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M Bracke

Publications and source records attributed to M Bracke.

At least 37 records · Page 2Linked to original sources
PubMed1996

Regulation of the invasion suppressor function of the cadherin/catenin complex.

Invasion is the cause of cancer malignancy. Invasion results from the cross-talk between cancer cells and host cells, building molecular invasion-promoter and invasion-suppressor complexes. The E-cadherin/catenin invasion-suppressor complex is regulated multifactorially, at multiple levels and sometimes in a reversible way. Mutations in the E-cadherin gene combined with loss of the wild type allele, causing irreversible downregulation, has been demonstrated only in a minority of human cancers. Posttranslational and reversible downregulation has been ascribed to tyrosine phosphorylation of beta-catenin. Phosphorylation is also implicated in transmembrane receptor signal transduction through the E-cadherin/catenin complex. E-cadherin interacts with E-cadherin on another cell through a dimeric adhesion zipper, involving the histidine-alanine-valine (HAV) sequence of the first extracellular domains. This is the major extracellular like of the E-cadherin/catenin complex, though not the only one. Intracellularly, the list of proteins that bind to or signal through the complex or through one or more of its elements is steadily growing. Extrinsic factors may influence the complex. At least in vitro, insulin-like growth factor-I, retinoic acid, tangeretin and tamoxifen were shown to upregulate the functions of the E-cadherin/catenin complex including inhibition of invasion.

Animals↗
PubMed1996

A3 domain is essential for interaction of von Willebrand factor with collagen type III.

von Willebrand factor (vWF) mediates platelet adhesion at sites of vascular damage. It acts as a bridge between receptors on platelets and collagens present in the connective tissue. Two collagen binding sites have been identified on the A1 and A3 domain of the vWF subunit. To study the functional importance of these binding sites, we have made two deletion mutants that lack the A1 domain (residues 478-716; delta A1-vWF; Sixma et al. Eur. J. Biochem, 196, 369, 1991 [1]) or the A3 domain (residues 910-1113; delta A3-vWF). After transfection in baby hamster kidney cells overexpressing furin, the mutants were processed and secreted efficiently. Ristocetin or botrocetin induced platelet binding was normal for delta A3-vWF as was binding to heparin and factor VIII. As reported by Sixma et al. (1) delta A1-vWF still binds to collagen type III, indicating that the A3 domain is sufficient for the interaction. In the current study, we investigated the binding of delta A3-vWF to collage type III. When preincubated on collagen type III it did not support platelet adhesion under flow conditions, whereas it was able to support platelet adhesion when coated directly to a glass surface. The binding of 125I-delta A3-vWF to collagen was specific but maximal binding was about 40 times less compared to 125I-vWF. When added at 25 times excess, delta A3-vWF did not compete with 125I-vWF for binding to collagen type III, whereas delta A1-vWF did. The binding of 125I-delta A3-vWF could be blocked by excess unlabeled vWF but not by delta A1-vWF. In conclusion, we demonstrate that the A3 domain in vWF contains the major collagen binding site. The major binding site present on the A3 domain and the minor site present on A1 bind to different sites on collagen.

Animals↗
PubMed1995

Iron regulation of siderophore biosynthesis and transport in Pseudomonas putida WCS358: involvement of a transcriptional activator and of the Fur protein.

Pseudobactin 358 is the yellow-green fluorescent siderophore produced by Pseudomonas putida WCS358 in conditions of iron limitation. The genes encoding for siderophore biosynthesis are iron-regulated at the transcriptional level. Previous work has shown that a positive regulator, PfrA, is absolutely required for the activation under iron-limiting conditions of pseudobactin 358 biosynthesis. In this study we identified a set of Tn5 insertion mutants of strain WCS358 which lost the ability to activate an iron-regulated siderophore promoter. These mutants no longer produced pseudobactin 358. Molecular analysis revealed that they carried a Tn5 insertion in a gene, designated pfrl (Pseudomonas ferric regulator), which codes for a protein (Pfrl) of 19.5 kDa. Pfrl contains a putative helix-turn-helix motif typical of DNA-binding proteins and has homology to two DNA-binding transcriptional activators, Fecl from Escherichia coli and Pupl from P. putida. The proposed role of Pfrl in strain WCS358 is an activator protein regulating pseudobactin 358 biosynthesis under iron limitation. The pfrl promoter region contains a sequence which displays high identity to the Fur-box consensus. This 19 bp consensus sequence is recognized by Fur, an iron-binding repressor protein found in many different bacteria. The E. coli Fur protein can bind to the pfrl promoter region, indicating that this activator gene is likely to be iron-regulated by Fur. We also report the identification and characterization of the P. putida WCS358 fur gene. The Fur protein of strain WCS358 is structurally and functionally similar to other cloned Fur proteins from other bacterial species.

Amino Acid Sequence↗
PubMed1995

Cancer metastasis: negative regulation by an invasion-suppressor complex.

Invasion is the hallmark of tumor malignancy. We situate invasion within microecosystems comprising neoplastic cells as well as host cells. Modulation of invasion within such systems is ascribed to balances between promoter and suppressor pathways. The E-cadherin/alpha-, beta-, gamma-catenin complex has an invasion-suppressor function as evidenced by transfections either with sense cDNA encoding these molecules or with antisense cDNA inhibiting their expression. Loss of heterozygosity at the E-Cadherin (uvo) locus has been reported, but mutations in the E-cadherin gene seem to be rare. Downregulation of E-cadherin occurred at the level of transcription or of mRNA stability. Ex vivo cultures from invasive tumors or metastases produced cells that were homogeneously E-cadherin-positive and noninvasive in vitro. These observations have led to the idea that factors in the host downmodulate the E-cadherin complex and promote invasion most probably in a transient way.

Animals↗
PubMed1994

Downregulation in vivo of the invasion-suppressor molecule E-cadherin in experimental and clinical cancer.

The invasion-suppressor molecule E-cadherin (E-CAD) can be regulated at multiple levels: synthesis, processing and stability of mRNA; synthesis, processing and stability of protein; localization and posttranslational modification of protein; binding to catenins (E-CAD-associated proteins); and size and charge of cell surface glycosaminoglycans. Loss of E-CAD antigen and of E-CAD function in vivo has been observed with cell lines that homogeneously expressed functional E-CAD in vitro. These observations led to the idea that factors in the host may downmodulate E-CAD on the cancer cells, thereby promoting cell invasion. Nude mouse cancers that were homogeneously E-CAD-positive and noninvasive in vitro, formed by epithelioid MDCK or NMuMG cells, stained heterogeneously for E-CAD; such cancers were invasive and metastatic. The in vivo downmodulation appeared to be transient. Ex vivo cultures from primary cancers, as well as from metastases, produced homogeneously E-CAD-positive and noninvasive cells. Downmodulation did not occur when cells were micro-encapsulated and then implanted in the mouse, suggesting a role for immediate cancer cell-host cell contact. Similar in vitro/in vivo/ex vivo experiments with mouse MO4 fibrosarcoma cells, transfected with E-CAD cDNA under the control of a b-actin promotor, showed downregulation at the transcriptional or mRNA stability level. This downregulation was rapidly reversible upon ex vivo culture of the tumor cells. TGF-bl and IGF-I were found, respectively, to downregulate and upregulate the expression or the function of E-CAD. We speculate that IGF-1 restores the function of E-CAD through interaction of the IGF-I tyrosine kinase receptor with the catenin-actin cytoskeletal complex. In human cancers, immunohistochemistry has revealed changes in E-cadherin that agree with the experimental data on transient downmodulation of the invasion-suppressor function of E-cadherin by host factors.

Animals↗
PubMed1993

Fibroblast growth factor-mediated growth regulation and receptor expression in embryonal carcinoma and embryonic stem cells and human germ cell tumours.

FGFs have been implicated in the induction of mesoderm in amphibian development and are present in the mouse embryo at stages that would be appropriate for a similar function in mammals. Primitive ectoderm would then be the target tissue. We have now changes in the expression of receptors for FGFs during the differentiation of embryonal carcinoma (EC) and embryonic stem (ES) cells from the mouse. These cells resemble those of the inner cell mass and later primitive ectoderm. On Northern blots of mRNA from undifferentiated cells, transcripts for FGF R1, R2 and R3 are expressed. All are upregulated during differentiation of ES cells and are upregulated or remain constant as EC cells differentiate. FGF R4 is only expressed after differentiation to derivatives resembling parietal endoderm. By contrast in human EC cells, FGF R2 is downregulated during differentiation, FGF R1 and FGF R3 are unchanged and FGF R4 is expressed before and after differentiation. In both human and mouse EC cells three members of the FGF family (a FGF, b FGF and k FGF, also known as FGFs 1,2 and 4) are mitogenic in serum-free medium and one (KGF or FGF 7) appears to have no effect on growth although cellular morphology is altered. Differences between human and mouse cells are primarily in the effects of heparin on the FGF-induced response.

Animals↗
PubMed1993

Differential regulation of gelatinase B and tissue-type plasminogen activator expression in human Bowes melanoma cells.

A comparison of the production of tissue-type plasminogen activator (t-PA) and gelatinases A and B was made at the mRNA and protein levels in human Bowes melanoma cells treated with phorbol myristate acetate (PMA). Immunocytochemical analysis confirmed previous quantitative data on PMA-mediated induction of t-PA. It also showed that t-PA immunoreactivity can be restrained to the local environment of the producing cell, most probably by interaction with extracellular matrix components. Zymographical analysis showed that gelatinase B protein was induced by PMA, whereas gelatinase A remained at the constitutive level. Protein kinase C (PKC) appeared to be involved in this regulation since, after PMA treatment (1) the PKC activity was found to be translocated from the cytosol to the particulate fraction of the cells and (2) addition of staurosporine and H-7 blocked the gelatinase B increase. Northern-blot hybridization showed a transient rise in t-PA and gelatinase B mRNA levels whereas gelatinase A mRNA levels remained unchanged. When c-fos and c-jun mRNAs were investigated, only that of c-fos was affected by PMA. Activation by PMA can be kinetically ordered as follows: translocation of PKC to the membrane fraction, transcription of the c-fos gene and eclipsing of gelatinase B mRNA, increase in steady-state mRNA levels of t-PA and gelatinase B and, finally, secretion of t-PA and gelatinase B glycoproteins. Our data also suggest that various proteases that are known to cooperate in the remodeling of the extracellular matrix can be differently regulated in one tumor-cell type.

Cell Compartmentation↗
PubMed1993

Expression of E-cadherin in embryogenetic ingression and cancer invasion.

Homophilic interactions of E-cadherin serve the organization of embryonic and adult epithelia and counteract cancer invasion. The role of E-cadherin as an invasion-suppressor molecule has been demonstrated cancer. Regulation of embryonic ingression and cancer invasion via E-cadherin occurs at transcriptional, translational and post-translation levels.

Animals↗
PubMed1992

E-cadherin expression: a counterbalance for cancer cell invasion.

Invasion, eventually leading to metastasis, is presented as the result of a balance between the activation of 2 sets of genes, coined i+ (invasion promotor) and i- (invasion suppressor) genes. Experiments in vitro have indicated that the homotypic homophilic epithelial cell--cell adhesion molecule E-cadherin (L-CAM; uvomorulin; cell CAM 120/80; Arc-1; rrl antigen) is an i- gene product. In several cell families, manipulation of E-cadherin at the level of the protein by antibody-mediated inactivation, at the level of the mRNA by antisense DNA transfection, and at the level of the genome by sense DNA transfection respectively resulted in induction and suppression of invasiveness. Nude mouse tumors from non-invasive homogeneously E-cadherin-positive cell populations were found to be invasive and metastatic. These tumors expressed E-cadherin in a heterogeneous manner, the undifferentiated cells being negative; but tumor-derived cells in culture were again E-cadherin-positive, indicating downregulation of this protein by host factors. Several types of human cancers showed a similar heterogeneity suggesting a relationship between downregulation of E-cadherin and invasion. Our current research focus is on the factors responsible for E-cadherin downregulation in experimental and human cancers.

Animals↗
PubMed1992

Interleukin-1 is a motility factor for human breast carcinoma cells in vitro: additive effect with interleukin-6.

Interleukin-1 beta (Il-1 beta) and interleukin-1 alpha (Il-1 alpha) were shown to act as motility factors for the human breast carcinoma cell lines SK-BR-3 and ZR-75-1 in vitro. Both cytokines induced transition from the stationary to the motile phenotype (spreading). Il-1 beta stimulated translocation, shape change and random migration (chemokinesis) of SK-BR-3 cells as demonstrated by time-lapse video recordings and by a modified Boyden chamber assay. Interleukin-6 (Il-6) stimulated spreading of the SK-BR-3 cells; an additive effect with Il-1 beta on spreading and fast plasma membrane movements was evidenced. In the SK-BR-3 cell line, the signal transduction of Il-1 beta and Il-6 differed, since only the effect of Il-6 on spreading was sensitive to pertussis toxin. Both Il-1 beta and Il-6 required protein synthesis to stimulate spreading, since cycloheximide inhibited the effect of the cytokines. Induction of an autocrine loop of Il-6 in the SK-BR-3 cells by Il-1 beta was unlikely, since after stimulation with Il-1 beta, no induction of Il-6 activity was measured, nor was inhibition of stimulated spreading seen in the presence of an antiserum against Il-6. Addition of Il-8 or of an antiserum against Il-8 did not affect spreading. We concluded that Il-1 and Il-6 could act as motility factors for human breast carcinoma cells, in both an independent and an additive way.(ABSTRACT TRUNCATED AT 250 WORDS)

Breast Neoplasms↗
PubMed1991

Intratester and intertester reliability of the cervical range of motion device.

The purpose of this study was to investigate the intratester and intertester reliability of the Cervical Range of Motion instrument (CROM) for measuring cervical flexion, extension, lateral flexion, and rotation. Twenty able-bodied subjects were tested by two testers on two different occasions. Pearson product-moment correlations for intratester reliability ranged from .63 to .90 for tester one and from .62 to .91 for tester two. Intertester reliability was good. Coefficients ranged from .80 to .87 for session one and .74 to .85 for session two. Paired data t-tests showed that there were no significant differences between testers or sessions (p = .01). The results suggest that the CROM has acceptable intratester and intertester reliability. The CROM has many benefits including ease of application and reliability. More research is needed on patients with cervical dysfunction.

Adult↗
PubMed1990

The presence of plasmin receptors on three mammary carcinoma MCF-7 sublines.

We studied plasmin receptors on 3 MCF-7 sublines: MCF7, MCF7R which was derived by transfection with v-Ha-ras oncogene, and MCF7MF which has been studied for the secretion of procathepsin D in the presence of estrogen. All 3 sublines bound plasmin (Pli) with a much higher affinity than plasminogen (Pg). The number of binding sites was increased about 4-fold by weak proteolytic pretreatment of tumor cells. Transfection by v-Ha-ras oncogene did not apparently change the affinity of Pli binding sites (KD 27-26 nM) and increased their number very slightly (3,800 against 3,200 fmoles/mg protein). However, this number was 5 times higher for MCF7MF (15,000 fmoles/mg protein) and the affinity was 4 times lower (106 nM). MCF7 and MCF7R sublines have previously been reported to be non-invasive in the in vitro invasion assay system (embryo chick heart muscle) but tumorigenic and metastatic in nude mice. In contrast, the MCF7MF subline has been shown to be invasive in both in vivo and in vitro invasion systems. Thus, the number of Pli binding sites at the MCF7 tumor-cell surface may be associated directly or indirectly with tumor-cell invasiveness.

Animals↗
PubMed1990

Hormone sensitivity in vitro and in vivo of v-ras-transfected MCF-7 cell derivatives.

Human mammary carcinoma cell lines (MCF-7) were analysed for their hormone sensitivity before and after transfection with a v-Ha-ras oncogene or with a neomycin-resistance gene followed by selection in vitro or in vivo. Our aim was to test how the expression of the ras oncogene would influence the estradiol sensitivity of MCF-7 cells. In culture, MCF-7 cells expressing the viral p21 oncogene product, as compared to parental MCF-7 cells and their control derivatives, showed lower levels of a 67-kDa estrogen receptor. Progesterone receptors, however, remained sensitive to up-regulation by estrogens. The oncogene-expressing cells were less sensitive than all controls to stimulation of proliferation by 10(-8)M estradiol or to inhibition of proliferation by 2-CH3-4-OH tamoxifen, and this was not dependent upon the type of culture medium used. After s.c. or i.p. injection into female athymic nude mice, ovariectomized or left intact, the growth of MCF-7 cells expressing the ras oncogene product and of all control cells was sensitive to stimulation by estrogen supplementation. Conversely, cell lines derived from tumors generated with long latency in untreated athymic nude mice by v-ras-expressing MCF-7 cells showed efficient formation of quickly growing tumors in the absence of estrogen supplementation. No differences were observed in invasion and metastasis of the different MCF-7 cell types injected into athymic nude mice that were supplemented with estrogens or not.

Animals↗
PubMed1989

Acquisition of tumorigenic potential in the human myoepithelial HBL100 cell line is associated with decreased expression of HLA class I, class II and integrin beta 3 and increased expression of c-myc.

The human breast cell line HBL100 acquires the capacity to invade normal tissues and to replace them by proliferation in vitro only at high passage levels (HPL). These cells therefore are a useful model for studying tumor progression in vitro. We have analyzed the expression of cell-surface markers supposed to be involved in the control of the neoplastic process. Quantitative flow cytometry has revealed that: (1) spontaneous expression of HLA class-I antigens strongly decreases in HPL HBL100 cells vs. LPL cells, which parallels amplification and over-expression of c-myc oncogene; (2) HLA DR antigens can be induced by IFN-gamma in LPL but not in HPL HBL100 cells; (3) HBL100 cells secrete a soluble protein factor which specifically inhibits HLA DR induction by IFN-gamma even in heterologous cell systems; (4) 50% of LPL HBL100 cells express integrin beta 3, whereas HPL HBL100 cells lose this antigen; (5) this cell line is myoepithelial in origin, since 100% of HBL100 cells exhibit the CD10 antigen. Our data stress a role of HLA antigens, of some integrins and of c-myc in the acquisition of malignant potential by myoepithelial mammary cells of the HBL100 line.

Biomarkers, Tumor↗