Fas/CD95-mediated apoptosis in human glioblastoma cells: a target for sensitisation to topoisomerase I inhibitors

The expression of the death receptor Fas/CD95 is cell type-specific and can be modulated by different cytotoxic treatments. In spite of a frequent expression of Fas/CD95 in high-grade gliomas, these tumours are typically refractory to conventional therapy. Using a human glioblastoma cell line (GBM), we explored the possibility of modulating susceptibility to Fas/CD95-mediated apoptosis following cytotoxic treatment. GBM cells were sensitive to the antiproliferative effects of topoisomerase I inhibitors (topotecan and a novel lipophilic analog CPT83) and taxol, less sensitive to cisplatin and, in any case, rather resistant to drug-induced apoptosis. This pattern of cellular response was consistent with p53 mutation. GBM cells expressed low levels of Fas/CD95, which was associated with low susceptibility to antibody-stimulated Fas/CD95-mediated apoptosis. A significant up-regulation of Fas/CD95 expression was detected after exposure to topotecan and CPT83, whereas cisplatin induced a low increase and taxol did not modify Fas/CD95 expression. In addition, after treatment with topoisomerase I inhibitors, the up-regulation of Fas/CD95 resulted in an increased susceptibility of GBM cells to antibody-stimulated Fas/CD95-mediated apoptosis, while no synergistic effects were detected after treatment with cisplatin or taxol. Our data suggest that Fas/CD95 up-regulation can be a common response to DNA damage, whereas sensitisation to Fas/CD95-mediated apoptosis appears to be dependent on the type of DNA damage and on the pathway of cellular response. The observed effects might have important therapeutic implications for the design of novel therapeutic strategies in the treatment of malignant gliomas.     

Anisomycin activates JNK and sensitises DU 145 prostate carcinoma cells to Fas mediated apoptosis

Treatment of the hormone refractory prostate cancer cell line DU 145 with sublethal concentrations of chemotherapeutic drugs has been reported to sensitise these cells to Fas mediated apoptosis. However, the mechanism by which this occurs has not been determined. Our group has shown that inhibition of JNK activity completely abrogates the effects of chemotherapeutic drugs. Using anisomycin, a potent JNK agonist, we have demonstrated a role for JNK in Fas mediated apoptosis in DU 145 cells. Inhibition of Caspase 8 and Caspase 9 completely inhibits this process which suggests that DU 145 cells require mitochondrial amplification of the Fas apoptotic signal. Furthermore, we have shown that inhibition of Fas mediated apoptosis is an early event in DU 145 cells, occurring upstream of Caspase 8 cleavage. It is hoped that identifying the target of JNK will allow novel therapies to be developed for the treatment of hormone refractory prostate cancer. Such therapies are especially important because no single or combined treatment to date has significantly prolonged survival in patients with hormone refractory prostate cancer.     

流式细胞术检测化疗前后卵巢癌细胞凋亡的临床意义

目的：探讨化疗前后卵巢癌细胞及外周血淋巴细胞凋亡的因子Ｆａｓ、Ａｐｏ２．７的含量及其临床意义。方法：从７５例化疗前后卵巢癌患者的腹水中提取富含癌细胞的悬液,用Ａｎｎｅｘｉｎ Ｖ－ＦＴＴＣ／ＰＩ双染法分辨凋亡的亡细胞及坏死细胞及坏死细胞,并以两种凋亡因子克隆抗体Ｆａｓ和Ａｐｏ２．７标记上述细胞,均用流式细胞仪检测。结果：化疗后卵巢癌细胞凋亡率显著高于化疗前的临床疗效好,反之疗效差,被Ｆａｓ及Ａｐｏ２     

Influence of phenobarbital pretreatment on thein vitro ring a reduction of Δ4-3-oxo-steroids in rat liver microsomes

Summary The metabolism of 4-androstene-3,17-dione has been studied in rat liver microsomes. Treatment of the animals with repeated doses of phenobarbitalin vivo caused an enhanced rate of formation of 5-androstane-3,17-dione and of polar metabolites from this steroid. On the other hand, no significant increase was found in the 5-reductase activity present in the soluble cytoplasm after phenobarbital administration to the rats. Carbon monoxide and oxidized cytochrome c abolished the formation of polar metabolites from 4-androstene-3,17-dione but did not inhibit the 5-reductase activity. The present findings indicate that the hydroxylation and 5-reduction reactions, although both stimulated by phenobarbital treatment of the animals, do not involve common enzyme components.Supported by grants from the Swedisch Cancer Society, Swedish Medical Research Council (Project no. 13X-2525) and from Caroline Andriette Nobel's foundations for experimental medical research.     

Apoptosis via the B cell antigen receptor requires Bax translocation and involves mitochondrial depolarization, cytochrome C release, and caspase-9 activation

Various routes to apoptosis can be active during B cell development. In a model system of mature B cells, differences in caspase-3 processing have suggested that antigen receptor (BCR)-mediated apoptosis may involve a zVAD-insensitive initiator protease(s). In search of the events leading to caspase-3 activation, we now establish that both CD95- and BCR-mediated apoptosis depend on Bax activation and cytochrome C (cytC) release. Nevertheless, the timing and caspase-dependence of mitochondrial membrane depolarization differed considerably after CD95- or BCR-triggering. To delineate events subsequent to cytC release, we compared apoptosis induced via BCR triggering and via direct mitochondrial depolarization by CCCP. In both cases, partial processing of caspase-3 was observed in the presence of zVAD. By expression in 293 cells we addressed the potential of candidate initiator caspases to function in the presence of zVAD, and found that caspase-9 efficiently processed caspase-3, while caspase-2 or -8 were inactive. Finally, retroviral expression of dominant-negative caspase-9 inhibited both CD95- and BCR-mediated apoptosis. In conclusion, we obtained no evidence for involvement of a BCR-specific protease. Instead, our data show for the first time that the BCR-signal causes Bax translocation, followed by mitochondrial depolarization, and cytC release. Subsequent caspase-9 activation can solely account for events further downstream.     

Arsenic trioxide sensitizes CD95/Fas-induced apoptosis through ROS-mediated upregulation of CD95/Fas by NF-kappaB activation

CD95/Fas is a cell surface protein that belongs to the tumor necrosis factor receptor family. Signals through CD95/Fas are able to induce apoptosis in sensitive cells. Therefore, modalities to regulate the CD95/Fas expression level in tumor cells are called for. In the present study, we show that sublethal doses of arsenic trioxide (As2O3) sensitized CD95/Fas-induced apoptosis in human cervical cancer cells, and the sensitizing effects resulted from As2O3-mediated increase in the expression of the CD95/Fas. N-acetyl-L-cysteine, a specific scavenger of reactive oxygen species, abrogated As2O3-induced upregulation of CD95/Fas and enhancement of CD95/Fas-mediated apoptosis. Furthermore, inhibition of NF-kappaB by transient transfection of IkappaBalpha supersurppessor blocked the increase of CD95/Fas expression following As2O2 treatment. Antisense oligonucleotide of CD95/Fas and ZB4, an antibody that blocks the binding of CD95/Fas ligand to CD95/Fas, reduced the amount of As2O3-sensitized CD95/Fas-induced apoptosis, demonstrating the specificity of CD95/Fas-binding ligands in the As2O3-sensitized CD95/Fas-induced apoptosis. These findings demonstrate that sensitization of human cervical cancer cells to CD95/Fas-mediated apoptosis by As2O3 can be partly due to induction of ROS and subsequent upregulation of CD95/Fas gene expression by NF-kappaB activation.     

Molecular and cellular mechanisms of donor cell-induced tolerance

The induction of immunologic tolerance to solid organ allografts is a subject of intense investigation because of the morbidity and mortality associated with standard immunosuppressive therapy. One method that is currently in clinical and preclinical testing involves the transient ablation of recipient T cells using polyclonal antithymocyte sera or monoclonal anti-CD4/CD8 antibody treatment, followed by the posttransplant administration of donor bone marrow cells or of donor peripheral lymphoid populations. Recent studies in our laboratory have shown that the molecular and cellular basis of the prolongation of graft survival by donor cell administration depends on the cellular compartment from which the donor cells were derived. We provide here a brief review of these data followed by new data suggesting that the mode of peripheral and central selection is also dependent on the source from which the donor cells were derived.     

Disruption of the NMDA receptor-PSD-95 interaction in hippocampal neurons with no obvious physiological short-term effect

PSD-95 binds to and co-localizes with NMDA receptors at postsynaptic sites. Their co-expression in COS7 cells induces the formation of aggregates containing both proteins. These findings have lead to the hypothesis that PSD-95 helps to cluster NMDA receptors at postsynaptic sites. In addition, PSD-95 binds various regulatory proteins including Src, Pyk2, SynGAP, and nNOS and may recruit signaling proteins to NMDA receptors. We tested whether synaptic transmission or plasticity was affected by acute dissociation of the PSD-95-NMDA receptor interaction with various peptides that bound to the first two PDZ domains of PSD-95 and its homologs and with antibodies directed against the very C-terminus of the NR2A and NR2B subunits of the NMDA receptor. Membrane-impermeable peptides injected via whole cell patch electrodes distributed within minutes throughout dendritic branches into spines in acute hippocampal slices and membrane-permeable peptides containing 11 arginine residues effectively accumulated in neurites in slices and primary hippocampal cultures. Neither peptides nor antibodies showed any effect on basal synaptic transmission or induction of long-term potentiation (LTP) in hippocampal slices. Pharmacologically isolated NMDA receptor activity was also not affected. However, the membrane-permeable peptide disrupted the NMDA receptor-PSD-95 interaction in slices as tested by immunoprecipitation and subsequent immunoblotting. These findings suggest that acute dissociation of PSD-95 and its homologs from the NMDA receptor and likely from other protein complexes does not result in any easily detectable physiological effects in hippocampal slices. However, we cannot exclude a role of PSD-95 in early events that lead to clustering of NMDA receptors or of other proteins including stargazin and AMPA receptors at postsynaptic sites nor do these experiments address the possibility of long-term changes in the slices. In fact, incubation of primary hippocampal cultures with the membrane-permeable peptide lead to a moderate decrease in the number of dendritic clusters of PSD-95 and NMDA receptors and their colocalization by 20-30%, suggesting some role of PSD-95 and its homologs in NMDA receptor clustering.     

Effect of fatty acids on expression of endothelial leukocyte adhesion molecules

Summary.Background: With respect to linoleic acid both beneficial and proatherogenic effects have been described. However, the effect on expression of cell adhesion molecules on human coronary artery endothelial cells (HCAEC) is not yet established. The aim of the experiments was to evaluate the influence of linoleic acid in comparison with palmitic acid regarding the cytokine-induced expression of endothelial leukocyte adhesion molecules (intercellular cell adhesion molecule-1 ICAM-1, vascular cell adhesion molecule-1 VCAM-1, E-selectin).Methods: HCAEC were cultured in microvascular endothelial cell growth medium. In the experiments, the cells were preincubated with linoleic acid and palmitic acid, respectively (10 µmol/l, 2 days) or under control conditions, after which interleukin- 1 (IL-1, 10 ng/ml in the test medium) was added for 1 day. The monoclonal antibodies used were fluorescein isothiocyanate (FITC)- labeled anti-ICAM-1, FITC-labeled anti-VCAM-1, and FITC-labeled anti-E-selectin. Expression was analyzed by flow cytofluorimetry. Next, to examine the effects of fatty acids on adhesion of monocytes to endothelial cells, adhesion experiments with the monocytic U 937 cell line were performed.Results and conclusions: IL-1 increased ICAM-1,VCAM-1, and E-selectin expression compared to controls. Incubation with IL-1 together with linoleic acid reduced the expression of ICAM-1 and VCAM-1 in contrast to palmitic acid. Furthermore, in the presence of linoleic acid a tendency of diminished adhesion of monocytes is seen.The results indicate that a reduced expression of cell adhesion molecules may be relevant to the antiatherogenic effects of linoleic acid. This is in contrast to the properties of palmitic acid.