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B Zbar

Publications and source records attributed to B Zbar.

At least 37 records · Page 2Linked to original sources
PubMed1999

Third International Meeting on von Hippel-Lindau disease.

Five years after the identification of the von Hippel-Lindau (VHL) gene, physicians, scientists and concerned VHL family members met to review the current state of knowledge on the diagnosis and treatment of VHL and to summarize the latest information on the biochemistry of the VHL protein (pVHL). The NIH and University of Pennsylvania groups reported the detection of germ-line mutations in 100% (93 of 93) of VHL families studied. Several studies determined the frequency of VHL germ-line mutations in individuals with a single manifestation of VHL without a family history of VHL. National groups to improve the diagnosis and treatment of individuals with VHL disease have been established in Great Britain, Denmark, France, Holland, Italy, Japan, Poland, and the United States. Evidence for the existence of genes that modify the expression of VHL was presented. The VHL protein appears to have several distinct functions: (a) down-regulation of hypoxia-inducible mRNAs; (b) proper assembly of the extracellular fibronectin matrix; (c) regulation of exit from the cell cycle; and (d) regulation of expression of carbonic anhydrases 9 and 12.

Animals↗
PubMed1999

Novel mutations of the MET proto-oncogene in papillary renal carcinomas.

Hereditary papillary renal carcinoma (HPRC) is characterized by multiple, bilateral papillary renal carcinomas. Previously, we demonstrated missense mutations in the tyrosine kinase domain of the MET proto-oncogene in HPRC and a subset of sporadic papillary renal carcinomas. In this study, we screened a large panel of sporadic papillary renal carcinomas and various solid tumors for mutations in the MET proto-oncogene. Summarizing these and previous results, mutations of the MET proto-oncogene were detected in 17/129 sporadic papillary renal carcinomas but not in other solid tumors. We detected five novel missense mutations; three of five mutations were located in the ATP-binding region of the tyrosine kinase domain of MET. One novel mutation in MET, V1110I, was located at a codon homologous to an activating mutation in the c-erbB proto-oncogene. These mutations caused constitutive phosphorylation of MET when transfected into NIH3T3 cells. Molecular modeling studies suggest that these activating mutations interfere with the intrasteric mechanism of tyrosine kinase autoinhibition and facilitate transition to the active form of the MET kinase. The low frequency of MET mutations in noninherited papillary renal carcinomas (PRC) suggests that noninherited PRC may develop by a different mechanism than hereditary papillary renal carcinoma.

3T3 Cells↗
PubMed1999

Somatic mutations in the kinase domain of the Met/hepatocyte growth factor receptor gene in childhood hepatocellular carcinomas.

The MET protooncogene encodes a transmembrane tyrosine kinase identified as the receptor of a polypeptide known as hepatocyte growth factor/scatter factor. We performed PCR-based single-strand conformational polymorphism and sequencing analysis of the tyrosine kinase domain of the MET gene (exon 15-19) in 75 primary liver cancers. Three missense mutations were detected exclusively in 10 childhood hepatocellular carcinomas (HCCs), while no mutations were detected in 16 adult HCCs, 21 cholangiocarcinomas, or 28 hepatoblastomas. The extremely short incubation period from hepatitis B virus infection to the genesis of childhood HCC as compared with the adult HCC suggests that there may be an additional mechanism that accelerates the carcinogenesis of childhood HCC. Our results indicate that mutations of the tyrosine kinase domain of the MET gene may be involved in the acceleration of the carcinogenesis in childhood HCC.

Adolescent↗
PubMed1999

Birt-Hogg-Dubé syndrome: a novel marker of kidney neoplasia.

BACKGROUND: Birt-Hogg-Dubé syndrome (BHD) is a dominantly inherited predisposition for development of fibrofolliculomas, trichodiscomas, and acrochordons. Concurrent internal tumors, such as colonic polyps and renal carcinoma, have been described in patients with BHD. OBJECTIVE: To evaluate kindreds with familial renal tumors for cutaneous manifestations of BHD. DESIGN: One hundred fifty-two patients from 49 families underwent complete oral and skin examination. Skin lesions were identified by their clinical appearance, and the diagnosis was confirmed by results of histologic examination. Individuals underwent screening for familial renal neoplasms. SETTING: A tertiary referral research hospital. PATIENTS: Individuals with familial renal tumors and their asymptomatic at-risk relatives. MAIN OUTCOME MEASURE: We determined whether any form of renal cancer is associated BHD. RESULTS: We identified 3 extended kindreds in whom renal neoplasms and BHD appeared to segregate together. Two kindreds had renal oncocytomas and a third had a variant of papillary renal cell carcinoma. Thirteen patients exhibited BHD. Seven individuals, including a set of identical twins, had renal neoplasms and BHD. An additional 4 patients (3 deceased and not examined) in these families had renal neoplasms but not BHD. Birt-Hogg-Dubé syndrome without renal neoplasms was present in 6 individuals. Thirteen patients with fibrofolliculomas and trichodiscomas presented clinically with multiple smooth skin-colored to grayish-white papules located on the face, auricles, neck, and upper trunk. Oral papules were present in 9 of 28 and achrochordons in 11 of 28 patients. Features of BHD not previously appreciated included deforming lipomas in 5, collagenomas in 4, and pulmonary cysts in 4 of 28 patients. Families with BHD did not display germline mutations in the von Hippel-Lindau gene or in the tyrosine kinase domain of the MET proto-oncogene. CONCLUSIONS: Birt-Hogg-Dubé syndrome may be associated with familial renal tumors. Birt-Hogg-Dubé and renal tumors segregate together in an autosomal dominant fashion. Patients with BHD and their relatives are at risk for development of renal tumors. Therefore, patients with BHD and their relatives should undergo abdominal computed tomography and renal ultrasound screening for renal tumors.

Adult↗
PubMed1999

Hereditary and sporadic papillary renal carcinomas with c-met mutations share a distinct morphological phenotype.

Germline mutations of c-met oncogene at 7q31 have been detected in patients with hereditary papillary renal cell carcinoma. In addition, c-met mutations were shown to play a role in 13% of patients with papillary renal cell carcinoma and no family history of renal tumors. The histopathology of papillary renal cell carcinoma with c-met mutations has not been previously described. We analyzed the histopathology of 103 bilateral archival papillary renal cell carcinomas and 4 metastases in 29 patients from 6 hereditary papillary renal cell carcinoma families with germline c-met mutations and 6 papillary renal cell carcinomas with c-met mutations from 5 patients with no family history of renal tumors. Twenty-five sporadic renal tumors with prominent papillary architecture and without somatic c-met mutations were evaluated for comparison. All papillary renal cell carcinomas with c-met mutations were 75 to 100% papillary/tubulopapillary in architecture and showed chromophil basophilic, papillary renal cell carcinoma type 1 histology. Fuhrman nuclear grade 1-2 was seen in tumors from 23 patients, and nuclear grade 3 was observed focally in 8 patients. Seventeen patients had multiple papillary adenomas and microscopic papillary lesions in the surrounding renal parenchyma. Clear cells with intracytoplasmic lipid and glycogen were focally present in tumors of 94% papillary renal cell carcinoma patients. Clear cells of papillary renal cell carcinoma had small basophilic nuclei, and clear cell areas lacked a fine vascular network characteristic of conventional (clear) cell renal cell carcinoma. We conclude that papillary renal cell carcinoma patients with c-met mutations develop multiple, bilateral, papillary macroscopic and microscopic renal lesions. Renal tumors with c-met genotype show a distinctive papillary renal cell carcinoma type 1 phenotype and are genetically and histologically different from renal tumors seen in other hereditary renal syndromes and most sporadic renal tumors with papillary architecture. Although all hereditary and sporadic papillary renal cell carcinomas with c-met mutations share papillary renal cell carcinoma type 1 histology, not all type 1 sporadic papillary renal cell carcinomas harbor c-met mutations.

Adenoma↗
PubMed1999

Expression of von Hippel-Lindau protein in normal and pathological human tissues.

To examine the localization of von Hippel-Lindau (VHL) protein in human tissues, we produced four novel monoclonal antibodies against human VHL protein. Western blot analysis revealed that two of these antibodies recognized the epitope in amino acid sequence 60-89 of the VHL protein and the others recognized sequences 54-60 and 189-213. In a wild-type VHL gene-transfected cell line, immunocytochemistry and immunoelectron microscopy demonstrated the intracytoplasmic localization of VHL protein, particularly in mitotic cells. In normal human tissues, VHL protein was detected immunohistochemically in epithelial cells covering the body surface and the alimentary, respiratory, and genitourinary tracts; in secretory epithelial cells of exocrine and endocrine organs; in parenchymal cells of visceral organs; in cardiomyocytes; in neurons in nervous tissue; in lymphocytes in lymphoid tissue; and in macrophages. In pathological specimens, VHL protein was expressed in VHL-related tumor, as well as in endothelial cells, fibroblasts, and pericytes, all of which are involved in active angiogenesis. These findings suggest that these monoclonal antibodies can be useful for various immunological assays and that the VHL protein plays fundamental roles in physiological and pathological situations, especially in neovascularization.

Adolescent↗
PubMed1999

Clinical and genetic characterization of pheochromocytoma in von Hippel-Lindau families: comparison with sporadic pheochromocytoma gives insight into natural history of pheochromocytoma.

PURPOSE: Families with von Hippel-Lindau disease have variable risk of pheochromocytoma. Patients with von Hippel-Lindau disease and pheochromocytoma identified by screening can have no characteristic signs or symptoms. Families with von Hippel-Lindau disease were screened and followed to describe the natural history of von Hippel-Lindau pheochromocytoma, and to correlate these findings with von Hippel-Lindau germline mutation. MATERIALS AND METHODS: Between 1988 and 1997, 246 individuals with von Hippel-Lindau disease were identified (von Hippel-Lindau group). Between August 1990 and June 1997, 26 consecutive patients with sporadic pheochromocytoma were evaluated (sporadic group). RESULTS: A total of 64 patients with von Hippel-Lindau disease had manifestations of pheochromocytoma, including 33 newly diagnosed during screening at the National Institutes of Health and 31 previously treated (93 adrenal and 13 extra-adrenal pheochromocytomas). Germline von Hippel-Lindau gene missense mutation was associated with extra-adrenal pheochromocytoma, younger age at presentation and the only patient with metastases. Of the 33 newly diagnosed patients with von Hippel-Lindau disease 4 had pheochromocytoma 2 times (37 pheochromocytomas) during followup. Of these pheochromocytomas 35% (13 of 37) were associated with no symptoms, normal blood pressure and normal catecholamine testing. Comparison of urinary catecholamines in the von Hippel-Lindau and sporadic groups demonstrated increased epinephrine, metanephrines and vanillylmandelic acid in the sporadic group. Analysis of urinary catecholamine excretion in the von Hippel-Lindau and sporadic groups together demonstrated a correlation between tumor size, and urinary metanephrines, vanillylmandelic acid, norepinephrine, epinephrine and dopamine. In 12 patients without signs or symptoms of pheochromocytoma 17 newly diagnosed pheochromocytomas were followed for a median of 34.5 months without morbidity. Median tumor doubling time was 17 months. CONCLUSIONS: Von Hippel-Lindau gene missense mutation correlated with the risk of pheochromocytoma in patients with von Hippel-Lindau disease. These findings support a von Hippel-Lindau disease clinical classification, wherein some families are at high risk for manifestations of pheochromocytoma. Von Hippel-Lindau disease pheochromocytomas identified by screening were smaller and less functional than sporadic pheochromocytomas.

Adrenal Gland Neoplasms↗
PubMed1999

Protective function of von Hippel-Lindau protein against impaired protein processing in renal carcinoma cells.

The absence of functional von Hippel-Lindau (VHL) tumor suppressor gene leads to the development of neoplasias characteristic of VHL disease, including renal cell carcinoma (RCC). Here, we compared the sensitivity of RCC cells lacking VHL gene function with that of RCC cells expressing the wild-type VHL gene (wtVHL) after exposure to various stresses. While the response to most treatments was not affected by the VHL gene status, glucose deprivation was found to be much more cytotoxic for RCC cells lacking VHL gene function than for wtVHL-expressing cells. The heightened sensitivity of VHL-deficient cells was not attributed to dissimilar energy requirements or to differences in glucose uptake, but more likely reflects a lesser ability of VHL-deficient cells to handle abnormally processed proteins arising from impaired glycosylation. In support of this hypothesis, other treatments which act through different mechanisms to interfere with protein processing (i.e., tunicamycin, brefeldin A, and azetidine) were also found to be much more toxic for VHL-deficient cells. Furthermore, ubiquitination of cellular proteins was elevated in VHL-deficient cells, particularly after glucose deprivation, supporting a role for the VHL gene in ubiquitin-mediated proteolysis. Accordingly, the rate of elimination of abnormal proteins was lower in cells lacking a functional VHL gene than in wtVHL-expressing cells. Thus, pVHL appears to participate in the elimination of misprocessed proteins, such as those arising in the cell due to the unavailability of glucose or to other stresses.

Apoptosis↗
PubMed1999

Synthetic peptides define critical contacts between elongin C, elongin B, and the von Hippel-Lindau protein.

The von Hippel-Lindau tumor suppressor protein (pVHL) negatively regulates hypoxia-inducible mRNAs such as the mRNA encoding vascular endothelial growth factor (VEGF). This activity has been linked to its ability to form multimeric complexes that contain elongin C, elongin B, and Cul2. To understand this process in greater detail, we performed a series of in vitro binding assays using pVHL, elongin B, and elongin C variants as well as synthetic peptide competitors derived from pVHL or elongin C. A subdomain of elongin C (residues 17-50) was necessary and sufficient for detectable binding to elongin B. In contrast, elongin B residues required for binding to elongin C were not confined to a discrete colinear domain. We found that the pVHL (residues 157-171) is necessary and sufficient for binding to elongin C in vitro and is frequently mutated in families with VHL disease. These mutations preferentially involve residues that directly bind to elongin C and/or alter the conformation of pVHL such that binding to elongin C is at least partially diminished. These results are consistent with the view that diminished binding of pVHL to the elongins plays a causal role in VHL disease.

Amino Acid Sequence↗
PubMed1998

Subcellular localization of the von Hippel-Lindau disease gene product is cell cycle-dependent.

The von Hippel-Lindau gene product (pVHL) interacts with and inhibits the cellular transcription factor elongin. However, the subcellular localization of pVHL has remained uncertain. Naturally occurring pVHL mutants which fail to interact with elongin have been described in patients with VHL disease or sporadic renal cell carcinoma (RCC). Here, we have examined the cellular expression pattern of endogenous pVHL in different RCC cell lines by immunocytochemistry and confocal microscopy. Both anti-N-terminal and anti-C-terminal pVHL antibodies were able to recognize endogenous wild-type pVHL expressed by the RCC cells studied. A C-terminal truncated VHL mutant expressed by RCC cell line A498 was detected only by the N-terminal antibody but not by the C-terminal antibody as expected. The overall staining patterns of these cell lines are similar, with a predominant nuclear speckled pattern and a moderate cytoplasmic staining in subconfluent cell cultures. Interestingly, when cells reached confluency, more prominent nuclear staining with little or no cytoplasmic expression was observed. By using double labeling with anti-VHL and anti-bromodeoxyuridine (BrdU) antibodies and cell cycle analyses, we found that in the G1/G0-phase, pVHL was localized exclusively in the nucleus associated with distinctive large subnuclear structures, whereas the majority of the cells in S-phase of the cell cycle also showed a diffuse cytoplasmic staining. Our results indicate that subcellular localization of pVHL is regulated in a cell cycle-dependent manner.

Carcinoma, Renal Cell↗
PubMed1998

Two North American families with hereditary papillary renal carcinoma and identical novel mutations in the MET proto-oncogene.

Hereditary papillary renal carcinoma (HPRC) is a newly recognized inherited disorder characterized by a predisposition to develop multiple bilateral papillary renal carcinomas. Individuals affected with HPRC have been shown to have germ-line mutations in the tyrosine kinase domain of the MET proto-oncogene. We identified a novel mutation in exon 16 of the MET gene in two large North American HPRC families. The H1112R MET mutation segregated with the disease, was not present in 320 normal chromosomes, and caused malignant transformation of NIH 3T3 cells. By examining individuals with the H1112R mutation, we determined the age-dependent penetrance of this mutation and identified additional nonrenal malignancies that occurred in mutation carriers. Affected members of the two families shared the same haplotype within and immediately distal to the MET gene, suggesting a founder effect. The identification of the H1112R mutation will facilitate predictive testing in HPRC and guide future studies of the MET gene in human neoplasia.

3T3 Cells↗
PubMed1998

Loss of heterozygosity and somatic mutations of the VHL tumor suppressor gene in sporadic cerebellar hemangioblastomas.

Cerebellar hemangioblastoma is a benign central nervous system neoplasm with characteristic proliferation of vascular and stromal cells. There is increasing evidence that the stromal cell population may represent the neoplastic component of hemangioblastoma, whereas the vascular component may be composed of reactive, nonneoplastic cells. Therefore, successful genetic testing for loss of heterozygosity requires selective analysis of target cell populations. Here, tissue microdissection was used to selectively analyze the stromal cell component of 20 archival sporadic cerebellar hemangioblastomas for loss of heterozygosity at the Von-Hippel Lindau (VHL) gene and somatic VHL gene mutations. Allelic deletions at the VHL gene locus were detected in the stromal cell component with one or more markers (D3S1038, D3S1110, and/or 104/105) in 10 of 19 (52.6%) informative cases. In all cases, heterozygosity at the VHL gene locus was retained in the vascular component. In two cases, aberrant bands in exon 2 of the VHL gene were demonstrated in the stromal cells by PCR-based single-strand conformation polymorphism analysis, and somatic missense mutations were successfully characterized in two of the sporadic hemangioblastomas by direct sequencing. The results suggest that allelic losses and mutations of the VHL tumor suppressor gene play a role in sporadic cerebellar hemangioblastoma tumorigenesis. Furthermore, because the genetic changes were detected in selectively procured stromal cell areas, the data provide strong evidence that the stromal cell represents a neoplastic component of hemangioblastoma.

Adolescent↗
PubMed1998

Improved detection of germline mutations in the von Hippel-Lindau disease tumor suppressor gene.

von Hippel-Lindau disease (VHL) is an inherited neoplastic disorder characterized by the development of tumors in the eyes, brain, spinal cord, inner ear, adrenal gland, pancreas, kidney, and epididymis. The VHL tumor suppressor gene was identified in 1993. Initial studies reported the detection of germline mutations in the VHL gene in 39-75% of VHL families. We used tests that detect different types of mutations to improve the frequency of detection of germline mutations in VHL families. The methods included quantitative Southern blotting to detect deletions of the entire VHL gene, Southern blotting to detect gene rearrangements, fluorescence in situ hybridization (FISH) to confirm deletions, and complete sequencing of the gene. Here we report that we have detected germline mutations in the VHL gene in 100% (93/93) of VHL families tested. In addition, we describe 13 novel intragenic VHL germline mutations. With the methodology described in this article, it is now possible to identify germline mutations in virtually all families with VHL.

Blotting, Southern↗
PubMed1998

Familial renal oncocytoma: clinicopathological study of 5 families.

PURPOSE: We analyzed familial renal oncocytoma to provide a foundation for studies aimed at defining genes involved in the pathogenesis of renal oncocytoma. MATERIALS AND METHODS: We describe 5 families with multiple members affected with renal oncocytoma. Tumors were analyzed pathologically, and affected and nonaffected members were screened clinically and genetically. RESULTS: We identified 12 affected male and 3 affected female (ratio 4:1) individuals in the 5 families. In affected family members renal oncocytomas were often multiple and bilateral. No metastatic disease was observed. Most renal oncocytomas were detected incidentally in asymptomatic individuals or during screening of asymptomatic members of renal oncocytoma families. One identical twin pair was affected with bilateral multiple renal oncocytomas. CONCLUSIONS: Renal oncocytoma may be inherited in some families.

Adenoma, Oxyphilic↗
PubMed1998

Inherited carcinomas of the kidney.

Studies of families with inherited carcinomas have provided powerful tools to identify the genes involved in the pathogenesis of human cancers. In this review, we summarize the clinical, pathological, and genetic characteristics of the inherited carcinomas of the kidney. We emphasize the observation that different genes predispose to histologically different types of renal carcinoma. Hereditary papillary renal carcinoma, a recently described inherited disorder, is discussed in detail along with the predisposing gene, the MET protooncogene. The data support a classification of renal carcinomas based on molecular genetics.

Adenocarcinoma, Clear Cell↗
PubMed1998

Trisomy 7-harbouring non-random duplication of the mutant MET allele in hereditary papillary renal carcinomas.

The gene defect for hereditary papillary renal carcinoma (HPRC) has recently been mapped to chromosome 7q, and germline mutations of MET (also known as c-met) at 7q31 have been detected in patients with HPRC (ref. 2). Tumours from these patients commonly show trisomy of chromosome 7 when analysed by cytogenetic studies and comparative genomic hybridization (CGH). However, the relationship between trisomy 7 and MET germline mutations is not clear. We studied 16 renal tumours from two patients with documented germline mutations in exon 16 of MET. Fluorescent in situ hybridization (FISH) analysis showed trisomy 7 in all tumours. To determine whether the chromosome bearing the mutant or wild-type MET gene was duplicated, we performed duplex PCR and phosphoimage densitometry using polymorphic microsatellite markers D7S1801 and D7S1822, which were linked to the disease gene locus, and D1S1646 as an internal control. We determined the parental origin of chromosome alleles by genotyping parental DNA. In all 16 tumours there was an increased signal intensity (2:1 ratio) of the microsatellite allele from the chromosome bearing the mutant MET compared with the allele from the chromosome bearing the wild-type MET. Our study demonstrates a non-random duplication of the chromosome bearing the mutated MET in HPRC and implicates this event in tumorigenesis.

Adult↗
PubMed1997

Activating mutations for the met tyrosine kinase receptor in human cancer.

Recently, mutations in the Met tyrosine kinase receptor have been identified in both hereditary and sporadic forms of papillary renal carcinoma. We have introduced the corresponding mutations into the met cDNA and examined the effect of each mutation in biochemical and biological assays. We find that the Met mutants exhibit increased levels of tyrosine phosphorylation and enhanced kinase activity toward an exogenous substrate when compared with wild-type Met. Moreover, NIH 3T3 cells expressing mutant Met molecules form foci in vitro and are tumorigenic in nude mice. Enzymatic and biological differences were evident among the various mutants examined, and the somatic mutations were generally more active than those of germ-line origin. A strong correlation between the enzymatic and biological activity of the mutants was observed, indicating that tumorigenesis by Met is quantitatively related to its level of activation. These results demonstrate that the Met mutants originally identified in human papillary renal carcinoma are oncogenic and thus are likely to play a determinant role in this disease, and these results raise the possibility that activating Met mutations also may contribute to other human malignancies.

3T3 Cells↗