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Biomedical subjects

C N Abboud

Publications and source records attributed to C N Abboud.

At least 37 records · Page 2Linked to original sources
PubMed1996

In situ use of suicide genes for cancer therapy.

Gene therapy has now become a standard experimental approach for treating cancers that have failed conventional therapies. As the understanding of the molecular nature of carcinogenesis develops, new approaches are being taken to directly target tumor cells, thus bypassing the difficulties of killing cells that are resistant to chemotherapy and radiation. One emerging gene therapy approach has been through the genetic modification of tumor cells with a suicide gene such as the herpes simplex virus thymidine kinase gene (HSV-TK) and ganciclovir (GCV) therapy. Death of tumor cells modified with the HSV-TK gene leads to killing of unmodified in situ tumor cells in a phenomenon termed the "bystander effect." The basis both for this effect and other gene therapy trials underway for the treatment of cancer will be discussed.

Cell Death↗
PubMed1996

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.

Animals↗
PubMed1995

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.

Clinical Trials as Topic↗
PubMed1995

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.

Antibodies, Monoclonal↗
PubMed1995

Patients > or = age 40 years undergoing autologous or allogeneic BMT have regimen-related mortality rates and event-free survivals comparable to patients < age 40 years.

To evaluate the safety and efficacy of marrow transplantation for older adults, the regimen-related mortality and event-free survival for patients > or = 40 years were compared with those for patients < 40 years. Of 148 consecutive patients receiving autotransplants for lymphoma or Hodgkin's disease, 70 were < 40 years and 78 were > or = 40 years at the time of transplant, including 40 who were > or = 50 years and 12 who were > or = 60 years. Eleven patients (16%) in the younger age group died from transplant-related complications compared with 4 (5%) in the older age group. The 4-year actuarial event-free survivals (EFS) for the younger and older age groups were 43% and 48%, respectively. After adjustment for covariates with prognostic significance, older age was marginally associated with improved event-free survival (P = 0.08). Of 92 consecutive patients undergoing allogeneic BMT during the same period, 62 patients were < 40 years and 30 patients were > or = 40 years, including 8 patients > or = 50 years, and 1 patient > 60 years. Non-relapse mortality (including deaths from GVHD) occurred in 28 of the younger patients (45%) and 9 of the older patients (30%). The 3-year actuarial EFS for the younger patients was 26% vs. 56% for the patients > or = 40 years (P = 0.057). However, this difference was mainly due to the higher proportion of patients with CML and early-stage leukemia in the older age group.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1994

Cytokine regulation of early human lymphopoiesis.

An in vitro culture system in which bone marrow-derived fibroblast-like cells support the growth of TdT+ colonies derived from CD34+/CD10- human bone marrow progenitor cells has recently been described. The regulatory role of cytokines during early B lineage commitment was investigated using this culture system. Expression of IL-7, a cytokine that induces proliferation of B cell precursors, was detectable in the adherent layer by PCR and bioassay. Lymphoid progenitor colonies were inhibited by neutralizing anti-IL-7 Ab, suggesting that IL-7 produced by the adherent layer was required even in the earliest recognizable stages of human B cell lymphopoiesis. IL-1 alpha, IL-4, and TNF-alpha inhibited lymphoid progenitor colonies in a dose-dependent fashion. Neutralizing Ab to IL-1 alpha, IL-4, or TNF-alpha did not increase lymphoid progenitor colonies, suggesting that inhibitory concentrations of these cytokines are not constitutively elaborated in the adherent layer. Recombinant Steel factor and IL-6 as well as neutralizing Abs to these cytokines did not significantly affect lymphoid progenitor colonies, arguing against an important role for these cytokines in early human B lymphopoiesis. These results indicate that IL-7 provided by the bone marrow microenvironment is a critical growth factor at the earliest recognizable stages of human lymphopoiesis. IL-1 alpha, IL-4, and TNF-alpha have been shown to indirectly stimulate release of myeloid growth factors. The inhibition of lymphopoiesis by these cytokines suggests a possible mechanism for the observed reciprocal relationship between lymphoid and myeloid supportive bone marrow microenvironments.

Adult↗
PubMed1994

Effects of GM-CSF on Ki67 expression and cell cycle traverse in acute myelogenous leukemia specimens and cell lines.

A new strategy in the treatment of acute myelogenous leukemia is to attempt to increase the growth fraction of clonal leukemic cells prior to administration of chemotherapeutic agents by the administration of hematopoietic growth factors. We have studied the effect of GM-CSF on the cell cycle status and Ki67 nuclear antigen expression of AML blasts in vitro. The effect of growth factors and stromal cell co-culture on Ki67 expression in leukemic cell lines was also examined. Neither stromal cell co-culture nor exposure of factor-dependent and factor-independent cell lines to GM-CSF, IL-3, SCF, or combinations thereof significantly changed the percentage of cells expressing Ki67. In the AML population analyzed as a whole, exposure of blasts to GM-CSF for up to 96 h did not significantly change the percentage of cells in S phase or expressing Ki67.

Antigens, Neoplasm↗
PubMed1994

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.

Anemia↗
PubMed1994

Integrins and adhesive receptors in normal and leukemic CD34+ progenitor cells: potential regulatory checkpoints for cellular traffic.

Multiple adhesion receptors are involved in the interaction of hematopoietic cells with the marrow microenvironment. This work characterizes the expression of various adhesive receptors on normal early hematopoietic precursors and reviews how they might be altered in leukemic states. Early hematopoietic CD34+ cells express CD18, CD11a, CD49d, CD49e, CD44, ICAM-1, and ICAM-3. Likewise, most AML samples express CD49d, CD49e, and CD44. In addition to mediating the adherence of progenitors to the marrow, these multiple receptors and their respective ligands may serve to regulate in vivo leukemic cell agrees from marrow and the ability of certain leukemic phenotypes to selectively seek extramedullary sanctuary sites such as the skin and the central nervous system.

Antigens, CD↗
PubMed1994

CD34+ progenitor cell isolation from blood and marrow: a comparison of techniques for small-scale selection.

The isolation and characterization of primitive hematopoietic cells and their purification in sufficient numbers is important in clinical and research marrow transplantation settings. As systems for large-scale isolation and amplification of such cells are developed, they may assume importance in transplantation, treatment of marrow failure and for gene therapy applications. Such cells have been isolated by numerous techniques and in this work, small-scale isolation of CD34+ cells by two immunoadsorption purification methods is compared with isolation by flow cytometry. While the immunoadsorption techniques allow for the processing of large numbers of density gradient-separated or unseparated cells for progenitor isolation, such techniques do not achieve the purity afforded by fluorescence activated cell sorter separation.

Antigens, CD↗
PubMed1994

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.

Antigens, CD↗
PubMed1993

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.

Animals↗
PubMed1993

Signal pathway regulation of interleukin-8-induced actin polymerization in neutrophils.

Interleukin-8 (IL-8), a recently described peptide cytokine, is a neutrophil chemoattractant and activator that exerts effects similar to fMLP, yet their receptors and their roles in pathophysiology differ. The effect of IL-8 on the neutrophil cytoskeleton has not been well studied; therefore, we compared and contrasted the effects of IL-8 and fMLP on neutrophil actin conformation and on the signal pathway regulation of actin responses. IL-8 caused a rapid, dose-dependent increase in neutrophil F-actin content within 30 seconds. The maximum increase was twofold. These changes were accompanied by the development of F-actin-rich pseudopods, as noted with fluorescence microscopy and scanning electron microscopy. Selected biochemical inhibitors were used to study the regulation of the IL-8-induced actin changes. Incubation of neutrophils with 2 micrograms/mL pertussis toxin resulted in a 67% inhibition of the IL-8-induced F-actin increase. The protein kinase C (PKC) inhibitors, staurosporine and H7, did not inhibit the increase in F-actin caused by IL-8. IL-8 caused a rapid increase in neutrophil intracellular calcium that could be completely inhibited by the chelating agent 1,2-bis(o-aminophenoxy)ethane-N,N-N',N'-tetraacetic acid (BAPTA). However, BAPTA-treated neutrophils retained the ability to increase F-actin in response to IL-8. Similar results were seen with fMLP, indicating that, similar to fMLP, the IL-8-induced actin response is mediated through pertussis-toxin-sensitive G-proteins but is neither dependent on PKC nor increases in cytosolic calcium. Thus, although IL-8 and fMLP exert their effects on neutrophils through different receptors, the signal transduction pathways used and the effects on actin conformation and pseudopod formation are similar.

Actins↗
PubMed1993

Expression of integrins and examination of their adhesive function in normal and leukemic hematopoietic cells.

Adhesion of hematopoietic progenitor cells to marrow-derived adherent cells has been noted for erythroid, myeloid, and lymphoid precursors. In this report, we have characterized very late antigen (VLA) integrin expression on normal CD34+ marrow progenitors, on leukemic cell lines, and on blasts from patients with acute myelogenous or monocytic leukemias. CD34+ progenitor cells expressed the integrin beta 1 chain (CD29), VLA-4 alpha (CD49d), and VLA-5 alpha (CD49e). The myeloid lines KG1 and KG1a also expressed CD49d and CD49e as did the Mo7e megakaryoblastic line. CD29, CD18, and CD11a were also present on each of these cell lines. Only the Mo7e line expressed the cytoadhesins GPIIbIIIa or GPIb. Binding of KG1a to marrow stroma was partially inhibited by antibodies to CD49d and its ligand, vascular cell adhesion molecule (VCAM-1). The majority of leukemic blasts studied expressed CD49d and CD49e as well. Blasts from patients with acute myelomonocytic leukemia consistently bound to stroma at levels greater than 20%, and adhesion to stroma could in some cases be partly inhibited by anti-CD49d. No role for glycosylphosphatidyl-inositol (GPI)-linked structures was demonstrated in these binding assays because the adhesion of leukemic blasts to stroma was not diminished after treatment with phosphatidylinositol-specific phospholipase C (PI-PLC). These studies indicate that CD34+ myeloid progenitors, myeloid leukemic cell lines, and leukemic blasts possess a similar array of VLA integrins. Their functional importance individually or in combination with other mediators of attachment in adhesion, transendothelial migration, and differentiation has yet to be fully elucidated.

Antibodies↗
PubMed1993

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.

Actuarial Analysis↗