Biomedical subjects

N Le Marer

Publications and source records attributed to N Le Marer.

10 recordsLinked to original sources

PubMed2001

Alpha-2,6-sialylation regulation in CD34+ progenitor cells in the human bone marrow and granulocyte colony-stimulating factor mobilization.

The use of peripheral blood (PB) progenitor cells to reconstitute hematopoiesis after high-dose chemotherapy is now common practice in the treatment of malignancies. Growth factors such as granulocyte colony-stimulating factor (G-CSF) induce high proliferation and self-renewal within the stem cell compartment of the bone marrow. This is followed by the release of a very high number of progenitor cells into the peripheral blood, the mechanism of which remains unclear. Previously, we have showed that high cell-surface sialylation reduces matured myeloid attachment to the bone marrow stroma, which is likely to help their release into the peripheral blood. Consequently, we decided to investigate the possibility that sialylation may also contribute to the CD34(+) cell release into the peripheral blood during G-CSF treatment. We found that G-CSF-mobilized PB CD34(+) cells exhibit an increase in the sialyltransferase ST6Gal-I mRNA level. The analysis of the heterogeneity of ST6Gal-I transcripts showed a predominance of the Y form in both bone marrow (BM) and G-CSF PB CD34(+) cells. Higher levels in ST6Gal-I mRNA resulted in a higher expression of alpha-2,6-sialylation on the surface of G-CSF PB CD34(+) cells when compared to noninduced PB CD34(+) cells but not higher to BM CD34(+) cells. Our present results, together with recent observations, suggest that ST6Gal-I and alpha-2,6-sialylation expression in myeloid cells is tightly dependent on the presence of G-CSF in their environment. Up-regulation of ST6Gal-I together with alpha-2,6-sialylation of cell surface glycoproteins is likely to modulate cellular adherence and survival of progenitor cells.

Antigens, CD34↗

PubMed2000

GALECTIN-3 expression in differentiating human myeloid cells.

Galectin-3 is an endogenous mammalian carbohydrate-binding protein with affinity for ABH group carbohydrate epitopes and polylactosamine glycans present on cell surface and extracellular matrix glycoproteins. It has been shown to play a role in cell differentiation, morphogenesis, adhesion and cell proliferation regulation. Progenitor cell proliferation in bone marrow depends on stem cell factors including those modulating their adhesion to the bone marrow stroma. The present study shows that the 32 kD galectin-3 is developmentally expressed in human myeloid cells and is strongly upregulated on the cell surface of late mature myeloid cells. Despite the fact that the expression of the galectin-3 is very low in CD34+ early myeloid cell, a 70 kD protein is found by Western blotting using antibodies specific to galectin-3, exclusively in those cells. Finally, exogenous human recombinant galectin-3 binds strongly to CD34+ early myeloid cells and emphasizes granulocyte-colony stimulating factor (G-CSF) driven proliferation in vitro.

Amino Sugars↗

PubMed1999

Up-regulation of alpha2,6 sialylation during myeloid maturation: a potential role in myeloid cell release from the bone marrow.

The mechanisms by which mature myeloid cells are released from the bone marrow into the peripheral blood are not clearly understood. Glycosylation is likely to play an important role, as has been shown in the homing of lymphocytes to lymph nodes and of neutrophils to inflamed endothelia. Cell surface sialylation is an important component of many cellular adhesive interactions, both as ligand-promoting interactions, as occurs in selectin and sialoadhesin-mediated adhesion, and for reducing cell adhesion as in some cancer cells. We have studied the expression of cell surface alpha2,6-linked sialic acid in the maturation of normal bone marrow myeloid cells, the expression of alpha2,6-sialyltransferase mRNA, and the role of sialylation in the adherence of myeloid cells to bone marrow stroma. Our data show that there is a dramatic increase in cell surface alpha2,6-sialylation during the late stage of maturation. This up-regulation is restricted to specific glycoproteins including CD11b and CD18. It is associated with a relative increase in the level of alpha2,6-sialyltransferase mRNA compared with alpha2,3-sialyltransferase mRNA. The changes in mature bone marrow myeloid cells are associated with reduced cell binding to fibronectin and cultured bone marrow stroma. Our data strongly suggest that alpha2,6-sialylation may be important in the interaction between maturing myeloid cells and bone marrow stroma and may govern the release of cells from the bone marrow into the peripheral blood.

Antigens, CD34↗

PubMed1997

Developmental regulation of alpha 1,3-fucosyltransferase expression in CD34 positive progenitors and maturing myeloid cells isolated from normal human bone marrow.

The adhesive interactions of hemopoietic cells within the bone marrow regulate their distribution, growth, and development. Fucosylated structures, of which sialyl Lewis x has been most extensively studied, are important ligands for selectins, but little is known about their function or regulation during normal hemopoietic development. We have studied alpha 1,3-fucosyltransferase activity in CD34 positive progenitors and myeloid cells at different stages of maturation isolated form normal human bone marrow, together with mRNA levels of Fuc-TIV and Fuc-TVII. Enzyme activity measured with H type 2 acceptor was present at all stages but was markedly elevated in fractions of early myeloid cells enriched for promyelocytes, correlating with the appearance of Lewis x on these cells, and thereafter fell progressively as cells matured. Activity measured with 3'sialyllactosamine was present in CD34+ cells and at all stages of maturation. Levels were low in promyelocyte/myelocyte transitional cells and increased, relative to those measured with H type 2, during the later stages of maturation; these changes correlate directly with a maturation-related increase in sialyl Lewis x expression. Using competitive quantitative RT-PCR, mRNA levels of Fuc-TIV and Fuc-TVII were similar in CD34+ cells, early myeloid and late myeloid cells. The significance of these findings in relation to fucosyltransferase activity, the synthesis of selectin ligands and differences between normal cells and leukemic cell lines is discussed.

Antigens, CD34↗

PubMed1996

Effects of the carbohydrate-binding protein galectin-3 on the invasiveness of human breast carcinoma cells.

Galectin-3 is a Mr 30,000 protein with carbohydrate-binding specificity for type I and II ABH blood group epitopes and polylactosamine glycans expressed on cell surface and extracellular matrix glycoproteins such as laminin. Cell lines propagated from human normal mammary epithelia and from benign or infiltrating components of primary breast tumours express low levels of galectin-3 in the cytoplasm. However, galectin-3 when added exogenously in solution or when bound within a three-dimensional matrix markedly enhanced the migration of the primary tumour cell lines through a Matrigel barrier. Galectin-3 expression in the cytoplasm and intercellularly on surface membranes was greatly increased in cell lines propagated from malignant ascites and pleural effusions of late stage breast cancer. These cell lines were non-invasive in the Matrigel assay and exogenous galectin-3 had no enhancing effect on invasiveness. These results suggest that galectin-3 could play multiple roles in cell metastasis at an early invasive stage by acting in a paracrine manner to stimulate cell migration through an extracellular matrix, and in later stage cancers in synergy with other mediators of cell-cell aggregation. However, endogenous galectin-3 expression in human breast cancers is not correlated directly with their invasive potential in vitro.

Antigens, Differentiation↗

PubMed1995

High alpha-2,6-sialylation of N-acetyllactosamine sequences in ras-transformed rat fibroblasts correlates with high invasive potential.

Through cloning experiments with the FRras EJ4 cell line, previously described to exhibit a Sambucus nigra agglutinin (SNA)+ phenotype, three clones with a SNA- phenotype were isolated. All the selected SNA+ and SNA- clones expressed the ras oncoprotein and cloned in soft agar with the same efficiency. We were interested in studying the adhesion and invasion properties of the FRras cells presenting a SNA + or - phenotype. They were first compared in their biochemical properties and we found that FRras SNA- were characterized by a low alpha-2,6-sialylation of their cell surface glycoproteins and a low beta-galactoside alpha-2,6 sialytransferase activity. Using in vitro invasion assays, FRras cells exhibiting a low alpha-2,6-sialylation on their surface were found to have a low invasive potential compared to their counterpart SNA+. FRras SNA-clones exhibit a different morphology from that of FRras SNA+ clones. Moreover, homotypic aggregation assays indicated that FRras SNA- were more cohesive with each other and adhesion assays showed that they were more adhesive to fibronectin.

Amino Sugars↗

PubMed1992

Comparison of sialyl- and alpha-1,3-galactosyltransferase activity in NIH3T3 cells transformed with ras oncogene: increased beta-galactoside alpha-2,6-sialyltransferase.

Previous studies have indicated that transfection of NIH3T3 cells with the ras oncogene induced modifications of the terminal glycosylation of N-linked glycans which appeared in the early stage after transfection. These changes affected especially the terminal part of N-linked glycans which is substituted with alpha-1,3-Gal residues in NIH3T3 and with Neu5Ac residues in the ras-transformed counterpart. We have transformed NIH3T3 cells with the human c-Ha-ras oncogene, evaluated tumorigenicity and metastatic capacity in vivo and compared alpha-1,3-galactosyltransferase, alpha-2,3- and alpha-2,6-sialyltransferases activities. By using different specific acceptors, we detected the enhancement of sialic acid transfer in transformed cells while the activity of alpha-1,3-galactosyltransferase remained unchanged. We showed that the higher sialyltransferase activity was due to the increase of beta-galactoside alpha-2,6-sialyltransferase in ras-transfectant although alpha-2,3-sialyltransferase was weakly expressed in these cells. On the basis of binding of different lectins, we correlated these observations with changes of protein glycosylation. We concluded that altered glycosylation of ras-transformed NIH3T3 is the result of a competitive effect of the enzymes acting for terminal glycosylation of N-linked glycans and the reflection of the higher expression of alpha-2,6-sialyltransferase.

Animals↗

PubMed1992

The c-Ha-ras oncogene induces increased expression of beta-galactoside alpha-2, 6-sialyltransferase in rat fibroblast (FR3T3) cells.

Alteration in cell surface carbohydrates, and in particular cell surface sialylation, have been known to occur during oncogenic transformation. To examine the basis for such changes, we have transformed the rat fibroblast cell line FR3T3 with the oncogenes c-Ha-ras EJ, v-mycOK10, v-src, polyoma virus middle T or the transforming bovine papilloma virus 1 (BPV1), and measured the sialytransferase activities of cellular lysates. We found that, in contrast to all other oncogenes examined, c-Ha-ras induced a striking increase in beta-galactoside alpha-2,6-sialytransferase (Gal alpha-2,6-ST) activity in FR3T3 cells. This increase in Gal alpha-2,6-ST activity resulted in the increased expression of cell surface alpha-2,6-linked sialic acid on cell surface glycoconjugates, as determined by cell staining with fluorescein-labelled Sambucus nigra agglutinin. Immunoprecipitation and immunofluorescence experiments revealed that the increase in Gal alpha-2,6-ST activity was due to an elevation of expression of the enzyme. Moreover, Northern analysis suggested that the increased expression of this enzyme was the result of an increase in the steady-state mRNA level of the Gal alpha-2,6-ST gene. These results support the notion that alterations seen in cell surface glycoconjugates during oncogenic transformation can be the result of altered expression of glycosyltransferases.

Animals↗

PubMed1991

[Modifications of sialylation in BHK 21/C13 cells after in vitro transfection by c-Ha-ras human oncogene].

A Hamster kidney fibroblast cell line (BHK 21/C13) has been transfected by c-Ha-ras human oncogene. The expression of the oncogene significantly modified the global sialytransferase activity of the cell extract. This activity is enhanced on an average 2.5 fold whatever the acceptor. In addition, the proportion of cell-surface associated N-glycolylneuraminic acid is enhanced in transfectants, the ratio N-acetylneuraminic acid/N-glycolylneuraminic acid decreases from 7.10 to 2.80. These results suggest that a tight relationship exists, in c-Ha-ras transfected BHK cells, between the expression of the oncogene and the neuraminic acid metabolism as well as a gene regulation of glycoconjugate sialylation.

Animals↗

PubMedDate not supplied

Comparison of in vitro invasiveness of human breast carcinoma in early or late stage with their malignancy in vivo.

Different in vitro invasion assays have been established to assess tumour cell invasiveness. We compared the invasiveness of previously described cell lines from human breast cancer that are derived from cancers in an early or late stage of malignancy, by three different in vitro systems. First, we evaluated the capacity of the cells to go through a Matrigel barrier in a Boyden chamber, and in a second assay their ability to migrate in a thick layer of collagen. These experiments showed that early stage cells were more motile than late stage cells. By a third assay, we tested the ability of cells to invade chick heart fragment tissue and found none of the cells to be invasive.

Animals↗