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Biomedical subjects

Rolf Larsson

Publications and source records attributed to Rolf Larsson.

At least 55 records · Page 3Linked to original sources
PubMed2002

Ligatoxin B, a new cytotoxic protein with a novel helix-turn-helix DNA-binding domain from the mistletoe Phoradendron liga.

A new basic protein, designated ligatoxin B, containing 46 amino acid residues has been isolated from the mistletoe Phoradendron liga (Gill.) Eichl. (Viscaceae). The protein's primary structure, determined unambiguously using a combination of automated Edman degradation, trypsin enzymic digestion, and tandem MS analysis, was 1-KSCCPSTTAR-NIYNTCRLTG-ASRSVCASLS-GCKIISGSTC-DSGWNH-46. Ligatoxin B exhibited in vitro cytotoxic activities on the human lymphoma cell line U-937-GTB and the primary multidrug-resistant renal adenocarcinoma cell line ACHN, with IC50 values of 1.8 microM and 3.2 microM respectively. Sequence alignment with other thionins identified a new member of the class 3 thionins, ligatoxin B, which is similar to the earlier described ligatoxin A. As predicted by the method of homology modelling, ligatoxin B shares a three-dimensional structure with the viscotoxins and purothionins and so may have the same mode of cytotoxic action. The novel similarities observed by structural comparison of the helix-turn-helix (HTH) motifs of the thionins, including ligatoxin B, and the HTH DNA-binding proteins, led us to propose the working hypothesis that thionins represent a new group of DNA-binding proteins. This working hypothesis could be useful in further dissecting the molecular mechanisms of thionin cytotoxicity and of thionin opposition to multidrug resistance, and useful in clarifying the physiological function of thionins in plants.

Amino Acid Sequence↗
PubMed2002

Action of a novel anticancer agent, CHS 828, on mouse fibroblasts: increased sensitivity of cells lacking poly (ADP-Ribose) polymerase-1.

We observed stronger cytotoxic effect of CHS 828 on poly(ADP-ribose) polymerase-1(PARP-1) knock-out cells as compared with the normal counterpart. The proliferation of PARP-1 -/- cells was inhibited by a drug concentration approximately 3-fold lower than that in the normal cells. The monitoring of p53 levels revealed that CHS 828 induced p53 response in a dose-dependent manner in only normal cells. The drug, however, failed to activate the p53 protein in PARP-1-deficient cells even after combined treatment with multidrug-resistant modulators. These results show that the PARP-1 inactivation sensitizes cells to the novel anticancer drug CHS 828 and that the drug is able to activate different cellular pathways depending on PARP-1 status.

Animals↗
PubMed2002

C3 adsorbed to a polymer surface can form an initiating alternative pathway convertase.

Contact between blood and a biomaterial surface induces an immediate complement-mediated inflammatory response. Under these conditions, the alternative pathway of complement is often initiated and amplified on the biomaterial surface. Adsorption of a protein such as C3 to a polymer surface induces conformational changes in the protein. Based on the expression on adsorbed C3 of conformational neoepitopes specific for bound C3 fragments, we have hypothesized that adsorbed C3 is able to bind factor B and form a functional C3,Bb convertase. Using a quartz crystal microbalance to monitor binding of proteins to a polymer surface, we have demonstrated that a functional C3-containing alternative pathway convertase can be formed, in particular, in the presence of properdin. These data indicate that adsorption of C3 induces conformational changes that turn C3 into a C3b-like molecule that is able to participate in the functioning of the alternative convertase, and they suggest a new mechanism for complement activation on a biomaterial surface.

Adsorption↗
PubMed2002

Modulation of pyridyl cyanoguanidine (CHS 828) induced cytotoxicity by 3-aminobenzamide in U-937 GTB cells.

The role of the nuclear enzyme poly(ADP-ribose) polymerase (PARP) and the ADP-ribosylation inhibitor 3-aminobenzamide (3-ABA) in the cytotoxicity induced by the novel antitumoral cyanoguanidine CHS 828 was investigated in the human lymphoma cell line U-937 GTB. Exposing cells to CHS 828 and 3-ABA in combination resulted in a 100-fold higher IC(50) compared to exposure to CHS 828 alone. CHS 828 did not activate PARP, measured as PARP-activity and formation of poly(ADP-ribose). The ATP-levels and levels of extracellular acidification rate of cells exposed to CHS 828 in combination with 3-ABA were maintained for a longer period than for cells exposed to CHS 828 alone. To characterize the mode of cell death, caspase-3 activity and gross morphology were assessed. 3-ABA increased and delayed the caspase-3 activity in cells exposed to CHS 828. Cells exposed to high concentrations of CHS 828 showed a necrotic morphology, while high concentrations of CHS 828 in combination with 3-ABA switched the mode of cell death, generating an apoptotic morphology. The results indicate that the cytotoxicity and morphology induced by CHS 828 is not due to PARP activation but can be modulated by the ADP-ribosylation inhibitor 3-ABA.

Antineoplastic Agents↗
PubMed2002

In vitro evaluation of the efficacy of idarubicin in human tumour cells from patients with low-grade non-Hodgkin's lymphoma.

Evaluating the potential benefit of the new anthracycline, idarubicin (Ida), in lymphoma, 58 tumour samples from patients suffering from low-grade non-Hodgkin's lymphoma (L-NHL), were analysed in vitro for their sensitivity to 0.5 microg/ml Ida. This was compared with the sensitivity to other anthracyclines (0.5 microg/ml), using the fluorometric microculture cytotoxicity assay. A total of 132 samples from patients with acute leukaemia and a cell-line panel representing different resistance mechanisms was included for comparison. The median cell survival of L-NHL cells did not differ after exposing the cells to Ida or daunorubicin (Dnr), whereas epirubicin, doxorubicin (Dox) and mitoxantrone (Mitox) were significantly less cytotoxic than Ida (P < 0.001). The median cell survival in L-NHL cells did not differ from that of acute leukaemia cells after exposure to 0.5 microg/ml Ida, Dnr, Dox and Mitox. Cells from previously treated patients with L-NHL had a higher median survival than cells from untreated patients after exposure to all drugs, except for Ida. In samples from previously untreated patients, Spearman rank correlations were high (Rho = 0.81-0.90) between cell survival after exposure to Ida and the other anthracyclines. The same pattern was observed in the cell-line panel (Rho = 0.78-0.91) (P < 0.05). In contrast, low correlations (Rho = 0.24-0.42) were observed among samples from previously treated patients. Our results indicate a potential benefit of Ida in previously drug-treated patients with L-NHL.

Adult↗
PubMed2002

Coagulation, fibrinolysis, and cell activation in patients and shed mediastinal blood during coronary artery bypass grafting with a new heparin-coated surface.

OBJECTIVES: Heparin coating of the cardiopulmonary bypass circuit is shown to improve the biocompatibility of the surface. We have studied a new heparin surface, the Corline Heparin Surface, applied to a complete set of an extracorporeal device used during coronary artery bypass grafting in terms of activation of inflammation, coagulation, and fibrinolysis in patients and in shed mediastinal blood. METHODS: Sixty patients scheduled for coronary artery bypass grafting were randomized to one of 3 groups with heparin-coated devices receiving either a standard, high, or low dose of systemic heparin or to an uncoated but otherwise identical circuit receiving a standard dose of systemic heparin. Samples were drawn before, during, and after the operation from the pericardial cavity and in shed mediastinal blood. No autotransfusion of shed mediastinal blood was performed. RESULTS: The Corline Heparin Surface significantly reduced the activation of coagulation, fibrinolysis, platelets, and inflammation compared with that seen with the uncoated surface in combination with a standard dose of systemic heparin during cardiac surgery with cardiopulmonary bypass. Both a decrease and an increase of systemic heparin in combination with the coated heparin surface resulted in higher activation of these processes. A significantly higher expression of all studied parameters was found in the shed mediastinal blood compared with in systemic blood at the same time. CONCLUSIONS: The Corline Heparin Surface used in cardiopulmonary bypass proved to be more biocompatible than an uncoated surface when using a standard systemic heparin dose. The low dose of systemic heparin might not be sufficient to maintain the antithrombotic activity, and the high dose resulted in direct cell activation rather than a further anti-inflammatory and anticoagulatory effect.

Aged↗
PubMed2002

Interactions between the new cytotoxic drug CHS 828 and amiloride and mitomycin C in a human tumour cell line and in tumour cells from patients.

BACKGROUND: CHS 828 is a novel cyanoguanidine with cytotoxic properties which was recently shown to induce an early increase in extracellular acidification. This could hypothetically be exploited for combination with drugs interfering with, or being dependent on, pH for their effect. METHODS: The isobole method and the additive model were used to evaluate the combinations CHS 828-amiloride and CHS 828-mitomycin C (MMC) in the lymphoma cell line U-937 GTB and in primary cultures of tumour cells from patients. RESULTS: Amiloride, which blocks the Na(+)/H(+) antiport, shifted the CHS 828 dose-response curve to the left in a synergistic manner according to the additive interaction model. MMC is a bioreductive drug with enhanced cytotoxicity at acidic pH. A lowering of pH induced by CHS 828 would theoretically create a favourable environment for bioreduction of MMC. The interaction between these drugs was mainly classified as additive by both methods, but was synergistic at the highest effect level tested. In addition, there were sub-additive to synergistic interactions between CHS 838 and MMC in 76% of the haematological samples tested. CONCLUSIONS: Circumstantial evidence indicated that the mechanisms for the interactions could be pH independent. Thus, the interaction between CHS 828 and amiloride was synergistic while the interaction between CHS 828 and MMC in tumour cells was at least additive.

Amiloride↗
PubMed2002

Selective cytotoxicity evaluation in anticancer drug screening of fractionated plant extracts.

Chosen to reflect biodiversity in a phylogenetic sense, 100 fractionated plant extracts were screened in vitro for cytotoxicity following extraction and fractionation (polypeptide isolation). Of these 100 extracts, 30 were selected and then characterized preliminarily for antitumor potency and mode of action by testing them on two cell lines and primary cultures of human tumor cells. On the basis of cytotoxicity potency, 10 of the extracts were further characterized for anticancer activity in 10 human tumor cell lines. This final testing resulted in seven potential lead plants with superior evidence of antitumor potential: Colchicum autumnale L. (Colchicaceae), Digitalis lanata Ehrh. and Digitalis purpurea L. (Plantaginaceae), Helleborus cyclophyllus Boiss. (Ranunculaceae), Menyanthes trifoliata L. (Menyanthaceae), and Viola arvensis Murr. and Viola patrinii Ging. (Violaceae). Within a database of antitumor compounds, the activity profiles of the extracts from these seven plants were compared, by correlation analysis, with those of more than 100 other compounds, including 39 standard drugs from different classes of cytotoxic mechanisms. The activity profiles of six of these candidates were uncorrelated with those of the standard drugs, possibly indicating new pathways of drug-mediated cell death.

Antineoplastic Agents, Phytogenic↗
PubMed2002

CHS 828 inhibits neuroblastoma growth in mice alone and in combination with antiangiogenic drugs.

CHS 828 is a new chemotherapeutic drug, a pyridyl cyanoguanidine. CHS 828 has low toxicity and lacks known patterns of multidrug resistance. Here we report that oral, daily treatment with CHS 828 reduced the growth of SH-SY5Y human neuroblastoma tumors in male NMRI nu/nu mice by 82% without apparent toxicity. CHS 828 induced complete tumor regression for at least 5 weeks in four of nine animals (44%). Combination therapy with CHS 828 and the antiangiogenic drugs TNP-470 or SU5416 decreased neuroblastoma growth by a further 10 and 3%, respectively. Combination therapy induced tumor regression at d 4 with CHS plus TNP and d 6 with CHS plus SU5416, compared with d 14 with CHS 828 alone (p < 0.05), and complete tumor regression was seen in nine of 19 animals (47%). Combination treatment of CHS 828 and TNP-470 decreased the total viable tumor volume by 71% compared with treatment with CHS 828 alone. Our findings support CHS 828 as a promising new drug in treatment of childhood cancers. Furthermore, they imply efficiency of daily administration of nontoxic doses of chemotherapy, and a possible additive effect when chemotherapy is combined with angiogenesis inhibitors.

Angiogenesis Inhibitors↗
PubMed2002

Selection of chemotherapy by ex vivo assessment of tumor sensitivity to cytotoxic drugs: results of a clinical trial.

The feasibility of tumor sampling followed by ex vivo assessment of drug sensitivity, using the short-term fluorometric microculture cytotoxicty assay (FMCA), for selection of chemotherapy was investigated prospectively in patients with advanced cancer not amenable to standard treatment. Taxol (175 mg/m2 every 3 wk) was given to patients with tumor samples being low drug resistant (LDR) to Taxol ex vivo, to patients with no LDR drug, and if other drugs were unsuitable. The remaining patients received the most optimal drug(s) based on the FMCA results. Gastrointestinal cancer was dominating among the 61 eligible patients. Tumor sampling was safely performed in 75% by ultrasound-guided core biopsy. Eighty-two percent of the patients had Taxol. Five patients (8%) had a partial remission and 18 (30%) had stable disease. Tumor response was poorly predicted, probably because the Taxol excipient Cremophor EL is cytotoxic exclusively ex vivo. However, patients with tumor cells being LDR to at least one drug ex vivo lived significantly longer than those with no such drug.

Adolescent↗
PubMed2002

Inhibition of thrombin abrogates the instant blood-mediated inflammatory reaction triggered by isolated human islets: possible application of the thrombin inhibitor melagatran in clinical islet transplantation.

A thrombotic/inflammatory reaction is elicited when isolated islets of Langerhans come in contact with ABO-compatible blood. The detrimental effects of this instant blood-mediated inflammatory reaction (IBMIR) provide a reasonable explanation for the observation that an unexpectedly high number of islets, from several donors, are needed to produce normoglycemia in transplant patients with type 1 diabetes. In this study, the hypothesis that a specific thrombin inhibitor, Melagatran, could reduce IBMIR in an in vitro model in which human islets are exposed to ABO-compatible blood was tested. The administration of Melagatran abrogated IBMIR dose-dependently. Islets exposed to blood, in the absence or presence of 0.4 micromol/l Melagatran, exhibited a loss of integrity and were found to be trapped in macroscopic clots containing platelets and CD11b(+) leukocytes. At concentrations from 1 to 10 micromol/l, Melagatran inhibited both coagulation and complement activation. Also, platelet and leukocyte activation and consumption were decreased. Islet morphology was maintained with almost no platelets adhering to the surface, and infiltration by CD11b(+) leukocytes was considerably reduced. In conclusion, Melagatran significantly reduced IBMIR in this model system. This protective effect indicates that thrombin plays a pivotal role in IBMIR and suggests that thrombin inhibition can improve the outcome of clinical islet transplantation.

ABO Blood-Group System↗
PubMed2002

A Phase I study of CHS 828 in patients with solid tumor malignancy.

CHS 828 is a cyanoguanidine, which has demonstrated potent antitumor activity in preclinical tumor models. The activity of CHS 828 in vitro showed only low to moderate correlation to other antineoplastic agents suggesting a unique mechanism of action. Ten females and 6 males (median age 58 years) with solid tumors refractory to standard therapy were included in this Phase I study. The study drug was administered to fasting patients as a single oral dose on days 1-5 of each treatment cycle. Patients received one to six cycles of treatment. The doses ranged from 30 mg to 200 mg (total dose within a cycle). Hematological toxicity was generally mild and dominated by transient thrombocytopenia and lymphocytopenia. Nonhematological toxicity most frequently consisted of nausea, vomiting, diarrhea, fatigue, and localized genital mucositis. The dose-limiting toxicities were thrombocytopenia, thrombosis, esophagitis, diarrhea, and constipation. The recommended Phase II dose of CHS 828 was 20 mg once daily for 5 days in cycles of 28 days duration. The extent of systemic exposure of CHS 828 across patients was approximately dose proportional. The time at which the highest drug concentration occurs was 2.2 +/- 1.3 h and half-life was 2.1 +/- 0.52 h (mean +/- SD). Large intra- and interindividual variation in dose level-adjusted maximum plasma concentration and the area under the curve from time 0 h to infinity were observed. There was an apparent inverse relationship between systemic exposure of CHS 828, and thrombocyte and lymphocyte nadir levels. No objective tumor responses were observed, and 7 patients showed stable disease after two courses of therapy.

Administration, Oral↗
PubMed2002

Cyclotides: a novel type of cytotoxic agents.

Cytotoxic activities of three naturally occurring macrocyclic peptides (cyclotides) isolated from the two violets, Viola arvensis Murr. and Viola odorata L., were investigated. A nonclonogenic fluorometric microculture assay was used to examine cytotoxicity in a panel of 10 human tumor cell lines representing defined types of cytotoxic drug resistance. Additionally, primary cultures of tumor cells from patients, and for comparison normal lymphocytes, were used to quantify cytotoxic activity. All three cyclotides, varv A, varv F, and cycloviolacin 02, exhibited strong cytotoxic activities, which varied in a dose-dependent manner. Cycloviolacin 02 was the most potent in all cell lines (IC50 0.1-0.3 microM), followed by varv A (IC50 2.7-6.35 microM) and varv F (IC50 2.6-7.4 microM), respectively. Activity profiles of the cyclotides differed significantly from those of antitumor drugs in clinical use, which may indicate a new mode of action. This, together with the exceptional chemical and biological stability of cyclotides, makes them interesting in particular for their potential as pharmacological tools and possibly as leads to antitumor agents.

Amino Acid Sequence↗
PubMedDate not supplied

A new antibody recognizing the vIII mutation of human epidermal growth factor receptor.

The epidermal growth factor receptor (EGFR) gene is frequently amplified and the receptor overexpressed in different types of human tumors. Furthermore, genomic rearrangements can cause expression of modified receptors, as one frequently occurring truncated form, EGFRvIII. This mutated receptor has previously been described and is formed by a 267-amino acid in-frame deletion and an insertion of a glycine in the fusion junction of the extracellular domain. EGFRvIII is a tumor-specific marker and therefore of interest for diagnostic and therapeutic applications. In this study we report on a new monoclonal antibody (Ua30:2) directed to the mutation site of EGFRvIII. The antibody was generated by immunization of mice with a synthetic peptide corresponding to the mutated sequence of the receptor. The affinity of Ua30:2 was found to be high [K(d) = 45 nM (Biacore) and 80 nM (saturation analysis)]. Immunohistochemistry in tissue sections from human gliomas demonstrated a similar expression pattern for Ua30:2 as for the recently characterized antibodies L8A4 and DH8.3. The antibody binding was EGFRvIII specific with no measurable cross-reactivity to the wild-type receptor, wtEGFR, as analyzed both with displacement analysis, Western blots and immunohistochemistry. The new antibody is a candidate for radioimmunotargeting aiming at diagnostic and therapeutic applications.

Amino Acid Sequence↗
PubMedDate not supplied

Metabolic effects of the cytotoxic guanidino-containing drug CHS 828 in human U-937 lymphoma cells.

N-(6-(4-chlorophenoxy)hexyl)-N'-cyano-N''-4-pyridylguanidine, CHS 828, is a new anti-neoplastic agent with promising anti-tumor activity both in vitro and in vivo. To characterize the metabolic events over time, the lymphoma cell line U-937 GTB was exposed to CHS 828 and the structurally related mitochondrial inhibitor meta-iodobenzylguanidine (MIBG). There was an instant stimulation of the extracellular acidification rate in response to CHS 828 as measured by the Cytosensor microphysiometer. MIBG shared this metabolic feature. During the first 24 hours of CHS 828 exposure, the consumption of glucose was not significantly affected, but was thereafter shut off. CHS 828 exposure induced a slight increase in lactate production, with 114% of control after 8 hours and 126% for MIBG. Only limited cytotoxicity from CHS 828 exposure was observed after 24 hours and ATP levels remained at 65% of control. Thereafter, the ATP level decreased rapidly and subsequently cell death appeared. Thus, the CHS 828-induced increase in metabolic activity was associated with increased lactate production, probably from increased glycolytic activity. However, CHS 828 also appears to induce a late inhibition of glucolysis leading to energy depletion and subsequent cell death.

3-Iodobenzylguanidine↗
PubMedDate not supplied

Cytotoxic activity of a new lipid formulation of doxorubicin in cell lines and primary tumor cells.

BACKGROUND: Liposomal formulations of the anthracyclines are being developed to circumvent toxicity and prolong effect. The current study investigates the in vitro activity of a novel doxorubicin micelle formulation, containing a vehicle designed to release pharmacologically active subcomponents. MATERIALS AND METHODS: The cytotoxicity of doxorubicin formulated in a vehicle containing C4 (N-docosahexaenoyl-O-phospho-2-aminoethanol) and C11 (N-all trans-retinoyl-O-phospho-L-tyrosine) was measured in a panel of human tumor cell lines, 19 primary cultures of human tumor cells and 5 lymphocyte preparations. RESULTS AND CONCLUSION: At the tested ratio between doxorubicin and C4/C11 (1:50), C4/C11 contributed significantly to the in vitro toxicity. However, the molar EC50-values were lower for doxorubicin than for C4/C11. Synergistic interactions between doxorubicin and C4/C11 were evident in a majority of the cell types studied. C4/C11 increased the cellular load of the fluorescent Pgp substrate calcein. To further investigate the possible benefits of the new formulation, in vivo studies are ongoing.

ATP Binding Cassette Transporter, Subfamily B, Mem↗
PubMedDate not supplied

Identification and evaluation of potential anti-cancer drugs on human neuroendocrine tumor cell lines.

UNLABELLED: The aim of this study was to investigate drug sensitivity in neuroendocrine tumor cell lines. MATERIALS AND METHODS: In vitro drug sensitivity screening was performed using the fluorometric microculture cytotoxicity assay in one human pancreatic carcinoid and two human bronchial carcinoid cell lines. In addition, a normal human retinal pigment epithelial cell line was used for comparison. A total of 18 drugs with different mechanisms of action were tested. RESULTS: The most active agents were brefeldin A, emetine, bortezomib and idarubicin, having IC5o values <1 microM in all four cell lines. In addition, the three tumor cell lines showed sensitivity for sanguinarine, Bayll-7085, mitoxantrone, doxorubicin, beta-lapachone, NSC 95397 and CGP-74514A. CONCLUSION: The cell lines were sensitive for several drugs acting in different ways, covering a broad spectrum of mechanisms of action. Some of these compounds may possibly be used in clinical trials and show therapeutic effect in patients with neuroendocrine tumors.

Antineoplastic Agents↗