Oral valganciclovir versus ganciclovir as delayed pre-emptive therapy for patients after allogeneic hematopoietic stem cell transplant: a pilot trial (04-0274) and review of the literature.

BACKGROUND: Cytomegalovirus (CMV) infection is an important cause of morbidity and mortality after allogeneic hematopoietic stem cell transplant (HSCT). This pilot prospective randomized clinical trial compares valganciclovir (VGV) to ganciclovir (GCV) as pre-emptive therapy for CMV viremia in the post-allogeneic HSCT population. METHODS: Patients undergoing allogeneic HSCT who were at risk for CMV viremia were monitored post HSCT by weekly quantitative whole blood polymerase chain reaction. Pre-emptive therapy was delayed until the viral load (VL) was >10,000 copies/mL once, or >5000 copies/mL twice. Patients were randomized to either GCV 5 mg/kg twice a day (b.i.d.) for 7 days followed by daily GCV 5 mg/kg for up to 21 days, or VGV 900 mg b.i.d. for 7 days followed by 900 mg daily for up to 21 days. The primary endpoint was clearance of viremia (VL <5000 copies/mL) within 28 days of initiation of therapy. RESULT: In total, 37 patients were enrolled; 19 patients received treatment with VGV and 18 patients received treatment with GCV. The VGV was not inferior in efficacy to GCV as pre-emptive therapy, with rates of viral clearance at 28 days of 89.5% and 83%, respectively (P-value for non-inferiority = 0.030). Toxicities were similar between the 2 arms. No patients developed CMV disease. CONCLUSIONS: In this trial, the rates of clearance of viremia appear to be similar with VGV and GCV.

Vascular cell adhesion molecule-1 and the integrin VLA-4 mediate adhesion of human B cell precursors to cultured bone marrow adherent cells.

Adhesion of B cell precursors to accessory cells in the bone marrow microenvironment may be required for normal early B cell development. Human bone marrow B cell precursors adhere more avidly than mature B cells to bone marrow-derived fibroblasts. To determine the mechanism of this adhesion, expression of adhesion proteins on human B precursor cells and cell lines was measured by flow cytometry. The very late antigen (VLA) integrins VLA-4 and VLA-5 were the only adhesion proteins expressed at higher levels in B cell precursors than mature B cells. Antibodies to the alpha and beta chains of VLA-4, but not VLA-5, significantly blocked binding to bone marrow-derived fibroblasts of immature B cells and cell lines. Although fibronectin is a ligand for VLA-4, anti-fibronectin antibody and a soluble fibronectin fragment containing the VLA-4 binding domain did not block adhesion, suggesting that VLA-4 is involved in adhesion of B cell precursors, but not as a fibronectin receptor. Vascular cell adhesion molecule-1 (VCAM-1), the other known counterreceptor for VLA-4, was identified on bone marrow-derived fibroblasts, and anti-VCAM-1 significantly blocked adhesion of normal B cell precursors to bone marrow-derived fibroblasts, indicating that VLA-4/VCAM-1 interactions are important in adhesion of B cell precursors to the bone marrow microenvironment.

Dynamic changes in the clonal structure of MDS and AML in response to epigenetic therapy.

Traditional response criteria in myelodysplastic syndrome (MDS) and acute myeloid leukemia (AML) are based on bone marrow morphology and may not accurately reflect clonal tumor burden in patients treated with non-cytotoxic chemotherapy. We used next-generation sequencing of serial bone marrow samples to monitor MDS and AML tumor burden during treatment with epigenetic therapy (decitabine and panobinostat). Serial bone marrow samples (and skin as a source of normal DNA) from 25 MDS and AML patients were sequenced (exome or 285 gene panel). We observed that responders, including those in complete remission (CR), can have persistent measurable tumor burden (that is, mutations) for at least 1 year without disease progression. Using an ultrasensitive sequencing approach, we detected extremely rare mutations (equivalent to 1 heterozygous mutant cell in 2000 non-mutant cells) months to years before their expansion at disease relapse. While patients can live with persistent clonal hematopoiesis in a CR or stable disease, ultimately we find evidence that expansion of a rare subclone occurs at relapse or progression. Here we demonstrate that sequencing of serial samples provides an alternative measure of tumor burden in MDS or AML patients and augments traditional response criteria that rely on bone marrow blast percentage.

The "bystander effect": tumor regression when a fraction of the tumor mass is genetically modified.

Tumor cells expressing the herpes simplex virus thymidine kinase (HSV-TK) gene are sensitive to the drug ganciclovir (GCV). We demonstrate here that HSV-TK-positive cells exposed to GCV were lethal to HSV-TK-negative cells as a result of a "bystander effect." HSV-TK-negative cells were killed in vitro when the population of cultured cells contained only 10% HSV-TK-positive cells. The mechanism of this "bystander effect" on HSV-TK-negative cells appeared to be related to the process of apoptotic cell death when HSV-TK-positive cells were exposed to GCV. Flow cytometric and electron microscopic analyses suggested that apoptotic vesicles generated from the dying gene-modified cells were phagocytized by nearby, unmodified tumor cells. Prevention of apoptotic vesicle transfer prevented the bystander effect. The toxic effect of HSV-TK-positive cells on HSV-TK-negative cells was reproduced in an in vivo model. A mixed population of tumor cells consisting of HSV-TK-positive and HSV-TK-negative cells was inoculated s.c. into mice. Regression of the tumor mass occurred when the inoculum consisted of as few as 10% HSV-TK-expressing tumor cells. The bystander effect was also demonstrated in i.p. tumor studies. Initial experiments demonstrated that prolonged survival (> 70 days) occurred when a mixture containing 50% HSV-TK-positive and 50% HSV-TK-negative cells was injected i.p. followed by GCV treatment. Further, survival was prolonged for mice with a preexisting HSV-TK-negative i.p. tumor burden by injecting HSV-TK-positive cells and GCV. These results suggest that genetic modification of tumor cells may be useful for developing cancer therapies.

Mobilization of peripheral-blood stem cells by concurrent administration of daniplestim and granulocyte colony-stimulating factor in patients with breast cancer or lymphoma.

PURPOSE: To evaluate the safety and hematopoietic activity of daniplestim administered concurrently with granulocyte colony-stimulating factor (G-CSF) for peripheral-blood stem-cell (PBSC) mobilization. PATIENTS AND METHODS: In the initial dose-escalation phase, 25 patients with adenocarcinoma of the breast (AB; 13 patients) or lymphoma (12 patients) were given daniplestim at doses ranging from 0.1 to 3.75 microgram/kg/d plus G-CSF 10 microgram/kg/d. In the randomized phase, 52 patients with AB (27 patients) or lymphoma (25 patients) were randomized within disease categories to the daniplestim dose chosen in the dose-escalation phase plus G-CSF 10 microgram/kg/d (D+G) or placebo plus G-CSF 10 microgram/kg/d (P+G) for up to 7 days. RESULTS: A daniplestim dose of 2. 5 microg/kg/d was chosen for further study because it was hematopoietically active and had an acceptable side-effect profile. In the randomized phase, in patients with AB, D+G was associated with a higher probability (P =.0696) of collecting >/= 2.5 x 10(6) CD34(+) cells/kg and significantly higher circulating CD34(+) cell counts (P =.0498) on days 6 through 9 after the initiation of dosing. The target level was more likely to be reached with additional leukaphereses in the patients given D+G. Patients given P+G did not benefit from additional leukaphereses beyond the first procedure. The type of mobilization did show a trend toward a shorter duration of neutropenia in the D+G group. The adverse events with D+G consisted largely of mild to moderate flu-like symptoms, including headache and fever, and occurred more frequently than with P+G. CONCLUSION: Daniplestim administered at 2.5 microgram/kg/d is tolerable and active when combined with G-CSF, and the combination may prove more effective than G-CSF alone in promoting the collection of adequate numbers of CD34(+) cells for PBSC infusion in patients with AB.

One hundred autotransplants for relapsed or refractory Hodgkin's disease and lymphoma: value of pretransplant disease status for predicting outcome.

PURPOSE: One hundred autotransplants for Hodgkin's disease (HD) or non-Hodgkin's lymphoma (NHL) were examined prospectively to identify variables with prognostic significance. PATIENTS AND METHODS: Ninety-six patients with relapsed or refractory HD or NHL underwent 100 autotransplants. Patients received high-dose carmustine (BCNU), etoposide, cytarabine, and cyclophosphamide (BEAC) followed by unpurged autologous stem-cell rescue. RESULTS: The 3-year actuarial event-free survival (EFS) rate for the 47 HD patients is 49%, with a median followup duration of 2 years. For the 53 NHL patients, the 3-year actuarial EFS rate is 40%, with a median follow-up duration of 19 months. By multivariate analysis, minimal disease on admission (all areas < or = 2 cm) is associated with improved EFS (HD, P = .003, NHL, P = .03). The projected EFS rate for HD patients entering with minimal disease is 70% versus 15% for patients with bulky disease (P = .0001). The projected EFS rate for NHL patients with minimal disease is 48% versus 25% for patients with bulky disease (P = .04). Posttransplant involved-field radiotherapy, administered to 26 of the last 61 patients, was associated with an improved EFS rate for NHL patients (P = .015). The BEAC regimen was well tolerated by patients who entered the study with minimal disease (mortality rate, < 5%), but caused significant toxicity in patients with bulky disease (mortality rate, 25%). CONCLUSION: Disease burden before autotransplantation is an important predictor of regimen-related toxicity and EFS. Posttransplant involved-field radiotherapy may improve outcomes in select patients with NHL. The BEAC regimen is safe and effective, particularly for patients with minimal disease.

Analysis of factors that correlate with mucositis in recipients of autologous and allogeneic stem-cell transplants.

PURPOSE: To identify predictors of oral mucositis and gastrointestinal toxicity after high-dose therapy. PATIENTS AND METHODS: Mucositis and gastrointestinal toxicity were prospectively evaluated in 202 recipients of high-dose therapy and autologous or allogeneic stem-cell rescue. Of 10 outcome variables, three were selected as end points: the peak value for the University of Nebraska Oral Assessment Score (MUCPEAK), the duration of parenteral nutritional support, and the peak daily output of diarrhea. Potential covariates included patient age, sex, diagnosis, treatment protocol, transplantation type, stem-cell source, and rate of neutrophil recovery. The three selected end points were also examined for correlation with blood infections and transplant-related mortality. RESULTS: A diagnosis of leukemia, use of total body irradiation, allogeneic transplantation, and delayed neutrophil recovery were associated with increased oral mucositis and longer parenteral nutritional support. No factors were associated with diarrhea. Also, moderate to severe oral mucositis (MUCPEAK > or = 18 on a scale of 8 to 24) was correlated with blood infections and transplant-related mortality: 60% of patients with MUCPEAK > or = 18 had positive blood cultures versus 30% of patients with MUCPEAK less than 18 (P =.001); 24% of patients with MUCPEAK > or = 8 died during the transplantation procedure versus 4% of patients with MUCPEAK less than 18 (P =.001). CONCLUSION: Gastrointestinal toxicity is a major cause of transplant-related morbidity and mortality, emphasizing the need for corrective strategies. The peak oral mucositis score and the duration of parenteral nutritional support are useful indices of gastrointestinal toxicity because these end points are correlated with clinically significant events, including blood infections and treatment-related mortality.

Gene-modified cells for the treatment of cancer.

Gene therapy involves the insertion of a gene into an organism to treat a disease. Since its early development in the 1970s, gene therapy has expanded rapidly both in terms of the methods available and the number of candidate diseases for treatment. This report reviews gene therapy for cancer, including methodology, pre-clinical studies and experimental clinical trials.

Characterization of the adherence of normal and leukemic CD34+ cells to endothelial monolayers.

The capacity of normal CD34+ marrow cells and CD34+ leukemic cell lines to adhere to human umbilical vein endothelial cells has been examined. Such interactions have importance since the processes of homing and egress within the marrow microenvironment involve the traverse of sinusoidal endothelium. Umbilical vein endothelial monolayers expressed CD44 and CD54 constitutively, and expression of both E-selectin (ELAM) and vascular cell adhesion molecule-1 (VCAM-1) were inducible with interleukin-1 (IL-1) alpha and beta and tumor necrosis factor (TNF). CD34+ marrow cells bound to unstimulated endothelial layers (33 vs. 16% to plastic), and their adhesion was significantly increased in the presence of IL-1 or TNF. This increased adhesion was not inhibited by functionally blocking antibodies to E-selectin or to CD54 but was partially inhibited by antibodies to VCAM. CD34+ KG1a cells also bound to endothelial monolayers (33 vs. 8% to plastic), and such adhesion was also upregulated by pretreatment of the endothelial cells with IL-1 or TNF. In contrast to normal CD34+ cells, this increased adhesion was inhibited by antibodies to E-selectin but not to VCAM. These findings indicate that adhesion of both normal CD34+ cells and leukemic blasts to endothelial cells can be upregulated by inflammatory mediators such as TNF and IL-1.

Effects of the farnesyl transferase inhibitor R115777 on normal and leukemic hematopoiesis.

Patients with acute myelogenous leukemia or myelodysplastic syndrome may respond to farnesyl transferase inhibitors (FTIs) with partial or complete response rates noted in about 30% of such patients. FTIs prevent the attachment of a lipid farnesyl moiety to dependent proteins prior to their insertion into the plasma membrane and thereby prevent activity of these prenylation-dependent proteins, but their mechanism of tumor suppression remains unknown. Many patients receiving FTIs do experience myelosuppression. In this work, the in vitro effects of the FTI, R115777 on normal and leukemic hematopoiesis have been examined as have its effects on apoptosis induction and cell cycle profile in both leukemic blasts and normal CD34+ cells. R115777 was inhibitory to normal CD34+ cell proliferation and to leukemic blast cells, but did not affect long-term culture initiating cell frequency nor NOD-SCID reconstituting capacity. No induction of apoptosis or cell cycle changes were noted in AML blasts. These data suggest that myelosuppression with R115777 occurs largely at the intermediate to late progenitor stage of hematopoiesis and that cyclic use might avoid long-term marrow suppression.

Purification of GCT cell-derived human colony-stimulating factors.

We have purified human-active colony-stimulating factors from the human cell line, GCT, using sequential ultrafiltration; cation exchange, gel permeation, and reverse-phase high performance liquid chromatography (RHPLC); and ion-exchange HPLC. Activity eluted from sodium dodecyl sulfate-polyacrylamide gels with a peak at 17,500 daltons. Similar results were obtained by processing 35S-methionine-labeled conditioned medium, which showed a labeled band in the same region of activity. This purified HPLC fraction, which had a specific activity of greater than 1 x 10(7) colonies/mg protein, stimulated neutrophil colonies at day 7 and neutrophil, neutrophil-macrophage, and eosinophil colonies at day 14 of culture, suggesting that it contained both granulocyte (G-CSF) and granulocyte-macrophage (GM-CSF) colony-stimulating factors. It also promoted the growth of erythroid progenitors, and the GM-CSF fraction purified by hydrophobic chromatography had erythroid-enhancing activity. Separation of G-CSF from GM-CSF was accomplished by the addition of trifluoroacetic acid to the mobile phase at the reverse-phase HPLC step.

Effect of stem cell factor on myelopoiesis potential in human Dexter-type culture systems.

Hematopoiesis is influenced by the presence of the hematopoietic microenvironment, and Dexter-type liquid culture systems represent an in vitro representation of some aspects of the microenvironment that are optimal for the propagation of myeloid progenitors. Marrow stromal layers, which constitute part of these culture systems, produce growth factors, including stem cell factor (SCF), a ligand for the c-kit proto-oncogene that has been found to increase detection of myeloid, erythroid, and megakaryocytic progenitors in short-term marrow colony assays. In this work, the role of SCF in Dexter-type culture systems was examined to better define its contribution to steady-state myelopoiesis. When cultured in the continued presence of 100 ng/mL SCF, both primary and recharged cultures demonstrated significantly greater CFU-GM output, with quantitative differences noted throughout culture duration (up to 6 weeks). This increase in CFU-GM could be inhibited specifically with the addition of 1:1500 SR-1, a neutralizing anti-c-kit monoclonal antibody (MAb) that neutralizes the biological effects of SCF, and the increase was noted both with recharged light-density marrow cells and purified CD34+ progenitor cells. On the other hand, when primary or recharged marrow cultures were established in the absence of exogenous SCF, but in the continuous presence of SR-1, no inhibition of CFU-GM output was observed. When light-density marrow cells were purged of pre-existing CFU-GM by 4-hydroperoxycyclophosphamide (4-HC) and were seeded over irradiated stromal layers, exogenous SCF resulted in detection of CFU-GM from 4-HC-treated cells as early as 1 week of culture, as compared to the lack of significant emergence of CFU-GMs at 4 weeks in the control cultures. This SCF effect was also inhibited by SR-1. Purified CD34+ progenitor cells did not adhere to SCF immobilized to tissue culture plates, and the adhesion of such progenitors to murine Steel lines transfected with membrane-bound SCF was not greater than to the parent nontransfected Steel line, suggesting that the effect of SCF was not on CD34+ cell adhesion. These studies confirm the action of SCF at a pre-CFU level, and they demonstrate the ability of SCF to stimulate increased production of myeloid progenitors in long-term liquid culture systems.

In vivo analysis of the 'bystander effect': a cytokine cascade.

The "bystander effect" refers to the death of unmodified tumor cells when in contact with ganciclovir (GCV)-exposed, herpes simplex virus-thymidine kinase (HSV-TK)-modified tumor cells. Although the exact mechanism or mechanisms involved in mediating the bystander effect in vivo are unknown, our findings suggest that an intact host immune system is required for the phenomenon to occur. The present study was designed to establish the effect of HSV-TK-modified tumor cells and GCV on the tumor and its microenvironment in vivo. In sublethally irradiated and immunodeficient Balb/c mice, the bystander effect was observed to be diminished or abrogated. Histopathologic examination of the tumor mass from immunocompetent mice demonstrated centralized hemorrhagic tumor necrosis (38%) after inoculation of the HSV-TK-modified tumor cells and GCV in tumor-bearing mice compared with the control mice (5%), indicating that cytokines such as tumor necrosis factor-alpha (TNF-alpha) were being released locally. This hypothesis was underscored using reverse transcriptase polymerase chain reaction (RT-PCR), by the demonstration of cytokine mRNA expression in mice treated with HSV-TK-expressing tumors and GCV. Semiquantitative PCR analysis for TNF-alpha using PCR-MIMIC on tumor samples from mice treated on days 1 and 4 showed a two-fold increase in the level on mRNA expression. Also, immunohistochemical staining for TNF-alpha showed that mononuclear inflammatory cells infiltrating the tumor were its source. Finally, characterization of tumor-infiltrating lymphocytes (TIL) in experimental animals demonstrated a two- to three-fold increase in the number of macrophages and T cells compared with control animals. These results demonstrate that, in vivo, the bystander effect is mediated in part by an antitumor response through the release of cytokines. Further, the cytokine milieu and tumor microenvironment can be modulated following injection of HSV-TK cells and GCV to enhance the host immune response, which is of potential use in clinical trials.

Survival of granulocytic progenitors in the nonadherent and adherent compartments of human long-term marrow cultures.

We have studied the survival of granulocytic and monocytic progenitor cells (CFU-GM) in human liquid marrow cultures. CFU-GM were present in the nonadherent cell population for a mean of 12 weeks without recharging . Histochemical analysis of agar gels revealed that most day-7 colonies were of neutrophilic type (CFU-N), whereas the majority of day-14 colonies were of mixed neutrophilic-macrophagic type (CFU-NM) for the first four weeks of culture and became predominantly of macrophagic type (CFU-M) thereafter. Eosinophilic colonies (CFU-Eo) declined after week 2 of culture. We have documented that CFU-GM were present in the adherent layer of these cultures, and that the CFU-GM in the nonadherent compartment arise from the adherent layer. In addition, we have compared the pre-CFU-GM survival in the adherent and nonadherent populations and determined that these progenitors were rapidly depleted from both compartments though their survival at the end of week 1 was better in the adherent than in the nonadherent layer.

Adhesive interactions of normal and leukemic human CD34+ myeloid progenitors: role of marrow stromal, fibroblast, and cytomatrix components.

Adhesive interactions between CD34+ myeloid progenitors, cytomatrix components, and marrow fibroblast and stromal monolayers are described and compared to the binding interactions of the CD34+ myeloid leukemic cell lines KG1a and KG1. Both normal precursors and their leukemic counterparts showed adhesion to marrow stroma and fibroblasts. CD34+ myeloid progenitors bound to the extracellular matrices of marrow stromal cell and fibroblast monolayers and to laminin and fibronectin to a lesser extent than to cellular stromal layers. These adhesive interactions were not inhibited by polyclonal antibodies to laminin or fibronectin, nor by 1 mM Arg-Gly-Asp-Ser (RGDS)-containing peptides. Also, although both normal and leukemic cells expressed the CD18 antigen, binding of these cells to stroma was not inhibited by blocking anti-CD18 monoclonal antibodies. Finally, KG1a adhesion was not blocked in the presence of anti-CD54 (ICAM) antibody, nor was it blocked when galactosyl or mannosyl pyranosides were added. KG1a binding was trypsin sensitive and enhanced in the presence of neuraminidase. These studies serve to characterize adhesive properties of normal and leukemic myeloid progenitors and begin to establish interactions important for the lodgement of early progenitor cells in human marrow.

Phenotypic characterization of the human fibrous histiocytoma giant cell tumor (GCT) cell line and its cytokine repertoire.

The pleiotropic nature of malignant fibrous histiocytomas (MFH) is manifested as mixed cellular infiltrates consisting of myofibroblasts, histiomonocytes, and neutrophils. We detail in this report the phenotypic characteristics of the human fibrous histiocytoma giant cell tumor (GCT) cell line that establish its mesenchymal origin. The latter is underscored by the ability of GCT cells to express mRNA for transforming growth factor beta (TGF-beta) as well as both A and B chains of platelet-derived growth factor (PDGF). GCT cells also support the binding of CD34+ cells, but less efficiently than do normal marrow stromal cells. Since cytokines elaborated by MFH may mediate in part the recruitment of monocytes and neutrophils into tumor-infiltrated tissues, we have determined the cytokine repertoire of the GCT cell line, already known for its ability to elaborate colony-stimulating factors (CSFs) and interleukin-1 (IL-1). GCT cells express IL-1 alpha, IL-1 beta, IL-6, macrophage colony-stimulating factor (M-CSF or CSF-1), granulocyte-macrophage colony-stimulating factor (GM-CSF), granulocyte colony-stimulating factor (G-CSF), and IL-8. No detectable mRNA for IL-3, IL-4, IL-7, and tumor necrosis factor-alpha (TNF-alpha) was detected in GCT cells by polymerase chain reaction (PCR). Expression of cytokine mRNAs was responsive to agents such as dexamethasone (dex), 12-O-tetradecanoyl phorbol 13-acetate (phorbol diester or TPA), and TNF-alpha. Thus, this cell line provides a useful model for understanding the pathobiology of MFH and hematopoietic progenitor interactions with mesenchymal/stromal cells.

An 80,000-kd glycoprotein cell surface antigen found only on nonhematopoietic cells in human bone marrow.

The murine IgG2a monoclonal antibody (MoAb) 6-19 binds to the surface of human nonhematopoietic cells but not to hematopoietic cells. As previously described, it can be used with complement to selectively kill nonhematopoietic cells prior to culture of human bone marrow. It is now shown that the 6-19 MoAb recognizes a specific antigenic determinant of apparent molecular mass 80 kd, detected by western blotting on nonhematopoietic tumor cell lines, endothelial cells, and bone marrow stromal cells. Mouse L cells were transfected with human DNA, and the 6-19 monoclonal antibody selected cells that expressed an antigen with similar characteristics. The antigenic determinant is absent in hematopoietic tumor cell lines, peripheral blood cells, and bone marrow hematopoietic cells. Investigation of the biochemical nature of the antigen, using various enzymes, lectin-binding studies, and western blotting suggests that the 6-19 epitope is at least partially carbohydrate and that the protein has N-linked sugars but not O-linked. The affinity (Ka approximately 10(9) M-1) of MoAb 6-19 binding is similar in tumor cells and normal fibroblasts and endothelial cells. The identification of a specific antigenic determinant of 80 kd may help to discriminate between hematopoietic and nonhematopoietic cells in human bone marrow.

State of the art; the hypereosinophilic syndromes.

Many disease states such as parasitic infestations, malignancies, collagen vascular diseases, and allergies are associated with eosinophilia. The diagnosis of idiopathic hypereosinophilic syndrome (HES) requires a persistent elevation in the total eosinophil count (greater than 1500/mm3) for over 6 months, associated organ damage and no detectable underlying cause. This review provides an updated summary of the cytokine cascade that controls eosinophil production and delineates our current understanding of the clinical features of hypereosinophilic states. We also examine the central role of T-lymphocyte activation in eosinophilia, and have attempted to integrate current treatment strategies for HES with the physiology of eosinophilopoiesis.

Granulocyte-macrophage colony-stimulating factor (GM-CSF) and granulocyte colony-stimulating factor (G-CSF): receptor biology, signal transduction, and neutrophil activation.

Granulocyte-macrophage colony-stimulating factor (GM-CSF) and granulocyte colony-stimulating factor (G-CSF) are two of the growing number of recognized cytokines involved in the regulation of hematopoiesis. The purification of these factors and the subsequent cloning of the cDNAs which encode these proteins have led to their widespread clinical use in the setting of therapy or disease-induced myelosuppression. Although originally purified on the basis of their colony-stimulating properties, GM-CSF and G-CSF may also play important roles in the regulation of effector cell function. The mechanisms underlying progenitor cell proliferation and effector cell stimulation remain poorly understood. However, the characterization of the GM-CSF and G-CSF receptors and recent work in signal transduction are helping to elucidate these mechanisms. This paper will review the biology of the GM-CSF and G-CSF receptors, the mechanisms of post-receptor signal transduction, and the resultant effects on neutrophil function. In addition, the current and potential clinical uses of these factors will be examined in light of their ability to activate and perhaps enhance the function of neutrophils.

Mechanisms of cytopenia in human immunodeficiency virus infection.

Human immunodeficiency virus (HIV) infection often has effects on the hematopoietic system which can be distinguished from the concurrent effects of medications or opportunistic infections. Exactly how the virus mediates these effects remains uncertain, but both in vivo and in vitro studies have pointed up possible direct and indirect modes of hematopoietic suppression. Whether a significant fraction of CD34+ cells in vivo are infected with HIV remains controversial, but most studies using in situ polymerase chain reaction techniques would suggest not. Other more indirect modes of hematopoietic cell suppression such as production of autoantibodies, production of other humoral inhibitory factors, T-cell mediated suppression of hematopoiesis, or production of inhibitory or stimulatory cytokines may also be contributory. It is probable that several of these mechanisms may occur simultaneously, and an increased understanding of their role may lead to improved strategies to correct the cytopenias which often accompany HIV disease.