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Key Points Over half of all phaeochromocytoma and/or paraganglioma (PPGL) can be attributed to genetic alterations 80% of inherited PPGLs are caused by a germline mutation in VHL or the SDHx group of genes Genetic testing is indicated for all patients with PPGLs, as identification of the underlying mutation guides patient management and genetic counselling Gene expression profiling can be used to classify PPGLs, assigning them to either an angiogenic cluster or a kinase signalling cluster, each of which has specific treatment targets DNA methylation profiling has revealed a hypermethylated cluster that is specific to tumours related to the SDHx genes and FH that accounts for the malignant and noradrenergic phenotype of tumours related to mutations in these genes Genomic studies of PPGLs are generating important findings that should pave the way for personalized medicine for affected patients During the past 15 years, our understanding of phaeochromocytoma and/or paraganglioma and the management of affected patients and their relatives have been revolutionized. Particular progress has been made in our understanding of the genetic changes underlying these tumours. This Review discusses the key advances that have occurred over this period. Paragangliomas and phaeochromocytomas are neuroendocrine tumours whose pathogenesis and progression are very strongly influenced by genetics. A germline mutation in one of the susceptibility genes identified so far explains ∼40% of all cases; the remaining 60% are thought to be sporadic cases. At least one-third of these sporadic tumours contain a somatic mutation in a predisposing gene. Genetic testing, which is indicated in every patient, is guided by the clinical presentation as well as by the secretory phenotype and the immunohistochemical characterization of the tumours. The diagnosis of an inherited form drives clinical management and tumour surveillance. Different 'omics' profiling methods have provided a neat classification of these tumours in accordance with their genetic background. Transcriptomic studies have identified two main molecular pathways that underlie development of these tumours, one in which the hypoxic pathway is activated (cluster 1) and another in which the MAPK and mTOR (mammalian target of rapamycin) signalling pathways are activated (cluster 2). DNA methylation profiling has uncovered a hypermethylator phenotype in tumours related to SDHx genes (a group of genes comprising SDHA , SDHB , SDHC , SDHD and SDHAF2 ) and revealed that succinate acts as an oncometabolite, inhibiting 2-oxoglutarate-dependent dioxygenases, such as hypoxia-inducible factor prolyl-hydroxylases and histone and DNA demethylases. 'Omics' data have suggested new therapeutic targets for patients with a malignant tumour. In the near future, new 'omics'-based tests are likely to be transferred into clinical practice with the goal of establishing personalized medical management for affected patients.

Succinate dehydrogenase (SDH) inhibitors (SDHIs) are used worldwide to limit the proliferation of molds on plants and plant products. However, as SDH, also known as respiratory chain (RC) complex II, is a universal component of mitochondria from living organisms, highly conserved through evolution, the specificity of these inhibitors toward fungi warrants investigation. We first establish that the human, honeybee, earthworm and fungal SDHs are all sensitive to the eight SDHIs tested, albeit with varying IC50 values, generally in the micromolar range. In addition to SDH, we observed that five of the SDHIs, mostly from the latest generation, inhibit the activity of RC complex III. Finally, we show that the provision of glucose ad libitum in the cell culture medium, while simultaneously providing sufficient ATP and reducing power for antioxidant enzymes through glycolysis, allows the growth of RC-deficient cells, fully masking the deleterious effect of SDHIs. As a result, when glutamine is the major carbon source, the presence of SDHIs leads to time-dependent cell death. This process is significantly accelerated in fibroblasts derived from patients with neurological or neurodegenerative diseases due to RC impairment (encephalopathy originating from a partial SDH defect) and/or hypersensitivity to oxidative insults (Friedreich ataxia, familial Alzheimer's disease).

Low-grade oncocytic renal tumor (LOT) is an emerging provisional entity, described as rare solid renal oncocytic/eosinophilic tumor sharing diffuse CK7 and negative CD117 immunoprofile. The links between LOT and other eosinophilic chromophobe like-renal cell carcinomas (RCC) are currently discussed. We sequenced tumoral DNA with a next generation sequencing panel for kidney cancer and carried out immunohistochemical analyses with CK7, CD117, SDHB, 4EBP1-P, S6K-P, and FOXI1 antibodies in a series of ten cases of LOT (9 females, 1 male; mean age at surgery: 66 years, 42.3 to 83.4) retrospectively diagnosed from a cohort of 272 tumors initially classified as chromophobe RCC (CHRCC). All LOT were single, without known hereditary predisposition, classified stage pT1 (70%), pT2 (20%) or pT3a (10%). Morphological features were similar to previous descriptions and clinical behavior was indolent for the six cases with available follow-up. We identified genetic variations in mTOR pathway related genes in 80% of cases, MTOR (7 cases) or TSC1 (1 case). Expression of FOXI1 was absent in all cases. In 9 LOT, 4EBP1-P and S6K-P were overexpressed, suggesting mTOR pathway activation. Our data highlights the major role of mTOR pathway in tumorigenesis of LOT mostly due to activating MTOR gene variations. Absence of FOXI1 expression is a strong argument to distinguish LOT from eosinophilic CHRCC and to bring them closer to other recently described FOXI1 negative eosinophilic-CHRCC like with MTOR/TSC mutations. Altogether, our data argue to consider LOT as a distinct entity with a favorable clinical outcome. However, in case of metastasis, an accurate diagnosis of LOT would be essential for the patient’s management and could allow targeted therapy.

The tricarboxylic acid (TCA) cycle is a central metabolic pathway responsible for supplying reducing potential for oxidative phosphorylation and anabolic substrates for cell growth, repair and proliferation. As such it thought to be essential for cell proliferation and tissue homeostasis. However, since the initial report of an inactivating mutation in the TCA cycle enzyme complex, succinate dehydrogenase (SDH) in paraganglioma (PGL), it has become clear that some cells and tissues are not only able to survive with a truncated TCA cycle, but that they are also able of supporting proliferative phenotype observed in tumours. Here, we show that loss of SDH activity leads to changes in the metabolism of non-essential amino acids. In particular, we demonstrate that pyruvate carboxylase is essential to re-supply the depleted pool of aspartate in SDH-deficient cells. Our results demonstrate that the loss of SDH reduces the metabolic plasticity of cells, suggesting vulnerabilities that can be targeted therapeutically. Evidence suggests that the TCA cycle enzyme complex succinate dehydrogenase (SDH) may be dispensable for cell proliferation in some cancer cells. Here the authors show that SDH deficient cells become dependent on the mitochondrial enzyme pyruvate carboxylase for aspartate production and proliferation.

BackgroundKnowing the genetic status of patients affected by paragangliomas and pheochromocytomas (PPGL) is important for the guidance of their management and their relatives. Our objective was to improve the diagnostic performances of PPGL genetic testing by next-generation sequencing (NGS).MethodsWe developed a custom multigene panel, which includes 17 PPGL genes and is compatible with both germline and tumour DNA screening. The NGS assay was first validated in a retrospective cohort of 201 frozen tumour DNAs and then applied prospectively to 623 DNAs extracted from leucocytes, frozen or paraffin-embedded PPGL tumours.ResultsIn the retrospective cohort, the sensitivity of the NGS assay was evaluated at 100% for point and indels mutations and 86% for large rearrangements. The mutation rate was re-evaluated from 65% (132/202) to 78% (156/201) after NGS analysis. In the prospective cohort, NGS detected not only germline and somatic mutations but also co-occurring variants and mosaicism. A mutation was identified in 74% of patients for whom both germline and tumour DNA were available.ConclusionThe analysis of 824 DNAs from patients with PPGL demonstrated that NGS assay significantly improves the performances of PPGL genetic testing compared with conventional methods, increasing the rate of identified mutations and identifying rare genetic mechanisms.

The development of pheochromocytomas and paragangliomas is strongly linked to the presence of germline mutations in more than 15 predisposing genes. Among them, germline and somatic VHL mutations account for ~10% of all cases. In contrast with SDHA and SDHB immunohistochemistries that are routinely used to validate SDHx gene mutations, there is no such tool available for VHL mutations. The aim of this study was to evaluate whether CA9 immunostaining could be used as a tool to predict the presence or validate the pathogenicity of VHL gene mutations in paraganglioma. Immunohistochemistry for CA9 was performed on 207 tumors. A retrospective series of 100 paragangliomas with known mutation status for paraganglioma susceptibility genes was first investigated. Then, a prospective series of 107 paragangliomas was investigated for CA9 immunostaining followed by germline and/or somatic genetic testing of all paraganglioma susceptibility genes by next-generation sequencing. Cytosolic CA9 protein expression was heterogeneous in the different samples. However, we observed that a membranous CA9 staining was almost exclusively observed in VHL-related cases. Forty two of 48 (88%) VHL- mutated samples showed a CA9 membranous immunostaining. Positive cells were either isolated, varying from 1 or 2 cells (5% of cases) to 10–20 cells per tumor block (35% of cases), grouped in areas of focal positivity representing between 1 and 20% of the tissue section (35% of cases), or widely distributed on 80–100% of the tumor sections (25% of samples). In contrast, 142/159 (91%) of non-VHL-mutated tumors presented no membrane CA9 localization. Our results demonstrate that VHL gene mutations can be predicted or validated reliably by an easy-to-perform and low-cost immunohistochemical procedure. CA9 immunohistochemistry on paragangliomas will improve the diagnosis of VHL -related disease, which is important for the surveillance and therapeutic management of paraganglioma patients, and in case of germline mutation, their family members.

Pheochromocytomas and paragangliomas (PCCs/PGLs) are neural crest-derived tumours with a very strong genetic component. Here we report the first integrated genomic examination of a large collection of PCC/PGL. SNP array analysis reveals distinct copy-number patterns associated with genetic background. Whole-exome sequencing shows a low mutation rate of 0.3 mutations per megabase, with few recurrent somatic mutations in genes not previously associated with PCC/PGL. DNA methylation arrays and miRNA sequencing identify DNA methylation changes and miRNA expression clusters strongly associated with messenger RNA expression profiling. Overexpression of the miRNA cluster 182/96/183 is specific in SDHB -mutated tumours and induces malignant traits, whereas silencing of the imprinted DLK1-MEG3 miRNA cluster appears as a potential driver in a subgroup of sporadic tumours. Altogether, the complete genomic landscape of PCC/PGL is mainly driven by distinct germline and/or somatic mutations in susceptibility genes and reveals different molecular entities, characterized by a set of unique genomic alterations. Pheochromocytomas and paragangliomas (PCCs/PGLs) are rare neuroendocrine tumours with a significant genetic component. Here, the authors carry out a multi-omic integrative characterization of PCC/PGL and reveal potential genomic alterations and regulatory mechanisms involved in the disease.

Research focused on succinate dehydrogenase (SDH) and its substrate, succinate, culminated in the 1950s accompanying the rapid development of research dedicated to bioenergetics and intermediary metabolism. This allowed researchers to uncover the implication of SDH in both the mitochondrial respiratory chain and the Krebs cycle. Nowadays, this theme is experiencing a real revival following the discovery of the role of SDH and succinate in a subset of tumors and cancers in humans. The aim of this review is to enlighten the many questions yet unanswered, ranging from fundamental to clinically oriented aspects, up to the danger of the current use of SDH as a target for a subclass of pesticides.

The Warburg effect describes how cancer cells down-regulate their aerobic respiration and preferentially use glycolysis to generate energy. To evaluate the link between hypoxia and Warburg effect, we studied mitochondrial electron transport, angiogenesis and glycolysis in pheochromocytomas induced by germ-line mutations in VHL, RET, NF1 and SDH genes. SDH and VHL gene mutations have been shown to lead to the activation of hypoxic response, even in normoxic conditions, a process now referred to as pseudohypoxia. We observed a decrease in electron transport protein expression and activity, associated with increased angiogenesis in SDH- and VHL-related, pseudohypoxic tumors, while stimulation of glycolysis was solely observed in VHL tumors. Moreover, microarray analyses revealed that expression of genes involved in these metabolic pathways is an efficient tool for classification of pheochromocytomas in accordance with the predisposition gene mutated. Our data suggest an unexpected association between pseudohypoxia and loss of p53, which leads to a distinct Warburg effect in VHL-related pheochromocytomas.

Despite the development of new therapeutic strategies, cancer remains one of the leading causes of mortality worldwide. One of the current major challenges is the resistance of cancers to chemotherapy treatments inducing metastases and relapse of the tumor. The Hedgehog receptor Patched (Ptch1) is overexpressed in many types of cancers. We showed that Ptch1 contributes to the efflux of doxorubicin and plays an important role in the resistance to chemotherapy in adrenocortical carcinoma (ACC), a rare cancer which presents strong resistance to the standard of care chemotherapy treatment. In the present study, we isolated and characterized a subpopulation of the ACC cell line H295R in which Ptch1 is overexpressed and more present at the cell surface. This cell subpopulation is more resistant to doxorubicin, grows as spheroids, and has a greater capability of clonogenicity, migration, and invasion than the parental cells. Xenograft experiments performed in mice and in ovo showed that this cell subpopulation is more tumorigenic and metastatic than the parental cells. These results suggest that this cell subpopulation has cancer stem-like or persistent cell properties which were strengthened by RNA-seq. If present in tumors from ACC patients, these cells could be responsible for therapy resistance, relapse, and metastases.