Von Hippel-Lindau Mutations Research Articles

Anoikis Disruption of Focal Adhesion-Akt Signaling Impairs Renal Cell Carcinoma

BackgroundQuinazoline-based α1-adrenoceptor antagonists suppress tumor growth by inducing apoptosis via an α1-adrenoceptor-independent action. Anoikis is a unique mode of apoptosis consequential to insufficient cell-matrix interactions. ObjectiveThis study investigated the apoptotic effect of novel quinazoline-based compounds on human renal cancer cells. Design, setting, and participantsTwo cell lines were used: renal cell carcinoma (RCC) 786-0, harboring a von Hippel-Lindau (VHL) tumor-suppressor gene mutation with a highly angiogenic phenotype, and Caki cells (no VHL mutation). MeasurementsThe lead compound DZ-50 (10μM) led to significant inhibition of tumor-cell adhesion, migration, and invasion at a lower dose than doxazosin (25μM) in both RCC lines. Results and limitationsDoxazosin induced death-receptor-mediated apoptosis, while DZ-50 led to anoikis via targeting of the focal adhesion complex and AKT signaling that subsequently increased RCC susceptibility to caspase-8-mediated apoptosis. Both quinazoline compounds, doxazosin and DZ-50, significantly reduced RCC metastatic potential in vivo. ConclusionsQuinazoline-based drugs trigger anoikis in RCC by targeting the focal adhesion survival signaling. This potent antitumor action against human RCC suggests a novel quinazoline-based therapy targeting renal cancer.

Molecular basis of von Hippel-Lindau syndrome in Chinese patients.

Von Hippel-Lindau (VHL) syndrome is an autosomal dominant familial cancer syndrome predisposing the affected individuals to multiple tumours in various organs. The genetic basis of VHL in Southern Chinese is largely unknown. In this study, we characterized the mutation spectrum of VHL in nine unrelated Southern Chinese families. Nine probands with clinical features of VHL, two symptomatic and eight asymptomatic family members were included in this study. Prenatal diagnosis was performed twice for one proband. Two probands had only isolated bilateral phaeochromocytoma. The VHL gene was screened for mutations by polymerase chain reaction, direct sequencing and multiplex ligation-dependent probe amplification (MLPA). The nine probands and the two symptomatic family members carried heterozygous germline mutations. Eight different VHL mutations were identified in the nine probands. One splicing mutation, NM_000551.2: c.463+1G > T, was novel. The other seven VHL mutations, c.233A > G [p.Asn78Ser], c.239G > T [p.Ser80Ile], c.319C > G [p.Arg107Gly], c.481C > T [p.Arg161X], c.482G > A [p.Arg161Gln], c.499C > T [p.Arg167Trp] and an exon 2 deletion, had been previously reported. Three asymptomatic family members were positive for the mutation and the other five tested negative. In prenatal diagnosis, the fetuses were positive for the mutation. Genetic analysis could accurately confirm VHL syndrome in patients with isolated tumours such as sporadic phaeochromocytoma or epididymal papillary cystadenoma. Mutation detection in asymptomatic family members allows regular tumour surveillance and early intervention to improve their prognosis. DNA-based diagnosis can have an important impact on clinical management for VHL families.

Development and Characterization of Clinically Relevant Tumor Models From Patients With Renal Cell Carcinoma

BackgroundAnimal models are instrumental in understanding disease pathophysiology and mechanisms of therapy action and resistance in vivo. ObjectiveTo establish and characterize a panel of mouse models of renal cell carcinoma (RCC) derived from patients undergoing radical nephrectomy. Design, setting, and participantsIn vivo and in vitro animal experiments. MeasurementsTumor tissues obtained during surgery were implanted into the subcutaneous space of female BALB/c nude mice and serially passaged into new mice. Tumors were characterized by histology, short tandem repeat (STR) fingerprinting, von Hippel-Lindau (VHL) gene sequencing, and single nucleotide polymorphism (SNP) analysis. Tumor-bearing mice were treated with sunitinib or everolimus. Primary cell cultures were derived from patient tumors and transfected with a lentivirus carrying the luciferase gene. Four subcutaneous xenograft mouse models were developed, representing papillary type 1, papillary type 2, clear cell, and clear cell with sarcomatoid features RCC. Results and limitationsRCC mouse models were established from four patients with distinct histologies of RCC. Tumor growth was dependent on histologic type, the size of the implanted tumor chip, and the passage number. Mouse tumors accurately represented their respective original patient tumors, as STR fingerprints were matching, histology was comparable, and SNP profiles and VHL mutation status were conserved with multiple passages. Bioluminescence imaging results were commensurate with subcutaneous xenograft growth patterns. Mice treated with sunitinib and everolimus exhibited an initial response, followed by a later stage of resistance to these agents, which mimics the clinical observations in patients with RCC. ConclusionsWe developed four mouse xenograft models of RCC with clear-cell and papillary histologies, with stable histologic and molecular characteristics. These models can be used to understand the basic biology of RCC as well as response and resistance to therapy.

Expression of the Hypoxia-Inducible Factors In the AML and MDS: Is Not Associated with the Von Hippel-Lindau Gene

AbstractAbstract 5114The hypoxia-inducible factor (HIF) is a transcriptional factor with important roles in tumor biology, which activates transcription of genes encoding glucose transporters, glycolytic enzymes, and vascular endothelial growth factor. The VHL (von Hippel-Lindau) gene normally regulates ubiquitin mediated proteolysis of HIF-1a. VHL inactivation blocks HIF-1 proteolysis, resulting in increased HIF-1 expression. In the previous study, the expression of HIF-1a was detected in children ALL and NHL. To clarify the possible involvement of the HIF-1a and VHL gene in the development and progression of acute myeloid leukemia (AML) and myelodysplastic syndrome (MDS), we analyzed the mutation and methylation of the VHL gene in 98 patients (54 AML and 44 MDS). The mutations in VHL gene was examined by direct exons sequence and the methylation status of the promoter region was determined using methylation-specific polymerase chain reaction (MSP). In addition, we examined the expression of HIF-1a in 44 of these patients (25 AML and 18 MDS) through the immunoblotting. VHL mutations were identified only in one patient with AML. However, no mutation was detected in the coding region of the VHL gene in MDS. Meanwhile the methylation of VHL gene was not found in the AML and MDS. But the expression of HIF-1a was found in 10 (66.7%) of 25 patients with AML and 5 (38.5%) of 18 patients with MDS. There is no significant correlation between the expression of HIF-1a and the VHL gene. Our primary date support that the HIF-1a may be involved in the development and progression of AML and MDS, but is not associated with the VHL gene. Disclosures:No relevant conflicts of interest to declare.

The relationship of erythropoietin overexpression with von Hippel-Lindau tumour suppressor gene mutations between hypoxia-inducible factor-1α and -2α in sporadic clear cell renal carcinoma

Decreased levels of von Hippel-Lindau (VHL) tumour suppressor protein are associated with up-regulation of hypoxia-inducible factor (HIF), leading to increased tumour proliferation, angiogenesis and progression. The role of erythropoietin (EPO), a target gene for HIF, remains unknown for sporadic clear cell renal cell carcinoma (sCCRCC). In this study, we determined expression levels of EPO, and its correlation with VHL mutations and HIF-1α and HIF-2α expression in 82 patients identified with sCCRCC following nephrectomy. We identified VHL gene alterations using multiplex polymerase chain reaction, purifying products of polymerase chain reaction, and direct sequencing. Immunohistochemical staining for HIF-1α, HIF-2α and EPO was performed for tumour and corresponding normal tissues. Data were analyzed with respect to clinicopathological factors. EPO was detected in 87.8% of sCCRCC tumours versus 7.3% for normal tissues. EPO expression was related to tumours demonstrating VHL gene abnormalities. Of specimens with VHL alterations 95.6% tested positive for EPO, versus 78.3% when VHL gene expression was normal (P<0.01). EPO was identified in 96.2 and 94.2% of HIF-1α and HIF-2α positive specimens, respectively, compared to 72.4 and 53.8% for HIF-1α and HIF-2α negative groups (p<0.01). Moreover, EPO expression correlated significantly with increasing nuclear grade (p<0.05). HIF-2α was identified in 84.1% of sCCRCC, compared to 64.6% for HIF-1α. Expression of HIF-1α, HIF-2α and EPO is common in sCCRCC. Although both forms of HIF up-regulate expression of EPO, the relationship to HIF-2α appears to be more pronounced. The VHL-HIF-EPO pathway requires further study, as it may represent a potential molecular target for therapy of sCCRCC.

The VHL-dependent regulation of microRNAs in renal cancer

BackgroundThe commonest histological type of renal cancer, clear cell renal cell carcinoma (cc RCC), is associated with genetic and epigenetic changes in the von Hippel-Lindau (VHL) tumour suppressor. VHL inactivation leads to induction of hypoxia-inducible factors (HIFs) and a hypoxic pattern of gene expression. Differential levels of specific microRNAs (miRNAs) are observed in several tumours when compared to normal tissue. Given the central role of VHL in renal cancer formation, we examined the VHL-dependent regulation of miRNAs in renal cancer.MethodsVHL-dependent miRNA expression in cc RCC was determined by microarray analysis of renal cell line RCC4 with mutated VHL (RCC4-VHL) and reintroduced wild-type VHL (RCC4 + VHL). Five miRNAs highly upregulated in RCC4 + VHL and five miRNAs highly downregulated in RCC4 + VHL were studied further, in addition to miR-210, which is regulated by the HIF-VHL system. miRNA expression was also measured in 31 cc RCC tumours compared to adjacent normal tissue.ResultsA significant increase in miR-210, miR-155 and miR-21 expression was observed in the tumour tissue. miR-210 levels also showed a correlation with a HIF-regulated mRNA, carbonic anhydrase IX (CAIX), and with VHL mutation or promoter methylation. An inverse correlation was observed between miR-210 expression and patient survival, and a putative target of miR-210, iron-sulfur cluster assembly protein (ISCU1/2), shows reciprocal levels of mRNA expression in the tumours.ConclusionsWe have identified VHL-regulated miRNAs and found that for some the regulation is HIF-dependent and for others it is HIF-independent. This pattern of regulation was also seen in renal cancer tissue for several of these miRNAs (miR-210, miR-155, let-7i and members of the miR-17-92 cluster) when compared with normal tissue. miR-210 showed marked increases in expression in renal cancer and levels correlated with patient survival. The inverse correlation between miR-210 levels and ISCU1/2 provides support for the hypothesis that ISCU1/2 is a target of miR-210 and that it may contribute to the anaerobic respiration seen in renal (and other) tumours.See Commentary: http://www.biomedcentral.com/1741-7015/8/65

Clinicopathologic and Molecular Genetic Study of Renal Cell Carcinoma Occurring in Teenagers

To investigate clinicopathological features, molecular genetic characteristics, differential diagnoses and prognosis of renal cell carcinoma in teenagers. Microscopic and immunohistochemical features of 46 cases of renal cell carcinomas in teenagers were reviewed along with the clinical follow-up data. Loss of heterozygosity (LOH), analysis of von Hippel-Lindau (VHL) gene and screening for VHL gene mutations were performed in all of the tumors. There were 19 Xp11.2 translocations/TFE3 gene fusions renal clear cell carcinomas (Xp11 RCCs), 9 chromophobe renal cell carcinomas (CCRCCs), 17 papillary renal cell carcinomas (PRCCs), and 1 unclassified renal cell carcinoma (RCC). All of the 19 Xp11.2 translocation RCCs showed a moderate to strong immunoreactivity for TFE, however, no TFEB expression was obtained. There were 4 histological patterns in the Xp11 RCC cases including: 8 tumors possessing a nested to papillary architecture resembling to the t(X;17) ASPL-TFE3 phenotype; 6 tumors possessing a morphologic feature like the t(X;1) PRCC-TFE3 phenotype; 4 cases morphologically resembling to clear cell RCC; and 1 Xp11 RCC case, with a special morphologic feature not searched yet in the literature, including a ground glass appearance of the nuclei accompanying occasionally with grooves on the nuclear surface; nucleoli inconspicuous with accumulation of abundant mucin-like substance in the stroma. VHL gene analysis revealed deletions at 3p25-26 in one clear cell RCC and one papillary type 2 RCC. The papillary type 2 RCC had also a family history of VHL disease, with a germline G→C mutation at a splicing site of position 553+5. There were no VHL mutations detected in the remaining 45 RCCs. Statistical analysis of tumor stage and outcome revealed that TFE+ RCCs of teen-agers were more frequently associated with a higher pT3/pT4 stage and a poorer outcome than that of the TFE-RCCs (P < 0.05). RCCs of the teenagers have a different morphologic spectrum and genetic background from the RCCs seen in adults. Among RCCs of the teen-agers, Xp11.2 translocation tumors are the most common RCCs and have a poorer prognosis than that of the TFE-RCCs.

Pheochromocytoma in a 2.75‐year‐old‐girl with a germline von Hippel–Lindau mutation Q164R

Pheochromocytomas are rare tumors of the adrenal gland occurring sporadically or as part of familial cancer syndromes. Here we report on the case of a pheochromocytoma due to the germline missense mutation c.491A>G (Q164R) in exon 3 of the von Hippel-Lindau gene in a girl as young as 2.75 years. Extended analyses of her relatives showed that the mutation occurred de novo in the patient's father who was subsequently diagnosed with bilateral pheochromocytomas and a retinal angioma. To the best of our knowledge, this is the youngest patient presenting with pheochromocytoma so far described in the literature. The same VHL mutation has been reported in a patient who developed a pheochromocytoma at the age of 10 years; therefore, for known VHL Q164R mutation carriers, we suggest screening for pheochromocytoma beginning at 2 years of age.

Endolymphatic Sac Tumors in von Hippel-Lindau Disease

To illustrate the diagnostic and pathophysiologic issues of endolymphatic sac tumors (ELSTs) and its clinical association with von Hippel-Lindau (VHL) disease and to demonstrate the interest of genetic testing in such cases. Retrospective analysis of 3 cases of ELST with VHL in 3 different clinical and prognostic situations. The first case was diagnosed on the concomitant finding of a central nervous system lesion. The familial genetic testing revealed the presence of the VHL mutation in an asymptomatic daughter, which justified regular follow-up. In the second case of known VHL syndromic disease, the pathophysiologic role of the endolymphatic sac was questioned, with vertigo as the initial, unique symptom of ELST. In the third case, a giant hypervascularized ELST, initially diagnosed as jugular paraganglioma, was the unique manifestation of VHL disease. The young age of the patient could explain the absence of other tumors. Diagnosis of ELSTs may be difficult especially when the original site of the lesion cannot be clearly identified. Such tumors may be revealed or may develop with VHL disease. On presentation of a lytic, vascularized tumor of the posterior face of the petrous bone, clinicians should systematically search for other manifestations of VHL disease and propose a VHL genetic testing for patients, and relatives in case of a positive test, to detect early asymptomatic other tumors. The type of VHL mutation might predict the aggressiveness.

Prognostic and predictive biomarkers in renal cell carcinoma

With the recent advances in targeted therapies, biomarkers in renal cell carcinoma (RCC) continue to be developed. Historically, information regarding prognosis has come from clinicopathologic variables, however in recent years much research has focused on the molecular basis of renal cell cancer. The discovery of reliable biomarkers in RCC could have an important impact on diagnosis, prognosis, and prediction of therapeutic benefit. To date, most biomarker research has centered on byproducts of the von Hippel-Lindau (VHL) pathway including VHL mutations, vascular endothelial growth factor (ligands and receptors), hypoxia-inducible factor, and carbonic anhydrase IX. This review examines these potential biomarkers, biomarker prognostic models, and molecular expression profiles in the field of renal cell carcinoma.

Molecularly genetic analysis of von Hippel-Lindau associated central nervous system hemangioblastoma

Von Hippel-Lindau (VHL) disease is an autosomal dominant inherited cancer predisposition syndrome, characterized by development of a variety of neoplasms in multiple organs. Central nervous system hemangioblastoma (CHB) is the most common manifestation of VHL disease. The germline mutations in the VHL tumor suppressor gene are responsible for the inherited cancer predisposition syndrome. To expand the VHL mutation data and to investigate the tumorigenesis of VHL-associated CNS hemangioblastoma, 24 CHB tissue samples and blood samples of 14 patients from 10 Chinese VHL families were collected and subjected to molecular genetic analysis. Six distinctive germline mutations were identified, and the 601 G to C (Val130Phe) mutation is reported for the first time. Somatic mutations analysis of the VHL gene in VHL-associated CHB showed that loss of heterozygosity (LOH) occurred in more than half of the cases. In addition, expression of the ZAC1 tumor suppressor gene protein was studied using immunohistochemistry staining in CHB tissues with a specific polyclonal antibody. The ZAC1 protein was lost in all CHB. Our data exhibited high frequency of LOH of ZAC1 gene in VHL-associated CHB, indicating that ZAC1 may have a role in tumorigenesis of VHL-associated CHB.

Body Mass Index and von Hippel-Lindau Gene Mutations in Clear-cell Renal Cancer: Results of the Netherlands Cohort Study on Diet and Cancer

Body mass index (BMI) is an important risk factor for clear-cell renal cancer (cc-RCC). A common molecular alteration in cc-RCC is loss-of-function of the von Hippel-Lindau (VHL) gene. We evaluated the association between BMI and VHL mutations in cc-RCC by using data from the Netherlands Cohort Study (NLCS), a prospective study, which comprises 120,852 persons. After 11.3 years of follow-up, 337 incident RCC cases were identified; 185 cc-RCC cases were included for analyses. A high BMI at baseline was associated with an increased risk of cc-RCC with or without VHL mutations (per 1 kg/m(2): hazard ratio [HR] = 1.09, 95% confidence interval [CI]: 1.02-1.16 and HR = 1.08, 95%CI: 1.01-1.15, respectively). BMI at age 20 was only associated with an increased risk of cc-RCC with VHL mutations (per 1 kg/m(2): HR =1.09, 95% CI: 1.03-1.16). In contrast, BMI gain since age 20 was only associated with an increased risk in VHL wild-type cases (per 1 kg/m(2): HR = 1.10, 95% CI: 1.03-1.19). Our findings indicate that BMI may be differently associated with subtypes of RCC based on VHL mutations.

Alterations in VHL as potential biomarkers in renal-cell carcinoma

Germ line mutations in the VHL tumor-suppressor gene cause von Hippel-Lindau (VHL) disease, a hereditary neoplastic disease associated with clear-cell renal-cell carcinomas (ccRCCs), central nervous system hemangioblastomas and pheochromocytomas. Disruption of VHL, by somatic mutation, hypermethylation of its promoter or chromosomal loss, is also seen in the majority of cases of sporadic ccRCC. The protein product of VHL, pVHL, has multiple functions, the best-documented of which relates to its ability to target hypoxia-inducible factors (HIFs) for polyubiquitination and proteasomal degradation through its role in substrate recognition as part of a ubiquitin ligase complex. Consequently, pVHL-defective ccRCCs overexpress mRNAs that are under the transcriptional control of HIF. Drugs that modulate the downstream targets of the pVHL/HIF pathway, including sunitinib, sorafenib, temsirolimus and bevacizumab, have proven benefit in treating ccRCC. In VHL disease, clear evidence supports strong genotype-phenotype correlations, but the situation in sporadic ccRCC is less clear. Data indicate that VHL alterations have a potential role as prognostic and predictive markers in ccRCC. Future clinical trials should prospectively define the VHL alteration status of study participants so that the true utility of such markers can be determined.

Genetic analysis of von Hippel-Lindau disease

Mutations in the von Hippel-Lindau (VHL) gene are responsible for VHL disease, congenital polycythemia, and are found in many sporadic tumor types as well. Reports of VHL mutations are dispersed throughout original articles and databases that have not been recently updated. We compiled a comprehensive mutation table of 1,548 germline and somatic VHL mutations, derived from this protein of only 213 amino acids. We describe detailed phenotype and gene mutation information for 945 VHL families, including 30 previously unpublished kindreds from The Netherlands (six novel mutations). These data represent the most extensive catalog of germline VHL mutations to date. We also review VHL disease, known and theorized pathogenesis of common VHL manifestations, and genotype-phenotype correlations. Analysis of all VHL families, excluding germline mutations resulting in congenital polycythemias, describes the spectrum of mutation types: 52% missense, 13% frameshift, 11% nonsense, 6% in-frame deletions/insertions, 11% large/complete deletions, and 7% splice mutations. This easy-to-use compilation of VHL mutations is intended to facilitate research and function as a necessary adjunct for physicians when providing patient information.

VHL genetic alteration in CCRCC does not determine de-regulation of HIF, CAIX, hnRNP A2/B1 and osteopontin.

Background: von Hippel–Lindau (VHL) tumour suppressor gene inactivation is associated with clear cell renal cell carcinoma (CCRCC) development. The VHL protein (pVHL) has been proposed to regulate the expression of several proteins including Hypoxia Inducible Factor-α (HIF-α), carbonic anhydrase (CA)IX, heterogeneous nuclear ribonucleoprotein (hnRNP) A2/B1 and osteopontin. pVHL has been characterized in vitro, however, clinical studies are limited. We evaluated the impact of VHL genetic alterations on the expression of several pVHL protein targets in paired normal and tumor tissue. Methods: The VHL gene was sequenced in 23 CCRCC patients and VHL transcript levels were evaluated by real-time RT-PCR. Expression of pVHL’s protein targets were determined by Western blotting in 17 paired patient samples. Results: VHL genetic alterations were identified in 43.5% (10/23) of CCRCCs. HIF-1α, HIF-2α and CAIX were up-regulated in 88.2% (15/17), 100% (17/17) and 88.2% (15/17) of tumors respectively and their expression is independent of VHL status. hnRNP A2/B1 and osteopontin expression was variable in CCRCCs and had no association with VHL genetic status. Conclusion: As expression of these proposed pVHL targets can be achieved independently of VHL mutation (and possibly by hypoxia alone), these data suggests that other pVHL targets may be more crucial in renal carcinogenesis.

Renal Cell Carcinoma in Children and Young Adults: Clinicopathological, Immunohistochemical, and VHL Gene Analysis of 46 Cases With Follow-up

To further study the characteristics of renal cell carcinoma (RCC) in young patients and better define their biological features, 46 RCCs of patients younger than 25 years were morphologically and immunohistochemically characterized with follow-up. Loss of heterozygosity (LOH) analysis of the von Hippel-Lindau (VHL) gene region and screening for VHL gene mutations were performed in all tumors. Applying the 2004 WHO classification for RCC, there were 19 Xp11.2 translocation RCCs, 9 clear cell RCCs, 17 papillary RCCs, and 1 unclassified RCC. All 19 Xp11.2 translocation RCCs showed moderate to strong immunoreactivity for TFE3. None had TFEB immunoreactivity. One Xp11.2 translocation RCC had an unreported morphology with empty or ground glass nuclei, occasional nuclear grooves, inconspicuous nucleoli and abundant mucinous material in stroma.VHL gene analysis revealed deletions at 3p25-26 in 1 clear cell RCC and 1 papillary type 2 RCC. The papillary type 2 RCC was also presented with a family history of VHL disease and found a germline mutation G → C on a splicing site at position 553+5. The present case widens the spectrum of microscopic features to be found in VHL-associated RCC. There were no VHL mutations in the remaining 45 RCCs. Statistical analysis of stage and outcome revealed that TFE+ pediatric RCCs were significantly more frequently associated with a higher pTNM pT3/pT4 stage and a poorer outcome than TFE-RCCs (P < .05). Owing to the already known aggressive behavior of these Xp11.2 translocation RCCs, patients with TFE+ pediatric RCCs should benefit from a stricter follow-up.

Parasympathetic Paragangliomas Are Part of the Von Hippel-Lindau Syndrome

Von Hippel-Lindau (VHL) disease, caused by germline mutations in the VHL gene, is a hereditary tumor syndrome manifested by hemangioblastomas, clear cell renal cell carcinomas, and pheochromocytomas. In addition, a multitude of other rare tumors, including parasympathetic paragangliomas, can occur and even be the sole manifestation of VHL disease. The VHL gene is a bona fide tumor suppressor gene with biallelic inactivation contributing to tumor formation. However, in parasympathetic paragangliomas occurring in VHL disease, biallelic inactivation of the VHL gene has not been demonstrated to date. The head and neck paragangliomas of two VHL patients were analyzed for mutations by direct sequencing of the VHL gene. In addition loss of heterozygosity analysis was performed for three microsatellite loci near the VHL gene. To rule out other underlying genetic causes of the parasympathetic paragangliomas, mutation analysis of the SDHB, SDHC, and SDHD genes was also performed. Apart from germline VHL mutations, no additional mutations were found in the paraganglioma-related tumor suppressor genes SDHB, SDHC, and SDHD. Analysis of paraganglioma tissue revealed loss of the VHL wild-type allele in both tumors, indicating that in these tumors biallelic VHL gene inactivation occurred. These findings indicate that parasympathetic paragangliomas in VHL disease, although rare, are part of the syndrome and related to VHL gene inactivation. Clinicians should be aware of the potential occurrence of parasympathetic paragangliomas in VHL disease.

Molecular Pathways in Metastatic Renal Cell Carcinoma: The Evolving Role of Mammalian Target of Rapamycin Inhibitors

Abstract Context Metastatic renal cell carcinoma (mRCC) is particularly resistant to conventional treatments. Improved understanding of the molecular pathways involved in mRCC has led to the development of novel targeted therapies for this disease. Objective This review describes key molecular pathways that have emerged as therapeutic targets for mRCC. Particular emphasis is placed on the mammalian target of rapamycin (mTOR) pathway and the newer class of targeted agents (ie, mTOR inhibitors). Evidence acquisition Medical literature was retrieved from PubMed during January 2009. Additional relevant articles were included from the bibliographies of retrieved literature. Evidence synthesis The von Hippel-Lindau (VHL) tumour suppressor gene was discovered in 1993 and has a vital role in renal cell carcinoma (RCC) pathogenesis. VHL mutations lead to accumulation of hypoxia-inducible factors (HIFs) that stimulate overexpression of the proangiogenic vascular endothelial growth factor (VEGF). The mTOR pathway was subsequently identified, which regulates cell growth, proliferation, and angiogenesis, and also has a pivotal role in RCC. An increase in HIF expression is a product of the mTOR pathway. Therefore, agents that suppress the mTOR pathway have become the focus of much research. Such mTOR inhibitors as everolimus and temsirolimus have shown robust clinical efficacy in treating mRCC. For example, everolimus has proved effective in patients whose disease has progressed after treatment with VEGF-targeted therapy. Conclusions Targeted agents against components of the mTOR pathway are in clinical use and have improved outcomes for patients with advanced disease and poor prognosis or with advanced disease that has become refractory to sunitinib or sorafenib.

Differences in regulation of tight junctions and cell morphology between VHL mutations from disease subtypes

BackgroundIn von Hippel-Lindau (VHL) disease, germline mutations in the VHL tumor suppressor gene cause clear cell renal carcinomas, hemangioblastomas, and pheochromocytomas. The VHL gene product is part of an ubiquitin E3 ligase complex and hypoxia-inducible factor alpha (HIF-α) is a key substrate, although additional VHL functions have been described. A genotype-phenotype relationship exists in VHL disease such that specific VHL mutations elicit certain subsets of these tumors. Here, we examine VHL genotype-phenotype correlations at the cellular level, focusing on the regulation of tight junctions and cell morphology.MethodsWild-type and various mutant VHL proteins representing VHL disease subtypes were stably expressed in 3 VHL-negative renal carcinoma cell lines. Using these cell lines, the roles of various VHL-associated cellular functions in regulation of cell morphology were investigated.ResultsAs a whole, type 1 mutants varied greatly from type 2 mutants, demonstrating high levels of HIF-2α, cyclin D1 and α5 integrin, lower p27 levels, and a spindly, fibroblastic cellular appearance. Type 2 mutations demonstrated an epithelial morphology similar to wild-type VHL in the majority of the renal cell lines used. Knockdown of p27 in cells with wild-type VHL led to perturbations of both epithelial morphology and ZO-1 localization to tight junctions. ZO-1 localization correlated well with VHL disease subtypes, with greater mislocalization observed for genotypes associated with a higher risk of renal carcinoma. HIF-2α knockdown in 786-O partially restored ZO-1 localization, but did not restore an epithelial morphology.ConclusionVHL has both HIF-α dependent and HIF-α independent functions in regulating tight junctions and cell morphology that likely impact the clinical phenotypes seen in VHL disease.

Sequential Sorafenib and Sunitinib for Renal Cell Carcinoma

Sorafenib and sunitinib are 2 tyrosine kinase inhibitors that were recently approved for renal cell carcinoma. In many patients sequential administration of the 2 drugs occurs because of the lack of sustained efficacy of the first agent. We determined the efficacy and safety of sequential administration. To determine whether cross-resistance occurs between these 2 drugs we analyzed the outcome in 90 consecutive patients with renal cell carcinoma from 4 sites in France who had received the 2 drugs sequentially. All patients received sorafenib followed by sunitinib or vice versa. From 2003 to 2006, 68 patients received sorafenib, while 22 received sunitinib first. In the sorafenib-sunitinib group median progression-free survival was 26 weeks with sorafenib and 28 with sunitinib. In the sunitinib-sorafenib group median progression-free survival was 22 weeks with sunitinib and 17 with sorafenib. Median overall survival was 135 weeks in the sorafenib-sunitinib group and 82 weeks in the sunitinib-sorafenib group (HR 0.49, 95% CI 0.16 to 0.96, p = 0.04). The average duration of sequential administration was 61 and 49 weeks, respectively, in the sorafenib-sunitinib and sunitinib-sorafenib groups. Each sequence was well tolerated and no increase in grade 3-4 toxicity was observed. Overall this retrospective study supports the conclusion of the lack of absolute cross-resistance between tyrosine kinase inhibitors. In this renal cell carcinoma population sorafenib followed by sunitinib was associated with longer survival than sunitinib followed by sorafenib. However, this observation needs further confirmation.