Early-onset renal cell carcinoma as a novel extraparaganglial component of SDHB-associated heritable paraganglioma

The tumor susceptibility gene TMEM127 is mutated in renal cell carcinomas and modulates endolysosomal function

TMEM127 is an endosome-associated tumor suppressor gene in pheochromocytomas, neuroendocrine tumors that can co-occur with renal cell carcinomas (RCCs). TMEM127 loss leads to increased mTOR signaling. However, the spectrum of tumors with TMEM127 mutation and how TMEM127 and mTOR interact in tumorigenesis remains unknown. Here, we report that germline TMEM127 mutations occur in RCCs and that some mutant proteins, unlike wild-type (WT) TMEM127, fail to cooperate with activated early endosomal GTPase, Rab5, to inhibit mTOR signaling. Tmem127-null mouse embryonic fibroblasts (MEFs) are deficient in generating early-to-late hybrid endosomes upon constitutive Rab5 activation, a defect rescued by WT, but not mutant, TMEM127. This endosomal dysfunction results in diminished mTOR colocalization with Rab5-positive vesicles. Conversely, active, lysosomal-bound mTOR is increased in Tmem127-null MEFs, which also display enhanced lysosomal biogenesis. Our data map the tumor-suppressive properties of TMEM127 to modulation of mTOR function in the endolysosome, a feature that may contribute to both pheochromocytoma and RCC pathogenesis.

Hereditary renal cell carcinoma: genetics, clinical features, and surgical considerations

OBJECTIVES

Hereditary renal cancer syndromes have been described and have illuminated novel methods to treat sporadic renal cell carcinoma. In this work, we aimed to review the genetic basis, molecular pathology and clinical manifestations of hereditary syndromes, as well as outline principles of surgical management and use of targeted therapy.

METHODS

We performed a comprehensive review of selected peer-reviewed publications regarding hereditary renal cancer syndromes, their genetic basis, and recommendations for surgical management.

RESULTS

The major syndromes contributing to hereditary renal cell carcinoma are discussed along with relevant literature guiding their management. The evolving surgical and molecular treatments are discussed.

CONCLUSIONS

Identification of genetic basis of hereditary carcinomas provides opportunity for targeted therapy of metastatic sporadic renal cell carcinoma. Appropriate and timely surgical management of hereditary renal cancers decreases the possibility of development of metastatic disease, and allows for preservation of renal function despite the need for repeat surgical interventions.

The genetic basis of pheochromocytoma and paraganglioma: implications for management

Chromaffin cells are catecholamine-producing cells derived from neural crest tissue. Chromaffin tumors are rare tumors arising from these cells and are divided into pheochromocytoma arising from adrenal tissue and paraganglioma arising from extra-adrenal ganglia. Previously, ∼10% were believed to be hereditary, but advances in genome sequencing have shown that roughly 35% of apparently sporadic tumors have a hereditary component. In this review, we describe both classic and newly discovered hereditary chromaffin tumors syndromes and provide recommendations for genetic testing. In many cases, the genes associated with these conditions are linked to common kidney cancer pathways familiar to urologic oncologists.

Mitochondrial dysfunctions in cancer: genetic defects and oncogenic signaling impinging on TCA cycle activity

The tricarboxylic acid (TCA) cycle is a central route for oxidative metabolism. Besides being responsible for the production of NADH and FADH2, which fuel the mitochondrial electron transport chain to generate ATP, the TCA cycle is also a robust source of metabolic intermediates required for anabolic reactions. This is particularly important for highly proliferating cells, like tumour cells, which require a continuous supply of precursors for the synthesis of lipids, proteins and nucleic acids. A number of mutations among the TCA cycle enzymes have been discovered and their association with some tumour types has been established. In this review we summarise the current knowledge regarding alterations of the TCA cycle in tumours, with particular attention to the three germline mutations of the enzymes succinate dehydrogenase, fumarate hydratase and isocitrate dehydrogenase, which are involved in the pathogenesis of tumours, and to the aberrant regulation of TCA cycle components that are under the control of oncogenes and tumour suppressors.

Pheochromocytoma and paraganglioma pathogenesis: learning from genetic heterogeneity

The neuroendocrine tumours pheochromocytomas and paragangliomas carry the highest degree of heritability in human neoplasms, enabling genetic alterations to be traced to clinical phenotypes through their transmission in families. Mutations in more than a dozen distinct susceptibility genes have implicated multiple pathways in these tumours, offering insights into kinase downstream signalling interactions and hypoxia regulation, and uncovering links between metabolism, epigenetic remodelling and cell growth. These advances extend to co-occurring tumours, including renal, thyroid and gastrointestinal malignancies. Hereditary pheochromocytomas and paragangliomas are powerful models for recognizing cancer driver events, which can be harnessed for diagnostic purposes and for guiding the future development of targeted therapies.

Aerobic glycolysis: a novel target in kidney cancer

Renal cell carcinoma (RCC) is a heterogenous group of cancers that arise from the nephron. While there are distinct histologic subtypes associated with common genetic alterations, most forms of RCC are linked by a common pathway of dysregulated metabolism. Reliance on aerobic glycolysis, a feature of cancer first hypothesized by Warburg, is a common feature in sporadic and hereditary forms of kidney cancer. Two hereditary forms of RCC, succinate dehydrogenase (SDH) and hereditary leiomyomatosis and RCC (HLRCC), are characterized by mutations in Krebs cycle enzymes, rendering them dependent on glycolysis for energy requirements. The reliance on these pathways may make them vulnerable to novel metabolic strategies, including inhibition of glycolysis, glucose uptake and macromolecule biosynthesis.

Non-pheochromocytoma (PCC)/paraganglioma (PGL) tumors in patients with succinate dehydrogenase-related PCC-PGL syndromes: a clinicopathological and molecular analysis

OBJECTIVE

Although the succinate dehydrogenase (SDH)-related tumor spectrum has been recently expanded, there are only rare reports of non-pheochromocytoma/paraganglioma tumors in SDHx-mutated patients. Therefore, questions still remain unresolved concerning the aforementioned tumors with regard to their pathogenesis, clinicopathological phenotype, and even causal relatedness to SDHx mutations. Absence of SDHB expression in tumors derived from tissues susceptible to SDH deficiency is not fully elucidated.

DESIGN AND METHODS

Three unrelated SDHD patients, two with pituitary adenoma (PA) and one with papillary thyroid carcinoma (PTC), and three SDHB patients affected by renal cell carcinomas (RCCs) were identified from four European centers. SDHA/SDHB immunohistochemistry (IHC), SDHx mutation analysis, and loss of heterozygosity analysis of the involved SDHx gene were performed on all tumors. A cohort of 348 tumors of unknown SDHx mutational status, including renal tumors, PTCs, PAs, neuroblastic tumors, seminomas, and adenomatoid tumors, was investigated by SDHB IHC.

RESULTS

Of the six index patients, all RCCs and one PA displayed SDHB immunonegativity in contrast to the other PA and PTC. All immunonegative tumors demonstrated loss of the WT allele, indicating bi-allelic inactivation of the germline mutated gene. Of 348 tumors, one clear cell RCC exhibited partial loss of SDHB expression.

CONCLUSIONS

These findings strengthen the etiological association of SDHx genes with pituitary neoplasia and provide evidence against a link between PTC and SDHx mutations. Somatic deletions seem to constitute the second hit in SDHB-related renal neoplasia, while SDHx alterations do not appear to be primary drivers in sporadic tumorigenesis from tissues affected by SDH deficiency.

Hereditary kidney cancer syndromes

Inherited susceptibility to kidney cancer is a fascinating and complex topic. Our knowledge about types of genetic syndromes associated with an increased risk of disease is continually expanding. Currently, there are 10 syndromes associated with an increased risk of all types of kidney cancer, which are reviewed herein. Clear cell kidney cancer is associated with von Hippel Lindau disease, chromosome 3 translocations, PTEN hamartomatous syndrome, and mutations in the BAP1 gene as well as several of the genes encoding the proteins comprising the succinate dehydrogenase complex (SDHB/C/D). Type 1 papillary kidney cancers arise in conjunction with germline mutations in MET and type 2 as part of hereditary leiomyomatosis and kidney cell cancer (fumarate hydratase [FH] mutations). Chromophone and oncocytic kidney cancers are predominantly associated with Birt-Hogg-Dubé syndrome. Patients with Tuberous Sclerosis Complex (TSC) commonly have angiomyolipomas and rarely their malignant counterpart epithelioid angiomyolipomas. The targeted therapeutic options for the kidney cancer associated with these diseases are just starting to expand and are an area of active clinical research.

Recent developments in the treatment of renal cell carcinoma

Renal cell carcinoma (RCC) management has been imbued with new interest, in large part due to the recent success of new treatment options for advanced and metastatic disease. This has also been accompanied by less generally well known advances in the understanding of the molecular characterizations of subtypes of RCC with potential to lead to new therapeutic options. Additionally, the urologic oncology community is focusing on nephron-sparing surgical approaches with limited surgery if possible, and in conjunction with interventional radiologists, on ablative procedures for incidentally determined small renal masses. This report reviews some of the new biologic findings of adenocarcinoma of the kidney, and reviews the new therapeutics which continue to change the landscape for treatment of RCC.

Genetics of hereditary head and neck paragangliomas

BACKGROUND

The purpose of this study was to give an overview on hereditary syndromes associated with head and neck paragangliomas (HNPGs).

METHODS

Our methods were the review and discussion of the pertinent literature.

RESULTS

About one third of all patients with HNPGs are carriers of germline mutations. Hereditary HNPGs have been described in association with mutations of 10 different genes. Mutations of the genes succinate dehydrogenase subunit D (SDHD), succinate dehydrogenase complex assembly factor 2 gene (SDHAF2), succinate dehydrogenase subunit C (SDHC), and succinate dehydrogenase subunit B (SDHB) are the cause of paraganglioma syndromes (PGLs) 1, 2, 3, and 4. Succinate dehydrogenase subunit A (SDHA), von Hippel-Lindau (VHL), and transmembrane protein 127 (TMEM127) gene mutations also harbor the risk for HNPG development. HNPGs in patients with rearranged during transfection (RET), neurofibromatosis type 1 (NF1), and MYC-associated factor X (MAX) gene mutations have been described very infrequently.

CONCLUSION

All patients with HNPGs should be offered a molecular genetic screening. This screening may usually be restricted to mutations of the genes SDHD, SDHB, and SDHC. Certain clinical parameters can help to set up the order in which those genes should be tested.

Signalling pathways in succinate dehydrogenase B-associated renal carcinoma

AIMS

Renal tumours have recently been described in association with mutations in the gene encoding the B subunit of succinate dehydrogenase, a mitochondrial Krebs cycle and electron transport chain enzyme (SDHB-associated renal cell carcinomas). The aim of this study was to investigate the roles of different signalling pathways in the pathogenesis of these tumours.

METHODS AND RESULTS

We used immunohistochemistry and antibodies against phospho-specific epitopes to examine the activity of three potential signalling pathways in tumour cells of three genetically confirmed cases of SDHB-associated renal cell carcinomas. We found no evidence supporting a role for either the mTOR [p-mTOR (Ser2448), p-S6 riboprotein (Ser235/236)] or hypoxia-inducible (carbonic anhydrase 9 and EGFR) pathways. However, there was immunohistochemical reactivity for phosphorylated AMP-dependent kinase (p-AMPK Thr172) and glycogen synthase kinase 3 (GSK3) phosphorylation (p-GSK3 Ser12), and nuclear expression of cyclin D1.

CONCLUSIONS

We suggest that these tumours may arise through a mechanism involving ATP depletion, activation of AMPK, and induction of cyclin D1, and that this may be a unique pathway of tumour development that has the potential for therapeutic intervention in these rare tumours.

A study exploring critical pathways in clear cell renal cell carcinoma

Renal cell carcinoma (RCC) is the most lethal type of cancer in the urinary system and often presents as a metastatic disease. Furthermore, there are no effective treatments for the disease. Several studies based on gene expression profiling have been performed with the aim of gaining insights into the pathogenesis of RCC; however, few studies have investigated RCC at the pathway level to search for the possible pathways involved in clear cell RCC (CCRCC). In this study, gene set enrichment analysis (GSEA) was conducted on microarray datasets from CCRCC tissue. DAVID functional enrichment analysis was performed based on the dysregulated genes that were identified in a meta-analysis performed on the microarray datasets from CCRCC tissue. In GSEA, 17 down- and 12 upregulated pathways coexisted in six datasets. The majority of the upregulated pathways were associated with the immune system. In addition, 32 dysregulated pathways were obtained from DAVID functional enrichment analysis, based on the abnormal genes identified by meta-analysis. This study demonstrated that cross-GSEA is a useful method for exploring the critical pathways involved CCRCC; however, an individual dataset with a small sample may introduce bias. A cross-GSEA based on certain well-designed datasets may be required to further the progress made in this study, following the analysis of its results.

Non-clear cell renal cancer: disease-based management and opportunities for targeted therapeutic approaches

A better understanding of the biology of renal cell carcinoma (RCC) has significantly changed the treatment paradigm of the disease. Several novel vascular endothelial growth factor (VEGF) and mammalian target of rapamycin (mTOR) inhibitors have been approved recently by the US Food and Drug Administration. Unfortunately, the vast majority of clinical trials conducted today have been aimed to include patients with clear cell RCC, which remains the most common histologic subtype of the disease. Non-clear cell RCC represents approximately 20%-25% of all RCC patients. Non-clear cell RCC is made up of multiple histologic subtypes, each with a different molecular printing profile. Although VEGF and TORC inhibitors are commonly used in the management of this cohort of patients, non-clear cell histologies do not appear to be related to the von Hippel-Lindau gene (VHL). As such, the clinical efficacy of the existing agents is quite limited. There is a need to develop more rational therapeutic approaches that specifically target the biology of each of the different subtypes of non-clear cell RCC. In this review, we discuss molecular and clinical characteristics of each of the non-clear cell RCC subtypes and describe ongoing efforts to develop novel agents for this subset of patients.

A novel mutation (P236S) in the succinate dehydrogenase subunit B gene in a Japanese patient with a posterior mediastinal paraganglioma

Succinate dehydrogenase subunit B gene (SDHB) is associated with the development of hereditary paraganglioma (PGL) and pheochromocytoma (PCC). Here we describe a novel germline mutation in SDHB in a 69-year-old Japanese woman with a posterior mediastinal PGL. We summarize the clinical presentation, diagnostic work-up, and pathological features of a patient with a posterior mediastinal PGL and review the pertinent literature. Direct sequencing of SDHB and SDHD was performed. The patient presented with a posterior mediastinal tumor and was normotensive. She underwent abdominal tumor resection at the age of 38 years, but clinical and pathological diagnoses were unknown. She had no family history of hypertension, PGL, or PCC. Imaging studies suggested that the tumor was neurogenic. Endocrinological examinations showed normal plasma catecholamine levels. The tumor was completely removed without metastasis. Pathological findings confirmed PGL. Immunohistochemical staining showed that the tumor cells were positive for chromogranin A, synaptophysin, and CD56, and the Ki67 index was low (<1 %). The patient has not experienced recurrence or metastasis for the last 5 years. DNA sequencing revealed a novel P236S (c.843 C > T) mutation in SDHB. The P236S germline mutation in SDHB was associated with posterior mediastinal PGL. Strict follow-up of the patient is necessary because the SDHB mutation may be related to malignancy.

Key pathways and genes controlling the development and progression of clear cell renal cell carcinoma (ccRCC) based on gene set enrichment analysis

Background

Clear-cell renal cell carcinoma (ccRCC) is one of the most common types of kidney cancer in adults; however, its causes are not completely understood. The study was designed to filter the key pathways and genes associated with the occurrence or development of ccRCC, acquaint its pathogenesis at gene and pathway level, to provide more theory evidence and targeted therapy for ccRCC.

Methods

Gene set enrichment analysis (GSEA) and meta-analysis (Meta) were used to screen the critical pathways and genes which may affect the occurrence and progression of ccRCC on the transcription level. Corresponding pathways of significant genes were obtained with the online website DAVID (http://david.abcc.ncifcrf.gov/).

Results

Thirty seven consistent pathways and key genes in these pathways related to ccRCC were obtained with combined GSEA and meta-analysis. These pathways were mainly involved in metabolism, organismal systems, cellular processes and environmental information processing.

Conclusion

The gene pathways that we identified could provide insight concerning the development of ccRCC. Further studies are needed to determine the biological function for the positive genes.

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.

10 rare tumors that warrant a genetics referral

The number of described cancer susceptibility syndromes continues to grow, as does our knowledge on how to manage these syndromes with the aim of early detection and cancer prevention. Oncologists now have greater responsibility to recognize patterns of cancer that warrant referral for a genetics consultation. While some patterns of common cancers are easy to recognize as related to hereditary cancer syndromes, there are a number of rare tumors that are highly associated with cancer syndromes yet are often overlooked given their infrequency. We present a review of ten rare tumors that are strongly associated with hereditary cancer predisposition syndromes: adrenocortical carcinoma, carcinoid tumors, diffuse gastric cancer, fallopian tube/primary peritoneal cancer, leiomyosarcoma, medullary thyroid cancer, paraganglioma/pheochromocytoma, renal cell carcinoma of chromophobe, hybrid oncocytoic, or oncocytoma histology, sebaceous carcinoma, and sex cord tumors with annular tubules. This review will serve as a guide for oncologists to assist in the recognition of rare tumors that warrant referral for a genetic consultation.

Rare insights into cancer biology

Cancer-associated mutations have been identified in the metabolic genes succinate dehydrogenase (SDH), fumarate hydratase (FH) and isocitrate dehydrogenase (IDH), advancing and challenging our understanding of cellular function and disease mechanisms and providing direct links between dysregulated metabolism and cancer. Some striking parallels exist in the cellular consequences of the genetic mutations within this triad of cancer syndromes, including accumulation of oncometabolites and competitive inhibition of 2-oxoglutarate-dependent dioxygenases, particularly, hypoxia-inducible factor (HIF) prolyl hydroxylases, JmjC domain-containing histone demethylases (part of the JMJD family) and the ten-eleven translocation (TET) family of 5methyl cytosine (5mC) DNA hydroxylases. These lead to activation of HIF-dependent oncogenic pathways and inhibition of histone and DNA demethylation. Mutations in FH, resulting in loss of enzyme activity, predispose affected individuals to a rare cancer, hereditary leiomyomatosis and renal cell cancer (HLRCC), characterised by benign smooth muscle cutaneous and uterine tumours (leiomyomata) and an aggressive form of collecting duct and type 2 papillary renal cancer. Interestingly, loss of FH activity results in the accumulation of high levels of fumarate that can lead to the non-enzymatic modification of cysteine residues in multiple proteins (succination) and in some cases to their disrupted function. Here we consider that the study of rare diseases such as HLRCC, combining analyses of human tumours and cell lines with in vitro and in vivo murine models has provided novel insights into cancer biology associated with dysregulated metabolism and represents a useful paradigm for cancer research.

Germline PTEN mutation Cowden syndrome: an underappreciated form of hereditary kidney cancer

PURPOSE

Cowden syndrome is a hereditary cancer syndrome associated with a germline mutation in PTEN. Patients are predisposed to multiple malignancies including renal cell carcinoma.

MATERIALS AND METHODS

Patients with Cowden syndrome were evaluated as part of a clinical protocol. Those with a history of renal cell carcinoma underwent review of clinical features, tumor characteristics and family history. Renal tumors were evaluated for loss of heterozygosity.

RESULTS

Among 24 patients with Cowden syndrome 4 were identified with renal cell carcinoma (16.7%). Three patients had solitary tumors, 2 with papillary type I histology and 1 with clear cell histology. The fourth patient had bilateral, synchronous chromophobe tumors. No patients had a prior family history of renal cell carcinoma. All patients with renal cell carcinoma had dermatologic manifestations of Cowden syndrome and had macrocephaly. Loss of heterozygosity at the PTEN mutation was identified in 4 tumors (80%). No genotype-phenotype association was found, as the same mutation was identified in different renal cell carcinoma histologies.

CONCLUSIONS

Renal cell carcinoma is an underappreciated feature of Cowden syndrome. As most patients lack a prior family history or a distinctive renal cell carcinoma histology, recognition of the associated nonrenal features should target referral for genetic counseling. PTEN loss of heterozygosity is common in Cowden syndrome renal tumors. Because loss of PTEN can activate mTOR and mTOR inhibitors are Food and Drug Administration approved to treat renal cell carcinoma, these agents have clinical potential in renal cell carcinoma associated with Cowden syndrome.

Familial SDHA mutation associated with pituitary adenoma and pheochromocytoma/paraganglioma

CONTEXT

Reports of the coexistence of pituitary adenomas and pheochromocytoma/paraganglioma are uncommon. Recently germline mutations in 2 of the genes encoding succinate dehydrogenase, SDHC and SDHD, were associated with pituitary tumors.

OBJECTIVE

Our aim was to determine whether the development of a pituitary adenoma was associated with SDHA mutation.

PATIENTS

A 46-year-old female presented with carotid body paraganglioma (proband). Subsequently the proband's son was diagnosed with a nonfunctioning pituitary macroadenoma at age 30 years.

RESULTS

An immunohistochemical analysis of the resected paraganglioma and pituitary adenoma revealed the loss of succinate dehydrogenase subunit B and succinate dehydrogenase subunit A (SDHA) expression in both tumors, with the preservation of staining in nonneoplastic tissue. Mutation analysis showed a novel SDHA mutation (c.1873C>T, p.His625Tyr) in the germline of the proband as well as in the proband's son. In the paraganglioma of the proband, in addition to the germline mutation, a somatic mutation was observed (c.1865G>A, p.Trp622*). In the pituitary adenoma of the proband's son, loss of SDHA immunoreactivity was paradoxically accompanied by loss of the mutant allele.

CONCLUSIONS

This is the first report of a pituitary adenoma arising in the setting of germline SDHA mutation. The loss of SDHA protein expression in both the paraganglioma (proband) and pituitary adenoma (proband's son) argues strongly for a causative role of SDHA mutation. This report further strengthens the link between pituitary neoplasia and germline SDH mutation. Although pituitary adenomas appear rare among patients carrying SDH subunit mutations, they may have been underrecognized due to the low penetrance of disease and lack of systematic surveillance.

Reduced succinate dehydrogenase B expression is associated with growth and de-differentiation of colorectal cancer cells

Succinate dehydrogenases (SDH), including SDHA, SDHB, SDHC, and SDHD, form the respiratory complex II in the mitochondria and play an important role in cell growth and homeostasis. In order to evaluate the expression and functional significance of SDH in colorectal cancer, the expression of four SDH subunits was analyzed, and SDHB protein was found to be significantly lower in colorectal cancer tissues. In vitro experiments including cell growth assay, colony formation assay, cell cycle analysis, and nude mouse xenograft of SDHB-transfected colorectal cancer cell line SW620 were performed. Notably, reduced SDHB expression in tumor tissues was associated with tumor de-differentiation, and restoration of SDHB could inhibit the growth of cancer cells both in vitro and in vivo. Furthermore, cDNA microarray of SDHB-transfected cell line showed that most of the differentially expressed genes are related to cell cycle control and cell proliferation. Thus, we conclude that SDHB expression is significantly decreased in human colorectal cancer tissues, and reconstitution of SDHB in colorectal cancer may be a potential therapeutic approach to inhibit aggressiveness of colorectal cancer.

The metabolic basis of kidney cancer

Kidney cancer is not a single disease; it is made up of a number of different types of cancer that occur in the kidney. Each of these different types of kidney cancer can have a different histology, have a different clinical course, can respond differently to therapy and is caused by a different gene. Kidney cancer is essentially a metabolic disease; each of the known genes for kidney cancer, VHL, MET, FLCN, TSC1, TSC2, TFE3, TFEB, MITF, fumarate hydratase (FH), succinate dehydrogenase B (SDHB), succinate dehydrogenase D (SDHD), and PTEN genes is involved in the cells ability to sense oxygen, iron, nutrients or energy. Understanding the metabolic basis of kidney cancer will hopefully provide the foundation for the development of effective forms of therapy for this disease.

Physiological consequences of complex II inhibition for aging, disease, and the mKATP channel

In recent years, it has become apparent that there exist several roles for respiratory complex II beyond metabolism. These include: (i) succinate signaling, (ii) reactive oxygen species (ROS) generation, (iii) ischemic preconditioning, (iv) various disease states and aging, and (v) a role in the function of the mitochondrial ATP-sensitive K(+) (mKATP) channel. This review will address the involvement of complex II in each of these areas, with a focus on how complex II regulates or may be involved in the assembly of the mKATP. This article is part of a Special Issue entitled: Respiratory complex II: Role in cellular physiology and disease.

The power of yeast to model diseases of the powerhouse of the cell

Mitochondria participate in a variety of cellular functions. As such, mitochondrial diseases exhibit numerous clinical phenotypes. Because mitochondrial functions are highly conserved between humans and Saccharomyces cerevisiae, yeast are an excellent model to study mitochondrial disease, providing insight into both physiological and pathophysiological processes.

Succinate dehydrogenase (SDHx) mutations in pituitary tumors: could this be a new role for mitochondrial complex II and/or Krebs cycle defects?

Succinate dehydrogenase (SDH) or mitochondrial complex II is a multimeric enzyme that is bound to the inner membrane of mitochondria and has a dual role as it serves both as a critical step of the tricarboxylic acid or Krebs cycle and as a member of the respiratory chain that transfers electrons directly to the ubiquinone pool. Mutations in SDH subunits have been implicated in the formation of familial paragangliomas (PGLs) and/or pheochromocytomas (PHEOs) and in Carney-Stratakis syndrome. More recently, SDH defects were associated with predisposition to a Cowden disease phenotype, renal, and thyroid cancer. We recently described a kindred with the coexistence of familial PGLs and an aggressive GH-secreting pituitary adenoma, harboring an SDHD mutation. The pituitary tumor showed loss of heterozygosity at the SDHD locus, indicating the possibility that SDHD's loss was causatively linked to the development of the neoplasm. In total, 29 cases of pituitary adenomas presenting in association with PHEOs and/or extra-adrenal PGLs have been reported in the literature since 1952. Although a number of other genetic defects are possible in these cases, we speculate that the association of PHEOs and/or PGLs with pituitary tumors is a new syndromic association and a novel phenotype for SDH defects.

Identification of three new variants of SDHx genes in a cohort of Portuguese patients with extra-adrenal paragangliomas

BACKGROUND

Extra-adrenal paragangliomas (PGL) are rare neoplasms occurring in sporadic and familial forms, the latter mostly in association with germline mutations of SD- HB, SDHC or SDHD genes.

AIM

Characterize frequency and spectrum of germline mutations among a cohort of Portuguese patients with extra-adrenal PGL.

DESIGN

Molecular and clinical data were reviewed on 44 patients referred for genetic testing by a single laboratory.

RESULTS

Genetic analysis identified 11 patients with head and neck PGL (30.6%) positive for SD- Hx gene mutations (6 SDHD, 4 SDHB, 1 SDHC) and 4 patients with abdominal or pelvic PGL (50%) positive for SDHx gene mutations (4 SDHB). Large deletions made up about 20% of the mutations detected. Mutation carriers were younger and more frequently had multiple or malignant PGL than patients without mutations. Only 11% of the head and neck PGL were secretory. In contrast, 100% of the abdominal or pelvic PGL were secretory. Five patients had a malignant PGL (4 SDHB, 1 apparently sporadic). Three novel mutations were identified: two in the SDHD gene (c.411delT [p.Leu139PhefsX29] and c.371_390del20insGG [p.Ala124_Ala130delinsGly]), one in the SDHB gene (c.49A>G [p.Thr17Ala]). The SDHD variant c.411delT [p.Leu139PhefsX29] was present in 3 apparently unrelated patients. Molecular genetic testing of 22 relatives disclosed 16 mutation carriers.

CONCLUSIONS

Genetic analysis identified 15 patients (34.1%) and 16 at-risk individuals (72.7%) positive for SDHx gene mutations. The finding of three novel mutations broadens the mutational profile of the mitochondrial complex II succinate dehydrogenase genes reported in other large European series of patients with paragangliomas. Further studies are needed to clarify whether the high frequency of the SDHD variant c.411delT [p.Leu139PhefsX29] corresponds to a founder mutation.

Succinate dehydrogenase kidney cancer: an aggressive example of the Warburg effect in cancer

PURPOSE

Recently, a new renal cell cancer syndrome has been linked to germline mutation of multiple subunits (SDHB/C/D) of the Krebs cycle enzyme, succinate dehydrogenase. We report our experience with the diagnosis, evaluation and treatment of this novel form of hereditary kidney cancer.

MATERIALS AND METHODS

Patients with suspected hereditary kidney cancer were enrolled on a National Cancer Institute institutional review board approved protocol to study inherited forms of kidney cancer. Individuals from families with germline SDHB, SDHC and SDHD mutations, and kidney cancer underwent comprehensive clinical and genetic evaluation.

RESULTS

A total of 14 patients from 12 SDHB mutation families were evaluated. Patients presented with renal cell cancer at an early age (33 years, range 15 to 62), metastatic kidney cancer developed in 4 and some families had no manifestation other than kidney tumors. An additional family with 6 individuals found to have clear cell renal cell cancer that presented at a young average age (47 years, range 40 to 53) was identified with a germline SDHC mutation (R133X) Metastatic disease developed in 2 of these family members. A patient with a history of carotid body paragangliomas and an aggressive form of kidney cancer was evaluated from a family with a germline SDHD mutation.

CONCLUSIONS

SDH mutation associated renal cell carcinoma can be an aggressive type of kidney cancer, especially in younger individuals. Although detection and management of early tumors is most often associated with a good outcome, based on our initial experience with these patients and our long-term experience with hereditary leiomyomatosis and renal cell carcinoma, we recommend careful surveillance of patients at risk for SDH mutation associated renal cell carcinoma and wide surgical excision of renal tumors.

The role of complex II in disease

Genetically defined mitochondrial deficiencies that result in the loss of complex II function lead to a range of clinical conditions. An array of tumor syndromes caused by complex II-associated gene mutations, in both succinate dehydrogenase and associated accessory factor genes (SDHA, SDHB, SDHC, SDHD, SDHAF1, SDHAF2), have been identified over the last 12 years and include hereditary paraganglioma-pheochromocytomas, a diverse group of renal cell carcinomas, and a specific subtype of gastrointestinal stromal tumors (GIST). In addition, congenital complex II deficiencies due to inherited homozygous mutations of the catalytic components of complex II (SDHA and SDHB) and the SDHAF1 assembly factor lead to childhood disease including Leigh syndrome, cardiomyopathy and infantile leukodystrophies. The role of complex II subunit gene mutations in tumorigenesis has been the subject of intensive research and these data have led to a variety of compelling hypotheses. Among the most widely researched are the stabilization of hypoxia inducible factor 1 under normoxia, and the generation of reactive oxygen species due to defective succinate:ubiquinone oxidoreductase function. Further progress in understanding the role of complex II in disease, and in the development of new therapeutic approaches, is now being hampered by the lack of relevant cell and animal models. This article is part of a Special Issue entitled: Respiratory complex II: Role in cellular physiology and disease.

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.

Cholesterol and the development of clear-cell renal carcinoma

The majority of kidney cancers are clear-cell carcinomas (ccRCC), characterized by the accumulation of cholesterol, cholesterol esters, other neutral lipids and glycogen. Rather than being a passive bystander, the clear-cell phenotype is suggested to be a biomarker of deregulated cholesterol and lipid biosynthesis, which plays an important role in development of the disease. One clue to this relationship has come from the elucidation of the hereditary kidney cancer gene, TRC8, which functions partly to degrade key regulators of endogenous cholesterol and lipid biosynthesis. In addition, deregulation of the mevalonate pathway has been shown to play a key role in cellular transformation and invasion. These findings are supported by considerable epidemiologic data linking obesity and the deregulation of lipid biosynthesis to ccRCC.

Succinate dehydrogenase B subunit immunohistochemical expression predicts aggressiveness in well differentiated neuroendocrine tumors of the ileum

Immunohistochemical loss of the succinate dehydrogenase subunit B (SDHB) has recently been reported as a surrogate biomarker of malignancy in sporadic and familial pheocromocytomas and paragangliomas through the activation of hypoxia pathways. However, data on the prevalence and the clinical implications of SDHB immunoreactivity in ileal neuroendocrine tumors are still lacking. Thirty-one consecutive, advanced primary midgut neuroendocrine tumors and related lymph node or liver metastases from 24 males and seven females were immunohistochemically assessed for SDHB. All patients were G1 tumors (Ki-67 labeling index ≤2%). SDHB immunohistochemistry results were expressed as immunostaining intensity and scored as low or strong according to the internal control represented by normal intestinal cells. Strong positivity for SDHB, with granular cytoplasmatic reactivity, was found in 77% of primary tumors (T), whilst low SDHB expression was detected in 90% of metastases (M). The combined analysis (T+M) confirmed the loss of SDHB expression in 82% of metastases compared to 18% of primary tumors. SDHB expression was inversely correlated with Ki-67 labeling index, which accounted for 1.54% in metastastic sites and 0.7% in primary tumors. A correlation between SDHB expression loss, increased Ki-67 labeling index and biological aggressiveness was shown in advanced midgut neuroendocrine tumors, suggesting a role of tumor suppressor gene.

Familial renal cancer as an indicator of hereditary leiomyomatosis and renal cell cancer syndrome

Hereditary Leiomyomatosis and Renal Cell Carcinoma (HLRCC) is a hereditary condition which typically presents with cutaneous and uterine leiomyomata. Papillary type II renal cell carcinoma and other less common histologic subtypes of renal cancer have been reported in HLRCC. We describe the case of a 31-year-old man in which the pathology review of his renal carcinoma and a positive family history of renal carcinoma allowed for the identification of a pathogenic mutation in the FH gene (c.698G>A;p.R233H) confirming the diagnosis of HLRCC. Recognition of this syndrome allowed for appropriate surveillance as well as identification of at-risk family members. Pathology review is essential for accurate diagnosis of a hereditary cancer syndrome in the setting of familial renal cancer.

Succinate dehydrogenase-deficient tumors: diagnostic advances and clinical implications

Just over 10 years ago, germline mutations in SDHD, a gene that encodes 1 of the 4 proteins of the succinate dehydrogenase (SDH) complex, were reported in a subset of patients with hereditary paraganglioma-pheochromocytoma syndrome. Since that time, rapid discoveries have been made in this area. It is now recognized that all of the SDH genes are involved in the tumorigenesis of not only paragangliomas/pheochromocytomas, but also other tumor types, most notably gastrointestinal stromal tumors. This review will outline the genetics of SDH-deficient tumors, discuss possible mechanisms of tumorigenesis, and describe how these tumors can be identified by immunohistochemistry.

State of the science: an update on renal cell carcinoma

Renal cell carcinomas (RCC) are emerging as a complex set of diseases that are having a major socioeconomic impact and showing a continued rise in incidence throughout the world. As the field of urologic oncology faces these trends, several major genomic and mechanistic discoveries are altering our core understanding of this multitude of cancers, including several new rare subtypes of renal cancers. In this review, these new findings are examined and placed in the context of the well-established association of clear cell RCC (ccRCC) with mutations in the von Hippel-Lindau (VHL) gene and resultant aberrant hypoxia inducible factor (HIF) signaling. The impact of novel ccRCC-associated genetic lesions on chromatin remodeling and epigenetic regulation is explored. The effects of VHL mutation on primary ciliary function, extracellular matrix homeostasis, and tumor metabolism are discussed. Studies of VHL proteostasis, with the goal of harnessing the proteostatic machinery to refunctionalize mutant VHL, are reviewed. Translational efforts using molecular tools to elucidate discriminating features of ccRCC tumors and develop improved prognostic and predictive algorithms are presented, and new therapeutics arising from the earliest molecular discoveries in ccRCC are summarized. By creating an integrated review of the key genomic and molecular biological disease characteristics of ccRCC and placing these data in the context of the evolving therapeutic landscape, we intend to facilitate interaction among basic, translational, and clinical researchers involved in the treatment of this devastating disease, and accelerate progress toward its ultimate eradication.

Biallelic inactivation of the SDHC gene in renal carcinoma associated with paraganglioma syndrome type 3

The etiology and pathogenesis of renal cell carcinoma (RCC) are only partially understood. Key findings in hereditary RCC, which may be site specific or a component of a syndrome, have contributed to our current understanding. Important heritable syndromes of RCC are those associated with pheochromocytoma, especially von Hippel-Lindau disease (VHL) associated with germline VHL mutations, and pheochromocytoma and paraganglioma syndrome (PGL) associated with mutations in one of the four genes (SDHA-D) encoding succinate dehydrogenase. A subset of individuals with SDHB and SDHD germline DNA mutations and variants develop RCC. RCC has never been described as a component of SDHC-associated PGL3. The European-American Pheochromocytoma and Paraganglioma Registry comprises 35 registrants with germline SDHC mutations. A new registrant had carotid body tumor (CBT) and his mother had CBT and bilateral RCC. Blood DNA, paragangliomas, and RCCs were analyzed for mutations and loss-of-heterozygosity (LOH) in/flanking SDHC and VHL. The proband with unilateral CBT had a germline SDHC c.3G>A (p.M1I) mutation. His mutation-positive mother had CBT at age 42, clear cell RCC (ccRCC) at age 68, and papillary RCC (pRCC) at age 69. Both paraganglial tumors showed somatic LOH of the SDHC locus. Both ccRCC and pRCC did not have a somatic SDHC mutation but showed LOH for intragenic and flanking markers of the SDHC locus. LOH was also present for the VHL locus. Our findings suggest that RCC is a component of PGL3. Biallelic inactivation of the SDHC gene may represent a new pathway of pathogenesis of syndromic and nonsyndromic RCC, perhaps of both clear cell and papillary histologies.

Genetic syndromes associated with renal cell carcinoma: a review

AIMS

A review of recent knowledge on heredital syndromes related to renal cell carcinoma.

METHODS

Aim of this review was to summarize the recent knowledge of genetic syndromes associated with renal cell carcinoma.

RESULTS

Summary of incidence and factors modulating risk of hereditary renal cell carcinoma development.

CONCLUSIONS

Hereditary forms of RCC are relatively rare. Their study is beneficial in many ways. In individuals at a higher risk of a hereditary syndrome, the knowledge of hereditary forms may help to significantly decrease the impact of the hereditary disease. In the general population, knowledge acquired by the study of hereditary forms of RCC may in the future contribute to both diagnosis and treatment of sporadic tumours.

Renal cancer: oxygen meets metabolism

Over the last two decades molecular studies of inherited tumor syndromes that are associated with the development of kidney cancer have led to the identification of genes and biochemical pathways, which play key roles in the malignant transformation of renal epithelial cells. Some of these findings have broad biological impact and extend beyond renal cancer. This review's focus is on the von Hippel-Lindau (VHL)/hypoxia-inducible factor (HIF) oxygen-sensing pathway and its role in physiology, energy metabolism and tumorigenesis.

Pheochromocytoma and paraganglioma: understanding the complexities of the genetic background

Pheochromocytomas and paragangliomas (PCC/PGL) are tumors derived from the adrenal medulla or extra-adrenal ganglia, respectively. They are rare and often benign tumors that are associated with high morbidity and mortality due to mass effect and high circulating catecholamines. Although most PCCs and PGLs are thought to be sporadic, over one third are associated with 10 known susceptibility genes. Mutations in three genes causing well characterized tumor syndromes are associated with an increased risk of developing PCCs and PGLs, including VHL (von Hippel-Lindau disease), NF1 (Neurofibromatosis Type 1), and RET (Multiple Endocrine Neoplasia Type 2). Mutations in any of the succinate dehydrogenase (SDH) complex subunit genes (SDHA, SDHB, SDHC, SDHD) can lead to PCCs and PGLs with variable penetrance, as can mutations in the subunit cofactor, SDHAF2. Recently, two additional genes have been identified, TMEM127 and MAX. Although these tumors are rare in the general population, occurring in two to eight per million people, they are more commonly associated with an inherited mutation than any other cancer type. This review summarizes the known germline and somatic mutations leading to the development of PCC and PGL, as well as biochemical profiling for PCCs/PGLs and screening of mutation carriers.

Paragangliomas and paraganglioma syndromes

Paragangliomas are rare tumors of neural crest origin. They are benign in the majority of cases and are characterized by a strong vascularisation.

In the head and neck region they most commonly occur as carotid body tumors. Jugulotympanic and especially vagal paragangliomas are seen less frequently. Complete surgical resection represents the only curative treatment option even though resection of locally advanced tumors regularly results in lesions of the lower cranial nerves and major vessels.

Appoximately 30% of all head and neck paragangliomas (HNPs) are hereditary and associated with different tumor syndromes. The paraganglioma syndromes 1, 3 and 4 (PGL 1, 3 and 4) make up the majority of those familial cases. PGL 1 is associated with mutations of the succinate dehydrogenase subunit D (SDHD) gene, PGL 3 is caused by SDHC and PGL 4 by SDHB gene mutations. Multiple HNPs and the occurance of HNPs together with pheochromocytomas are seen in SDHD as well as SDHB mutation carriers. In patients with SDHB mutations the risk for the development of malignant paraganglial tumors is significantly higher compared to SDHC and SDHD patients as well as patients with sporadic tumors. SDHC mutation carriers almost exclusively present with benign HNP that are unifocal in the majority of cases. The role of transmission is autosomal dominant for all three symptoms. Interestingly, there is a “parent-of-origin-dependent-inheritance” in subjects with SDHD gene mutations. This means that the disease phenotype may only become present if the mutation is inherited through the paternal line. We recommend screening for mutations of the genes SDHB, SDHC and SDHD in patients with HNPs. Certain clinical parameters can help to set up the order in which the three genes should be tested.

Tumor metabolism as modulator of immune response and tumor progression

About a century ago Otto Warburg observed that tumor cells exhibited increased glycolysis despite the presence of oxygen and stated this metabolic shift to glycolysis as the origin of cancer cell. In the meantime it has become clear, that the altered glucose metabolism is only one piece of the tumor metabolome puzzle. In addition, amino acid, lipid and adenosine metabolism are adapted to fulfill the tumors needs for energy and generation of building blocks such as lipids and nucleotides for new cell structures. The altered tumor metabolism leads to accumulation of specific metabolites in the tumor environment and creates a favorable milieu for tumor growth, progression and metastasis. These tumor-derived metabolites are important players in immune escape mechanisms beside other known factors such as cytokines, chemokines and growth factors. A variety of metabolites re-educate immune cells and prevent an effective immune response against tumor cells. Furthermore, tumor infiltrating immune cells support tumor growth by the secretion of cytokines, growth factors and other metabolic determinants. Hence, a complex interplay of tumor metabolites, cytokines and stromal factors is active in tumors and facilitates their establishment and growth. Pharmacological blockade of tumor metabolites could overcome some limitations of cancer treatment and rescue the endogenous immune response against tumor cells.

Succinate dehydrogenase (SDH) D subunit (SDHD) inactivation in a growth-hormone-producing pituitary tumor: a new association for SDH?

BACKGROUND

Mutations in the subunits B, C, and D of succinate dehydrogenase (SDH) mitochondrial complex II have been associated with the development of paragangliomas (PGL), gastrointestinal stromal tumors, papillary thyroid and renal carcinoma (SDHB), and testicular seminoma (SDHD).

AIM

Our aim was to examine the possible causative link between SDHD inactivation and somatotropinoma.

PATIENTS AND METHODS

A 37-yr-old male presented with acromegaly and hypertension. Other family members were found with PGL. Elevated plasma and urinary levels of catecholamines led to the identification of multiple PGL in the proband in the neck, thorax, and abdomen. Adrenalectomy was performed for bilateral pheochromocytomas (PHEO). A GH-secreting macroadenoma was also found and partially removed via transsphenoidal surgery (TTS). Genetic analysis revealed a novel SDHD mutation (c.298_301delACTC), leading to a frame shift and a premature stop codon at position 133 of the protein. Loss of heterozygosity for the SDHD genetic locus was shown in the GH-secreting adenoma. Down-regulation of SDHD protein in the GH-secreting adenoma by immunoblotting and immunohistochemistry was found. A literature search identified other cases of multiple PGL and/or PHEO in association with pituitary tumors.

CONCLUSION

We describe the first kindred with a germline SDHD pathogenic mutation, inherited PGL, and acromegaly due to a GH-producing pituitary adenoma. SDHD loss of heterozygosity, down-regulation of protein in the GH-secreting adenoma, and decreased SDH enzymatic activity supports SDHD's involvement in the pituitary tumor formation in this patient. Older cases of multiple PGL and PHEO and pituitary tumors in the literature support a possible association between SDH defects and pituitary tumorigenesis.