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T Bocker

Publications and source records attributed to T Bocker.

At least 19 recordsLinked to original sources
PubMed2000

Sequence analysis of the mismatch repair gene hMSH6 in the germline of patients with familial and sporadic colorectal cancer.

To evaluate the involvement of hMSH6 in colorectal cancer, the complete coding sequence and flanking intron regions of the gene were analyzed by DNA sequencing in 10 patients fulfilling Bethesda Guidelines for colorectal tumors and 10 patients with sporadic colorectal carcinoma. In addition, 10 mono- and 10 dinucleotide repeat markers were analyzed for microsatellite instability. A protein-truncating T insertion at codon 218 was identified in the index person of a hereditary non-polyposis colorectal cancer (HNPCC)-like kindred and was accompanied by a somatic T deletion in the tumor. The tumor of this patient was positive for mono- but negative for dinucleotide repeat instability and lacked allelic losses at loci frequently affected in colorectal carcinomas. A novel amino acid change, F340S, was found in a patient with sporadic colon and breast cancer and leukemia but was not detected in 246 chromosomes from healthy anonymous blood donors. In addition, we describe 2 silent and 15 intronic sequence variants not previously reported. Although the frequency is low, we present further evidence for hMSH6 germline mutations that predispose patients to HNPCC-like phenotypes and suggest that mono- and dinucleotide repeat instability testing may be useful for distinguishing between individuals harboring an hMSH2 or hMLH1 mutation and a mutation of the hMSH6 gene.

Adaptor Proteins, Signal Transducing↗
PubMed1999

Molecular diagnostics of cancer predisposition: hereditary non-polyposis colorectal carcinoma and mismatch repair defects.

Hereditary non-polyposis colorectal carcinoma accounts for 5-13% of all colorectal carcinomas and is inherited in a dominant fashion. Two different forms can be distinguished. Type I is restricted to colorectal cancers, whereas type II patients acquire acolorectal, endometrial, gastric, small intestinal and transitional carcinomas of the upper urinary tract. Germline mutations in the human mismatch repair genes (hMSH2, hMSH6, hMLH1, hPMS2) account for the majority of hereditary non-polyposis colorectal carcinoma. As a result of the mismatch repair deficiency, replication errors are not repaired, resulting in a mutator phenotype. Simple repetitive sequences (microsatellites) are especially prone to replication errors and analysis of their stability combined with immunohistochemical analysis of mismatch repair protein expression provides a rapid diagnostic strategy. For patients either (1) fulfilling the Amsterdam criteria for HNPCC, (2) with synchronous or metachronous hereditary non-polyposis colorectal carcinoma-related tumors, (3) with hereditary non-polyposis colorectal carcinoma-related tumors before the age of 45 and/or (4) with right sided CRC and mucinous, solid, or cribriform growth patterns, screening for mismatch repair deficiencies should be performed. The identification of colorectal cancers displaying a mutator phenotype has implications for both treatment and prognosis.

Adaptor Proteins, Signal Transducing↗
PubMed1999

hMSH5: a human MutS homologue that forms a novel heterodimer with hMSH4 and is expressed during spermatogenesis.

MutS homologues have been identified in nearly all organisms examined to date. They play essential roles in maintaining mitotic genetic fidelity and meiotic segregation fidelity. MutS homologues appear to function as a molecular switch that signals genomic manipulation events. Here we describe the identification of the human homologue of the Saccharomyces cerevisiae MSH5, which is known to participate in meiotic segregation fidelity and crossing-over. The human MSH5 (hMSH5) was localized to chromosome 6p22-21 and appears to play a role in meiosis because expression is induced during spermatogenesis between the late primary spermatocytes and the elongated spermatid phase. hMSH5 interacts specifically with hMSH4, confirming the generality of functional heterodimeric interactions in the eukaryotic MutS homologue, which also includes hMSH2-hMSH3 and hMSH2-hMSH6.

Amino Acid Sequence↗
PubMed1999

MLH1 promoter methylation and gene silencing is the primary cause of microsatellite instability in sporadic endometrial cancers.

Defective DNA mismatch repair in human tumors leads to genome-wide instability of microsatellite repeats and a molecular phenotype referred to as microsatellite instability (MSI). MSI has been reported in a variety of cancers and is a consistent feature of tumors from patients with hereditary non-polyposis colorectal cancer. Approximately 20% of cancers of the uterine endometrium, the fifth most common cancer of women world-wide, exhibit MSI. Although the frequency of MSI is higher in endometrial cancers than in any other common malignancy, the genetic basis of MSI in these tumors has remained elusive. We investigated the role that methylation of the MLH1 DNA mismatch repair gene plays in the genesis of MSI in a large series of sporadic endometrial cancers. The MLH1 promoter was methylated in 41 of 53 (77%) MSI-positive cancers investigated. In MSI-negative tumors on the other hand, there was evidence for limited methylation in only one of 11 tumors studied. Immunohistochemical investigation of a subset of the tumors revealed that methylation of the MLH1 promoter in MSI-positive tumors was associated with loss of MLH1 expression. Immunohistochemistry proved that two MSI-positive tumors lacking MLH1 methylation failed to express the MSH2 mismatch repair gene. Both of these cancers came from women who had family and medical histories suggestive of inherited cancer susceptibility. These observations suggest that epigenetic changes in the MLH1 locus account for MSI in most cases of sporadic endometrial cancers and provide additional evidence that the MSH2 gene may contribute substantially to inherited forms of endometrial cancer.

Adaptor Proteins, Signal Transducing↗
PubMed1999

[Correlation between histological and molecular mechanisms of carcinogenesis in stomach cancer].

Since gastric cancer is an exceptional heterogeneous tumor conflicting results have been obtained about the relationship between genotype and phenotype. From the molecular point of view gastric carcinoma diffuse type forms a distinct entity which is microsatellite stable, has almost no p53 mutations and exhibits in at least half of the cases mutations in the E-cadherin gene. In contrast, all other gastric carcinomas comprise a heterogeneous group of which about one third exhibits microsatellite instability (MSI) but no p53 protein stabilization or gene mutations. These tumors are either of pure intestinal (glandular) type or show large solid (medullary) tumor cell clusters. Thereby, in sporadic gastric cancer MSI is caused by loss of hMLH1 expression due to hypermethylation of the promotor region rather than by mutation of the gene itself. Tumors that are microsatellite stable (MSS) and show p53 alterations are either intestinal (about 70%) or a mixed-type encompassing at least 5% glandular and poorly differentiated diffuse components (about 30%). Whereas pure diffuse type gastric cancer is unlikely to develop from intestinal type carcinoma, this may, however, be the case in some advanced mixed-type gastric cancers.

Base Pair Mismatch↗
PubMed1999

[Aspirin suppresses microsatellite instability].

Nonsteroidal anti-inflammatory drugs (NSAIDs) exhibit cancer preventive effects and have been shown to induce regression of adenomas in FAP patients. In order to elucidate the probable underlying mechanism, the effect of NSAIDs on mismatch repair related microsatellite instability was investigated. Six colorectal cancer cell lines all but one deficient for human mismatch repair (MMR) genes were examined for microsatellite instability (MSI) prior and after treatment with Aspirin or Sulindac. For rapid in vitro analysis of MSI a microcloning assay was developed by combining Laser microdissection and random (PEP-) PCR prior to specific MSI-PCR. Effects of NSAIDs on cell cycle and apoptosis were systematically investigated by using flow cytometry and cell-sorting. MSI frequency in cells deficient of MMR genes (hMSH2, hMLH1, hMSH6) was markedly reduced after long-term (> 10 weeks) NSAID treatment. This effect was reversible, time- and concentration dependent. However, in the hPMS2 deficient endometrial cancer cell line (HEC-1-A) the MSI phenotype kept unchanged. According to cell sorting, non-apoptotic cells were stable and apoptotic cells were unstable. These results suggest that aspirin/sulindac induces a genetic selection for microsatellite stability in a subset of MMR-deficient cells and may thus provide an effective prophylactic therapy for HNPCC related colorectal carcinomas.

Anti-Inflammatory Agents, Non-Steroidal↗
PubMed1998

Aspirin suppresses the mutator phenotype associated with hereditary nonpolyposis colorectal cancer by genetic selection.

Nonsteroidal anti-inflammatory drugs (NSAIDs) are well-known cancer preventives, which have been largely attributed to their antiproliferative and apoptosis-inducing activities. In this study, we show that microsatellite instability (MSI) in colorectal cancer cells deficient for a subset of the human mismatch repair (MMR) genes (hMLH1, hMSH2, and hMSH6), is markedly reduced during exposure to aspirin or sulindac [or Clinoril, which is chemically related to indomethacin (Indocin)]. This effect was reversible, time and concentration dependent, and appeared independent of proliferation rate and cyclooxygenase function. In contrast, the MSI phenotype of a hPMS2-deficient endometrial cancer cell line was unaffected by aspirin/sulindac. We show that the MSI reduction in the susceptible MMR-deficient cells was confined to nonapoptotic cells, whereas apoptotic cells remained unstable and were eliminated from the growing population. These results suggest that aspirin/sulindac induces a genetic selection for microsatellite stability in a subset of MMR-deficient cells and may provide an effective prophylactic therapy for hereditary nonpolyposis colorectal cancer kindreds where alteration of the hMSH2 and hMLH1 genes are associated with the majority of cancer susceptibility cases.

Adaptor Proteins, Signal Transducing↗
PubMed1998

[Late manifestation of a fatal Behçet's disease with cardiac involvement and lethal outcome].

HISTORY AND CLINICAL FINDINGS: One year before admission a 67-year-old man of German origin developed extensive ulcerations of the limbs, later also of the trunk and neck. In addition to recurrent oral aphthous ulcers it was associated with erythema nodosum and intermittent arthritis of the elbow knee and ankle joints. During the last month he also had dyspnoea. Echocardiography revealed a dilated cardiomyopathy (DCM). He was admitted because of the progressive skin disorder. Physical examination showed a disoriented man with dyspnoea, cyanosis of the lips and pretibial oedema. He had aphthous ulcers in the mouth and on the genitals. Adamant Behçet disease was suspected. INVESTIGATIONS: Erythrocyte sedimentation rate was raised to 21/48 mm/h, white cell count to 15,800/microliter. Tests for HLA B5 and B27 were negative, skin biopsy revealed superficial necrotizing vasculitis of postcapillary venules. TREATMENT AND COURSE: Initially high doses of prednisolone, 100 mg/d intravenously) and azathioprine (100 mg/d orally) were administered, and within a few days both the skin and cardiac changes had regressed. Prednisolone dosage was reduced and cyclosporin (350 mg/d) substituted for azathioprine. He was discharged in a markedly improved general condition and with only a few tibial ulcerations. 4 months later he had a severe recurrence with dramatic mucocutaneous involvement and rapidly deteriorating DCM, together with radiological signs of pneumonia. He died 4 months later. INTERPRETATION: Although very rare, Behçet disease should even in the elderly patients be considered in the differential diagnosis: in the presence of appropriate symptoms cardiac involvement should be looked for.

Aged↗
PubMed1998

[Molecular cancer disposition diagnosis exemplified by colorectal carcinoma. What is the contribution of pathology?].

During the last few years, the molecular basis of several cancer predisposition syndromes has been discovered which offers new tools for cancer prevention and early detection. This will be demonstrated in one of the most frequent hereditary cancer syndromes, namely the hereditary nonpolyposis colorectal cancer (HNPCC) which accounts for about 5% to 8% of CRC. Thereby, families with exclusively CRC (Lynch type I syndrome) and those with extracolonic cancers especially of endometrium, stomach, small bowel and upper urinary tract (Lynch type II syndrome) can be discriminated. At the molecular level, HNPCC is caused by germline mutations in one of the mismatch repair genes (hMSH2, hMLH1, hMSH6, hPMS2). Thus, nucleotide mispairings occurring particularly within simple repetitive genomic sequences (microsatellites) during replication are no longer be repaired properly and can be demonstrated by PCR as so-called microsatellite instability (MSI). Since more than 90% of HNPCC associated and only about 15% of sporadic CRC show MSI, this test is a useful tool for HNPCC screening. In case of a negative result HNPCC is highly unlikely. In positive cases (with > or = 2 out of 5 unstable defined microsatellite markers) the definite molecular diagnosis can only be obtained by sequencing the mismatch repair genes from the patient's blood or normal DNA. As immunohistochemistry reveals loss of hMSH2 or hMLH1 expression in most MSI positive CRC, these data provide useful information for the sequencing strategy. Molecular tumor screening by MSI test and immunohistochemistry is recommended in patients i.) with a positive family history (acc. to the Amsterdam criteria), ii.) suffering from multiple HNPCC related carcinomas, iii.) with HNPCC related cancer before 45 ys of age, and iv.) with right-sided CRC exhibiting medullary, signet-ring or mucinous differentiation. Finally, these tests as well as genetic counseling and treatment of the patient need to be done by an interdisciplinary approach. Thereby, the pathologist can substantially contribute to identify HNPCC related carcinomas either by clinical or morphological criteria and to initiate the molecular screening test.

Cell Transformation, Neoplastic↗
PubMed1997

Microsatellite instability analysis: a multicenter study for reliability and quality control.

The molecular biology section of the Hereditary Non-Polyposis Colorectal Cancer study group-Germany, instituted a multicenter study to test the reliability and quality of microsatellite instability (MSI) analysis. Eight laboratories compared MSI analyses performed on 10 matched pairs of normal and tumor DNA from patients with colorectal carcinomas. A variety of techniques were applied to the detection of microsatellite changes: (a) silver and ethidium bromide staining of polyacrylamide gels; (b) radioactive labeling; and (c) automated fluorescence detection. The identification of highly unstable tumors and tumors without MSI was achieved in high concordance. However, the interpretation of the band patterns resulted in divergent classifications at several microsatellite marker loci for a large fraction of this tumor/normal panel. The data on more than 30 primers per case suggest that the enlargement of the microsatellite panel to more than 10 loci does not influence the results. In this study, cases with MSI in less than 10% of loci were classified as microsatellite stable, whereas MSI was diagnosed in cases with more than 40% of all markers unstable. We propose that a panel of five microsatellite loci consisting of repeats with different lengths should be analyzed in an initial analysis. When less than two marker loci display shifts in the microsatellite bands from tumor DNA, the panel should be enlarged to include an additional set of five marker loci. The number of marker loci analyzed as well as the number of unstable marker loci found should always be identified. These criteria should result in reports of MSI that are more comparable between studies.

Chromosome Deletion↗
PubMed1997

Diagnostic microsatellite instability: definition and correlation with mismatch repair protein expression.

Alterations of the length of simple repetitive genomic sequences (microsatellite instability, MSI) characterize a distinct mechanism of colorectal carcinogenesis. Such MSI has been found to be associated with hereditary nonpolyposis colorectal cancer (HNPCC) that involves mutation of the human mismatch repair genes hMSH2 and hMLH1 as well as many sporadic cancers of most tissue types. Although the study of MSI status is a useful tool for HNPCC screening and for the determination of tumor prognosis in sporadic cases of colorectal cancer, the reliability of MSI diagnosis is still a subject of debate. Here we have examined 58 primary colorectal tumors (selected from a cohort of 200) using 31 microsatellite markers that comprised the most frequent simple repeat types. The expression of the hMSH2 and hMLH1 mismatch repair proteins was studied by immunohistochemistry, and most patients were surveyed for at least 2 years. Reproducibility of gel interpretation, as well as diagnostic sensitivity and specificity of the MSI status, were determined. We found that unambiguous determination of band shifts as well as MSI diagnosis were closely related to the type of the marker repeat and that MSI could be subdivided into "high" MSI (>20% unstable loci), "low" MSI (<10% unstable loci), and microsatellite stable (0% unstable loci). One-half of the patients with high MSI tumors (n = 8) fulfilled either the Amsterdam criteria (n = 4), had at least one relative with HNPCC-related carcinoma (n = 2), or were diagnosed with colorectal cancer at an age below 45 years (n = 2). Fourteen of the 15 high MSI tumors had lost either hMSH2 (n = 8) or hMLH1 (n = 6) protein expression. In contrast, all of the low MSI tumors and the MSI-negative tumors displayed normal expression of hMSH2 and hMLH1. These studies provide a clear recommendation for the uniform use of a panel of 10 microsatellites and a definition of at least 40% instability (using these defined marker loci) in the diagnostic analysis of MSI.

Adenocarcinoma↗
PubMed1997

Female embryonic lethality in mice nullizygous for both Msh2 and p53.

The mutator hypothesis of tumorigenesis suggests that loss of chromosomal stability or maintenance functions results in elevated mutation rates, leading to the accumulation of the numerous mutations required for multistep carcinogenesis. The human DNA mismatch repair (MMR) genes are highly conserved homologues of the Escherichia coli MutHLS system, which contribute to genomic stability by surveillance and repair of replication misincorporation errors and exogenous DNA damage. Mutations in one of these MMR genes, hMSH2, account for about half of all cases of genetically linked hereditary non-polyposis colorectal cancer. Loss of function of p53 has also been proposed to increase cellular hypermutability, thereby accelerating carcinogenesis, although a clear role for p53 in genomic instability remains controversial. p53 is mutated frequently in a wide range of human cancers, including colonic tumours. Both Msh2- and p53-targeted knockout mice are viable and susceptible to cancer. Here we demonstrate that combined Msh2 and p53 ablation (Msh2-/-p53-/-) results in developmental arrest of all female embryos at 9.5 days. In contrast, male Msh2-/-p53-/- mice are viable, but succumb to tumours significantly earlier (t1-2 is 73 days) than either Msh2-/- or p53-/- littermates. Furthermore, the frequency of microsatellite instability (MSI) in tumours from Msh2-/-p53-/- mice is not significantly different than in Msh2-/- mice. Synergism in tumorigenesis and independent segregation of the MSI phenotype suggest that Msh2 and p53 are not genetically epistatic.

Animals↗
PubMed1997

Poorly differentiated colonic adenocarcinoma, medullary type: clinical, phenotypic, and molecular characteristics.

Clinicopathological evidence has accumulated that colorectal adenocarcinoma with minimal or no glandular differentiation constitutes two entities with different prognosis. In a series of 20 predominantly nonglandular, poorly differentiated adenocarcinomas, histological features, DNA content, p53 protein expression, Ki-ras mutation, and microsatellite instability were analyzed and correlated to the biology of the tumors. In addition, the presence of Epstein-Barr virus (EBV) transcripts was tested by RNA in situ hybridization and EBV DNA was demonstrated by nested polymerase chain reaction. Histologically, 13 tumors showed small uniform cells and 7 tumors showed large pleomorphic cells. Tumors with uniform cells exhibited more commonly an expansive growth pattern (69.2% versus 0%; P < 0.025) and a dense peritumor lymphoid infiltrate (84.6% versus 14.3%; P < 0.01) resembling their gastric counterpart, solid or medullary carcinoma. These tumors showed less frequent lymph node as well as hematogeneous metastases than pleomorphic carcinomas. In addition, they were usually diploid (84.6% versus 28.6%; P < 0.05) and lacked stabilization of the p53 protein (0% versus 42.9%; P < 0.05). No significant difference between the medullary and the pleomorphic tumor type was found with respect to bcl2 expression and the occurrence of Ki-ras mutations at codon 12. In contrast, microsatellite instability was almost totally restricted to poorly differentiated adenocarcinomas of the medullary type (100% versus 14.3%; P < 0.001). Finally, polymerase chain reaction revealed EBV DNA in 5 tumor specimens, which was, however, restricted to the peritumor lymphoid infiltrate as shown by in situ hybridization. Correlation with the biology of the tumors revealed that only one patient with the uniform cell type died due to metastastic disease during the follow-up period (median, 31 months), which was the case in five of the seven patients with the pleomorphic-type carcinoma (P < 0.025). Our results clearly indicate that the poorly differentiated colonic carcinoma with minimal or no glandular structures constitute two different entities, a medullary and a pleomorphic variant, which markedly differ in their phenotype, genotype, and prognosis.

Adult↗
PubMed1996

[Endosonographic demonstration of extrapancreatic and extraintestinal gastrinoma].

HISTORY AND CLINICAL FINDINGS: No cause had been found for chronic diarrhoea in a 57-year-old man. Up to 15 watery stools daily had been without relation to food intake and without blood admixture. But muscular cramps had developed, especially in the legs. The patient had a history of recurrent peptic ulcers for which a selective proximal vagotomy had been performed 13 years ago. Physical examination was unremarkable. INVESTIGATIONS: Alkaline phosphatase activity (182 U/l) and C-reactive protein (9.3 mg/l) were slightly raised; serum iron was 42 micrograms/dl, while all other routine laboratory tests, including protein electrophoresis, blood picture and differential count were within normal limits. Gastroscopy revealed ulcerative duodenitis, gastritis with erosions and numerous ulcers and reflux oesophagitis, grade III-IV. Endosonography showed enlarged gastric mucosal relief as sign of foveolar hyperplasia and a ca. 4 x 3 cm tumour next to the duodenal bulb. Gastrin level was 7537 pg/ml (normal < 150 pg/ml). Computed tomography and somatostatin receptor scintigraphy confirmed the site and size of the gastrinoma. TREATMENT AND COURSE: Treatment with omeprazole (40 mg three times daily) slightly improved the symptoms. The tumour was excised a week after diagnosis. The patient has been symptom-free since then. CONCLUSION: Chronic diarrhoea of unknown aetiology can be caused by an endocrine tumour; endosonography can often provide information on the diagnosis and location of such a tumour.

Chronic Disease↗
PubMed1996

[Miliary tuberculosis and silicosis with predominantly cerebral symptoms].

HISTORY AND CLINICAL FINDINGS: About 10 weeks before admission to hospital a 73-year-old woman developed a fever of up to 40 degrees C for three days. She then had subfebrile temperature for several weeks with some rises to 39 degrees C. She was known to have type II a diabetes mellitus and pulmonary silicosis, having worked in a porcelain and ceramic factory for many years. Before admission her cerebral functions were rapidly deteriorating, especially short-term memory. This was followed by increasing paraplegia of the legs with inability to walk. She finally had urinary and faecal incontinence and swallowing difficulties with tendency to aspiration, which necessitated hospitalisation. INVESTIGATIONS: Both lactate dehydrogenase (339 U/l) and C-reactive protein (112 mg/l) were elevated; the platelet count was low (73000/microliters). Cerebrospinal fluid was unremarkable, as was computed tomography of the skull. But magnetic resonance imaging revealed multiple spotty lesions with low contrast-medium uptake throughout the brain, pointing to a disseminated bacterial or mycotic infection. 3 days later the chest-ray showed small nodular soft shadows in the lungs, and lung functions had decreased. Mycobacteria were found in the urine and liver biopsy showed granulomatous hepatitis, establishing the diagnosis of miliary tuberculosis in the presence of silicosis. TREATMENT AND COURSE: Tuberculostatic treatment was instituted with four drugs (pyrazinamide, ethambutol, isoniazid and streptomycin. After 6 weeks the patient was again able to walk and continent of urine during the day. All cerebral functions gradually improved. CONCLUSION: Miliary tuberculosis should be included in the differential diagnosis of ill-defined feverish disease, especially in the elderly.

Aged↗
PubMed1996

Genomic instability in colorectal carcinomas: comparison of different evaluation methods and their biological significance.

In order to demonstrate the relationship between microsatellite instability and other types of genomic instability, a series of 56 sporadic colorectal carcinomas was investigated by flow cytometrical ploidy analysis, oligonucleotide fingerprinting, and microsatellite polymerase chain reaction (PCR). Stabilization of the p53 gene product was analysed by immunohistochemistry and proliferative activity was determined flow cytometrically and by silver staining of nucleolar organizer regions (AgNORs). Of the 56 carcinomas, 11 (19 per cent) exhibited microsatellite instability; 33 of the cases were aneuploid (59 per cent) and 29 (52 per cent) showed alterations of the oligonucleotide fingerprints. There was a significant correlation of microsatellite instability with localization of these tumours proximal to the splenic flexure, diploid DNA content, and less frequent p53 stabilization. A solid growth pattern, mucinous differentiation, and a Crohn's-like lymphoid infiltrate were also characteristic for those tumours. The results demonstrate for the first time a significantly lower proliferative activity in tumours with microsatellite instability. Data obtained from DNA flow cytometry or from oligonucleotide fingerprinting did not correlate with such tumour characteristics. It is proposed that the use of microsatellite PCR facilitates specifically the detection of a group of colorectal cancers which may differ in pathogenesis and perhaps prognosis.

Adult↗