Comprehensive mutational analysis of the VHL gene in sporadic renal cell carcinoma: relationship to clinicopathological parameters

To delineate more precisely the somatic von Hippel-Lindau disease (VHL) gene alteration as well as to elucidate its etiologic role in renal tumorigenesis, we examined a total of 240 sporadic renal cell carcinomas (RCCs) for somatic VHL gene alterations by DNA-SSCP followed by sequencing, methylation-specific PCR assay, microsatellite LOH study, and Southern blot analysis. Intragenic mutation of the VHL gene was found exclusively in clear-cell or variant-type RCCs at a frequency of 51% (104/202). Hypermethylation of the VHL promoter region was detected in an additional 11 clear-cell RCCs. Microsatellite analysis demonstrated that LOH of the VHL locus was found in 140/155 (90%) informative clear-cell RCCs. The VHL gene therefore seems to be inactivated in a two-hit manner by intragenic mutation or hypermethylation plus allelic loss in clear-cell RCC. Genomic rearrangement of the VHL gene detected by Southern analysis was not found (0/216 cases); this is in contrast to germ lines in which Southern aberrations consisted of 7-19% of the mutations. Clinicopathologic data demonstrated that VHL mutation/LOH did not vary according to tumor progression in clear-cell RCC, including tumor diameter, stage, grading, distant metastasis, and lymph node metastasis. Interestingly, VHL mutation was significantly less frequent in RCCs occurring in younger (< or = 55 years) than that in older (> or = 56 years) patients. These data suggested that the inactivation of the VHL tumor-suppressor gene is a specific genetic change in clear-cell RCC, and that it may occur at an early or first step in the clear-cell tumorigenic pathway rather than as a late event.     

Somatic mutations of the von Hippel -- Lindau disease tumour suppressor gene in non-familial clear cell renal carcinoma

Loss of heterozygosity (LOH) studies have suggested that somaticmutations of a tumour suppressor gene or genes on chromosome3p are a critical event In the pathogenesls of non-familialrenal cell carcinoma (RCC). Germllne mutations of the von Hippel— Lindau (VHL) disease gene predispose to early onsetand multifocal clear cell renal cell carcinoma, and the mechanismof tumorigenesls In VHL disease is consistent with a one-hitmutation model. To Investigate the role of somatic VHL genemutations in non-familial RCC, we analysed 99 primary RCC forVHL gene mutations by SSCP and heteroduplex analysis. SomaticVHL gene mutations were Identified In 30 of 65 (46%) sporadicRCC with chromosome 3p allele loss and one of 34 (3%) tumourswith no LOH for chromosome 3p. The VHL gene mutations were heterogeneous(17 frameshift deletions, eight missense mutations, four frameshiftinsertions, one nonsense and one splice site mutation), butno mutations were detected in the first 120 codons of clonedcoding sequence. Most RCCs with somatic VHL mutations (23 of27 (85%) informative cases) had chromosome 3p25 allele lossin the region of the VHL gene so that both alleles of the VHLgene had been inactivated as expected from a two–hit modelof tumorigenesis. Detailed histopathology was available for59 of the tumours investigated: 18 of 43 (42%) RCC with a clearcell appearance had a somatic VHL gene mutation but none of16 non–clear cell RCC (eight chromophilic, three chromophobeand five oncocytoma) (x²= 7.77, P<0.025). These results suggestthat somatic mutations of the VHL gene are a critical eventin the pathogenesis of non-familial clear cell renal carcinoma,but do not exclude a role for other chromosome 3p tumour suppressorgenes.     

散发性肾癌中VHL基因的两个单核苷酸多态位点分析和杂合性缺失检测

目的检测79例散发性肾癌中抑癌基因VHL内部的两个单核苷酶多态(single nucleotide polymorphism，SNP)位点并分析杂合性缺失(loss of heterozygosity，LOH)发生情况，探讨VHL基因LOH与肾癌临床病理特征的关系。方法从肿瘤和正常肾组织中提取DNA，应用聚合酶链反应-限制性片段长度多态性方法检测VHL基因5′端SNP位点rs779805和3′端SNP位点rs1642742的基因型。在两个位点的杂合子中进行LOH检测，并分析VHL基因LOH与临床病理特征的关系。结果我们计算了两个位点的基因型、基因频率、杂合度、多态信息含量等遗传学参数。综合两个位点发现杂合子29例．其中12例(41．4％)存在LOH。VHL基因LOH与肾癌发生年龄、性别、临床分期、病理分级无显著相关性。结论在散发性肾癌中，VHL基因LOH是肿瘤发生的重要机理，其发生率达41．4％，VHL基因LOH与肾癌分期、分级无关。     

Familial clear cell renal cell carcinoma (FCRC): clinical features and mutation analysis of the VHL, MET, and CUL2 candidate genes

Familial renal cell carcinoma (RCC) is genetically heterogeneous. Genetic predisposition to clear cell RCC (CCRCC) is a major feature of von Hippel-Lindau (VHL) disease (MIM 193300) and has rarely been associated with chromosome 3 translocations. In addition, familial papillary (non-clear cell) RCC may result from germline mutations in the MET proto-oncogene (MIM 164860). However, rare kindreds with familial CCRCC (FCRC) not linked to the VHL tumour suppressor gene have been described suggesting that further familial RCC susceptibility genes exist. To investigate the genetic epidemiology of FCRC, we undertook a clinical and molecular study of FCRC in nine kindreds with two or more cases of CCRCC in first degree relatives. FCRC was characterised by an earlier age at onset (mean 47.1 years, 52% of cases <50 years of age) than sporadic cases. These findings differ from the only previous report of two FCRC kindreds and have important implications for renal surveillance in FCRC. The molecular basis of CCRCC susceptibility was investigated in nine FCRC kindreds and seven isolated cases with features of possible genetic susceptibility to CCRCC (four bilateral CCRCC aged <50 years and three with unilateral CCRCC aged <30 years). No germline mutations were detected in the VHL or MET genes, suggesting that FCRC is not allelic with VHL disease or HPRC. As binding of the VHL gene product to the CUL2 protein is important for pVHL function, we then searched for germline CUL2 mutations. Although CUL2 polymorphisms were identified, no pathogenic mutations were detected. These findings further define the clinical features of FCRC and exclude a major role for mutations in VHL, MET, or CUL2 in this disorder.


Keywords: familial clear cell renal carcinoma; VHL; MET; CUL2     

青少年肾细胞癌的临床病理及分子遗传学研究

目的 探讨青少年肾细胞癌的临床病理特征、遗传学改变、鉴别诊断及预后.方法 对46例青少年肾细胞癌进行光镜观察及免疫组织化学染色,随访并复习相关文献.对46例肿瘤进行von Hippel-Lindau(VHL)基因区域杂合性缺失(LOH)及VHL基因突变筛查.结果 共诊断19例Xp11.2易位/TFE3基因融合相关性肾癌(Xp11 RCC)、9例透明细胞癌、17例乳头状肾细胞癌(PRCC)和1例不能分类肾细胞癌.19例Xp11 RCC均TFE3阳性,而TFEB阴性.8例肿瘤具有巢状和乳头状结构形态类似t(X;17)ASPL-TFE3型肾癌,6例肿瘤组织学类似t(X;1)PRCC-TFE3型肾癌,4例肿瘤形态像透明细胞癌,1例肿瘤组织学形态文献中未被检索到,表现为细胞核呈毛玻璃样,核仁不明显,可见核沟,肿瘤间质见大量黏液.LOH及VHL突变检测结果显示,仅1例透明细胞癌和1例2型PRCC存在LOH,并且该2型PRCC的VHL基因的一个剪切位点存在胚系突变,553+5 G→C.其余45例均未检测出VHL突变.统计学分析表明TFE3阳性肾细胞癌比TFE3阴性肾细胞癌更倾向于高病理分期(pT3/pT4),并且预后较差(P=0.035).结论 青少年肾细胞癌表现出不同的组织学形态以及分子遗传学背景.其中Xp11 RCC为最常见的肾癌亚型.TFE3阳性肾细胞癌的预后要差于TFE3阴性肾细胞癌.     

Role of chromosome 3p12-p21 tumour suppressor genes in clear cell renal cell carcinoma: analysis of VHL dependent and VHL independent pathways of tumorigenesis.

AIMS: Chromosome 3p deletions and loss of heterozygosity (LOH) for 3p markers are features of clear cell renal cell carcinoma but are rare in non-clear cell renal cell carcinoma. The VHL tumour suppressor gene, which maps to 3p25, is a major gatekeeper gene for clear cell renal cell carcinoma and is inactivated in most sporadic cases of this disease. However, it has been suggested that inactivation of other 3p tumour suppressor genes might be crucial for clear cell renal cell carcinoma tumorigenesis, with inactivation (VHL negative) and without inactivation (VHL positive) of the VHL tumour suppressor gene. This study set out to investigate the role of non-VHL tumour suppressor genes in VHL negative and VHL positive clear cell renal cell carcinoma. METHODS: Eighty two clear cell renal cell carcinomas of known VHL inactivation status were analysed for LOH at polymorphic loci within the candidate crucial regions for chromosome 3p tumour suppressor genes (3p25, LCTSGR1 at 3p21.3, LCTSGR2 at 3p12 and at 3p14.2). RESULTS: Chromosome 3p12-p21 LOH was frequent both in VHL negative and VHL positive clear cell renal cell carcinoma. However, although the frequency of 3p25 LOH in VHL negative clear cell renal cell carcinoma was similar to that at 3p12-p21, VHL positive tumours demonstrated significantly less LOH at 3p25 than at 3p12-p21. Although there was evidence of LOH for clear cell renal cell carcinoma tumour suppressor genes at 3p21, 3p14.2, and 3p12, both in VHL negative and VHL positive tumours, the major clear cell renal cell carcinoma LOH region mapped to 3p21.3, close to the lung cancer tumour suppressor gene region 1 (LCTSGR1). There was no association between tumour VHL status and tumour grade and stage. CONCLUSIONS: These findings further indicate that VHL inactivation is not sufficient to initiate clear cell renal cell carcinoma and that loss of a gatekeeper 3p21 tumour suppressor gene is a crucial event for renal cell carcinoma development in both VHL negative and VHL positive clear cell renal cell carcinoma.     

Expression of HGF/SF and Met protein is associated with genetic alterations of VHL gene in primary renal cell carcinomas

We analyzed the genetic alterations of VHL, HGF/SF, and Met genes and the expression pattern of HGF/SF and Met protein in 26 renal cell carcinomas (RCCs). We found five mutations of the VHL gene and frequent LOH (50%) only in non-papillary clear cell RCC. We found six cases in which the CpG island of VHL was methylated. In addition, one missense mutation of the HGF/SF gene was detected in clear cell RCC. HGF/SF and Met protein were expressed in 84.6% and 80.7% of RCCs, respectively. All of the cases with the genetic alterations of VHL or HGF/SF demonstrated strong expression of HGF/SF and Met protein in RCC cells. Statistically, genetic alterations of VHL and HGF/SF were significantly correlated with HGF/SF and Met expression (Fisher's exact test, p=0.022 and p=0.0070). Thus, these results strongly suggest that the expression of HGF/SF and Met protein is closely associated with the genetic alterations of VHL and HGF/SF in primary RCCs.     

Allelic deletion and mutation of the von Hippel-Lindau (VHL) tumor suppressor gene in pancreatic microcystic adenomas.

An association between pancreatic microcystic (serous) adenomas (MCAs) and von Hippel-Lindau (VHL) disease has been suggested. However, genetic alterations of the VHL gene in MCAs of the pancreas have never been reported. In this study, we performed genetic analysis of 12 pancreatic MCAs. In 2 cases, VHL disease was documented clinically, and 10 cases were sporadic. For LOH analysis, tumor and normal pancreatic cells were procured from formalin-fixed, paraffin-embedded material using tissue microdissection. After DNA extraction, the samples were amplified by polymerase chain reaction using the polymorphic markers D3S2452, D3S1110, D3S192, and D3S656. In addition, the sporadic tumors were analyzed for VHL gene mutations using probes 3b/10b and K55/K56. Both MCAs associated with VHL disease showed LOH with at least one of the microsatellite markers tested. Among the 10 sporadic cases, 7 tumors showed LOH at the VHL gene locus. A somatic VHL gene mutation on exon 2 was documented in one sporadic case. The study provides the first direct genetic evidence for the role of the VHL gene in MCA tumorigenesis. Furthermore, VHL gene alterations may be detected in both VHL-associated and sporadic pancreatic MCAs.     

Imprinted DLK1 is a putative tumor suppressor gene and inactivated by epimutation at the region upstream of GTL2 in human renal cell carcinoma

A common deletion at chromosomal arm 14q32 in human renal cell carcinoma (RCC) prompted us to explore a tumor suppressor gene (TSG) in this region. We report that imprinted DLK1 at 14q32, a regulator of adipocyte differentiation, is a candidate TSG in RCCs. DLK1 expression was lost in 39 out of 50 (78%) primary RCC tissues, whereas expression of DLK1 was maintained in every normal kidney tissue examined. DLK1 was expressed in only one of 15 (7%) RCC-derived cell lines. In order to see the biological significance of DLK1 inactivation in RCCs, we tested the effect of restoration of DLK1 in RCC cell lines, using a recombinant retrovirus containing the gene. Reintroduction of DLK1 into DLK1-null RCC cell lines markedly increased anchorage-independent cell death, anoikis and suppressed tumor growth in nude mice. We then investigated the underlying mechanisms for DLK1 inactivation in RCCs. We found loss of heterozygosity at this region in 12 out of 50 RCC tissues (24%). To explore the role of epigenetic regulation of DLK1 inactivation in RCCs, we conducted methylation analysis of the upstream region and the gene body of DLK1. We could not find a differentially methylated region in either the upstream region or the gene body of DLK1. However, we found that gain of methylation upstream of GTL2, a reciprocal imprinted gene for DLK1, is a critical epigenetic alteration for the inactivation of DLK1 in RCCs. The present data have shown that gain of methylation upstream of the untranslated GTL2 leads to pathological downregulation of DLK1 in RCCs.     

Analysis of the Birt-Hogg-Dubé (BHD) tumour suppressor gene in sporadic renal cell carcinoma and colorectal cancer

Germline mutations in the BHD gene cause the dominantly inherited cancer susceptibility disorder, Birt-Hogg-Dubé (BHD) syndrome. Individuals with BHD are reported to have an increased risk of renal cell carcinoma (RCC) and of colorectal polyps and cancer. The BHD gene maps to 17p11.2, and to investigate whether somatic inactivation of the BHD gene region is implicated in the pathogenesis of sporadic RCC and colorectal cancer (CRC), we performed mutation analysis in 30 RCC primary tumours and cell lines, and 35 CRCs and cell lines. A somatic missense mutation (Ala444Ser) with loss of the wild type allele (consistent with a two hit mechanism of tumorigenesis) was detected in a primary clear cell RCC, and a further missense mutation (Ala238Val) was identified in a clear cell RCC cell line for which matched normal DNA was not available. A somatic missense substitution (Arg392Gly) was identified in a primary CRC, and the same change was detected in three RCCs (all oncocytomas) for which matched normal DNA was not available. A germline Arg320Gln missense variant detected in a primary CRC was not detected in 40 control individuals or in a further 159 familial and sporadic CRC cases. However, AA homozygotes for an intronic single nucleotide polymorphism (c.1517+6 G-->A) were under-represented in familial cases compared with controls (p = 0.03). For some tumour suppressor genes, epigenetic silencing is a more common mechanism of inactivation than somatic mutations. However, we did not detect evidence of epigenetic silencing of BHD in 19 CRC and RCC cell lines, and BHD promoter region hypermethylation was not detected in 20 primary RCCs. These findings suggest that BHD inactivation occurs in a subset of clear cell RCC and CRC.     

Somatic von Hippel-Lindau disease gene mutation in clear-cell renal carcinomas associated with end-stage renal disease/acquired cystic disease of the kidney

It has been documented that renal cell carcinomas (RCCs) occur frequently in patients treated with long-term dialysis, especially in cases of end-stage renal disease (ESRD)/acquired cystic disease of the kidney (ACDK). To address the molecular pathogenesis of ESRD/ACDK-associated RCCs, we examined 14 RCCs (7 clear-cell and 7 papillary carcinomas) in patients receiving dialysis for somatic mutations of the von Hippel-Lindau disease (VHL) gene as well as of the tyrosine kinase domain of the MET oncogene. Direct sequencing analyses revealed that three tumors exhibited VHL frameshifts (618delA, 386-395del10-bp, and 723-724insTC). One of the VHL mutated tumors showed additional loss of heterozygosity at the VHL gene locus. Histopathologic and clinical data demonstrated that the three tumors having VHL mutations were clear-cell RCCs occurring in ESRD with 55, 106, and 156 months of dialysis history, respectively. We did not find any tumors with mutations in the tyrosine kinase domain of the MET. These results demonstrated that the VHL tumor-suppressor gene is also involved in a subset of clear-cell RCCs occurring in ESRD/ACDK, as in the case of sporadic clear-cell RCCs. However, mutations of the MET oncogene could not be found in the seven ESRD/ACDK-associated papillary RCCs examined.     

Molecular cytogenetic characterization of early and late renal cell carcinomas in von Hippel-Lindau disease

Deletions of 3p25, gains of chromosomes 7 and 10, and isochromosome 17q are known cytogenetic aberrations in sporadic renal cell carcinoma (RCC). In addition, a majority of RCCs have loss of heterozygosity (LOH) of the Von Hippel-Lindau (VHL) gene located at chromosome band 3p25. Patients who inherit a germline mutation of the VHL gene can develop multifocal RCCs and other solid tumors, including malignancies of the pancreas, adrenal medulla, and brain. VHL tumors follow the two-hit model of tumorigenesis, as LOH of VHL, a classic tumor suppressor gene, is the critical event in the development of the neoplastic phenotype. In an attempt to define the cytogenetic aberrations from early tumors to late RCC further, we applied spectral karyotyping (SKY) to 23 renal tumors harvested from 6 unrelated VHL patients undergoing surgery. Cysts and low-grade solid lesions were near-diploid and contained 1-2 reciprocal translocations, dicentric chromosomes, and/or isochromosomes. A variety of sole numerical aberrations included gains of chromosomes 1, 2, 4, 7, 10, 13, 21, and the X chromosome, although no tumors had sole numerical losses. Three patients shared a breakpoint at 2p21-22, and three others shared a dicentric chromosome 9 or an isochromosome 9q. In contrast to the near-diploidy of the low-grade lesions, a high-grade lesion and its nodal metastasis were markedly aneuploid, revealed loss of VHL by fluorescence in situ hybridization (FISH), and contained recurrent unbalanced translocations and losses of chromosome arms 2q, 3p, 4q, 9p, 14q, and 19p as demonstrated by comparative genomic hybridization (CGH). By combining SKY, CGH, and FISH of multiple tumors from the same VHL kidney, we have begun to identify chromosomal aberrations in the earliest stages of VHL-related renal cell tumors. Our current findings illustrate the cytogenetic heterogeneity of different VHL lesions from the same kidney, which supports the multiclonal origins of hereditary RCCs. Published 2001 Wiley-Liss, Inc.     

Characterization of a 3;6 translocation associated with renal cell carcinoma

The most frequent cause of familial clear cell renal cell carcinoma (RCC) is von Hippel-Lindau disease and the VHL tumor suppressor gene (TSG) is inactivated in most sporadic clear cell RCC. Although there is relatively little information on the mechanisms of tumorigenesis of clear cell RCC without VHL inactivation, a subset of familial cases harbors a balanced constitutional chromosome 3 translocation. To date nine different chromosome 3 translocations have been associated with familial or multicentric clear cell RCC; and in three cases chromosome 6 was also involved. To identify candidate genes for renal tumorigenesis we characterized a constitutional translocation, t(3;6)(q22;q16.1) associated with multicentric RCC without evidence of VHL target gene dysregulation. Analysis of breakpoint sequences revealed a 1.3-kb deletion on chromosome 6 within the intron of a 2 exon predicted gene (NT_007299.434). However, RT-PCR analysis failed to detect the expression of this gene in lymphoblast, fibroblast, or kidney tumor cell lines. No known genes were disrupted by the translocation breakpoints but several candidate TSGs (e.g., EPHB1, EPHA7, PPP2R3A RNF184, and STAG1) map within close proximity to the breakpoints.     

Copy number profiling in von Hippel-Lindau disease renal cell carcinoma

Germline mutations in the VHL tumor suppressor gene cause von Hippel-Lindau (VHL) disease and somatic VHL mutations occur in the majority of clear cell renal cell carcinoma (cRCC). To compare copy number abnormalities (CNAs) between cRCC from VHL patients and sporadic cRCC cases without detectable somatic VHL mutations, we analyzed 34 cRCC with Affymetrix 250K arrays. To increase the power of the study, we then combined our results with those of a previously published study and compared CNAs in VHL and non-VHL related cRCC using the genomic identification of significant targets in cancer (GISTIC) program. In VHL, cRCC GISTIC analysis identified four statistically significant regions of copy number gain and four statistically significant regions of deletion that occurred in >10% of tumors analyzed. Sporadic cRCC without detectable VHL mutations had, on average, more copy number abnormalities than VHL cRCC though the most common regions of loss/gain (e.g., 3p and 14q loss and 5q gain) were present in both tumor sets. However, CNAs on chromosome arms 7p (gain) and 8p (loss) were only detected in VHL RCC. Although individual copy number abnormality peaks contained clear candidate cancer genes in some cases (e.g., the 3p loss peak in VHL cRCC contained only six genes including VHL), most peaks contained many genes. To date, only a minority of the candidate genes included in these peaks have been analyzed for mutation or epigenetic inactivation in cRCC but TNFRSF10C and DUSP4 map to the 8p region deleted in VHL cRCC and TP53 and HIF2A (EPAS1) mapped to CNA loss and gain peaks (chromosomes 17 and 2, respectively) detected in sporadic VHL wild-type cRCC.     

Allelic loss at 10q23.3 but lack of mutation of PTEN/MMAC1 in chromophobe renal cell carcinoma.

Chromophobe renal cell carcinoma (RCC) is characterized by loss of multiple chromosomes including chromosome 10. This study was undertaken to determine the LOH at the PTEN/MMAC1 locus (chromosome band 10q23.3) and to search for gene mutations in 15 chromophobe, 50 conventional, and 10 papillary RCCs as well as in 10 renal oncocytomas. Loss of heterozygosity (LOH) wa seen at all informative loci in all chromophobe RCCs and in two conventional RCCs. We did not find mutations by analyzing exon 1 to 9 of the PTEN/MMAC1 gene using the PCR-SSCP technique in tumors with LOH at 10q23.3.     

Allelic deletions of the VHL gene detected in multiple microscopic clear cell renal lesions in von Hippel-Lindau disease patients.

Patients with von Hippel-Lindau (VHL) disease develop a spectrum of bilateral clear-cell renal lesions including cysts and renal cell carcinomas (RCCs). VHL gene deletions have been previously reported in VHL-associated macroscopic RCC. Although histological analysis suggests that microscopic cystic lesions in the VHL patients may represent precursors of the RCC, there is at present no direct molecular evidence of their relationship. To investigate the relationship between cystic lesions and RCC, 26 microdissected archival renal lesions from two VHL disease patients were studied for loss of heterozygosity at the VHL gene locus using polymerase chain reaction single-strand conformation polymorphism analysis. The renal lesions included 2 benign cysts, 5 atypical cysts, 5 microscopic RCCs in situ, 5 cysts lined by a single layer of cells, in which RCCs in situ were developing, and 2 microscopic and 7 macroscopic RCCs. Except for a single benign cyst, 25 of 26 renal lesions showed nonrandom allelic loss of the VHL gene. In either of the 2 patients, the same VHL allele was deleted in all of the lesions tested, indicating loss of the wild-type allele and retention of the inherited, mutated VHL allele. The results suggest that all clear-cell lesions in the VHL kidney represent neoplasms and that the loss of the VHL gene occurs early in their development. Atypical and benign cysts most likely represent the initial phenotype in malignant transformation to the RCC.     

Expression of fibronectin and HIF-1alpha in renal cell carcinomas: relationship to von Hippel-Lindau gene inactivation

The von Hippel-Lindau (VHL) tumor suppressor gene (TSG) at 3p25 is mutated in approximately 50% of conventional (clear cell) renal cell carcinomas (cRCC). VHL normally regulates the ubiquitin-mediated proteolysis of hypoxia-inducible factor 1alpha (HIF-1alpha), and VHL inactivation results in increased cellular HIF-1alpha expression. VHL protein (pVHL) also interacts with fibronectin (Fn) and VHL inactivation results in defective Fn extracellular matrix assembly. The present study investigated the immunohistochemical (IHC) staining for Fn and HIF-1alpha in 11 cRCC and the relationship of the staining to VHL inactivation by gene deletion, mutation, or hypermethylation. Evidence for VHL inactivation by 3p deletions and VHL mutations were found in six tumors. Fn-positive IHC staining of tumor cells and negative to weak staining of extracellular stroma was found in five cases having exon 1 or exon 2 mutations. In contrast, Fn staining was absent in tumor cells and positive in the stroma of five tumors without VHL inactivation and in one tumor with a C-terminal exon 3 mutation. HIF-1alpha tumor cell staining was present in the cRCC with VHL inactivation but was also present in two tumors having 3p deletions but neither mutation nor hypermethylation of VHL. These two cRCC showed a tumor cell-negative and stroma-positive pattern of Fn staining. The findings indicate that VHL inactivation plays a role in the development of some cRCC by altering Fn cell--stroma relationships. They also suggest that some C-terminal mutations may not interfere with Fn assembly and that a 3p TSG in addition to VHL influences HIF-1alpha degradation.     

Loss of heterozygosity of DNA repair gene, hOGG1, in renal cell carcinoma but not in renal papillary adenoma

The kidney is constantly exposed to free radicals due to its active metabolism and processing of toxic metabolites. Among 20 or so free radical-induced DNA lesions, 8-oxoquanine is the most abundant and is potentially mutagenic if not sufficiently removed. The human 8-oxoquanine DNA glycosylase 1 ( hOGG1 ) gene repairs 8-oxoguanine and resides at 3p25–26, which has frequent loss of heterozygosity (LOH) in clear cell–renal cell carcinoma (CC-RCC). Even though some studies found similar genetic alterations between renal papillary adenomas (PA) and papillary RCC (PRCC), no studies have been conducted to compare the alterations of hOGG1 gene in PA, PRCC and CC-RCC. To further explore the relationship between CC-RCC, PRCC and PA at the genetic level LOH of hOGG1 gene was investigated in these three groups. It was found that 8/8 PRCC (100%) and 8/9 CC-RCC (88%) had evidence of hOGG1 LOH, whereas all four PA (0%) were devoid of hOGG1 LOH. It is concluded that deletion of hOGG1 gene occurs commonly in PRCC and CC-RCC but not in renal cortical PA. Further studies are warranted to further explore the exact roles of hOGG1 gene in the development and progression of RCC.