PubMed Health⌕ Search

Biomedical subjects

A C Bloem

Publications and source records attributed to A C Bloem.

At least 19 recordsLinked to original sources
PubMed1999

Idarubicin overcomes P-glycoprotein-related multidrug resistance: comparison with doxorubicin and daunorubicin in human multiple myeloma cell lines.

The clinical utility of anthracyclines like doxorubicin (DOX) and daunorubicin (DNR) for treatment of multiple myeloma (MM) is limited by the occurrence of multidrug resistance (MDR). Highly lipophilic anthracyclines like idarubicin (IDA) might circumvent MDR and thereby enhance chemotherapeutic efficacy. To determine the efficacy of IDA in myeloma cells, the pharmacokinetics and cytotoxicity of IDA and its major metabolite idarubicinol (IDAol) were compared with those of DNR, DOX, and doxorubicinol (DOXol) in the cell line RPMI 8226-S and two MDR sublines (8226-R7 and 8226-Dox40) that overexpress the drug transporter P-glycoprotein (Pgp). Cytotoxicity assays using MTT (viability) or annexin V (apoptosis) showed a 10-50-fold higher potency of IDA compared with DNR or DOX in the MDR variant cell lines. The difference in cytotoxicity was lower in the sensitive parental cell line (3-fold). These results are explained by a better intracellular uptake of IDA compared to DNR in resistant 8226 cell lines. The Pgp-inhibitor verapamil affected IDA uptake only in the most resistant cell line 8226-Dox40. This indicates that IDA is less sensitive than DNR to transport-mediated MDR. IDAol was at least 32-fold more cytotoxic than DOXol, and more susceptible to Pgp transport than IDA. These studies demonstrate that the efficacy of IDA in MDR MM cell lines is superior to that of DOX or DNR, and that IDA may become an important drug in the treatment of MM, especially in refractory disease.

ATP Binding Cassette Transporter, Subfamily B, Mem↗
PubMed1999

Donor leukocyte infusions inducing remissions repeatedly in a patient with recurrent multiple myeloma after allogeneic bone marrow transplantation.

We describe a patient with recurrent relapses after allogeneic BMT for multiple myeloma who repeatedly went into CR after donor leukocyte infusions (DLI). The first bone marrow relapse, 24 months after allogeneic BMT, was treated successfully with the infusion of 1.2 x 10(8) donor T cells. The second extramedullary relapse, 18 months later with a pleural mass and midthoracic spine process, responded again to DLI, however, only after three courses were given, each with escalating doses of T cells. The pleural mass was treated successfully with radiation therapy after the second DLI but reappeared 3 months later and responded again to the final DLI course with 5 x 10(8) T cells/kg. Nevertheless, graft-versus-host disease (GVHD) did not occur. Retrospective analysis of minimal residual disease in bone marrow aspirates during CR periods using a sensitive quantitative tumor-specific PCR showed that BM tumor cell infiltration persisted. The possible clinical implications of this case report, like maintenance DLI and the aim for molecular remissions, are discussed.

Bone Marrow Transplantation↗
PubMed1998

Lung-resistance-related protein expression is a negative predictive factor for response to conventional low but not to intensified dose alkylating chemotherapy in multiple myeloma.

This study was undertaken to assess the significance of lung-resistance related protein (LRP) expression in plasma cells from untreated multiple myeloma (MM) patients and to determine whether LRP was associated with a poor response and survival in patients treated with different dose regimens of melphalan. Seventy untreated patients received conventional oral dose melphalan (0.25 mg/kg, day 1 to 4) combined with prednisone (MP) or intravenous intermediate-IDM; 70 mg/m2) or high- (140 mg/m2) dose Melphalan (HDM). LRP expression was assessed with immunocytochemistry using the LRP-56 monoclonal antibody. LRP expression was found in 47% of patients. In the MP treated patients, LRP expression was a significant prognostic factor regarding response induction (P < .05), event free survival (P < .003), and overall survival (P < .001). In the intensified dose melphalan treated patients LRP did not have a prognostic value. The response rates of LRP-positive patients to MP and IDM/HDM were 18% versus 81%, respectively (P < .0001). We conclude that LRP is frequently expressed in untreated MM patients and is an independent predictor for response and survival in patients treated with MP. Pretreatment assessment of LRP identifies a subpopulation of patients with a poor probability of response to conventional dose melphalan. Dose intensification of melphalan is likely to overcome LRP-mediated resistance.

Adult↗
PubMed1998

CD44 isoforms distinguish between bone marrow plasma cells from normal individuals and patients with multiple myeloma at different stages of disease.

CD44 variant isoforms (CD44v) have been shown to be important factors in adverse prognosis in hematological malignancies. To investigate whether CD44 expression is associated with malignant transformation in multiple myeloma, RNA and protein expression of CD44 standard (CD44s) and CD44v4, v6, v9, v10 containing isoforms was compared on bone marrow plasma cells from normal individuals and myeloma patients at different stages of disease. CD44s protein expression is strongly decreased on myeloma plasma cells and non-malignant B cells in affected bone marrow of myeloma patients, while no differences in CD44s expression were found between blood B cells from normal individuals and myeloma patients. CD44v isoforms were expressed on plasma cells in the majority of normal and myeloma samples analyzed. CD44v9 and v10 containing isoforms were differentially expressed on bone marrow plasma cells from normal individuals (predominantly CD44v9+v10+) and myeloma patients with stable (predominantly CD44v9-v10+) or progressive (predominantly CD44v9+v10- disease. Normal and myeloma plasma cells contained CD44 mRNA transcripts consisting of multiple CD44v exons. In addition, CD44v9 positive myeloma cells carried large CD44 transcripts. These results imply that detection of CD44v isoforms may be a valuable diagnostic tool for monitoring myeloma disease progression and response to treatment.

Bone Marrow Cells↗
PubMed1998

Long-term bone marrow cultured stromal cells regulate myeloma tumour growth in vitro: studies with primary tumour cells and LTBMC-dependent cell lines.

Long-term bone marrow cultured stromal cells (LTBMC) produce IL-6 after contact with tumour cells from multiple myeloma patients. We found that LTBMC could substitute for exogenous IL-6 in the stimulation of bone marrow plasma cells from myeloma patients with active disease in short-term cultures. In addition, tumour cells of some patients with inactive disease, which were unresponsive to exogenous IL-6, were induced to IL-6-dependent growth after LTBMC co-culture. To study the role of LTBMC in myeloma tumour growth in vitro, plasma cell lines UM-2 and UM-3 were selected. UM-2 and UM-3 grew in contact with LTBMC and proliferation was blocked by antibodies against IL-6, IL-6 receptor (IL-6R, gp80, CD126) or the common signal transducing unit, gp130 (CD130). Culture with IL-6 alone or combined with GM-CSF resulted in cell death via apoptosis. The combination of IL-6 with soluble gp80, however, maintained in vitro proliferation of UM-2 and UM-3 cells. These data imply that LTBMC regulate myeloma growth in vitro via production of IL-6, possibly via induction of a functional IL-6 receptor on the tumour cells.

Base Sequence↗
PubMed1998

Activation and cell cycle antigens in CD4+ and CD8+ T cells correlate with plasma human immunodeficiency virus (HIV-1) RNA level in HIV-1 infection.

The relationship between T cell activation and human immunodeficiency virus type 1 (HIV-1) replication was studied in HIV-infected subjects, 20 with and 10 without anti-HIV treatment. Expression of Ki-67 proliferation-associated antigen was increased in CD4+ and CD8+ T cells and correlated with HLA-DR. In subjects without anti-HIV treatment, the plasma HIV-1 RNA level correlated with HLA-DR in CD4+ T cells, with Ki-67 in CD8+ T cells, and with expression of CD38 in both T cell subsets. A proportion of treated subjects had increased T cell activation despite 4 months of highly active antiretroviral treatment (HAART). In subjects receiving HAART, a high percentage of HLA-DR+ CD4+ T cells was associated with signs of opportunistic infections. This work supports the concept that, in the natural course of HIV-1 infection, HIV replication itself leads to general T cell activation and that opportunistic infections generate additional CD4+ T cell activation and HIV replication.

ADP-ribosyl Cyclase↗
PubMed1997

Anti-adhesive signals are mediated via major histocompatibility complex class II molecules in normal and neoplastic human B cells: correlation with B cell differentiation stage.

We show that major histocompatibility complex (MHC) class II molecules on B cells transit signals which regulate adhesion in a negative manner. Engagement of MHC class II molecules with antibodies results in detachment of B cells previously bound to interferon-gamma-activated human umbilical cord venous endothelial cells. This process depends on metabolic energy, active signaling and protein tyrosine kinase activity. The adhesion pathway influenced by this signaling event is neuraminidase sensitive. The anti-adhesive signaling program is activated in B cell lines with a mature phenotype, e.g. normal B cells from spleen and tonsil. In contrast, cell lines with a pre-B cell phenotype and normal B cells from peripheral blood are refractory to MHC class II-mediated regulation of adhesion. These results extend to neoplastic cells from patients with lymphoproliferative diseases representing different stages of B cell maturation. These results suggest that MHC class II-mediated signals regulate B cell adhesion in a developmentally programmed fashion; this might have implications for clinical behavior of B cell malignancies.

Animals↗
PubMed1996

Different CD44 splicing patterns define prognostic subgroups in multiple myeloma.

CD44 variant isoforms (CD44v) are generated by alternative splicing of the nuclear RNA resulting in the expression of additional protein domains in the extracellular region of the CD44 standard molecule (CD44s). In multiple myeloma (MM), CD44 mediates binding of tumor cells to stroma and regulates interleukin-6 production. To evaluate the role of CD44v isoforms in MM, CD44v expression was analyzed by immunohistochemical staining of 64 bone marrow biopsies from 38 MM patients. Expression of variant isoforms containing the 9v domain was observed in 36% of cases and was associated with an advanced stage (P < .02; n = 61), a progressive disease (P < .001; n = 61), and a shorter overall survival (P < .02; n = 36). In contrast, 3v, 4v, 6v, or 10v isoforms were detected only in a small percentage of the patients. To analyze the exon composition in RNA-transcripts, reverse transcriptase polymerase chain reaction analyses followed by Southern hybridization with exon-specific probes were performed in fluorescence-activated cell sorted myeloma plasma cells. Tumors expressing the 9v domain showed complex, 9v-containing transcripts in combinations with the 3v, 7v, 8v, and 10v exons. Identical transcripts were detected in several myeloma cell lines and in a Ki-1 B-immunoblastic lymphoma. Similar to high-grade non-Hodgkin's lymphoma and gastric and renal cell carcinoma, overexpression of 9v-containing isoforms in MM is related to an unfavorable clinical presentation and represents a new prognostic parameter.

Adult↗
PubMed1995

Adhesion molecules: a new target for immunoliposome-mediated drug delivery.

The anti-ICAM-1 monoclonal antibody F10.2 was conjugated to liposomes to target to cells expressing the cell adhesion molecule ICAM-1. We demonstrate that F10.2 immunoliposomes bind to human bronchial epithelial cells (BEAS-2B) and human umbilical vein endothelial cells (HUVEC) in a specific, dose- and time-dependent manner. It appears that the degree of ICAM-1 expression is the limiting factor in the degree of immunoliposome binding to the cells. These results are a first step in the strategy for specific drug delivery to target sites characterised by increased expression of adhesion molecules.

Antibodies, Monoclonal↗
PubMed1995

Co-ligation of ICAM-1 (CD54) and membrane IgM negatively affects B cell receptor signaling.

A possible role of intercellular adhesion molecule 1 (ICAM-1, CD54) in transmembrane signaling was investigated in B cells from the Burkitt lymphoma cell line MTLM4. Cross-linking of membrane IgM (mIgM) induced an increase in intracellular free Ca2+ as a result of the release from intracellular stores and an influx of extracellular Ca2+. When the B cells were incubated with limiting concentrations of anti-IgM, co-ligation of mIgM and CD54, but not CD19, resulted in an inhibition of the Ca2+ response. Separate cross-linking of mIgM and CD54 under these conditions, using isotype mismatched monoclonal antibodies (mAb), did not affect the mobilization of Ca2+. The CD54-mediated inhibition of the Ca2+ response was also observed in the absence of extracellular Ca2+. All CD54 mAb tested (F10.2, F10.3 and F7.11) interfered with mIgM signaling. The results presented in this report imply that CD54 is linked to intracellular signaling pathways and, via co-ligation with mIgM, interferes in the release of Ca2+ from intracellular stores.

Antibodies, Monoclonal↗
PubMed1995

The SCID mouse as a model for multiple myeloma.

The SCID mouse was investigated as a potential animal model for human multiple myeloma (MM). Duplicate samples of bone marrow mononuclear cells (BMMC) and/or peripheral blood mononuclear cells (PBMC) of six MM patients in different clinical phases and one patient with monoclonal gammapathy of undetermined significance (MGUS) were injected intraperitoneally into SCID mice. Human immunoglobulins (Ig) in the SCID sera were quantified with a light-chain isotype-specific ELISA, and their monoclonality biochemically characterized, using a sensitive immunoblotting technique after agar gel electrophoresis. Successful transplantation of bone marrow derived-tumour cells in SCID mice was obtained with BMCC of two MM patients with progressive disease. Human plasma cells were detected in the mesenteric fat tissue around the pancreas and the spleen. This model in SCID mice may facilitate studies on processes involved in tumour progression and provides a new tool for therapeutic approaches in MM.

Adult↗
PubMed1994

Primary tumor cells of myeloma patients induce interleukin-6 secretion in long-term bone marrow cultures.

Long-term bone marrow cultures (LTBMC) from patients with multiple myeloma (MM) and normal donors were analyzed for immunophenotype and cytokine production. Both LTBMC adherent cells from myeloma and normal donor origin expressed CD10, CD13, the adhesion molecules CD44, CD54, vascular cell adhesion molecule 1, very late antigen 2 (VLA-2), and VLA-5, and were positive for extracellular matrix components fibronectin, laminin, and collagen types 3 and 4. LTBMC from myeloma patients and normal donors spontaneously secreted interleukin-6 (IL-6). However, levels of IL-6 correlated with the stage of disease; highest levels of IL-6 were found in LTBMC from patients with active myeloma. To identify the origin of IL-6 production, LTBMC from MM patients and normal donors were cocultured with BM-derived myeloma cells and cells from myeloma cell lines. IL-6 was induced by plasma cell lines that adhered to LTBMC such as ARH-77 and RPMI-8226, but not by nonadhering cell lines U266 and FRAVEL. Myeloma cells strongly stimulated IL-6 secretion in cocultures with LTBMC adherent cells from normal donors and myeloma patients. When direct cellular contact between LTBMC and plasma cells was prevented by tissue-culture inserts, no IL-6 production was induced. This implies that intimate cell-cell contact is a prerequisite for IL-6 induction. Binding of purified myeloma cells to LTBMC adherent cells was partly inhibited by monoclonal antibodies against adhesion molecules VLA-4, CD44, and lymphocyte function-associated antigen 1 (LFA-1) present on the plasma cell. Antibodies against VLA-4, CD29, and LFA-1 also inhibited the induced IL-6 secretion in plasma cell-LTBMC cocultures. In situ hybridization studies performed before and after coculture with plasma cells indicated that LTBMC adherent cells produce the IL-6. These results suggest that the high levels of IL-6 found in LTBMC of MM patients with active disease are a reflection of their previous contact with tumor cells in vivo. These results provide a new perspective on tumor growth in MM and emphasize the importance of plasma cell-LTBMC interaction in the pathophysiology of MM.

Antibodies, Monoclonal↗
PubMed1993

Host cell membrane proteins on human immunodeficiency virus type 1 after in vitro infection of H9 cells and blood mononuclear cells. An immuno-electron microscopic study.

Human immunodeficiency virus type 1 (HIV-1)-infected H9 and blood mononuclear cells (MNCs) were studied by immunogold electron microscopy for the presence of HIV-1 gag p24 protein, env gp41 and gp120 proteins, and host cell molecules CD4, CD11a, CD25, CD54, CD63, HLA class I and HLA-DR. Uninfected H9 cells and MNC membranes labelled for CD4, HLA class I and class II, and, at low density, CD11a and CD54; lysosomal structures in the cytoplasm labelled for CD63. The infected cell surface showed immunolabelling for HIV-1 proteins, as did budding particle-like structures. Immunogold labelling of the cell membrane for CD4 was almost non-existent. The level of immunolabelling for CD11a and CD54 on infected cells was greater than that on uninfected cells; this is presumably related to a state of activation during virus synthesis. Budding particle-like structures and free virions in the intercellular space were immunogold-labelled for all host cell markers investigated. This was confirmed by double immunogold labelling using combinations of HIV-1 gag p24 labelling and labelling for the respective host cell molecule. We conclude that virions generated in HIV-1-infected cells concentrate host-derived molecules on their envelope. Also molecules with a prime function in cellular adhesion concentrate on the virion.

Antigens, CD↗
PubMed1993

A novel flow cytometric assay for the quantification of adhesion of subsets within a heterogeneous cell population; analysis of lymphocyte function-associated antigen-1 (LFA-1)-mediated binding of bone marrow-derived primary tumour cells of patients with multiple myeloma.

In a previous study the expression of the adhesion molecule LFA-1 on tumour cells in patients suffering from multiple myeloma (MM) was correlated with growth of the malignant plasma cells in vivo. Here we describe a novel in vitro flow cytometric adhesion assay (FCAA) which, based on scatter and fluorescence properties, was used to analyse the contribution of the LFA-1/intercellular adhesion molecule-1 (ICAM-1) adhesion pathway in the binding of bone marrow (BM)-derived LFA-1-positive primary tumour cells of patients with MM to interferon-gamma (IFN-gamma)-activated, ICAM-1-positive, human venous umbilical endothelial cells (huVEC) in vitro. To validate the FCAA, cells from different myeloma cell lines were labelled with the fluorescent dye CFDA or stained for CD38 expression, and LFA-1-mediated adhesion to IFN-gamma-activated endothelial cells was quantified. Results obtained with the FCAA were compared with a conventional adhesion assay employing 51Cr-labelled cells. Statistical analysis revealed that both assays gave similar results. This allowed analysis of the contribution of LFA-1 to the adhesive potential of malignant plasma cells in bone marrow mononuclear cells (BMMC) from MM patients to IFN-gamma-activated endothelial cells. The results prove that LFA-1 expressed on bone marrow-derived plasma cells from MM patients can be used for cellular adhesion to ICAM-1 expressed on adherent growing cells, and are suggestive for a role of the LFA-1/ICAM-1 adhesion pathway in the pathophysiology of MM. The FCAA described in this study is a generally applicable assay, allowing analysis of the interaction of distinct subpopulations with in vitro grown adherent cells of different origin.

Bone Marrow Cells↗
PubMed1992

Lymphocyte function-associated antigen-1 expression on plasma cells correlates with tumor growth in multiple myeloma.

Lymphocyte function-associated antigen-1 (LFA-1) (CD11a/CD18) expression on bone marrow-derived plasma cells from normal individuals, patients with monoclonal gammopathies of undetermined significance (MGUS), and patients with multiple myeloma (MM) was studied by immunofluorescence microscopy and flow cytometry using a new monoclonal antibody (MoAb) F8.8. This MoAb recognizes the alpha-chain (CD11a) of LFA-1 as determined by immunoprecipitation, and inhibits T-cell-induced cytotoxicity. Although the F8.8 MoAb stains unstimulated peripheral blood T cells with the same mean fluorescence intensity as other anti-CD11a MoAbs, it proved to be superior in detecting CD11a on plasma cells as compared with reference MoAbs. Using the anti-CD11a MoAb F8.8, a strong correlation was found between LFA-1 expression and disease activity in MM, as defined by clinical performance and serum M-protein level. Hardly any LFA-1+ plasma cells were detected in normal individuals, patients with MGUS, and MM patients in a nonactive phase of their disease, while plasma cells of some MM patients with active disease and all patients with fulminant disease expressed LFA-1. Plasma cell LFA-1 expression correlated well with the labeling index (LI) of the tumors in the individual patients. The relation between LFA-1 expression and the tumor growth suggests an involvement of this adhesion molecule in cellular interactions resulting in plasma cell proliferation.

Antibodies, Monoclonal↗
PubMed1992

Expression of members of the immunoglobulin VH3 gene families is not restricted at the level of individual genes in human chronic lymphocytic leukemia.

Previous studies on the repertoire of Ig VH genes utilized in the malignant cells of chronic lymphocytic leukemia (CLL) have suggested a non-random expression pattern. In particular, individual genes from the VH1, VH5, and VH6 gene families have been frequently found in CLL. With regard to other VH gene families, including the large VH3 family which is expressed in greater than 50% of CLL cases, it is unknown whether CLL cells utilize either a broad or a restricted repertoire of VH genes. In the present paper, we analyzed the VH genes expressed in a collection of 11 CLL cases. The results of these experiments demonstrate that there is no apparent restriction in the usage of individual members of the VH3 gene families in CLL.

Base Sequence↗
PubMed1992

Adhesion of subsets of human blood mononuclear cells to endothelial cells in vitro, as quantified by flow cytometry.

Binding of leucocytes to endothelial cells (EC) is essential as an initial step in inflammatory responses. We present a rapid, non-radioactive method to measure adhesion of human lymphoid cells to EC using flow cytometry. Freshly isolated peripheral blood mononuclear cells (PBMC) were allowed to adhere to EC grown in 24-well plates. Non-adhering cells were removed, after which adhering cells and EC were dissociated using trypsin/EDTA. These samples were subsequently analysed by flow cytometry, using scatter properties to distinguish between adhering cells and EC. The ratio of the number of adhering leucocytes and EC was calculated to quantify adhesion. Results of the flow cytometric adhesion assay were comparable to those obtained with a conventional adhesion assay using chromium-labelled cells. We additionally show that by using the flow cytometric adhesion assay, adhesion of lymphocytes and monocytes present within the adhering PBMC can be quantified simultaneously. As a model, the contribution of LFA-1 (CD11a/CD18) and ICAM-1 (CD54) in adhesion of PBMC to EC was studied. It was found that adhesion of lymphocytes and monocytes is regulated differently by phorbol ester and that the relative contribution of LFA-1 and ICAM-1 differs for both cell types.

Antigens, CD↗