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S Olschwang

Publications and source records attributed to S Olschwang.

At least 55 records · Page 3Linked to original sources
PubMed1997

Alternative genetic pathways in colorectal carcinogenesis.

The comparative typing of matched tumor and blood DNAs at dinucleotide repeat (microsatellite) loci has revealed in tumor DNA the presence of alleles that are not observed in normal DNA. The occurrence of these additional alleles is possibly due to replication errors (RERs). Although this observation has led to the recognition of a subtype of colorectal cancer with a high incidence of RERs (caused by a deficiency in DNA mismatch repair), a thorough analysis of the RER frequency in a consecutive series of colorectal cancers had not been reported. It is shown here that the extensive typing of 88 colorectal tumors reveals a bimodal distribution for the frequency of RER at microsatellite loci. Within the major mode (75 tumors, RER- subtype), the probability that a locus exhibited instability did not differ significantly among loci and tumors, being 0.02. The subsequent development of a statistical test for an operational discrimination between the RER- and RER+ subtypes indicated that the probability of misclassification did not exceed 0.001 in this series. The frequency of K-ras mutation was found to be equivalent in the two subtypes. However, in the RER+ tumors, the p53 gene mutation was less frequently detected, the adenomatous polyposis coli (APC) mutation was rare, and the biallelic inactivation of either of these genes was not observed. Furthermore, the concomitant occurrence of APC and tumor growth factor beta receptor type II gene alterations was found only once. These data suggest that the repertoires of genes that are frequently altered in RER+ and RER- tumors may be more different than previously thought.

Aged↗
PubMed1997

Concerted nonsyntenic allelic losses in hyperploid hepatocellular carcinoma as determined by a high-resolution allelotype.

Although the occurrence of loss of genetic material in hepatocellular carcinoma (HCC) has been documented both by cytogenetic analysis and by monitoring of allelic losses, a global overview of the extent and frequency of deletion occurring throughout the genome is not yet available. To contribute to this information, DNAs extracted from flow-sorted aneuploid nuclei from HCC and matched normal DNAs were typed for 275 microsatellite loci that were distributed along the autosomes. An average of 190 (69%) informative loci per case were generated on 48 HCC. Complete loss of heterozygozity in the tumor DNA was observed for 15.6% of the typed loci. The chromosome segments that were most frequently affected by deletion were: 8p (60%), 17p (48%), 1p (44%), 4q (42%), 16p (40%), 16q (39%), 6q (35%), 9p (30%), and 13q (29%). On average, 8 of the 39 chromosome segments studied per tumor carried at least one locus that demonstrated loss of heterozygosity (ie., the fractional allelic loss was 0.21). Groups of concerted nonsyntenic losses were observed for 16p and 1p and for 16p and 4q. The location of putative tumor suppressor genes on the most frequently deleted regions was confirmed and, in some cases, refined.

Adult↗
PubMed1997

[Colonic cancer: from molecular diagnosis to diagnostic and therapeutic procedure].

Studies of tumour cell genetic alterations have demonstrated the existence of two distinct groups of colorectal cancers. The first one is characterised by the existence of hyperploid tumour cells and frequent loss of heterozygosity. These colorectal cancers are the most common. The second one is characterised by the presence of microsatellite instability. Among the most frequent genetic alterations, the loss of heterozygosity on the short arm of chromosome 17 and the long arm of chromosome 18 seems to be indicators of a pejorative prognosis. In the same way the existence of a p53 mutation in tumour cells has been demonstrated as an independent prognostic factor in colorectal cancer. The indication of an adjuvant chemotherapy on the basis of such genetic alterations remains to be demonstrated by randomised trials.

Chromosome Mapping↗
PubMed1997

[Familial adenomatous polyposis and thyroid cancer].

Familial adenomatous polyposis may exhibit extracolonic tumors which include thyroid carcinoma. It has been recently suggested that thyroid carcinomas associated with familial adenomatous polyposis show distinct histologic features different from sporadic follicular or papillary thyroid carcinomas. We report a case of thyroid carcinoma in a young girl affected by familial adenomatous polyposis, whose thyroid tumor exhibited some of these features. This finding confirms the peculiar histologic phenotype of the thyroid carcinomas associated with familial adenomatous polyposis. Alterations of the APC gene responsible for familial adenomatous polyposis may play a role in the development of these thyroid cancers.

Adenomatous Polyposis Coli↗
PubMed1997

Somatic inactivation of the VHL gene in Von Hippel-Lindau disease tumors.

Von Hippel-Lindau (VHL) disease is a dominantly inherited disorder predisposing to retinal and CNS hemangioblastomas, renal cell carcinoma (RCC), pheochromocytoma, and pancreatic tumors. Interfamilial differences in predisposition to pheochromocytoma reflect allelic heterogeneity such that there is a strong association between missense mutations and risk of pheochromocytoma. We investigated the mechanism of tumorigenesis in VHL disease tumors to determine whether there were differences between tumor types or classes of germ-line mutations. Fifty-three tumors (30 RCCs, 15 hemangioblastomas, 5 pheochromocytomas, and 3 pancreatic tumors) from 33 patients (27 kindreds) with VHL disease were analyzed. Overall, 51% of 45 informative tumors showed loss of heterozygosity (LOH) at the VHL locus. In 11 cases it was possible to distinguish between loss of the wild-type and mutant alleles, and in each case the wild-type allele was lost. LOH was detected in all tumor types and occurred in the presence of both germ-line missense mutations and other types of germline mutation associated with a low risk of pheochromocytoma. Intragenic somatic mutations were detected in three tumors (all hemangioblastomas) and in two of these could be shown to occur in the wild-type allele. This provides the first example of homozygous inactivation of the VHL by small intragenic mutations in this type of tumor. Hypermethylation of the VHL gene was detected in 33% (6/18) of tumors without LOH, including 2 RCCs and 4 hemangioblastomas. Although hypermethylation of the VHL gene has been reported previously in nonfamilial RCC and although methylation of tumor-suppressor genes has been implicated in the pathogenesis of other sporadic cancers, this is the first report of somatic methylation in a familial cancer syndrome.

Chromosome Deletion↗
PubMed1997

[Localization of a tumor suppressor gene distal to D22S270 in colorectal cancers].

Recurrent allelic losses on chromosome 22q have been reported in colorectal cancer, distal to the NF2 gene, suggesting that another tumor suppressor gene might be involved. We report here the typing of 256 sporadic colorectal tumors and 18 colonic cancer cell lines using a set of chromosome 22 polymorphisms, ranging from 20 to 45. A panel of somatic cell hybrids, that allows to distinguish 11 bins in the 22q13 region, was used to localize 19 of the 45 selected markers and the putative tumor suppressor gene BZRP. Allelic-loss was observed in 43% of tumors. The minimal region of deletion that could be determined, telomeric to locus D22S270, refines significantly the position of the gene. The localization of the BZRP gene in this region led to a systematic screening for somatic point mutation. Direct sequencing of its coding sequence in 36 tumors hemizygous for chromosome 22 allowed the identification of three polymorphisms but failed to detect somatic mutation.

Adenocarcinoma↗
PubMed1996

Germline mutations in the Von Hippel-Lindau disease (VHL) gene in families from North America, Europe, and Japan.

Germline mutation analysis was performed in 469 VHL families from North America, Europe, and Japan. Germline mutations were identified in 300/469 (63%) of the families tested; 137 distinct intragenic germline mutations were detected. Most of the germline VHL mutations (124/137) occurred in 1-2 families; a few occured in four or more families. The common germline VHL mutations were: delPhe76, Asn78Ser, Arg161Stop, Arg167Gln, Arg167Trp, and Leu178Pro. In this large series, it was possible to compare the effects of identical germline mutations in different populations. Germline VHL mutations produced similar cancer phenotypes in Caucasian and Japanese VHL families. Germline VHL mutations were identified that produced three distinct cancer phenotypes: (1) renal carcinoma without pheochromocytoma, (2) renal carcinoma with pheochromocytoma, and (3) pheochromocytoma alone. The catalog of VHL germline mutations with phenotype information should be useful for diagnostic and prognostic studies of VHL and for studies of genotype-phenotype correlations in VHL.

Adrenal Gland Neoplasms↗
PubMed1996

Testing candidate loci on chromosomes 1 and 6 for genetic linkage to Peutz-Jeghers' disease.

Peutz-Jeghers' syndrome (PJS) is a disease with autosomal dominant inheritance, which is characterised by gastrointestinal hamartomata and characteristic melanin pigmentation. Three candidate sites for a PJS locus have recently been proposed, chromosomes 1p31-p32, 6q25 and 6p11-cen. At the first of these sites, a multipoint LOD score of 4.00 had been found, strongly suggesting genetic linkage to PJS. The last two candidate sites were suggested by the chromosomal breakpoints of a patient with an inv(6) and PJS. We have analysed up to 34 families in order to test each of the three candidate sites for linkage to PJS. No evidence was found in support of a Peutz-Jeghers' syndrome locus on chromosome 1p31-p32. The candidate region on 6q25 was also excluded. The region close to the centromere of chromosome 6 has not been excluded and there is some evidence of linkage to a marker near 6cen, although genetic heterogeneity in PJS must be proposed to account for a gene at this site.

Chromosomes, Human, Pair 1↗
PubMed1995

High resolution genetic map of the adenomatous polyposis coli gene (APC) region.

Familial adenomatous polyposis coli (APC) is a dominantly inherited colorectal cancer susceptibility disease caused by mutation in a gene called APC and located on chromosome 5q21. Presymptomatic diagnosis of this condition is recommended because it enables restriction of the efficient but demanding prevention program to those relatives that are genetically affected. The large size of the APC gene makes the direct search for the causal alteration difficult to implement in routine diagnostic laboratories. Because APC appears to be genetically homogeneous with alteration in a single locus causing the disease, cosegregation analysis may represent an alternative efficient method for presymptomatic diagnosis. However, the reliability of the risk estimation by linkage analysis in APC families is hampered by the lack of a short range genetic map of the APC locus. A combined approach including genotyping of 65 APC families, analysis of the CEPH database, and complementary typing of both APC and CEPH families has made it possible to derive the following genetic map: Centromere-[D5S82-D5S49]-0.02-D5S122-0.01-D5S136 -0.01-D5S135-0.02-[APC-D5S346-MCC]-0.04-[D5S81-D5S6 4]-Telomere. This order, which differs from previously proposed genetic maps, is fully compatible with recent physical mapping data. These data should contribute to increase the reliability of the presymptomatic test for APC.

Adenomatous Polyposis Coli↗
PubMed1995

Predominance of normal karyotype in colorectal tumors from hereditary non-polyposis colorectal cancer patients.

We report the cytogenetic study of 9 colorectal tumors arising in patients with hereditary non-polyposis colorectal cancer (HNPCC). According to the cytogenetic classification of colorectal tumors previously proposed by us, 2 cases were of the trisomic type, 2 were of the monosomic type, and 5 had a normal karyotype. This represents a significant excess of tumors with normal karyotype in HNPCC tumors (56%) compared to sporadic cases (10/184 = 5%).

Adenomatous Polyposis Coli↗
PubMed1995

Familial adenomatous polyposis: desmoid tumours and lack of ophthalmic lesions (CHRPE) associated with APC mutations beyond codon 1444.

An earlier study has shown that FAP patients with mutations in codons 136-302 of the APC gene do not develop congenital hypertrophy of the retinal pigment epithelium (CHRPE), whereas those with mutations in codons 463-1387 regularly do. Here we present data on 36 patients from 20 families with mutations in codons 1445-1578. These patients lack CHRPE. Furthermore, with the exception of three prepubertal children all patients with mutations in codons 1445-1578 developed desmoid tumours. This relationship between certain extracolonic manifestations and site of the APC mutation points to a specific role of the APC protein in different tissues.

Adenomatous Polyposis Coli↗
PubMed1995

DNA-based presymptomatic diagnosis for the von Hippel-Lindau disease by linkage analysis.

Von Hippel-Lindau (VHL) disease is an autosomal dominantly inherited condition characterized by a predisposition to the development of haemangioblastoma, renal cell carcinoma and phaeochromocytoma. The gene which, when altered, causes the disease was cloned in 1993, and maps within a series of known polymorphic loci in the 3p25-p26 region. To optimize a DNA-based presymptomatic diagnosis, we have selected six highly informative microsatellite loci, closely linked to the VHL gene. Genotyping using a multiplex-PCR approach was performed in 26 affected families including 99 asymptomatic relatives born from an affected parent. Ninety-six subjects were informative with one or more markers, 76 being informative with markers on both sides of the gene. Combination of age-related and DNA-based risk information improved the accuracy of risk assessment for 90 at-risk patients (91%) and allowed attribution of risk with a confidence limit higher than 0.98 in 79 cases (88%).

Adolescent↗
PubMed1995

Genetic predispositions to colorectal cancer.

Genetic predispositions to colorectal cancer can schematically be divided in two categories depending on the presence or absence of a diffuse polyposis i.e.: a large number of adenomatous polyps in the colon and rectum of affected patients. These syndromes are referred as familial adenomatous polyposis coli and hereditary non polyposis colon cancer (HNPCC) respectively. The gene which when altered causes familial adenomatous polyposis coli is called APC and has been identified in 1991 but the function of its product remained elusive. Recent experimental data indicate that the APC protein can interact with catenins and tubulins, two groups of proteins known to be components of adherens junctions and cytoskeleton. Thus the APC protein may play a role in cell adhesion and in transduction of signal regulating the cell cycle. Of more immediate clinical interest is the observation that specific APC mutations appear to participate in the severity of the disease and determine the development of hypertrophy of the retinal pigment epithelium, a diagnostically important manifestation of the APC disease found in 70% of the patients. HNPCC syndromes have been recognized as being frequently associated with a defect in the DNA mismatch repair pathway. Furthermore, human genes, demonstrating homology with the bacterial DNA repair genes MutS and MutL, have been identified and shown to be altered in several HNPCC families. There are now indications that genotyping of tumor DNA at particular loci, termed microsatellite, may contribute in the identification of patients genetically predisposed to tumor development.(ABSTRACT TRUNCATED AT 250 WORDS)

Adenomatous Polyposis Coli↗
PubMed1995

[Towards an allotype of second generation colon cancer].

A subset of genetic alterations distinguishes two groups of colon cancers. In the first group instability of microsatellite loci due to a defective DNA mismatch repair system is observed. The second group is characterized by recurrent losses of chromosome regions, frequently associated with hyperploidization. We have developed a technique which enables a fine description of allelic losses in this second group of tumours. The typing of 278 loci in 47 hyperploid colon cancers has provided information for an average of 160 loci per tumour. The high frequency of allelic losses on chromosomes 17, 18 and 5 was confirmed thus validating our methodological approach. Several additional chromosome segments were observed lost in over 40% of the cases, suggesting that tumour suppressor genes may map within these regions. Further technical development should contribute to the identification of these genes.

Alleles↗
PubMed1994

Association of p53 mutations with short survival in colorectal cancer.

BACKGROUND/AIMS: Mutations in p53, a tumor suppressor gene located on chromosome 17p, are the most frequent genetic alterations found in human cancers. Increased intracellular concentration of p53, which is frequently but not systematically related to p53 mutation, has been proposed to be associated with poor prognosis in some tumor types. In colorectal cancer, this significance is still a matter of debate. To directly investigate the relationship between prognosis and p53 mutation, this study screened a series of 85 colorectal carcinomas for mutations in exons 5-8 of this gene. METHODS: Polymerase chain reaction-amplified products from tumor DNA were analyzed by denaturing gradient gel electrophoresis and direct DNA sequencing. RESULTS: Forty-four tumors were found to be mutated (52%). A strong correlation between the presence of a mutation and short survival was observed (P = 0.003). When tumors were classified according to their histological stage, a multivariate Cox model analysis showed that p53 mutation, rather than 17p allelic loss (previously proposed to convey prognostic information), was retained as the only independent prognostic factor (relative risk, 2.25; 95% confidence interval, 1.06-4.80; P < 0.029). CONCLUSIONS: Combined with staging, direct monitoring of p53 mutation improves prognostic accuracy for colorectal cancer.

Aged↗
PubMed1994

Mapping of 18 probes on human chromosome 18 using single- and double-color FISH.

Fluorescence in situ hybridization (FISH) techniques were applied to the mapping of 18 probes from chromosome 18, permitting seven new assignments: D18S16 (18p11.31), D18S12 (18p11.1), D18S1 (18q12.2), D18S13 (18q21.31), D18S18 (18q21.31), D18S14 (18q21.33), and D18S17 (18q23). In addition, the localization of D18S3 in 18p11.3 was confirmed and that of D18S6, previously mapped in 18p11, was changed to 18q21.13. Finally, a more accurate mapping for nine probes was proposed: D18S7 (18q12.2), D18S10 (18q12.2), D18S24 (18q21.13), D18S8 (18q21.13), GRP (18q21.31), BCL2 (18q21.33), D18S5 (18q22.1), D18S19 (18q22.1), and D18S11 (18q22.3). The ordering of probes located in close proximity was made possible by combined use of single-color FISH with direct assignment on banded chromosomes, chromosomal length measurements, and double-color FISH.

Chromosome Mapping↗