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M Amiot

Publications and source records attributed to M Amiot.

At least 37 records · Page 2Linked to original sources
PubMed1998

The absence of CD56 (NCAM) on malignant plasma cells is a hallmark of plasma cell leukemia and of a special subset of multiple myeloma.

In this study, we show that malignant plasma cells from patients with either primary (n=12) or secondary (n=15) plasma cell leukemia (PCL) do not express CD56 at all, neither in the bone marrow nor the peripheral blood in 81% of cases. On the other hand, multiple myeloma (MM) at diagnosis overexpress it in 63 of 94 (67%) cases (P=0.0001). In three secondary PCL evaluated serially, CD56 was also lacking at diagnosis showing that CD56 is not downregulated at the end stage of the disease but rather not upregulated in this subset of patients. This last concept is strengthened by the observation that 29% of MM patients lacking CD56 or weakly expressing it at diagnosis present a detectable leukemic phase vs 11% only in CD561 MM (P=0.06). Forty percent of all the CD56(-/weak) malignant plasma cell disorders present or develop a leukemic phase vs only 15% of CD56+ cases (P < 0.008). CD56(-/weak) MM subset is also associated with a significantly less aggressive osteolytic potential (P=0.012). We conclude that the lack or weak expression of CD56 is a characteristic feature of PCL but also delineates a special subset of MM at diagnosis mainly characterized by a lower osteolytic potential and a trend for malignant plasma cells to circulate in the peripheral blood more overtly.

Bone Marrow↗
PubMed1998

Activation of T cells via CD55: recruitment of early components of the CD3-TCR pathway is required for IL-2 secretion.

It was previously reported that the glycosylphosphatidylinositol (GPI)-anchored CD55 molecule provides a co-stimulatory signal for T lymphocytes and is constitutively associated with the Src-related kinase p56lck. The present studies were undertaken to clarify the mechanism of action of CD55 in T cells. We describe the failure of cross-linking of CD55 alone to induce both the elevation of the intracellular calcium concentration and the tyrosine phosphorylation of PLC-gamma in CD3+ Jurkat cells. By contrast, it is sufficient to induce the phosphorylation of tyrosine residues on p56lck, the TCR-zeta chain as well as ZAP-70. Surprisingly, the observed TCR-zeta and ZAP-70 tyrosine phosphorylations appear delayed compared to stimulation via CD3. Calcium ionophore A23187 in combination with cross-linked CD55 mAb initially caused an acceleration in the kinetic of these two phosphorylation events, followed by IL-2 secretion. Furthermore, transfection of the cytoplasmic domain of TCR-zeta in CD3- Jurkat cells, using a CD16-zeta chimera, demonstrates that CD55-mediated T-cell activation depends on the expression of this chain of the CD3-TCR complex.

Antibodies, Monoclonal↗
PubMed1998

CD28, a marker associated with tumoral expansion in multiple myeloma.

CD28 expression was thoroughly investigated on plasma cells of monoclonal gammopathy of undetermined significance, multiple myeloma (MM), and human myeloma cell lines. CD28+ plasma cells were detected in 19% of 31 monoclonal gammopathy of undetermined significance, 41% of 116 MM, and 100% of 13 human myeloma cell lines. CD28+ myeloma cells were detected in 21 of 79 (26%) MM cases at diagnosis, 13 of 22 (59%) at medullary relapse (P < 0.009), and 14 of 15 (93%) at extramedullary relapse (P = 0.05), including 10 of 10 (100%) secondary plasma cell leukemias (P = 0.05). Serial studies in individual patients confirmed the emergence of CD28+ myeloma cells with tumoral expansion and treatment failure. This was significantly correlated with the expression of CD28 ligand, i.e., CD86 (but not CD80), and with an increase in the proliferative activity (labeling index) of myeloma cells in bone marrow. Whereas the expression of CD56 defines a particular subset of myeloma patients, CD28 is the only antigen for which expression correlates with tumor progression. Our data show that an aggressive compartment of CD28+ and CD86+ myeloma cells emerges during the course of MM in vivo, indicating that CD28 could be aberrantly expressed on highly malignant (possibly mutated) myeloma cells. Conversely, a subset of proliferative plasmablasts coexpressing CD28 and CD86 could be the normal counterpart of the clonogenic myeloma stem cell because a subset of CD28+ plasma cells was observed in 6 of 6 cases of reactive plasmocytosis.

Antigens, CD↗
PubMed1997

Metalloproteinases in multiple myeloma: production of matrix metalloproteinase-9 (MMP-9), activation of proMMP-2, and induction of MMP-1 by myeloma cells.

Multiple myeloma is a very devastating cancer with a high capacity to destroy bone matrix. Matrix metalloproteinases (MMPs) play a critical role in bone remodeling and tumor invasion. In this study, we have investigated the involvement of interstitial collagenase (MMP-1) and gelatinases (MMP-2 and MMP-9) in the biology of multiple myeloma. We show (1) that myeloma cells express MMP-9 and (2) that this expression is not subjected to regulation either by interleukin-6 (IL-6), the major myeloma cell growth factor, or by other cytokines involved in the multiple myeloma cytokine network. In the tumoral environment, we show that bone marrow stromal cells express MMP-1 and MMP-2. Whereas MMP-1 is positively regulated by IL-1beta, tumor necrosis factor-alpha, and Oncostatin M, MMP-2 is not modulated by any of these cytokines. To evaluate whether myeloma cells can modify the bone marrow stromal environment, we have examined these MMP activities in coculture. Interestingly, we have observed an upregulation of MMP-1 and a partial conversion of the proMMP-2 into its activated form. We conclude that the increase of MMP activity produced or induced by myeloma cells in these cocultures could favor bone resorption and tumor invasion. Inhibition of such activities could represent a new therapeutical approach in multiple myeloma.

Antineoplastic Agents↗
PubMed1997

The retinoblastoma susceptibility gene RB-1 in multiple myeloma.

Genetic mechanisms leading to the development of multiple myeloma (MM) remain poorly understood. Given the frequency of chromosome 13 deletion in MM and the localization in 13q14 of the retinoblastoma susceptibility gene RB-1, an involvement of RB-1 in MM pathogenesis has been proposed. Moreover, interleukin-6 (IL-6) has been shown to be the main growth factor for MM in vitro and in vivo. The product of the RB-1 gene (pRB) can down-regulate IL-6 gene expression. Absence of pRB may then induce an autocrine IL-6 expression in myeloma cells and contribute to the autonomous growth of MM. As assessed in this review, heterozygous deletion of RB-1 is very common in MM but does not alter gene transcription and protein expression. Nevertheless, homozygous deletion of RB-1 has been identified in some MM patients with advanced disease and in the IL-6-autocrine human myeloma cell line U266. Thus, even if inactivation of RB-1 appears to be only a rare and late oncogenic event in MM and is not likely to represent the main mechanism involved in IL-6 up-regulation in MM, definitive assessment of the actual role played by RB-1 in MM pathogenesis still needs further investigation particularly the examination of pRB function.

Cell Division↗
PubMed1996

Myeloma cell growth arrest, apoptosis, and interleukin-6 receptor modulation induced by EB1089, a vitamin D3 derivative, alone or in association with dexamethasone.

We have previously shown that malignant plasma cells expressed the specific receptor for 1,25-dihydroxyvitamin D3 and that this derivative could significantly inhibit the proliferation of such malignant cells. More recently, new vitamin D3 derivatives have been generated with extraordinarily potent inhibitory effects on leukemic cell growth in vitro. These new data prompted us to (re)investigate the capacity of such new vitamin D3 derivatives to inhibit myeloma cell growth in comparison with that of dexamethasone, a potent antitumoral agent in multiple myeloma. In the current study, we show that EB1089, a new vitamin D3 derivative, (1) induces G1 growth arrest of human myeloma cells, which is only partially reversed by interleukin-6 (IL-6); (2) induces apoptosis in synergy with dexamethasone, IL-6, leukemia-inhibitory factor, and Oncostatin M, with an agonistic anti-gp130 monoclonal antibody being unable to prevent this apoptosis; (3) downregulates both the gp80 (ie, the alpha chain of the IL-6 receptor [IL-6Ralpha]) expression on malignant plasma cells and the production of soluble IL-6Ralpha, and finally (4) inhibits the deleterious upregulation of gp80 expression induced by dexamethasone while limiting the dexamethasone-induced upregulation of gp130 expression. Considering that these in vitro effects of EB1089 have been observed at doses obtainable in vivo (without hypercalcemic effects), our present data strongly suggest that EB1089 could have a true interest in the treatment of multiple myeloma, especially in association with dexamethasone.

Antigens, CD↗
PubMed1996

CD11a-CD18 and CD102 interactions mediate human myeloma cell growth arrest induced by CD40 stimulation.

We have recently demonstrated that the CD40 molecule was expressed on both normal human plasma cells and most malignant plasma cells, i.e., myeloma cells. Thus, we have investigated its putative role in the proliferation of myeloma cells. We report that 7 of 15 myeloma cell lines were CD40+ but only one, XG2, presented a high level of CD40 expression. We show that the CD40 stimulation by anti-CD40 monoclonal antibodies (mAbs) of the interleukin 6-dependent myeloma cell line XG2 induced a total inhibition of its proliferation. This inhibition was also observed when cells were either cultured in the "CD40 system," where the anti-CD40 mAb has been immobilized on fibroblasts expressing Fc receptors or in the presence of a soluble chimeric CD40 ligand molecule. This inhibition of proliferation was neither accompanied by differentiation nor apoptosis. Triggering CD40 induced an homotypic aggregation of XG2 cells, and the inhibition of proliferation was totally prevented by a blocking anti-CD18 mAb. Although the CD11a-CD18 ligands, i.e., CD50, CD54, and CD102, were all expressed on XG2 cells, only a blocking anti-CD102 mAb inhibited the CD40-induced growth arrest. Our data demonstrate that CD40 triggering on XG2 cells induced a myeloma cell growth arrest mediated by lymphocyte function-associated antigen 1 and intercellular adhesion molecule 2 interactions.

Antibodies, Monoclonal↗
PubMed1996

Ectopic secretion of osteocalcin, the major non-collagenous bone protein, by the myeloma cell line NCI-H929.

In this study we provide the first evidence that human non-osteoblastic cells secrete the bone-specific protein osteocalcin. We show that the myeloma cell line NCI-H929 constitutively produces low amounts of osteocalcin. Furthermore, we demonstrate that this production is strongly enhanced after 1,25(OH)2D3 stimulation. An amplification or a deregulation of the osteocalcin gene could be responsible for the observed phenomenon because NCI-H929 has the unusual characteristic of having at least three chromosomes 1, where the osteocalcin gene was mapped (1q25-q31). It is of interest to note that the patient in whom the NCI-H929 cell line originated never developed osteolytic lesions despite extensive disease apparent at autopsy. Although lytic bone lesions with low osteocalcin serum levels are a common feature of multiple myeloma (MM), a small subset of patients does not develop lytic bone lesions or even demonstrate osteosclerotic MM. This occurrence is associated with high osteocalcin serum levels of unknown origin. In this context, osteocalcin production by immortalized tumor lacking any osteolytic potential could be relevant to the pathophysiology of this particular type of MM.

Blotting, Western↗
PubMed1996

Plasma concentration of apolipoprotein E in intermediate-sized remnant-like lipoproteins in normolipidemic and hyperlipidemic subjects.

Triglyceride-rich lipoprotein (TRL) remnants have been strongly implicated in the pathogenesis of atherosclerosis. To further investigate plasma remnant lipoprotein metabolism, we have determined the plasma concentration of apolipoprotein (apo) E (by polyclonal enzyme-linked immunoassay) in remnant-like lipoproteins, isolated by automated gel filtration chromatography as a fraction intermediate in size between VLDL and HDL. In normolipidemic subjects (n = 12), 1.2 +/- 0.11 mg/dL (33 +/- 2%, mean +/- SE) of total plasma apoE was associated with this fraction (termed ISL apoE). In hypercholesterolemic (type IIa, n = 12), hypertriglyceridemic (type IV, n = 12), and mixed hyperlipidemic (type IIb, n = 12) subjects, mean ISL apoE concentrations were 2.1 +/- 0.2, 2.5 +/- 0.2, and 3.8 +/- 0.4 mg/dL, respectively (P < .001 versus normal values) (45 +/- 2%, 32 +/- 2%, and 44 +/- 2% of total). ISL apoE was 8.7 +/- 1.4 mg/dL (42 +/- 3%) in type III dyslipidemic subjects (apoE2/2, n = 8). ISL apoE was positively correlated with plasma triglyceride (r = .41, P < .01), and at any given level of plasma triglyceride, subjects with an apoE2/2 or apoE3/2 phenotype tended to have a higher concentration of ISL apoE (P < .01) than apoE3/3 or E4/3 individuals. ISL apoE was also correlated (P < .001) with total plasma cholesterol (r = .66), TRL cholesterol (r = .49), TRL apoE (r = .47), LDL apoB (r = .42), and LDL+HDL triglyceride (r = .74). These results suggest that (1) a significant proportion of plasma apoE resides within an intermediate-sized remnant-like lipoprotein fraction in both normolipidemic and hyperlipidemic subjects; (2) plasma remnant lipoprotein accumulation is associated with an elevation in ISL apoE concentration; and (3) ISL apoE concentration is significantly correlated with various proatherogenic lipid parameters and may itself be a potentially important atherogenic index.

Adult↗
PubMed1995

Myeloma cells upregulate interleukin-6 secretion in osteoblastic cells through cell-to-cell contact but downregulate osteocalcin.

Previous studies have shown that bone marrow, especially the bone microenvironment, may play an important role in the pathogenesis of multiple myeloma (MM). To elucidate the relationship between myeloma cells and bone cells, mainly osteoblasts, we have established a coculture system between two interleukin-6 (IL-6)-dependent myeloma cell lines, XG1 and XG6, and the osteosarcoma cell lines Saos-2 and MG63. Both osteosarcoma cell lines have retained major functions of normal osteoblasts; principally, the capacity to produce hematopoietic growth factors (including IL-6) and osteocalcin, a noncollagenic protein essential in the bone formation process. Because IL-6 is a critical growth factor in MM, we have examined the IL-6 osteoblastic cell production in our coculture system. XG1 cells strongly upregulate IL-6 production by MG63 and Saos-2 cells. Of major interest, the triggering of IL-6 is totally dependent on the physical contact between myeloma cells and osteoblastic cells, contact that is partly mediated by CD44, CD56, and fibronectin interactions. Osteocalcin production by MG63 and Saos-2 cells has previously been shown to be dependent on 1,25-(OH)2D3. We demonstrate that XG1 and XG6 cells reduced the amount of osteocalcin in MG63 coculture cell supernatants, a reduction that is partly mediated by a soluble factor and by cell-to-cell contact. Notably, whereas one of the myeloma cell lines, XG6, has lost its capacity to stimulate IL-6 production by osteoblastic cell lines, both XG1 and XG6 cell lines remain able to reduce the osteocalcin amount, indicating that IL-6 and osteocalcin levels are regulated by two different pathways. In conclusion, these data strongly support the concept that the bone microenvironment is directly modified by contact with myeloma cells and are consistent with the characteristics observed in vivo in patients with MM patients, ie, abnormally high IL-6 and low osteocalcin levels, respectively.

Calcitriol↗
PubMed1995

Adhesion molecules on human myeloma cells: significant changes in expression related to malignancy, tumor spreading, and immortalization.

In order to evaluate putative changes of major adhesion molecule expression on plasma cells (PCs) associated with malignant transformation, tumor spreading, and immortalization, we have quantified and compared the expression of CD56, CD44, CD11a, CD49e, and CD45 RO/RA on normal PCs, malignant PCs from multiple myeloma patients in chronic phase, in accelerated phase with or without extramedullary progression, and from human myeloma cell lines. Plasma cell phenotype was defined with the use of two-color immunofluorescence in combination with B-B4 or anti-CD38 antibodies. We found that all the adhesion antigens were expressed on normal PCs. Malignancy was characterized by an overexpression of CD56, whereas extramedullary spreading was associated with a dramatic down expression of CD56. Although CD44 remained unchanged, the subpopulation of PCs expressing CD11a, CD49e, and CD45RA/RO were significantly reduced during malignancy, and each of these negative subpopulations increased during disease acceleration. We demonstrated that CD11a and CD49e expression were correlated and defined the same subpopulation of PCs. The phenotype of HMCLs was similar to the expression profile of patients in accelerated phase with extramedullary spreading. In conclusion, we show that significant changes of PC phenotype were associated with malignancy, were correlated with the disease evolution, and could be of diagnostic and prognostic value in individuals with monoclonal gammopathy and patients with multiple myeloma.

Antigens, CD↗
PubMed1995

High incidence of deletions but infrequent inactivation of the retinoblastoma gene in human myeloma cells.

We have studied the retinoblastoma (RB-1) susceptibility gene status and pRB expression in 22 human myeloma cell lines (HMCL) and in 10 patients with advanced multiple myeloma (MM). Deletions of the RB-1 gene were observed in 81% (17/21) of the informative HMCL, regardless of their paracrine or autocrine interleukin-6 (IL-6) status. Among the deleted HMCL, only one (U266) had a biallelic deletion and lacked pRB expression. Monoallelic deletions had no consequence on the RB-1 gene activation and pRB expression. One patient of 10 presented the same biallclic deletion as U266 and six of 10 had monoallelic deletions. We conclude that monoallelic deletions of the RB-1 gene are frequent in HMCL and MM patients but have no consequence on gene activation and pRB expression.

Blotting, Southern↗
PubMed1995

The gp 130 family cytokines IL-6, LIF and OSM but not IL-11 can reverse the anti-proliferative effect of dexamethasone on human myeloma cells.

In order to understand the mechanisms supporting steroid escape in patients with multiple myeloma (MM), three IL-6 autocrine human myeloma cell lines, LP1, OPM2 and L363, have been treated with dexamethasone in the presence or absence of cytokines belonging to the gp 130 family: IL-6, LIF, OSM and IL-11. With pharmacological doses of dexamethasone, a dramatic growth arrest was observed in all the cell lines. IL-6 completely reversed this inhibition. Of note, this IL-6 induced reversion was still seen with very low amounts of IL-6 (12 pg/ml). Finally, whereas LIF and OSM had clear growth-promoting effects on OPM2 only, both cytokines (but not IL-11) reversed the dexamethasone-induced growth arrest in all the cell lines. Therefore the high levels of IL-6 (ng/ml) observed in the MM intermediate milieu and the putative presence of LIF and OSM can easily counteract the effects of dexamethasone in vivo.

Antineoplastic Agents↗
PubMed1994

Expression of CD28 and CD40 in human myeloma cells: a comparative study with normal plasma cells.

CD28 and CD40 are important activation pathways for T and B lymphocytes, respectively. The aim of this study was to determine the phenotype of plasma cells (PCs) and the expression of these two molecules, CD28 and CD40. Therefore, we have compared their expression on normal PCs from bone marrows and tonsils with that of freshly explanted malignant PCs from 31 patients with multiple myeloma (MM) and those from 12 human myeloma cell lines. For this purpose, we first described a new approach to identify plasma cells in bone marrow using two-color immunofluorescence analysis with anti-CD38 and B-B4 antibodies. B-B4 specifically recognizes all PC; all B-B4 cells are located within the CD38 bright fraction and vice versa. CD19 and CD56 expression, which was previously shown to discriminate normal from malignant PCs, was also evaluated. In the current report, we show that normal PCs express CD19, CD40, and CD56 (weakly as a subset) and lack CD28. Regardless of whether they express CD19, CD56 is clearly upregulated during the medullary chronic and accelerated phases of MM, but is absent in patients with extramedullary involvement. Although the level of CD40 expression is variable, only patients in accelerated phases expressed high CD40 levels. Finally, whereas CD28 was negative in chronic phase (as in normal PCs), it was expressed in 63% of the patients in accelerated phases and 100% of cell lines. Our data strongly suggest that both disease activity and medullary homing (or not) are correlated with the expression of CD19, CD40, CD28, and CD56 on human myeloma cells.

Antibodies, Monoclonal↗
PubMed1994

A highly sensitive quantitative bioassay for human interleukin-11.

Human interleukin-11 (IL-11) is a cytokine with a broad spectrum of activity, similar to interleukin-6 (IL-6). However, its role in human disease is poorly understood, partly because of a lack of sensitive bioassays. A subclone (B9-11) obtained from the B9 hybridoma (which responds poorly to human IL-11) enabled us to develop a highly sensitive bioassay for human IL-11. B9-11 cells responded only to human IL-11 and IL-6 and not to other human cytokines using the same gp130 transducer chain (ciliary neurotrophic factor, leukemia inhibitory factor and oncostatin M) or to other human interleukins (interleukin-1 to interleukin-13), human hematopoietic cytokines (granulocyte colony stimulating factor, granulocyte-macrophage colony stimulating factor, colony stimulating factor-1) and various other human cytokines (interferon-alpha, tumor necrosis factor-alpha, tumor necrosis factor-beta, fibroblast growth factor and nerve growth factor). In addition, these cytokines did not interfere with the IL-11 response of B9-11 cells. IL-11-induced proliferation of B9-11 cells was unaffected by anti-murine IL-6 receptor mAb but inhibited by anti-gp130 mAb. Half-maximal proliferation of B9-11 cells was obtained with 30 pg/ml of recombinant IL-11, a concentration 300-fold lower than IL-11 concentrations known to be active on human cells. Finally, culturing of B9-11 cells with an anti-IL-6 mAb enabled us to measure the natural IL-11 produced by various cell lines. Thus, B9-11 cells should be useful for studies of IL-11 involvement in various human diseases as well as for a better understanding of the mechanisms of action of this cytokine.

Animals↗
PubMed1994

Insulin and interleukin-1 differentially regulate pp63, an acute phase phosphoprotein in hepatoma cell line.

We have reported previously that the phosphoprotein pp63, an acute phase protein, which has been recently identified as the rat fetuin, was capable of blocking the mitogenic effect of insulin on the rat Fao hepatoma cell line, without affecting metabolic effects of the hormone. Only the phosphorylated form of the protein has been shown to exhibit both anti-tyrosine kinase and growth inhibitory properties. In this study, we used the FTO-2B rat hepatoma cell line to analyze the mechanisms involved in the control of synthesis and/or phosphorylation of pp63. For this purpose, we investigated the action of effectors known to modulate hepatic functions, such as cytokines (interleukin (IL)-1 beta and IL-6), which regulate the production of acute phase proteins, and insulin, which elicits profound effects on hepatocyte metabolism. Here, we demonstrate that IL-1 beta diminished markedly the pp63 production by affecting its mRNA transcription and that the cytokine was able to modify the N-glycosylation process of the protein. In contrast, insulin did not affect the biosynthesis of pp63 but dramatically decreased its extent of phosphorylation.

Acute-Phase Proteins↗
PubMed1992

Sequence requirements for induction of cytolysis by the T cell antigen/Fc receptor zeta chain.

The zeta chain of the T cell antigen receptor is a dimeric transmembrane protein with a very short extracellular domain and an extended cytoplasmic tail that triggers T cell effector function when aggregated by extracellular stimuli. We have reduced the active site of zeta to an 18 residue motif that can be appended to the intracellular domain of other transmembrane proteins to endow them with receptor-like activity. The compact size of the motif appears to eliminate zeta mechanisms based on enzymatic activity and suggests that one or at most a few cellular proteins interact with the zeta intracellular domain to initiate signal transduction. Analysis of individual amino acids within the 18 residue element reveals two phylogenetically conserved tyrosines that are absolutely required for activity and other residues that are less essential but contribute to the efficacy of receptor-directed cytolysis.

Amino Acid Sequence↗