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K Meflah

Publications and source records attributed to K Meflah.

At least 19 recordsLinked to original sources
PubMed1992

Involvement of histo-blood-group antigens in the susceptibility of colon carcinoma cells to natural killer-mediated cytotoxicity.

The susceptibility to natural-killer-cell lysis and expression of histo-blood-group antigens of 2 clones from a rat colon adenocarcinoma, of variants derived from them and of 17 human colon carcinoma cell lines were assessed in an attempt to determine if the major glycosidic tissue antigens of epithelial cells could influence the NK susceptibility of tumor target cells of epithelial origin. The rat REGb clone, which is relatively NK-sensitive, expressed higher levels of precursor structures T and Tn and lower levels of H antigenic determinants than the PROb clone, which displays higher resistance to NK-cell lysis. Cell variants were obtained from these 2 clones; it appeared that whether the cell variants were selected on the basis of expression of a blood-group antigenic determinant or on the basis of altered susceptibility to NK-cell lysis, there was a link between increased resistance and higher expression of cell-surface A and H histo-blood-group antigens, or conversely, between increased sensitivity and higher expression of precursor structures. Similar conclusions were obtained upon study of the human cell lines, since a significant correlation was found between the level of expression of T or Tn antigens and sensitivity to NK-cell lysis. A significant relationship was found between the expression of Lewis antigens and increased resistance to NK-cell-mediated cytotoxicity.

ABO Blood-Group System↗
PubMed1992

Isolation of cDNA clones corresponding to genes differentially expressed in two colon-carcinoma cell lines differing by their tumorigenicity.

In an effort to isolate genes involved in the progression of colonic cells leading to a carcinoma, we used as a model 2 rat colon-carcinoma cell lines selected from the same tumor, differing by their tumorigenicity. When soluble, Triton-X-100 extracted, or cytoskeletal proteins from the progressive PROb cells and the regressive REGb cells were analyzed by SDS-PAGE, minor differences were seen. Furthermore, mRNA-cDNA hybridization analyses showed extensive homology between the 2 mRNA populations. Thus, the homology between the 2 clones is high at both the protein and the mRNA levels. A PROb cDNA library was hybridized with 32P-cDNA synthesized from PROb or REGb mRNA. The clones giving a stronger signal when hybridized with the homologous PROb probe were isolated. The specificity of each clone was confirmed by RNA blotting. Most of the positive clones showed a 2- to 3-fold higher expression in PROb cells when compared with REGb cells. One clone (J 13) corresponded to an mRNA 7- to 10-fold more abundant in PROb cells, and was further studied. No gene amplification was detected by Southern blot analysis, indicating that the difference in mRNA content was most likely due to an increased transcription of this gene in PROb cells. Sequencing of the cDNA showed high homology with the rat ferritin light sub-unit. Over-expression of ferritin in PROb cells as compared with REGb cells was confirmed at the protein level using specific antibodies.

Adenocarcinoma↗
PubMed1992

Relationship between sensitivity to natural killer cells and MHC class-I antigen expression in colon carcinoma cell lines.

The sensitivity of colorectal tumors to NK-cell-mediated cytotoxicity and their expression of major histocompatibility complex (MHC) class-I antigens were studied in an attempt to determine whether such antigens play a role in the susceptibility of colorectal tumors to NK-cell lysis. In a rat colon-carcinoma model, 2 clones differing in their sensitivity to NK-cell-mediated cytotoxicity were tested for class-I expression; it was seen that the more sensitive cells (REGb) expressed less class-I products than did the resistant cells (PROb). However, when MHC class-I antigen expression was increased by IFN-gamma treatment, no change in NK-cell lysis was found with the PROb cells, while an increase in cytotoxicity was obtained with the REGb cells. After in vivo or in vitro selection of NK-resistant REGb cells, we observed in the selected cells an important decrease in RT-I class-I antigen expression. Fifteen different human colorectal cell lines were also studied for HLA class-I expression and NK-cell susceptibility, and no quantitative correlation between these 2 features was seen. However, cell lines which were deficient in HLA class-I antigens were more sensitive than class-I-positive cells.

Animals↗
PubMed1992

Modulation of extracellular matrix glycoproteins production by in vitro interacting conditions between rat colonic fibroblasts and tumoral cells.

Mixed cultures of fibroblasts with rat colon carcinoma cell lines were used to investigate the production of extracellular matrix glycoproteins. Tumoral cells were shown to influence their production in different ways depending on the cell clone (PROb cells which in vivo produce progressive tumors and REGb cells which produce regressive ones) but also on the relative proportions of stromal and tumoral cells. When fibroblasts were predominant, the REGb cells containing mixture produced higher levels of all protein studied as compared with the PROb cells containing system. When the situation was reversed in favor of tumoral cells, REGb cells containing cocultures still produced more fibronectin, laminin and undulin, but the difference with PROb ones was reduced. On the opposite, cocultures enriched with PROb cells made more entactin and SPARC and approximately equal amounts of tenascin.

Animals↗
PubMed1992

Differential adhesion of rat colon carcinoma cells to fibronectin in relation to their tumorigenicity.

We examined the fibronectin-adhesive properties of clones from a rat colonic cell line exhibiting distinct tumorigenicity in a syngeneic host. These cells were originally selected on the basis of differential adhesion to plastic surfaces. The TR cell line, when injected subcutaneously, forms a tumour which grows progressively and gives off metastases, whereas the TS cell line forms a small tumour which regresses within a few weeks. The regression is largely mediated by immunological factors and involves a fibroblastic reaction. REGb, a clone from the TS subline, adhered better to fibronectin or RGDS tetrapeptide than did PROb, a clone from the TR subline. However, there was little binding to the RGD tripeptide with either clone. The degree of adhesion was dependent on time and substrate concentration. After 6 h of incubation, 38% and 55% respectively of PROb and REGb cells bound to plates coated with 10 micrograms/ml fibronectin. Adhesion of both clones to fibronectin was inhibited to various degrees when cells were preincubated with RGDS, GRGDS or GRADSPK peptides, whereas other synthetic peptides such as RGD, GRGD or GRGFSPK were ineffective. Binding experiments using 125I-labelled fibronectin showed 39,000 fibronectin receptor sites on REGb cells but only 17,000 on PROb cells. Flow cytometry analysis using both anti-alpha 5 and anti-beta 1 integrins showed more fibronectin receptor sites on REGb than on PROb cells. Both approaches were in accordance with the higher adhesiveness of the REGb clone to fibronectin.(ABSTRACT TRUNCATED AT 250 WORDS)

Adenocarcinoma↗
PubMed1992

Possible involvement of TGF beta 1 in the distinct tumorigenic properties of two rat colon carcinoma clones.

The presence in tumors of numerous cytokines suggests that they potentially modulate tumor cell activities and host tissue remodelling. To investigate the possible involvement of transforming growth factor type beta (TGF beta) in the metastatic process of cancer development, we have studied the effect of this factor on two rat colon carcinoma cell lines. These cell clones had been previously tested and selected for their ability to develop metastases in syngenic animals or lack of it. The two cell lines were characterized for their production of TGF beta. Production of active and latent forms of TGF beta 1 in the medium conditioned by the rat colon cancer cells were quantified using a bioassay. The presence of active TGF beta 1 was demonstrated in conditioned medium from the progressive tumor (PROb) cells and significant expression of latent forms of TGF beta 1 were found in the conditioned media from both cell clones. TGF beta 1 slightly inhibited proliferation of PROb cells which had been previously described as moderately differentiated, and significantly stimulated proliferation of the regressive (REGb) cells, described as poorly differentiated. On the basis of our observations, we suggest that this endogenous factor could be involved in autocrine regulation of tumor cell activities and in paracrine regulation of stroma cell and immune responses. Active and/or latent expression of TGF beta 1 by the two rat colon carcinoma cell lines, and their variable responses to the growth factor, strongly suggest that this polypeptide is involved in the regulation of tumorigenic expression of adenocarcinoma cells.

Adenocarcinoma↗
PubMed1992

[Characterization of autoantigen (p105) in a model of colonic adenocarcinoma in the rat].

Sera from BDIX rats bearing the syngeneic colon tumors PROb or REGb were analysed by Western blotting in order to detect a possible humoral response against the grafted tumor. The PROb clone grows progressively in syngeneic hosts and metastasizes, whereas the REGb clone grows slowly and then is rejected. This model was developed by F Martin and his group in Dijon, France. We observed that rats bearing PROb tumors only develop an antibody response against a water-soluble protein of 105 kDa (p105) which is expressed by both tumor clones. This antibody response has never been detected in rats bearing REGb tumors. The antigen p105 was also expressed by normal adult colon as well as some other foetal or adult tissues. It is also present in extracts from several tumor cell lines including human colorectal carcinoma cell lines. Moreover, the titer of detected antibody at day 30 was inversely correlated with the survival of rats after tumor inoculation, suggesting a possible facilitating role of this antibody response.

Adenocarcinoma↗
PubMed1991

Expression of alkaline phosphatase in murine lymphoma cells.

Alkaline phosphatase (ALP) was secreted and expressed at the cell surface of the lymphoma A/63-2 cell line but not on another clone A/63-1 deriving from a single thymoma (A/63) induced by a wild-type Abelson-Moloney viral complex. The enzyme was heat-sensitive and strongly inhibited by L-p-bromotetramisole and L-homoarginine but not by L-phenylalanine. All these data indicated that this enzyme was most likely identical to the L/B/K ALP isoenzyme. Southern blot analysis showed that neither amplification nor polymorphism were responsible for the high expression of the ALP gene observed in A/63-2 cells. On the opposite, the mRNA transcripts of ALP were only detected in A/63-2 cells indicating that a modulation of the ALP gene transcription occurred which could be due to the insertion of the v-abl gene within or near the 5'-flanking region of the ALP promotor in A/63-2 cells. Butyrate strongly increased both the secretion and the expression of the enzyme on A/63-2 cell surface. This induction was strongly inhibited by cordycepin, an RNA biosynthesis inhibitor, and at a lesser degree by cycloheximide, a translation inhibitor suggesting that butyrate induction occurs both at the transcriptional and the translational level.

Alkaline Phosphatase↗
PubMed1991

Characterization, isolation and amino terminal sequencing of a rat colon carcinoma-associated antigen.

Monoclonal antibodies have been raised against a cell line derived from a dimethylhydrazine-induced rat colon carcinoma. One of these antibodies (MAb E4) has previously been shown to react slightly with normal small intestine and colon, and not with other normal tissues as determined by immunohistochemistry. Using Western immunoblotting we confirmed this tumor specificity. Therefore, the Mr of approx. 66,000 glycosylated antigen (pE4) recognized by MAb E4 appeared to be a potential marker of colon carcinoma. Fifteen human tumor cell lines were tested by flow cytometry for the expression of pE4. This antigen was not detected on these cells. In the rat colon carcinoma cell, pE4 was exclusively found on the cell membrane. pE4 was purified to near homogeneity by immunoaffinity chromatography. The first 20 N-terminal amino acids were identified. Comparison with the NBRF data bank did not reveal a complete homology with known sequenced proteins but similarities were found with the mouse L3T4 precursor, the env polyprotein of human immunodeficiency virus type I, flagellin from Halobacterium halobium and the gp30 from hepatitis B surface antigen. Homology was always found in transmembranous or hydrophobic domains of these proteins. By indirect immunofluorescence analysis of adherent cells and size exclusion chromatography under native conditions, pE4 was found to interact with other molecules and perhaps to be involved in intercellular contact.

Amino Acid Sequence↗
PubMed1991

Analysis of the state of differentiation of two rat colon carcinoma clones with distinct tumorigenic properties.

The presence of some characteristics of normal rat intestinal epithelial cells was studied on two clones originating from a single rat colon carcinoma. These clones differed by their tumorigenic properties in the syngeneic host. However, they grow similarly in vitro and in immuno-deprived animals. The PROb clone which had the ability to form progressive tumors in the syngeneic host appeared to possess more features of differentiated cells than the REGb clone which was immunologically rejected by syngeneic hosts. Indeed, the morphology of the cells was different, the REBb cells having a more fibroblastic appearance while the PROb cells had the capacity to form domes characterizing the functional polarization of the cell layer. The two clones could also be distinguished by their expression of proteins of intermediate filaments. Both expressed cytokeratins showing their epithelial origin, but only REGb cells displayed vimentin which is characteristic of mesenchymal or poorly differentiated epithelial cells. Furthermore, analysis of the expression of a series of glycoconjugate tissue antigens and an unknown protein (p120) showed that the PROb cells resembled more the normal adult digestive epithelium than the REGb cells did. In conclusion, it appears that in this model, the most aggressive cells, those resisting to the constraints imposed by the immune system, are also the more differentiated ones.

Adenocarcinoma↗
PubMed1990

Fucose and galactose receptor and liver recognition by lymphoma cells.

A syngeneic model system for the study of metastases is described. The system consisted of 2 lymphoma clones (A/63-I and A/63-2) derived from a single thymoma (A/63) induced by a wild-type Abelson-Moloney viral complex. Phenotype and genotype analyses revealed that both clones were derived from transformation of early T-cell precursors. An in vivo study of the colonizing potential following intravenous (i.v.) injection of clones showed that only the A/63-I cell clone colonized the liver. This observation was confirmed by quantitative analysis of organ distribution of both cell clones consecutive to i.v. injection of 125IUdR-labelled cells. In the same way, an in vitro study of the invasive potential of both clones was performed on frozen liver sections and showed that only the A/63-I cell clone had the ability to attach to liver. This specific adhesion was inhibited by L-fucose, D-galactose, N-acetyl-D-galactosamine (D-GalNAc) and with D-galactose- and L-fucose-containing neoglycoproteins. Differences in cell surface carbohydrates of the 2 cell clones were detected using various lectins: peanut agglutinin (PNA), Dolichos biflorus (DBA), Aleuria aurantia (AAA) and Galactia tenuiflora agglutinins (GTA). A/63-I was found to react strongly with PNA, DBA and GTA, and the removal of sialic acid by neuraminidase treatment increased DBA and PNA receptor sites of A/63-2 as compared to A/63-I. The present data suggest that cell-surface GalNAc, galactosyl and fucosyl residues are responsible for the ability of the A/63-I cell clone to recognize liver tissue probably through binding to a Kupffer-cell-associated lectin.

Abelson murine leukemia virus↗
PubMed1990

Correlation between cell surface oligosaccharides and tissue target-selective adhesion of two rat adenocarcinoma cell lines.

We observed that two rat colon adenocarcinoma variants originating from a single parental cell line and differing by their progressive and metastatic capacities in syngeneic BDIX rats differed by their organ distribution after intravenous injections. The PROb cells accumulated in the lung, wherefrom the REGb cells were rapidly cleared. In order to explore the role of cell surface glycoconjugates in organ-specific metastasis, cytofluorometric and histochemical studies using labelled lectins were performed. This revealed that the metastatic variant PROb presented more alpha-L-Fuc(1----2) beta D-Gal-R structures than the regressive nonmetastatic variant REGb. At variance, REGb cells exposed more D-galactosyl and N-acetyl-D-galactosaminyl residues than PROb cells. Monosacharides inhibited specifically cell adhesions on frozen organ sections. L-Fuc and N-acetyl-D-galactosamine (D-GalNAc) most strongly inhibited the adhesion of PROb cells on lungs, whereas D-Gal and D-GalNAc most strongly inhibited that of REGb cells. On the liver, adhesions of both cell lines were inhibited by D-Gal and D-GalNAc. These observations support the involvement of sugar-lectin receptors in the adhesion of these cells to the lungs or liver. The possible involvement of previously described lectins is discussed.

Adenocarcinoma↗
PubMed1989

Differences in glycosylation state of fibronectin from two rat colon carcinoma cell lines in relation to tumoral progressiveness.

We have investigated the biosynthesis and carbohydrate structure of fibronectin secreted by two rat colon carcinoma cell lines. The cell line Prob yields progressive tumors after s.c. injection in syngeneic BD IX rats while tumors developed by Regb cells disappear after 20 days. No difference was observed in the fibronectin biosynthesis from both cell lines; however, the glycosylation degree was higher in Regb than in Prob cells indicating probable differences in the posttransductional process. The analysis of the glycosylation nature shows that fibronectin doesn't bear O-linked carbohydrate chains. The fibronectin of progressive Prob cells is more sialylated than that of the regressive Regb ones. In addition, the tri- and tetraantennary glycans are more important in Prob, while the fucosylated triantennary glycans are three times higher in Regb cells. These differences in the glycosylation state of the fibronectins could explain their differential susceptibility to the proteases treatment. In fact, the low glycosylated fibronectin from the progressive Prob cells was more rapidly degraded by several proteases than that of regressive Regb cells. The identification of the specific sites of proteolytic cleavage by sodium dodecyl sulfate-polyacrylamide gel electrophoresis showed that the cell attachment domain as well as the collagen binding domain of Regb cell fibronectin are particularly protected against proteolytic degradation.

Adenocarcinoma↗
PubMed1989

Endothelial cell growth regulation by PGE1 analog misoprostol and indomethacin.

The role of prostaglandins on growth regulation of different cell types was investigated. We studied the effect of exogenous misoprostol in the presence or absence of indomethacin on the cell growth kinetics. Our results clearly show that misoprostol strongly inhibited the growth of several cancer cells but only slightly affected that of endothelial cells. Moreover, indomethacin alone (which decreases PG synthesis) had little effect on DNA synthesis in endothelial cells or C6 cells but inhibited colonic cancer cells. Conversely, misoprostol stimulated DNA synthesis in endothelial or C6 cells preincubated with indomethacin. This phenomenon was not observed with colonic cancer cells. The role of NSAIDs in the field of cytoprotection is discussed.

Alprostadil↗
PubMed1989

Differences in the release of 5'-nucleotidase and alkaline phosphatase from plasma membrane of several cell types by PI-PLC.

1. We have compared the effect of phosphatidyl inositol specific phospholipase C (PI-PLC) on the attachment of both 5'-nucleotidase and alkaline phosphatase to the liver plasma membrane from different species. 2. Our results demonstrate differences in the susceptibilities of both enzymes to PI-PLC treatment in relation to their origin. 3. These results were confirmed by immunoblotting using polyclonal anti-5'-nucleotidase antibodies. 4. In addition, in a single animal, susceptibility of both enzymes to PI-PLC treatment is different from one tissue to another. 5. The different percentages of released enzymes could be explained either by a polymorphism in the anchoring of these proteins at the cell surface membrane, or by a different steric hindrance or environment at the cleavage site itself.

5'-Nucleotidase↗
PubMed1988

Purification of bovine liver cytosolic 5'-nucleotidase. Kinetic and structural studies as compared to the membrane isoenzyme.

Cytosolic 5'-nucleotidase from bovine liver has been purified to homogeneity. Two affinity chromatographies on concanavalin A and 5'AMP-Sepharose columns result in a 12,000-fold purification. The sequential elution of glycoproteins from the concanavalin-A-Sepharose column with methyl alpha-D-glucoside and methyl alpha-D-mannoside greatly increases the degree of purification of the enzyme. Polyacrylamide gel electrophoresis in the presence of sodium dodecyl sulfate shows two subunits having apparent molecular masses of 65 kDa and 57 kDa respectively, while only one band at 70 kDa is observed in the case of the membrane-bound 5'-nucleotidase. Both the Stokes radii, measured by gel exclusion HPLC, and the sedimentation coefficient, determined by density gradient ultracentrifugation, indicate that the cytosolic enzyme is a heterodimer of about 130 kDa. This contrasts with the membrane-bound 5'-nucleotidase which is a homodimer of 140 kDa. Moreover, the antibodies raised against the membrane 5'-nucleotidase inhibited the cytosolic form indicating that a common antigenic determinant(s) exists between the two isoenzymes. However, structural differences are revealed by immunoblotting. In the same way, the effect of lectins suggests that differences in the structure of the carbohydrate chains exist between the two isoenzymes. The purified cytosolic enzyme has lower affinity for the nucleotides than does the membrane enzyme. In addition, while ADP, [alpha,beta-CH2]ADP and ATP were strong competitive inhibitors of the membrane enzyme, ADP and ATP activate the cytosolic form and [alpha,beta-CH2]ADP has no effect. Moreover, two pH optima at 7.5 and 9.5 are observed in the cytosolic enzyme while only one at 7.5 occurred in the membrane form. Finally the exogenous cations, MgCl2 and MnCl2, are necessary for the maximal activity of the cytosolic but not of the membrane 5'-nucleotidase. All these observations indicate that the two isoenzymes are different.

5'-Nucleotidase↗
PubMed1988

The carbohydrate moiety of mineral-bound proteins from fetal enamel: a basis for enamelins heterogeneity.

Enamelins were prepared from the soft enamel of bovine fetuses. They were purified on synthetic hydroxyapatite and separated in two fractions by affinity chromatography on a ConA-ultrogel column. The two fractions were different with respect to their electrophoretic behavior, stainability, amino acid composition, phosphorylation, and glycosylation. The ConA-binding fraction, consisting of three molecular species with apparent molecular weights of 33, 37, and 45 kD, contained organic phosphorus and high levels of sugars. The Gal/Man ratio suggested a biantennary structure. The ConA-unbound fraction contained two major molecular species with molecular weights of 70 and 56 kD, and represented 70% of the total enamelin preparation. The amino acid composition of this fraction showed a higher level of alanine and a lower level of proline when compared with that of total enamelins. Its sugar composition was unusual, being principally constituted of N-acetyl galactosamine and N-acetyl glucosamine.

Amino Acids↗