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Biomedical subjects

A O Vortmeyer

Publications and source records attributed to A O Vortmeyer.

At least 37 records · Page 2Linked to original sources
PubMed2000

Limitations on the quantitative determination of telomerase activity by the electrophoretic and ELISA based TRAP assays.

Telomerase is a promising new tumor marker and can be detected using the TRAP (Telomeric Repeat Amplification Protocol) method. To address factors affecting its quantitative determination, we evaluated two commercial TRAP assays, an electrophoretic and an ELISA assay formats, using cultured cells and human tumor samples. We found that both TRAP assays had a limited linearity from 250 to 5000 tumor cells, with a similar intra-assay variation. The quantification of TRAP products was affected by high cell number in sample, the presence of non-tumor cells, and interfering substances in patient specimens. Because both assays have different limitations, determination of telomerase by a combined use of the two may provide more accurate information on the telomerase activity in a specimen. Extracts of specimens should also be tested at several concentrations to insure that the result is not being falsely decreased by an inhibitor. The quantitative results for telomerase activity by the TRAP assays, however, should be interpreted cautiously.

Cell Count↗
PubMed2000

Distinction between dysplasia-associated lesion or mass (DALM) and adenoma in patients with ulcerative colitis.

Polyps with epithelial dysplasia in ulcerative colitis (UC) represent either dysplasia-associated lesions or masses (DALMs) or sporadic adenomas. DALMs are frequently associated with associated carcinoma and are an indication for colectomy. Removal of the polyp is treatment of choice for sporadic adenomas. Differentiating between these 2 lesions is not always easy. The goal of this study was to distinguish DALMs from adenomas in patients with UC on a genetic basis. We evaluated genetic alterations in DALMs and compared them with a previously published set of dysplastic polyps in patients with UC that were considered adenomas for the following reasons: (1) polyps were located outside of current active disease; (2) polyps had histological features of sporadic adenomas; and (3) patients displayed a uneventful follow-up after polypectomy (UC-adenomas). In addition, adenomas not associated with UC were studied. Genetic alterations on chromosome 3p were assessed for the markers D3S1766, D3S2409, and D3S2387. LOH with or without microsatellite instability was found in 70%, 37%, and 57% of cases of DALM, respectively. In contrast, UC-adenomas lesions exhibited genetic alterations in 8.3%, 11.7%, and 15.3% for the respective markers. Spontaneous adenomas exhibited genetic alterations in 10.5%, 7.1%, and 0% of cases, which were not significantly different from the UC-adenoma results. These results indicate that UC-adenomas are genetically and biologically similar to sporadic adenomas and that UC-adenomas may biologically represent sporadic adenomas, supporting on a genetic basis the criteria chosen to diagnose adenomas in UC. Genetic markers on chromosome 3p may be useful in the differential diagnosis between DALM and UC-adenomas.

Adenoma↗
PubMed2000

Teratomatous genotype detected in malignancies of a non-germ cell phenotype.

Originating from post-meiotic germ cells, mature ovarian teratomas (MOT) are genetically homozygous tumors within heterozygous hosts. MOT may be associated with malignant tumors of a non-germ cell phenotype (so-called malignant transformation). Based on the presence of in situ changes, some cases have been hypothesized to arise from teratomatous tissue. However, other malignancies associated with mature teratomas, such as sarcomas, may originate from either teratomatous elements or preexisting somatic ovarian tissue. Eight cases of MOT containing various histologic types of malignancy, including four squamous cell carcinomas, two sarcomas, one thyroid carcinoma, and one carcinoid tumor, were selected for study. Using selective tissue microdissection and PCR-based analysis of the extracted DNA, we compared the genotypic pattern of the mature teratomatous components to the associated malignant neoplasm with a random panel of highly informative genetic markers for different chromosomes. In all eight cases, genetic analysis of the malignant component revealed a homozygous genotype. In seven cases, the genetic profiles of mature teratomas and the associated malignant tumors were identical, suggesting a direct pathogenetic relationship between these lesions. In one case, the malignant component revealed homozygosity of different alleles compared with mature teratoma, suggesting independent teratomatous growth processes. This finding indicates that some ovarian malignancies of the non-germ cell phenotype arise in teratoma and fall into the spectrum of germ cell tumors.

DNA, Neoplasm↗
PubMed2000

Missense mutation of the MET gene detected in human glioma.

Multiple mechanisms, such as gene mutations, amplifications, and rearrangements, as well as perturbed mitogen and receptor function, are likely to contribute to glioma formation. The MET (also known as c-met proto-oncogene located at 7q31-34 has been shown to be amplified in human gliomas, and activating mutations within the tyrosine kinase domain of MET have been causally related to tumorigenesis in hereditary papillary renal cell carcinoma. To elucidate the role of MET gene in glioma formation, sporadic gliomas from 11 patients were examined for MET gene mutations and allelic duplications or deletions by polymerase chain reaction-single strand conformational polymorphism analysis and fluorescence in situ hybridization. Three of 11 sporadic gliomas showed a deletion of one copy of the MET gene, and a specific METgene missense mutation in the remaining gene copy was detected in one of those tumors. The corresponding sequence in non-tumor DNA was normal in all cases. Three of 11 sporadic gliomas showed duplication of one copy of the MET gene, but none of them contained mutations. One tumor showed METamplification without mutation. Three showed neither allelic change nor mutation. These data suggest that somatic MET gene mutation may play a role in the development of a subgroup of sporadic gliomas. However, MET mutations appear to be absent in the majority of sporadic gliomas.

Adult↗
PubMed1999

A model for CD8+ CTL tumor immunosurveillance and regulation of tumor escape by CD4 T cells through an effect on quality of CTL.

Understanding immune mechanisms influencing cancer regression, recurrence, and metastasis may be critical to developing effective immunotherapy. Using a tumor expressing HIV gp160 as a model viral tumor Ag, we found a growth-regression-recurrence pattern, and used this to investigate mechanisms of immunosurveillance. Regression was dependent on CD8 T cells, and recurrent tumors were resistant to CTL, had substantially reduced expression of epitope mRNA, but retained the gp160 gene, MHC, and processing apparatus. Increasing CTL numbers by advance priming with vaccinia virus expressing gp160 prevented only the initial tumor growth but not the later appearance of escape variants. Unexpectedly, CD4 cell depletion protected mice from tumor recurrence, whereas IL-4 knockout mice, deficient in Th2 cells, did not show this protection, and IFN-gamma knockout mice were more susceptible. Purified CD8 T cells from CD4-depleted mice following tumor regression had more IFN-gamma mRNA and lysed tumor cells without stimulation ex vivo, in contrast to CD4-intact mice. Thus, the quality as well as quantity of CD8+ CTL determines the completeness of immunosurveillance and is controlled by CD4 T cells but not solely Th2 cytokines. This model of immunosurveillance may indicate ways to enhance the efficacy of surveillance and improve immunotherapy.

Animals↗
PubMed1999

Deletion analysis of the adenomatous polyposis coli and PTCH gene loci in patients with sporadic and nevoid basal cell carcinoma syndrome-associated medulloblastoma.

BACKGROUND: Medulloblastomas can occur sporadically or may be associated with hereditary tumor syndromes including familial adenomatous polyposis (FAP) and nevoid basal cell carcinoma syndrome (NBCCS). METHODS: The authors performed a retrospective analysis for allelic deletion of the adenomatous polyposis coli (APC) and PTCH gene loci using paraffin embedded medulloblastoma specimens from patients who were admitted to Children's National Medical Center in Washington, DC, between 1982 and 1997. Thirty-five cases from which tumor and normal tissue could be procured were analyzed. Two of the analyzed cases had a positive family and personal history for NBCCS; in both cases the histology of the medulloblastoma revealed a desmoplastic phenotype. Thirty-three cases were not known to be associated with hereditary disease; 2 of those cases revealed desmoplastic and 31 cases revealed nondesmoplastic "classic" medulloblastoma histology. RESULTS: Although medulloblastoma tumorigenesis has been associated strongly with FAP associated with APC germline mutation, none of the 22 informative sporadic cases revealed loss of heterozygosity of the APC gene locus. PTCH gene deletion was detected in the tumors of both patients with NBCCS. In contrast, only 1 of 33 sporadic medulloblastomas revealed PTCH gene deletion. The sporadic case with PTCH gene deletion did not demonstrate the desmoplastic phenotype. CONCLUSIONS: In conjunction with previous studies, the data from the current study confirm that allelic deletion occurs in NBCCS-associated medulloblastomas, consistent with the role of PTCH as a tumor suppressor gene. However, in sporadic medulloblastomas, allelic deletion of PTCH is an infrequent event. Morphologic examination in conjunction with genetic analysis of PTCH gene deletion in medulloblastoma tissue may prove to be a quick and efficient test with which to screen for NBCCS in patients with medulloblastomas. Although medulloblastoma is a component of Turcot syndrome with demonstrated APC mutations, APC gene deletions appear to be absent or very uncommon in patients with sporadic and NBCCS-associated medulloblastomas.

Adenomatous Polyposis Coli↗
PubMed1999

Allelic imbalance in the clonal evolution of prostate carcinoma.

BACKGROUND: To understand better the genetic basis of the clonal evolution of prostate carcinoma, the authors analyzed the pattern of allelic loss in 25 matched primary and metastatic prostate tumors. METHODS: Twenty-five cases were selected from the surgical pathology files of the Mayo Clinic from patients who had undergone radical retropubic prostatectomy and bilateral lymphadenectomy between 1987-1991. All patients had regional lymph node metastases at the time of surgery. DNA samples for the analysis of allelic loss pattern were prepared from primary tumors and matched synchronous lymph node metastases by tissue microdissection. The oligonucleotide primer pairs for the microsatellite DNA markers were D8S133, D8S136, D8S137, ANK1 on chromosome 8p12-21, LPLTET on chromosome 8p22, and D17S855 (intragenic to the BRCA1 gene) on chromosome 17q21. One case was not informative at any of the loci tested and was excluded from further analysis. RESULTS: The overall frequency of allelic imbalance was 79% in primary tumors and 88% in paired metastases. Of 24 informative cases, 14 patients (58%) showed the same pattern of allelic loss or retention in matched primary and metastatic tumors at all marker locus; discordant allelic loss was observed in the remaining 10 patients (42%). Four patients showed loss of the same allele at one or more marker loci in both primary and metastatic tumors, but discordant allelic loss was observed at other marker loci. Five patients showed allelic loss in at least one genetic marker in the metastatic tumor but not in its matched primary tumor. Five patients displayed loss of one allele at one or more marker loci in a primary tumor but not in the matched metastases. There was no significant difference in the frequency of allelic imbalance between primary and metastatic tumors at any marker analyzed (P>0.05). CONCLUSIONS: These data suggest that different patterns of allelic deletion may be acquired during cancer progression to metastases. The differences in genetic composition between primary prostate carcinoma and its metastases may be related to intrinsic cancer heterogeneity, overall genetic instability, and clonal divergence.

Aged↗
PubMed1999

Perivascular cells harboring multiple endocrine neoplasia type 1 alterations are neoplastic cells in angiofibromas.

Although neoplasia is caused by clonal proliferation of cells, the resulting tumors are frequently heterogeneous, being composed of both neoplastic and reactive cells. Therefore, identification of tumors as neoplastic processes is frequently obscured. We studied cutaneous angiofibroma, which is a tumor of unknown etiology. Combined analysis using immunohistochemistry, selective tissue microdissection, fluorescence in situ hybridization, sequencing analysis, and deletion analysis of the multiple endocrine neoplasia type 1 locus succeeded in the identification of a population of genetically altered, neoplastic cells in these tumors. This approach may be valuable in the future in identifying the etiology of other tumors of unknown etiology.

Angiofibroma↗
PubMed1999

VHL gene deletion and enhanced VEGF gene expression detected in the stromal cells of retinal angioma.

OBJECTIVE: Retinal angioma frequently occurs in von Hippel-Lindau (VHL) disease. However, VHL gene alterations have not been documented in retinal angiomas. METHODS: Using tissue microdissection and polymerase chain reaction amplification, we have analyzed 7 retinal angiomas associated with VHL disease for loss of heterozygosity of the VHL gene. In addition, vascular endothelial growth factor expression was evaluated in these tumors by immunohistochemistry and in situ hybridization. RESULTS: All 6 informative retinal angiomas showed loss of heterozygosity of the VHL gene. Loss of heterozygosity was detected in vacuolated "stromal" cells, but not in vascular cells or reactive glial tissue. Vascular endothelial growth factor protein and messenger RNA were also present in vacuolated "stromal" cells. CONCLUSIONS: These findings suggest that vacuolated "stromal" cells represent the true neoplastic component in retinal angioma. These cells express vascular endothelial growth factor and therefore may be responsible for abundant neovascularization of retinal angioma.

Adult↗
PubMed1999

Morphologic and genetic analysis of retinal angioma associated with massive gliosis in a patient with von Hippel-Lindau disease.

We report morphologic and genetic analysis of bilateral retinal angiomas in a 35-year-old patient with von Hippel-Lindau (VHL) disease. Enucleation of both eyes revealed extensive intraocular tumor. Whereas the right eye demonstrated large amounts of retinal angioma tissue, the left eye showed small areas of retinal angioma associated with massive diffuse retinal gliosis. Genetic analysis of the angioma showed allelic deletion of the VHL gene locus, suggesting that the origin of the angiomas was directly related to the patient's underlying VHL disease. Genetic analysis of the pleomorphic glial proliferation showed no allelic VHL gene deletion, which is consistent with the assessment that the glial component represents a reactive process. Apoptosis detected by TUNEL revealed lack of DNA fragmentation in the angioma; in contrast, many positive signals were found in the massive gliosis. We confirmed that the abnormal VHL genes were located in the "stromal" cells of the retinal angioma. Massive gliosis in VHL disease is a true reactive retinal gliosis.

Adult↗
PubMed1999

Microdissection-based analysis of mature ovarian teratoma.

The genotypic features of mature ovarian teratomas (MOTs) are controversial. Early studies detected a homozygous genotype in MOTs suggesting that these tumors are composed of germ cells that have undergone meiosis I. Other studies, however, revealed a heterozygous genotype in a substantial proportion of MOTs suggesting an origin either from premeiotic germ cells or from a somatic cell line. In view of the complex morphology of MOTs and to increase the sensitivity of teratoma genotyping, we applied tissue microdissection before genetic analysis of teratomatous tissue. This approach allowed selective analysis of different heterotopic tissue elements as well as the lymphoid tissues within MOTs the origin of which is unknown. After DNA extraction, the tissue samples were polymerase chain reaction amplified using a random panel of highly informative genetic markers for different chromosomes to evaluate heterozygosity versus homozygosity. In all seven cases that were analyzed, heterotopic tissues consistently revealed a homozygous genotype with several markers; in two cases, heterozygosity was detected with a single marker, indicating a meiotic recombination event. Lymphoid aggregates within MOTs were heterozygous and derived from host tissue rather than from teratomatous growth. However, well differentiated thymic tissue was consistently homozygous, suggesting lymphoid differentiation capability of MOTs. We conclude that potential pitfalls in genotyping of teratomas including meiotic recombination and host cell participation can be avoided by a microdissection-based approach in combination with a panel of genetic markers.

Adolescent↗
PubMed1999

Detection of loss of heterozygosity on chromosome 9q22.3 in microdissected sporadic basal cell carcinoma.

Identification of loss of heterozygosity (LOH) at specific genetic loci in cancer cells suggests the presence of a tumor suppressor gene within the deleted region. A basal cell carcinoma (BCC) susceptibility gene, human homolog of drosophila patched (PTC), has been recently cloned and localized on chromosome 9q22.3. Mutation and deletion of this region has been reported in BCCs using frozen tumor tissue. The objective of this study was to test whether LOH of human PTC on chromosome 9q22 could be detected in archival sporadic BCCs. We studied 20 randomly selected sporadic BCCs by microdissection and polymerase chain reaction using paraffin-embedded, formalin-fixed material on glass slides. In all cases, analysis was performed with the polymorphic markers D9S53, D9S15, D9S287, and D9S303. The LOH frequencies were 30%, 42%, 56%, and 75% with D9S15, D9S287, D9S53, and D9S303, respectively. LOH at 9q22 was identified in 12 of 20 cases (60%) with at least one marker. Seven cases showed LOH with two markers, two cases with three markers, and one case showed LOH with all four markers. The results indicate that BCC LOH can be frequently identified in paraffin-embedded BCC after routine processing.

Aged↗
PubMed1999

Allelic loss of 11q13 as detected by MEN1-FISH is not associated with mutation of the MEN1 gene in lymphoid neoplasms.

Deletions and rearrangements involving the long arm of chromosome 11 are not infrequent occurrences in the non-Hodgkin's lymphomas. Recently, a tumor suppressor gene, the multiple endocrine neoplasia type 1 gene (MEN1) was cloned and mapped to chromosome 11q13. To assess the potential involvement of this gene in lymphomagenesis, we examined 94 primary cases of lymphoma and 12 cell lines by a combination of fluorescent in situ hybridization and PCR-SSCP analysis. In our initial analysis of 41 primary B or T lymphomas, MEN1 FISH analysis revealed allelic deletions in 15 cases (three of four B cell chronic lymphocytic leukemias, six of 15 follicular lymphomas, three of nine diffuse large B cell lymphomas, two of five mantle cell lymphomas, one of four Burkitt's lymphoma). To discern whether the MEN1 gene was in fact the target of the deletions, we assessed 20 of these 41 cases and an additional 74 primary lymphomas and 12 cell lines for MEN1 gene mutations using PCR-SSCP analysis. Abnormal SSCP patterns were found in exon 2 in two of the primary lymphoma cases and in one of the cell lines, but not in any of the original cases that showed MEN1 deletions by FISH. Furthermore, sequencing analysis revealed that the abnormal SSCP patterns in exon 2 were the result of a previously described genetic polymorphism (S145S: AGC --> ACT), and in one sample, the result of this S145S polymorphism associated with a second nucleotide substitution at position 498 which left the encoded amino acid unchanged. Our study indicates that the 11q13 locus is a frequent target of deletion in lymphoid neoplasms, but that there are no associated mutations of the MEN1 gene. This suggests that the 11q deletions either target another gene in lymphomas, or that the MEN1 gene is inactivated through means other than mutation.

Amino Acid Substitution↗
PubMed1999

Mutation analysis of the MEN1 tumour suppressor gene in malignant melanoma.

During the initiation and progression of malignant melanoma a series of genetic events accumulate, including alterations of chromosome 11q. Recently, an important tumour suppressor gene, the multiple endocrine neoplasia type 1 (MEN1) gene, has been mapped on 11q13 and has been cloned. To assess whether the MEN1 region is involved in tumour initiation and progression, we analysed 23 primary cutaneous melanomas and 17 metastases for loss of heterozygosity (LOH) using two informative polymorphic markers closely linked to the MEN1 gene (PYGM and D11S449). To search for mutations within the gene, single-strand conformation polymorphism (SSCP) analysis was performed using 13 primer sets with designed intronic sequences to amplify the MEN1 coding sequence exons 2 to 10. None of the cases showed LOH at the MEN1 gene locus. By SSCP analysis, no aberrant bands were identified on exons 3 to 10. Analysis of exon 2 revealed the presence of aberrant bands in two of the analysed melanomas. Sequencing analysis revealed a genetic polymorphism at S145S (AGC-->ACT) in both sections. None of the cases analysed showed MEN1 gene mutations. This study represents the first genetic analysis of the MEN1 gene in sporadic melanomas. Our data demonstrate no evidence of deletion or mutation of the MEN1 gene in primary or metastatic melanoma. Therefore, MEN1 gene alterations appear not to be associated with tumorigenesis of malignant melanoma. The MEN1 gene appears to be a highly specific tumour suppressor gene only involving tumours within the spectrum of MEN1 disease.

Alleles↗
PubMed1999

BCL-2 expression and inhibin-A in adrenal neoplasms: a comparative study.

Differential diagnosis between adrenal cortical and adrenal medullary lesions may be difficult in many cases. Different immunohistochemical, histochemical tools as well as ultrastructural diagnostic techniques have been employed to aid in differentiating between these lesions. Recently, both inhibin-A and BCL-2 have been shown to stain selectively adrenal cortical tissue and its derived neoplasms but not adrenal medulla or pheochromocytomas. In this study we compared the staining reactions of inhibin-A and BCL-2 in cases of adrenal cortical adenomas and carcinomas as well as pheochromocytomas. We found that both inhibin-A and BCL-2 stained cortical derived tissues, but not medullary derived tissues. Staining intensity for inhibin-A was significantly weaker than for BCL-2. We found that fixation techniques may influence the staining reactivity, as some cases did not immunoreact with any of the antibodies. We conclude that both inhibin-A, and, preferentially, BCL-2 are useful additions to a staining protocol to help in the differential diagnosis of cortical and medullary neoplasms.

Adenoma↗