Biomedical subjects

A Balsari

Publications and source records attributed to A Balsari.

At least 55 records · Page 3Linked to original sources

PubMed1996

Nerve growth factor controls proliferation and progression of human prolactinoma cell lines through an autocrine mechanism.

Two different human prolactinoma phenotypes (responders and nonresponders), which are distinguished by different tumorigenic potential and different responsiveness to dopaminergic therapy, have recently been identified. Responders show low proliferation rate, low tumorigenic potential, and expression of D-2 receptors for dopamine (DA), while nonresponders are characterized by high proliferation rate, high tumorigenic potential, and lack of expression of DA D-2 receptors. In this study it has been shown that both gp140trk and gp75 components of nerve growth factor (NGF) receptor are expressed in responder prolactinoma cell lines. High levels of both NGF gene transcript and protein were also found in responders, and biologically active NGF was detectable in the media conditioned by these cells. Ablation of NGF production in responder cells by hybridization arrest of translation through NGF antisense oligonucleotides resulted in: 1) loss of secreted NGF; 2) loss of expression of gp75; 3) loss of expression of DA D-2 receptors; and 4) a remarkable increase in the cell proliferation rate. These results thus suggest that a NGF-mediated autocrine loop essential to control cell proliferation and to preserve some phenotypical characteristics of mammotroph cells is present in responder prolactinoma cell lines. Analysis of nonresponders showed that these cells express gp140trk but no detectable levels of gp75. In addition, no NGF mRNA or protein was detectable in nonresponders. Exposure of these cells to NGF resulted in the permanent expression of NGF mRNA and in the production and secretion of NGF protein, thus establishing the same NGF-mediated autocrine loop present in responders. As a result, it has been shown that nonresponder cells treated with NGF acquire and maintain most of the phenotypic characteristics of normal mammotroph cells. In conclusion, the present work reports that a NGF-mediated autocrine loop with an inhibitory role in the control of cell proliferation and tumor progression is active in the more differentiated DA-sensitive prolactinoma cell lines and is lost in the most malignant prolactinoma cells refractory to the dopaminergic therapy. Alterations in the expression of this autocrine loop thus may lead to cell transformation and tumor progression.

Animals↗

PubMed1996

Tumor-necrosis-factor-induced fibroblast growth factor-1 acts as a survival factor in a transformed endothelial cell line.

Endothelial cells undergo apoptosis after withdrawal of growth factors, alterations in the extracellular matrix, or exposure to cytokines. Here we report that tumor necrosis factor (TNF)-alpha induces apoptosis of human endothelial cells derived from the umbilical vein in a dose-dependent fashion. Apoptosis is triggered through a pathway that is independent from the levels of Bcl-2. On the contrary, TNF stimulates the growth of spontaneously transformed human umbilical vein endothelial cells. This proliferative effect is mediated through the up-regulation of fibroblast growth factor-1 by TNF. The addition of specific fibroblast growth factor-1 antisense oligonucleotides inhibits TNF-induced fibroblast growth factor-1 expression, thus inhibiting the growth and triggering apoptosis of spontaneously transformed human umbilical vein endothelial cells.

Apoptosis↗

PubMed1996

Apoptosis of hair follicle cells during doxorubicin-induced alopecia in rats.

Alopecia is a common side effect of cancer chemotherapy, and to date, little progress has been made in alopecia prevention or treatment. The present studies were undertaken to topographically localize the site of injury in the hair follicle after doxorubicin (DXR) administration and to investigate the mechanism of DXR-induced alopecia. Tissue samples of head and proximal neck skin obtained from newborn rats treated with DXR were histologically examined by light and electron microscopy and stained by the terminal deoxynucleotidyl transferase-mediated deoxyuridine triphosphate nick-end labeling method. Light microscopy revealed pyknotic cells in the matrix and in the upper bulb and a decrease in the number of mitotic cells. Terminal deoxynucleotidyl transferase-mediated deoxyuridine triphosphate-digoxigenin nick-end labeling analysis evidenced cells with nuclear staining indicative of apoptosis, as confirmed by ultrastructural analysis. Kinetics studies indicated that even a single DXR treatment induced apoptosis and a decrease in mitotically active cells. Our data show that DXR treatment induces injury in a cell subset localized in the hair matrix. The successful prevention of drug-induced alopecia in patients may depend on the selective protection of these cells of the hair follicle.

Alopecia↗

PubMed1995

A monoclonal antibody extends the half-life of an anti-HIV oligodeoxynucleotide and targets it to CD4+ cells.

An approach was sought to increase the half-life and target cell specificity of antisense oligodeoxynucleotides (oligos). A monoclonal antibody (MAb) was derived from mice immunised with an oligo complementary to a region (1-20) of the HIV genome. This MAb exerts a protective effect on the oligo from the degradation induced by plasma exonucleases in vitro and in vivo. Moreover the anti-oligo MAb dissociates from the oligo in the presence of its complementary sequence to allow hybridization of the two complementary strands. To direct the oligo to CD4+ cells the anti-oligo MAb was cross-linked to an anti-CD4 MAb. The heteroaggregate determines a 5-fold increase in the cellular membrane binding of the oligo to CD4+ lymphocytes. These findings suggest a new approach to enhancing the therapeutic action and the target specificity of antisense oligodeoxynucleotides useful for the selective inhibition of HIV replication in vivo.

Animals↗

PubMed1995

The differential response to interferon gamma by normal and transformed endothelial cells.

Interferon gamma, a multifunctional cytokine secreted by activated T lymphocytes and NK cells, induces normal endothelial cell apoptosis which is inhibited by the activation of protein kinase C. Interestingly, interferon exerts a dual effect on transformed endothelial cell proliferation: at low concentrations it stimulates their growth, while at high concentrations it exerts an inhibitory effect. The different response of normal and transformed endothelial cells correlates with the levels of interferon receptor: when expressed at high levels--such as in normal cells--interferon promotes apoptosis; on the contrary, when cells possess a low number of receptors--such as transformed cells--the cytokine promotes cell growth. Since interferon induces it own receptor, we anticipate that transformed cells exposed to high doses of interferon may upregulate the receptor and, consequently, respond to the cytokine with a reduction in cell viability.

Apoptosis↗

PubMed1995

Nerve growth factor and bromocriptine: a sequential therapy for human bromocriptine-resistant prolactinomas.

Nerve growth factor (NGF) administration to athymic mice with transplanted human bromocriptine-resistant prolactinoma, results in the expression of dopamine D-2 receptors in the tumour and restores sensitivity to subsequent treatment with bromocriptine, which then produces normalisation of plasma prolactin and tumour regression. Sequential administration of NGF and bromocriptine thus may be a promising therapy for patients refractory to bromocriptine.

Animals↗

PubMed1995

A monoclonal antibody to the NH2-terminal region of human interferon-gamma inhibits its antiproliferative activity without affecting its internalization.

MAb IGMB-15, an anti-hIFN-gamma MAb, neutralizes the antiproliferative activity of hIFN-gamma without affecting that of hIFN-alpha or hIFN-beta. The neutralizing capacity of MAb IGMB-15 is wide: it has been assessed on cell lines whose origin and sensitivity to hIFN-gamma differ. The binding of hIFN-gamma to its receptor and its subsequent internalization into the target cell were not influenced by the antibody. MAb IGMB-15 has been found to interact with hIFN-gamma in solution but not when the lymphokine was associated with its cell surface receptor, showing that the growth of certain cell lines can be inhibited at the cell membrane level. This finding is consistent with the existence of an accessory factor responsible for the antiproliferative activity of hIFN-gamma.

Antibodies, Monoclonal↗

PubMed1994

Modulation of drug-induced cytotoxicity by a bispecific monoclonal antibody that recognizes the epidermal growth factor receptor and doxorubicin.

A hybrid hybridoma secreting a bispecific hybrid mAb (bsmAb), which recognizes both the epidermal growth factor receptor (EGF-R) and the drug doxorubicin, was produced by somatic hybridization of two hybridomas. The bsmAb obtained was able to retarget doxorubicin cytotoxicity in vitro specifically on EGF-R-positive cells exerting at the same time an antidotal effect on cells that did not overexpress the EGF-R. Distribution studies in mice indicate that the bsmAb selectively delivers the drug to tumour cells and modifies doxorubicin biodistribution with a statistically significant decrease of drug concentration in the intestine, which is the main target of early anthracycline toxicity. In keeping with this finding is the remarkable antidotal activity exerted by bsmAb in mice treated with doxorubicin, which is proved by retardation in loss of body weight and mortality. The effectiveness on tumour growth of the mAb followed by the administration of doxorubicin appears to be equal to that of the drug alone; however, the bsmAb exerts a remarkable antidotal activity.

Animals↗

PubMed1994

Effect of a bifunctional monoclonal antibody directed against a tumor marker and doxorubicin on the growth of epidermoid vulvar carcinoma grafted in athymic mice.

Even though the first monoclonal antibodies (MAbs) directed against tumor cells were produced 15 yr ago, the therapeutic application of immunoconjugates is still at the beginning. This is principally because of the enormous work that is required for the development of completely new therapeutic tools. An alternative could be to only use MAbs to improve conventional treatment such as chemotherapy. To this aim, a MAb directed against doxorubicin (DXR) was produced. DXR is an anthracycline antibiotic of which the clinical usefulness in cancer chemotherapy is limited by serious side effects, such as cardiomyopathy, bone marrow depression, and gastrointestinal tract mucositis. This toxicity was found to be reduced by treatment with the antidrug MAb, as shown by reduction in body weight loss and mortality of experimental mice. To improve the DXR therapeutic index, a bifunctional hybrid MAb (DOXER2), capable of simultaneously recognizing DXR and the epidermal growth factor (EGF) receptor, was produced. This reagent was found in vitro to increase the drug toxicity on the epidermoid carcinoma cell line A431, which overexpresses the EGF-R and, at the same time, to reduce DXR cytotoxicity on EGF-R negative cells. The effect of DOXER2 on the DXR biodistribution in vivo was also investigated. In mice previously injected ip with the DOXER2, the uptake of the drug, in comparison to the control group, was found to be reduced in the intestine and in myocardial tissue, and significantly increased in the tumor.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1994

Relevance of antibody valency in EGF receptor modulation.

Binding characteristics of a monovalent bispecific monoclonal antibody (bsMoAb), which recognizes both epidermal growth factor receptor (EGF-R) and drug doxorubicin (DXR) were compared with those of the parental bivalent MoAb directed against the EGF-R binding site. Scatchard analysis indicated that both MoAbs bound to EGF-R-overexpressing A431 cells with the same affinity. In tracer amounts, both MoAbs also displayed the same capacity to be internalized after binding to the cell surface. However, when the MoAbs were used at saturating concentrations, down-modulation of the receptor was greater with the bivalent MoAb. The bivalent MoAb also inhibited proliferation of A431 cells both in vitro and in vivo whereas the bsMoAb was inhibitory only in vivo. These data suggest that MoAb bivalency is required for EGF-R down-modulation and in vitro cell growth inhibition.

Animals↗

PubMed1994

Expression of CD28 on CD8+ and CD4+ lymphocytes during HIV infection.

CD28 interaction with B7 molecules, expressed on the membranes of antigen-presenting cells, co-stimulates cytokine production, T-cell proliferation and generation of cytotoxic lymphocytes. The expression of CD28 markers on CD4+ and CD8+ lymphocytes was studied in a group of subjects at various stages of HIV infection. A reduction in the percentage of CD28-bearing CD4+ and CD8+ cell subsets was observed during the asymptomatic stage of the disease. This reduction was more pronounced in AIDS than in non-AIDS patients. At the same time, an increase in the absolute CD8+CD28- cell number (greater in stage A than in stage B and C subjects) was observed in HIV-infected patients. The finding of an altered pattern of CD28 expression on T cells might per se explain certain early defects in the cytokine pattern and in the immune response peculiar to HIV-infected patients.

CD28 Antigens↗

PubMed1994

Nerve growth factor directs differentiation of the bipotential cell line GH-3 into the mammotroph phenotype.

GH-3 is an established cell line which, for the production of both PRL and GH, may be related to the bipotential somatomammotroph from which both somatotroph and mammotroph cells derive. In the present study we first report that GH-3 cells express both the gp140trk and the gp75 components of the nerve growth factor (NGF) receptor and that NGF dictates a nonneuronal type of differentiation of this cell line of ectodermal origin. After exposure to NGF, GH-3 cells markedly decreased their proliferation rate. This effect, which was maximal (50% inhibition) 3 days after beginning the treatment and was maintained during the following days of exposure, was paralleled by a change in the hormone production. The secretion of PRL was increased 6-fold, but that of GH was remarkably inhibited. Moreover, GH-3 cells expressed the mammotroph-specific D-2 receptor protein in response to NGF, as shown by binding with the D-2 receptor ligand N-(p-aminophenetyl)spiperone coupled to fluorescein. The present data thus show that NGF induces the differentiation of GH-3 cells into one of their physiological counterparts, the mammotroph cell, and together with the finding that NGF receptors are expressed in the anterior pituitary suggest a physiological role for the neurotrophic factor in pituitary ontogenesis.

Cell Differentiation↗

PubMed1993

Nerve growth factor suppresses the transforming phenotype of human prolactinomas.

The most effective therapy of human prolactinomas is represented by dopamine D-2 receptor agonists; there is, however, a population of nonresponder patients who require surgical intervention. In the present study, we report that prolactinomas totally resistant to pharmacological therapy have a high potential of both growing in soft agar and forming tumors in nude mice and lack D-2 receptors for dopamine. These tumors express the receptors for nerve growth factor (NGF) and are sensitive to its differentiating activity. After exposure to NGF for 4 days, prolactinoma cells decreased their proliferation rate, lost their capability to form colonies in soft agar, lost their tumorigenic activity in nude mice, and reexpressed the lactotroph-specific D-2 receptor protein inhibiting prolactin release. These effects were permanent after NGF withdrawal and were reproducible in vivo in nude mice transplanted with the tumors. NGF in fact remarkably and lastingly depressed tumor growth and induced expression of D-2 receptors when injected intravenously once a day for 5 days into prolactinoma-bearing nude mice. These data suggest that NGF may induce a long-lasting switch of gene expression in human prolactinomas, modifying their transforming phenotype and reverting them to more differentiated, less malignant, dopamine-sensitive lactotroph-like cells. The possibility thus arises that short-term treatment with NGF may restore the refractory patients to conventional pharmacological therapy with D-2 agonists.

Animals↗

PubMed1993

Purification of interleukin-2 antibodies from healthy individuals.

By covalent binding of recombinant interleukin-2 (rIL-2) to Sepharose, it was possible to immunopurify specific human anti-IL-2 antibodies from a pool of immunoglobulins obtained from healthy subjects. Since low quantities of the ligand released by the matrix could interfere with the evaluation of the biological activity of anti-IL-2 antibodies, the antibody preparation was subjected to pepsin digestion which is known to destroy the IL-2 molecule. Purified human anti-IL-2 antibodies were found to be mostly IgG1 and able to neutralize IL-2 induced peripheral blood lymphocytes (PBL) proliferation in vitro. The availability of purified anti-IL-2 antibodies, obtained from healthy individuals, able to modulate IL-2 activity, could be important in several therapeutic approaches.

Blotting, Western↗

PubMed1993

Expression of activation markers on peripheral-blood lymphocytes following oral administration of Bacillus subtilis spores.

This study was undertaken to assess the capability of Bacillus subtilis spores to modify the peripheral-blood lymphocyte (PBL) subsets or determine the de novo expression of activation markers. The data we obtained show that spores of B. subtilis are able to increase the expression of certain cell activation markers and that such activation is dose-dependent. In fact, doses of 2 x 10(9) spores did not give rise to changes in any of the parameters evaluated, while doses of 6 x 10(9) increased the HLA-DR antigen expression on T-lymphocytes. At the highest dosage used (12 x 10(9), B. subtilis spores caused the appearance of cells bearing the CD25 and CD71 activation markers. Therefore, such cell activation markers may prove useful for monitoring the activity of B. subtilis spores, and possibly of other immunomodulating agents, in the course of clinical research.

Administration, Oral↗

PubMed1993

The detection and biological activity of human antibodies to IL-2 in normal donors.

Antibodies to interleukin-2 (IL-2) have been reported in the sera of patients under therapies involving this cytokine and in the sera of patients infected with human immunodeficiency virus (HIV). Our study proves that auto-antibodies to IL-2 are present also, at a lower titre, in healthy individuals. These antibodies were affinity purified and studied for their capability to interfere with the in vitro biological activity of IL-2. Data obtained show that human anti-IL-2 antibodies can interfere with lymphocyte proliferation both in the lymphokine activated killer (LAK) cell assay and in the mixed lymphocyte reaction (MLR). However, the kinetics of inhibition by anti-IL-2 antibodies differs from LAK cell assay to MLR as the former are always inhibited in a time-independent manner, and the latter only by adding antibodies at the outset of culture. The neutralizing activity observed in vitro suggests that such antibodies play a part in the elaborate cytokine network by which the immune system regulates the amplitude and duration of its response.

Autoantibodies↗

PubMed1992

Natural human antibodies to gamma interferon interfere with the immunomodulating activity of the lymphokine.

Natural antibodies to gamma interferon (IFN-gamma) were found in patients suffering from different viral diseases and, at a lower titer, in healthy individuals. Such antibodies were affinity-purified and studied for their capability to interfere in vitro with the antiviral and immunomodulating activity of IFN-gamma. Data obtained show that these human anti-IFN-gamma antibodies have no inhibitory effect on the antiviral activity of IFN-gamma. On the contrary, they are able to inhibit the expression of Fc receptor sites and HLA-DR antigens induced by IFN-gamma on the U-937 cells, a human monocytoid/macrophage-derived cell line. These antibodies can also interfere in a mixed lymphocyte culture (MLC) with the proliferation of lymphocytes and the generation of cytotoxic lymphocytes. However, they showed only a moderate inhibitory effect on the cytotoxicity generated in MLC to K-562 cells. Human antibodies capable of interfering with the immunomodulating activities of IFN-gamma might open up a new field in clinical therapy for those diseases that carry evidence of activated cell-mediated immunity.

Animals↗

PubMed1992

An anti-doxorubicin monoclonal antibody modulates kinetic and dynamic characteristics of the drug.

A monoclonal antibody (MAb) directed against doxorubicin (DXR), denominated MAD II, was found to exert an antidotal action by modulating the kinetic and dynamic characteristics of the drug. In vitro, MAD II has been found to reduce the cytotoxicity of DXR and the drug uptake on spleen lymphocytes more efficiently than on tumor cells (P388 leukemia cells). In vivo, the anti-DXR MAb modified the drug distribution; the drug uptake was found to be reduced in the intestine and myocardial tissues and increased in the tumor, liver and spleen. In mice treated with DXR, the administration of anti-DXR MAb exerted an antidotal activity which was proved by the reduction in body-weight loss and mortality. In contrast, the therapeutic efficacy of the drug in P388-tumor-bearing mice was not influenced by the anti-DXR MAb.

Animals↗