Biomedical subjects

G Bruchelt

Publications and source records attributed to G Bruchelt.

79 records · Page 5Linked to original sources

PubMedDate not supplied

Inhibition of the membrane localization of p21 ras proteins by lovastatin in tumor cells possessing a mutated N-ras gene.

Mutated ras genes are found in a variety of human tumors. For biological activity the gene product p21 ras needs to be bound to the cell membrane by a farnesyl residue. Treatment of tumor cells with lovastatin reduces the availability of farnesyl pyrophosphate for the modification of the ras proteins. The membrane localization of p21 ras has been reduced by 30-36% after the tumor cells have grown in the presence of 10 microM lovastatin for 7 days. The extent of the inhibition depends on the growth kinetics of the cell lines.

Acute Disease↗

PubMedDate not supplied

Effect of amifostine on neuroblastoma during high dose chemotherapy: in vivo and in vitro investigations.

Amifostine (Ethyol, WR-2721) has been clinically used in combination with high dose therapy of neuroblastoma stage 4 with melphalan, carboplatin and VP-16 in 14 patients. The amifostine group was compared to a historical control group of 24 comparably-treated patients. There were no significant differences regarding the time of hematological recovery, the duration of hospitalization, the duration of antibiotic treatment and the extent of renal toxicity. However, in contrast to four patients of the control group, no patient in the amifostine group developed such severe mucositis that artificial ventilation became necessary. Pretreatment of neuroblastoma cell lines for 30 minutes with amifostine and the free thiol(WR-1065) did not reduce the cytotoxic effects of melphalan, carboplatin and VP-16. Evidence was obtained that the uptake of the activated thiol could be achieved by a polyamine transporter. Taken together, the data do not support the use of amifostine in high dose chemotherapy of neuroblastoma prior to autologous stem cell transplantation. However, amifostine may be more effective in conventional neuroblastoma therapy where protection of bone marrow stem cells is necessary.

Amifostine↗

PubMedDate not supplied

Ascorbic acid induces lipid peroxidation on neuroectodermal SK-N-LO cells with high endogenous ferritin content and loaded with MAb-ferritin immunoconjugates.

Neuroblasma-and other malignant cells often contain elevated amounts of iron-rich ferritin and H2O2 and may therefore be a potential target for pro-oxidative effects of ascorbic acid (AA), generating cytotoxic products e.g. by lipid peroxidation (LPO). The influence of H2O2 and iron, either in its free form or bound to ferritin, on AA induced LPO was first investigated using erythrocyte ghosts as a model system. Results of these experiments showed that AA induced LPO not only in the presence of free available iron but also in the presence of ferritin. Similarly, AA induced significant LPO in neuroectodermal SK-N-LO cells with elevated intracellular ferritin levels. These LPO promoting effects of ferritin in the presence of AA on SK-N-LO cells could also be observed using ferritin-immunoconjugates: for this purpose, ferritin was bound to human monoclonal antibodies (MAb-ferritin) recognizing ganglioside GD2 which is present in large quantities on cell surfaces of SK-N-LO and many neuroblastoma cells. We conclude that the pro-oxidative effects of AA could be exploited in the treatment of ferritin rich neuroblastoma in combination with chemotherapy or with MAb-ferritin immunoconjugates.

Antibodies, Monoclonal↗

PubMedDate not supplied

Uptake and cytotoxicity of ascorbic acid and dehydroascorbic acid in neuroblastoma (SK-N-SH) and neuroectodermal (SK-N-LO) cells.

Ascorbic acid (AA) was found to be cytotoxic to neuroblastoma cells in vitro and in vivo. In the present, study we investigated whether the reduced--(AA) or oxidized form (dehydroascorbic acid, DhAA) and its rapidly formed metabolites were the main cytotoxic agents. In neuroblastoma SK-N-SH cells, AA was found to be more cytotoxic than DhAA, although considerably higher amounts of [14C]DhAA than of [14C]AA were incorporated. In contrast, SK-N-LO cells derived from neuroectodermal tissue in fact showed a similar uptake but were much less injured by both substances. We observed that uptake of [14C]AA and [14C]DhAA was impaired in the presence of dithiothreitol and glutathione. Once inside the cell, [14C]DhAA was partially reduced to [14C]AA. From these data we conclude first that at least part of AA is oxidized prior to its uptake, and second that the reduced form of AA and perhaps ascorbyl radicals but not DhAA or its metabolites are the most important forms in mediating cytotoxic reactions in neuroblastoma cells. Furthermore, the results strengthen the previous assumption that AA acts as a pro-oxidant in neuroblastoma cells and supports its use in the treatment of neuroblastoma, especially in combination with existing chemotherapeutics.

Ascorbic Acid↗

PubMedDate not supplied

Effects of cyclophosphamide and ifosfamide on neuroblastoma cells before and after activation by microsomes.

Cyclophosphamide (CP) and Ifosfamide (IF) are of great importance in the therapy of neuroblastoma (NB). They are prodrugs which have to be activated by microsomes in order to become active compounds. We established a test system which allowed the activation of CP and IF by liver microsomes in the presence of NB cells. The data from these experiments showed that neuroblastoma cells (SK-N-SH, SK-N-LO and IMR-5) were unable to activate CP and IF, but in the presence of rat liver microsomes considerable cytotoxicity was achieved, similar to those of the preactivated derivatives maphosphamide (MP) and 4-hydroxy-ifosfamide (4-OH-IF). Compared to other compounds the final metabolite acrolein contributes significantly to the cytotoxicity of CP and IF, obviously through significant lowering of the glutathione levels in the cells. The incubation system as described allows the rapid determination of the cytotoxicity of CP and IF in the simultaneous presence of microsomes. The results show great differences in the sensibility of NB cells toCP and IF.

Animals↗

PubMedDate not supplied

Cholesterol based antineoplastic strategies.

Manipulation of cholesterol metabolism open several possibilities of interfering with the growth of malignant cells. Deprivation of cholesterol decreases the velocity of growth and alters the composition of the cell membrane. The high requirement for LDL of malignant cells can be utilized for drug targeting. Proliferation assays were performed with neuroblastoma cells and cell lines of acute myeloid leukemia deprived of cholesterol by inhibition of HMG-CoA-reductase or culture in LDL-deficient medium. The cholesterol content of the cell membrane when reduced to 50% had no effect on the toxicity of LAK-cells but the toxicity of the fluorescent dye merocyanine MC 540 was enhanced two-fold. LDL-mediated drug targeting to AML cells was performed with oxidized LDL and showed toxic reactions. These results proved that cholesterol deprivation could be used to support some therapeutic approaches.

Anticholesteremic Agents↗

PubMedDate not supplied

Cytotoxic effect of immunoconjugate composed of glucose-oxidase coupled to an anti-ganglioside (GD2) antibody on spheroids.

As a new treatment protocol for neuroblastoma, the chimeric (human/mouse) antiganglioside GD2 antibody chl4.18 is being clinically tested. To improve the therapeutic effect of the antibody alone, we are currently investigating the cytotoxicity of glucose-oxidase coupled to the antibody chl4.18 on spheroids of the neuroblastoma cell line SK-N-LO. The cytotoxic effect of glucose-oxidase is achieved by the production of hydrogenperoxide (H2O2) and probably by the following reaction of H2O2 with iron to form hydrogen radicals (OH.). The cytotoxicity of glucose-oxidase was measured by two viability tests (MTT and WST 1). After a 4 hour treatment of the spheroids with the immunoconjugate, a reduction of viability to 50% (MTT-test) and 25% (WST 1-test), respectively, was obtained. The difference between the results of these two tests, might be explained by the different measurement protocols.

Antibodies, Monoclonal↗