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Biomedical subjects

S Ménard

Publications and source records attributed to S Ménard.

At least 55 records · Page 3Linked to original sources
PubMed2000

Detection of aberrant isotype switch recombination in low-grade and high-grade gastric MALT lymphomas.

Gastric mucosa-associated lymphoid tissue (MALT) lymphoma originates from reactive lymphocytic infiltrates during chronic gastritis, closely associated with Helicobacter pylori infection. MALT lymphomas may be either "low grade" or "high grade," and transformation from low grade to high grade can occur. To obtain information on the maturational state of MALT lymphoma cells, we investigated their ability to undergo isotype switch recombination, which together with immunoglobulin variable gene somatic mutation, contributes to normal B-cell maturation. Using specific probes for the immunoglobulin heavy-chain (IgH) switch regions, we found by Southern blot that 3 out of 5 low-grade cases and 2 out of 2 high-grade cases showed rearrangements within IgH switch regions, which appeared aberrant in 4 of the 5 cases. The cloning of two rearranged fragments from one low-grade and one high-grade case confirmed the aberrant nature of the rearranged fragments. A deletion from the switch mu region (S mu) to the first constant mu exon (C mu 1) and a second deletion from the second constant mu exon (C mu 2) to the gamma 3 region (gamma 3) was detected in the low-grade case. In the high-grade case, there was a deletion of the IgH intronic enhancer (E mu) and a 336-base pair (bp) insertion into the S mu region of a gene (KIAA0307) normally located at 15q24. These data demonstrate for the first time the ability of MALT lymphoma cells to undergo aberrant isotype switch recombinations, which might be directly involved in the development or progression of malignancy.

B-Lymphocytes↗
PubMed2000

Tamoxifen chemoprevention of a hormone-independent tumor in the proto-neu transgenic mice model.

We evaluated the effect of tamoxifen (TAM) on tumor development in proto-neu transgenic mice that spontaneously develop mammary carcinomas overexpressing the neu protein. These mammary carcinomas are hormone independent because superimposable growth of transplants was observed in females and males. Virgin transgenic mice treated with TAM from 24 weeks of age, ie., when subclinical mammary tumors are already present, showed a slightly accelerated tumor development. In contrast, transgenic mice treated with TAM starting at 12 weeks of age, when subclinical tumors are not yet present, showed a 50% reduction of tumor incidence. Light microscopy analysis of the mammary gland of these mice revealed an apparently normal ductal branching but a complete regression of the acini. In conclusion, TAM can prevent the occurrence of hormone-independent breast carcinoma if given early enough to inhibit normal cells.

Animals↗
PubMed2000

Role of HER2 gene overexpression in breast carcinoma.

The HER2 proto-oncogene encodes a transmembrane glycoprotein of 185 kDa (p185(HER2)) with intrinsic tyrosine kinase activity. Amplification of the HER2 gene and overexpression of its product induce cell transformation. Numerous studies have demonstrated the prognostic relevance of p185(HER2), which is overexpressed in 10% to 40% of human breast tumors. Recent data suggest that p185(HER2) is a ligand orphan receptor that amplifies the signal provided by other receptors of the HER family by heterodimerizing with them. Ligand-dependent activation of HER1, HER3, and HER4 by EGF or heregulin results in heterodimerization and, thereby, HER2 activation. HER2 overexpression is associated with breast cancer patient responsiveness to doxorubicin, to cyclophosphamide, methotrexate, and fluorouracil (CMF), and to paclitaxel, whereas tamoxifen was found to be ineffective and even detrimental in patients with HER2-positive tumors. In vitro analyses have shown that the role of HER2 overexpression in determining the sensitivity of cancer cells to drugs is complex, and molecules involved in its signaling pathway are probably the actual protagonists of the sensitivity to drugs. The association of HER2 overexpression with human tumors, its extracellular accessibility, as well as its involvement in tumor aggressiveness are all factors that make this receptor an appropriate target for tumor-specific therapies. A number of approaches are being investigated as possible therapeutic strategies that target HER2: (1) growth inhibitory antibodies, which can be used alone or in combination with standard chemotherapeutics; (2) tyrosine kinase inhibitors (TKI), which have been developed in an effort to block receptor activity because phosphorylation is the key event leading to activation and initiation of the signaling pathway; and (3) active immunotherapy, because the HER2 oncoprotein is immunogenic in some breast carcinoma patients.

Breast Neoplasms↗
PubMed2000

Modulation of interleukin-12 synthesis by DNA lacking the CpG motif and present in a mycobacterial cell wall complex.

A mycobacterial cell wall complex prepared from the non-pathogenic microorganism Mycobacterium phlei, where mycobacterial DNA is preserved and complexed to cell wall fragments, possesses anticancer and immunomodulatory activity. DNA from a number of prokaryotes has been found to modulate the immune system and to induce cytokine synthesis. We have therefore determined whether the DNA associated with this complex has the ability to induce the synthesis of interleukin-12 (IL-12), a potent anticancer cytokine. Mycobacterial DNA complexed with cell wall fragments or DNA purified from M. phlei induced IL-12 synthesis by murine and human monocytes and macrophages in vitro, and was capable of inducing IL-12 synthesis in vivo in mice following i.p. administration. Neutralization of DNA with cationic liposomes or digestion with DNase I significantly decreased the ability of the cell wall complex to induce IL-12. CpG methylation of DNA extracted from these cell walls or from M. phlei did not affect the induction of IL-12 synthesis by monocytes and macrophages. In contrast, CpG methylation of DNA from Escherichia coli abolished its ability to induce IL-12 synthesis. These results demonstrate that unmethylated CpG motifs present in M. phlei DNA are not a prerequisite for the induction of IL-12 synthesis. The size of the mycobacterial DNA, in the range of 5 bp to genomic DNA, did not influence its capacity to induce IL-12. Our results emphasize that M. phlei DNA associated with the cell wall complex makes a significant contribution to the overall immunomodulatory and anticancer activity of this mycobacterial cell wall preparation and that these activities are not correlated with the presence of CpG motifs.

Animals↗
PubMed1999

High level antibody response to retrovirus-associated but not to melanocyte lineage-specific antigens in mice protected against B16 melanoma.

Mice vaccinated with Mycobacterium tuberculosis Ag38 gene-transduced B16 melanoma cells showed significant protection from intravenous challenge with parental B16 melanoma cells. No cytotoxic T-cell activity was found against melanoma cells, although the endogenous presence of the mycobacterial gene induced a preferential Th1 response. After immunization, a low serological response against melanoma cells was detected, while a high titer of antibodies directed to parental B16 cells, mainly of IgG2(a) isotype, was found in protected mice after challenge. These antibodies exhibited complement-dependent cytotoxicity against melanoma cells in vitro, while in vivo, used in passive immunization, they induced a decrease in a number of experimental B16 lung metastases. Most of the antibodies were directed against endogenous murine leukemia viruses. No reactivity against melanocyte lineage-specific antigens was observed. In particular, no reactivity was found in sera from protected mice against tyrosinase-related protein 2 (TRP-2), either stably expressed in a non-melanoma cell line or obtained by in vitro transcription-translation, or against tyrosinase, TRP-1 and gp100 antigens immunoprecipitated from B16 cells. Thus, in the B16 murine model, the presence of dominant viral antigens induces a very strong humoral response that might be protective and may inhibit or mask the presence of minor clonotypes.

3T3 Cells↗
PubMed1999

Concomitant activation of pathways downstream of Grb2 and PI 3-kinase is required for MET-mediated metastasis.

The Met tyrosine kinase - the HGF receptor - induces cell transformation and metastasis when constitutively activated. Met signaling is mediated by phosphorylation of two carboxy-terminal tyrosines which act as docking sites for a number of SH2-containing molecules. These include Grb2 and p85 which couple the receptor, respectively, with Ras and PI 3-kinase. We previously showed that a Met mutant designed to obtain preferential coupling with Grb2 (Met2xGrb2) is permissive for motility, increases transformation, but - surprisingly - is impaired in causing invasion and metastasis. In this work we used Met mutants optimized for binding either p85 alone (Met2xPI3K) or p85 and Grb2 (MetPI3K/Grb2) to evaluate the relative importance of Ras and PI 3-kinase as downstream effectors of Met. Met2xPI3K was competent in eliciting motility, but not transformation, invasion, or metastasis. Conversely, MetP13K/Grb2 induced motility, transformation, invasion and metastasis as efficiently as wild type Met. Furthermore, the expression of constitutively active PI 3-kinase in cells transformed by the Met2xGrb2 mutant, fully rescued their ability to invade and metastasize. These data point to a central role for PI 3-kinase in Met-mediated invasiveness, and indicate that simultaneous activation of Ras and PI 3-kinase is required to unleash the Met metastatic potential.

Adaptor Proteins, Signal Transducing↗
PubMed1999

Ectopic expression of pRb2/p130 suppresses the tumorigenicity of the c-erbB-2-overexpressing SKOV3 tumor cell line.

We investigated the in vitro and in vivo effects of the ectopic expression of the pRb2/p130 cell cycle regulator on c-erbB-2-associated tumorigenicity. SKOV3 ovarian cancer cells, which display c-erbB-2 gene amplification and oncoprotein (p185HER2) overexpression, were stably transfected with a plasmid containing the coding sequence for human wild-type pRb2/p130 (wtRb2), or with pcDNA3 empty vector. Three wtRb2-transfected clones (cl. 24, ci. 49, cl. 100) and one empty vector-transfected clone (cl. mock) were randomly picked and further analysed. Western blot analysis revealed high levels of pRb2/p130 in the three clones compared to mock cells. Levels of p185HER2 and the extent of its tyrosine phosphorylation were similar in all transfectant clones, as were levels of pRb1 and p107. In anchorage-independent growth assays, the number of colonies from wtRb2 clone-transfectants was about 90% less than that arising from mock cells (P<0.001). Tumor take rates of the three wtRb2-transfected clones xenografted in nu/nu mice were much lower than those of mock cells, and tumor volume was decreased by 80% (P<0.001). A mutant version of pRb2/p130 deleted of the pocket region (mut-Rb2) was also transfected into SKOV3 cells and studied in parallel with the wtRb2-transfected and pcDNA empty vector-transfected bulk populations. mut-Rb2 transfected cells showed no inhibition of in vitro colony formation and were fully tumorigenic. Together, these findings indicate that Rb2 acts as a tumor suppressor gene in vivo and in vitro in SKOV3 cells and that the intact pocket region is required for the suppressor activity.

Animals↗
PubMed1999

Absence of microsatellite instability in breast carcinomas with both p53 and c-erbB-2 alterations.

Based on a previous finding that amplification of the c-erbB-2 oncogene and alteration of p53 are strongly associated in most aggressive breast tumours, the present study investigated whether microsatellite instability (MI) might also be associated with this tumour phenotype. Nine polymorphic microsatellite markers, including six dinucleotide, one trinucleotide, and two tetranucleotide repeats, were amplified from paired normal and tumour DNA samples of 15 breast tumours that overexpressed both c-erbB-2 and p53 and of 15 control breast tumours that overexpressed neither protein. All 30 breast tumours analysed exhibited a replication error-negative phenotype, with only one sample showing MI in one of the nine loci. This suggests that the genetic events underlying MI, which are critical in colorectal and gastric tumours, are not involved in the pathogenesis of c-erbB-2/p53 double-altered breast tumours and do not play a central role in breast tumour formation.

Adult↗
PubMed1999

Fluctuation of HER2 expression in breast carcinomas during the menstrual cycle.

The hormonal milieu at time of tumor surgery seems to have a significant impact on survival in premenopausal breast cancer patients. Indeed, surgery performed during the follicular phase of the menstrual cycle was suggested to correlate with a poor prognosis. To investigate the relationship between prognosis and menstrual cycle at time of surgery, we analyzed the expression of some markers associated with tumor aggressiveness, such as the hormone receptors, HER2, p53, Bcl2, and cathepsin D in breast carcinomas obtained from 198 premenopausal women who underwent surgery during different phases of the menstrual cycle. HER2 overexpression was found to fluctuate in hormone receptor-positive tumors. In actual fact, 20% of the tumors removed during the follicular phase scored HER2-positive, versus 8% of those removed during the luteal phase. Similarly, a number of hormone receptor-positive tumor specimens, obtained from the same patients during follicular and luteal phases, were scored HER2-positive when the sample was removed during the follicular phase and HER2-negative when removed in the luteal phase. Southern blot analysis of the HER2 gene indicated that, in hormone receptor-positive cases, the overexpression of HER2 is often not associated with gene amplification. The finding that overexpression of the HER2 gene, associated with tumor aggressiveness, can fluctuate according to the hormonal milieu may explain the increased survival of patients operated during the luteal phase. It is also relevant to the selection and treatment of patients most likely to benefit from anti-HER2 antibody therapy.

Adult↗
PubMed1999

Pathobiologic identification of two distinct breast carcinoma subsets with diverging clinical behaviors.

Many different pathological and biological variables which characterize breast carcinomas have been found to be associated. The aim of this work was to analyze the complex relationship among these parameters. The pathologic, biologic, and clinical characteristics of a series of primary breast carcinomas from 676 patients were retrospectively investigated. Multiple correspondence analysis of 13 factors revealed clustering of eight pathobiologic variables, that is histologic grade, necrosis, lymphoid infiltration, number of mitoses, c-erbB-2 overexpression, p53, progesterone receptor, and bcl2 expression. An index for each tumor calculated on the basis of these eight factors served to distinguish two different tumor phenotypes, designated A and B. Phenotype A is represented by tumors sharing most of the biologic features of normal breast tissues: indeed, these tumors are characterized by a relatively high degree of differentiation, low proliferation, no necrosis or leukocyte infiltration, and no gene alterations. By contrast, phenotype B is quite divergent from the normal tissue because of its poor differentiation, high proliferation, frequent gene alterations and evidence of a host immune reaction. As regards the disease progression, these two subsets showed marked differences: phenotype A tumors had a low recurrence rate per year that remained constant over time and affected more frequently elderly patients, whereas group B tumors showed high aggressivity in the first years after surgery followed by a low long-term recurrence rate and were more frequently seen in younger patients. These data suggest that breast carcinoma consists of two different subsets that can be identified on the basis of pathobiologic features.

Adult↗
PubMed1999

Correlation between tumor vascularity, vascular endothelial growth factor production by tumor cells, serum vascular endothelial growth factor levels, and serum angiogenic activity in patients with breast carcinoma.

Angiogenesis is an important prognostic factor in invasive breast carcinoma. We analyzed sera and tumor samples from 36 patients with primary breast carcinomas to determine the relationship between tumor vascularity, vascular endothelial growth factor (VEGF) production by tumor cells, levels of circulating VEGF (measured by ELISA assay), and levels of endothelial growth factors analyzed by a functional test of human umbilical vein endothelial cells (HUVEC) proliferation. Tumor vascularity was correlated directly with VEGF production by the tumor, indicating that VEGF production is a relevant factor in determining angiogenesis in primary tumor. No correlation was found either between the number of vessels in the tumor or the production of VEGF by tumor cells and the levels of serum angiogenic factors including VEGF. On the contrary, the two serum tests correlated together because a high serum level of VEGF is more frequent in cases with the presence of HUVEC-stimulating growth factors. These data indicate that the principal source of factors stimulating angiogenesis in the primary tumor is the tumor itself. This is an important issue in the context of anti-angiogenic therapeutic approaches, which should be planned to interfere with tumor production of angiogenic factors rather than with circulating angiogenic factors. In conclusion, whereas the vessel count and VEGF production by tumor cells are parameters that give direct information on tumor angiogenesis, long-term follow-up is necessary to determine the clinical significance of the determination of serum HUVEC-stimulating factors in the progression of breast carcinoma.

Breast Neoplasms↗
PubMed1999

Sequences homologous to the mouse mammary tumor virus env gene in human breast carcinoma correlate with overexpression of laminin receptor.

We previously reported that a 660-bp sequence that is homologous to the env gene of the mouse mammary tumor virus (MMTV) but not to endogenous retroviruses or to other known genes was present in 38% of human breast cancers and in some breast cancer cell lines studied (Y. Wang et al., Cancer Res., 55: 5173-5179, 1995). Here, we have investigated whether the MMTV-like sequences were associated with the clinical, pathological, and molecular parameters that have been reported to define two subsets of human breast cancers. Archival breast carcinoma samples were analyzed for four clinical parameters, obtained from patients' records, and for six pathological characteristics. Expression of c-erbB-2, p53, bcl-2, progesterone receptor, laminin receptor, and cathepsin D was detected by immunochemistry using monoclonal antibodies. PCRs were used to amplify 250 bp of the MMTV env gene-like sequence. The chi2, log-rank, and generalized Wilcoxon tests were used to analyze the data. The MMTV env gene-like sequence was detected in 37.7% of the samples. The presence of this sequence was not significantly associated with any of the pathological clinical or biological parameters studied. It did correlate, however, with expression of the laminin receptor, a marker for invasiveness and poor prognosis. This is the first phenotypic characterization of human breast cancers containing retroviral sequences.

Breast Neoplasms↗
PubMed1998

Increased expression of c-erbB-2 in hormone-dependent breast cancer cells inhibits cell growth and induces differentiation.

c-erbB-2, a member of the tyrosine kinase oncogene family, is overexpressed in about 30% of human breast tumors where it correlates with poor prognosis. In vitro studies have suggested that increased expression of the receptor plays an important role in malignant progression. To better understand the direct effects of p185HER2 overexpression, a human c-erbB-2 expression vector was transfected into the hormone-dependent MCF-7 human breast carcinoma cell line and cell growth was analysed. Unexpectedly, colony formation assay revealed a reduction in the number and size of colonies as compared with mock-transfected cells. In hormone-deprived medium, c-erbB-2 transfected cells acquired growth capability, consistent with previous reports. By contrast, two c-erbB-2-transfected clones grown in complete medium showed a reduced proliferation rate despite the activation of a fully functional oncoprotein capable of autophosphorylation and induction of the MAPK pathway. The number of c-erbB-2-overexpressing cells in the S phase of the cell cycle was about one-half the number of control and mock-transfected cells. Also, overexpression of c-erbB-2 induced overexpression of p21WAF1, pRB hypophosphorylation and a mature differentiated cell phenotype with production of lipid droplets. Functional inactivation of p185HER2 by means of a specific single chain antibody indicated the c-erbB-2-dependence of the observed alterations. These data show that the exogenous overexpression of the c-erbB-2 gene in hormone-dependent breast cancer cells inhibits proliferation and induces differentiation.

Adenocarcinoma↗
PubMed1998

Formation of the 67-kDa laminin receptor by acylation of the precursor.

Even though the involvement of the 67-kDa laminin receptor (67LR) in tumor invasiveness has been clearly demonstrated, its molecular structure remains an open problem, since only a full-length gene encoding a 37-kDa precursor protein (37LRP) has been isolated so far. A pool of recently obtained monoclonal antibodies directed against the recombinant 37LRP molecule was used to investigate the processing that leads to the formation of the 67-kDa molecule. In soluble extracts of A431 human carcinoma cells, these reagents recognize the precursor molecule as well as the mature 67LR and a 120-kDa molecule. The recovery of these proteins was found to be strikingly dependent upon the cell solubilization conditions: the 67LR is soluble in NP-40-lysis buffer whereas the 37LRP is NP-40-insoluble. Inhibition of 67LR formation by cerulenin indicates that acylation is involved in the processing of the receptor. It is likely a palmitoylation process, as indicated by sensitivity of NP-40-soluble extracts to hydroxylamine treatment. Immunoblotting assays performed with a polyclonal serum directed against galectin3 showed that both the 67- and the 120-kDa proteins carry galectin3 epitopes whereas the 37LRP does not. These data suggest that the 67LR is a heterodimer stabilized by strong intramolecular hydrophobic interactions, carried by fatty acids bound to the 37LRP and to a galectin3 cross-reacting molecule.

Acylation↗
PubMed1998

Heregulin beta1 induces the down regulation and the ubiquitin-proteasome degradation pathway of p185HER2 oncoprotein.

Analysis of the fate of the p185HER2 oncoprotein following activation by heregulin beta1 revealed the induction of the tyrosine-phosphorylation, down-modulation, and polyubiquitination of p185HER2. Receptor ubiquitination was suppressed in cells treated with heregulin beta1 in the presence of sodium azide, an inhibitor of ATP-dependent reactions, or genistein, a tyrosine kinase protein inhibitor, indicating the requirement for kinase activity and ATP in p185HER2 polyubiquitination. Ubiquitinated p185HER2 was degradated by the 26S proteasome proteolytic pathway. Kinetics and inhibition experiments indicated that endocytosis of the receptor occurs downstream of the initiation of the degradation process.

Adenosine Triphosphate↗