Solid renal tumor severity in von Hippel Lindau disease is related to germline deletion length and location

The Emerging Role of PET/CT with PSMA-Targeting Radiopharmaceuticals in Clear Cell Renal Cancer: An Updated Systematic Review

BACKGROUND

Recent articles proposed the employment of positron emission tomography/computed tomography (PET/CT) with prostate-specific membrane antigen (PSMA)-targeting radiopharmaceuticals in clear cell renal cell carcinoma (ccRCC).

METHODS

The authors performed a comprehensive literature search of studies on the performance of PET/CT with PSMA-targeting radiopharmaceuticals in ccRCC. Original articles concerning this imaging examination were included in newly diagnosed ccRCC patients and ccRCC patients with disease recurrence.

RESULTS

A total of sixteen papers concerning the diagnostic performance of PSMA-targeted PET/CT in ccRCC (331 patients) were included in this systematic review. The included articles demonstrated an excellent detection rate of PSMA-targeting PET/CT in ccRCC.

CONCLUSIONS

PSMA-targeted PET/CT seems promising in detecting ccRCC lesions as well as in discriminating the presence of aggressive phenotypes. Prospective multicentric studies are warranted to strengthen the role of PSMA-targeting PET/CT in ccRCC.

Mosaicism in Tumor Suppressor Gene Syndromes: Prevalence, Diagnostic Strategies, and Transmission Risk

A mosaic state arises when pathogenic variants are acquired in certain cell lineages during postzygotic development, and mosaic individuals may present with a generalized or localized phenotype. Here, we review the current state of knowledge regarding mosaicism for eight common tumor suppressor genes-NF1, NF2, TSC1, TSC2, PTEN, VHL, RB1, and TP53-and their related genetic syndromes/entities. We compare and discuss approaches for comprehensive diagnostic genetic testing, the spectrum of variant allele frequency, and disease severity. We also review affected individuals who have no mutation identified after conventional genetic analysis, as well as genotype-phenotype correlations and transmission risk for each tumor suppressor gene in full heterozygous and mosaic patients. This review provides new insight into similarities as well as marked differences regarding the appreciation of mosaicism in these tumor suppressor syndromes.

von Hippel-Lindau disease: Updated guideline for diagnosis and surveillance

von Hippel Lindau disease (vHL) is caused by a hereditary predisposition to multiple neoplasms, especially hemangioblastomas in the retina and CNS, renal cell carcinomas (RCC), pheochromocytomas, neuroendocrine pancreatic tumours (PNET) and endolymphatic sac tumours. Evidence based approaches are needed to ensure an optimal clinical care, while minimizing the burden for the patients and their families. This guideline is based on evidence from the international vHL literature and extensive research of geno- and phenotypic characteristics, disease progression and surveillance effect in the national Danish vHL cohort. We included the views and preferences of the Danish vHL patients, ensured consensus among Danish experts and compared with international recommendations. RECOMMENDATIONS: vHL can be diagnosed on clinical criteria, only; however, in most cases the diagnosis can be supported by identification of a pathogenic or likely pathogenic variant in VHL. Surveillance should be initiated in childhood in persons with, or at risk of, vHL, and include regular examination of the retina, CNS, inner ear, kidneys, neuroendocrine glands, and pancreas. Treatment of vHL manifestations should be planned to optimize the chance of cure, without unnecessary sequelae. Most manifestations are currently treated by surgery. However, belzutifan, that targets HIF-2α was recently approved by the U.S. Food and Drug Administration (FDA) for adult patients with vHL-associated RCC, CNS hemangioblastomas, or PNETs, not requiring immediate surgery. Diagnostics, surveillance, and treatment of vHL can be undertaken successfully by experts collaborating in multidisciplinary teams. Systematic registration, collaboration with patient organisations, and research are fundamental for the continuous improvement of clinical care and optimization of outcome with minimal patient inconvenience.

A germline 1;3 translocation disrupting the VHL gene: a novel genetic cause for von Hippel-Lindau

Von Hippel-Lindau (VHL) disease is an autosomal dominant hereditary tumour susceptibility disease caused by germline pathogenic variation of the VHL tumour suppressor gene. Affected individuals are at risk of developing multiple malignant and benign tumours in a number of organs.In this report, a male patient in his 20s who presented to the Urologic Oncology Branch at the National Cancer Institute with a clinical diagnosis of VHL was found to have multiple cerebellar haemangioblastomas, bilateral epididymal cysts, multiple pancreatic cysts, and multiple, bilateral renal tumours and cysts. The patient had no family history of VHL and was negative for germline VHL mutation by standard genetic testing. Further genetic analysis demonstrated a germline balanced translocation between chromosomes 1 and 3, t(1;3)(p36.3;p25) with a breakpoint on chromosome 3 within the second intron of the VHL gene. This created a pathogenic germline alteration in VHL by a novel mechanism that was not detectable by standard genetic testing.Karyotype analysis is not commonly performed in existing genetic screening protocols for patients with VHL. Based on this case, protocols should be updated to include karyotype analysis in patients who are clinically diagnosed with VHL but demonstrate no detectable mutation by existing genetic testing.

Distinct sequence features underlie microdeletions and gross deletions in the human genome

Microdeletions and gross deletions are important causes (~20%) of human inherited disease and their genomic locations are strongly influenced by the local DNA sequence environment. This notwithstanding, no study has systematically examined their underlying generative mechanisms. Here, we obtained 42,098 pathogenic microdeletions and gross deletions from the Human Gene Mutation Database (HGMD) that together form a continuum of germline deletions ranging in size from 1 to 28,394,429 bp. We analyzed the DNA sequence within 1 kb of the breakpoint junctions and found that the frequencies of non‐B DNA‐forming repeats, GC‐content, and the presence of seven of 78 specific sequence motifs in the vicinity of pathogenic deletions correlated with deletion length for deletions of length ≤30 bp. Further, we found that the presence of DR, GQ, and STR repeats is important for the formation of longer deletions (>30 bp) but not for the formation of shorter deletions (≤30 bp) while significantly (χ², p < 2E−16) more microhomologies were identified flanking short deletions than long deletions (length >30 bp). We provide evidence to support a functional distinction between microdeletions and gross deletions. Finally, we propose that a deletion length cut‐off of 25–30 bp may serve as an objective means to functionally distinguish microdeletions from gross deletions.

Comprehensive characterization of Alu-mediated breakpoints in germline VHL gene deletions and rearrangements in patients from 71 VHL families

Von Hippel-Lindau (VHL) is a hereditary multisystem disorder caused by germline alterations in the VHL gene. VHL patients are at risk for benign as well as malignant lesions in multiple organs including kidney, adrenal, pancreas, the central nervous system, retina, endolymphatic sac of the ear, epididymis, and broad ligament. An estimated 30%-35% of all families with VHL inherit a germline deletion of one, two, or all three exons. In this study, we have extensively characterized germline deletions identified in patients from 71 VHL families managed at the National Cancer Institute, including 59 partial (PD) and 12 complete VHL deletions (CD). Deletions that ranged in size from 1.09 to 355 kb. Fifty-eight deletions (55 PD and 3 CD) have been mapped to the exact breakpoints. Ninety-five percent (55 of 58) of mapped deletions involve Alu repeats at both breakpoints. Several novel classes of deletions were identified in this cohort, including two cases that have complex rearrangements involving both deletion and inversion, two cases with inserted extra Alu-like sequences, six cases that involve breakpoints in Alu repeats situated in opposite orientations, and a "hotspot" PD of Exon 3 observed in 12 families that involves the same pair of Alu repeats.

Biological and clinical impact of central nervous system hemangioblastomas in Chinese patients with von Hippel-Lindau disease: implications for treatment

Objective

Central nervous system (CNS) hemangioblastomas (HGBs) are the most frequent cause of mortality in patients with von Hippel-Lindau (VHL) genetic syndrome. However, there is a lack of large studies on the clinical features and optimal management of HGBs in Chinese patients.

Methods

VHL-related HGB cases treated surgically at our hospital from 2012 to 2019 were evaluated. Patients and family members meeting the clinical diagnostic criteria underwent genetic testing. Clinical, genetic and relevant imaging data were analyzed.

Results

Eighty-five VHL patients from 34 pedigrees in 16 Chinese provinces who underwent 121 operations for CNS HGBs were enrolled. Multiple operations were associated with a younger age at first operation (OR = 0.926, 95% CI = 0.871–0.985, P = 0.014, threshold: 27.5, sensitivity: 72.2%, specificity: 71.2%) and a longer postoperative period (OR = 1.096, 95% CI = 1.015–1.184, P = 0.019, threshold: 10.5, sensitivity: 66.7%, specificity: 76.3%). The age at first operation was younger in children than in their parents (23 pairs, P < 0.001). The age at first operation was younger in siblings born later than in those born earlier (10 pairs, P = 0.01). Most untreated tumors (98.2%) remained relatively stable during follow-up (range, 0.5–7; median, 2). However, new tumors continued to emerge (0.14 tumor/year).

Conclusion

VHL-associated CNS HGB is a long-term chronic disease with repeated attacks, likely with genetic anticipation in Chinese pedigrees. When the age at first operation is under 27.5 years, or the postoperative period is longer than 10.5 years, the risk of multiple operations is increased. While most unresected HGBs remain stable after surgery, new tumors may still slowly emerge; hence, scheduled follow-ups are necessary.

Growth Rates of Genetically Defined Renal Tumors: Implications for Active Surveillance and Intervention

PURPOSE

Published series of growth rates of renal tumors on active surveillance largely consist of tumors without pathologic or genetic data. Growth kinetics of genetically defined renal tumors are not well known. Here, we evaluate the growth of genetically defined renal tumors and their association with patient clinical and genetic characteristics.

PATIENTS AND METHODS

We evaluated patients with an inherited kidney cancer susceptibility syndrome as a result of a pathologic germline alteration of VHL, MET, FLCN, or BAP1 with at least 1 solid renal mass managed with active surveillance at our institution. Tumor growth rates (GR) were calculated and patients were stratified by genetic alteration and other clinical and genetic factors to analyze differences in growth rates using linear regression and comparative statistics.

RESULTS

A total of 292 patients with 435 genetically defined tumors were identified, including 286 VHL-deficient, 91 FLCN-deficient, 52 MET-activated, and 6 BAP1-deficient tumors. There were significant differences in GRs when stratified by genetic alteration. BAP1-deficient tumors had the fastest median GR (0.6 cm/y; interquartile range [IQR], 0.57-0.68 cm/y), followed by VHL-deficient tumors (GR, 0.37 cm/y; IQR, 0.25-0.57 cm/y), FLCN-deficient tumors (GR, 0.10 cm/y; IQR, 0.04-0.24 cm/y), and tumors with MET activation (GR, 0.15 cm/y; IQR, 0.053-0.32 cm/y; P < .001). Tumors from the same patient had similar GRs. Younger age was independently associated with higher GR (P = .005).

CONCLUSION

In a cohort of genetically defined tumors, tumor growth rates varied in a clinically and statistically different manner according to genetic subtype. Rapid growth of BAP1-deficient tumors indicates that these patients should be managed with caution. The faster growth of tumors in younger patients may support more frequent imaging, whereas the slower growth of other tumors may support extended surveillance beyond annual imaging in some instances.

Whole exome sequencing identified genetic variations in Chinese hemangioblastoma patients

Hemangioblastomas (HBs) are uncommon tumors characterized by the presence of inactivating alterations in the von Hippel-Lindau (VHL) gene in inherited cases and by infrequent somatic mutation in sporadic entities. We performed whole exome sequencing on 11 HB patients to further elucidate the genetics of HBs. A total of 270 somatic variations in 219 genes, of which there were 86 mutations in 67 genes, were found in sporadic HBs, and 184 mutations were found in 154 genes in familial HBs. C: G>T: A and T: A>C: G mutations are relatively common in most HB patients. Genes harboring the most significant mutations include PCDH9, KLHL12, DCAF4L1, and VHL in sporadic HBs, and ZNF814, DLG2, RIMS1, PNN, and MUC7 in familial HBs. The frequency of CNV varied considerably within sporadic HBs but was relatively similar within familial HBs. Five genes, including OTOGL, PLCB4, SCEL, THSD4, and WWOX, have CNVs in the six patients with sporadic HBs, and three genes, including ABCA6, CWC27, and LAMA2, have CNVs in the five patients with familial HBs. We found new genetic mutations and CNVs that might be involved in HBs; these findings highlight the complexity of the tumorigenesis of HBs and pinpoint potential therapeutic targets for the treatment of HBs.

Comprehensive genomic and phenotypic characterization of germline FH deletion in hereditary leiomyomatosis and renal cell carcinoma

Hereditary leiomyomatosis and renal cell carcinoma (HLRCC) is a familial cancer syndrome associated with the development of cutaneous and uterine leiomyomas, and an aggressive form of type 2 papillary kidney cancer. HLRCC is characterized by germline mutation of the FH gene. This study evaluated the prevalence and clinical phenotype of FH deletions in HLRCC patients. Patients with phenotypic manifestations consistent with HLRCC who lacked detectable germline FH intragenic mutations were investigated for FH deletion. A series of 28 patients from 13 families were evaluated using a combination of a comparative genomic hybridization (CGH) array and/or CLIA-approved FH deletion/duplication analyses. Thirteen distinct germline deletions were identified in the 13 UOB families, including 11 complete FH gene deletions and 2 partial FH gene deletions. The size of eight evaluated complete FH deletions varied from ∼4.74 Mb to 249 kb, with all deletions resulting in additional gene losses. Two partial FH gene deletions were identified, with one resulting in loss of exon 1 and the upstream region of the FH gene only. Kidney cancer was diagnosed in 9 (32%) of 28 patients and 7 (54%) of 13 families possessing either complete or partial FH deletions. Cutaneous and uterine leiomyomas were observed at similar rates to those in FH point mutation families. Complete or partial FH gene alterations in HLRCC families are associated with all of the canonical HLRCC manifestations, including type 2 papillary kidney cancer and should be screened for in any patient at-risk for this disorder.

Simple and rapid characterization of novel large germline deletions in SDHB, SDHC and SDHD-related paraganglioma

Germline mutations in genes encoding subunits of succinate dehydrogenase (SDH) are associated with hereditary paraganglioma and pheochromocytoma. Although most mutations in SDHB, SDHC and SDHD are intraexonic variants, large germline deletions may represent up to 10% of all variants but are rarely characterized at the DNA sequence level. Additional phenotypic effects resulting from deletions that affect neighboring genes are also not understood. We performed multiplex ligation-dependent probe amplification, followed by a simple long-range PCR 'chromosome walking' protocol to characterize breakpoints in 20 SDHx-linked paraganglioma-pheochromocytoma patients. Breakpoints were confirmed by conventional PCR and Sanger sequencing. Heterozygous germline deletions of up to 104 kb in size were identified in SDHB, SDHC, SDHD and flanking genes in 20 paraganglioma-pheochromocytoma patients. The exact breakpoint could be determined in 16 paraganglioma-pheochromocytoma patients of which 15 were novel deletions. In six patients proximal genes were also deleted, including PADI2, MFAP2, ATP13A2 (PARK9), CFAP126, TIMM8B and C11orf57. These genes were either partially or completely deleted, but did not modify the phenotype. This study increases the number of known SDHx deletions by over 50% and demonstrates that a significant proportion of large gene deletions can be resolved at the nucleotide level using a simple and rapid method.

Von Hippel-Lindau Disease

Von Hippel-Lindau disease is an autosomal dominant syndrome which occurs secondary to germline mutations in the VHL tumor suppressor gene, located on chromosome 3. Clinically von Hippel-Lindau disease is characterized by an increased risk of developing simple visceral cysts, most commonly in the pancreas and kidneys, in addition to an increased risk of developing neoplasms, often with clear cell features, in a multitude of organ systems. The most common neoplasms are cerebellar and retinal hemangioblastomas, adrenal pheochromocytomas, clear cell renal cell carcinomas, pancreatic neuroendocrine tumors, pancreatic serous cystadenomas, and endolymphatic sac tumors. These lesions most commonly present during adulthood; however, screening and surveillance for the development of these lesions should begin in the pediatric years for patients with von Hippel-Lindau disease. In this review article, the genetics and most common neoplasms of von Hippel-Lindau disease are reviewed, with an eye towards implications for the pediatric patient.

Patient-specific factors influence somatic variation patterns in von Hippel-Lindau disease renal tumours

Cancer development is presumed to be an evolutionary process that is influenced by genetic background and environment. In laboratory animals, genetics and environment are variables that can largely be held constant. In humans, it is possible to compare independent tumours that have developed in the same patient, effectively constraining genetic and environmental variation and leaving only stochastic processes. Patients affected with von Hippel-Lindau disease are at risk of developing multiple independent clear cell renal carcinomas. Here we perform whole-genome sequencing on 40 tumours from six von Hippel-Lindau patients. We confirm that the tumours are clonally independent, having distinct somatic single-nucleotide variants. Although tumours from the same patient show many differences, within-patient patterns are discernible. Single-nucleotide substitution type rates are significantly different between patients and show biases in trinucleotide mutation context. We also observe biases in chromosome copy number aberrations. These results show that genetic background and/or environment can influence the types of mutations that occur.

von Hippel-Lindau Disease: Review of Genetics and Imaging

von Hippel-Lindau (VHL) disease is an autosomal-dominant, hereditary, multisystem neoplasia syndrome with increased susceptibility to several benign and malignant tumors. VHL occurs in about 1 in 36,000 live births and is associated with germline mutation of the VHL tumor suppressor gene on the short arm of chromosome 3. VHL disease exhibits diverse genotype and phenotype correlations, exhibits variable intrafamilial and interfamilial expressivity, and can manifest with benign and malignant tumors of the central nervous system, kidneys, adrenals, pancreas, and reproductive organs. Imaging and management of this entity are therefore multidisciplinary. An overview of VHL disease is presented.

VHL, the story of a tumour suppressor gene

Since the Von Hippel-Lindau (VHL) disease tumour suppressor gene VHL was identified in 1993 as the genetic basis for a rare disorder, it has proved to be of wide medical and scientific interest. VHL tumour suppressor protein (pVHL) plays a key part in cellular oxygen sensing by targeting hypoxia-inducible factors for ubiquitylation and proteasomal degradation. Early inactivation of VHL is commonly seen in clear-cell renal cell carcinoma (ccRCC), and insights gained from the functional analysis of pVHL have provided the foundation for the routine treatment of advanced-stage ccRCC with novel targeted therapies. However, recent sequencing studies have identified additional driver genes that are involved in the pathogenesis of ccRCC. As our understanding of the importance of VHL matures, it is timely to review progress from its initial description to current knowledge of VHL biology, as well as future prospects for novel medical treatments for VHL disease and ccRCC.

Genetic evidence of a precisely tuned dysregulation in the hypoxia signaling pathway during oncogenesis

The classic model of tumor suppression implies that malignant transformation requires full "two-hit" inactivation of a tumor-suppressor gene. However, more recent work in mice has led to the proposal of a "continuum" model that involves more fluid concepts such as gene dosage-sensitivity and tissue specificity. Mutations in the tumor-suppressor gene von Hippel-Lindau (VHL) are associated with a complex spectrum of conditions. Homozygotes or compound heterozygotes for the R200W germline mutation in VHL have Chuvash polycythemia, whereas heterozygous carriers are free of disease. Individuals with classic, heterozygous VHL mutations have VHL disease and are at high risk of multiple tumors (e.g., CNS hemangioblastomas, pheochromocytoma, and renal cell carcinoma). We report here an atypical family bearing two VHL gene mutations in cis (R200W and R161Q), together with phenotypic analysis, structural modeling, functional, and transcriptomic studies of these mutants in comparison with classical mutants involved in the different VHL phenotypes. We demonstrate that the complex pattern of disease manifestations observed in VHL syndrome is perfectly correlated with a gradient of VHL protein (pVHL) dysfunction in hypoxia signaling pathways. Thus, by studying naturally occurring familial mutations, our work validates in humans the "continuum" model of tumor suppression.

TERT promoter mutations in clear cell renal cell carcinoma

We screened promoter region of the telomerase reverse transcriptase (TERT) for activating somatic mutations in 188 tumors from patients with clear cell renal cell carcinoma (ccRCC). Twelve tumors (6.4%) carried a mutation within the core promoter region of the gene. The mutations were less frequent in high grade tumors compared to low grade tumors [odds ratio (OR) = 0.15, 95% confidence interval (CI) = 0.03-0.72, p = 0.02]. Multivariate analysis for cause specific survival showed statistically significant poor outcome in patients with TERT promoter mutations [hazard ratio (HR) = 2.90, 95% CI = 1.13-7.39, p = 0.03]. A common polymorphism (rs2853669) within the locus seemed to act as a modifier of the effect of the mutations on patient survival as the noncarriers of the variant allele with the TERT promoter mutations showed worst survival (HR = 3.34, 95% CI = 1.24-8.98, p = 0.02). We also measured relative telomere length (RTL) in tumors and difference between tumors with and without the TERT promoter mutations was not statistically significant. Similarly, no difference in patient survival based on RTL in tumors was observed. Our study showed a relatively low frequency of TERT promoter mutations in ccRCC. Nevertheless, patients with the mutations, particularly in the absence of the rs2853669 variant showed the worst disease-specific survival. Thus, it is possible that the TERT promoter mutations define a small subset of tumors with an aggressive behavior.

Large deletion causing von Hippel-Lindau disease and hereditary breast cancer syndrome

Patients with intragenic mutations of the VHL gene have a typical disease presentation. However in cases of large VHL gene deletions which involve other genes in the proximity of the VHL gene a presentation of the disease can be different.

To investigate whether large VHL deletions that remove the FANCD2 gene have an effect on the disease phenotype, we studied a family with a 50 kb large deletion encompassing these two genes. Four patients in this family were affected by VHL-related lesions. However one carrier of the deletion also had bilateral ductal breast cancer at age 46 and 49. Both tumors were of ~2 cm in diameter. On one side lymph nodes were affected. One tumor was ER- and PR-negative (HER2 s unknown) and the second was ER- and PR-positive, and HER2-negative.

Our study suggests that a deletion of FANCD2 gene, an important gene in the DNA repair pathway, may be associated with an increased risk of breast cancer, but further studies are needed in this regard.

A review of vascular anomalies: genetics and common syndromes

Vascular tumors and malformations are unique in that affected cells exhibit disrupted angiogenesis. The current treatment options often yield suboptimal results. New insight into the genetics and molecular basis of vascular anomalies may pave the way for potential development of targeted therapy. The authors review the genetic and molecular basis of vascular anomalies and common associated syndromes.

Renal cancer in von Hippel-Lindau disease and related syndromes

Sporadic and hereditary forms of renal cell carcinoma (RCC), von Hippel-Lindau (VHL) disease and the familial paraganglioma syndromes are closely related in terms of their clinical, molecular, and genetic aspects. Most RCCs occur sporadically and the heritable fraction of RCC is estimated to be just 2-4%. An understanding of the molecular genetic basis, the disease-specific and gene-specific biology and the clinical characteristics of these cancer syndromes is of utmost importance for effective genetic diagnosis and appropriate treatment. In addition, such insight will improve our understanding of sporadic RCCs. To date, 10 different heritable RCC syndromes have been described. VHL syndrome is the oldest known hereditary RCC syndrome. Similar to VHL disease, phaeochromocytoma is a major manifestation of the paraganglioma syndromes types 1, 3 and 4 in which RCCs have been reported. These syndromes are therefore regarded as VHL-related disorders and are included in this Review. Multifocal tumours, bilateral occurrence, a young age at diagnosis and/or family history are clinical red flags suggestive of hereditary disease and should trigger referral for genetic and molecular analysis. The identification of an underlying genetic alteration enables gene-specific risk assessment and opens up the possibility of a tailored follow-up strategy and specific surveillance protocols as the basis of effective preventive medicine. The important goals of preventive medicine are to increase the life expectancy of affected patients and to improve their quality of life. The study of seemingly rare hereditary syndromes and their susceptibility genes has consistently revealed clues regarding the aetiology and pathogenesis of these diseases, and can aid diagnosis and the development of therapeutics for patients affected by much more common sporadic counterparts.

Genetic basis of kidney cancer: role of genomics for the development of disease-based therapeutics

Kidney cancer is not a single disease; it is made up of a number of different types of cancer, including clear cell, type 1 papillary, type 2 papillary, chromophobe, TFE3, TFEB, and oncocytoma. Sporadic, nonfamilial kidney cancer includes clear cell kidney cancer (75%), type 1 papillary kidney cancer (10%), papillary type 2 kidney cancer (including collecting duct and medullary RCC) (5%), the microphalmia-associated transcription (MiT) family translocation kidney cancers (TFE3, TFEB, and MITF), chromophobe kidney cancer (5%), and oncocytoma (5%). Each has a distinct histology, a different clinical course, responds differently to therapy, and is caused by mutation in a different gene. Genomic studies identifying the genes for kidney cancer, including the VHL, MET, FLCN, fumarate hydratase, succinate dehydrogenase, TSC1, TSC2, and TFE3 genes, have significantly altered the ways in which patients with kidney cancer are managed. While seven FDA-approved agents that target the VHL pathway have been approved for the treatment of patients with advanced kidney cancer, further genomic studies, such as whole genome sequencing, gene expression patterns, and gene copy number, will be required to gain a complete understanding of the genetic basis of kidney cancer and of the kidney cancer gene pathways and, most importantly, to provide the foundation for the development of effective forms of therapy for patients with this disease.

FusionFinder: a software tool to identify expressed gene fusion candidates from RNA-Seq data

The hallmarks of many haematological malignancies and solid tumours are chromosomal translocations, which may lead to gene fusions. Recently, next-generation sequencing techniques at the transcriptome level (RNA-Seq) have been used to verify known and discover novel transcribed gene fusions. We present FusionFinder, a Perl-based software designed to automate the discovery of candidate gene fusion partners from single-end (SE) or paired-end (PE) RNA-Seq read data. FusionFinder was applied to data from a previously published analysis of the K562 chronic myeloid leukaemia (CML) cell line. Using FusionFinder we successfully replicated the findings of this study and detected additional previously unreported fusion genes in their dataset, which were confirmed experimentally. These included two isoforms of a fusion involving the genes BRK1 and VHL, whose co-deletion has previously been associated with the prevalence and severity of renal-cell carcinoma. FusionFinder is made freely available for non-commercial use and can be downloaded from the project website (http://bioinformatics.childhealthresearch.org.au/software/fusionfinder/).

Growth kinetics in von Hippel-Lindau-associated renal cell carcinoma

OBJECTIVE

To evaluate the growth kinetics of renal cell carcinoma (RCC) in von Hippel-Lindau (VHL) disease in a large trial by CT/MRI scan. VHL disease is a multisystemic disorder predisposing to renal cysts and cancer. There is a general assumption that VHL-associated RCC presents slower growth rates than sporadic RCC.

PATIENTS AND METHODS

We describe growth kinetics of 96 renal tumours in 64 VHL patients with analysed germline mutation (54/64 treated, 10/64 active surveillance) over a mean follow-up of 54.9 months. We calculated tumour volume, growth rate, multiplication of tumour volume per year and overall, as well as tumour volume doubling time.

RESULTS

The mean growth rate of 96 tumours was 4.4 mm/year (SD 3.2, median 4.1 mm/year), mean volume doubling time was 25.7 months (SD 20.2, median 22.2 months). We saw a median 1.4-fold increase in tumour volume per year. At treatment time point, VHL kidneys comprised 39% tumour and 15.7% cyst volume fraction. We saw no correlation between tumour size and growth parameters.

CONCLUSION

VHL-associated RCC show large variances in tumour growth behaviour. Compared to the literature, in our study the growth rates (mm/year) of RCC in VHL disease did not differ from those of sporadic RCC. Fast tumour growth increases the risk for metastases.

Familial renal cancer: molecular genetics and surgical management

Familial renal cancer (FRC) is a heterogeneous disorder comprised of a variety of subtypes. Each subtype is known to have unique histologic features, genetic alterations, and response to therapy. Through the study of families affected by hereditary forms of kidney cancer, insights into the genetic basis of this disease have been identified. This has resulted in the elucidation of a number of kidney cancer gene pathways. Study of these pathways has led to the development of novel targeted molecular treatments for patients affected by systemic disease. As a result, the treatments for families affected by von Hippel-Lindau (VHL), hereditary papillary renal carcinoma (HPRC), hereditary leiomyomatosis renal cell carcinoma (HLRCC), and Birt-Hogg-Dubé (BHD) are rapidly changing. We review the genetics and contemporary surgical management of familial forms of kidney cancer.

Detection of the first gross CDC73 germline deletion in an HPT-JT syndrome family

Hereditary primary hyperparathyroidism (HPT) may develop as a solitary endocrinopathy (FIHP) or as part of multiple endocrine neoplasia Type 1, multiple endocrine neoplasia Type 2A, or hereditary HPT-jaw tumor syndrome. Inactivating germline mutations of the tumor suppressor gene CDC73 account for 14 and 50% of all FIHP and HPT-JT patients, respectively, and have also been found in almost 20% of apparently sporadic parathyroid carcinoma patients. Although more than 60 independent germline mutations have been described, to date no rearrangement affecting the CDC73 locus has been identified. By means of multiplex-PCR we found a large germline deletion affecting the whole gene in a two-generation HPT-JT family. Subsequently array-CGH and specific PCR analysis determined that the mutation spanned ∼ 547 kb, and included four additional genes: TROVE2, GLRX2, B3GALT2, and UCHL5. Although no clear mutation-specific phenotype was found associated to the presence of the mutation, further studies are needed to assess whether the loss of the neighboring genes could modify the phenotype of carriers. There was complete absence of nuclear staining in the two HPT-JT-related tumors available. The finding of the first rearrangement affecting the CDC73 gene warrants screening for this tumor suppressor gene inactivation mechanism not only in high-risk CDC73 point mutation-negative HPT-JT families, but also in FIHP patients.

von Hippel-Lindau disease: a clinical and scientific review

The autosomal dominantly inherited disorder von Hippel-Lindau disease (VHL) is caused by germline mutations in the VHL tumour suppressor gene (TSG). VHL mutations predispose to the development of a variety of tumours (most commonly retinal and central nervous system haemangioblastomas, clear cell renal carcinoma and phaeochromocytomas). Here, we review the clinical and genetic features of VHL disease, briefly review the molecular pathogenesis and outline clinical management and tumour surveillance strategies.

Impact of genetics on the diagnosis and treatment of renal cancer

Kidney cancer is a heterogeneous disease comprised of a number of histologic subtypes, each associated with unique genetic mutations, clinical features, and sensitivity to treatment. By examining families affected with the hereditary kidney cancer syndromes von Hippel-Lindau, hereditary papillary renal cell carcinoma, hereditary leiomyomatosis and renal cell carcinoma, and Birt-Hogg-Dubé, researchers have been able to identify the genes responsible for these syndromes. This work has revealed that kidney cancer is fundamentally a metabolic disorder, and as such, novel targeted therapies specific to their molecular biology have been developed and employed in both the hereditary and sporadic forms of renal cell carcinoma.

Brick1 is an essential regulator of actin cytoskeleton required for embryonic development and cell transformation

Brick1 (Brk1) is the less-studied component of the Wave/Scar pathway involved in the branched nucleation of actin fibers. The clinical relevance of Brk1 is emphasized by correlative data showing that Von Hippel-Lindau (VHL) patients that also lose the BRK1 gene are protected against the development of tumors. This contrasts with recent evidence suggesting that the Wave complex may function as an invasion suppressor in epithelial cancers. Here, we show that the downregulation of Brk1 results in abnormal actin stress fiber formation and vinculin distribution and loss of Arp2/3 and Wave proteins at the cellular protrusions. Brk1 is required for cell proliferation and cell transformation by oncogenes. In addition, Brk1 downregulation results in defective directional migration and invasive growth in renal cell carcinoma cells as well as in other tumor cell types. Finally, genetic ablation of Brk1 results in dramatic defects in embryo compaction and development, suggesting an essential role for this protein in actin dynamics. Thus, genetic loss or inhibition of BRK1 is likely to be protective against tumor development due to proliferation and motility defects in affected cells.

VHL frameshift mutation as target of nonsense-mediated mRNA decay in Drosophila melanogaster and human HEK293 cell line

There are many well-studied examples of human phenotypes resulting from nonsense or frameshift mutations that are modulated by Nonsense-Mediated mRNA Decay (NMD), a process that typically degrades transcripts containing premature termination codons (PTCs) in order to prevent translation of unnecessary or aberrant transcripts. Different types of germline mutations in the VHL gene cause the von Hippel-Lindau disease, a dominantly inherited familial cancer syndrome with a marked phenotypic variability and age-dependent penetrance. By generating the Drosophila UAS:Upf1^D45B line we showed the possible involvement of NMD mechanism in the modulation of the c.172delG frameshift mutation located in the exon 1 of Vhl gene. Further, by Quantitative Real-time PCR (QPCR) we demonstrated that the corresponding c.163delG human mutation is targeted by NMD in human HEK 293 cells. The UAS:Upf1^D45B line represents a useful system to identify novel substrates of NMD pathway in Drosophila melanogaster. Finally, we suggest the possible role of NMD on the regulation of VHL mutations.

The clinical implications of the genetics of renal cell carcinoma

Over the last several decades, the advances in molecular genetics have elucidated kidney cancer gene pathways. Kidney cancer is a heterogeneous disorder. Each specific type of kidney cancer has its own histologic features, gene, and clinical course. Insight into the genetic basis of kidney cancer has been learned largely from the study of the familial or hereditary forms of kidney cancer. Extirpative surgery is currently the treatment of choice for kidney cancer that is confined to the kidney. Treatment for advanced or metastatic kidney cancer is a formidable challenge with the traditional therapies currently available. However, investigation of the Mendelian single-gene syndromes, like von Hippel Lindau (VHL: VHL gene), hereditary papillary renal carcinoma (HPRC: c-Met gene), Birt-Hogg-Dubé (BHD: BHD gene), and hereditary leiomyomatosis renal cell cancer (HLRCC: fumarate hydratase gene) provides an opportunity to develop pathway specific therapies. Advances in molecular therapeutics offer novel treatment options for patients with advanced disease.

Head and neck paragangliomas in von Hippel-Lindau disease and multiple endocrine neoplasia type 2

BACKGROUND

Head and neck paragangliomas (HNPs) occur as sporadic or familial entities, the latter mostly in association with germline mutations of the SDHB, SDHC, or SDHD (SDHx) genes. Heritable non-SDHx HNP might occur in von Hippel-Lindau disease (VHL, VHL gene), multiple endocrine neoplasia type 2 (MEN2, RET gene), and neurofibromatosis type 1 (NF1, NF1 gene). Reports of non-SDHx HNP presentations are scarce and guidance for genetic testing nonexistent.

PATIENTS AND METHODS

An international consortium registered patients with HNPs and performed mutation analyses of the SDHx, VHL, and RET genes. Those with SDHx germline mutations were excluded for purposes of this study. Personal and family histories were evaluated for paraganglial tumors, for the major tumor manifestations, and for family history of VHL, MEN2, or NF1.

RESULTS

Twelve patients were found to have hereditary non-SDHx HNPs of a total of 809 HNP and 2084 VHL registrants, 11 in the setting of germline VHL mutations and one of a RET mutation. The prevalence of hereditary HNP is five in 1000 VHL patients and nine in 1000 non-SDHx HNP patients. Comprehensive literature review revealed previous reports of HNPs in five VHL, two MEN2, and one NF1 patient. Overall, 11 here presented HNP cases, and four previously reported VHL-HNPs had lesions characteristic for VHL and/or a positive family history for VHL.

CONCLUSIONS

Our observations provide evidence that molecular genetic testing for VHL or RET germline mutations in patients with HNP should be done only if personal and/or family history shows evidence for one of these syndromes.

Genetic signature for human risk assessment: lessons from trichloroethylene

Trichloroethylene (TCE), an organic solvent commonly used for metal degreasing and as a chemical additive, is a significant environmental contaminant that poses health concerns in humans. The US Environmental Protection Agency (EPA) is currently revising the 2001 TCE human risk assessment draft. The next draft is expected to be ready in 2008. TCE metabolites are detectable in humans and carry varying potencies for induction of cancers in animals. Genomic mechanisms have been explored in animals and humans to link TCE to carcinogenesis. DNA analysis provides an opportunity for detection of unique genetic alterations representing a signature of TCE exposure. These alterations can arise from genotoxic and nongenotoxic pathways at multiple points throughout tumorigenesis. Although fixation of alterations may require several stages of selection and modification, the spectra can be specific to TCE. Only a fraction of these alterations eventually lead to tumor formation and some contribute to tumor progression. Genetic events in two major TCE target organs are reviewed, including the VHL gene in kidney, and the Ras gene and genome-wide hypomethylation in liver. Attempts to identify a genetic signature of TCE exposure are challenged by inconsistent findings, lack of evidence of promutagenic lesions, biological relevance of specific genomic changes, and likelihood of coexposures. For human risk assessment, genome-wide screening is useful and is possible with the development of new DNA-sequencing technologies. Genetic screening for preneoplastic and tumor tissues from high-risk population is proposed to exclude the noise of passenger mutations and genetic polymorphisms.

Genetic basis for kidney cancer: opportunity for disease-specific approaches to therapy

BACKGROUND

Kidney cancer is not a homogenous entity; it is comprised of many different tumor types, with different biologies and molecular mechanisms leading to disease and therefore different treatment approaches.

OBJECTIVE

To describe the genetic basis and biochemical pathways underlying inherited forms of renal cancer, specifically in four described syndromes (von Hippel-Lindau [VHL], hereditary papillary renal cancer [HPRC], Birt-Hogg-Dubé [BHD] and hereditary leiomyomatosis renal cell carcinoma [HLRCC]), and to elucidate how the understanding of these diseases enables the possibility of disease-specific approaches to therapy.

METHODS

A systematic review of the published literature on inherited and sporadic forms of renal cancer was performed.

CONCLUSION

Understanding of the biology and mechanisms of different forms of kidney cancer provides an opportunity for development of new treatment options.

Genetic Counseling in Renal Masses

All urologists have faced patients suffering a renal cancer asking for the occurrence of the disease in their offspring and very often the answer to this question has not been well founded from the scientific point of view, and only in few cases a familial segregation tree is performed. The grate shift seen in the detection of small renal masses and renal cancer in the last decades will prompt us to know the indications for familial studies, which and when are necessary, and probably to refer those patients with a suspected familial syndrome to specialized oncological centers where the appropriate molecular and familial studies could be done. Use of molecular genetic testing for early identification of at-risk family members improves diagnostic certainty and would reduce costly screening procedures in at-risk members who have not inherited disease-causing mutations. This review will focus on the molecular bases of familial syndromes associated with small renal masses and the indications of familial studies in at-risk family members.

Pseudohypoxic pathways in renal cell carcinoma

Mutations of the von Hippel-Lindau (VHL) or fumarate hydratase (FH) genes lead to morphologically different renal cell carcinomas with distinct clinical courses and outcomes. The VHL protein is a part of an ubiquitin ligase complex that targets proteins for proteosomal degradation. FH is one of the mitochondrial enzymes of the Kreb's cycle. Despite two different functionalities and cellular locations, loss of either VHL or FH products has been shown to alter expression levels of hypoxia-inducible factors (HIF-1alpha and HIF-2alpha) and their downstream targets. HIF proteins are key regulators of oxygen homeostasis. Tight regulation of HIF allows for cell survival and growth at the time of hypoxic stress. HIF acts via transcriptional regulation of vascular endothelial growth factor, platelet derived growth factor, endothelial growth factor receptor, glucose transporter protein 1, erythropoietin, and transforming growth factor-alpha. Loss of VHL or FH is thought to result in a pseudohypoxic state so that cellular response pathways mediated by HIF are activated despite normal oxygen conditions. Understanding of these pseudohypoxic pathways has provided a better appreciation of the molecular mechanisms of carcinogenesis in addition to providing a rationale for targeted therapeutic approaches.

Loss of the actin regulator HSPC300 results in clear cell renal cell carcinoma protection in Von Hippel-Lindau patients

Clear cell renal cell carcinoma (ccRCC) is the most common malignant neoplasm of the kidney. The majority of hereditary and sporadic ccRCC cases are associated with germline and somatic mutations in the Von Hippel-Lindau gene (VHL), respectively. Gross deletions at the VHL locus can result either in ccRCC or in a mild clinical phenotype, with the absence of ccRCC development. Our goal in this study was to identify the molecular basis responsible for these differences in the clinical behavior in order to predict patients' phenotype. Using multiplex ligation-dependent amplification (MLPA), we identified and characterized gross VHL deletions in Spanish VHL families. A candidate gene related to this clinical association, HSPC300, was identified and depleted by RNA interference. It was possible to narrow the susceptibility region related to the mild clinical phenotype down to approximately 14 kb that included HSPC300 (C3orf10), a regulator of actin dynamics and cytoskeleton organization. Whereas 9 out of 10 families with ccRCC retained HSPC300 in the germline, loss of the HSPC300 locus was associated with mild clinical presentation of the disease in 6 out of 8 families. In fact, genetic depletion of HSPC300 resulted in cytoskeleton abnormalities and cytokinesis arrest in several tumor cell lines including ccRCC cells, suggesting that tumor cell proliferation was compromised in the absence of HSPC300. These clinical and functional data indicate a relevant function of HSPC300 in tumor cell progression, and suggest future therapeutic strategies based upon the inhibition of HSPC300 in renal cell carcinoma and possibly on other cancers.

Genotype-phenotype correlations in von Hippel-Lindau disease

von Hippel-Lindau (VHL) disease is a dominantly inherited familial cancer syndrome resulting from mutations in the VHL tumor suppressor gene. VHL disease displays marked variation in expression and the presence of pheochromocytoma has been linked to missense VHL mutations. We analyzed genotype-phenotype correlations in 573 individuals with VHL disease. Routine clinical and radiological surveillance of VHL patients and at-risk relatives was associated with increased detection of retinal angiomatosis (73 vs. 59% of cases) and a reduction in age at diagnosis of renal cell carcinoma (RCC) (44.0+/-10.9 vs. 39.7+/-10.3 years). We confirmed the association of pheochromocytoma with missense mutations described previously, but stratifying missense mutations into those that resulted in substitution of a surface amino acid and those that disrupted structural integrity demonstrated that surface amino acid substitutions conferred a higher pheochromocytoma risk. Age at first manifestation of VHL disease was significantly earlier (P=0.001), and age-related risks of retinal angiomas and RCC were higher (P=0.022 and P=0.0008, respectively) in individuals with a nonsense or frameshift mutation than in those with deletions or missense mutations that disrupted the structural integrity of the VHL gene product (pVHL). These results extend genotype-phenotype-protein structure correlations in VHL disease and provide a baseline for future chemoprevention studies in VHL disease.