Search PubMed⌕ Search

Biomedical subjects

U Günthert

Publications and source records attributed to U Günthert.

At least 19 recordsLinked to original sources
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↗
PubMed1995

Are CD44 variant isoforms involved in human tumour progression?

The transmembrane glycoprotein CD44 exists in a variety of isoforms generated by alternative splicing of the pre-mRNA. In a rat metastasis model, certain variant isoforms (containing exon 6v) are causally involved in lung metastasis formation. We have summarized the data obtained to date on the expression of CD44 variant isoforms in human tumour progression. In non-Hodgkin lymphomas, expression of exon 6v containing isoforms is an independent prognostic factor indicating an adverse prognosis. Upregulation of exon 9v containing isoforms in gastric and renal cell carcinomas relates to a poor prognosis of patients. In colorectal carcinomas, CD44-9v isoforms are strongly expressed already in early adenomas; CD44-6v isoforms are upregulated in late adenomas along with ras and TP53 mutations. No expression of variant isoforms has been detectable in neuroblastomas, but significant downregulation of CD44s correlates inversely with tumour progression and N-myc amplification. Only in breast carcinoma has no correlation of CD44 expression with survival or any other prognostic marker been established. Evaluation of CD44 isoform expression by immunohistochemistry in cases of non-Hodgkin lymphoma, gastric, colon and renal cell carcinomas, as well as neuroblastomas, may be a useful diagnostic parameter indicating invasive processes.

Breast Neoplasms↗
PubMed1995

[Expression of CD44 isoforms in normal human liver and also in regenerative and neoplastic liver changes].

CD44 is a transmembrane glycoprotein of which a large number of isoforms exist. There is evidence, mostly from experimental systems, that isoforms of CD44 generated by alternative splicing of ten variant exons are involved in tumor invasion and metastasis formation. We have evaluated the expression of CD44 standard (CD44s) and variant exons (CD44v) encoded gene products in formalin-fixed and paraffin-embedded human liver specimens, using an immunohistochemical protocol with microwave-based antigen-retrieval and signal amplification. Tissue sections from normal, regenerative and neoplastic liver were studied. Our results indicate that: 1. in normal liver, both, hepatocytes and bile duct epithelia lacked detectable CD44s and CD44v containing isoforms; 2. most cirrhotic liver specimens were unreactive. Some regenerative nodules showed a focal weak positivity for CD44v5 and v9. Most proliferating bile ductules were weakly stained for CD44v9 and some of them also for v5 and v6; 3. most hepatocellular carcinomas displayed a heterogeneous staining of varying intensity for CD44v5, v6, v9 and CD44s. In a few tumors a weak staining for CD44v3 and v4 was also present. Furthermore, there was a tendency to an increased staining intensity of CD44 isoforms with decreasing differentiation; 4. cholangiocarcinomas showed a high expression of CD44s, v3, v5, v6 and v9 containing isoforms. We conclude that neoplastic transformation of hepatocytes and bile duct epithelia is associated with qualitative and quantitative changes in the expression of some CD44 variant exons encoded products. The clinical implications of these findings remain to be determined in a large series of patients.

Adenoma↗
PubMed1994

Expression of integrins and CD44 isoforms in non-Hodgkin's lymphomas: CD44 variant isoforms are preferentially expressed in high-grade malignant lymphomas.

Low- and high-grade malignant non-Hodgkin's lymphomas have been investigated by immunohistochemistry for their expression of various integrins and CD44 isoforms. Comparison with the expression patterns obtained in non-malignant adult lymph nodes revealed the following differences: alpha 6 and beta 4 integrins were expressed in several high-grade malignant lymphomas to a lower degree than in both the low-grade malignant lymphomas and the normal lymph nodes; all other integrins (alpha 2, alpha 4, alpha 5, alpha v, beta 1, beta 2, beta 3, and beta 7) did not exhibit significant differences in the expression levels between malignant and non-malignant tissues. The standard isoform of CD44 (CD44s) was highly expressed in all lymphoid tissues. Using CD44 exons-specific monoclonal antibodies, CD44 variant isoforms were not detected in non-malignant lymph nodes and were detected only rarely in low-grade malignant lymphomas. In contrast, high-grade malignant lymphomas expressed several CD44 variant isoforms, which included the products from the variant exons 3v, 6v, and 9v, but not 4v. Specifically, detection of exon 3v and 6v products indicates a more aggressive phenotype.

Adult↗
PubMed1994

CD44 variant isoforms are preferentially expressed in basal epithelial of non-malignant human fetal and adult tissues.

CD44 is a transmembrane glycoprotein, which can exist in a multitude of isoforms due to alternative splicing of the pre-mRNA. We have generated monoclonal antibodies to several of these variant regions, which are encoded by 10 additional exons in the extracellular part of the molecule. CD44 variant isoforms have been reported to be involved in the malignant progression of rat and human tumours. The precise localization of CD44 variant isoforms in normal developmental and morphogenetic processes is essential for diagnostic studies of human tumorigenesis. Therefore, we have analysed a large number of different human tissues by immunohistochemistry for the expression of CD44 isoforms containing either exons 4v, 6v or 9v. Expression of exon 9v-isoforms was detected in almost all epithelia analysed, with a few exceptions. Exon 6v isoforms are expressed only in squamous and glandular epithelial, e.g. skin epidermis, sweat and sebaceous glands, oesophagus, ducts of the mammary gland, salivary and prostate glands. Detection of exon 4v-encoded isoforms was restricted to the epidermis and the oesophagus. Similar tissue distributions of CD44 variant isoforms were observed in 10-week-old fetal tissues. Since one of the ligands of CD44 is hyaluronic acid (HA), we also analysed the tissue distribution of HA synthetase. HA synthetase was detected in all tissues analysed, showing good correlation with the expression of the standard form of CD44, CD44s.

Adult↗
PubMed1994

Expression and modulation of CD44 variant isoforms in humans.

CD44 is a ubiquitous surface molecule that exists as a number of isoforms, generated by alternative splicing of 10 "variant" exons. Little is known about the expression and function of the variant isoforms, except that certain isoforms may play a role in cancer metastasis. We produced mAbs against CD44 variant regions encoded by exons 4v, 6v, and 9v, by immunizing mice with a fusion protein spanning variant exons 3v to 10v. A comprehensive analysis of human tissues revealed that CD44 variant isoforms were expressed widely throughout the body, principally by epithelial cells. However there was differential expression of CD44 variant exons by different epithelia. Most epithelia expressed exon 9v, but much fewer expressed 6v or 4v. The regions of epithelia that expressed the highest levels of the variant isoforms were the generative cells, particularly the basal cells of stratified squamous epithelium, and of glandular epithelium. CD44 variant isoforms were also expressed differentially by leukocytes, with CD44-9v expressed at very low levels and CD44-6v and 4v virtually absent. However, CD44-9v and CD44-6v were the main variants that were transiently upregulated on T cells after mitogenic stimulation and on myelomonocytic cell lines by TNF alpha and IFN gamma treatment. Some epithelial cell lines could preferentially upregulate CD44-6v upon IFN gamma incubation. These results show that CD44 variant isoforms are expressed much more widely than first appreciated, and that expression of the variant isoforms on some cell types can be modulated by particular cytokines.

Amino Acid Sequence↗
PubMed1993

De-novo expression of CD44 and survival in gastric cancer.

We have examined the cell surface molecule CD44, which is attracting interest because of reports that isoforms are associated with metastasis. The prognostic value of CD44 expression has yet to be assessed for a solid tumour. Benign (59) and malignant (primary 61, metastatic 59) gastric tissues were examined with antibodies directed at epitopes common to known CD44 isoforms. Normal mucosa was CD44 negative. In atrophic gastritis and intestinal metaplasia expression was restricted to the epithelial cells of the basal glands and was positively correlated with an increased leucocyte infiltrate and with the expression of HLA DR by mucosal cells. These observations suggest a role for chronic inflammation in the induction of CD44 expression on benign mucosa. No such association was observed between inflammatory infiltrate and CD44 expression on gastric tumours. CD44 expression, observed in only 49% of primary tumours, was associated with distant metastases at time of diagnosis and, among 31 curatively resected patients, with tumour recurrence (p = 0.0014) and increased mortality (p = 0.001) during follow-up averaging 17 months. When we used an antibody directed against the CD44 variant exon 9v, we found a good correlation between the expression of total CD44 and of exon 9v containing isoforms, and 9v expression in primary tumours was significantly and positively associated with tumour recurrence and mortality.

Adenocarcinoma↗
PubMed1993

A link between ras and metastatic behavior of tumor cells: ras induces CD44 promoter activity and leads to low-level expression of metastasis-specific variants of CD44 in CREF cells.

The activated oncogene c-Ha-ras induces expression of the surface glycoprotein CD44 in cloned rat embryonic fibroblasts (CREF). Induction is transcriptional as shown by transient cotransfections of c-Ha-ras expression constructs and CD44 promoter reporter gene constructs and depends on the presence of an AP-1 binding site at position -110. Increased transcript levels for the standard isoform of CD44 (CD44s) are accompanied by the appearance of alternatively spliced RNAs and the synthesis of variants of CD44 (CD44v). These CD44v molecules differ from the standard type by the addition of sequences in the extracellular portion of the molecules. The occurrence of CD44v molecules in CREF cells upon induction of the CD44 promoter is probably due to leakiness of the splice control in these cells since stable transfection with c-Ha-ras does not alter the CD44v/total CD44 ratio. Upon ras overexpression, however, using an inducible mouse mammary tumor virus-ras construct, a transient increase of CD44v/total CD44 ratio of 3-4 has been determined suggesting that a burst of ras expression, in the genetic background of CREF cells, influences both promoter activity and splice control or accuracy. The expression of CD44v proteins is responsible for the metastatic potential in a variety of tumors (U. Günthert et al., Cell, 65: 13-24, 1991). Also in CREF cells expression of CD44v correlates with metastatic behavior, ras-transfected CREF cells are not only fully transformed but also give rise to metastatic spread as measured in the spontaneous metastasis assay. The adenoviral oncogene E1A counteracts ras-induced promoter function and, consequently, inhibits metastatic behavior without extinguishing transformation.

Animals↗
PubMed1993

Expression of cell adhesion molecules alpha-2, alpha-5 and alpha-6 integrin, E-cadherin, N-CAM and CD-44 in renal cell carcinomas. An immunohistochemical study.

Renal cell carcinoma is known to metastasize early independent of tumour grade. Invasion of the renal vein plays an important role in the prognosis. Cell adhesion molecules have been investigated, including the expression of alpha-2, alpha-5, and alpha-6 integrin, E-cadherin, neural-cell adhesion molecule and CD-44 in 34 renal cell carcinomas, using the alkaline phosphatase-anti-alkaline phosphatase technique. Our results indicate a differential expression of these cell adhesion molecules (alpha-2, alpha-5 and E-cadherin) depending on histological type and tumour grade.

Cadherins↗
PubMed1993

[Occurrence of CD44 and its isoforms under orthological and pathological conditions].

Variant isoforms of CD44 have been strongly implicated in malignant transformation and cancer metastasis. To ascertain the pattern of expression of these isoforms in human normal, fetal and tumor tissues (breast carcinomas, renal cell carcinomas, malignant melanomas, colon carcinomas, non-Hodgkin-lymphomas, neuroblastomas and brain tumors), we generated monoclonal antibodies against CD44 variant regions. Monoclonal antibodies were produced against variant regions encoded by exons 4v, 6v and 9v. CD44 variant isoforms are expressed on normal epithelial cells in a different pattern. Regions of epithelia that expressed the highest levels of the variant isoforms were those with a high rate of cell division. CD44 variant isoforms were not expressed by all investigated tumors (not by malignant melanomas, brain tumors and neuroblastomas). It is interesting that the expression of CD44 isoforms in non-Hodgkins lymphomas and colon carcinomas shows possibly a correlation with malignancy.

Antibodies, Monoclonal↗
PubMed1991

CD44 splice variants confer metastatic behavior in rats: homologous sequences are expressed in human tumor cell lines.

One of several splice variants of CD44 expressed in metastasizing cell lines of rat tumors has been shown to confer metastatic potential to the non-metastatic variant of a rat pancreatic carcinoma line (U. Günthert et al., Cell, 65: 13-24, 1991). The variant-specific rat CD44 sequences were used to detect RNA expression in human cell lines: in carcinoma lines from lung, breast and colon; and in keratinocyte lines. By polymerase chain reaction amplification, complementary DNAs encoding human homologues were isolated and sequenced. The largest splice variant has been found in a large cell lung carcinoma line and in keratinocyte cell lines. It carries at least 5 additional domains (exons) encoding a total of 338 amino acids in the membrane-proximal extracellular region of the standard CD44. Various alternative splice products have been detected in other human tumor cell lines. The distribution of CD44 splice variants is consistent with the speculation that they fulfill functions in only a few restricted differentiation pathways and that in tumor cells these pathways have been reactivated.

Amino Acid Sequence↗