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Biomedical subjects

A Tobler

Publications and source records attributed to A Tobler.

At least 127 records · Page 7Linked to original sources
PubMed1991

The polymerase chain reaction: a new tool for the detection of minimal residual disease in haematological malignancies.

The polymerase chain reaction (PCR) is a novel technique for the in vitro amplification of specific short DNA fragments, which permits a selective and up to 10(7) fold enrichment of the target sequence. The method is increasingly being used for the molecular genetic analysis of hereditary, infectious and neoplastic disorders. The use of PCR for the detection of minimal residual disease in particular types of leukaemia or lymphoma, such as chronic myelogenous leukaemia expressing specific BCR/ABL-RNA and follicular non-Hodgkin lymphoma with the chromosomal translocation t(14;18) are reviewed. In acute lymphoblastic leukaemia clone-specific sequences from rearranged antigen receptor genes may be molecular markers suitable for amplification. Although PCR holds great promise for "molecular" staging and follow-up, several technical problems have to be kept in mind, and the clinical relevance of PCR-based evidence of minimal residual disease in haematological malignancies requires further investigation.

False Negative Reactions↗
PubMed1991

[Large cell anaplastic lymphomas in the immunocompromised host].

Large cell anaplastic (LCA) lymphomas are a newly defined tumor entity, which has recently been integrated in the updated Kiel classification. The occurrence of CD30+ LCA lymphoma in the setting of renal transplant patients has so far been reported only once. This report describes two LCA lymphomas of B-cell phenotype in renal transplant patients. The clonal evolution and possible etiologic role of Epstein-Barr Virus (EBV) in LCA lymphoma was studied. Our findings give further evidence that clonal evolution of B-cell populations is a second event in lymphomagenesis and is, at least in the cases studied, preceeded by either reactivated latent or primary EBV-infection with clonal EBV proliferation.

Antigens, CD↗
PubMed1990

Lymphocyte cell lines from vitamin D-dependent rickets type II show functional defects in the 1 alpha,25-dihydroxyvitamin D3 receptor.

Lymphocyte cell lines were established from five patients with vitamin D-dependent rickets, type II (VDDR-II). These lines were established by infection with human T-lymphotrophic virus type I (HTLV-I). Binding of [3H]1 alpha,25-dihydroxyvitamin D3 (1,25(OH)2D3) to its receptor in these cell lines was compared to binding studies using a T-lymphocyte cell line (S-LB1) from a normal individual. The 1,25(OH)2D3 receptor of S-LB1 was comparable to the well-characterized chick intestinal 1,25(OH)2D3 receptor in terms of its ligand binding affinity and capacity, its mobility on 5-20% sucrose gradients, and its adsorption to and elution properties from DNA-cellulose. Three cell lines established from patients with VDDR-II (Rh-VDR, Sh-VDR, and Ab-VDR) showed no specific binding of 1,25(OH)2D3 to a receptor and treatment of the cultured cells with 1,25(OH)2D3 did not stimulate production of 24,25-dihydroxy-vitamin D3 (24,25(OH)2D3), a response which is diagnostic of the presence of a functional 1,25(OH)2D3 receptor. In a fourth cell line, A1-VDR, the receptor for 1,25(OH)2D3 had a low binding capacity and 25(OH)D3-24-hydroxylase activity was not detectable. Induction of 24,25-(OH)2D3 synthesis by 1,25(OH)2D3 was observed in the fifth cell line, designated Ro-VDR, although the sensitivity to hormone treatment was lower than in the control cell line from a normal donor. The capacity of the receptor for 1,25(OH)2D3 was low in Ro-VDR. In all cell lines where 1,25(OH)2D3 binding to a receptor was detectable, the receptor had the typical sedimentation coefficient of 3.7 S on sucrose density gradient analysis. Binding and elution properties to DNA-cellulose, however, differed from normal in both Ro-VDR and A1-VDR cells where elution from DNA-cellulose occurred at a lower salt concentration than is typical of the 1,25(OH)2D3 receptor. While Ro-VDR cells showed typical nuclear localization of the unoccupied 1,25(OH)2D3 receptor, neither the unoccupied nor the occupied receptor from A1-VDR cells was completely localized in the nucleus. In a series of functional studies we found that modulation of the level of the mRNAs coding for both the c-myc oncogene and the growth factor known as granulocyte-monocyte colony stimulating activity by 1,25(OH)2D3 correlated with the 1,25(OH)2D3 receptor status of these cells. Use of these cell lines will facilitate further study of the molecular defect(s) in the receptor for 1,25(OH)2D3 in vitamin D-dependent rickets type II and will allow a correlation with impairment of cellular functions.

24,25-Dihydroxyvitamin D 3↗
PubMed1990

Immunogenotyping with antigen receptor gene probes as a diagnostic tool in childhood acute lymphoblastic leukaemia.

13 cases of childhood acute lymphoblastic leukaemia (ALL) were studied combining cell surface marker analysis with immunogenotyping by Southern blot hybridisation with a panel of antigen receptor gene probes. The immunophenotypes were unequivocal: 7 patients had B-phenotype and 6 patients T-phenotype ALL. In several patients immunogenotypes were not fully consistent with the respective phenotypes. For example, 2 B-cell precursor ALL had rearranged TCR beta chain genes and 2 T-ALL rearrangement of Ig heavy-chain genes. All cases showed clonal rearrangement or deletions within the TCR delta gene locus. TCR delta gene rearrangements might, therefore, serve as markers of clonality but not of B- or T-lineage in immature lymphoid neoplasms. We conclude that in current diagnostic practice immunogenotyping is a supplement rather than an alternative to immunophenotyping by surface marker analysis.

Adolescent↗
PubMed1989

Evidence for a pretranslational defect in hereditary and acquired myeloperoxidase deficiency.

Myeloperoxidase (MPO) is a heme containing enzyme involved in the oxygen-dependent microbicidal activity of human polymorphonuclear leukocytes (PMN). Complete hereditary and acquired MPO deficiencies are defined as lack of peroxidase activity in PMN. Using this criterion, we studied a patient with complete hereditary MPO deficiency, and a MPO deficient variant cell line of HL-60 (HL-60-A7), which we used as a model for acquired MPO deficiency. Western blot analysis showed complete absence of mature and precursor protein of MPO both in PMN from the patient and in HL-60-A7 cells. PMN from both parents had one half of normal levels of these proteins. To study further the molecular basis of this defect, we isolated an intron specific probe for MPO and used it and a cDNA probe. Both normal human bone marrow cells and the promyelocytic HL-60 leukemia cells contained MPO mRNA species of 2.8, 3.3, approximately 4, and greater than 8 kilobase (kb). The transcripts of greater than 8 and approximately 4 kb contained sequences hybridizing to a probe specific for intron 7 of the MPO gene. Bone marrow cells of the MPO deficient patient contained two species of heterogeneous nuclear (hn) RNA of greater than 8 and approximately 4 kb, but only trace amounts of the normal sized 3.3 kb MPO mRNA and undetectable 2.8 kb MPO mRNA. HL-60-A7 cells contained both greater than 8 and approximately 4 kb hnRNA, but only small amounts of normal sized 2.8 kb MPO mRNA and undetectable levels of the 3.3 kb mRNA. Southern blot analyses revealed no gross alteration of the MPO gene in both cases. Our results suggest that a pretranslational defect is one mechanism leading to MPO deficiency.

Adult↗
PubMed1988

[Vitamin D as an immuno-hematopoietic hormone. New perspectives on a previously known substance].

1,25-dihydroxyvitamin D3 (1.25[OH]2D3), the most active metabolite of vitamin D3, plays an important role in bone and mineral metabolism. There is growing evidence that the vitamin D endocrine system may be important in other systems as well: 1,25(OH)2D3 is synthesized in extrarenal tissue. Macrophages from both normal human individuals and patients with sarcoidosis are capable of producing 1,25(OH)2D3. Specific receptors for 1,25(OH)2D3 are present in a number of cells and tissues other than those of the classical target organs (bone, intestine and kidney). The possible role of 1,25(OH)2D3 in both the modulation of immune responses and normal and leukemic hematopoiesis is discussed.

Calcitriol↗
PubMed1988

[Induction of myelogenous differentiation: a therapeutic possibility for preleukemia and acute leukemia?].

Human acute myelogenous leukemia often arises from a transformation at the stem cell level leading to a block in differentiation. The malignant cell, therefore, remains in the proliferative pool and rapidly accumulates. In preleukemia, also known as myelodysplastic syndromes, the malignant clone is already established, leading to disturbed hematopoiesis. One therapeutic approach, therefore, might be to overcome this block in differentiation and thus shift the cell from the proliferative into the differentiating pool. For several years now research in leukemia has focused on study of the proliferation and differentiation of normal and leukemic hematopoietic cells. Numerous substances have been identified which are able to trigger differentiation in myeloid cells, including the retinoids, vitamin D, tumor necrosis factor and hematopoietic hormones. The possible role of these agents in the treatment of preleukemia and acute myelogenous leukemias is discussed.

Cell Differentiation↗
PubMed1988

Regulation of gene expression of myeloperoxidase during myeloid differentiation.

Myeloperoxidase (MPO) is a major heme enzyme involved in inflammatory responses of polymorphonuclear leukocytes. Using cDNA and intron specific probes for MPO we studied the regulation of MPO expression during myeloid differentiation of the promyelocytic HL-60 leukemia cell line. Mature MPO mRNA species of 3.3, 2.8 and 1.6 kb and heterogeneous nuclear (hn) RNA of greater than 8 and approximately 4 kb were observed in wildtype HL-60 cells. Induction of differentiation of the cells towards either granulocytes or macrophages resulted in a profound decrease (greater than 95%) in the concentration of MPO mRNA levels, showing that gene expression of MPO mRNA is closely linked to the stage of development of myeloid cells. Studies using normal and leukemic hematopoietic cells confirmed these findings and showed that myeloblasts and promyelocytes contain MPO mRNA. Rate of transcription of MPO was measured by a nuclear run-on assay in wild-type and day 3- and day -4 differentiated HL-60 cells and was nearly the same in all three. In contrast, rate of transcription of c-myc in the same nuclei became almost undetectable with induction of differentiation. Overall transcription decreased by 60% and 80% on day 3 and 4 of differentiation, respectively, compared to wild-type cells. Stability of mature MPO mRNA was also measured and found to be the same in wild-type and differentiated HL-60. Half-life of MPO hnRNA was less than or equal to 30 min in wild-type HL-60; nevertheless, this hnRNA was easily detectable 3 days after induction of differentiation of these cells. Taken together, the results show that decreased expression of MPO mRNA with differentiation occurs in part post-transcriptionally, possibly due to a failure in RNA processing. In addition, as overall transcription decreases during differentiation, MPO transcription is concomitantly reduced. This indicates that transcriptional and post-transcriptional mechanisms cooperate in the control of MPO gene expression.

Cell Differentiation↗
PubMed1988

Transcriptional and posttranscriptional modulation of myeloid colony-stimulating factor expression by tumor necrosis factor and other agents.

Granulocyte (G) and granulocyte-macrophage (GM) colony-stimulating factors (CSF) are necessary for proliferation and differentiation of myeloid hematopoietic cells. Fibroblasts stimulated by tumor necrosis factor alpha (TNF alpha) and several other agents are a rich source of these CSF. The GM-CSF synthesized by these cells had the same molecular weight and glycosylation pattern as that produced by activated T lymphocytes, as shown by [35S]methionine labeling studies. Northern (RNA) blot analysis showed that the fibroblasts had trace levels of G- and GM-CSF mRNA. Both G- and GM-CSF mRNA concentrations coordinately increased after exposure of the cells to TNF alpha (greater than or equal to 5 ng/ml), 12-O-tetradecanoylphorbol 13-acetate (TPA) (greater than or equal to 5 x 10(-10) M), or cycloheximide (20 micrograms/ml). Both TNF alpha and TPA increased levels of G- and GM-CSF mRNA in the absence of new protein synthesis. Transcriptional run-on studies demonstrated that fibroblasts constitutively transcribed GM-CSF, and transcription was enhanced 3.0-fold by TNF alpha and 2.5-fold by TPA and was unchanged by cycloheximide. The stability of G- and GM-CSF transcripts was determined after exposure of the cells to actinomycin D; the half-lives of G- and GM-CSF mRNA in unstimulated cells were less than 0.25 h and were increased 2- to 16-fold in cells cultured with TNF, TPA, or cycloheximide. In summary, both transcriptional and posttranscriptional signals acted coordinately to modulate the levels of G- and GM-CSF mRNAs in fibroblasts.

Bone Marrow↗
PubMed1988

1,25-Dihydroxyvitamin D3 modulates the expression of a lymphokine (granulocyte-macrophage colony-stimulating factor) posttranscriptionally.

We recently showed that 1,25(OH)2D3 sensitively inhibited the expression of granulocyte-macrophage colony-stimulating factor (GM-CSF) in normal human mitogen-activated peripheral blood lymphocytes and in the human T lymphotropic virus I immortalized T cell line known as S-LB1 at the levels of both mRNA and protein. Using S-LB1 cells as a model system the present paper identifies at least in part the mechanisms by which 1,25(OH)2D3 regulates the expression of GM-CSF. Time-course studies demonstrated that by 6 and 48 h of exposure of S-LB1 cells to 1,25(OH)2D3 (10(-8) M) the GM-CSF mRNA levels were reduced by 50 and 90%, respectively. Studies using cycloheximide as a protein synthesis inhibitor showed that the inhibitory action of 1,25(OH)2D3 on GM-CSF expression was dependent on new protein synthesis. In vitro nuclear run-on assays demonstrated that 1,25(OH)2D3 (10(-8) M) did not change the rate of transcription of the GM-CSF gene. The t1/2 of GM-CSF mRNA, however, was profoundly reduced by 1,25(OH)2D3 when transcription was blocked by actinomycin D compared with the half-life of GM-CSF in the presence of actinomycin D alone (t1/2, less than 0.5 and 4 h, respectively). Taken together, these results demonstrate that 1,25(OH)2D3 regulates expression of the lymphokine GM-CSF posttranscriptionally by influencing the stability of GM-CSF mRNA.

Calcitriol↗
PubMed1987

1 alpha,25-Dihydroxyvitamin D3 inhibits gamma-interferon synthesis by normal human peripheral blood lymphocytes.

1 alpha,25-Dihydroxyvitamin D3 [1,25-(OH)2D3], the biologically active metabolite of vitamin D3, inhibited synthesis of gamma-interferon (IFN-gamma) by phytohemagglutinin-activated peripheral blood lymphocytes (PBLs). A significant reduction of IFN-gamma protein levels in PBL culture medium was achieved with a physiologic 1,25-(OH)2D3 concentration (0.1 nM). 1,25-(OH)2D3 also inhibited accumulation of IFN-gamma mRNA in activated PBLs in a dose-dependent fashion. The ability of 1,25-(OH)2D3 to modulate IFN-gamma protein synthesis was unaltered in the presence of high concentrations of recombinant human interleukin 2. The suppression of IFN-gamma synthesis by PBLs was specific for 1,25-(OH)2D3; the potencies of other vitamin D3 metabolites were correlated with their affinities for the cellular 1,25-(OH)2D3 receptor. The time course of 1,25-(OH)2D3 receptor expression in phytohemagglutinin-activated PBLs was correlated with the time course of 1,25-(OH)2D3-mediated inhibition of IFN-gamma synthesis. In selected experiments, T-lymphocyte-enriched cell preparations were utilized. In these experiments, 1,25-(OH)2D3 was equally active as in PBL preparations. Finally, we examined the effects of 1,25-(OH)2D3 on the constitutive IFN-gamma production by two human T-lymphocyte lines transformed by human T-lymphotropic virus type I. The cell lines were established from a normal donor (cell line S-LB1) and from a patient with vitamin D-dependent rickets type 2 (cell line Ab-VDR). IFN-gamma synthesis by S-LB1 cells was inhibited in a dose-dependent fashion by 1,25-(OH)2D3, whereas IFN-gamma synthesis by Ab-VDR cells was not altered by 1,25-(OH)2D3. The data presented in this study provide further evidence for a role of 1,25-(OH)2D3 in immunoregulation.

Calcitriol↗
PubMed1987

Differentiation of human acute myelogenous leukemia cells: therapeutic possibilities.

Human myeloid leukemia cells have a growth advantage over normal cells because they do not differentiate into functional end-cells but remain in the proliferative pool. Several agents have been identified as inducers of differentiation of leukemia cells; among them are the retinoids, 1 alpha,25-dihydroxyvitamin D3 and human tumor necrosis factor alpha, which will be discussed in the following chapter.

Adolescent↗
PubMed1987

Granulocyte-macrophage colony-stimulating factor. Sensitive and receptor-mediated regulation by 1,25-dihydroxyvitamin D3 in normal human peripheral blood lymphocytes.

We show that 1,25-dihydroxyvitamin D3 (1,25[OH]2D3), the most hormonally active metabolite of vitamin D3, modulates sensitively and specifically both the protein and messenger RNA accumulation of the multilineage growth factor granulocyte-macrophage colony-stimulating factor (GM-CSF). The regulation of GM-CSF expression is seen in both normal human mitogen-activated T lymphocytes and T lymphocytes from a line (S-LB1) transformed with human T cell lymphotropic virus 1 (HTLV-1). In contrast, cells from a HTLV-1 transformed T lymphocyte line (Ab-VDR) established from a patient with vitamin D-resistant rickets type II with undetectable 1,25(OH)2D3 cellular receptors are resistant to the action of 1,25(OH)2D3. Inhibition of GM-CSF expression by 1,25(OH)2D3 can occur independently of interleukin 2 regulation and is probably mediated through cellular 1,25(OH)2D3 receptors. We conclude that 1,25(OH)2D3 may be important in the physiology of hematopoiesis.

Calcitriol↗
PubMed1987

In vitro interaction of recombinant tumor necrosis factor alpha and all-trans-retinoic acid with normal and leukemic hematopoietic cells.

Both human recombinant tumor necrosis factor alpha (TNF alpha) and all-trans-retinoic acid (RA) inhibit the in vitro clonal growth of human myeloid leukemic cells. We investigated the in vitro interaction of TNF alpha and RA with normal and a variety of leukemic myeloid cells. With the promyelocytic HL-60 cells, TNF alpha (greater than or equal to 2.5 U/mL) in combination with RA synergistically inhibited clonal growth; TNF alpha at lower concentrations (less than or equal to 1 U/mL) plus RA (10(-9) mol/L) were antagonistic in their inhibition of growth. The ability of RA (10(-8) mol/L) plus TNF alpha (2.5, 5 U/mL) to enhance differentiation of HL-60 cells paralleled their ability to inhibit clonal growth of these cells. In addition, RA (10(-9) to 10(-7) mol/L) increased the number of TNF alpha receptors on HL-60 cells 1.3- to 1.7-fold without changing the affinity for the TNF alpha receptor. With the more immature KG-1 myeloblasts, concentrations of TNF alpha greater than 10 U/mL synergistically interacted with RA to inhibit clonal growth; at lower concentrations of TNF alpha (less than 10 U/mL), RA appeared to inhibit the expected effect of TNF alpha. KG-1 cells were not induced to differentiate with either agent alone or in combination. With four of nine leukemic patients, TNF alpha in combination with RA (10(-7) mol/L) inhibited leukemic clonal growth to a greater extent than each agent alone. No marked effect of the combined treatment was seen in two other patients. The RA reversed the inhibitory action of TNF alpha on normal human granulocyte-macrophage colony forming cells (GM-CFC) and on clonal growth of leukemic cells from three patients. Our study suggests that TNF alpha and RA interact in a complex manner with normal and leukemic hematopoietic cells.

Cell Differentiation↗