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U Günthert

Publications and source records attributed to U Günthert.

At least 19 recordsLinked to original sources
PubMed1997

Expression of CD44 isoforms is increased in the airway epithelium of asthmatic subjects.

Since shedding of columnar, but not basal, epithelial cells is common in asthma, cell adhesion molecules such as CD44, which are differentially expressed on these cell types, are likely to be important in this disease. In bronchial epithelium of asthmatic and nonasthmatic subjects, CD44 isoforms have been localized by light- and electron-microscopic immunocytochemistry. Immunoreactivity for total CD44 (mAb Hermes-3/mAb 25.32) and for isoforms containing CD44v9 (mAb 11.24), CD44v6 (mAb 11.9), and CD44v4 (mAb 11.10) have been compared. In nonasthmatic samples, CD44s and CD44v9 were seen on basal but not columnar epithelial cells. Weak CD44v6 immunoreactivity was found infrequently in the bronchus, whereas CD44v4 immunoreactivity was absent. This indicates the presence of a distinct population of basal cells that express CD44. No CD44 was detected in areas of close cell-cell or cell-matrix contact, thus precluding the involvement of CD44 in stable adhesion in these areas. CD44 immunoreactivity was locally increased in areas showing morphologic damage to the epithelium. In epithelium from asthmatic subjects, the mean level of CD44 immunoreactivity on basal-cell membranes was doubled (4.3 versus 2.0 gold particles/microns membrane) as compared with nonasthmatic subjects. Increased expression of CD44 in asthmatic subjects, suggests that it has a significant role in the pathobiology of this disease, whereas the restricted distribution of this increase supports an association with repair rather than with inflammatory processes.

Asthma↗
PubMed1996

Different CD44 splicing patterns define prognostic subgroups in multiple myeloma.

CD44 variant isoforms (CD44v) are generated by alternative splicing of the nuclear RNA resulting in the expression of additional protein domains in the extracellular region of the CD44 standard molecule (CD44s). In multiple myeloma (MM), CD44 mediates binding of tumor cells to stroma and regulates interleukin-6 production. To evaluate the role of CD44v isoforms in MM, CD44v expression was analyzed by immunohistochemical staining of 64 bone marrow biopsies from 38 MM patients. Expression of variant isoforms containing the 9v domain was observed in 36% of cases and was associated with an advanced stage (P < .02; n = 61), a progressive disease (P < .001; n = 61), and a shorter overall survival (P < .02; n = 36). In contrast, 3v, 4v, 6v, or 10v isoforms were detected only in a small percentage of the patients. To analyze the exon composition in RNA-transcripts, reverse transcriptase polymerase chain reaction analyses followed by Southern hybridization with exon-specific probes were performed in fluorescence-activated cell sorted myeloma plasma cells. Tumors expressing the 9v domain showed complex, 9v-containing transcripts in combinations with the 3v, 7v, 8v, and 10v exons. Identical transcripts were detected in several myeloma cell lines and in a Ki-1 B-immunoblastic lymphoma. Similar to high-grade non-Hodgkin's lymphoma and gastric and renal cell carcinoma, overexpression of 9v-containing isoforms in MM is related to an unfavorable clinical presentation and represents a new prognostic parameter.

Adult↗
PubMed1996

CD44 standard and variant isoform expression in human epidermal skin tumors is not correlated with tumor aggressiveness but down-regulated during proliferation and tumor de-differentiation.

CD44 isoforms have been reported to be involved in tumor invasion and metastasis formation. Normal human skin expresses high levels of CD44 isoforms, but little is known about their expression in epidermal skin tumors. Expression of CD44 standard (CD44s) and variant exon (CD44v3, -v4, -v5, -v6, -v9)-encoded gene products has been studied in 74 benign, semi-malignant and malignant human epithelial skin tumors using a panel of well-characterized, variant exon-specific monoclonal antibodies (MAbs). Sensitivity and resolution of the immunohistochemical staining in paraffin sections was substantially improved by using microwave-based antigen retrieval and an optimized streptavidin-biotin-peroxidase technique. Immunostaining was evaluated semi-quantitatively and correlated with tumor type and degree of histological differentiation by non-parametric statistical tests. Furthermore, the relationship between CD44 expression and cellular proliferation rate as defined by the Ki-67 antigen was analyzed in basal cell carcinomas. We found a significant correlation between tumor type and CD44 isoform expression. Basal cell carcinomas exhibited the weakest staining and keratoacanthomas the strongest. Squamous cell carcinomas ranged in between, with a tendency to down-regulate CD44 expression upon de-differentiation. In basal cell carcinomas, an inverse relationship between CD44 expression and proliferation rate was directly demonstrated at the cellular level using double immunolabelling. Our data indicate that qualitative and quantitative changes in CD44 splicevariant expression in human skin tumors do not correlate with invasive and metastatic potential but are rather related to the degree of tumor differentiation.

Animals↗
PubMed1996

The cellular basis of metastasis.

The molecular basis of tumorigenesis and metastasis has been under intense analysis over the last few years. Tumor progression is a multistep process involving the interplay of several molecules. Initiated by spontaneous mutations, cellular alterations occur, which may result in a metastatic phenotype. The transition from a nonmalignant to a malignant cell is governed by mechanisms similar to those implicated in normal cellular differentiation and development. Epithelial cells might lose their polarity and adhesive contacts to become invasive carcinoma cells. Such a complex transformation has been summarized in the term epithelial-mesenchymal transition (EMT). In the analysis of tumor progression it is of particular interest that metastasis-specific gene products are involved in embryonic development and, furthermore, play a role in blood cell migration, tissue remodeling, and wound healing during adulthood. Herein we present a synopsis of the newest developments in molecular biology with respect to tumorigenesis and metastasis in the light of specific molecules involved in EMT.

Animals↗
PubMed1996

CD44 standard and variant isoform expression in normal human skin appendages and epidermis.

CD44 isoforms have been implicated in tumor progression and metastasis formation. This study presents a thorough immunohistochemical analysis of CD44 standard and isoform expression in normal human skin appendages and epidermis applying monoclonal antibodies against CD44s, CD44v3, -v4, -v5, -v6, and -v9. An improved immunohistochemical protocol with microwave-based antigen retrieval in paraffin sections and heavy metal amplification of the diaminobenzidine reaction product provided enhanced resolution and sensitivity as compared to studies on frozen sections. The hair follicle, the seborrheic and eccrine sweat glands were strongly positive for all CD44 isoforms studied. In the latter, the clear cells but not the dark (intercalated) cells were positive. the sudoriferous ducts adjacent to the glands were weakly positive for all CD44 isoforms and strongly positive near the skin surface. In the apocrine glands, the basal cells showed only a moderate positivity. The myoepithelial cells expressed only CD44s. In the epidermis, all CD44 isoforms were detectable, with strongest CD44 immunostaining in the lower third of the stratum spinosum and weaker staining in the stratum basale and the upper two-thirds of the stratum granulosum. The stratum granulosum and corneum were unreactive. Thus, a regional and cell type-specific CD44 expression was revealed.

Antibodies, Monoclonal↗
PubMed1996

Expression of the CD44 variant isoforms 6 and 4/5 in breast cancer. Correlation with established prognostic parameters.

Eighty one invasive breast cancers were analysed immunohistochemically to detect if they expressed the adhesion molecules CD44 v6 and v4/5, and the results were evaluated using the semiquantitative IR-score. The results were further divided into four groups: negative, weak positive, moderate positive and strong positive. Fifteen benign breast tumors were also analysed. Sixty eight breast cancers were CD44v6 and v4/5 positive. T3 and T4 cancers showed statistically significant higher positive CD44 rates than T1 and T2 cancers (P < 0.05). We also found a statistically significant correlation between the estrogen receptor and the CD44 status and between the CD44 status and the cathepsin-D status, whereas no correlation between CD44 and the lymph node status, the M status, the grading of the tumors, the progesterone receptor and the menopausal status could be found. Eleven benign tumors were CD44v6 and v4/5 positive. We could not establish any correlation between the expression of CD44 and the metastasizing capacity of breast cancer.

Breast↗
PubMed1996

Targeted mutation of plakoglobin in mice reveals essential functions of desmosomes in the embryonic heart.

Plakoglobin (gamma-catenin), a member of the armadillo family of proteins, is a constituent of the cytoplasmic plaque of desmosomes as well as of other adhering cell junctions, and is involved in anchorage of cytoskeletal filaments to specific cadherins. We have generated a null mutation of the plakoglobin gene in mice. Homozygous -/- mutant animals die between days 12-16 of embryogenesis due to defects in heart function. Often, heart ventricles burst and blood floods the pericard. This tissue instability correlates with the absence of desmosomes in heart, but not in epithelia organs. Instead, extended adherens junctions are formed in the heart, which contain desmosomal proteins, i.e., desmoplakin. Thus, plakoglobin is an essential component of myocardiac desmosomes and seems to play a crucial role in the sorting out of desmosomal and adherens junction components, and consequently in the architecture of intercalated discs and the stabilization of heart tissue.

Animals↗
PubMed1996

Expression of CD44 isoforms in renal cell tumors. Positive correlation to tumor differentiation.

CD44 isoforms have been implicated in tumor progression and embryogenesis. Primary renal cell tumors (n = 100) of various histopathological differentiation and grading stages were analyzed for expression of CD44 isoforms in comparison with nonmalignant adult and fetal renal tissues. Evaluations were performed by immunohistochemistry using CD44 isoform-specific monoclonal antibodies and by reverse transcriptase polymerase chain reactions (RT-PCR). In the nonmalignant kidney no CD44 variant isoforms were detected. There was a significant increase in expression of CD44 standard (CD44s) and several variant isoforms (CD44v) in the course of tumor differentiation in clear cell carcinomas (n = 68) from stages G1 to G3 (P < 0.0001 for CD44s and isoforms containing CD44-6v, and P < 0.007 for those containing CD44-9v). Also, in chromophilic cell carcinomas (n = 13), CD44 isoform expression correlated with grading; ie, no CD44 expression was detected in G1 tumors, whereas in approximately 50% of the G2 tumors, CD44s, CD44-6v, and CD44-9v isoforms were present. Oncocytomas (n = 8), which are benign renal cell tumors, did not express CD44 isoforms, whereas invasive chromophobe cell carcinomas (n = 11) were positive for CD44s and CD44v isoforms. Transcript analyses by RT-PCR revealed that the upregulated isoforms in the carcinoma cells contained exons 8 to 10 and 3, 8 to 10 in combination from the variant region. In conclusion, expression of variant CD44 isoforms was strongly correlated with grading and appears to mediate a more aggressive phenotype to renal cell tumors.

Adenocarcinoma, Clear Cell↗
PubMed1995

CD44 isoforms correlate with cellular differentiation but not with prognosis in human breast cancer.

CD44 is a transmembrane glycoprotein occurring in several isoforms with different extracellular regions. The various transcripts are encoded by one gene locus containing 20 exons, of which at least 10 can be alternatively spliced in nascent RNA. Isoforms encoded by the variant exons (termed CD44v) are highly restricted in their distribution in nonmalignant tissue as opposed to the standard form of CD44 (CD44s) abundant in many tissues. Specific variant isoforms containing exon 6v have been shown to render nonmetastatic rat tumor cells metastatic. Based on the prominent role in rat metastasis formation, CD44v isoforms were suggested to be involved in human tumor progression. Correlations between prognosis and expression of CD44v have been reported for gastric and colon carcinoma, for non-Hodgkin's lymphoma, and recently for breast carcinoma. We evaluated the expression of CD44 isoforms in node-positive (n = 119) and node-negative (n = 108) cases of breast carcinoma by immunohistochemistry using CD44v exon-specific mAbs. In a subset of 43 cases of high-risk patients, reverse transcription-PCR was used to determine the exon composition of the transcripts. Protein and RNA expression data were probed statistically for their correlation to survival of the patients and clinical risk factors. In contrast to recently published data (M. Kaufmann et al., Lancet, 345: 615-619, 1995), in our cohort disease-free and overall survival data did not indicate significant correlations with the expression of the analyzed isoforms in univariate and multivariate analyses. Comparison of CD44 protein expression with established clinical risk factors for survival such as tumor size (pT1+pT2) and histological grading revealed correlations with the presence of CD44s (P = 0.02 and P = 0.03, respectively) and CD44-9v (P = 0.05 for histological grading). Carcinoma tissues with elevated estrogen and progesterone receptor levels showed positive correlation with CD44-6v (P = 0.001), while a trend for significant coexpression of CD44s and CD44-9v isoforms was observed in estrogen receptor-positive tissues (P = 0.08 and 0.06, respectively). In breast cancer, CD44s, CD44-9v, and CD44-6v are apparently markers for cellular differentiation but not for tumor progression. Our data suggest that steroid hormone receptors may be associated with the in vivo expression of CD44-6v-containing isoforms in human mammary carcinoma.

Adult↗
PubMed1995

CD44 variant isoforms in non-Hodgkin's lymphoma: a new independent prognostic factor.

Isoforms of the transmembrane glycoprotein CD44, generated by alternative RNA splicing, have been correlated to tumor dissemination. For evaluation of the potential role of CD44 variant isoforms in non-Hodgkin's lymphoma (NHL), the presence of CD44 isoforms was analyzed in a large panel of reactive and neoplastic lymphoid tissues by immunohistochemical staining, as well as detection of CD44 variant RNAs by the reverse transcriptase-polymerase chain reaction. Whereas the CD44 standard or hematopoietic isoform (CD44s), devoid of the variant regions, was expressed in all leukocyte subpopulations, the variant isoforms (CD44v) showed a highly restricted pattern of expression, mainly observed in epithelial layers of lymphoid tissues and subpopulations of leukocytes after stimulation. In addition to a strong expression of CD44s, variant isoforms containing CD44-6v in combination with other variant exons were observed predominantly in aggressive lymphoma and were associated with a shorter overall survival of patients (n = 138; P < .0001). Moreover, multivariate analysis indicated CD44-6v as a new independent prognostic parameter in high grade NHL in comparison with the risk groups defined by the International NHL Lymphoma Prognostic Factors Project (N Engl J Med 329:987, 1993).

Adolescent↗
PubMed1995

CD44 isoforms during differentiation and development.

During mouse early development cell adhesion molecules are indispensable for the embryo organisation. A family of molecules probably involved in development is the transmembrane glycoprotein CD44 family, which exists in multiple isoforms. These are generated by alternative splicing of the pre-mRNA, resulting in the enlargement of the extracellular part of the molecule. The standard form of CD44 is widely expressed in adult tissues and in embryos from day 9.5 post coitum onwards, while the numerous variant isoforms exhibit highly specialised patterns of expression that are already in the egg cylinder at day 6.5 of development. In lymphohemopoiesis, specific variant isoforms also emerge at decisive differentiation stages. Although specific ligands for the variant region still await isolation, the highly organised expression of CD44 variant isoforms suggests they have a pivotal role in cellular interactions during early development, pattern formation and hemopoiesis.

Alternative Splicing↗
PubMed1995

Irreversible repression of DNA synthesis in Fanconi anemia cells is alleviated by the product of a novel cyclin-related gene.

Primary fibroblasts from patients with the genetic disease Fanconi anemia, which are hypersensitive to cross-linking agents, were used to screen a cDNA library for sequences involved in their abnormal cellular response to a cross-linking challenge. By using library partition and microinjection of in vitro-transcribed RNA, a cDNA clone, pSPHAR (S-phase response), which is able to correct the permanent repression of semiconservative DNA synthesis rates characteristic of these cells, was isolated. Wild-type SPHAR mRNA is expressed in all fibroblasts so far analyzed, including those of Fanconi anemia patients. Correction of the abnormal response in these cells appears therefore to be due to overexpression after cDNA transfer rather than to genetic complementation. The cDNA contains an open reading frame coding for a polypeptide of 7.5 kDa. Rabbit antiserum directed against a SPHAR peptide detects a protein of 7.9 kDa in Western blots (immunoblots) of whole-cell extracts from proliferating, but not resting, fibroblasts. The deduced amino acid sequence of SPHAR contains a motif found in the cyclins, and it is proposed that SPHAR acts within the injected cell by interfering with the cyclin-controlled maintenance of S phase. In agreement with this proposal, normal cells transfected with an antisense SPHAR expression vector have a significantly reduced rate of DNA synthesis during S phase and a prolonged G2 phase, reflecting the need for postreplicative DNA processing before entry into mitosis.

Amino Acid Sequence↗
PubMed1995

Distinct expression patterns of CD44 isoforms during human lung development and in pulmonary fibrosis.

The transmembrane glycoprotein CD44 represents a family of molecules, all encoded by one gene. The variability of the isoforms is generated by alternative splicing of the nuclear RNA. Apart from the abundant standard form (CD44s), the variant isoforms (CD44v) are mostly restricted to epithelia. The present study demonstrates the expression of CD44s and CD44v isoforms in embryonic and fetal lungs and in normal and pathologically altered (pulmonary fibrosis after radio- or chemotherapy) human adult pulmonary tissues. Using double immunofluorescence and avidin biotin complex (ABC) techniques on paraffin sections, presence of CD44s and CD44v isoforms (CD44v4, CD44v6, CD44v9) has been analyzed. In normal lung tissue, CD44s is present at the cell surface of alveolar macrophages, in some interstitial cells and in epithelial cells. It is also present in epithelial and non-epithelial cells during lung development. CD44v isoforms containing exon v6 and v9 encoded epitopes are selectively detectable in normal epithelial cells with a strong basolateral distribution pattern in the entire population of type II pneumocytes and in basal cells of the bronchial epithelium. During development exon v9 encoded isoforms appear at the pseudoglandular stage, whereas CD44v6 has only been found at the saccular stage. Examination of 12 fibrotic lung samples has revealed major alterations in the CD44 expression in comparison to normal lung tissue. These changes include cytoplasmic deposits of CD44s in alveolar epithelial cells and reduced expression of the CD44v6 and CD44v9 isoforms in alveolar epithelial and bronchial epithelial cells. The results suggest that CD44v isoforms may be utilized by type II pneumocytes in epithelial-mesenchymal interactions and in the maintenance of the pulmonary histoarchitecture.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗