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Bjørn Tore Gjertsen

Publications and source records attributed to Bjørn Tore Gjertsen.

At least 19 recordsLinked to original sources
PubMed2006

T cells remaining after intensive chemotherapy for acute myelogenous leukemia show a broad cytokine release profile including high levels of interferon-gamma that can be further increased by a novel protein kinase C agonist PEP005.

Cytokines are released during T cell activation, including the potentially anti-leukemic interferon-gamma (IFNgamma), but also the hematopoietic growth factor granulocyte-macrophage colony-stimulating factor (GM-CSF) that enhance proliferation and inhibit apoptosis of acute myelogenous leukemia (AML) cells. In the present study we investigated the release of IFNgamma and GM-CSF by circulating T cells in AML patients with chemotherapy-induced cytopenia. T cells were activated with anti-CD3 plus anti-CD28 in a whole-blood assay in the presence of their natural cytokine network. We examined 63 samples derived from 16 AML patients during 28 chemotherapy cycles. Activated T cells showed a broad cytokine release profile, but IFNgamma and GM-CSF levels showed a significant correlation and were generally higher than the other cytokine levels. Higher IFNgamma and GM-CSF responses were associated with a low CD4:CD8 ratio, older patient age and no ongoing chemotherapy indicating potential utility of T cell activation regimes for the older AML patient. The cytokine levels could be further increased by the novel protein kinase C agonist PEP005, which also induced significant production of IL2 and TNFalpha which could contribute to anti-tumor effects in AML patients. We conclude that remaining T cells after intensive AML therapy show a broad cytokine release profile including high and significantly correlated levels of potentially anti-leukemic IFNgamma and the AML growth factor GM-CSF. The final outcome of an AML-initiated T cell cytokine response will thus depend on the functional characteristics of the AML cells, in particular the relative expression of IFNgamma and GM-CSF receptors which differs between AML patients.

Adult↗
PubMed2006

Effects of interferon gamma on native human acute myelogenous leukaemia cells.

T cell targeting immunotherapy is now considered a possible strategy in acute myelogenous leukaemia (AML), and IFNgamma release may then contribute to the antileukaemic effects. We investigated the effects of IFNgamma on native human AML cells. Normal T cells could be activated to release IFNgamma in the presence of AML cells. Furthermore, high levels of CD119 (IFNgamma receptor alpha chain) expression were observed for all 39 patients examined. Receptor expression was decreased after exposure to exogenous IFNgamma, and receptor ligation caused Stat1 phosphorylation but no phosphorylation of the alternative messengers Erk1/2. The effect of exogenous IFNgamma on AML blast proliferation was dependent on the local cytokine network and IFNgamma (1) inhibited proliferation in the presence of exogenous IL1beta, GM-CSF, G-CSF and SCF; (2) had divergent effects in the presence of IL3 and Flt3 (65 patients examined); (3) inhibited proliferation in the presence of endothelial cells but had divergent effects in the presence of fibroblasts, osteoblasts and normal stromal cells (65 patients examined). IFNgamma increased stress-induced (spontaneous) in vitro apoptosis as well as cytarabine-induced apoptosis only for a subset of patients. Furthermore, IFNgamma decreased the release of proangiogenic CXCL8 and increased the release of antiangiogenic CXCL9-11. We conclude that IFNgamma can be released in the presence of native human AML cells and affect AML cell proliferation, regulation of apoptosis and the balance between pro- and antiangiogenic chemokine release.

Adult↗
PubMed2006

Correlation analysis of two-dimensional gel electrophoretic protein patterns and biological variables.

BACKGROUND: Two-dimensional gel electrophoresis (2DE) is a powerful technique to examine post-translational modifications of complexly modulated proteins. Currently, spot detection is a necessary step to assess relations between spots and biological variables. This often proves time consuming and difficult when working with non-perfect gels. We developed an analysis technique to measure correlation between 2DE images and biological variables on a pixel by pixel basis. After image alignment and normalization, the biological parameters and pixel values are replaced by their specific rank. These rank adjusted images and parameters are then put into a standard linear Pearson correlation and further tested for significance and variance. RESULTS: We validated this technique on a set of simulated 2DE images, which revealed also correct working under the presence of normalization factors. This was followed by an analysis of p53 2DE immunoblots from cancer cells, known to have unique signaling networks. Since p53 is altered through these signaling networks, we expected to find correlations between the cancer type (acute lymphoblastic leukemia and acute myeloid leukemia) and the p53 profiles. A second correlation analysis revealed a more complex relation between the differentiation stage in acute myeloid leukemia and p53 protein isoforms. CONCLUSION: The presented analysis method measures relations between 2DE images and external variables without requiring spot detection, thereby enabling the exploration of biosignatures of complex signaling networks in biological systems.

Algorithms↗
PubMed2006

Stress-induced in vitro apoptosis of native human acute myelogenous leukemia (AML) cells shows a wide variation between patients and is associated with low BCL-2:Bax ratio and low levels of heat shock protein 70 and 90.

Spontaneous in vitro apoptosis reflects a true biological heterogeneity between patients which has to be considered when in vitro models are used to study regulation of apoptosis in native human AML cells. Even though the balance between pro- and anti-apoptotic signaling seems to have a prognostic impact in AML, the possible clinical relevance of spontaneous apoptosis remains to be clarified. High apoptosis/low viability was associated with low levels of heat shock proteins 70 and 90 as well as low Bcl-2:Bax ratio for patients heterogeneous with regard to morphology, membrane molecule expression, genetic abnormalities and response to therapy.

Adult↗
PubMed2006

Adaptive contrast enhancement of two-dimensional electrophoretic protein gel images facilitates visualization, orientation and alignment.

2-DE is a powerful technique to discriminate post-translationally modified protein isoforms. However, all steps of 2-DE preparation and gel-staining may introduce unwanted artefacts, including inconsistent variation of background intensity over the entire 2-DE gel image. Background intensity variations limit the accuracy of gel orientation, overlay alignment and spot detection methods. We present a compact and efficient denoising algorithm that adaptively enhances the image contrast and then, through thresholding and median filtering, removes the gray-scale range covering the background. Applicability of the algorithm is demonstrated on immunoblots, isotope-labeled gels, and protein-stained gels. Validation is performed in contexts of (i) automatic gel orientation based on Hough transformation, (ii) overlay alignment based on cross correlation and (iii) spot detection. In gel stains with low background variability, e.g. Sypro Ruby, denoising will lower the spot detection sensitivity. In gel regions with high background levels denoising enhances spot detection. We propose that the denoising algorithm prepares images with high background for further automatic analysis, without requiring manual input on a gel-to-gel basis.

Algorithms↗
PubMed2006

Protein lysine acetylation in normal and leukaemic haematopoiesis: HDACs as possible therapeutic targets in adult AML.

Several new therapeutic strategies are now considered for acute myelogenous leukaemia (AML), including modulation of protein lysine acetylation through inhibition of histone deacetylases (HDACs): a large group of enzymes that alters the acetylation and, thereby, the function of a wide range of nuclear and cytoplasmic proteins. Firstly, HDACs can deacetylate histones as well as transcription factors, and can modulate gene expression through both these mechanisms. Secondly, acetylation is an important post-translational modulation of several proteins involved in the regulation of cell proliferation, differentiation and apoptosis (e.g., p53, tubulin, heat-shock protein 90). The only HDAC inhibitors that have been investigated in clinical studies of AML are butyrate derivatives, valproic acid and depsipeptide. In the first studies, the drugs have usually been used as continuous therapy for several weeks or months, and in most studies the drugs were used alone or in combination with all-trans retinoic acid for treatment of patients with relapsed or primary resistant AML. Neurological toxicity and gastrointestinal side effects seem to be common for all three drugs. Complete haematological remission lasting for several months has been reported for a few patients (< 5% of included patients), whereas increased peripheral blood platelet counts seem more common and have been described both for patients with AML and myelodysplastic syndromes. Taken together, these studies suggest that HDAC inhibition can mediate antileukaemic effects in AML, but for most patients the clinical benefit seems limited and further studies of combination therapy are required.

Acetylation↗
PubMed2006

Proteomics approaches to elucidate oncogenic tyrosine kinase signaling in myeloid malignancies.

Myeloid malignancies frequently harbor specific mutations in protein tyrosine kinases leading to oncogenic cell signaling. The most extensively investigated example is chronic myeloid leukemia, where the pathogenic tyrosine kinase fusion protein Bcr-Abl is a successful target for disease control by the specific inhibitor imatinib mesylate. In acute myeloid leukemia the receptor tyrosine kinase Flt3 is frequently mutated and inhibitors to impair the oncogenic signaling are in development. In this review we exemplify oncogenic signaling and how signal pathways can be unraveled with help from proteomics-based technologies. The distinction between cell extract and single cell approaches aiming at rigorous standardization and reliable quantitative aspects for future proteomics-based diagnostics is discussed.

Benzamides↗
PubMed2006

Proteomics of p53 in diagnostics and therapy of acute myeloid leukemia.

The anti-oncogene TP53 is frequently mutated in human cancer, but in hematological malignancies this is a rare feature. In acute myeloid leukemia (AML) more than 90% of the patients comprise wild type TP53 in their cancer cells, but if TP53 is mutated or deleted the disease is often found to be chemoresistant. In this review we define proteomics of the oncogene product p53 as the study of proteins in the p53 regulating signaling networks, as well as the protein study of members of the p53 family itself. Various messenger RNA splice forms as well as a multitude of post-translational modifications give a high number of protein isoforms in the p53 family. Some of the proteomic techniques allow detection of various isoforms, such as two-dimensional gel electrophoresis in combination with tandem mass spectrometry (MS/MS) and this methodology may therefore increasingly be used as a diagnostic tool in human disease. We introduce the p53 protein as an illustration of the complexity of post-translational modifications that may affect one highly connected protein and discuss the possible impact in AML diagnostics if the p53 profile is reflecting cell stress and status of signal transduction systems of the malignancy.

Acetylation↗
PubMed2006

Proteomic strategies for individualizing therapy of acute myeloid leukemia (AML).

Acute myeloid leukemia (AML) is an aggressive hematological malignancy characterized by accumulating myeloid precursor cells in the bone marrow, with approximately 2-3 months 50% survival if left untreated. With current treatment modalities the five years overall survival hardly exceeds 50%. Cytogenetics and molecular diagnostics guide the clinician to select individualized therapy in certain subsets of AML, achieving long-term survival above 70% of these cases. However, approximately half of the AML patients have no risk stratifying features, and early reports indicate that proteomic approaches may be utilized for disease classification as well as development of novel biomarkers related to prognosis, diagnosis, and choice of therapeutic regimen. Proteomics, here defined as the analysis of all proteins in a cell, in a cell compartment or in a signaling pathway, has probably its greatest potential in investigating pathways that are easily targeted by small molecules or therapeutic antibodies. The major methodological challenges include detection sensitivity in a limited clinical material, a problem that in some cases can be solved through designated multiplexed protein assays based on single cells or cell extracts. In this review we will discuss pharmacoproteomic studies of drugs regulating leukemia specific targets like all-trans retinoic acid, histone deacetylase inhibitors, proteasome inhibitors and tyrosine kinase inhibitors, as well as studies on drug resistance and graft-versus-host studies during stem cell transplantations. These studies indicate new avenues in AML diagnostics, individualized therapy design and therapy response surveillance for the clinician.

Acute Disease↗
PubMed2006

cDNA microarray analysis of non-selected cases of acute myeloid leukemia demonstrates distinct clustering independent of cytogenetic aberrations and consistent with morphological signs of differentiation.

Acute myeloid leukemia (AML) is a heterogeneous disease with respect to biology and clinical course. Until now the basis for prognostic evaluation and therapeutic decision has been the karyotype, genetic FLT3 abnormalities and the initial chemotherapy response. A question that has emerged is if extensive gene expression analysis may supplement or partly replace current diagnostics. In an attempt to address this question, we performed cDNA microarray analysis on peripheral blood samples of 25 patients with newly diagnosed AML with high blast counts. The patients were randomly selected from a large group of consecutive patients. Leave-one-out crossvalidation (LOOCV) showed with high accuracy that gene expression classifiers could predict if leukaemia samples belonged to the FAB AML-M1 or to the FAB AML-M2 groups. An unsupervised two-dimensional hierarchical cluster analysis generated 3 patient subgroups. Except for an accumulation of samples classified as FAB M1 and M2 in cluster 3, there was no evident relationship between the clusters and the FAB classification. Each subgroup displayed clearly distinguished gene expression patterns validated using real-time quantitative PCR analysis. The identification of specific gene expressions that together constitute regulatory modules must complement cluster analyses in order to achieve an accurate basis for prognosis and prediction.

Adult↗
PubMed2005

Is targeted chemotherapy an alternative to immunotherapy in chronic lymphocytic leukemia?

Although molecular remission is now detected, it is still unknown whether we have the tools to cure B cell chronic lymphocytic leukemia (referred to as CLL). Nonetheless, several new therapeutic approaches have been introduced in cancer therapy during the last decade, including antiangiogenic therapy, apoptosis-inducing treatment and inhibition of heat shock proteins, farnesyl transferase, tyrosine kinases and proteasomes. These modalities may also be considered in CLL, but additional experimental characterization is required. Further characterization and development of CLL animal models should be a part of this preclinical work (especially xenografting in NOD/SCID animals, but also murine leukemia) to allow a more extensive evaluation prior to clinical trials. Animal models are particularly important for preclinical comparison of pharmacological effects between different disease compartments and for in vivo evaluation of antileukemic immune reactivity. However, T cell targeting therapy seems to have several advantages in comparison to other approaches: (1) based on the current clinical experience one would expect low toxicity for several of these strategies, especially vaccine treatment; (2) several studies have demonstrated that autologous T cells can recognize CLL cells; (3) experimental and clinical evidence suggests that immunotherapy can be combined with chemotherapy. Thus, T cell therapy has a relatively strong scientific basis that justifies further clinical studies of immunotherapy in CLL. Although several of the new pharmacological agents seem to have immunosuppressive effects, at least some of them (e.g. heat shock protein 90 inhibitors, proteasome inhibitors, inhibition of angiogenesis) appear to affect T cells only at relatively high concentrations and may thus be used in combination with immunotherapy.

Antineoplastic Combined Chemotherapy Protocols↗
PubMed2005

CD34 expression in native human acute myelogenous leukemia blasts: differences in CD34 membrane molecule expression are associated with different gene expression profiles.

BACKGROUND: The stem cell marker CD34 is expressed by leukemia blasts only for a subset of patients with acute myelogenous leukemia (AML). It is still controversial as to whether CD34 expression (defined as at least 10-20% positive cells) has any prognostic effect in patients with AML who receive intensive chemotherapy. The present study investigated whether gene expression profiling could be used to further subclassify CD34(+) AML cell populations. METHODS: AML blasts derived from 25 patients were examined; these patients were randomly selected from a larger consecutive group of patients. CD34 protein expression was determined by flow cytometry and expressed as the percentage of positive cells. Gene expression profiles were determined by complementary DNA microarrays. RESULTS: By unsupervised hierarchical clustering our patients could be grouped into two or three major subsets depending on the methodologic approach before clustering analysis (filtering or flooring of data, respectively). However, both approaches identified a cluster characterized by high gene expression and membrane molecule level of CD34. When using the floored expression profiles, the patient cluster characterized by increased CD34 gene expression was also characterized by a high percentage of CD34(+) cells (median 82%, range 56-100%) compared with the two other major clusters (median 19%, range <1-55%), but three of four outpatients also showed a high percentage of CD34(+) cells. CONCLUSION: A major proportion of patients with AML and high CD34 expression (usually >80% CD34(+) cells; nearly all patients had >50% positive cells) showed similarities in gene expression profile. In contrast, patients with lower CD34 expression often had a profile similar to those of patients regarded as CD34(-) according to conventional criteria. Our results suggest that the possible prognostic effect of CD34 expression should be reevaluated in clinical studies using additional or alternative cutoff values to describe CD34 expression.

Adult↗
PubMed2005

In vitro crosstalk between fibroblasts and native human acute myelogenous leukemia (AML) blasts via local cytokine networks results in increased proliferation and decreased apoptosis of AML cells as well as increased levels of proangiogenic Interleukin 8.

Interactions between native human acute myelogenous leukemia (AML) blasts and nonleukemic cells in the bone marrow microenvironment seem important both for disease development chemosensitivity. Native human AML blasts from consecutive patients were cultured with normal human bone marrow stromal cells and two fibroblast lines (HFL1 and Hs27) separated by a semipermeable membrane. This bidirectional crosstalk via the cytokine network between AML blasts and fibroblasts caused (i) increased proliferation, (ii) mediated antiapoptotic signalling and (iii) increased local levels of proangiogenic IL8.

Adult↗
PubMed2005

Proteomics in acute myelogenous leukaemia (AML): methodological strategies and identification of protein targets for novel antileukaemic therapy.

Enduring efforts into determination of the molecular biological status of acute myelogenous leukaemia (AML), a stem cell disease characterised by distinct blastic differentiation blocks and their extensive growth, continue to provide us with prognostically important information for more than half of all patients. In subsets of AML, molecular diagnostics rigorously guide the clinician toward the choice of optimal therapy. The in-depth characterization of leukemogenesis associated genetic alterations, such as the combined presence of activating mutations of tyrosine kinases together with altered transcription factors, and the documented impact of these mutations upon prognosis of AML, suggests AML as a primary candidate for pioneering proof-of-principle studies with new high throughput protein analysis techniques. This review aims to introduce the reader to proteomic methodology, e.g. two-dimensional polyacrylamide gel electrophoresis, mass spectrometry, SELDI and protein arrays. Examples of its use, including single cell phosphoprotein profiling in risk stratification, the probing of cellular effects of conventional chemotherapeutics and novel target determination are presented. Based on original proteomic analysis of AML, molecular characteristics of AML, in addition to knowledge of conventional therapeutics and novel drugs, we attempt to forecast the influence of proteomics in therapy development for AML.

Acetylation↗
PubMed2004

How should clinical data be included in experimental studies of cancer immunology?

Patients diagnosed with the same malignant disease are often heterogeneous with regard to age, complications, malignant cell morphology and tumor histology, disease stage, prognostic parameters, and previous therapy. Many of these factors can affect immunocompetent cells or influence the malignant cell susceptibility to immunotherapy. Summaries of relevant clinical information should therefore be included in cancer immunology studies to increase the present as well as the future scientific impact. Guidelines for selection of relevant information are suggested in the article.

Antigens, Neoplasm↗
PubMed2004

Osteoblasts increase proliferation and release of pro-angiogenic interleukin 8 by native human acute myelogenous leukemia blasts.

BACKGROUND AND OBJECTIVES: Interactions between acute myelogenous leukemia (AML) blasts and non-leukemic cells in the bone marrow seem to be important for both disease development and susceptibility to chemotherapy. Recent studies have focused on the endothelial cells, but other non-leukemic cells may also be involved. In the present study we investigated how osteoblasts affect native human AML blasts. DESIGN AND METHODS: AML cells were derived from a large group of consecutive patients. The AML blasts and osteoblastic sarcoma cell lines (Cal72, SJSA-1) were incubated together in different chambers separated by a semipermeable membrane. We investigated effects of co-culture on proliferation, apoptosis and cytokine release. RESULTS: The cross-talk between these two cell populations, achieved via release of soluble mediators, resulted in increased AML blast proliferation, including increased proliferation of clonogenic progenitors, but did not affect spontaneous in vitro apoptosis. Both interleukin (IL) 1-b and granulocyte-macrophage colony-stimulating factor were involved in this growth-enhancing cross-talk, and normal osteoblasts could also increase the AML blast proliferation. Furthermore, co-culture of AML blasts with osteoblastic sarcoma cells as well as normal osteoblasts increased the levels of the pro-angiogenic mediator IL8. INTERPRETATION AND CONCLUSIONS: Our in vitro results suggest that the release of soluble mediators by osteoblasts supports leukemic hematopoiesis through two major mechanisms: (i) direct enhancement of AML blast proliferation; and (ii) enhanced angiogenesis caused by increased IL8 levels.

Apoptosis↗