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M Worm

Publications and source records attributed to M Worm.

At least 55 records · Page 3Linked to original sources
PubMed1998

Lymphotoxin-alpha is an important autocrine factor for CD40 + interleukin-4-mediated B-cell activation in normal and atopic donors.

Stimulation of human B cells with anti-CD40 + interleukin-4 (IL-4) results not only in proliferation and immunoglobulin E (IgE)-production, but also increased production of the cytokine lymphotoxin-alpha (LT-alpha) (formerly also known as tumour necrosis factor-beta (TNF-beta)). Here, we studied the role of LT-alpha (TNF-beta) in B cells following stimulation with anti-CD40 + IL-4 from normal versus atopic donors. Anti-CD40 + IL-4 stimulation of peripheral blood mononuclear cells (PBMC) from atopic donors resulted in enhanced production of soluble LT-alpha (TNF-beta) and increased membrane LT-alpha (TNF-beta) expression on the B cells compared with normal donors. Functional evaluation of LT-alpha (TNF-beta) in CD40 + IL-4-stimulated B cells shows that recombinant LT-alpha (TNF-beta) induces proliferation of B cells and enhances CD40 + IL-4-mediated B-cell proliferation and IgE synthesis in both normal and atopic donors in a dose-dependent manner. These findings were supported by semiquantitative analysis of epsilon-germline transcripts using reverse transcription-polymerase chain reaction (RT-PCR) showing increased epsilon-germline transcription in the presence of LT-alpha. Furthermore, addition of anti-LT-alpha (anti-TNF-beta) to CD40 + IL-4-stimulated B cells partially inhibited proliferation and IgE synthesis in a dose-dependent manner indicating a role of endogenous LT-alpha (TNF-beta) production by B cells during continued CD40 + IL-4 stimulation. These data suggest that LT-alpha (TNF-beta) plays a potentially significant role during B-cell proliferation and IgE synthesis. Moreover, LT-alpha (TNF-beta) production seems to be differentially regulated in B cells from normal and atopic donors.

Antibodies, Monoclonal↗
PubMed1997

Molecular regulation of human IgE synthesis.

Understanding the induction and regulation of IgE synthesis in human B cells is crucial to elucidate the molecular pathogenesis of IgE-dependent diseases. Experimental data, in part supported by clinical observations, suggests that IgE regulation is a complex process involving several cellular and molecular interactions. A two-signal model is accepted for the induction of IgE synthesis in human B cells. The first signal is provided by the cytokines interleukin 4 or 13, which are secreted by T cells, mast cells, and basophils. The second signal for the induction of IgE synthesis requires cell contact between T and B cells. Engagement of the B cell antigen CD40 by the CD40 ligand (CD40L) expressed on T cells leads to subsequent isotype switching during immunoglobulin synthesis in B cells. The CD40-CD40L interaction is well established as a key signal for the induction of isotype switching while the elucidation of the role of other cell-cell interactions, for example, through adhesion molecules, needs further study. An important counteracting cytokine for IgE synthesis is interferon (IFN) gamma which is produced mainly by T lymphocytes. Several cell-contact molecules, cytokines, and various hormones have been shown to modulate IgE synthesis in vitro, suggesting a complex network of molecular events to be involved in the production of IgE. However, the relevance of these factors for IgE production in vivo requires further elucidation. Here we describe the molecular mechanisms known to be involved in the induction and regulation of human IgE synthesis and discuss the role of various molecules during this process. Furthermore, evidence is presented that the understanding of IgE synthesis provides a potential key for new therapeutic strategies in patients with IgE mediated diseases including atopic dermatitis.

CD40 Antigens↗
PubMed1997

Upregulation of CD40 and CD40 ligand expression in IgE-associated cutaneous diseases.

In order to better understand the immunological processes connected with IgE-associated cutaneous disease, we have examined the expression of CD40 and its ligand CD40L, required for the induction of IgE synthesis in B-cells, as well as of IgE and its receptors in various dermatoses (atopic dermatitis (AD), scabies, chronic recurrent urticaria) versus normal skin, and in one dermopathic lymph node versus normal lymphatic tissue by immunohistochemistry. Compared to normal skin, cells expressing IgE, Fc epsilon RI, Fc epsilon RII, CD40, CD40L and L26 were increased in the dermis, partly also in the epidermis, from patients with AD and scabies, but not in chronic urticaria. CD40 and CD40L were detected on numerous cells in lymphatic tissue from both normal donors and a patient with AD, whereas large numbers of IgE- and Fc epsilon RI-positive cells were only found in the dermopathic lymph node from the AD patient, in contrast to very few in normal lymphatic tissue. These results with selectively increased IgE/Fc epsilon RI and associated CD40/CD40L expression in the skin of AD and scabies suggest that cutaneous tissue, in addition to dermopathic lymphatic tissue, might contribute to IgE synthesis.

Antigen Presentation↗
PubMed1996

Treatment of melanoma cells with the synthetic retinoid CD437 induces apoptosis via activation of AP-1 in vitro, and causes growth inhibition in xenografts in vivo.

Human malignant melanoma is notoriously resistant to pharmacological modulation. We describe here for the first time that the synthetic retinoid CD437 has a strong dose-dependent antiproliferative effect on human melanoma cells (IC50: 5 x 10(-6) M) via the induction of programmed cell death, as judged by analysis of cell morphology, electron microscopical features, and DNA fragmentation. Programmed cell death was preceded by a strong activation of the AP-1 complex in CD437-treated cells as demonstrated by gel retardation and chloramphenicol transferase (CAT) assays. Northern blot analysis showed a time-dependent increase in the expression of c-fos and c-jun encoding components of AP-1, whereas bcl-2 and p53 mRNA levels remained constant. CD437 also exhibited a strong growth inhibitory effect on MeWo melanoma cells in a xenograft model. In tissue sections of CD437-treated MeWo tumors from these animals, apoptotic melanoma cells and c-fos overexpressing cells were colocalized by TdT-mediated deoxyuridine triphosphate-digoxigenin nick end labeling (TUNEL) staining and in situ hybridization. Taken together, this report identifies CD437 as a retinoid that activates and upregulates the transcription factor AP-1, leading eventually to programmed cell death of exposed human melanoma cells in vitro and in vivo. Further studies are needed to evaluate whether synthetic retinoids such as CD437 represent a new class of retinoids, which may open up new ways to a more effective therapy of malignant melanoma.

Animals↗
PubMed1995

CD40-mediated lymphotoxin alpha expression in human B cells is tyrosine kinase dependent.

The cytokine lymphotoxin (LT)alpha is known to play a role in B cell activation. As the engagement of the B cell antigen CD40 is known to lead to B cell proliferation and differentiation, we studied LT alpha expression in human B cells after CD40 ligation. We demonstrate that anti-CD40 monoclonal antibody (mAb) induces strong LT alpha mRNA and surface-expression in human tonsil B cells. Induction of LT alpha mRNA and surface expression by CD40 ligation is inhibited by the protein tyrosine kinase (PTK) inhibitors herbimycin and genistein in a dose-dependent manner. The protein kinase C (PKC)-specific inhibitors sphingosine and bis-indolylmaleimide caused negligible inhibition of anti-CD40-induced LT alpha mRNA and surface expression. No inhibition is observed with the protein kinase (PKA) inhibitors H89 and HA1004. Cross-linking of the transmembrane phosphatase CD45 to CD40 by using goat-anti-mouse F(ab')2 fragments strongly inhibits CD40-mediated LT alpha expression in human B cells, confirming the role of PTK activation in CD40-mediated induction of LT alpha expression. Inhibitors of the serine/threonine protein phosphatases PP1 and PP2A, okadaic acid and calyculin induce LT alpha mRNA expression. In contrast, cyclosporin A, an inhibitor of the serine/threonine phosphatase calcineurin has no effect on anti-CD40-induced LT alpha expression. These results suggest that induction of LT alpha expression in B cells following engagement of CD40 involves activation of protein tyrosine kinases.

Antibodies, Monoclonal↗
PubMed1995

Effects of various synthetic retinoids on proliferation and immunophenotype of human melanoma cells in vitro.

Since response rates in human melanoma are low with currently available therapeutic modalities, we have reevaluated the potential usefulness of retinoids as new alternatives for therapy of metastatic melanoma. Nine synthetic retinoids with high affinity and/or selectivity for the retinoic acid receptors (RAR) alpha, beta, and gamma were studied in comparison to all-trans retinoic acid (RA) for their in vitro effects on melanoma cell proliferation and for their immunomodulating capacities using four human melanoma cell lines. Eight out of ten retinoids tested had no effect on melanoma cell growth, whereas the remaining two compounds with high RAR-gamma selectivity (CD437 and CD2325) showed a dose-dependent antiproliferative effect on all melanoma cell lines with IC50 (concentration inhibiting response by 50%) values between 10(-6) and 10(-7)M. Further analyses showed that paracrine-mediated tumor cell growth inhibition such as induction of transforming growth factor (TGF)-beta described as one mechanism of retinoid action and enzyme systems such as tyrosinase and monoamine oxidase were not involved in mediating the antiproliferative effects exerted by the two retinoids. Four of nine retinoids modulated HLA-DR expression on human melanoma cells, and expression levels of intercellular adhesion molecule 1 (ICAM-1) was increased by another subset of compounds. These effects were, however, not correlated to the receptor selectivity of the retinoids. The potent growth inhibitory effect of the RAR-gamma-selective retinoids and the immunomodulating capacities of the retinoids open an interesting alternative for new antiproliferative and immunomodulatory strategies in the treatment of metastatic melanoma.

Antigens, CD↗
PubMed1995

CD40-CD40 ligand (CD40L) interactions and X-linked hyperIgM syndrome (HIGMX-1).

Interactions between the B cell surface antigen CD40 and its ligand (CD40L) expressed on activated T cells play a critical role in isotype switching. This is illustrated by failure of isotype switching in patients with X-linked hyperIgM syndrome in whom the CD40L gene is mutated and by failure of isotype switching of CD40-deficient mice in response to T-cell-dependent antigens. We review these findings and discuss the signaling mechanisms of CD40 and the developmental control and transcriptional regulation of CD40L expression.

Animals↗
PubMed1995

Interferon-gamma downregulates epidermal growth factor receptors on human melanoma cells.

Unregulated expression of epidermal growth factor receptor (EGF-R) is a common event in neoplastic transformation and has been shown to be associated with melanocytic tumor progression. Modulation of such a receptor by pharmacological agents could therefore be of clinical interest. We have studied EGF-R expression, its response to epidermal growth factor (EGF) and modulation effects by interferon gamma (IFN gamma) on human melanoma cells. Addition of EGF, anti-EGF and anti-EGF-R antibodies had no effect on proliferation of six melanoma cell lines tested. We report in this communication that EGF-R expression on human melanoma cells can be modulated by IFN-gamma. In the melanoma cell lines treated with IFN gamma, proliferative behavior was not affected; however, we demonstrate a downregulation of EGF-R expression on the protein level, by immunohistochemistry and flow cytometric analysis, and an accumulation of EGF-R mRNA by Northern blot analysis. The results suggest that IFN gamma downregulates EGF-R expression at a posttranscriptional level on human melanoma cells. This EGF/EGF-R interaction and its modulation by IFN gamma on human melanoma cells needs to be further clarified regarding its in vivo significance for the treatment and prognosis of malignant melanoma.

Blotting, Northern↗
PubMed1994

Chemosensitivity testing of human malignant melanoma. A retrospective analysis of clinical response and in vitro drug sensitivity.

BACKGROUND: Clinical response rates in the treatment of patients with disseminated malignant melanoma are low and unpredictable. Several reports have documented that clonogenic assay systems for in vitro drug testing are capable of predicting resistance to therapy in vivo and might provide guidelines to improve clinical response rates. METHODS: Specimens from metastatic lesions of patients with malignant melanoma, predominantly from lymph nodes and skin, were disaggregated, exposed to a panel of 10 cytotoxic drugs for 1 hour, and subsequently cultured in agarose. Effects were calculated by the ability to form tumor colonies compared with an untreated control after 7-14 days. A retrospective comparison between the in vitro drug testing result and clinical response was possible in 19 cases. RESULTS: An average of 7.3 drugs per specimen were tested. A high degree of resistance was observed against all cytostatic agents studied independently of the tumor site. In 47 of 181 in vitro drug tests, tumor colony formation was reduced by 30-50%; in 17 of 181, the reduction was more than 50%. A retrospective analysis showed no clinical response in 11 cases and one mixed response in which patients received drugs that had been shown to be "resistant" in vitro. CONCLUSIONS: These results support the concept that in vitro drug testing promises to help avoid treatment with ineffective drugs and their associated toxic side effects. Furthermore, it may increase the likelihood of obtaining a clinical response in the treatment of disseminated malignant melanoma. The major limitation in the treatment of malignant melanoma is the lack of availability of effective agents for treatment.

Antineoplastic Agents↗
PubMed1994

Nerve conduction velocity in man: influence of glucose, somatostatin and electrolytes.

Insufficient metabolic control in diabetes mellitus is associated with a reversible reduction in nerve conduction velocity, but the mechanism behind this phenomenon is unknown. To examine the effect of acute hyperglycaemia on nerve conduction eight non-diabetic men (20-49 years of age) with no signs of peripheral neuropathy were studied before and after 3 h of hyperglycaemic clamping (plasma glucose approximately 15 mmol/l), while insulin secretion was suppressed by somatostatin [Study 1]. Nerve conduction velocity, as determined in the proximal part of the median nerve, fell by 2.8 +/- 3.0 m/s (2p-value: 0.033). However, during euglycaemic clamping (plasma glucose approximately 5 mmol/l) in five non-diabetic men (19-38 years of age) infused solely with somatostatin [Study 2], a comparable decrement in nerve conduction velocity was found (1.7 +/- 1.3 m/s, 2p-value: 0.043). In both studies relative hypoinsulinaemia was present. Serum-sodium decreased significantly (143 +/- 1 mmol/l vs 137 +/- 1 mmol/l [Study 1] and 143 +/- 1 mmol/l vs 142 +/- 2 mmol/l [Study 2]), while serum-potassium increased. In conclusion, the slight but significant reduction in nerve conduction velocity observed in both studies appears to be correlated to electrolyte changes. However, an effect of hypersomatostatinaemia or the hormonal changes associated with this cannot be excluded, while short-term hyperglycaemia per se seems to be without effect on nerve conduction velocity.

Adult↗
PubMed1994

Lysis of allogeneic and autologous melanoma cells by IL-7-induced lymphokine-activated killer cells.

In order to assess the potential of interleukin 7 (IL-7) as an immunotherapeutic agent in human melanoma, we have evaluated the in vitro activity of IL-7-induced lymphokine-activated killer (LAK) cells from patients with advanced melanoma against allogeneic and autologous melanoma cells. Peripheral blood lymphocytes (PBLs) from 14 patients with stage III melanoma were isolated and incubated in the presence of 1,000 U ml-1 IL-7 and 100 U ml-1 IL-2 for comparison. LAK-cell activity was determined by a 24 h cytotoxicity assay using MTT [3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide]. The activity of IL-7-induced LAK cells against two allogeneic melanoma cell lines was 32.7% (+/- 17.9) against SK-Mel-37 and 38.1% (+/- 12.5) against SK-Mel-23 at an effector-to-target (E/T) ratio of 20:1. The activity of IL-2-induced LAK cells was significantly higher against SK-Mel-37 (78 +/- 24.6%) and against SK-Mel-23 (73.5 +/- 19.7%). IL-7 and suboptimal doses of IL-2 (10 U ml-1) were found to have a co-stimulatory on lymphocyte proliferation as well as on LAK activity. Against autologous melanoma cells, the activity of IL-7- and IL-2-induced LAK cells did not differ significantly (55.8 +/- 25.6% versus 68.7 +/- 21.7% respectively). In two patients, IL-7-induced LAK-cell activity against autologous melanoma cells exceeded even that of IL-2 significantly (67% vs 35% and 95% vs 82%). Levels of tumour necrosis factor alpha (TNF-alpha) in the supernatants of LAK-cell cultures generated by IL-7 were lower than those of IL-2-generated LAK-cell cultures. These results suggest that IL-7 is a potential alternative to immunotherapy with IL-2 in terms of efficacy and possible side-effects and encourages pilot studies with IL-7 in melanoma patients.

Adult↗
PubMed1994

CD40 ligation induces lymphotoxin alpha gene expression in human B cells.

CD40 plays an important role in T cell mediated B cell proliferation and isotype switching. The cytokines tumor necrosis factor (TNF)-alpha and lymphotoxin (LT)-alpha are expressed by B cells, and are known to play a role in B cell activation. We have studied TNF-alpha and LT-alpha expression in human tonsillar B cells following stimulation with anti-CD40 mAb. Anti-CD40 induced weak TNF-alpha mRNA expression but strong LT-alpha mRNA expression and had little effect on the constitutive expression of LT-beta mRNA in B cells. Induction of TNF-alpha mRNA was inhibited by actinomycin D suggesting that CD40 ligation results in transcriptional activation of the TNF-alpha and LT-alpha genes. Anti-CD40 caused minimal increase in the expression of TNF-alpha on the B cell membrane and no detectable secretion of TNF-alpha. Anti-CD40 as well as soluble CD40 ligand caused sustained induction of LT-alpha on the membrane of the B cells lasting up to 120 h but induced no detectable secretion of LT-alpha. IL-4, a cytokine known to synergize with anti-CD40 in inducing B cell proliferation and isotype switching, augmented the induction of LT-alpha mRNA and of mLT-alpha expression by anti-CD40. These results indicate that CD40 ligation vigorously induces expression of membrane LT-alpha in B cells and that membrane LT-alpha may play a role in CD40 mediated B cell activation.

Antibodies, Monoclonal↗
PubMed1994

In vitro sensitivity of human melanoma cells to chemotherapeutic agents and interferons.

The purpose of our study was to evaluate systematically the anti-proliferative effects of eight chemotherapeutic drugs as well as of four recombinant interferons (IFNs) (alpha-2a, alpha-2b, beta, gamma). All drugs and IFNs were tested separately and in combination at several concentrations on four human melanoma cell lines using the 3-(4,5-dimethylthiazol-2-yl)-2,5,-diphenyltetrazolium (MTT) test. In all cases, drug inhibitory concentrations of chemotherapeutic agents required to kill 25% of melanoma cells (IC25) in vitro were in the range of the maximal achievable plasma peak level in vivo. Sensitivity to the anti-proliferative action of bleomycin, DTIC, doxorubicin, cisplatin and carboplatin was similar for all melanoma cell lines, whereas cell lines exposed to 5-fluorouracil (5-FU), vindesine and fotemustine differed up to 26-fold in their sensitivity. Studies with IFN showed that IFN-beta and IFN-gamma proved to be more antiproliferative than IFN-alpha in a dose-dependent fashion in all cell lines. However, the ability of IFNs to improve cytotoxicity of chemotherapeutic agents was limited. Pre-incubation of melanoma cells with IFN as well as exposure to IFN after incubation with the drugs showed mainly additive effects (231/256). These results confirm the high chemoresistance of human melanoma cells, independently of the drug chosen. Combinations of chemotherapeutic agents with IFN will provide additional therapeutic benefit, but are unlikely to change the overall high chemoresistance of human melanoma cells.

Antineoplastic Agents↗
PubMed1993

IL-8 produced by human malignant melanoma cells in vitro is an essential autocrine growth factor.

Normal melanocytes require a number of exogenous growth factors in contrast to most metastatic malignant melanomas. This investigation demonstrates that endogenously produced human IL-8 can act as an important growth factor for human melanoma cells. In the present study, six out of eight human melanoma cell lines tested secrete IL-8 protein into the culture supernatant. In two of these IL-8-secreting melanoma cell lines, SK-MEL 13 and SK-MEL 23, we have determined the IL-8 requirement for their proliferative capacity. These melanoma cell lines produced significant amounts of bioactive IL-8 as measured by the ELISA technique. Secretion of human IL-8 was inducible by IL-1 and by PMA. Human IL-8-specific mRNA was already detected in unstimulated melanoma cells. In addition, human IL-8-R mRNA could be detected for the first time in human melanoma cells. Exposure of the two melanoma cell lines in vitro to antisense oligonucleotides targeted against two different sites of human IL-8 mRNA-inhibited cell proliferation, colony formation in soft agar, and secretion of IL-8 protein into culture supernatant in a dose dependent fashion. Effects were reversible either by removal of the oligomers or by addition of exogenous IL-8 protein. In contrast, exposure to IL-8 sense probes or oligonucleotides in sense or antisense orientation specific for IL-7, TGF-alpha, TGF-beta, and MGSA had no such effect. A monospecific immune serum and two IL-8-specific mAb were also capable of inhibiting melanoma cell proliferation in the same manner. These results provide strong evidence for an autocrine IL-8 synthesis and for an IL-8-dependent proliferation in a subgroup of human melanomas. Furthermore, they suggest that IL-8 may play a role not only in immunomodulation but also in melanoma progression and metastatic spread.

Base Sequence↗
PubMed1993

Determination of granulocyte/macrophage-colony-stimulating factor secretion by human melanoma cells and its effects on human melanoma cell proliferation.

Recently, granulocyte/macrophage-colony-stimulating factor (GM-CSF) became available for overcoming chemotherapy-induced granulocytopenia. GM-CSF not only has a prominent role in the regulation of proliferation and differentiation of haematopoietic cells but it is also secreted by a variety of solid tumours and is capable of exerting growth-stimulatory effects. To evaluate the safety of GM-CSF administration in the treatment of malignant melanoma, we investigated GM-CSF secretion, GM-CSF receptor expression and the effect of GM-CSF on the proliferation of human melanoma cells in vitro. A panel of eight human melanoma cell lines and two fresh tumour specimen was studied. GM-CSF protein was not detectable in culture supernatants by ELISA without stimulation. Interleukin-1 and tumour necrosis factor alpha induced GM-CSF secretion in all four melanoma cell lines tested. When biotinylated GM-CSF was used, the corresponding receptor was not detectable by immunohistochemical or FACScan analysis. The proliferation of eight human melanoma cell lines and two fresh melanoma specimens was determined by the MTT test after 4-6 days of growth in the presence of different concentrations of GM-CSF (0.1-1000 U/ml). Neither proliferation nor growth inhibition was observed. Therefore the effect of GM-CSF on residual tumour cells in vivo may not present a problem during clinical use to stimulate marrow regeneration after or during chemotherapy of metastatic malignant melanoma.

Cell Division↗