Mutations of the VHL tumour suppressor gene in renal carcinoma.

Multiple, bilateral renal carcinomas are a frequent occurrence in von Hippel-Lindau (VHL) disease. To elucidate the aetiological role of the VHL gene in human kidney tumorigenesis, localized and advanced tumours from 110 patients with sporadic renal carcinoma were analysed for VHL mutations and loss of heterozygosity (LOH). VHL mutations were identified in 57% of clear cell renal carcinomas analysed and LOH was observed in 98% of those samples. Moreover, VHL was mutated and lost in a renal tumour from a patient with familial renal carcinoma carrying the constitutional translocation, t(3;8)(p14;q24). The identification of VHL mutations in a majority of localized and advanced sporadic renal carcinomas and in a second form of hereditary renal carcinoma indicates that the VHL gene plays a critical part in the origin of this malignancy.

Increased intracellular cyclic adenosine monophosphate inhibits T lymphocyte-mediated cytolysis by two distinct mechanisms.

Cholera toxin (CT), but not pertussis toxin (PT), treatment of cloned murine CTL inhibited target cell lysis in a dose-dependent fashion. The effects of CT were mimicked by forskolin and cyclic adenosine monophosphate (cAMP) analogues. Inhibition of cytotoxicity by CT and cAMP analogs was mediated in part by attenuation of conjugate formation. Additionally, both CT and cAMP analogs blocked the increase in intracellular Ca2+ induced by stimulation of the TCR complex by mAbs. These findings indicate that cAMP inhibits the activity of CTL by two distinct mechanisms and suggests a role for this second messenger in CTL-mediated cytolysis.

Identification of the von Hippel-Lindau disease tumor suppressor gene.

A gene discovered by positional cloning has been identified as the von Hippel-Lindau (VHL) disease tumor suppressor gene. A restriction fragment encompassing the gene showed rearrangements in 28 of 221 VHL kindreds. Eighteen of these rearrangements were due to deletions in the candidate gene, including three large nonoverlapping deletions. Intragenic mutations were detected in cell lines derived from VHL patients and from sporadic renal cell carcinomas. The VHL gene is evolutionarily conserved and encodes two widely expressed transcripts of approximately 6 and 6.5 kilobases. The partial sequence of the inferred gene product shows no homology to other proteins, except for an acidic repeat domain found in the procyclic surface membrane glycoprotein of Trypanosoma brucei.

The von Hippel-Lindau tumor suppressor gene inhibits hepatocyte growth factor/scatter factor-induced invasion and branching morphogenesis in renal carcinoma cells.

Loss of function in the von Hippel-Lindau (VHL) tumor suppressor gene occurs in familial and most sporadic renal cell carcinomas (RCCs). VHL has been linked to the regulation of cell cycle cessation (G(0)) and to control of expression of various mRNAs such as for vascular endothelial growth factor. RCC cells express the Met receptor tyrosine kinase, and Met mediates invasion and branching morphogenesis in many cell types in response to hepatocyte growth factor/scatter factor (HGF/SF). We examined the HGF/SF responsiveness of RCC cells containing endogenous mutated (mut) forms of the VHL protein (VHL-negative RCC) with that of isogenic cells expressing exogenous wild-type (wt) VHL (VHL-positive RCC). We found that VHL-negative 786-0 and UOK-101 RCC cells were highly invasive through growth factor-reduced (GFR) Matrigel-coated filters and exhibited an extensive branching morphogenesis phenotype in response to HGF/SF in the three-dimensional (3D) GFR Matrigel cultures. In contrast, the phenotypes of A498 VHL-negative RCC cells were weaker, and isogenic RCC cells ectopically expressing wt VHL did not respond at all. We found that all VHL-negative RCC cells expressed reduced levels of tissue inhibitor of metalloproteinase 2 (TIMP-2) relative to the wt VHL-positive cells, implicating VHL in the regulation of this molecule. However, consistent with the more invasive phenotype of the 786-0 and UOK-101 VHL-negative RCC cells, the levels of TIMP-1 and TIMP-2 were reduced and levels of the matrix metalloproteinases 2 and 9 were elevated compared to the noninvasive VHL-positive RCC cells. Moreover, recombinant TIMPs completely blocked HGF/SF-mediated branching morphogenesis, while neutralizing antibodies to the TIMPs stimulated HGF/SF-mediated invasion in vitro. Thus, the loss of the VHL tumor suppressor gene is central to changes that control tissue invasiveness, and a more invasive phenotype requires additional genetic changes seen in some but not all RCC lines. These studies also demonstrate a synergy between the loss of VHL function and Met signaling.

Expression of Pax-2 in human renal cell carcinoma and growth inhibition by antisense oligonucleotides.

Renal cell carcinoma (RCC) is the most common malignancy in the adult kidney. Because RCC is generally thought to arise from the epithelium of the proximal tubules, the expression of Pax-2, a gene required for renal epithelium development, was examined in primary tumors and tumor-derived cell lines. Immunostaining of frozen sections from the primary tumors indicated Pax-2 expression in the malignant cells but not in the surrounding stroma. In a panel of human RCC-derived cell lines, 73% expressed Pax-2 protein and mRNA. Treatment of RCC cell lines with antisense oligodeoxynucleotides resulted in down-regulation of Pax-2 protein expression and growth inhibition after 3 days in culture. These data indicate that Pax-2 gene function is required for proliferation, as well as differentiation during embryonic development, and suggest a novel therapy for RCC.

Chromosome 17p deletions and p53 mutations in renal cell carcinoma.

Studies of the role of tumor suppressor genes in human renal cell carcinoma from our laboratory have suggested the presence of a disease gene(s) on the short arm of chromosome 3. Little is known about the role other tumor suppressor genes may play in this malignancy. Abnormalities of chromosome 17p and, in particular of p53, are common in many human malignancies. In order to evaluate the role of this region in renal cell carcinoma, we performed restriction fragment length polymorphism analyses of chromosome 17 with probes localized to the p53 region. Fourteen of 29 (48%) evaluable cell lines showed loss of heterozygosity at this locus. Northern blot analysis did not detect a p53 transcript in 4 of 27 cell lines tested. In addition, we screened cell lines for p53 mutations using a polymerase chain reaction-single strand conformation polymorphism technique. Cell lines positive for mutations by this technique were then sequenced. Mutations were detected in 11 of 33 (33%) cell lines, including 8 derived from primary tumors and 3 derived from metastatic foci. Six of 9 (67%) patients with loss of heterozygosity demonstrated a mutation in the remaining allele, while only 1 of 8 (13%) without loss of heterozygosity had a mutation. Three of 3 (100%) cell lines derived from metastases had the same mutation as their matched primary cell line. Loss or mutation of p53 did not correlate either with loss of chromosome 3p or with histological subtype. These results suggest that, while the primary disease gene for kidney cancer appears to be on chromosome 3, abnormalities of p53 are common and may be involved in the progression of this malignancy.

Regional DNA hypermethylation at D17S5 precedes 17p structural changes in the progression of renal tumors.

In a preceding paper for brain tumors, we demonstrate a tight association between regional hypermethylation at locus D17S5 of chromosome 17p and allelic loss of this chromosome. Because 17p allelic losses occur at the earliest stages of brain tumors, the exact temporal relationship between this event and the hypermethylation could not be elucidated. In renal cancers, two linked structural changes on chromosome 17p, allelic loss and p53 gene mutations, generally occur late in progression. We now show that D17S5 hypermethylation is tightly coupled to both of these genetic changes in late stage renal tumors. However, the methylation change is the only one of the 17p abnormalities which occurs at a high incidence in early-stage renal cancers (hypermethylation, 50%; 17p allelic loss, 13%; p53 mutations, 0%). Our results firmly suggest that D17S5 regional hypermethylation precedes the appearance of the consistent 17p genetic changes in renal cancers, suggesting that this event either marks, or may even cause, chromatin changes which predispose to genetic instability.

von Hippel-Lindau syndrome: cloning and identification of the plasma membrane Ca(++)-transporting ATPase isoform 2 gene that resides in the von Hippel-Lindau gene region.

We have isolated and analyzed full-length complementary DNA clones encoded by a 200-kilobase gene encompassing the D3S601 locus that resides in the von Hippel-Lindau (VHL) gene region. The deduced amino acid sequence shows 99% identity with the published sequence of the rat plasma membrane Ca(++)-transporting ATPase isoform 2 complementary DNA, implying that we have cloned and positioned the human plasma membrane Ca(++)-transporting ATPase isoform 2 gene within the VHL critical region. The gene is expressed in VHL target tissues and should be considered a potential candidate gene for the VHL disease.

One-megabase yeast artificial chromosome and 400-kilobase cosmid-phage contigs containing the von Hippel-Lindau tumor suppressor and Ca(2+)-transporting adenosine triphosphatase isoform 2 genes.

We have isolated and ordered yeast artificial chromosomes (YACs) and cosmids surrounding the von Hippel-Lindau (VHL) tumor suppressor and plasma membrane Ca(2+)-transporting ATPase isoform 2 (PMCA-2) genes on chromosome 3p25-26. The YAC contig consists of six YACs and covers a region of 1 megabase. A cosmid-phage contig around VHL and PMCA-2 genes (400 kilobases) was established and integrated into the YAC map. Using these clones, we generated an EcoRI map of the 400-kilobase region. PMCA-2 and VHL complementary DNA were positioned entirely within the cosmid-phage contig as well as two polymorphic markers (D3S601 and D3S1317). This physical map of the cloned region will allow a detailed analysis of both the PMCA-2 and VHL genes. Some of the genomic clones may be useful for isolation of the full-length VHL complementary DNA.

Molecular analysis of the von Hippel-Lindau disease tumor suppressor gene in human lung cancer cell lines.

The deletion of the short arm of chromosome 3 is frequently observed in lung cancer. To determine whether the von Hippel-Lindau (VHL) disease tumor suppressor gene located at 3p25 is responsible for oncogenesis in lung cancer, we searched the known open reading frame using the single-strand conformation polymorphism (SSCP) technique for mutations in the VHL gene in 72 cancer cell lines including small cell (SCLC) and non-small cell (NSCLC) lung cancers, carcinoids, and mesotheliomas. SSCP analysis showed that four cell lines have altered SSCP patterns within the coding region and one in an intron of the VHL gene. SCLC line NCI-H1672 had a somatic mutation, G to A at nucleotide (nt) 530, leading to amino acid substitution (glycine to aspartic acid) compared to normal DNA from the same patient. Mesothelioma line NCI-H28 had T to A mutation at nt 479 leading to leucine to histidine amino acid change. We found one frequent polymorphism A (0.72) or G (0.28) at nt 19 resulting in either serine or glycine at this position, changes also found in normal peripheral blood cell DNA, often in a heterozygous state. In addition, we found single rare polymorphisms which did not alter the coding region including: C to G at nt 396, G to T at nt 843, and C to T change in an intron. These results suggest that the VHL gene is only rarely mutated in thoracic malignancies.

Examination of human tumors for rhoA mutations.

rhoA encodes a ras-related GTP-binding protein that is thought to play a role in cytoskeletal organization. Recent evidence has suggested both that rhoA could act either as a dominant oncogene, since transfection of both normal and activated rho genes confer a transformed phenotype on fibroblast cells in culture, or as a recessive tumor suppressor gene, by virtue, in part, of its chromosomal location at 3p21, a site deleted in many human malignancies. In either case, a role for rhoA in the oncogenesis of human tumors would be supported by the finding of rhoA mutations in tumors. We therefore examined human tumors and cell lines for mutations in the protein coding regions of rhoA by RNAase protection analysis. We first examined the expression of rhoA in renal cell carcinoma cell lines in which 3p21 was heterozygously deleted or retained. We found no evidence for rhoA mutations in these specimens. We also examined RNA from lung, breast, colon or ovarian tumors and also found no evidence of activating rhoA mutations. Furthermore, there was no relation between the level of rhoA mRNA expression and the presence or absence of 3p21 deletions in the renal cell carcinoma specimens. Thus, although rhoA has transforming potential in vitro, there is no evidence that it is activated by mutation in human malignancies, or that it could act as a tumor suppressor gene in tumors in which 3p21 is deleted.

Genetics of renal-cell carcinoma and evidence for a critical role for von Hippel-Lindau in renal tumorigenesis.

Using a genetic linkage-based positional cloning approach the VHL gene was identified at chromosome 3p25.5. VHL is mutated in the germlines of affected individuals, and in VHL-associated tumors the mutation is almost always exposed by virtue of chromosomal deletion of the inherited wild-type allele. VHL is also frequently mutated in sporadic, nonpapillary RCC and in familial RCC. This was predicted because such tumors are histologically similar to VHL-associated renal tumors. Knowledge that VHL plays a critical role in sporadic RCC should aid in the future diagnosis and treatment of this malignancy. Detailed analyses of the biology of individual mutations will be required to determine whether the inherited VHL mutations or acquired sporadic mutations cause loss of protein function or have dominant-negative affects. However, the nature of the VHL protein is at present unclear and a complete understanding its function will only be expected after the cloning of the full-length gene.

von Hippel-Lindau disease gene deletion detected in microdissected sporadic human colon carcinoma specimens.

The progression of human malignancies is thought to involve the inactivation or loss of tumor suppressor genes. Previous studies have suggested that inactivation of tumor suppressor genes on chromosomes 5q, 17p, 18q, and 8p play a role in the development of colorectal carcinoma. However, chromosome 3p at the von Hippel-Lindau disease (VHL) gene locus (3p25-26) has not been previously implicated in the development or progression of sporadic colorectal carcinoma. The authors have analyzed VHL gene alterations on chromosome 3p in sporadic human colon carcinomas and adenomas using modified microdissection techniques. These techniques allow for procurement and analysis of selected subpopulations of cells from both paraffin-embedded and frozen human tumor specimens. VHL disease gene deletion was detected by polymerase chain reaction (PCR) and single-strand conformation polymorphism (SSCP) analysis in microdissected colon carcinoma specimens. Allelic loss of VHL gene was detected in 7 of 11 (64%) informative patients who underwent colectomy for primary sporadic colon carcinoma. However, no allelic loss of VHL gene was shown in colonic adenomas of eight informative patients. These results indicate that VHL disease gene deletion frequently occurs in sporadic colon carcinoma. Because this deletion was not present in adenomas, VHL gene may play a role in colonic carcinogenesis and represent a relatively late event in colonic neoplasia progression. Additionally, microdissection of tissue sections may be especially useful in detecting allelic loss in PCR-based studies of infiltrating tumors, particularly when the tumor cells represent a relatively small percentage of the total cell population.

von Hippel-Lindau gene deletion detected in the stromal cell component of a cerebellar hemangioblastoma associated with von Hippel-Lindau disease.

Central nervous system hemangioblastoma is a neoplasm with characteristic and well-described histopathological features, including proliferation of vascular and stromal cells. yet, the histogenesis of the stromal cell component and its neoplastic capacity as compared with the vascular component are still controversial. Stromal cells were selectively procured from formalin-fixed, paraffin-embedded archival tissue from a von Hippel-Lindau (VHL) disease patient with a cerebellar hemangioblastoma and studied for loss of heterozygosity (LOH) of the VHL gene locus and associated microsatellite regions. The stromal cells consistently showed LOH. Analysis of mixed stromal anti vascular areas of this tumor and four other hemangioblastomas of VHL patients showed that loss of heterozygosity was partially obscured. These preliminary results suggest that the stromal component of hemangioblastomas contains genetic alterations consistent with a neoplastic nature. Additional samples of pure stromal cells need to be analyzed to establish the prevalence of VHL gene deletion in stromal cells of capillary hemangioblastoma and, hence, its pathogenetic significance.

Early events in target-cell lysis by cytotoxic T cells.

Using ratio-imaging fluorescence microscopy, we have investigated the changes in intracellular Ca2+ [( Ca2+]i) that occurred in cytotoxic T lymphocytes (CTL) upon target-cell binding. This process resulted in a rapid increase in [Ca2+]i, which was localized in the region of the CTL in contact with the target cell. This increase was mediated both by influx from the external medium as well as by release from intracellular stores. Although the magnitude of the initial increase in [Ca2+]i was not dependent upon the presence of extracellular Ca2+, influx was necessary for sustained elevation of [Ca2+]i. Inasmuch as target-cell lysis by the CTL clone used is dependent on extracellular Ca2+, this suggests that a prolonged elevation of [Ca2+]i is necessary for lytic function. It was also shown that the increase in [Ca2+]i and its subsequent decay show several pulsations. The mechanism by which these variations are generated and their possible function is not known. Finally, a role for K+ efflux in the control of the antigen-induced increase in [Ca2+]i was demonstrated. Thus it is becoming clear that signal transduction in CTL is remarkably complex, involving several ionic species and second messengers.

Renal cell carcinoma. Cytogenetic analysis of tumors and cell lines.

Successful cytogenetic analysis was performed on 27 samples from 25 patients with RCC, including 7 of 11 tumors studied and 20 cell lines. Clonal chromosomal abnormalities were detected in all 27 samples. The most frequently involved chromosomes were 7, 1, 3, 9, and the Y (20, 17, 17, 14, and 10 cases, respectively). Polysomy 7 or rearrangement of 7q was seen in 80% (20/25) of the patients, and loss or rearrangement of 3p was seen in 48% (12/25); of the latter, four patients had loss of the whole chromosome and 10 patients had deletions or translocations involving 3p, with breakpoints at either 3p11-14 or 3p21-23 (5/7 translocation breakpoints were at 3p21-23). Loss of the sex chromosomes was seen in 15 patients, including -Y in 10/22 males. Other clonal changes included structural abnormalities of chromosome 1 centromere and the long arm, breakpoints at or near the centromere of chromosome 9 (10 patients), polysomy 16, monosomy 17, polysomy 20, and monosomy 22. With the exception of chromosome 3p loss, which was primarily confined to the nonpapillary cases, no specific clonal abnormality was noted for any particular subtype of RCC. Trisomy or tetrasomy 7 and -Y were seen in all subtypes of renal cell carcinoma.

Progelatinase A mRNA expression in cell lines derived from tumors in patients with metastatic renal cell carcinoma correlates inversely with survival.

OBJECTIVES: Tumors are thought to metastasize by a process involving tumor cell attachment to extracellular matrix, degradation of matrix components by tumor-associated proteases, and cellular movement into the area modified by protease activity. Type IV collagen comprises the major element tumor cells must degrade to gain access to the rest of the body. Renal cancer cell line progelatinase A (E.C. 3.4.24.24; 72-kDa type IV collagenase; MMP-2) mRNA expression was correlated with patient survival. METHODS: Total cellular mRNA was extracted from tumor cell lines derived from patients with metastatic renal cell carcinoma. The results of the densitometric analysis of Northern blots were correlated with patient survival. Formalin-fixed, paraffin-embedded tissue sections of primary renal cancers were examined for immunohistochemical expression of MMP-2. RESULTS: Cell lines established from 23 primary renal tumors and six metastatic sites in 26 patients with metastatic renal carcinoma were studied. Variable expression of progelatinase A, relative to A2058 melanoma cells (mean +/- SEM, 0.60 +/- 0.21; median, 0.082; range, 0 to 4.78), was found. There was a significant inverse association between patient survival and the log of the MMP-2 expression (P = 0.045 by the Cox proportional-hazards model). Using a cutoff value of 0.10, the closest round number to the median expression of MMP-2, a significant difference between survival of patients with lower and higher MMP-2 expression in their primary renal cell line was found (P = 0.0054). Cell lines with low, intermediate, and high expression of MMP-2 mRNA all had primary tumors with high tissue immunohistochemical expression of MMP-2. CONCLUSIONS: These studies demonstrate an inverse relationship between renal cancer cell line MMP-2 mRNA expression and patient survival. Immunohistochemical studies of the primary tumors from which the cell lines were derived uniformly showed high MMP-2 expression. Previous work suggests local renal factors upregulate cellular expression of MMP-2 in the primary tumor, and are not active at extrarenal sites.

Molecular genetic studies of sporadic and familial renal cell carcinoma.

Renal cell carcinoma (RCC) occurs predominantly as a sporadic disease but has familial forms. Cytogenetic and DNA deletion analyses show that both sporadic and familial RCC tumors arise as the result of chromosomal deletions in the 3p13-p26 region. von Hippel-Lindau (VHL) disease is a hereditary, multifocal syndrome that includes, among several affected organs, multiple, bilateral renal cysts and RCC. Although the VHL disease gene maps to chromosome 3p25-p26, data indicate that the VHL and sporadic RCC disease genes are likely to be independent. The authors hypothesize that VHL disease manifestations are controlled by mutations in the VHL disease gene and that the onset of VHL-associated kidney cancer is due to a second mutation of the linked sporadic RCC gene.

Renal cell carcinoma. Molecular genetics and clinical implications.

The combined efforts of a number of investigators have led to the identification of the VHL gene, which appears to function as a tumor suppressor gene and is implicated in both sporadic and familial forms of RCC. These findings should increase our understanding of the molecular biology of this malignancy; however, there is much work to be done. Identification of the mechanism of inactivation of the VHL gene, as well as the structure and function of the VHL gene product, ultimately may provide clinicians with greater understanding of this malignancy as well as with methods for earlier diagnosis. The role of other tumor suppressor genes, such as p53, is incompletely understood. It is hoped that the techniques that have been applied to the study of RCC also will result in advances in our knowledge of other urologic malignancies.