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K M Debatin

Publications and source records attributed to K M Debatin.

At least 19 recordsLinked to original sources
PubMed2006

NF-kappaB-independent sensitization of glioblastoma cells for TRAIL-induced apoptosis by proteasome inhibition.

The transcription factor nuclear factor-kappaB (NF-kappaB) is a key regulator of stress-induced transcriptional activation and has been implicated in mediating primary or acquired apoptosis resistance in various cancers. In the present study, we therefore investigated the role of NF-kappaB in regulating apoptosis in malignant glioma, a prototypic tumor refractory to current treatment approaches. Here, we report that constitutive NF-kappaB DNA-binding activity was low or moderate in eight different glioblastoma cell lines compared to Hodgkin's lymphoma cells, known to harbor aberrant constitutive NF-kappaB activity. Specific inhibition of NF-kappaB by overexpression of inhibitor of kappaB (IkappaB)alpha superrepressor did not enhance spontaneous apoptosis of glioblastoma cells. Also, overexpression of IkappaBalpha superrepressor had no significant impact on apoptosis induced by two prototypic classes of apoptotic stimuli, that is, chemotherapeutic drugs or death-inducing ligands such as TNF-related apoptosis inducing ligand (TRAIL), which are known to trigger NF-kappaB activation as part of a cellular stress response. Similarly, inhibition of NF-kappaB by the proteasome inhibitor MG132 did not increase doxorubicin (Doxo)-induced apoptosis of glioblastoma cells, although it prevented DNA binding of NF-kappaB complexes in response to Doxo. Interestingly, proteasome inhibition significantly sensitized glioblastoma cells for TRAIL-induced apoptosis. These findings indicate that the characteristic antiapoptotic function of NF-kappaB reported for many cancers is not a primary feature of glioblastoma and thus, specific NF-kappaB inhibition may not be effective for chemosensitization of glioblastoma. Instead, proteasome inhibitors, which enhanced TRAIL-induced apoptosis in an NF-kappaB-independent manner, may open new perspectives to increase the efficacy of TRAIL-based regimens in glioblastoma, which warrants further investigation.

Active Transport, Cell Nucleus↗
PubMed2005

AML bearing the translocation t(11;17)(q23;q21): involvement of MLL and a region close to RARA, with no differentiation response to retinoic acid.

We describe a case of acute myeloid leukemia (AML) bearing the translocation t(11;17)(q23;q21). The morphological phenotype represented a monoblastic leukemia, AML French-American-British (FAB) M5a. Further analysis of the translocation revealed an involvement of the mixed-lineage leukemia (MLL) gene and a region closely proximal to the retinoic acid (RA) receptor alpha (RARA) gene. AMLs involving both a rearranged MLL and the 17q21 region, in which the RARA gene is located, have only been described in some individual cases. The functional role of this translocation is still unknown. Rearrangements of the MLL (11q23) gene in AML are usually related to the morphological phenotype FAB M5. In general, they are associated with an adverse prognosis. In acute promyelocytic leukemia, the translocation (15;17)(q22;q11-21) involving the RARA leads to a maturation arrest that can be overcome by RA, often inducing remission. In other forms of AML, however, the effects of RA are limited and diverse. To study whether RA might have a therapeutical potential in our case, we performed an in vitro analysis of RA effects on AML cells. We found that RA leads to enhanced cell death and up-regulation of CD38 and CD117. However, no hints of RA-induced in vitro differentiation were visible. Our data indicate that in AML cells bearing the t(11;17)(q23;q21), a differentiation arrest that is overcome by RA is not present. On the contrary, RA induces alterations in cellular regulation that are similar to the RA-induced changes observed in early hematogenic progenitors; thus, a possible therapeutical benefit of RA in such cases remains open.

ADP-ribosyl Cyclase 1↗
PubMed2005

The effect of the HIV protease inhibitor ritonavir on proliferation, differentiation, lipogenesis, gene expression and apoptosis of human preadipocytes and adipocytes.

HIV patients in highly active antiretroviral therapy (HAART) develop lipodystrophy and insulin resistance. Protease inhibitors have been shown to alter adipocyte metabolism in murine cell lines. In this study, biological effects of the HIV protease inhibitor, ritonavir, were investigated on human SGBS preadipocytes and adipocytes. Ritonavir dose-dependently impaired preadipocyte proliferation and adipogenic differentiation. Gene expression analysis measured by real-time PCR, showed no effect of ritonavir (up to 20 microM) on expression of mRNA of PPARgamma2 and SREBP1c, but suppressed adiponectin mRNA while increasing IL-6 mRNA expression. In human adipocytes, ritonavir at therapeutic concentrations inhibited insulin-stimulated lipogenesis, reduced GLUT4 mRNA, fatty acid synthase and adiponectin expression, while increasing IL-6 mRNA expression. Finally, long-term treatment (72 and 120 h) of SGBS adipocytes but not preadipocytes with ritonavir induced apoptosis in up to 15% of the cells. All together, these data show effects of ritonavir on human preadipocytes and adipocytes aiming at reducing adipose tissue mass and increasing insulin resistance. These in vitro findings may partly explain the clinical findings in patients under HAART. Furthermore, SGBS cells may serve as a useful tool in further investigation of the mechanism of protease inhibitor action in human adipocytes.

Adipocytes↗
PubMed2004

Betulinic acid-induced apoptosis in leukemia cells.

Betulinic acid (BA), a natural component isolated from Birch trees, effectively induces apoptosis in neuroectodermal and epithelial tumor cells and exerts little toxicity in animal trials. Here, we show that BA-induced marked apoptosis in 65% of primary pediatric acute leukemia cells and all leukemia cell lines tested. When compared for in vitro efficiency with conventionally used cytotoxic drugs, BA was more potent than nine out of 10 standard therapeutics and especially efficient in tumor relapse. No crossresistances were found between BA and any cytotoxic drug. Intracellular apoptosis signaling in leukemia tumor cells paralleled the pathway found in neuroectodermal cells involving caspases, but not death receptors. In isolated mitochondria, BA induced release of both cytochrome c and Smac. Taken together, BA potently induces apoptosis in leukemia cells and should be further evaluated as a future drug to treat leukemia.

Adolescent↗
PubMed2001

Activation of apoptosis pathways in peripheral blood lymphocytes by in vivo chemotherapy.

In addition to myelosuppression, anticancer drugs cause rapid and persistent depletion of lymphocytes, possibly by direct apoptosis induction in mature T and B cells. Induction of apoptosis regulators was analyzed in peripheral blood lymphocytes from pediatric patients undergoing first-cycle chemotherapy for solid tumors. In vivo chemotherapy induced a significant increase in lymphocyte apoptosis ex vivo. The activation of initiator caspase-8 and effector caspase-3 and the cleavage of caspase substrates was detected 12 to 48 hours after the onset of therapy. Caspase inhibition by Z-VAD-fmk did not reduce ex vivo lymphocyte apoptosis in all patients, indicating the additional involvement of caspase-independent cell death. No evidence for the involvement of activation-induced cell death was found in the acute phase of lymphocyte depletion as analyzed by activation marker expression and sensitivity for CD95 signaling. Lymphocyte apoptosis in vivo appeared to be predominantly mediated by the mitochondrial pathway because a marked decrease of mitochondrial membrane potential (DeltaPsi(M)) was detected after 24 to 72 hours of treatment, preceded by the increased expression of Bax. Interestingly, despite the use of DNA-damaging agents, p53 remained completely undetectable throughout treatment. In contrast, in vitro treatment with cytarabine and etoposide induced p53 protein, CD95 receptor expression, CD95 sensitivity, and CD95 receptor-ligand interaction in stimulated cycling lymphocytes, but no such induction was seen in resting cells. These data suggest that chemotherapy-induced lymphocyte depletion involves distinct mechanisms of apoptosis induction, such as direct mitochondrial and caspase-dependent pathways in resting cells and p53-dependent pathways in cycling lymphocytes.

Adolescent↗
PubMed2001

Cellular stress response and apoptosis in cancer therapy.

Anticancer treatment using cytotoxic drugs is considered to mediate cell death by activating key elements of the apoptosis program and the cellular stress response. While proteolytic enzymes (caspases) serve as main effectors of apoptosis, the mechanisms involved in activation of the caspase system are less clear. Two distinct pathways upstream of the caspase cascade have been identified. Death receptors, eg, CD95 (APO-1/Fas), trigger caspase-8, and mitochondria release apoptogenic factors (cytochrome c, Apaf-1, AIF), leading to the activation of caspase-9. The stressed endoplasmic reticulum (ER) contributes to apoptosis by the unfolded protein response pathway, which induces ER chaperones, and by the ER overload response pathway, which produces cytokines via nuclear factor-kappaB. Multiple other stress-inducible molecules, such as p53, JNK, AP-1, NF-kappaB, PKC/MAPK/ERK, and members of the sphingomyelin pathway have a profound influence on apoptosis. Understanding the complex interaction between different cellular programs provides insights into sensitivity or resistance of tumor cells and identifies molecular targets for rational therapeutic intervention strategies.

Animals↗
PubMed2001

Sensitization for death receptor- or drug-induced apoptosis by re-expression of caspase-8 through demethylation or gene transfer.

Resistance of tumors to treatment with cytotoxic drugs, irradiation or immunotherapy may be due to disrupted apoptosis programs. Here, we report in a variety of different tumor cells including Ewing tumor, neuroblastoma, malignant brain tumors and melanoma that caspase-8 expression acts as a key determinant of sensitivity for apoptosis induced by death-inducing ligands or cytotoxic drugs. In tumor cell lines resistant to TRAIL, anti-CD95 or TNFalpha, caspase-8 protein and mRNA expression was decreased or absent without caspase-8 gene loss. Methylation-specific PCR revealed hypermethylation of caspase-8 regulatory sequences in cells with impaired caspase-8 expression. Treatment with the demethylation agent 5-Aza-2'-deoxycytidine (5-dAzaC) reversed hypermethylation of caspase-8 resulting in restoration of caspase-8 expression and recruitment and activation of caspase-8 at the CD95 DISC upon receptor cross-linking thereby sensitizing for death receptor-, and importantly, also for drug-induced apoptosis. Inhibition of caspase-8 activity also inhibited apoptosis sensitization by 5-dAzaC. Similar to demethylation, introduction of caspase-8 by gene transfer sensitized for apoptosis induction. Hypermethylation of caspase-8 was linked to reduced caspase-8 expression in different tumor cell lines in vitro and, most importantly, also in primary tumor samples. Thus, these findings indicate that re-expression of caspase-8, e.g. by demethylation or caspase-8 gene transfer, might be an effective strategy to restore sensitivity for chemotherapy- or death receptor-induced apoptosis in various tumors in vivo.

Apoptosis↗
PubMed2001

HIPK2 overexpression leads to stabilization of p53 protein and increased p53 transcriptional activity by decreasing Mdm2 protein levels.

BACKGROUND: HIPK2 (homeodomain-interacting protein kinase 2) has been identified as a nuclear serine/threonine kinase. A central function of HIPK2 is repressing transcription of homeodomain containing transcription factors. RESULTS AND CONCLUSIONS: We show here that HIPK2 activates transcription mediated by tumor suppressor p53 responsive promoter elements. Overexpression of HIPK2 leads to an increase of p53 protein expression or stability, which becomes enhanced further in the presence of the DNA damaging drug doxorubicin. The effects of HIPK2 on p53 are not observed with kinase deficient HIPK2 mutants. However, HIPK2 is not sufficient for phosphorylation of three crucial serine residues of p53, suggesting that HIPK2-induced p53 activation does not involve phosphorylation of p53. Instead, HIPK2 leads to a downregulation of p53-induced Mdm2 protein and this may lead to stabilization of p53. Overexpression of HIPK2 does not lead to a change of Mdm2 mRNA expression. The data suggest that HIPK2 plays a critical role in p53 mediated cellular responses by removing the p53 inhibitor protein Mdm2 via modification of the protein itself or its intracellular movement.

Journal Article↗
PubMed2001

Murine models for experimental therapy of pediatric solid tumors with poor prognosis.

Novel therapeutic strategies are required for pediatric solid tumors with poor prognosis such as metastasizing neuroblastoma, rhabdomyosarcoma and Ewing's sarcoma. A prerequisite for the development of such new therapies is the availability of murine models. To be useful for therapeutic studies, these models should not only recapitulate the genetic alterations characteristic of the human disease but should also mimic the metastatic process and the response to current therapy, both of which ultimately determine the fate of children with these tumors. This review scrutinizes the utility of existing murine models of neuroblastoma, rhabdomyosarcoma and Ewing's sarcoma for investigating novel therapies. Much experience has been gained with both syngeneic and xenogeneic transplantable models of these tumors, while transgenic and knockout mice are just beginning to be available for therapeutic investigations. Modeling the genetic aberrations characterizing these tumors may provide faithful models for therapeutic studies in the future.

Animals↗
PubMed2001

Cell type specific involvement of death receptor and mitochondrial pathways in drug-induced apoptosis.

Apoptosis in response to cellular stress such as treatment with cytotoxic drugs is mediated by effector caspases (caspase-3) which can be activated by different initiator pathways. Here, we report on a cell type specific triggering of death receptor and/or mitochondrial pathways upon drug treatment. In type I cells (BJAB), both the receptor and the mitochondrial pathway were activated upon drug treatment, since blockade of either the receptor pathway by overexpression of dominant negative FADD (FADD-DN) or of the mitochondrial pathway by overexpression of Bcl-X(L) only partially inhibited apoptosis. Drug treatment induced formation of a FADD- and caspase-8-containing CD95 death-inducing signaling complex (DISC) in type I cells resulting in activation of caspase-8 as the most apical caspase. In contrast, in type II cells (Jurkat), apoptosis was predominantly controlled by mitochondria, since overexpression of Bcl-2 completely blocked drug-induced apoptosis, while overexpression of FADD-DN had no protective effect. In these cells, caspases including caspase-8 were activated by mitochondria-driven signaling events and no DISC was detected despite expression levels of CD95, FADD and caspase-8 proteins comparable to type I cells. Likewise, drug-induced CD95 aggregation was predominantly found in type I cells. Bid was cleaved prior to mitochondrial alterations in type I cells providing a molecular link between caspase-8 activation and mitochondrial perturbations, whereas in type II cells, Bid was cleaved downstream of mitochondria. Our findings of a cell type specific response to cytotoxic drugs have implications for the identification of molecular parameters for chemosensitivity or resistance in different tumor cells.

Adaptor Proteins, Signal Transducing↗
PubMed2001

Suicide gene therapy for pediatric tumors.

Tumor gene therapy is potentially very specific and efficacious. Suicide genes are promising tools in the arsenal of tumor gene therapy. However, problems of tumor targeting, low in vivo efficacy of nucleic acid transfer, and recent reports of adverse effects hinder the translation of this approach into clinical practice. Therefore vector design, tumor targeting, mechanisms of cell kill and killing of untransfected tumor cells must be improved. Once these problems are solved in vitro and in animal models, gene therapy holds great promise for pediatric oncology given the abundance of specific targets in pediatric tumors. This review describes the current state of preclinical research in tumor suicide gene therapy, provides an outline of pediatric suicide gene therapy protocols, and identifies potential targets in pediatric malignancies.

Adolescent↗
PubMed2001

Congenital neuroblastoma mimicking early onset sepsis.

UNLABELLED: A newborn girl presented with symptoms of severe early onset sepsis but also with systemic hypertension (SH) at age 3 h. Plasma catecholamine (CAT) levels were extremely elevated, reflecting increased release of CAT from a congenital neuroblastoma (NB). Clinical symptoms at time of admission were: prolonged capillary refill (5 s), tachycardia, tachydyspnoea, metabolic acidosis (pH 7.17, lactate 11.8 mmol/l), fever (38.4 degrees C) and SH: 90/50/65 mmHg (systolic/diastolic/mean). The infant experienced organ failure (lung, heart, liver). A retroperitoneal dumbbell tumour was detected. Plasma CAT levels at age 15 h were: noradrenaline 219 nmol/l; adrenaline 13 nmol/l; and dopamine 65.3 nmol/l. SH responded to intermittent alpha-adrenergic blockage. CAT-related symptoms ceased within 1 week. The intraspinal NB was surgically removed when cord compression became symptomatic. The neurological and developmental state is normal at age 17 months. The abdominal NB regressed spontaneously. CONCLUSION: A neuroblastoma should be considered in newborn infants presenting with a shock-like condition together with systemic hypertension.

Blood Gas Analysis↗
PubMed2001

Successful HLA-identical bone marrow transplantation in a patient with PNP deficiency using busulfan and fludarabine for conditioning.

PNP deficiency is an autosomal recessive metabolic disorder characterized by severe combined immunodeficiency and by complex neurological symptomatology including ataxia, developmental delay and spasticity. Patients usually die in the first or second decade of life due to recurrent infections. The only curative treatment is bone marrow transplantation (BMT). We describe a 22-month-old girl who underwent BMT from her HLA-identical brother. Conditioning consisted of busulfan and fludarabine only, resulting in low toxicity and prompt engraftment. At 18 months after BMT, the girl has developed normal immunological functions, and her neurological status has improved.

Antineoplastic Combined Chemotherapy Protocols↗
PubMed2001

Eradication of a dysfunctional HLA-haploidentical T cell system by a second HLA-identical BMT.

A 12-year-old boy treated for SCID at 1 month of age by HLA-haploidentical BMT developed a lymphoproliferative disease of unknown etiology at the age of 9 years characterized by sustained, marked elevation of circulating CD8+ donor T cells and by diffuse infiltration of the liver by CD8+ T cells. Because of progressive liver disease, the patient underwent a second BMT from a younger HLA-matched sister. This treatment induced an effective graft-versus-graft reaction and led to complete replacement of the HLA-nonidentical, dysfunctional T cell system, resolution of the hepatopathy and full reconstitution of T and B cell functions.

Bone Marrow Transplantation↗
PubMed2001

Characterization of a human preadipocyte cell strain with high capacity for adipose differentiation.

OBJECTIVE: To develop and to characterize a human preadipocyte cell strain with high capacity for adipose differentiation serving as a model for studying human adipocyte development and metabolism in vitro. METHODS: Cells were derived from the stromal cells fraction of subcutaneous adipose tissue of an infant with Simpson-Golabi-Behmel syndrome (SGBS). Adipose differentiation was induced under serum-free culture conditions by exposure to 10 nM insulin, 200 pM triiodothyronine, 1 microM cortisol and 2 microM BRL 49653, a PPAR gamma agonist. RESULTS: During the differentiation process SGBS cells developed a gene expression pattern similar to that found in differentiating human preadipocytes with a characteristic increase in fat cell-specific mRNAs encoding lipoprotein lipase (LPL), glycero-3-phosphate dehydrogenase (GPDH), GLUT4, leptin and others. Differentiated SGBS cells exhibited an increase in glucose uptake upon insulin stimulation and in glycerol release upon catecholamine exposure. SGBS adipocytes were morphologically, biochemically and functionally identical to in vitro differentiated adipocytes from healthy subjects. However, while preadipocytes from healthy control infants rapidly lost their capacity to differentiate after a few cell divisions in culture, SGBS cells maintained their differentiation capacity over many generations: upon appropriate stimulation 95% of SGBS cells of generation 30 developed into adipocytes. A mutation in the glypican 3 gene was not detected in the patient. Thus, it remains unclear whether the molecular alteration in SGBS cells is also responsible for the high differentiation capacity and further investigations are required. CONCLUSION: The human cell strain described here provides an almost unlimited source of human preadipocytes with high capacity for adipose differentiation and may, therefore, represent a unique tool for studying human fat cell development and metabolism. International Journal of Obesity (2001) 25, 8-15

Adipocytes↗