subpopulation of BFU-E located in the nonadherent fraction of the cultures, promoting its maturation into CFU-E, which in turn develop into erythroblasts. However, despite Epo supplementation, erythropoiesis was not restored to in vivo proportions, suggesting that additional factors or conditions necessary for erythropoiesis are lacking in LTMC. Interestingly, we found that exogenous Epo reduced the numbers of presumably more mature (nonadherent) myeloid CFU (CFU-C), granulocytes, and macrophages compared to controls and did not alter the levels of any of the most primitive hemopoietic progenitors measured (CFU-MIX, adherent BFU-E, and adherent CFU-C). Thus the data show that exogenous Epo modulates hemopoiesis in human LTMC, enhancing erythropoiesis and suppressing myelopoiesis, but that its effects appear limited to modulating levels of the nonadherent (more mature) progenitors, leaving the numbers of the adherent (immature) progenitor cells unchanged.

Composition and functional integrity of the in vitro hemopoietic microenvironment in acute myelogenous leukemia: effect of macrophage colony-stimulating factor.

In the present work, we have investigated the composition and hemopoietic supportive capacity of eleven normal and six acute myelogenous leukemia (AML) marrow-derived stromal adherent layers, established in the absence or in the presence of recombinant human colony-stimulating factor 1 (rhCSF-1, macrophage colony-stimulating factor). Two of six AML adherent layers were deficient in composition (i.e., no confluency, reduced numbers of macrophages and fibroblastic progenitors, and no fat cell formation), resulting in reduced CSF-1 production and a poor hemopoietic supportive capacity (assessed by the ability of an irradiated stroma to sustain the growth of myeloid, erythroid, and multipotential progenitors derived from a second innoculum of normal bone marrow). Four out of six AML adherent layers showed levels of macrophages, fibroblastic progenitors, fat cells, and CSF-1 similar to those observed in adherent layers from normal bone marrow; however, their capacity to sustain normal hemopoiesis was still significantly reduced. The deficient hemopoietic supportive capacity of all AML adherent layers correlated with the presence of a soluble activity in the culture supernatant that inhibited hemopoietic colony formation. Addition of rhCSF-1 during the establishment of AML adherent layers significantly increased their hemopoietic supportive capacity. In contrast, the hemopoietic supportive capacity of normal adherent layers was reduced by rhCSF-1. The opposite effects of rhCSF-1 on the hemopoietic supportive capacity of normal and AML adherent layers correlated with the levels of the soluble inhibitory activity, that is, increased levels in cultures containing rhCSF-1-treated normal adherent layers, and slightly reduced levels in cultures of rhCSF-1-treated AML layers. These results indicate that, despite a morphologically normal composition in most cases (four out of six), the hemopoietic microenvironment developed in long-term marrow culture (LTMC) from all AML marrows analyzed has a deficient hemopoietic supportive capacity, due, at least in part, to the production of hemopoietic inhibitor(s). Such a deficiency can be partially overcome by establishing the stroma layers in the presence of rhCSF-1.

Differential MMP and TIMP production by human marrow and peripheral blood CD34(+) cells in response to chemokines.

As stromal cell-derived factor-1 (SDF-1), macrophage inflammatory protein-1alpha (MIP-1alpha), and interleukin-8 (IL-8) are implicated in the homing and mobilization of human hematopoietic progenitors (HPC), we hypothesized that these chemokines mediate the migration of HPC across subendothelial basement membranes by regulating production of matrix metalloproteinases (MMPs) and their natural tissue inhibitors (TIMPs). Assays for migration across reconstituted basement membrane (Matrigel) and chemotaxis were carried out using CD34(+) cells derived from normal human bone marrow (BM) and mobilized peripheral blood (PB). Secretion of MMPs and TIMPs was evaluated by zymography and reverse zymography and gene expression by RT-PCR. We found that an SDF-1 gradient increases the chemotaxis of BM and PB CD34(+) cells across Matrigel (BM > PB), which is blocked by inhibitors of MMPs (o-phenanthroline, rhTIMP-1, rhTIMP-2, and anti-MMP-9 and anti-MMP-2 antibodies) but enhanced by tumor necrosis factor-alpha (TNF-alpha), a strong stimulator of MMPs. Preincubation of these cells with SDF-1 stimulated the secretion of MMP-2 and MMP-9 in BM and PB CD34(+) cells but of TIMP-1 and TIMP-2 only in PB CD34(+) cells. Preincubation with MIP-1alpha and IL-8 also stimulated the secretion of MMP-9 and MMP-2 (BM > PB), but with respect to TIMPs, the effect was reversed (PB > BM), resulting in trans-Matrigel migration of BM but not of PB CD34(+) cells. We therefore propose that MMPs and TIMPs are involved in 1) SDF-1-induced chemotaxis of human HPC across subendothelial basement membranes, and 2) MIP-1alpha- and IL-8-stimulated migration of HPC.

The limited infectability by R5 HIV of CD34(+) cells from thymus, cord, and peripheral blood and bone marrow is explained by their ability to produce beta-chemokines.

The resistance of human bone marrow (BM) CD34(+) cells to human immunodeficiency virus (HIV) infection is at this point not fully understood. Recently we reported that the chemokines MIP-1alpha, MIP-1beta, and RANTES secreted by BM-derived CD34(+) cells may compete with the macrophagotropic HIV (R5 HIV) strain for the CCR5 coreceptor.In this study we extended our previous observations and examined various lympho-hematopoietic CD34(+) cells isolated from thymus (Th), cord blood (CB), mobilized peripheral blood (mPB), and BM for the expression of beta-chemokines binding to CCR5, i.e., MIP-1alpha, MIP-1beta, RANTES, MCP-2, MCP-3, and MCP-4, and the alpha chemokine SDF-1 (binding to CXCR4) as these chemokines may compete with the R5 and X4 HIV strains, respectively, for entry into cells. We found that Th-, CB-, mPB-, and BM-derived CD34(+) cells express mRNA transcripts for all the beta-chemokines tested but not for SDF-1. Using sensitive ELISA assays we found that although MIP-1alpha and MIP-1beta proteins were secreted by all the lympho-hematopoietic CD34(+) cells tested, RANTES was detectable only in media conditioned by BM- and CB-derived CD34(+) cells and not Th-derived cells. However, media conditioned by BM-, mPB- and Th-derived CD34(+) cells protected the T lymphocytic cell line (PB-1) from infection by the R5 but not the X4 HIV strain. Hence this study demonstrates that beta-chemokines are secreted by lympho-hematopoietic CD34(+) cells originating from various sources and that these endogenously secreted chemokines may limit entry of the R5 HIV strain into the cells by competing for the CCR5 coreceptor.

Review of docetaxel and doxorubicin-based combinations in the management of breast cancer: from metastatic to adjuvant setting.

Considering the efficacy of docetaxel (Taxotere, Rhône-Poulenc Rorer, Antony, France) and doxorubicin in advanced breast cancer and their potential noncross-resistance, two pilot studies of docetaxel/doxorubicin (TA)-based combinations were conducted, one being a phase I dose-finding study of TA and the second a phase II study of docetaxel/doxorubicin/cyclophosphamide (TAC). The only significant toxicity, seen in both trials, was neutropenia and its consequences such as febrile neutropenia without significant documented infections. Extrahematologic and particularly docetaxel-specific side effects (fluid retention) were mild. Particularly noteworthy was the absence of significant cardiac toxicity; overall, there was only one case of congestive heart failure (1%). In terms of efficacy, response rates in excess of 70% and 80% were noted in both studies, even for patients with visceral metastases. Several phase III randomized trials using TA or TAC are presently being performed in first-line metastatic breast cancer and most importantly in the adjuvant setting to assess whether TA-based combinations will change the natural history of breast cancer.

Monoclonal antibodies against human granulocytes and myeloid differentiation antigens.

Monoclonal antibodies (MCA) were obtained by immunizing BALB/c mice with 99% pure granulocytes from normal donors or with a whole leukocyte suspension obtained from a chronic myelogenous leukemia (CML) patient, and then fusing the mouse spleen cells with a 315-43 myeloma cell clone. Four MCA were selected and studied using ELISA, immunofluorescence, cytotoxicity assays, and FACS analysis. Antibodies 80H.1, 80H.3, and 80H.5 (from normals) and 81H.1 (from CML) detected antigens expressed on neutrophils. Antibodies 80H.1 and 80H.3 (IgG) also reacted with monocytes but not with other blood cell subsets. Antibodies 80H.5 and 81H.1 (IgM) were cytotoxic and reacted strongly with most of the cells of the neutrophil maturation sequence, i.e., myeloblasts, promyelocytes, myelocytes, and mature granulocytes. Antibodies 80H.5 and 81H.1 also inhibited CFU-GM growth stimulated by leukocyte feeder layers or placental conditioned media, but did not inhibit BFU-E and CFU-E. Antigens recognized by 80H.3, 80H.5, and 81H.1 were expressed both on a proportion of cells from HL.60, KG.1, ML.1, and K562 myeloid cell lines, and on a proportion of blast cells isolated from patients with acute myelogenous leukemia. They were not found on lymphoid cell lines or lymphoid leukemia cells. These MCA recognize either late differentiation antigens expressed on mature neutrophils and monocytes (80H.1 and 80H.3) or early differentiation antigens (80H.5 and 81H.1) specific to the granulocytic lineage. They may be useful for a better definition of those antigens specific to hematopoietic stem cells and their relationship with normal or neoplastic hematopoiesis.

Unstimulated human acute myelogenous leukemia blasts secrete matrix metalloproteinases.

PURPOSE: The secretion of metalloproteinases was examined, especially the 92-kDa and 72-kDa type IV collagenases/gelatinases, and their role in the degradation of reconstituted basement membrane (Matrigel) by leukemic blasts. METHODS AND RESULTS: Leukemic blasts were obtained from the peripheral blood of 11 patients diagnosed with acute myelogenous leukemia (AML). After incubation of the AML blasts in serum-free cultures, conditioned media were collected and examined by zymography. The 92-kDa gelatinase was detected in ten AML patients after 2 h and 24 h of incubation, and in five samples its activated form (83 kDa) was observed. 72-kDa gelatinase was detected in cell-conditioned media from four patients after 2 h and in media from ten patients after 24 h. Its activated forms (64-60 kDa) were observed in one of four samples after 2 h and in five of ten after 24 h. By contrast, normal peripheral mononuclear cells from healthy donors secreted only 92-kDa gelatinase after 24 h; the 72 kDa enzyme was not detectable. A specific inhibitor of metalloproteinases, 1,10-phenanthroline, significantly reduced the in vitro invasion of AML blasts in a Matrigel assay and completely inhibited gelatinolytic activity in zymography. CONCLUSIONS: We concluded that primary, unstimulated peripheral-blood AML blasts secrete metalloproteinases, which may contribute to the in vitro degradation of reconstituted basement membrane.

Expression of the active form of MMP-2 on the surface of leukemic cells accounts for their in vitro invasion.

The enhanced expression of matrix metalloproteinases (MMP), especially gelatinases MMP-2 and MMP-9, has been associated with the invasive behavior of tumor cells. Previously we reported that primary acute myelogenous leukemia blasts and human leukemic cultured KG-1 cells but not HEL cells penetrate a reconstituted basement membrane (Matrigel) in an invasion assay. In this study, we investigated the role of MMP-2 and MMP-9 in in vitro invasion by leukemic cells. We found that both recombinant human tissue inhibitor of metalloproteinase-2 (rhTIMP-2) and anti-MMP-2 antibody inhibit the invasiveness of KG-1 cells in the Matrigel assay (by 76% and 51% respectively), while anti-MMP-9 antibody does not, indicating that MMP-2 but not MMP-9 in involved in the invasive process. KG-1 cells were found to secrete constitutively the latent (but not the activated) forms of both MMP-2 and MMP-9 and, after stimulation with the phorbol ester 12-O-tetradecanoylphorbol 13-acetate (TPA), higher levels of these pro-MMP. TPA stimulation, however, did not increase the in vitro invasiveness of these cells. Analysis by Western blot and flow cytometry revealed the presence of the activated form of MMP-2 (64 kDa) on the surface of KG-1 cells and primary AML blasts, as well as MT-MMP in the homogenates of these cells. This active form of MMP-2 was not detected on the surface of HEL cells, which were non-invasive in vitro, although these cells secreted pro-MMP-2. In conclusion, leukemic KG-1 and primary acute myelogenous leukemia cells, which secrete pro-MMP-2 and pro-MMP-9, were also shown to express the activated form of MMP-2 on their cell surface. We suggest that this active form is essential to the in vitro invasion of leukemic cells.