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Biomedical subjects

R Montesano

Publications and source records attributed to R Montesano.

At least 73 records · Page 4Linked to original sources
PubMed1996

An antisense oligonucleotide to the notch ligand jagged enhances fibroblast growth factor-induced angiogenesis in vitro.

Angiogenesis, or the formation of new blood vessels, plays a central role in a number of physiologic and pathologic conditions, including wound healing, diabetic retinopathy, and solid tumor growth, and endothelial cells can be induced to mimic this process in vitro. Using a modification of the differential display method (Zimrin, A. B., Villeponteau, B., and Maciag, T. (1995) Biochem. Biophys. Res. Commun. 213, 630-638), we isolated the human homolog of the Jagged ligand for the Notch receptor from human endothelial cells exposed to fibrin and demonstrate that the Jagged transcript, but not the Notch 1 or Notch 2 transcripts, are up-regulated by fibrin. Interestingly, the addition of an antisense Jagged oligomer to bovine microvascular endothelial cells grown on a collagen gel resulted in a marked increase in invasion and tube formation in the underlying gel in response to fibroblast growth factor. In contrast, no effect was observed on vascular endothelial growth factor-induced angiogenesis under identical conditions. These data suggest that Jagged-Notch signaling is able to regulate fibroblast growth factor-induced endothelial cell migration in vitro, an early event during angiogenesis in vivo.

Calcium-Binding Proteins↗
PubMed1996

Genetic alterations in esophageal cancer and their relevance to etiology and pathogenesis: a review.

Cancer of the esophagus exists in 2 main forms with different etiological and pathological characteristics-squamous cell carcinoma (SCC) and adenocarcinoma (ADC). This review focuses on the occurrence of genetic alterations in SSC and ADC of the esophagus and on their possible implications for the elucidation of the etiology and pathogenesis of these cancers. The most common alterations found in esophageal cancers include allelic losses at chromosomes 3p, 5q, 9p, 9q, 13q, 17p, 17q and 18q, as well as mutations of p53 (mostly missense), Rb (deletions), cyclin DI (amplifications) and c-myc (amplifications). The sequence of occurrence of these alterations with respect to histopathological tumor progression is discussed. Our findings underscore the different etiology and pathogenesis of SCC vs. ADC and suggest that the genetic alterations observed may represent molecular fingerprints of critical risk involved in the development of these 2 cancers.

Adenocarcinoma↗
PubMed1996

DNA damage and repair in mutagenesis and carcinogenesis: implications of structure-activity relationships for cross-species extrapolation.

Previous studies on structure-activity relationships (SARs) between types of DNA modifications and tumour incidence revealed linear positive relationships between the log TD50 estimates and s-values for a series of mostly monofunctional alkylating agents. The overall objective of this STEP project was to further elucidate the mechanistic principles underlying these correlations, because detailed knowledge on mechanisms underlying the formation of genotoxic damage is an absolute necessity for establishing guidance values for exposures to genotoxic agents. The analysis included: (1) the re-calculation and further extension of TD50 values in mmol/kg body weight for chemicals carcinogenic in rodents. This part further included the checking up data for Swain-Scott s-values and the use of the covalent binding index (CBI); (2) the elaboration of genetic toxicity including an analysis of induced mutation spectra in specific genes at the DNA level, i.e., the vermilion gene of Drosophila, a plasmid system (pX2 assay) and the HPRT gene in cultured mammalian cells (CHO-9); and (3) the measurement of specific DNA alkylation adducts in animal models (mouse, rat, hamster) and mammalian cells in culture. The analysis of mechanisms controlling the expression of mammalian DNA repair genes (alkyltransferases, glycosylases) as a function of the cell type, differentiation stage, and cellular microenvironment in mammalian cells. The 3 classes of genotoxic carcinogens selected for the project were: (1) chemicals forming monoalkyl adducts upon interaction with DNA; (2) genotoxins capable of forming DNA etheno-adducts; and (3) N-substituted aryl compounds forming covalent adducts at the C8 position of guanine in DNA. In general, clear SARs and AARs (activity-activity relationships) between physiochemical parameters (s-values, O6/N7-alkylguanine ratios, CBI), carcinogenic potency in rodents and several descriptors of genotoxic activity in germ cells (mouse, Drosophila) became apparent when the following descriptors were used: TD50 estimates (lifetime doses expressed in mg/kg b.wt. or mmol/kg b.wt.) from cancer bioassays in rodents; the degree of germ-cell specificity, i.e., the ability of a genotoxic agent to induce mutations in practically all cell stages of the male germ-cell cycle of Drosophila (this project) and the mouse (literature search), as opposed to a more specific response in postmeiotic stages of both species; the Mexr-/Mexr+ hypermutability ratio, determined in a repair assay utilizing Drosophila germ cells; mutation spectra induced at single loci (the 7 loci used in the specific-locus test of the mouse (published data), and the vermilion gene of Drosophila); and doubling doses (DD) in mg/kg (mmol/kg) for specific locus test results on mice. By and large, the TD50 values, the inverse of which can be considered as measures of carcinogenic potency, were shown to be predictable from knowledge of the in vivo doses associated with the absorbed amounts of the investigated alkylators and with the second-order constant, kc, reaction at a critical nucleophilic strength, nc. For alkylating agents kc can be expressed as the second-order rate constant for hydrolysis, kH2O, and the substrate constant s:kH2OTD50 is a function of a certain accumulated degree of alkylation, here given as the (average) daily increment, ac, for 2 years exposure of the rodents. The TD*50 in mmol/kg x day) could then be written: [formula: see text] This expression would be valid for monofunctional alkylators provided the reactive species are uncharged. This is the case for most SN2 reagents. Although it appears possible to predict carcinogenic potency from measured in vivo doses and from detailed knowledge of reaction-kinetic parameter values, it is at present not possible to quantify the uncertainty of such predictions. One main reason for this is the complication due to uneven distribution in the body, with effects on the dose in target tissues. The estimation can be impro

Alkylating Agents↗
PubMed1996

Low frequency of p16/CDKN2 gene mutations in esophageal carcinomas.

Mutational analysis of the p16/CDKN2 gene was conducted by direct sequencing of the whole coding sequence (exons 1-3 and flanking splicing sites) in 21 esophageal squamous-cell carcinomas and 3 adenocarcinomas from a high-incidence area of Italy. Two inactivating mutations were found in exon 1 of the gene (both in squamous-cell carcinoma), whereas no mutations were detected in exon 2, where most of the sequence changes reported so far have been located, or in exon 3. Southern blot analysis of exon 2 in this set of samples and in a complementary set of 12 tumor samples from France did not show homozygous deletions or detectable gene rearrangements. Thus, p16/CDKN2 gene alterations do not appear to play a major role in the group of patients examined.

Adenocarcinoma↗
PubMed1996

TGF-beta1 induces morphogenesis of branching cords by cloned mammary epithelial cells at subpicomolar concentrations.

The factors which control the formation of lactiferous ducts during mammary gland development are not yet fully understood. To address this issue, we assessed the effect of the multifunctional cytokine transforming growth factor-beta-1 (TGF-beta1) on the morphogenetic properties of TAC-2.1 mammary epithelial cells grown in collagen gels. Here we demonstrate that TGF-beta1, has a biphasic effect on these cells: whereas relatively high concentrations (0.5-5 ng/ml) inhibit colony formation, lower concentrations (5-100 pg/ml = 200fM-4pM) stimulate colony elongation and branching, resulting in the formation of an extensive network of epithelial cords. We suggest that, in concert with other regulatory factors, low concentrations of TGF-beta1 promote mammary gland ductal morphogenesis.

Animals↗
PubMed1996

Aflatoxin exposure and cytogenetic alterations in individuals from the Gambia, West Africa.

Aflatoxin-albumin adducts in peripheral blood provide a measure of exposure to aflatoxin over the previous 2-3 months. In the present study, the levels of these adducts were determined in a group of individuals from The Gambia, West Africa and were compared in a cross-sectional study to the levels of various cytogenetic alterations (chromosomal aberrations, micronuclei, sister chromatid exchanges) in the same individuals to test whether an increase in genetic damage is associated with an increased exposure in this population. Of 35 subjects tested for aflatoxin-albumin adducts, all but 3 were positive. There were no correlations between the adduct level and the number of cytogenetic abnormalities at the individual level. A comparison of the cytogenetic alterations was made between Gambian individuals and a group of 22 healthy people from Italy where aflatoxin exposure is expected to be low. The levels of structural chromosomal aberrations, sister chromatid exchanges and micronuclei were all higher in the former group. Overall, these data are indicative of a higher exposure to genotoxins in Gambian subjects, one of which are aflatoxins, but suggest that more specific genetic markers of aflatoxin exposure are required to further examine the link between aflatoxin exposure and genetic alterations.

Adolescent↗
PubMed1996

Somatic point mutations in the p53 gene of human tumors and cell lines: updated compilation.

In 1994 we described a list of approximately 2500 point mutations in the p53 gene of human tumors and cell lines which we had compiled from the published literature and made available electronically through the file server at the EMBL Data Library. This database, updated twice a year, now contains records on 4496 published mutations (July 1995 release) and can be obtained from the EMBL Outstation-the European Bioinformatics Institute (EBI) through the network or on CD-ROM. This report describes the criteria for inclusion of data in this database, a description of the current format and a brief discussion of the current relevance of p53 mutation analysis to clinical and biological questions.

CD-ROM↗
PubMed1996

Modulation of clusterin gene expression in the rat mammary gland during pregnancy, lactation, and involution.

The mammary gland provides an excellent system for investigating factors involved in the regulation of epithelial growth, differentiation, morphogenesis, and involution. We have recently demonstrated that clusterin gene expression is associated with epithelial differentiation and morphogenesis during murine embryogenesis. In the present study, we have analyzed expression of clusterin in the rat mammary gland with particular emphasis on the periods of pregnancy and lactation. By Northern blot analysis we show that clusterin mRNA is present in virgin rat mammary glands, that it is increased during pregnancy and strongly down-regulated during lactation, and that mRNA levels return progressively to those found in virgin rats during the course of involution. Total protein levels, as assessed by Western blot analysis, were also seen to decrease during lactation. In situ hybridization showed that strong expression of clusterin was localized to epithelial cells of developing lactiferous ducts and alveoli during pregnancy, and confirmed that epithelial clusterin expression is down-regulated during lactation. This down-regulation was reproducibly observed in mothers to which pups were returned after 2 days of weaning, suggesting that maternal mammary clusterin production is under hormonal control. These results show that clusterin gene expression is highest in alveolar and tubular epithelial cells during pregnancy and lowest during lactation, when the protein synthetic machinery of differentiated alveolar epithelial cells is devoted to milk production. This suggests that clusterin may be involved not only in mammary gland involution but also in the regulation of tubuloalveolar morphogenesis and alveolar epithelial cell differentiation in the adult rat mammary gland.

Animals↗
PubMed1996

Angiogenesis: a paradigm for balanced extracellular proteolysis during cell migration and morphogenesis.

Extracellular proteolysis is required for matrix degradation and the regulation of cytokine activity during angiogenesis, and this is dependent on a cohort of proteases and protease inhibitors produced by endothelial and nonendothelial cells. The plasminogen activator (PA)/plasmin system has been extensively investigated in these processes, and descriptive studies have demonstrated that urokinase-type PA (uPA), uPA receptor (uPAR) and PA inhibitor-1 (PAI-1) are expressed by endothelial cells during angiogenesis in vivo. In vitro studies have led to the notion that normal capillary morphogenesis is dependent on a protease-antiprotease equilibrium. These findings are discussed in the context of recent observations on uPA-, uPAR-, PAI-1 and plaminogen-deficient mice, in which developmental and physiological angiogenesis appear to occur normally. This has led to a reevaluation of the role of the PA/plasmin system during angiogenesis. In particular, these observations raise the possibility that the role of this system may be limited to situations in which endothelial cells encounter and must degrade fibrin in order to form new capillary sprouts.

Animals↗
PubMed1996

Temporal cell-type-specific mRNA expression of O6-methylguanine-DNA methyltransferases in liver of rats treated with dimethylnitrosamine.

The intercellular distribution of O6-methylguanine-DNA methyltransferase (MGMT) mRNA expression has been investigated at the individual cell level in the liver of rats treated with dimethylnitrosamine using in situ hybridization. Male BDIV rats were orally administered with a single dose of dimethylnitrosamine (5 or 10 mg/kg) and were killed at 24, 48, and 96 hours after exposure. Constitutive MGMT mRNA expression was found in bile duct cells, vascular endothelial cells, and fibrous cells; however, weak or negative expression was detected in hepatocytes and Kupffer cells. On the other hand, after exposure to dimethylnitrosamine, inducible MGMT mRNA was rapidly expressed in hepatocytes, especially in the centrilobular area at earlier time points, confirming our previous studies in which enzymatic activity has been measured in different purified cell populations obtained by differential centrifugation. Immunohistochemical detection of the O6-methylguanine-DNA adduct formation was demonstrated in a dose-dependent fashion and was mainly found in the centrilobular hepatocytes where high levels of MGMT mRNA were present. These results suggest a correlation between the induction of this repair activity and DNA damage; however, the relationship between MGMT mRNA and enzyme activity remains to be fully established for all cell types.

Administration, Oral↗
PubMed1996

Synergistic effect of hyaluronan oligosaccharides and vascular endothelial growth factor on angiogenesis in vitro.

The aim of the present study was to determine whether hyaluronan (HA) degradation products, which have been shown to be angiogenic in vivo, influence endothelial cell invasion of a 3-dimensional matrix, an essential component of the neovascularization process. Using a previously described in vitro assay, we demonstrate that like the angiogenic cytokines basic fibroblast growth factor (bFGF) and vascular endothelial growth factor (VEGF), HA oligosaccharides (OHA) induce bovine microvascular endothelial cells to invade a 3-dimensional collagen gel within which they form capillary-like tubes, with an optimal effect at approximately 0.5 to 2 micrograms/ml. Strikingly, co-addition of OHA (0.5 - 2 micrograms/ml) and VEGF (30 ng/ml), but not co-addition of OHA and bFGF (10 ng/ml), induced an in vitro angiogenic response that was greater than the sum of the effects elicited by either agent separately. In contrast to OHA, native high molecular weight HA was consistently inactive, whether added alone or in combination with VEGF or bFGF. Because endothelial cell invasion is believed to require extracellular proteolytic activity, we also investigated the effect of OHA on the plasminogen activator (PA)-plasmin system. OHA (0.01 to 1 microgram/ml) but not native high molecular weight HA induced a dose-dependent increase in mRNA levels of urokinase type PA (uPA), urokinase type PA receptor and PA inhibitor type 1, and a parallel increase in the functional activity of urokinase type PA and PA inhibitor type 1, as determined by zymography and reverse zymography, respectively. The effects of OHA on proteolytic activity were additive with those of VEGF, but not with those of bFGF. Taken together, these results demonstrate that OHA modulate the invasive and proteolytic properties of bovine microvascular endothelial cells and synergize specifically with VEGF in the induction of angiogenesis in vitro. We suggest that the synergism between OHA and VEGF plays a role in the regulation of angiogenesis and that it may be exploited therapeutically in situations that would benefit from stimulation of new blood vessel growth.

Adrenal Cortex↗
PubMed1996

Aflatoxin-albumin adducts: a basis for comparative carcinogenesis between animals and humans.

The study objectives were (a) to correlate AFB1 serum albumin adduct levels with AFB1-DNA adduct levels in liver in different rodent species to determine whether the former could serve as a marker of hepatic DNA adduct levels irrespective of species, and (b) to relate the levels of both adducts to differences in susceptibility to tumor induction by AFB1 in the different species. Finally, an attempt was made to compare the dose response for AFB1-albumin adduct formation in the rodent species with that in human populations exposed environmentally to AFB1. Three strains of rat (Fischer 344, Wistar, and Sprague-Dawley), and one strain each of guinea pig (Hartley), hamster (Syrian golden), and mouse (C57BL) were treated by gavage with up to 14 daily doses of between 1 and 80 mug AFB1/kg body weight. Animals were killed 24 h after 1, 3, 7, or 14 days treatment. A dose response in both AFB1-albumin and AFB1-DNA adducts was seen for all species and strains with steady-state adduct levels at 14 days. In rat strains at 14 days after treatment with 20 mu g/kg, the mean AFB1-albumin levels were between 24 and 26 pg AFB1-lysine equivalent/mg albumin, and the mean AFB1-DNA adduct levels were between 1.5 and 2.5 pmol (8, 9-dihydro-8- (2, 6-diamino-4-oxo-3, 4-dihydro-pyrimid-5-ylforamido-)- 9-hydroxy) AFB1/mg DNA. The level of both adducts was in the following order: rat > guinea pig > hamster > mouse. In the case of AFB1-albumin, the mean adduct level at 14 days in the three rat strains was approximately 1.5, 3.0, and 8-fold higher than in the guinea pig, hamster, and mouse, respectively. When the levels of the albumin and DNA adducts at 14 days were plotted against each other for all species and strains, a correlation was observed (r = 0.83; P = < 0.0001; n = 57; two-tailed test) suggesting a constant relationship between the level of binding of AFB1 to serum albumin and liver DNA. The levels of AFB1-albumin adduct also reflect at least qualitatively the relative susceptibility of the different species to AFB1 carcinogenesis; the rat is sensitive and the hamster and mouse are resistant. The level of AFB1-albumin adduct formed as a function of a single dose of AFB1 in rodents was compared to data from humans exposed environmentally to AFB1. This comparison yielded a value for the three rat strains of between 0.3 and 0.51 pg AFB1-lysine equivalent/mg albumin/1 mu g AFB1/kg body weight and a value for the mouse of <0.025. The best estimate for people from The Gambia and southern China was 1.56 pg/mg albumin for the same exposure. These data suggest that humans exposed to AFB1 form amounts of albumin addducts, and by extrapolation amounts of DNA adducts, closer to those observed in AFB1-sensitive species and 1-2 orders of magnitude higher levels than the AFB1-resistant species.

Aflatoxins↗
PubMed1996

Molecular etiopathogenesis of esophageal cancers.

The occurrence and the relevance in squamous cell carcinomas (SCC) and Barrett's adenocarcinomas (ADC) of genetic alterations, namely mutations in the p53 gene, allelic loss at various chromosomal loci and altered expression of genes involved in the regulation of cell proliferation, are described and discussed with reference to the etiology and pathogenesis of esophageal cancers. Mutations in the p53 gene occur in both SSC and ADC with a frequency of up to approximately 80%, although with a strikingly different pattern of mutations. In ADC, a very high frequency of G > A transitions at CpG dinucleotides was observed, whereas in SCC, mutations at A:T base pairs was comparatively high. In addition, in SCC, the frequency of p53 mutations was related to tobacco smoking. These data therefore indicated that such mutation analysis could provide valuable insight into the etiology of this cancer. It is also apparent that the genetic alterations involving genes other than p53 are also present in the natural history of esophageal cancer. The significance of these genetic changes as well as alterations of expression of cell cycle regulatory genes in esophageal carcinogenesis is briefly discussed.

Adenocarcinoma↗
PubMed1995

p53 mutations in esophageal tumors from high-incidence areas of China.

Carcinomas of the upper digestive tract (squamous-cell carcinoma of the esophagus, adenocarcinoma of the cardia) from 24 patients residing in Linxian (China) and near-by high-incidence areas were analyzed for mutations in exons 5-8 of the p53 tumor-suppressor gene. Mutations were identified by polymerase chain reaction amplification and direct sequencing in 50% of the specimens. Eleven tumors harbored a single base-pair substitution leading to either an amino-acid substitution (8 tumors) or a chain-termination signal (3 tumors), and one tumor revealed a 15-bp deletion in exon 7 with a silent base substitution adjacent to the deletion site. Mutations occurred in all 4 exons examined, with a preponderance in exon 5. Of the 6 mutations identified among the 14 adenocarcinomas examined, 3 were G to T transversions, a mutation that has thus far been absent from reported mutations in Barrett's esophageal adenocarcinomas and dysplasias from patients residing in Europe and North America.

Adenocarcinoma↗