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Biomedical subjects

J Harb

Publications and source records attributed to J Harb.

At least 19 recordsLinked to original sources
PubMed2005

Outbreak of cyclosporiasis in British Columbia associated with imported Thai basil.

Sporadic outbreaks of cyclosporiasis, a common cause of protracted diarrhoea in underdeveloped countries, are often undetected and undiagnosed in industrial countries. In May 2001, an outbreak of Cyclospora cayetanensis gastroenteritis was identified in British Columbia, Canada, with 17 reported cases. We conducted a case-control study involving 12 out of the 17 reported and confirmed case patients. Eleven (92%) of the patients had consumed Thai basil, an essential ingredient in Vietnamese cuisine, compared to 3 out of 16 (19%) of the control patients (P = 0.003). Trace-back investigations implicated Thai basil imported via the United States as the vehicle for this outbreak. This is the first documented sporadic outbreak of cyclosporiasis linked to Thai basil in Canada, and the first outbreak of cyclosporiasis identified in an ethnic immigrant population. This outbreak provides the opportunity to increase our understanding of this emerging pathogen and improve on our prevention and control for future outbreaks.

Adult↗
PubMed2001

Identification of BARD1 as mediator between proapoptotic stress and p53-dependent apoptosis.

The BRCA1-associated protein BARD1 is a putative tumor suppressor. We suggest that BARD1 is a mediator of apoptosis since (1) cell death in vivo (ischemic stroke) and in vitro is accompanied by increased levels of BARD1 protein and mRNA; (2) overexpression of BARD1 induces cell death with all features of apoptosis; and (3) BARD1-repressed cells are defective for the apoptotic response to genotoxic stress. The proapoptotic activity of BARD1 involves binding to and elevations of p53. BRCA1 is not required for but partially counteracts apoptosis induction by BARD1. A tumor-associated mutation Q564H of BARD1 is defective in apoptosis induction, thus suggesting a role of BARD1 in tumor suppression by mediating the signaling from proapoptotic stress toward induction of apoptosis.

Animals↗
PubMed2000

Identification of an apoptotic cleavage product of BARD1 as an autoantigen: a potential factor in the antitumoral response mediated by apoptotic bodies.

We have shown previously that rats can be cured from induced peritoneal colon carcinomatosis by injections of apoptotic bodies derived from tumor cells and interleukin 2. This curative treatment generated a tumor-specific cytotoxic T-cell response associated with a humoral response. Autoantibodies from sera of cured rats strongly recognized a Mr 67,000 protein from apoptotic bodies and weakly reacted with a protein of Mr approximately 97,000 in PROb parental cells. We now show that these autoantibodies are directed against BARD1, originally identified as a protein interacting with the product of the breast cancer gene 1, BRCA1. We demonstrate that the Mr 67,000 antigen is a cleaved form of BARD1 present in apoptotic bodies derived from rat and human colon and mammary carcinoma cell lines. Moreover, we show that the cleavage site of BARD1 is located NH2 terminally but downstream of the RING domain essential for BARD1 and BRCA1 protein interaction. In vitro studies using [35S]methionine-labeled human BARD1 and apoptotic cellular extracts derived from SW48 carcinoma cells indicate that BARD1 proteolysis occurs at an early stage of apoptosis and in a cell cycle-dependent manner. This hydrolysis is inhibited by EGTA, and the calpain inhibitor I, N-acetyl-leu-leu-norleucinal, but not by several caspases inhibitors, suggesting that BARD1 is hydrolyzed by the calcium-dependent cysteine proteases, calpains. Thus, the highly immunogenic form of cleaved BARD1 could contribute to the antitumoral response mediated by apoptotic bodies.

Amino Acid Sequence↗
PubMed1999

Production and characterisation of a monoclonal antibody specific for apoptotic bodies derived from several tumour cell lines.

We have recently shown that apoptotic bodies (apobodies) derived from rat colon carcinoma cell lines (PROb) after sodium butyrate (NaB) treatment were able to cure rats with induced peritoneal carcinomatosis ( [BOISTEAU] ). A specific immune response was assumed to be involved since the serum of cured rats contained antibodies specific for apobodies. In the present study, a mAb (clone 6E8) produced by immunisation of rats with apobodies strongly recognized apobodies but had little reactivity with parental tumour cell lines, as demonstrated by enzyme-linked immunosorbent assay (ELISA), immunostaining and flow cytometry. Immunoelectron microscopy showed that 6E8 mAb mainly stained the hyaloplasm or cytosol of apobodies. A protein was detected at 67 kDa by immunoprecipitation of apobodies with mAb, followed by immunoblotting, using serum of rats immunised with apobodies. The 6E8 mAb recognized apobodies derived from several rat or human colon cancer cell lines and a rat glioma cell line, regardless of the apoptosis stimulus used (NaB, staurosporine or UV). Our results clearly show that 6E8 mAb defines an epitope specifically generated during apoptosis, which suggests that the protein recognized may be involved in the molecular cascade of apoptotic cell death.

Animals↗
PubMed1997

Apoptosis induced by sodium butyrate treatment increases immunogenicity of a rat colon tumor cell line.

We have recently demonstrated that a treatment combining the cell differentiating agent sodium butyrate (NaBut) and interleukin-2 (IL2) resulted in a remission of established peritoneal colorectal carcinomatosis in rats. NaBut or IL2 treatment alone, never cured these tumour-bearing rats. In the present investigation, we report that NaBut-treatments induce apoptosis in the colonic cancer cells both in vitro and in vivo. We postulated that the significant therapeutic effect of NaBut/IL2 treatment can be mainly attributed to a NaBut-induced apoptosis of the tumoural cells increasing their immunogenicity. Indeed, treatment which combined apoptotic bodies (apobodies) as cell vaccine, plus IL2 immunotherapy significantly increased tumour remission and survival rate of the vaccinated rats, whereas IL2 treatment alone did not. We observed that the cured rats presented long-term protection against subsequent challenge with the parental tumour cells. This latter result suggests that these treatments generate an immune protection. This was confirmed by the presence, in the sera of the cured rats, of anti-tumoural antibodies directed against both the apobodies and the tumour cells, but not against normal colonocytes. In addition, we show that injections of apobodies before administration of the parental tumour cells results in a partial protection. We provide the first evidence that apobodies, derived from cancer cells after NaBut-treatment, induce a specific immune response against parental tumours cells. These data suggest that the distinctive immunologic properties of apobodies could provide a valuable tool in colorectal cancer immunotherapy.

Journal Article↗
PubMed1996

Induction of fibroblast gelatinase B expression by direct contact with cell lines derived from primary tumor but not from metastases.

During cancer progression, tumor cells interact with stromal cells. As a consequence, matrix metalloproteinases are produced that contribute to the degradation of the extracellular matrix. This study used coculture systems to investigate fibroblast interaction with three colon cancer cell lines isolated from a single patient. Cells from primary colorectal carcinoma, but not from corresponding liver or lymph node metastases, induced gelatinase B expression by fibroblasts of different tissue origin. Remarkably, direct cell-cell contact was required for this induction, which occurred at the pretranslational level (as revealed by Northern blot analysis) and was completely blocked by anti-beta1 integrin monoclonal antibody, but only partially blocked by anti-alpha5 or anti-alpha(v). Induction was also inhibited by cytochalasin D, staurosporine, or dexamethasone, suggesting the need, respectively, for an organized actin cytoskeleton, protein kinase C, and AP-1-driven gene transcription. Our data suggest that direct tumor-stromal cell contact is one inductive event involved in matrix metalloproteinase expression by stromal cells.

Animals↗
PubMed1996

Spontaneous, persistent infection of a B-cell lymphoma with adenovirus.

An adenovirus culture-positive lymphoblastoid cell line was derived from a bone marrow transplant recipient with fatal B-cell lymphoproliferative disease and adenovirus pneumonia. At autopsy, focal areas of the lymphoma infiltrating the patient's lung were positive for adenovirus proteins by immunohistochemical staining. The Epstein-Barr virus-transformed B-cell line Mk, established from pleural fluid cells, contained adenovirus virions in both the nucleus and the cytoplasm by electron microscopy. The majority of Mk cells expressed adenovirus proteins and produced a high level of infectious adenovirus by plaque assay analysis. However, in contrast to the rapid cell death induced by adenovirus in other permissive cell lines, Mk was maintained stably in tissue culture for 6 months. These data indicate that adenoviral replication is not sufficient for cell lysis and confirm that adenovirus can cause persistent infection in human lymphoid cells in vivo.

Adenoviridae Infections↗
PubMed1996

Altered glycosylation of alpha(s)beta 1 integrins from rat colon carcinoma cells decreases their interaction with fibronectin.

Malignant cell transformation is generally accompanied by changes in their interactions with environing matrix proteins in a way to facilitate their migration and generate invasion. Our results show the binding of rat colon adenocarcinoma PROb cells to fibronectin strongly reduced when compared to normal rat intestine epithelial cells. This decrease was not due to the level of alpha(s)beta 1 integrins expressed at the surface of the cell line. However, beta 1- and alpha(s)-associated subunits appeared to be structurally altered as shown by immunoprecipitation followed by electrophoresis. Pulse chase experiments using 35S methionine evidenced differences in the biosynthesis of beta 1- and alpha(s)associated integrins: normal epithelial IEC18 cells required 16 h for maximal biosynthesis of the completely mature beta 1 subunit, while PROb cells did it within 4-6 h. Studies using endoglycosidases O, H, D, and N glycanase confirmed that the molecular weight alterations were due to abnormal glycosylation and suggested that alpha(s)beta 1 integrins of PROb cells could bear both mature complex and immature high mannose types while IEC18 cells borne only mature complex type oligosaccharidic chains. Treatment of both cell types with castanospermine, an inhibitor of N-glycosylation, reduced the differences observed in their adhesion to the fibronectin without significantly affecting beta 1 receptors expression at the cell surface. These results strongly suggest a role of the glycosylation of beta 1 receptors in the adhesion of rat colon adenocarcinoma PROb cells to fibronectin substrata.

Animals↗
PubMed1996

[Modulation of integrin alpha-v-beta-1 expression on human tumor cells by leukemia inhibitory factor (LIF) and oncostatin M (OSM)].

Integrins belong to a large family of heterodimeric membrane glycoproteins which mediate cell-cell or cell-extracellular matrix interactions. These interactions could play a major role during the migration of tumor cells across the extracellular matrix and vascular endothelium and would thus appear to be a requisite for the metastatic process. Treatment of the Foss human melanoma cell line with LIF or OSM, two cytokines involved in acute-phase response, increased the expression of membrane alpha v beta 1 by 1.5-2 fold. The same phenomenon was observed on the SK-N-SH human neuroblastoma cell line. This modulation, which was inhibited by specific monoclonal antibodies against alpha v or beta 1 integrin subunits, was concomitant with improved tumor cell attachment to the fibronectin matrix. Similar results were obtained after TNF-alpha treatment. Our findings demonstrate the ability of LIF and OSM to modulate tumor cell capacity to adhere to the matrix component, suggesting a potential role for these cytokines in modulation of tumoral progression.

Antineoplastic Agents↗
PubMed1995

Upmodulation of alpha v beta 1 integrin expression on human tumor cells by human interleukin for DA cells/leukemia inhibitory factor and oncostatin M: correlation with increased cell adhesion on fibronectin.

Integrins belong to a large family of heterodimeric membrane glycoproteins which mediate cell-cell or cell-extracellular matrix interactions. These interactions could play a major role during the migration of tumor cells across the extracellular matrix and vascular endothelium and would thus appear to be requisite for the metastatic process. Pretreatment of the Foss human melanoma cell line with HILDA/LIF or OSM, two cytokines involved in acute-phase response, increased the expression of membrane alpha v beta 1 1.5-2-fold. The same phenomenon was observed on the SK-N-SH human neuroblastoma cell line. alpha v beta 1 upmodulation was concomitant with improved tumor cells attachment to the fibronectin matrix. This greater adhesion of tumor cells to fibronectin was inhibited by specific monoclonal antibodies against alpha v or beta 1 integrin subunits. Similar results were obtained after TNF-alpha treatment. Our findings demonstrate the ability of HILDA/LIF and OSM to modulate tumor cell capacity to adhere to the matrix component, suggesting a potential role for these cytokines in modulation of tumoral progression.

Cell Adhesion↗
PubMed1995

Human interleukin for DA cells/leukemia inhibitory factor and oncostatin M enhance membrane expression of intercellular adhesion molecule-1 on melanoma cells but not the shedding of its soluble form.

ICAM-1-mediated cell-cell adhesion is essential for different immunologic functions including non-MHC-restricted cytotoxicity. The shedding of a soluble form of ICAM-1 from melanoma impairs immune recognition and leads to tumour escape. Pretreatment of the Foss human melanoma cell line with HILDA/LIF or OSM, two cytokines involved in acute-phase response, increased the expression of membrane ICAM-1 twofold without inducing sICAM-1 shedding. Conversely, TNF-alpha, in the same conditions, strongly stimulated membrane ICAM-1 expression and the shedding of the soluble form. The same phenomenon was observed on the A375 human melanoma cell line. ICAM-1 upregulation was concomitant with an increase in the non-MHC-restricted cytotoxicity of tumour cells mediated by LAK cell.s This higher sensitivity to LAK lysis was abolished by RR1/1, a specific monoclonal antibody against ICAM-1. Our results demonstrate for the first time the ability of HILDA/LIF and OSM to upregulate ICAM-1 expression on the melanoma cell surface, suggesting a potential role for these cytokines in human immune surveillance during tumour progression.

Binding Sites↗
PubMed1995

[Identification of spermatozoa L-selectin and two potential pellucida ligands].

At the molecular level, gamete interactions partly depend on zona pellucida-glycoproteins fucosylation. We show, by immunocytochemistry, the sialyl-lewisx and sialyl-lewisa oligosaccharides on human zonae pellucidae. These epitopes are potential ligands of cell adhesion molecules named selectins which are known to play a role in endothelium-leukocyte interactions. By immunofluorescence, we find the leukocyte selectin (L-selectin) on the spermatozoa head. Preincubation of spermatozoa with an anti-L-selectin monoclonal antibody produces a significant inhibition of zona pellucida tight binding, under hemizona assay conditions. In contrast, preincubation of the zonae pellucidae with anti-sialyl-lewisx or anti-sialyl-lewisa antibodies does not produce a significant inhibition of spermatozoa binding. Western blot analysis of spermatozoa-detergent extracts revealed a band at approximatively 90 kDa with the anti-L-selectin monoclonal antibody. This spermatozoa selectin could play a role in human spermatozoa-zona pellucida binding. Zona-ligands have yet to be precisely defined.

Blotting, Western↗
PubMed1994

An interleukin 2/sodium butyrate combination as immunotherapy for rat colon cancer peritoneal carcinomatosis.

BACKGROUND/AIMS: Immunotherapy using interleukin 2 has had disappointing results in the treatment of colon cancer. Overcoming escape mechanisms, such as lack of antigen presentation and absence of accessory adhesion molecules on cancer cells, may increase its efficiency. We tried to do so by modifying the phenotype of the weakly immunogenic rat colon cancer PROb cells with sodium butyrate. METHODS: After in vitro treatment with butyrate, PROb cells were tested for lymphokine-activated killer cell sensitivity and, using cytofluorometry, expression of adhesion molecules. We then treated established PROb peritoneal carcinomatoses with intraperitoneal injections of interleukin 2 and butyrate. Tumors were studied histologically and immunohistochemically. We tested the specificity of the immune protection by subsequent subcutaneous challenges with either PROb or glioma cells and by Winn's assay. RESULTS: Butyrate increased lymphokine-activated killer cell sensitivity and expression of major histocompatibility complex class I and intercellular adhesion molecule 1 in vitro. Interleukin 2/butyrate combination resulted in cases of complete cure of carcinomatosis with specific protection against PROb cells. We noticed a complex stroma reaction with numerous functional antigen presenting cells close to PROb cells. CONCLUSIONS: The complete regression of tumor masses may be attributed, at least in part, to a butyrate-induced increase in immunogenicity of the cancer cells. This new combined immunotherapy may be of interest in the treatment of colon cancer.

Adenocarcinoma↗