PubMed Health⌕ Search

Biomedical subjects

F Gebhardt

Publications and source records attributed to F Gebhardt.

13 recordsLinked to original sources
PubMed2000

Length and loss of heterozygosity of an intron 1 polymorphic sequence of egfr is related to cytogenetic alterations and epithelial growth factor receptor expression.

Overexpression of epithelial growth factor receptor (EGFR) is correlated with a poor prognosis and reduced steroid receptor expression. Recently, it was demonstrated that the length of a CA repeat in the intron 1 of EGFR correlated with the expression of EGFR in vitro. We investigated 112 cases of cancerous and noncancerous breast tumor samples for loss of heterozygosity (LOH) in intron 1 of the egfr gene and determined the intratumoral EGFR content and genetic alterations by comparative genomic hybridization. Heterozygous tumors with short CA repeats showed elevated EGFR expression in contrast to tumors with longer CA repeats. Tumors with LOH in intron 1 of egfr revealed higher EGFR expression when the longer allele was lost compared with loss of the shorter allele. Additionally, tumors with a loss of the long allele showed more chromosomal alterations, especially a higher frequency of amplifications. We conclude that the CA repeat status in intron 1 of the egfr gene also modulates the intratumoral EGFR content in vivo. Furthermore, LOH at the CA repeat is associated with genetically advanced tumors. Therefore, allele-specific gene expression due to LOH of the CA repeat could be assumed to be an important event in invasive breast cancer development.

Alleles↗
PubMed2000

Modulation of EGFR gene transcription by secondary structures, a polymorphic repetitive sequence and mutations--a link between genetics and epigenetics.

The epidermal growth factor receptor (EGFR) plays a crucial role in growth, differentiation and motility of normal as well as tumor cells. The transduction of extracellular signals to the cytoplasm via the receptor not only depends on ligand binding, but is also determined by the receptor density on the cell surface. Therefore, in terms of cancer diagnosis and therapeutic approaches targeting EGFR it is decisive to know how the expression level of EGFR is controlled. We found that transcription activity declines with increasing numbers of CA dinucleotides of a highly polymorphic CA repeat in the first intron epidermal growth factor receptor gene. In vivo data from cultured cell lines support these findings, although other regulation mechanisms can compensate this effect. In addition, we showed that RNA elongation terminates at a site closely downstream of the simple sequence repeat (SSR) and that there are two separate major transcription start sites. Model calculations for the helical DNA conformation revealed a high bendability in the EGFR polymorphic region, especially if the CA stretch is extended. These data suggest that the CA-SSR can act like a joint bringing the promoter in proximity to a putative repressor protein bound downstream of the CA-SSR. The data suggest that this polymorphism is a marker for cancer linking genetic and epigenetic risk. Furthermore in breast cancer, heterozygous tumours with short CA-SSR showed an elevated EGFR-expression in contrast to tumours with longer CA-SSR. Tumours with loss of heterozygosity in intron 1 of egfr revealed an increased EGFR expression if the longer allele was lost. Moreover, deceased egfr gene dosages were significantly correlated to poor prognosis in breast cancer.

Animals↗
PubMed1999

Modulation of epidermal growth factor receptor gene transcription by a polymorphic dinucleotide repeat in intron 1.

The influence of a highly polymorphic CA dinucleotide repeat in the epidermal growth factor receptor (EGFR) gene on transcription was examined with a quantitative nuclear run-off method. We could demonstrate that transcription of the EGFR gene is inhibited by approximately 80% in alleles with 21 CA repeats. In experiments with polymerase chain reaction products that spanned a region of more than 4,000 base pairs and contained the promoter, two enhancers, and the polymorphic region in the first intron of the gene, we found that transcription activity declines with increasing numbers of CA dinucleotides. In vivo pre-mRNA expression data from cultured cell lines support these findings, although other regulation mechanisms can outweigh this effect. In addition, we showed that under our experimental conditions RNA elongation terminates at a site closely downstream of the simple sequence repeat and that there are two separate major transcription start sites. Our results provide new insights in individually different EGFR gene expression and the role of the CA repeat in transcription of this proto-oncogene.

Base Sequence↗
PubMed1998

Differential expression of alternatively spliced c-erbB-2 mRNA in primary tumors, lymph node metastases, and bone marrow micrometastases from breast cancer patients.

We established an RT-PCR method to measure the amount of a 2.3-kb alternatively spliced mRNA of the human c-erbB-2/HER-2 proto-oncogene relative to the 4.6-kb full-length transcript. For the first time, we demonstrated production of c-erbB-2 extracellular domains via alternative splicing in breast cancer tissues, lymph node and bone marrow micrometastases. In 15 c-erbB-2-positive primary breast tumor samples, we found two significantly distinct subgroups: 6/15 had a low level of the extracellular fragment, and 9/15 showed an average 4.4-fold higher amount of the alternatively spliced mRNA. Additionally, six lymph nodes and six bone marrow aspirates from metastatic breast cancer patients were analyzed: 5/6 lymph nodes and 6/6 bone marrow aspirates were found to produce elevated relative amounts of the truncated fragment. The results demonstrate that our method is suitable for sensitive detection of c-erbB-2-positive micrometastasis and strongly suggest that the alternatively spliced c-erbB-2 variant is involved in the development of micrometastasis in breast cancer.

Alternative Splicing↗
PubMed1998

Direct quantification of polymerase chain reaction fragments using field-amplified sample injection in capillary zone electrophoresis for gene dosage estimation.

To assess gene dosages for clinical application, especially for prognostication of cancer, we developed a direct quantification method for polymerase chain reaction products. We report on an application of field amplified sample injection (FASI) to capillary zone electrophoresis which allows the quantification of PCR products without sample preparation. Using an external standard and UV detection for the quantification of DNA, a low coefficient of variation has been obtained. Overall, the described method provides a fast and easy tool for PCR product quantification in clinical laboratories.

DNA↗
PubMed1997

Translational research studies of erbB oncogenes: selection strategies for breast cancer treatment.

Specific gene families, e.g. encoding members of signal transduction pathways, show a gene dosage sensitivity. We report on the determination of the gene dosages of egfr and c-erbB-2 in relation to the intratumoral concentration of the tyrosine kinase receptor protein EGFR and p185c-erbB-2 and the clinical outcome of breast cancer patients in a retrospective study. Prognostic unfavorable subgroups were determined in a life-table analysis by (a) an average gene copy number of egfr of less than 0.4 and greater than 1.6 and an intratumoral EGFR concentration of more than 56 fmol/mg, (b) an intratumoral p185c-erbB-2 concentration above 26 HNU/mg and (c) a quotient of egfr and c-erbB-2 average gene copy numbers of less than 0.15 and greater than 4.35.

Breast Neoplasms↗
PubMed1981

The frozen-section autopsy.

A protocol for the rapid completion of autopsies using frozen sections was studied. The protocol was tested on 50 autopsy subjects, and the results compared with those from the standard autopsy protocol used on the same 50 cases. Cost, speed with which the reports could be completed, teaching value, and accuracy were compared; autopsy completed by frozen sections was superior in all four areas. There were 47 errors, none of which involved major disease processes. All but nine were errors of sampling and could be remedied by the more liberal sampling of tissues and the occasional supplementation with paraffin sections. The frozen-section autopsy protocol can replace the standard autopsy protocol in most cases. The rapid completion of the autopsy invites participation of the clinician and stimulates cooperation that benefits both the clinician and the pathologist.

Autopsy↗
PubMedDate not supplied

Modulation of EGFR gene transcription by a polymorphic repetitive sequence--a link between genetics and epigenetics.

The epidermal growth factor receptor (EGFR) plays a crucial role in growth, differentiation and motility of normal as well as tumor cells. The transduction of extracellular signals to the cytoplasm via the receptor not only depends on ligand binding, but is also determined by the receptor density on the cell surface. Therefore, with regard to cancer diagnosis and therapeutic approaches targeting EGFR it is important to know how the expression level of EGFR is controlled. We found that transcription activity declines with increasing numbers of CA dinucleotides of a highly polymorphic CA repeat in the first intron of the epidermal growth factor receptor gene. In vivo data from cultured cell lines support these findings, although other regulation mechanisms can compensate this effect. In addition, we showed that RNA elongation terminates at a site closely downstream of the simple sequence repeat (SSR) and that there are two separate major transcription start sites. Model calculations for the helical DNA conformation revealed a high bendability in the EGFR polymorphic region, especially if the CA stretch is extended. These data suggest that the CA-SSR can act like a joint, bringing the promoter in proximity to a putative repressor protein bound downstream of the CA-SSR. The data indicate that this polymorphism may be a marker for cancer, linking genetic and epigenetic risk factors. Furthermore, in breast cancer, heterozygous tumors with short CA-SSR showed an elevated EGFR-expression in contrast to tumours with longer CA-SSR. Tumours with loss of heterozygosity in intron 1 of egfr revealed an increased EGFR expression if the longer allele was lost. Moreover, decreased EGFR gene levels were significantly correlated with poor prognosis in breast cancer.

Biomarkers, Tumor↗