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Biomedical subjects

F André

Publications and source records attributed to F André.

At least 55 records · Page 3Linked to original sources
PubMed1999

Biogenesis of alpha6beta4 integrin in a human colonic adenocarcinoma cell line involvement of calnexin.

The heterodimer alpha6beta4 is a major integrin and the main laminin receptor in epithelia. The alpha6 integrin subunit is proteolytically cleaved, probably by furin, and glycosylated during its biosynthesis. In the present work, we have investigated the kinetics of the assembly process of alpha6beta4 heterodimers in the colonic adenocarcinoma cell line HT29-D4. We demonstrate that the association of alpha6 and beta4 precursors occurs within the ER, while the endoproteolytic cleavage of pro-alpha6 occurs later, probably in the trans-Golgi network. When pro-alpha6 was blocked within the ER by treatment with brefeldin A, its maturation processing was completely prevented without any consequence on its association with beta4 subunit. Low temperature (20 degrees C) also blocked pro-alpha6 maturation, like brefeldin A, but in addition impaired the integrin assembly. Calnexin, an ER resident protein chaperone, was found to be associated with both the alpha6 and beta4 subunit precursors. Our data suggest that calnexin might be responsible for the prolonged retention of pro-alpha6 within the ER compartment and for the defect of integrin subunit association observed at low temperature.

Adenocarcinoma↗
PubMed1999

Low-salt water reduces intestinal permeability in atopic patients.

BACKGROUND: Clinical remission of atopic dermatitis (AD) after intake of a low-salt water has recently been reported. METHODS: We here investigated the effects of a low-salt water in AD patients with increased intestinal permeability to lactulose. From an initial group of 75 atopic patients, who undertook a treatment in a medical spa center, 12 were included because of abnormal urinary excretion of lactulose (>0.6%), which is absorbed in the enterocytic interspaces, at baseline. The excretion of mannitol with an extraenterocytic absorption was also studied as control. During 18 days, the patients followed a medical spa treatment course, including topical application and oral ingestion of a low-mineral water. Patients were asked not to modify their usual food regimen during the cure. At the end of treatment (day 18), the determination of the excretion of both sugars in urine was repeated. RESULTS: At baseline, the mean urine excretion of lactulose in the study population was 1.21+/-0.08 SEM. At the end of treatment (day 18), the lactulose concentration in urine diminished dramatically by 55% (mean 0.55+/-0.09 SEM, p = 0.0005). Urine mannitol was also found to be reduced over the cure period, although to a lesser extent (30%, p = 0.04). CONCLUSION: This study indicates that low-mineral water normalizes the intestinal permeability of patients with AD.

Adolescent↗
PubMed1999

[Epidemiology, prognostic factors, staging, and treatment of non-small cell lung cancer].

Non small cell lung cancer (NSCLC) is the leading cause of cancer death among the world. The incidence of adenocarcinoma is rising while squamous cell carcinoma decreases. The biology of NSCLC is characterized by a multistep carcinogenesis. During the last years, changing in the management of NSCLC have occurred. The lobectomy and mediastinal lymph node dissection are now the references. Postoperative radiotherapy has failed to improve survival, but hyperfractionated radiotherapy seems to be interesting for inoperable patients. The platin-based chemotherapy is now considered as standard treatment for stage IV. Gene therapy and angiogenesis inhibitors are currently under development.

Carcinoma, Non-Small-Cell Lung↗
PubMed1998

"Rescue" abciximab for complicated percutaneous transluminal coronary angioplasty.

We studied the in-hospital outcome of 138 consecutive patients who received abciximab as a "rescue" intervention for complicated coronary angioplasty in a high-risk clinical setting. "Rescue" treatment with abciximab was associated with clinical and angiographic success rates of 83% and 84%, respectively, whereas the risk of bleeding was higher in patients of low body weight.

Abciximab↗
PubMed1998

Expression of the Cdx1 and Cdx2 homeotic genes leads to reduced malignancy in colon cancer-derived cells.

We have previously described an inverse relationship between Cdx1 and Cdx2 mRNA levels and the extent of dysplasia and severity of clinical outcome in colorectal carcinoma, suggesting that altered expression of these genes was associated with colorectal carcinogenesis or tumor progression. To investigate further their involvement in the physiopathology of colorectal cancer, HT29 colon carcinoma cells that show very low Cdx expression were transfected with Cdx1 and/or Cdx2 cDNA to elicit their overexpression. Growth rate, tumorigenicity, resistance to apoptosis, and migration potential of the corresponding cells were analyzed. Growth rate of cells overexpressing Cdx2 decreased by half, whereas overexpression of Cdx1 had no effect. However, cells overexpressing both Cdxs had a growth rate reduced to 20% of control. In cells overexpressing Cdx1 or Cdx2, tumorigenicity and resistance to apoptosis induced by serum starvation, ceramide, or staurosporine were not changed compared with control cells; yet phorbol ester-stimulated cell migration was decreased by 50%. In cells overexpressing both Cdx1 and Cdx2, tumorigenicity was decreased by 50%, resistance to apoptosis was significantly lowered, and stimulated cell migration was further decreased to 15% of control compared with cells expressing Cdx1 or Cdx2. Finally, cells overexpressing both Cdxs showed strongly decreased Bcl-2 expression, which could account for their increased sensitivity to apoptosis. These findings show that, in HT29 cells, both Cdx1 and Cdx2 genes must be expressed to reduce tumorigenic potential, to increase sensitivity to apoptosis, and to reduce cell migration, suggesting that the two genes control the normal phenotype by independent pathways. This may explain why loss of Cdx1 or Cdx2 expression is associated with tumor development and invasiveness in colorectal tumors.

Apoptosis↗
PubMed1998

Interrelation between high and low affinity tentoxin binding sites in chloroplast F1-ATPase revealed by synthetic analogues.

Eight synthetic analogues of tentoxin (cyclo-(L-N-MeGlu1-L-Leu2-N-MeDeltaZPhe3-Gly4)) modified in residues 1, 2, and 3 were checked for their ability to inhibit and reactivate the ATPase activity of the activated soluble part of chloroplast ATP synthase. The data were consistent with a model involving two binding sites of different affinities for the toxins. The occupancy of the high affinity site (or tight site) gave rise to an inactive complex, whereas filling both sites (tight + loose) gave rise to a complex of variable activity, dependent on the toxin analogue. Competition experiments between tentoxin and nonreactivating analogues allowed discrimination between the absence of binding and a nonproductive binding to the site of lower affinity (or loose site). The affinity for the loose site was not affected significantly by the modifications of the tentoxin molecule, whereas the affinity for the tight site was found notably changed. Increasing the size of side chain 1 or 2 and introducing a net electrical charge both resulted in a decrease of affinity for the tight site, but the second change dominated the first one. The activity of different ternary complexes enzyme-tentoxin-analogue depended on the nature of the toxin bound on each site and not only on that bound on the loose site. This demonstrates that the reactivation process results from an interaction, direct or not, between these two binding sites. Possible molecular mechanisms are discussed.

Binding Sites↗
PubMed1998

Determination of the exogenous character of testosterone in bovine urine by gas chromatography-combustion-isotope ratio mass spectrometry.

A new approach was developed in order to control testosterone abuse in animal production. A gas chromatographic-combustion-isotope ratio mass spectrometric (GC-C-IRMS) method was used to distinguish the exogenous character from the endogenous character of the main metabolites of testosterone (epitestosterone and etiocholanolone) in cattle urine. This method is based on a comparison between the carbon isotope ratio (13C/12C) of testosterone metabolites and those of testosterone endogenous precursors. After urinary steroid purification, extracts were acetylated with acetic anhydride and injected into the GC-C-IRMS system. In order to validate the method, testosterone enanthate was administered to a 4 year old cow. The 13C/12C isotope ratios of testosterone exogenous metabolites appeared to be significantly different to the 13C/12C precursor ratios and were detected until 3 weeks after the anabolic administration. These preliminary results appear to be promising for the difficult control of natural hormones in livestock.

Anabolic Agents↗
PubMed1998

Calf primary hepatocyte culture as a tool for anabolic steroid metabolism studies.

Calf hepatocyte cultures were developed for the predictive analysis of in vivo xenobiotic biotransformations. The goal of this work was to show the feasibility of a system based on calf primary hepatocyte cultures using radiolabelled molecules to study xenobiotic metabolism rather than to study exhaustively the metabolism of a particular steroid. 19-Nortestosterone was chosen as a model substrate because of its relatively well known metabolism in the bovine species. Incubation of a mixture of tritiated and non-tritiated 19-nortestosterone was investigated in cell culture in order to target the biosynthesized metabolites. After extraction and purification, some of the in vitro metabolite structures were elucidated by GC-MS and compared with the main urinary metabolites detected in vivo after intramuscular injection of 19-nortestosterone into a calf. 19-Norepitestosterone, the main in vivo metabolite, was identified in vitro. However, the main in vitro metabolites were mostly in an oxidized form (4-estrene-3,17-dione, hydroxy-4-estrene-3,17-dione).

Anabolic Agents↗
PubMed1998

Characterization of two monoclonal antibodies against the RON tyrosine kinase receptor.

RON is a receptor protein tyrosine kinase belonging to the hepatocyte growth factor (HGF) receptor family. Using Récepteur d'Origine Nantais (RON) transfected cell lines, Macrophage Stimulating Protein (MSP) was identified as the ligand of RON. RON is synthesized as a single chain precursor, which subsequently is cleaved to yield a disulfide-linked heterodimer, with a 40-kDa alpha chain and a 150-kDa beta chain. Activation of RON by MSP results in cell migration, shape change, and proliferation. The present work centers on the production and characterization of two monoclonal antibodies (MAbs) to RON called ID-1 and ID-2. Antibodies were generated by immunization of mice with Madin-Darby Canine Kidney (MDCK) cells expressing human RON (clone RE7). Both antibodies recognized the mature and precursor form of RON. The specificity of the anti-RON antibodies was confirmed using a hepatocarcinoma cell line HepG2 expressing both task MET and RON receptors. Specific immunoprecipitation with ID-1 and ID-2 or anti-MET antibody followed by Western blotting under reducing conditions with rabbit polyclonal antibodies against RON and MET showed that our anti-RON antibodies recognize specifically the RON receptor. Ligand binding experiments showed that both antibodies are able to block the binding of radiolabeled MSP to RON and showed also that the antibodies recognize two different epitopes in the molecule. The blocking of MSP binding to RON by the anti-RON antibodies was confirmed by inhibition of cell migration induced by MSP in HT-29-D4 cells. Significant immunostaining was not observed in any subpopulation of whole blood with either ID-1 or ID-2. We analyzed the expression of RON receptor in a number of human hematopoietic and nonhematopoietic cells lines by flow cytometry. We found a strong mean of fluorescence intensity (MFI) in colon adenocarcinoma cells SW620 and HT-29-D4, low MFI in SVK14 and HepG2 cells, and no immunostaining in melanoma, lymphoma, and leukemia cells. Immunohistochemistry revealed that RON was expressed in germinal centers of tonsil, in skin, small intestine, and colon. These antibodies defined RON as CDw136 during the last leucocyte typing VI.

Animals↗
PubMed1998

Oral food challenge increases in vitro IL-4 production by peripheral blood mononuclear cells in allergic patients.

The aim of this study was to investigate interferon-gamma (IFN-gamma) and interleukin-4 (IL-4) production by peripheral blood mononuclear cells (PBMC) in response to oral challenge in patients with food allergy. Thirty-one patients were compared with 10 healthy subjects. Cell cultures were prepared before and 150 min after single-blind, placebo-controlled, oral food challenge. In vitro production of cytokines was observed after stimulation with phytohemagglutinin (PHA) plus phorbol myristate acetate (PMA). Patients were characterized according to their reactions. In vitro IL-4 production was significantly greater in patients with food sensitization than in controls. The 18 patients with positive food challenge presented significantly greater IL-4 production after food challenge than before. IFN-gamma production was not modified. In the 10 control subjects and in 13 patients with negative food challenge, IL-4 and IFN-gamma production was comparable before and after food challenge. The increased IL-4 production in patients with positive oral food challenge could account for the development of polysensitization. This situation might be relevant to other allergic diseases and to treatments.

Adolescent↗
PubMed1998

Ewing's family of tumors in adults: multivariate analysis of survival and long-term results of multimodality therapy in 182 patients.

PURPOSE: To assess the outcome and the prognosis of adults with a neoplasm related to the Ewing's sarcoma family of tumors. PATIENTS AND METHODS: The outcomes of 182 consecutive patients older than 15 years with Ewing's sarcoma or related neoplasms managed from 1982 to 1992 were reviewed, without any selection according to primary tumor site or disease extension. RESULTS: Of 182 patients, 53 had evidence of metastases at presentation (29%). Tumor size was greater than 10 cm in 70 patients (41%). With a median follow-up duration of 66 months, the 5-year overall survival (OS) rate was 41%. In patients with localized disease, 5-year OS rate was 54% and 5-year progression-free survival (PFS) rate, 43%. Late relapses after 5 years accounted for 9% of relapses. Metastasis at presentation (P = .00001), pelvic primary lesion (P = .0025), and tumor size greater than 10 cm (P = .004) were independent prognostic factors for survival. Five-year OS was 67% in patients with nonpelvic tumors < or = 10 cm, 52% in those with pelvic tumors less than 10 cm or extrapelvic tumors > or = 10 cm, 16% in those with pelvic tumors greater than 10 cm, and 9% in those with metastasis (P = .00001). CONCLUSION: Based on our experience and a review of the literature, we concluded that the natural history and the prognosis of the Ewing's family of tumors in adults are not different from that found in children. A greater tumor bulk in adults may explain the less favorable prognosis previously reported by others. Outcome could be adequately monitored by a simple prognostic index.

Adolescent↗
PubMed1998

Deficient processing and activity of type I insulin-like growth factor receptor in the furin-deficient LoVo-C5 cells.

To investigate endoproteolytic processing of the type I insulin-like growth factor receptor (IGF-IR), we have examined its structure and activity in the furin-deficient LoVo-C5 cell line. Immunoprecipitation experiments using the monoclonal anti-IGF-IR antibody (alpha-IR3) showed that LoVo-C5 cells expressed a major high molecular mass receptor (200 kDa) corresponding to the unprocessed alpha/beta pro-receptor. A small amount of successfully cleaved alpha/beta heterodimers was also produced, indicating a residual endoproteolytic cleavage activity in these cells. In vitro, a soluble form of recombinant furin was able to cleave the pro-IGF-IR (200 kDa) into alpha-subunit (130 kDa) and beta-subunit (97 kDa). Measurement of IGF binding parameters in LoVo-C5 cells indicated a low number of typical type I IGF-binding sites (binding capacity, 5 x 10(3) sites/cell; Kd, 1.9 nM for IGF-I and 7.0 nM for IGF-II). These findings in LoVo-C5 contrast with those in HT29-D4 cells, which have active furin, and where IGF-IR (2.8 x 10(4) sites/cell) was fully processed. Moreover, the 200-kDa pro-IGF-IR of LoVo-C5 was unable to induce intracellular signaling, such as beta-subunit tyrosine autophosphorylation and insulin-related substrate-1 tyrosine phosphorylation. Flow immunocytometry analysis using alpha-IR3 antibody indicated that LoVo-C5 cells expressed 40% more receptors than HT29-D4 cells, suggesting that in LoVo-C5 cells only the small amount of mature type I IGF-IR binds IGFs with high affinity. To provide evidence for this idea, we showed that mild trypsin treatment of living LoVo-C5 cells partially restored alpha/beta cleavage of IGF-IR, and greatly enhanced (6-fold) the IGF-I binding capacity of LoVo-C5 cells, but did not restore IGF-IR signaling activity. Moreover, LoVo-C5 cells were totally unresponsive to IGF-I in terms of cell migration, in contrast to fully processed IGF-IR-HT29-D4 cells. Our data indicate that furin is involved in the endoproteolytic processing of the IGF-IR and suggest that this posttranslational event might be crucial for its ligand binding and signaling activities. However, our data do not exclude that other proprotein convertases could participate to IGF-IR maturation.

ADP Ribose Transferases↗
PubMed1998

Integrin ligation and PKC activation are required for migration of colon carcinoma cells.

The activation of protein kinases C (PKCs) is an essential step in integrin-dependent cell adhesion and spreading. In this report we examined the effect of the phorbol ester PMA, a PKC activator, on adhesion, spreading and migration of a colon carcinoma cell line, HT29-D4. Treatment with PMA increased the rate of cell spreading and induced the migration of these cells towards purified matrix proteins in haptotaxis assays on Boyden chambers. PMA-induced effects were the result of PKCs activation, as shown by using the inactive isomer 4alpha-PMA and PKCs inhibitors. The involvement of integrins in the phorbol ester-induced cell migration was demonstrated both by the absence of migration of cells plated on membranes coated with poly-L-lysine and by the use of function blocking antibodies. Thus, interactions between alpha 2beta1, alpha3beta1, alpha6beta4, alpha vbeta5, alphavbeta6 integrins and their specific ligands are necessary for the PKC-mediated migration. However, adhesion, immunoprecipitation and immunocytofluorometry experiments clearly showed that HT29-D4 cell haptotaxis induced by PKC activation is not a consequence of quantitative or qualitative changes in the cell surface integrins. We also demonstrated that PKCs were able to activate the MAP kinase pathway and that the impediment of MAP kinase activation resulted in the loss of cell migration. Moreover, stimulation of the insulin-like growth factor I signalling pathway led to MAP kinase activation and to the induction of cell migration. In addition, the growth factor-induced motility of HT29-D4 cells was affected both by PKC and MAP kinase cascade inhibitors. It thus appears that both integrin ligation and MAP kinase activation by PKCs are required to promote the migration of HT29-D4 cells.

Calcium-Calmodulin-Dependent Protein Kinases↗
PubMed1998

[Urothelial tumors of the bladder].

Bladder cancer is a common malignancy and accounts for 8,000 new cases and 4,000 deaths each year in France. Numerous factors may be responsible for the development of this disease, first of which are smoking and occupational exposure to chemicals. Main data regarding etiology, epidemiology and biology of bladder cancer are detailed. Diagnostic and therapeutic advances as well as actual research directions are presented.

Humans↗
PubMed1998

Follicle-like structure and polarized monolayer: role of the extracellular matrix on thyroid cell organization in primary culture.

The thyroid follicle, the morphofunctional unit of thyroid gland, is a spheroidal structure formed by a monolayer of polarized cells surrounding a closed cavity in which thyroglobulin accumulates. Newly isolated porcine thyroid cells reorganize into two types of structures which differ by the orientation of cell polarity: in follicle-like structures, obtained in the presence of TSH, the apical pole delineates a closed cavity and cells express most parameters characteristic of thyroid function; in inside-out follicles the apical pole is oriented towards the culture medium and cells do not express properly the thyroid function. The organization of newly formed follicles can be modified by stimulation of cell migration or by interaction of their apical poles with a new cell environment. Seeded on a hard surface (glass, plastic), cells of follicle-like structures or inside-out follicles formed in suspension migrate giving a monolayer. On the contrary, cells organized into a monolayer treated with hexamethylene bisacetamide, reorganize into follicle-like structures. Inside-out structures reorganize upon interaction of their apical poles with collagen I gel, a coherent matrix, or with a reconstituted basement membrane (RBM), a soft matrix. Overlaid with collagen I, monolayers reorganize into follicles. Embedded in collagen I or in RBM, inside-out follicles reorient their polarity giving functional follicles. On the RBM surface, cells pull on the gel and embed themselves in the soft matrix gel, finally reorienting their polarity to inside-in polarity. When comparing thyroid cells with other epithelial cell types (mammary cells, Sertoli cells), it appears that the obtention in culture of follicle-like structures, i.e. closed inside-in polarized cell organization, is the best way to express in culture both morphology and function of any specific epithelial tissue, the polarized monolayer in porous bottom culture chamber coming just behind.

Acetamides↗