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Ulrich Lehmann

Publications and source records attributed to Ulrich Lehmann.

30 records · Page 2Linked to original sources
PubMed2004

Tubular chimerism occurs regularly in renal allografts and is not correlated to outcome.

Recent studies have demonstrated an integration of recipient-derived progenitor cells into solid allografts with differentiation into parenchymal cells. Whether or to what extent this phenomenon influences allograft outcome has still to be elucidated. To detect epithelial chimerism tubular cells were harvested from sequential renal allograft biopsy samples by laser microdissection in 36 patients. Recipient-derived cells were detected by short-tandem repeat-based genotyping. In cases with gender-mismatched transplantation, chimerism was semiquantitatively evaluated by in situ hybridization for the Y-chromosome. Findings were correlated to different pathomechanisms of epithelial injury as well as to morphologic and clinical outcome. Epithelial chimerism was detectable as early as 8 d after transplantation and lasted for 8 yr. A total of 88% of the patients showed an epithelial chimerism; 72% had a stable chimerism in sequential biopsy samples. Evaluation of Y-chromosome by in situ hybridization revealed low percentages of chimerical tubular epithelial cells (2.4% to 6.6%). No correlation to morphology was found. Chimerism was detectable in inconspicuous protocol biopsy samples, cases of drug toxicity, and rejected allografts with and without chronic changes. No correlation was found to allograft function. Epithelial microchimerism is an early and persistent phenomenon after renal transplantation. There is no correlation to morphologic or functional outcome. Probably recipient-derived stem cells contribute in a minor fashion to tissue homeostasis, and cell turnover in renal allografts is predominantly enabled by donor cell renewal.

Biopsy↗
PubMed2004

Real-time PCR-based assay for quantitative determination of methylation status.

The best studied epigenetic modification in mammals is the methylation of cytosine. During the development and progression of malignant neoplasia, a global hypomethylation is often accompanied by a locus-specific increase in methylation. Also, during normal development specific alterations in DNA methylation patterns take place. In recent years it has become clear that in many situations only quantitative changes in methylation levels occur and that the pure qualitative detection of cytosine methylation misses important biological and pathophysiological information. Therefore, several protocols were developed for the quantitative detection of cytosine methylation. Here, we describe a real-time polymerase chain reaction-based assay for the sensitive and precise quantification of methylated and unmethylated alleles after bisulfite treatment of genomic DNA. In addition to providing quantitative methylation data, this methodology is suitable for high-throughput analysis.

Animals↗
PubMed2003

Role of epigenetic changes in hematological malignancies.

Inactivation of tumor suppressor genes is an important event contributing to the development of neoplasia. In addition to the classic genetic mechanisms of deletion or inactivating point mutations, growth regulatory genes can be functionally inactivated without alterations of the primary sequence by methylation of cytosine residues in the promoter regions of the genes. After introducing epigenetic phenomena in general and the molecular basis of DNA methylation in more detail, this review will present the broad spectrum of alterations in DNA methylation patterns found in hematopoietic malignancies. In addition, the implications for therapy and prognosis will be discussed.

Animals↗
PubMed2003

Increased chimerism of bronchial and alveolar epithelium in human lung allografts undergoing chronic injury.

Chimerism on the parenchymal level has been shown for several human allografts, including liver, heart, and kidney, with the integrated recipient-derived cells most likely originating from multipotent bone marrow precursors. We investigated whether chimerism also occurs within epithelial structures of the lung. For this purpose archival tissue biopsies from seven explanted human lung allografts were obtained. We performed laser microdissection of the target structures with subsequent short tandem repeat analysis to detect chimerism within the isolated cells. We found integration of recipient-derived cells in the bronchial epithelium, in type II pneumocytes and in seromucous glands lying adjacent to larger bronchi in all lung allografts studied. Quantitative analysis revealed that the epithelial structures displaying signs of chronic injury, such as squamous metaplasia, showed a markedly higher degree of chimerism (24% versus 9.5%). We therefore conclude that in human lungs, epithelial chimerism occurs at least within bronchi, type II pneumocytes, and seromucous peribronchial glands. Although a bone marrow origin of immigrating host-derived stem cells has been suggested by previous studies in rodents, analysis of lung biopsies from bone marrow-transplanted patients (n = 3) could not prove such delineation in this study. The observation of an enhanced integration of recipient cells into chronically damaged epithelial structures suggests that extrapulmonary precursor cells are able to contribute to pulmonary regeneration.

Adolescent↗
PubMed2003

Quantitative intra-individual monitoring of BCR-ABL transcript levels in archival bone marrow trephines of patients with chronic myeloid leukemia.

We established a quantitative real-time RT-PCR assay for the detection of chimeric BCR-ABL transcripts in archival formalin-fixed bone marrow trephines, both acrylate-embedded and paraffin-embedded. This new methodology enables determination of transcript levels in direct comparison to histopathological findings and therapeutic interventions during the time course of the disease in a retrospective and a prospective manner. We found an excellent correlation between the quantitative molecular data and the morphological evaluation as well as the clinical outcome for a cohort of chronic myeloid leukemia patients (n = 10). To the best of our knowledge, this is the first study demonstrating the feasibility of large-scale quantitative expression analysis in archival bone marrow trephines for monitoring molecular markers over several years or even decades.

Base Sequence↗
PubMed2003

Expression profiling of breast cancer cells by differential peptide display.

Expression profiling of RNAs or proteins has become a promising means to investigate the heterogeneity of histopathologically defined classes of cancer. Peptides, representing degradation as well as processing products of proteins offer an even closer insight into cell physiology. Peptides are related to the turnover of cellular proteins and are capable to reflect disease-related changes in homoeostasis of the human body. Furthermore, peptides derived from tumor cells are potentially useful markers in the early detection of cancer. In this study, we introduced a method called differential peptide display (DPD) for separating, detecting, and identifying native peptides derived from whole cell extracts. This method is a highly standardized procedure, combining the power of reversed-phase chromatography with mass spectrometry. This technology is suitable to analyze cell lines, various tissue types and human body fluids. Peptide-based profiling of normal human mammary epithelial cells (HMEC) and the breast cancer cell line MCF-7 revealed complex peptide patterns comprising of up to 2300 peptides. Most of these peptides were common to both cell lines whereas about 8% differed in their abundance. Several of the differentially expressed peptides were identified as fragments of known proteins such as intermediate filament proteins, thymosins or Cathepsin D. Comparing cell lines with native tumors, overlapping peptide patterns were found between HMEC and a phylloides tumor (CP) on the one hand and MCF-7 cells and tissue from a invasive ductal carcinoma (DC) on the other hand.

Biomarkers, Tumor↗
PubMed2002

Promoter hypermethylation of the death-associated protein kinase gene in breast cancer is associated with the invasive lobular subtype.

Expression of death-associated protein (DAP) kinase, a proapoptotic serine/threonine protein kinase, is frequently lost in human tumors. In a study of 134 primary breast cancer specimens hypermethylation of the DAP kinase gene was found in 13% of cases. A highly significant difference (P < 0.001) of DAP kinase inactivation was observed between invasive lobular cancer (n = 19) and invasive ductal cancer (n = 85; 53% versus 9%, respectively). Hypermethylation correlated with loss of RNA expression, estrogen receptor positivity (P < 0.01), and the absence of p53 overexpression (P < 0.01). In contrast to invasive lobular cancer, the in situ-growing precursor lesion lacked epigenetic modification of the DAP kinase promotor by aberrant methylation indicating a potential role in tumor progression. Unlike the DAP kinase gene, hypermethylation of the cyclin D2 and RASSF1A genes did not correlate with a particular histological subtype or to invasiveness [corrected]. We conclude that different histological subtypes of breast cancer may not only differ concerning specific chromosomal abnormalities and DNA mutations but also with regard to epigenetic inactivation patterns.

Apoptosis Regulatory Proteins↗
PubMed2002

Quantitative assessment of promoter hypermethylation during breast cancer development.

The aberrant methylation of cytosine residues in the promoter region of growth regulatory genes is now widely recognized as an additional mechanism for gene inactivation in cancer cells. In this study we analyzed the methylation status of four growth regulatory genes (p16, RASSF1A, cyclinD2, 14-3-3zeta) during breast cancer progression. For this purpose invasive and noninvasive tumor cell populations as well as hyperplastic cell proliferations were isolated from a series of archival breast tissue specimens (n = 57) using laser-assisted microdissection. A new real-time polymerase chain reaction-based assay was used for the sensitive and quantitative determination of the cell-specific methylation status. We found that aberrant promoter methylation was already prevalent in pure intraductal carcinoma with different frequencies and different methylation levels for the four genes analyzed. For RASSF1A and 14-3-3zeta promoter methylation was also demonstrated in epithelial hyperplasia and intraductal papillomas. By contrast, aberrant methylation of cyclinD2 and p16 was restricted to cancerous epithelium. Increased methylation of the cyclinD2 gene was significantly associated with a higher van Nuys grade. Furthermore, when intraductal and invasive tumor cells were compared, significant quantitative changes in the methylation level were detected primarily within the cyclinD2 gene. These results demonstrate that promoter methylation is an early and frequent event in breast cancer development, but displays great quantitative and gene-specific differences, and changes in a gene-specific manner during tumor progression.

14-3-3 Proteins↗
PubMed2002

Reliability of lymphoma classification in bone marrow trephines.

The aim of this study was to test and establish the accuracy and reliability of lymphoma classification in bone marrow trephines according to the new World Health Organization (WHO) classification by considering predominantly the morphology and immunophenotype. Therefore, we retrospectively compared lymphoma diagnoses, rendered exclusively on bone marrow trephines without knowledge of lymph node diagnosis in 124 patients, with the results of the reference centres that had reviewed lymph node (n = 90) or extranodal biopsies (n = 34). The overall concordance rate was higher than 85% and 91%, respectively, when patients with discordant malignancy grades were excluded. The concordance rate for low-grade B-cell lymphomas was 93% and for high-grade B-cell lymphomas 84%. The main reasons for discordant diagnoses were divergent immunophenotypes among low-grade B-cell lymphomas (6 out of 81, i.e. 7.4%) and discrepant malignancy grades within high-grade B-cell lymphomas (6 out of 31, i.e. 19.4%). No relationship between discordant diagnoses and chemotherapy given during the course of the disease with the site of biopsy (i.e. lymph nodes, extranodal sites) was noted. We conclude from our results that bone marrow trephines are a reliable tool, not only for establishing bone marrow infiltration, but also for the subtyping of lymphomas.

Biopsy↗
PubMed2002

High frequency of epithelial chimerism in liver transplants demonstrated by microdissection and STR-analysis.

It has recently been shown that epithelial cells derived from stem cells originating outside the liver are integrated into liver allografts. Whether epithelial intragraft chimerism protects transplants from rejection or chronic transplant dysfunction, and whether it interferes with recurrence of primary liver disease, is not known. Twenty-seven sequential biopsies derived from 9 liver-transplant recipients were studied for chimerism of hepatocytes and cholangiocytes. The target cells were isolated by laser microdissection after cytokeratin immunolabeling and genotyped using DNA analysis of a highly polymorphic short tandem repeat. Irrespective of whether early (up to 4 weeks) or late (more than 12 months) posttransplantation biopsies were studied, cholangiocyte chimerism was almost constantly found in 91% of the samples. No significant differences occurred between samples derived from patients with chronic organ dysfunction (n = 3), recurrent hepatitis (n = 3), or mild, unspecific changes (n = 3). By contrast, hepatocyte chimerism tended to occur later (55% vs. 22%) and appeared to be associated with recurrent hepatitis (67% vs. 27%). In this respect, chronic organ dysfunction did not differ from mild, unspecific changes. While cholangiocyte chimerism represents a constant and early phenomenon in liver transplantations, an enhanced chimeric integration of recipient-derived hepatocytes can be observed in recurrent hepatitis, supporting the concept of an increased recruitment of extrahepatic progenitor cells to the liver in chronic hepatitis.

Bile Ducts↗
PubMed2002

Marked intratumoral heterogeneity of c-myc and cyclinD1 but not of c-erbB2 amplification in breast cancer.

Intratumoral heterogeneity mirrors subclonal diversity and might affect treatment response. To investigate molecular heterogeneity of primary breast cancer specimens, we determined the amplification status of growth regulatory genes (c-erbB2, topoisomerase IIalpha, c-myc, and cyclinD1) in macroscopically and microscopically separate areas of individual tumors (n = 21). Using laser-assisted microdissection and quantitative PCR, we found marked intratumoral heterogeneity with different patterns for each gene. Molecular heterogeneity in amplification pattern could be demonstrated between both macroscopically (0.5 to several centimeters) and microscopically (10 to several hundred micrometers) distant tumor areas. C-erbB2 amplification proved to be the most stable amplification in individual tumors, with heterogeneity occurring in only 36% of amplified cases. By contrast, amplification of c-myc and cyclinD1 revealed varying patterns in the vast majority of amplified cases (100% and 83%). The constancy of c-erbB2 amplification underlines its presumed importance in breast cancer biology. We conclude that the molecular heterogeneity of breast cancer as evidenced in this study requires thorough and representative sampling of different tumor areas when the biologic significance of somatic mutations is considered. Patterns of heterogeneity can be used to trace the clonal evolution within different compartments of an individual tumor.

Breast Neoplasms↗