Spectrum and prevalence of FP/TMEM127 gene mutations in pheochromocytomas and paragangliomas

Succinate dehydrogenase mutations in head and neck paragangliomas: A systematic review and meta-analysis of individual patients' data

BACKGROUND

Head and neck paragangliomas (HNPs) have been associated with gene mutations in the succinate dehydrogenase (SDH) complex, but the clinical significance remains unclear. We sought to explore the demographics, clinical characteristics, treatment methods, and outcomes of SDH-mutated HNPs.

METHODS

Databases were systematically searched. Pooled event ratio and relative 95% confidence intervals were calculated for dichotomous outcomes. Meta-regression was performed. Cochran's Q test and I2 test assessed heterogeneity. Funnel plot and Egger's regression test assessed publication bias.

RESULTS

Forty-two studies with 8849 patients were included. Meta-regression revealed a significant correlation between multifocality and SDHD mutations (0.03 ± 0.006, p < 0.0001) and between distant metastases and SDHB mutations (0.06 ± 0.023, p = 0.008). There was no correlation between sex, age, tumor size, or familial occurrences and SDH-related mutations.

CONCLUSION

Multifocality of HNPs correlates with the SDHD mutational subtype, and metastases correlate with the SDHB subtype. Knowledge of HNP phenotypes associated with SDH-related mutations has the potential to influence the management approach to such HNPs.

Genetic and Molecular Biomarkers in Aggressive Pheochromocytomas and Paragangliomas

Pheochromocytomas and paragangliomas (PPGLs) are rare neoplasms producing catecholamines that occur as hereditary syndromes in 25-40% of cases. To date, PPGLs are no longer classified as benign and malignant tumors since any lesion could theoretically metastasize, even if it occurs only in a minority of cases (approximately 10-30%). Over the last decades, several attempts were made to develop a scoring system able to predict the risk of aggressive behavior at diagnosis, including the risk of metastases and disease recurrence; unfortunately, none of the available scores is able to accurately predict the risk of aggressive behavior, even including clinical, biochemical, and histopathological features. Thus, life-long follow-up is required in PPGL patients. Some recent studies focusing on genetic and molecular markers (involved in hypoxia regulation, gene transcription, cellular growth, differentiation, signaling pathways, and apoptosis) seem to indicate they are promising prognostic factors, even though their clinical significance needs to be further evaluated. The most involved pathways in PPGLs with aggressive behavior are represented by Krebs cycle alterations caused by succinate dehydrogenase subunits (SDHx), especially when caused by SDHB mutations, and by fumarate hydratase mutations that lead to the activation of hypoxia pathways and DNA hypermethylation, suggesting a common pathway in tumorigenesis. Conversely, PPGLs showing mutations in the kinase cascade (cluster 2) tend to display less aggressive behavior. Finally, establishing pathways of tumorigenesis is also fundamental to developing new drugs targeted to specific pathways and improving the survival of patients with metastatic disease. Unfortunately, the rarity of these tumors and the scarce number of cases enrolled in the available studies represents an obstacle to validating the role of molecular markers as reliable predictors of aggressiveness.

Patient Sex and Origin Influence Distribution of Driver Genes and Clinical Presentation of Paraganglioma

Context

Sexual and ancestral differences in driver gene prevalence have been described in many cancers but have not yet been investigated in pheochromocytoma and paraganglioma (PPGL).

Objective

This study aims to assess whether sex and ancestry influence prevalence of PPGL driver genes and clinical presentation.

Methods

We conducted a retrospective analysis of patients with PPGL considering studies from 2010 onwards that included minimal data of type of disease, sex, mutated gene, and country of origin. Additional features were recorded when available (age, tumor location, bilateral or multifocal, somatic or germline, and metastatic disease).

Results

We included 2162 patients: 877 in Europe and 757 in Asia. Males presented more often with germline pathogenic variants (PVs) in genes activating hypoxia pathways (P = .0006) and had more often sympathetic paragangliomas (P = .0005) and metastasis (P = .0039). On the other hand, females with PPGLs due to MAX PVs were diagnosed later than males (P = .0378) and more often developed metastasis (P = .0497). European but not Asian females presented more often with PPGLs due to PVs in genes related to kinase signaling (P = .0052), particularly RET and TMEM127. Contrary to experiences from Europe, Asian patients with PPGL due to PVs in kinase signaling genes NF1, HRAS, and FGFR1 showed a high proportion of sympathetic tumors, while European patients almost exclusively had adrenal tumors (P < .005).

Conclusion

Personalized management of patients with PPGL might benefit from considering sexual and ancestral differences. Further studies with better clinically aligned cohorts from various origins are required to better dissect ancestral influences on PPGL development.

Total adrenalectomy versus subtotal adrenalectomy for bilateral pheochromocytoma: meta-analysis

BACKGROUND

Bilateral pheochromocytomas are rare and often heritable. Total adrenalectomy leads to a definitive oncological cure, with subsequent definitive hypocortisolism. Subtotal adrenalectomy is a possible alternative. The aim of this study was to assess the effects of total adrenalectomy and subtotal adrenalectomy on bilateral pheochromocytoma in terms of post-surgical rate of recurrence, metastatic disease, and steroid dependence.

METHODS

Systematic searches in the bibliographic databases PubMed, Embase, and Europe PMC were performed for 1945 to 1 June 2023. PRISMA guidelines were followed and the PICO strategy was applied to English-language studies comparing subtotal adrenalectomy with total adrenalectomy. A random-effects model was used to assess the different outcomes for studies with high heterogeneity. The Newcastle-Ottawa scale and the Risk Of Bias In Non-randomized Studies of Interventions ('ROBINS-I') tool were used to assess quality and risk of bias.

RESULTS

From a total of 12 909 studies, 1202 patients (from 10 retrospective studies) were eligible for the meta-analysis. In six studies, including 1176 patients, the recurrence rate after subtotal adrenalectomy and total adrenalectomy was 14.1 versus 2.6 per cent respectively (OR 4.91, 95 per cent c.i. 1.30 to 18.54; P = 0.020; I2 72 per cent). In nine studies, including 1124 patients, the rate of post-surgical steroid dependence was 93.3 versus 11.6 per cent after total adrenalectomy and subtotal adrenalectomy respectively (OR 0.003, 95 per cent c.i. 0.0003 to 0.03; P < 0.00001; I2 66 per cent). Based on two studies, including 719 patients, no differences were evident regarding the occurrence of post-surgery metastatic disease.

CONCLUSION

Subtotal adrenalectomy leads to less post-surgical primary adrenal insufficiency, but leads to a higher postoperative recurrence rate. Future prospective randomized studies, with clear eligibility criteria, are needed to confirm these results.

Hashimoto's Thyroiditis and the Risk of Papillary Thyroid Cancer in Children

The association between Hashimoto's thyroiditis (HT) and pediatric thyroid cancer is controversial. Most studies examining this connection have been based on adults, and larger studies in children are lacking. We performed a retrospective study of all sequential pediatric patients who underwent a thyroidectomy for a neoplasm at our institution over a twenty-year period in order to explore the link between HT and pediatric thyroid cancer. A total of 153 patients, median age 16.5 (interquartile range [IQR] 14.2-18.3) years, underwent thyroid surgery for a neoplasm. Patients were mainly female (80%) and White (84%). Median follow-up was 58.6 (IQR 20.7-105.4) months. Thirty-five (23%) patients had HT. Patients who underwent thyroid surgery and had HT were more likely to harbor a malignant neoplasm (p = 0.05); specifically, papillary thyroid carcinoma (PTC, p = 0.02). There was a difference in the distribution of HT among the subtypes of PTC (p = 0.03). Despite this, there was no difference in terms of survival between patients with/without HT. In conclusion, children with a thyroid malignancy, specifically, PTC, are more likely to have HT. The association between HT and pediatric PTC appears to be subtype-specific but does not seem to affect patient survival.

The connection between tricarboxylic acid cycle enzyme mutations and pseudohypoxic signaling in pheochromocytoma and paraganglioma

Pheochromocytomas and paragangliomas (PPGLs) are rare neuroendocrine tumors originating from chromaffin cells, holding significant clinical importance due to their capacity for excessive catecholamine secretion and associated cardiovascular complications. Roughly 80% of cases are associated with genetic mutations. Based on the functionality of these mutated genes, PPGLs can be categorized into distinct molecular clusters: the pseudohypoxia signaling cluster (Cluster-1), the kinase signaling cluster (Cluster-2), and the WNT signaling cluster (Cluster-3). A pivotal factor in the pathogenesis of PPGLs is hypoxia-inducible factor-2α (HIF2α), which becomes upregulated even under normoxic conditions, activating downstream transcriptional processes associated with pseudohypoxia. This adaptation provides tumor cells with a growth advantage and enhances their ability to thrive in adverse microenvironments. Moreover, pseudohypoxia disrupts immune cell communication, leading to the development of an immunosuppressive tumor microenvironment. Within Cluster-1a, metabolic perturbations are particularly pronounced. Mutations in enzymes associated with the tricarboxylic acid (TCA) cycle, such as succinate dehydrogenase (SDHx), fumarate hydratase (FH), isocitrate dehydrogenase (IDH), and malate dehydrogenase type 2 (MDH2), result in the accumulation of critical oncogenic metabolic intermediates. Notable among these intermediates are succinate, fumarate, and 2-hydroxyglutarate (2-HG), which promote activation of the HIFs signaling pathway through various mechanisms, thus inducing pseudohypoxia and facilitating tumorigenesis. SDHx mutations are prevalent in PPGLs, disrupting mitochondrial function and causing succinate accumulation, which competitively inhibits α-ketoglutarate-dependent dioxygenases. Consequently, this leads to global hypermethylation, epigenetic changes, and activation of HIFs. In FH-deficient cells, fumarate accumulation leads to protein succination, impacting cell function. FH mutations also trigger metabolic reprogramming towards glycolysis and lactate synthesis. IDH1/2 mutations generate D-2HG, inhibiting α-ketoglutarate-dependent dioxygenases and stabilizing HIFs. Similarly, MDH2 mutations are associated with HIF stability and pseudohypoxic response. Understanding the intricate relationship between metabolic enzyme mutations in the TCA cycle and pseudohypoxic signaling is crucial for unraveling the pathogenesis of PPGLs and developing targeted therapies. This knowledge enhances our comprehension of the pivotal role of cellular metabolism in PPGLs and holds implications for potential therapeutic advancements.

TMEM127 suppresses tumor development by promoting RET ubiquitination, positioning, and degradation

The TMEM127 gene encodes a transmembrane protein of poorly known function that is mutated in pheochromocytomas, neural crest-derived tumors of adrenomedullary cells. Here, we report that, at single-nucleus resolution, TMEM127-mutant tumors share precursor cells and transcription regulatory elements with pheochromocytomas carrying mutations of the tyrosine kinase receptor RET. Additionally, TMEM127-mutant pheochromocytomas, human cells, and mouse knockout models of TMEM127 accumulate RET and increase its signaling. TMEM127 contributes to RET cellular positioning, trafficking, and lysosome-mediated degradation. Mechanistically, TMEM127 binds to RET and recruits the NEDD4 E3 ubiquitin ligase for RET ubiquitination and degradation via TMEM127 C-terminal PxxY motifs. Lastly, increased cell proliferation and tumor burden after TMEM127 loss can be reversed by selective RET inhibitors in vitro and in vivo. Our results define TMEM127 as a component of the ubiquitin system and identify aberrant RET stabilization as a likely mechanism through which TMEM127 loss-of-function mutations cause pheochromocytoma.

A cleaved METTL3 potentiates the METTL3-WTAP interaction and breast cancer progression

N6-methyladenosine (m6A) methylation of RNA by the methyltransferase complex (MTC), with core components including METTL3-METTL14 heterodimers and Wilms' tumor 1-associated protein (WTAP), contributes to breast tumorigenesis, but the underlying regulatory mechanisms remain elusive. Here, we identify a novel cleaved form METTL3a (residues 239-580 of METTL3). We find that METTL3a is required for the METTL3-WTAP interaction, RNA m6A deposition, as well as cancer cell proliferation. Mechanistically, we find that METTL3a is essential for the METTL3-METTL3 interaction, which is a prerequisite step for recruitment of WTAP in MTC. Analysis of m6A sequencing data shows that depletion of METTL3a globally disrupts m6A deposition, and METTL3a mediates mammalian target of rapamycin (mTOR) activation via m6A-mediated suppression of TMEM127 expression. Moreover, we find that METTL3 cleavage is mediated by proteasome in an mTOR-dependent manner, revealing positive regulatory feedback between METTL3a and mTOR signaling. Our findings reveal METTL3a as an important component of MTC, and suggest the METTL3a-mTOR axis as a potential therapeutic target for breast cancer.

[A case of cervical lymph node metastasis after carotid body tumor surgery]

Malignant carotid body tumor is rare, reported this case who had experienced the totally resection of carotid body tumor 16 years ago and presented with cervical tumor now. The patient was a 68 year old male who presented with a low growing left-sided painless neck mass for half a year. Carotid body tumor resection and left carotid artery artificial vascular reconstruction were performed 16 years ago. Physical examination showed that multiple hard and painless masses can be touched behind the left sternocleidomastoid muscle of the neck. Blood routine and biochemical tests were normal. MRI enhancement of the neck showed multiple circular abnormal signals behind the left sternocleidomastoid muscle, with obvious enhancement. The cervical masses of this case were experienced totally resected again, and the postoperative pathology confirmed that it was carotid body tumor and cervical lymph node metastasis. The clinical diagnosis was malignant carotid body tumor with cervical lymph node metastasis. Postoperative PET-CT examination showed multiple lymphadenopathy and abnormal metabolism in hilar, mediastinum and abdominal aorta. Multiple systemic metastasis of malignant carotid body tumor was considered. It was suggested that preoperative whole-body PET-CT examination can be used to evaluate whether the tumor has systemic metastasis.

Personalized Management of Pheochromocytoma and Paraganglioma

Pheochromocytomas/paragangliomas are characterized by a unique molecular landscape that allows their assignment to clusters based on underlying genetic alterations. With around 30% to 35% of Caucasian patients (a lower percentage in the Chinese population) showing germline mutations in susceptibility genes, pheochromocytomas/paragangliomas have the highest rate of heritability among all tumors. A further 35% to 40% of Caucasian patients (a higher percentage in the Chinese population) are affected by somatic driver mutations. Thus, around 70% of all patients with pheochromocytoma/paraganglioma can be assigned to 1 of 3 main molecular clusters with different phenotypes and clinical behavior. Krebs cycle/VHL/EPAS1-related cluster 1 tumors tend to a noradrenergic biochemical phenotype and require very close follow-up due to the risk of metastasis and recurrence. In contrast, kinase signaling-related cluster 2 tumors are characterized by an adrenergic phenotype and episodic symptoms, with generally a less aggressive course. The clinical correlates of patients with Wnt signaling-related cluster 3 tumors are currently poorly described, but aggressive behavior seems likely. In this review, we explore and explain why cluster-specific (personalized) management of pheochromocytoma/paraganglioma is essential to ascertain clinical behavior and prognosis, guide individual diagnostic procedures (biochemical interpretation, choice of the most sensitive imaging modalities), and provide personalized management and follow-up. Although cluster-specific therapy of inoperable/metastatic disease has not yet entered routine clinical practice, we suggest that informed personalized genetic-driven treatment should be implemented as a logical next step. This review amalgamates published guidelines and expert views within each cluster for a coherent individualized patient management plan.

Genetics of Pheochromocytomas and Paragangliomas Determine the Therapeutical Approach

Pheochromocytomas and paragangliomas are the most heritable endocrine tumors. In addition to the inherited mutation other driver mutations have also been identified in tumor tissues. All these genetic alterations are clustered in distinct groups which determine the pathomechanisms. Most of these tumors are benign and their surgical removal will resolve patient management. However, 5–15% of them are malignant and therapeutical possibilities for them are limited. This review provides a brief insight about the tumorigenesis associated with pheochromocytomas/paragangliomas in order to present them as potential therapeutical targets.

Genetic Alterations in Mitochondrial DNA Are Complementary to Nuclear DNA Mutations in Pheochromocytomas

Simple Summary

Mitochondrial DNA (mtDNA) alterations have been reported to play important roles in cancer development and metastasis. However, there is scarce information about pheochromocytomas and paragangliomas (PCCs/PGLs) formation. To determine the potential roles of mtDNA alterations in PCCs/PGLs, we analyzed a panel of 26 nuclear susceptibility genes and the entire mtDNA sequence of 77 human tumors, using NGS. We also performed an analysis of copy-number alterations, large mtDNA deletion, and gene/protein expression. Our results revealed that 53.2% of the tumors harbor a mutation in the susceptibility genes and 16.9% harbor complementary mitochondrial mutations. Large deletions and depletion of mtDNA were found in 26% and 87% of tumors, respectively, accompanied by a reduced expression of the mitochondrial biogenesis markers (PCG1α, NRF1, and TFAM). Furthermore, P62 and LC3a gene expression suggested increased mitophagy, which is linked to mitochondrial dysfunction. These finding suggest a complementarity and a potential contributing role in PCCs/PGLs tumorigenesis.

Abstract

Background: Somatic mutations, copy-number variations, and genome instability of mitochondrial DNA (mtDNA) have been reported in different types of cancers and are suggested to play important roles in cancer development and metastasis. However, there is scarce information about pheochromocytomas and paragangliomas (PCCs/PGLs) formation. Material: To determine the potential roles of mtDNA alterations in sporadic PCCs/PGLs, we analyzed a panel of 26 nuclear susceptibility genes and the entire mtDNA sequence of seventy-seven human tumors, using next-generation sequencing, and compared the results with normal adrenal medulla tissues. We also performed an analysis of copy-number alterations, large mtDNA deletion, and gene and protein expression. Results: Our results revealed that 53.2% of the tumors harbor a mutation in at least one of the targeted susceptibility genes, and 16.9% harbor complementary mitochondrial mutations. More than 50% of the mitochondrial mutations were novel and predicted pathogenic, affecting mitochondrial oxidative phosphorylation. Large deletions were found in 26% of tumors, and depletion of mtDNA occurred in more than 87% of PCCs/PGLs. The reduction of the mitochondrial number was accompanied by a reduced expression of the regulators that promote mitochondrial biogenesis (PCG1α, NRF1, and TFAM). Further, P62 and LC3a gene expression suggested increased mitophagy, which is linked to mitochondrial dysfunction. Conclusion: The pathogenic role of these finding remains to be shown, but we suggest a complementarity and a potential contributing role in PCCs/PGLs tumorigenesis.

Genomic Profiling of Lung Adenocarcinoma in Never-Smokers

PURPOSE

Approximately 10%-40% of patients with lung cancer report no history of tobacco smoking (never-smokers). We analyzed whole-exome and RNA-sequencing data of 160 tumor and normal lung adenocarcinoma (LUAD) samples from never-smokers to identify clinically actionable alterations and gain insight into the environmental and hereditary risk factors for LUAD among never-smokers.

METHODS

We performed whole-exome and RNA-sequencing of 88 and 69 never-smoker LUADs. We analyzed these data in conjunction with data from 76 never-smoker and 299 smoker LUAD samples sequenced by The Cancer Genome Atlas and Clinical Proteomic Tumor Analysis Consortium.

RESULTS

We observed a high prevalence of clinically actionable driver alterations in never-smoker LUADs compared with smoker LUADs (78%-92% v 49.5%; P < .0001). Although a subset of never-smoker samples demonstrated germline alterations in DNA repair genes, the frequency of samples showing germline variants in cancer predisposing genes was comparable between smokers and never-smokers (6.4% v 6.9%; P = .82). A subset of never-smoker samples (5.9%) showed mutation signatures that were suggestive of passive exposure to cigarette smoke. Finally, analysis of RNA-sequencing data showed distinct immune transcriptional subtypes of never-smoker LUADs that varied in their expression of clinically relevant immune checkpoint molecules and immune cell composition.

CONCLUSION

In this comprehensive genomic and transcriptome analysis of never-smoker LUADs, we observed a potential role for germline variants in DNA repair genes and passive exposure to cigarette smoke in the pathogenesis of a subset of never-smoker LUADs. Our findings also show that clinically actionable driver alterations are highly prevalent in never-smoker LUADs, highlighting the need for obtaining biopsies with adequate cellularity for clinical genomic testing in these patients.

[Clinical and laboratory features of hereditary pheochromocytoma and paraganglioma]

The widespread introduction of genetic testing in recent years has made it possible to determine that more than a third of cases of pheochromocytomas and paragangliomas (PPPGs) are caused by germline mutations. Despite the variety of catecholamine-producing tumors manifestations, there is a sufficient number of clinical and laboratory landmarks that suggest a hereditary genesis of the disease and even a specific syndrome. These include a family history, age of patient, presence of concomitant conditions, and symptoms of the disease. Considering that each of the mutations is associated with certain diseases that often determine tactics of treatment and examination of a patient, e.g. high risk of various malignancies. Awareness of the practitioner on the peculiarities of the course of family forms of PPPGs will allow improving the tactics of managing these patients.The article provides up-to-date information on the prevalence of hereditary PPPGs. The modern views on the pathogenesis of the disease induced by different mutations are presented. The main hereditary syndromes associated with PPPGs are described, including multiple endocrine neoplasia syndrome type 2A and 2B, type 1 neurofibromatosis, von Hippel-Lindau syndrome, hereditary paraganglioma syndrome, as well as clinical and laboratory features of the tumor in these conditions. The main positions on the necessity of genetic screening in patients with PPPGs are given.

Metastatic cluster 2-related pheochromocytoma/paraganglioma: a single-center experience and systematic review

Risk of metastatic disease in the cluster 2-related pheochromocytoma/paraganglioma (PPGL) is low. In MEN2 patients, identification of origin of metastases from pheochromocytoma (PCC) or medullary thyroid carcinoma (MTC) is challenging as both are of neuroendocrine origin. We aim to describe our experience and perform a systematic review to assess prevalence, demographics, biochemistry, diagnostic evaluation, management, and predictors of cluster 2-related metastatic PPGL. Retrospective analysis of 3 cases from our cohort and 43 cases from world literature was done. For calculation of prevalence, all reported patients (n = 3063) of cluster 2 were included. We found that the risk of metastasis in cluster 2-related PPGL was 2.6% (2% in RET, 5% in NF1, 4.8% in TMEM127 and 16.7% in MAX variation). In metastatic PCC in MEN2, median age was 39 years, bilateral tumors were present in 71% and median tumor size was 9.7 cm (range 4-19) with 43.5% mortality. All patients had a primary tumor size ≥4 cm. Origin of primary tumor was diagnosed by histopathology of metastatic lesion in 11 (57.9%), 131I-MIBG scan in 6 (31.6%), and selective venous sampling and CT in 1 (5.3%) patient each. In subgroup of neurofibromatosis 1 (NF1), median age was 46 years (range 14-59) with median tumor size 6 cm and 57% mortality. To conclude, the risk of metastatic disease in cluster 2-related PPGL is low, being especially high in tumors with size ≥4 cm and associated with high mortality. One-third patients of NF1 with metastatic PPGL had presented in second decade of life. Long-term studies are needed to formulate management recommendations.

Insights into Mechanisms of Pheochromocytomas and Paragangliomas Driven by Known or New Genetic Drivers

Simple Summary

Pheochromocytomas and paragangliomas are rare neuroendocrine tumors that are often hereditary. Although research has advanced considerably, significant gaps still persist in understanding risk factors, predicting metastatic potential and treating aggressive tumors. The study of rare mutations can provide new insights into how pheochromocytomas and paragangliomas develop. In this review, we provide examples of such rare events and how they can inform our understanding of the spectrum of mutations that can lead to these tumors and improve our ability to provide a genetic diagnosis.

Abstract

Pheochromocytomas and paragangliomas are rare tumors of neural crest origin. Their remarkable genetic diversity and high heritability have enabled discoveries of bona fide cancer driver genes with an impact on diagnosis and clinical management and have consistently shed light on new paradigms in cancer. In this review, we explore unique mechanisms of pheochromocytoma and paraganglioma initiation and management by drawing from recent examples involving rare mutations of hypoxia-related genes VHL, EPAS1 and SDHB, and of a poorly known susceptibility gene, TMEM127. These models expand our ability to predict variant pathogenicity, inform new functional domains, recognize environmental-gene connections, and highlight persistent therapeutic challenges for tumors with aggressive behavior.

Pheochromocytoma: A Clinicopathologic and Molecular Study of 390 Cases From a Single Center

Pheochromocytomas are rare neuroendocrine tumors arising from chromaffin cells in the adrenal medulla. They may occur sporadically or in the context of hereditary syndromes. All pheochromocytomas are considered to have malignant potential (defined as risk of metastasis, not local invasion). The use of grading systems with incorporated clinical and histopathologic parameters can help but not definitively predict the metastatic potential of pheochromocytomas. The recent discovery of susceptibility genes provided new insights into the pathogenesis and introduced additional approaches to estimate the metastatic risk of pheochromocytoma. However, the prevalence of these genetic signatures in pheochromocytomas has yet to be fully addressed. Therefore, in the present study, we retrospectively reviewed cases of pheochromocytoma from 1980 to 2018 in the archives of our institution. Three hundred ninety cases were identified, and their clinicopathologic characteristics and genetic statuses were analyzed. About 25% of the cases had metastases, which were more common in older patients (median, 49 y) than in younger ones. Univariate and multivariate analyses revealed that older age, Hispanic ethnicity, metastasis, and large primary tumor size were markedly associated with poor overall survival. In contrast, family history of pheochromocytoma, lack of symptoms, and bilateral adrenal involvement were associated with better survival. About 37% of the pheochromocytomas were associated with inherited syndromes. About 52% of tested patients had pathogenic mutations of pheochromocytoma susceptibility genes. Of these, succinate dehydrogenase B gene mutation had the strongest association with metastasis. These data support that genetic testing should be offered to all patients with pheochromocytoma.

Analytical Performance of NGS-Based Molecular Genetic Tests Used in the Diagnostic Workflow of Pheochromocytoma/Paraganglioma

Next Generation Sequencing (NGS)-based methods are high-throughput and cost-effective molecular genetic diagnostic tools. Targeted gene panel and whole exome sequencing (WES) are applied in clinical practice for assessing mutations of pheochromocytoma/paraganglioma (PPGL) associated genes, but the best strategy is debated. Germline mutations of at the least 18 PPGL genes are present in approximately 20-40% of patients, thus molecular genetic testing is recommended in all cases. We aimed to evaluate the analytical and clinical performances of NGS methods for mutation detection of PPGL-associated genes. WES (three different library preparation and bioinformatics workflows) and an in-house, hybridization based gene panel (endocrine-onco-gene-panel- ENDOGENE) was evaluated on 37 (20 WES and 17 ENDOGENE) samples with known variants. After optimization of the bioinformatic workflow, 61 additional samples were tested prospectively. All clinically relevant variants were validated with Sanger sequencing. Target capture of PPGL genes differed markedly between WES platforms and genes tested. All known variants were correctly identified by all methods, but methods of library preparations, sequencing platforms and bioinformatical settings significantly affected the diagnostic accuracy. The ENDOGENE panel identified several pathogenic mutations and unusual genotype-phenotype associations suggesting that the whole panel should be used for identification of genetic susceptibility of PPGL.

A Critical Appraisal of Contemporary and Novel Biomarkers in Pheochromocytomas and Adrenocortical Tumors

Simple Summary

Pheochromocytomas/paragangliomas (PPGLs) and adrenocortical tumors are neoplasms that originate from different regions of the adrenal gland and display significant heterogeneity with respect to their biological and clinical behavior. They may be sporadic or develop in the context of hereditary syndromes. Adrenocortical tumors are mostly benign but less than 2% are carcinomas associated with a poor outcome when diagnosed in advanced disease. The majority of PPGLS are benign, but a subset may develop metastatic disease. In particular, for PPGLs, it is mandatory to identify biomarkers of high sensitivity and specificity that lead to accurate diagnosis and predict patients with a malignant potential that would benefit from aggressive surveillance and administration of early treatment. Current biomarkers include mostly histopathological and genetic parameters but none of them can be considered independent predictive factors. Recent genomic studies have implemented new molecular biomarkers of high accuracy for the diagnosis and management of PPGLs and adrenocortical tumors. In this review, we summarize the current and novel biomarkers that may be considered valuable tools for diagnosis and prediction of malignancy in patients with PPGLs and adrenocortical tumors.

Abstract

Pheochromocytomas/Paragangliomas (PPGLs) and adrenocortical tumors are rare neoplasms with significant heterogeneity in their biologic and clinical behavior. Current diagnostic and predictive biomarkers include hormone secretion, as well as histopathological and genetic features. PPGL diagnosis is based on biochemical measurement of catecholamines/metanephrines, while histopathological scoring systems have been proposed to predict the risk of malignancy. Adrenocortical tumors are mostly benign, but some can be malignant. Currently, the stage of disease at diagnosis and tumor grade, appear to be the most powerful prognostic factors. However, recent genomic and proteomic studies have identified new genetic and circulating biomarkers, including genes, immunohistochemical markers and micro-RNAs that display high specificity and sensitivity as diagnostic or prognostic tools. In addition, new molecular classifications have been proposed that divide adrenal tumors in distinct subgroups with different clinical outcomes.

Multigene Panel Testing in Individuals With Hepatocellular Carcinoma Identifies Pathogenic Germline Variants

Hepatocellular carcinoma (HCC) has well-defined environmental risk factors. In addition, epidemiologic studies have suggested hereditary risk factors. The goals of this study were to determine the rate of pathogenic and likely pathogenic (P/LP) germline variants in cancer predisposition genes in patients with HCC, possible enrichment of P/LP variants in particular genes, and potential impact on clinical management.

MATERIALS AND METHODS

A prospective study at a tertiary medical center enrolled 217 patients with a personal history of HCC. Multigene panel testing was performed for 134 cancer predisposition genes in all patients. The rate of P/LP variants was compared with population rates. A separate retrospective cohort included 219 patients with HCC who underwent testing at a commercial laboratory.

RESULTS

In the prospective cohort, P/LP germline variants were identified in 25 of 217 patients with HCC (11.5%). Four patients (1.8%) had P/LP variants in the highly penetrant cancer genes BRCA2 (n = 2), MSH6 (n = 1), and PMS2 (n = 1). In addition, multiple patients had P/LP variants in FANCA (n = 5) and BRIP1 (n = 4), which were significantly enriched in HCC compared with the general population. Detection of P/LP variants led to changes in clinical management in regard to therapy selection, screening recommendations, and cascade testing of relatives. In a separate retrospective analysis of 219 patients with HCC, 30 (13.7%) were positive for P/LP variants including 13 (5.9%) with highly penetrant genes APC (n = 2), BRCA1 (n = 1), BRCA2 (n = 6), MSH2 (n = 2), or TP53 (n = 2).

CONCLUSION

P/LP germline variants in cancer predisposition genes were detected in 11%-14% of patients with HCC. Inherited genetics should not be overlooked in HCC as there are important implications for precision treatment, future risk of cancers, and familial cancer risk.

Genetics of pheochromocytoma and paraganglioma

PURPOSE OF REVIEW

This review summarizes our current understanding of germline and somatic genetics and genomics of pheochromocytomas and paragangliomas (PCC/PGL), describes existing knowledge gaps, and discusses future research directions.

RECENT FINDINGS

Germline pathogenic variants (PVs) are found in up to 40% of those with PCC/PGL. Tumors with germline PVs are broadly categorized as Cluster 1 (pseudohypoxia), including those with SDH, VHL, FH, and EPAS1 PVs, or Cluster 2 (kinase signaling) including those with NF1, RET, TMEM127, and MAX PVs. Somatic driver mutations exist in some of the same genes (RET, VHL, NF1, EPAS1) as well as in additional genes including HRAS, CSDE1 and genes involved in cell immortalization (ATRX and TERT). Other somatic driver events include recurrent fusion genes involving MAML3.

SUMMARY

PCC/PGL have the highest association with germline PVs of all human solid tumors. Expanding our understanding of the molecular pathogenesis of PCC/PGL is essential to advancements in diagnosis and surveillance and the development of novel therapies for these unique tumors.

Concurrent heterozygous Von-Hippel-Lindau and transmembrane-protein-127 gene mutation causing an erythropoietin-secreting pheochromocytoma in a normotensive patient with severe erythrocytosis

BACKGROUND

Mutations of genes related to Krebs cycle enzymes, kinases or to pseudohypoxic signaling pathways, including Von-Hippel-Lindau (VHL) and transmembrane-protein-127 predispose to pheochromocytoma and paraganglioma development. Homozygous loss of function mutation of VHL (VHL 598C>T) gene can associate with polycythemia because of an altered hypoxia sensing.

PATIENT

A 19-year-old normotensive man presented with headache, fatigue associated with severe erythrocytosis (hematocrit 76%), high hemoglobin (25.3 g/dl) in normoxic condition. Bone marrow biopsy showed marked hyperplasia of erythroid series. The Janus kinase 2 (V617F) mutation was absent. Abdominal computed tomography scan showed a 8-mm left adrenal pheochromocytoma with tracer uptake on GaDOTA-octreotate PET. Twenty-four-hour urinary metanephrine excretion was slightly increased, while normetanephrine, 3-methoxytyramine were normal. Adrenal veins sampling showed high left-side erythropoietin secretion.

RESULTS

Next-generation sequencing genetic analysis evidenced two concurrent heterozygous mutation of VHL598C>T and of transmembrane-protein-127 c.268G>A. Left side adrenalectomy improved symptoms, erythrocytosis, hemoglobin, and erythropoietin circulating levels. Adrenal histologic sections showed a pheochromocytoma with extensive immunostaining for erythropoietin, but also coexpression of chromogranin A, a marker of chromaffin tissue.

CONCLUSION

Congenital polycythemia was clinically diagnosed, mimicking Chuvash polycythemia. Chuvash polycythemia is an autosomal recessive disorder that usually harbors a homozygous mutation of VHL598C>T but not predispose to pheochromocytoma development; in contrast our patient showed for the first time that the concurrent heterozygous VHL and TMEM mutations, resulted in a clinical phenotype of a normotensive patient with polycythemia due to erythropoietin-secreting pheochromocytoma that improved after adrenalectomy.

Genotype-Phenotype Features of Germline Variants of the TMEM127 Pheochromocytoma Susceptibility Gene: A 10-Year Update

PURPOSE

This work aimed to evaluate genotype-phenotype associations in individuals carrying germline variants of transmembrane protein 127 gene (TMEM127), a poorly known gene that confers susceptibility to pheochromocytoma (PHEO) and paraganglioma (PGL).

DESIGN

Data were collected from a registry of probands with TMEM127 variants, published reports, and public databases.

MAIN OUTCOME ANALYSIS

Clinical, genetic, and functional associations were determined.

RESULTS

The cohort comprised 110 index patients (111 variants) with a mean age of 45 years (range, 21-84 years). Females were predominant (76 vs 34, P < .001). Most patients had PHEO (n = 94; 85.5%), although PGL (n = 10; 9%) and renal cell carcinoma (RCC, n = 6; 5.4%) were also detected, either alone or in combination with PHEO. One-third of the cases had multiple tumors, and known family history was reported in 15.4%. Metastatic PHEO/PGL was rare (2.8%). Epinephrine alone, or combined with norepinephrine, accounted for 82% of the catecholamine profiles of PHEO/PGLs. Most variants (n = 63) occurred only once and 13 were recurrent (2-12 times). Although nontruncating variants were less frequent than truncating changes overall, they were predominant in non-PHEO clinical presentations (36% PHEO-only vs 69% other, P < .001) and clustered disproportionately within transmembrane regions (P < .01), underscoring the relevance of these domains for TMEM127 function. Integration of clinical and previous experimental data supported classification of variants into 4 groups based on mutation type, localization, and predicted disruption.

CONCLUSIONS

Patients with TMEM127 variants often resemble sporadic nonmetastatic PHEOs. PGL and RCC may also co-occur, although their causal link requires further evaluation. We propose a new classification to predict variant pathogenicity and assist with carrier surveillance.

Identification of a TMEM127 variant in a patient with paraganglioma and acromegaly

SUMMARY

The coincidence of a pheochromocytoma or paraganglioma and a pituitary adenoma in the same patient is a rare condition. In the last few years SDHx and MAX mutations have been identified and discussed as a potential causal connection in cases of coincidence. We describe a case of a middle-aged female patient which presented with acromegaly, a growth hormone-secreting pituitary adenoma and a symptomatic neck paraganglioma. The patient was cured by surgery from both the pituitary tumour and the paraganglioma and is well after ten years follow-up. Due to the unusual coexistence of two neuroendocrine tumours, further molecular genetic testing was performed which revealed a variant in the TMEM127 gene (c245-10C>G).

LEARNING POINTS

Pheochromocytoma/paraganglioma and coexisting functioning pituitary adenoma are a very rare condition. An appropriate treatment of each tumour entity with a multi-disciplinary approach and regular follow-up is needed. The possibility of a hereditary disease should be considered and genetic workup is recommended. Genetic testing should focus primarily on the genes with mutations related to pheochromocytomas and paragangliomas. Next-generation sequencing with multi-gene panel testing is the currently suggested strategy. Genes associated with paragangliomas and pituitary adenomas are SDHA, SDHB, SDHC, SDHD, SDHAF2, MAX and MEN1, while case reports with VHL, RET and NF1 may represent coincidences. Variants of uncertain significance may need ongoing vigilance, in case novel data become available of these variants.

Texture analysis of routine T2 weighted fat-saturated images can identify head and neck paragangliomas - A pilot study

PURPOSE

To evaluate the role of the first and second-order texture parameters obtained from T2-weighted fat-saturated DIXON images in differentiating paragangliomas from other neck masses, and to develop a statistical model to classify them.

METHOD

We retrospectively evaluated 38 paragangliomas, 18 nerve-sheath tumours and 14 other miscellaneous neck lesions obtained from an IRB approved study conducted between January 2016 and June 2019; using a composite gold standard of histopathology, cytology and DOTANOC PET CT (A total of 70 lesions in 63 patients). Fat-suppressed T2weighted-DIXON axial images were used. First and second-order texture-parameters were calculated from the original and filtered images. Feature selection using F-statistics and collinearity analysis provided 14 texture parameters for further analysis. Mann-Whitney-U test was used to compare between the groups and p-values were adjusted for multiple comparisons. ROC curve analysis was used to obtain optimal cut-offs.

RESULTS

A total of ten texture features were found to be significantly different between paragangliomas and non-paraganglioma lesions. Minimum from the histogram of grey levels was lower in paragangliomas with a cut off of ≤113.462 obtaining 62.9 % sensitivity and 77.27 % specificity in differentiating paragangliomas from non-paragangliomas. Logistic regression model was trained (n-49) using forward feature selection, which when evaluated on the validation set(n-21)- obtained an AUC of 0.855(95 %CI, 0.633 to 0.968) with a positive likelihood ratio of 4.545 (95 %CI, 1.298-15.923) in differentiating paragangliomas from non-paragangliomas.

CONCLUSION

Texture analysis of a routine imaging sequence can identify paragangliomas with high accuracy. Further development of texture analysis would enable better imaging workflow, resource utilisation and imaging cost reductions.

Functional Characterization of TMEM127 Variants Reveals Novel Insights into Its Membrane Topology and Trafficking

CONTEXT

TMEM127 is a poorly known tumor suppressor gene associated with pheochromocytomas, paragangliomas, and renal carcinomas. Our incomplete understanding of TMEM127 function has limited our ability to predict variant pathogenicity.

PURPOSE

To better understand the function of the transmembrane protein TMEM127 we undertook cellular and molecular evaluation of patient-derived germline variants.

DESIGN

Subcellular localization and steady-state levels of tumor-associated, transiently expressed TMEM127 variants were compared to the wild-type protein using immunofluorescence and immunoblot analysis, respectively, in cells genetically modified to lack endogenous TMEM127. Membrane topology and endocytic mechanisms were also assessed.

RESULTS

We identified 3 subgroups of mutations and determined that 71% of the variants studied are pathogenic or likely pathogenic through loss of membrane-binding ability, stability, and/or internalization capability. Investigation into an N-terminal cluster of missense variants uncovered a previously unrecognized transmembrane domain, indicating that TMEM127 is a 4- transmembrane, not a 3-transmembrane domain-containing protein. Additionally, a C-terminal variant with predominant plasma membrane localization revealed an atypical, extended acidic, dileucine-based motif required for TMEM127 internalization through clathrin-mediated endocytosis.

CONCLUSION

We characterized the functional deficits of several germline TMEM127 variants and identified novel structure-function features of TMEM127. These findings will assist in determining pathogenicity of TMEM127 variants and will help guide future studies investigating the cellular role of TMEM127.

Pheochromocytoma Due to TMEM127 Mutation - The Importance of Genetic Testing for Clinical Decision

Apreviously healthy 53-year-old woman presented with new onset arterial hypertension diagnosed during workup for daily pulsatile bilateral frontal headaches and paroxysmal episodes of fatigue, palpitations and sweating. High urinary metanephrines were detected and an abdominal magnetic resonance image evidenced two nodular bilateral adrenal lesions and a left iliac focal lesion. ¹⁸F-FDG-PET/CT (fluorodeoxyglucose-positron emission tomography/computed tomography) scanning revealed mild-to-moderate uptake in both adrenal lesions and mild uptake in the iliac bone, whereas ¹²³I-metaiodobenzylguanide scintigraphy revealed uptake only in the right adrenal. CT-scan confirmed the heterogeneous nodular lesion on the right adrenal gland as suspicious for pheochromocytoma and a non-specific sclerotic lesion in the iliac. A right adrenalectomy was performed with posterior resolution of symptoms and normalisation of urinary metanephrines. Histology confirmed a pheochromocytoma and later a mutation of the TMEM127 gene was detected. The present case highlights the importance of genetic testing for pheochromocytoma in order to better guide the management of these patients.

An overview of 20 years of genetic studies in pheochromocytoma and paraganglioma

Paragangliomas and pheochromocytomas (PPGL) are rare neuroendocrine tumours characterized by a strong genetic determinism. Over the past 20 years, evolution of PPGL genetics has revealed that around 40% of PPGL are genetically determined, secondary to a germline mutation in one of more than twenty susceptibility genes reported so far. More than half of the mutations occur in one of the SDHx genes (SDHA, SDHB, SDHC, SDHD, SDHAF2), which encode the different subunits and assembly protein of a mitochondrial enzyme, succinate dehydrogenase. These susceptibility genes predispose to early forms (VHL, RET, SDHD, EPAS1, DLST), syndromic (RET, VHL, EPAS1, NF1, FH), multiple (SDHD, TMEM127, MAX, DLST, MDH2, GOT2) or malignant (SDHB, FH, SLC25A11) PPGL. The discovery of a germline mutation in one of these genes changes the patient's follow-up and allows genetic screening of affected families and the presymptomatic follow-up of relatives carrying a mutation.

Epigenetic Deregulation of Protocadherin PCDHGC3 in Pheochromocytomas/Paragangliomas Associated With SDHB Mutations

CONTEXT

SDHB mutations are found in an increasing number of neoplasms, most notably in paragangliomas and pheochromocytomas (PPGLs). SDHB-PPGLs are slow-growing tumors, but ∼50% of them may develop metastasis. The molecular basis of metastasis in these tumors is a long-standing and unresolved problem. Thus, a better understanding of the biology of metastasis is needed.

OBJECTIVE

This study aimed to identify gene methylation changes relevant for metastatic SDHB-PPGLs.

DESIGN

We performed genome-wide profiling of DNA methylation in diverse clinical and genetic PPGL subtypes, and validated protocadherin γ-C3 (PCDHGC3) gene promoter methylation in metastatic SDHB-PPGLs.

RESULTS

We define an epigenetic landscape specific for metastatic SDHB-PPGLs. DNA methylation levels were found significantly higher in metastatic SDHB-PPGLs than in SDHB-PPGLs without metastases. One such change included long-range de novo methylation of the PCDHA, PCDHB, and PCDHG gene clusters. High levels of PCDHGC3 promoter methylation were validated in primary metastatic SDHB-PPGLs, it was found amplified in the corresponding metastases, and it was significantly correlated with PCDHGC3 reduced expression. Interestingly, this epigenetic alteration could be detected in primary tumors that developed metastasis several years later. We also show that PCDHGC3 down regulation engages metastasis-initiating capabilities by promoting cell proliferation, migration, and invasion.

CONCLUSIONS

Our data provide a map of the DNA methylome episignature specific to an SDHB-mutated cancer and establish PCDHGC3 as a putative suppressor gene and a potential biomarker to identify patients with SDHB-mutated cancer at high risk of metastasis who might benefit from future targeted therapies.

Novel TMEM127 Variant Associated to Bilateral Phaeochromocytoma with an Uncommon Clinical Presentation

Phaeochromocytomas and paragangliomas are rare catecholamine-secreting tumours arising from the adrenal medulla or sympathetic paraganglia. It is known that 20–30% of all cases occur as a result of germline variants in several well known genes. The TMEM127 gene was recently identified as a new phaeochromocytoma susceptibility gene. However, until a larger sample of cases is available, the prevalence, genotype-phenotype correlation, and a clear predominant biochemical pattern of TMEM127-related PCC, remain to be defined. We present a woman with the pathogenic variant c.86delG (p.Arg29Leufs^∗52) in the TMEM127 gene, which has not been previously reported, associated to a bilateral phaeochromocytoma, with an uncommon initial clinical presentation and a biochemical profile that is distinctly adrenergic. Her two young children carry the same variant and are, at present, disease-free. Physicians should be aware that phaeochromocytoma can manifest in an atypical manner, as with episodic hypotension, mainly if the symptoms have no obvious aetiology and they worsen over time. This case also supports the presence of a predominant adrenaline secreting pattern in TMEM127-positive tumours, as well as the need to consider multigene panel testing in patients with bilateral phaeochromocytomas.

The tumor suppressor TMEM127 regulates insulin sensitivity in a tissue-specific manner

Understanding the molecular components of insulin signaling is relevant to effectively manage insulin resistance. We investigated the phenotype of the TMEM127 tumor suppressor gene deficiency in vivo. Whole-body Tmem127 knockout mice have decreased adiposity and maintain insulin sensitivity, low hepatic fat deposition and peripheral glucose clearance after a high-fat diet. Liver-specific and adipose-specific Tmem127 deletion partially overlap global Tmem127 loss: liver Tmem127 promotes hepatic gluconeogenesis and inhibits peripheral glucose uptake, while adipose Tmem127 downregulates adipogenesis and hepatic glucose production. mTORC2 is activated in TMEM127-deficient hepatocytes suggesting that it interacts with TMEM127 to control insulin sensitivity. Murine hepatic Tmem127 expression is increased in insulin-resistant states and is reversed by diet or the insulin sensitizer pioglitazone. Importantly, human liver TMEM127 expression correlates with steatohepatitis and insulin resistance. Our results suggest that besides tumor suppression activities, TMEM127 is a nutrient-sensing component of glucose/lipid homeostasis and may be a target in insulin resistance.

Surgical approaches and results of treatment for hereditary paragangliomas

Paragangliomas (PGL) are rare neuroendocrine tumours; parasympathetic PGL are predominantly non-secreting and located at the skull base and neck, while sympathetic PGL are typically catecholamine-secreting and located at abdomino-pelvic level. Approximately 40% of PGL may be caused by germline mutations; hereditary variants should be suspected especially in case of positive family history, early onset, multifocal, or recurrent PGL. Significant genotype-phenotype correlation has been recognized, including syndromic presentation, location, multifocality and risk of malignancy. Surgical resection remains the only curative strategy, but the outcomes may be unsatisfactory because of surgical morbidity and recurrence rate. However, due to the rarity of the disease, most data derive from case-report or limited series. This paper was aimed to review the available literature on the epidemiology, diagnosis, clinical features, treatment of PGL in order to discuss the surgical approach and the results of treatment in hereditary PGL.

Pheochromocytoma/Paraganglioma: Is This a Genetic Disorder?

Pheochromocytomas and paragangliomas (PCC/PGL) are neuroendocrine tumors of the adrenal medulla and extra-adrenal ganglia which often over-secrete catecholamines leading to cardiovascular morbidity and even mortality. These unique tumors have the highest heritability of all solid tumor types with up to 35-40% of patients with PCC/PGL having a germline predisposition. PURPOSE OF REVIEW: To review the germline susceptibility genes and clinical syndromes associated with PCC/PGL. RECENT FINDINGS: There are over 12 PCC/PGL susceptibility genes identified in a wide range of pathways. Each gene is associated with a clinical syndrome with varying penetrance for both primary and metastatic PCC/PGL and often includes increased risk for additional tumors besides PCC/PGL. Patients with sporadic or hereditary PCC/PGL should be monitored for life given the risk of multiple primary tumors, recurrence, and metastatic disease. All patients with PCC/PGL should be referred for consideration for clinical genetic testing given the high heritability of disease.

Pheochromocytomas and Paragangliomas: New Developments with Regard to Classification, Genetics, and Cell of Origin

Pheochromocytomas (PCC) and paragangliomas (PGL) are rare neuroendocrine tumors that arise in the adrenal medulla and in extra-adrenal locations, such as the head, neck, thorax, abdomen, and pelvis. Classification of these tumors into those with or without metastatic potential on the basis of gross or microscopic features is challenging. Recent insights and scoring systems have attempted to develop solutions for this, as described in the latest World Health Organization (WHO) edition on endocrine tumor pathology. PCC and PGL are amongst the tumors most frequently accompanied by germline mutations. More than 20 genes are responsible for a hereditary background in up to 40% of these tumors; somatic mutations in the same and several additional genes form the basis for another 30%. However, this does not allow for a complete understanding of the pathogenesis or targeted treatment of PCC and PGL, for which surgery is the primary treatment and for which metastasis is associated with poor outcome. This review describes recent insights into the cell of origin of these tumors, the latest developments with regard to the genetic background, and the current status of tumor classification including proposed scoring systems.

Precision Surgery for Pheochromocytomas and Paragangliomas

Since Felix Fränkel's account of pheochromocytoma in 1886, great discoveries and vast advancements in the diagnosis, genetics, anatomical and functional imaging techniques, and surgical management of pheochromcytoma and paraganglioma (P-PGL) have been made. The improved insight in the pathophysiology of P-PGL and more accurate detection methods enable physicians to tailor the treatment plan to an individual based on the genetic profile and tumor behavior. This review will cover briefly the clinical features, diagnosis, genetic mutations, and imaging modalities that are used to guide current surgical management of these rare and interesting endocrinopathies.

An Update on the Histology of Pheochromocytomas: How Does it Relate to Genetics?

Pheochromocytomas are rare neuroendocrine tumors of the adrenal gland, whereas any extra-adrenal tumor with similar histology is designated as paraganglioma. These tumors have a very high rate of germline mutations in a large number of genes, up to 35% to 40%, frequently predisposing for other tumors as well. Therefore, they represent a phenomenal challenge for treating physicians. This review focuses on pheochromocytomas only, with special attention to gross and microscopic clues to the diagnosis of genetic syndromes, including the role of succinate dehydrogenase subunit A and subunit B immunohistochemistry as surrogate markers for genetic analysis in the field of succinate dehydrogenase subunit gene mutations.

65 YEARS OF THE DOUBLE HELIX: Genetics informs precision practice in the diagnosis and management of pheochromocytoma

Although the authors of the present review have contributed to genetic discoveries in the field of pheochromocytoma research, we can legitimately ask whether these advances have led to improvements in the diagnosis and management of patients with pheochromocytoma. The answer to this question is an emphatic Yes! In the field of molecular genetics, the well-established axiom that familial (genetic) pheochromocytoma represents 10% of all cases has been overturned, with >35% of cases now attributable to germline disease-causing mutations. Furthermore, genetic pheochromocytoma can now be grouped into five different clinical presentation types in the context of the ten known susceptibility genes for pheochromocytoma-associated syndromes. We now have the tools to diagnose patients with genetic pheochromocytoma, identify germline mutation carriers and to offer gene-informed medical management including enhanced surveillance and prevention. Clinically, we now treat an entire family of tumors of the paraganglia, with the exact phenotype varying by specific gene. In terms of detection and classification, simultaneous advances in biochemical detection and imaging localization have taken place, and the histopathology of the paraganglioma tumor family has been revised by immunohistochemical-genetic classification by gene-specific antibody immunohistochemistry. Treatment options have also been substantially enriched by the application of minimally invasive and adrenal-sparing surgery. Finally and most importantly, it is now widely recognized that patients with genetic pheochromocytoma/paraganglioma syndromes should be treated in specialized centers dedicated to the diagnosis, treatment and surveillance of this rare neoplasm.

The TMEM127 human tumor suppressor is a component of the mTORC1 lysosomal nutrient-sensing complex

The TMEM127 tumor suppressor gene encodes a transmembrane protein of unknown function mutated in pheochromocytomas and, rarely, in renal cancers. Tumors with inactivating TMEM127 mutations have increased mTORC1 signaling by undefined mechanisms. Here we report that TMEM127 interacts with the lysosome-anchored complex comprised of Rag GTPases, the LAMTOR pentamer (or 'ragulator') and vATPase, which controls amino acid-mediated mTORC1 activation. We found that under nutrient-rich conditions TMEM127 expression reduces mTORC1 recruitment to Rags. In addition, TMEM127 interacts with LAMTOR in an amino acid-dependent manner and decreases the LAMTOR1-vATPase association, while TMEM127-vATPase binding requires intact lysosomal acidification but is amino acid independent. Conversely, both murine and human cells lacking TMEM127 accumulate LAMTOR proteins in the lysosome. Consistent with these findings, pheochromocytomas with TMEM127 mutations have increased levels of LAMTOR proteins. These results suggest that TMEM127 interactions with ragulator and vATPase at the lysosome contribute to restrain mTORC1 signaling in response to amino acids, thus explaining the increased mTORC1 activation seen in TMEM127-deficient tumors.

Homozygous TMEM127 mutations in 2 patients with bilateral pheochromocytomas

Pheochromocytoma (PCC) and paraganglioma (PGL) are rare neuroendocrine tumors that are hereditary in up to 50% of patients. The gene encoding transmembrane-protein-127 (TMEM127) is one of the PCC/PGL-susceptibility genes with an autosomal dominant inheritance pattern. Here, we report 2 patients with bilateral PCC who both harbored a homozygous TMEM127-mutation. In a 31-year-old mentally retarded patient, the homozygous c.410-2A > G mutation was discovered during an update of DNA analysis. A 26-year-old mentally retarded patient was found to have a homozygous c.3G > A mutation. The parents of both patients were consanguineous. We reviewed previously reported clinical features of TMEM127 mutation carriers and compared our findings with case descriptions of homozygous mutations in other PGL/PCC-susceptibility genes. Homozygosity for an autosomal dominant inherited disorder is an extremely rare phenomenon and has, to our knowledge, not been reported before for the gene encoding TMEM127. In the present cases, the clinical picture does not seem to be very different from heterozygous TMEM127 mutation carriers, except for a relatively large tumor size and more pronounced plasma metanephrine concentration. It is unclear whether the mental retardation is causally related to homozygosity of the TMEM127 mutations. Updating genetic screening in patients in whom PCC/PGL has been diagnosed in the past should be considered as it might provide clinically relevant information.

Exome analysis of carotid body tumor

Background

Carotid body tumor (CBT) is a form of head and neck paragangliomas (HNPGLs) arising at the bifurcation of carotid arteries. Paragangliomas are commonly associated with germline and somatic mutations involving at least one of more than thirty causative genes. However, the specific functionality of a number of these genes involved in the formation of paragangliomas has not yet been fully investigated.

Methods

Exome library preparation was carried out using Nextera® Rapid Capture Exome Kit (Illumina, USA). Sequencing was performed on NextSeq 500 System (Illumina).

Results

Exome analysis of 52 CBTs revealed potential driver mutations (PDMs) in 21 genes: ARNT, BAP1, BRAF, BRCA1, BRCA2, CDKN2A, CSDE1, FGFR3, IDH1, KIF1B, KMT2D, MEN1, RET, SDHA, SDHB, SDHC, SDHD, SETD2, TP53BP1, TP53BP2, and TP53I13. In many samples, more than one PDM was identified. There are also 41% of samples in which we did not identify any PDM; in these cases, the formation of CBT was probably caused by the cumulative effect of several not highly pathogenic mutations. Estimation of average mutation load demonstrated 6–8 mutations per megabase (Mb). Genes with the highest mutation rate were identified.

Conclusions

Exome analysis of 52 CBTs for the first time revealed the average mutation load for these tumors and also identified potential driver mutations as well as their frequencies and co-occurrence with the other PDMs.

Electronic supplementary material

The online version of this article (10.1186/s12920-018-0327-0) contains supplementary material, which is available to authorized users.

Looking beyond the thyroid: advances in the understanding of pheochromocytoma and hyperparathyroidism phenotypes in MEN2 and of non-MEN2 familial forms

Over the last years, the knowledge of MEN2 and non-MEN2 familial forms of pheochromocytoma (PHEO) has increased. In MEN2, PHEO is the second most frequent disease: the penetrance and age at diagnosis depend on the mutation of RET Given the prevalence of bilateral PHEO (50% by age 50), adrenal sparing surgery, aimed at sparing a part of the adrenal cortex to avoid adrenal insufficiency, should be systematically considered in patients with bilateral PHEO. Non-MEN2 familial forms of PHEO now include more than 20 genes: however, only small phenotypic series have been reported, suggesting that phenotypic features of isolated hereditary PHEO must be better explored, and follow-up series are needed to better understand the outcome of patients carrying mutations of these genes. The first part of this review will mainly focus on these points. In the second part, a focus will be given on MEN2 and non-MEN2 familial forms of hyperparathyroidism (HPTH). Again, the management of MEN2 HPTH should be aimed at curing the disease while preserving an optimal quality of life by a tailored parathyroidectomy. The phenotypes and outcome of MEN1-, MEN4- and HRPT2-related HPTH are briefly described, with a focus on the most recent literature data and is compared with familial hypocalciuric hypercalcemia.

Extent of surgery for phaeochromocytomas in the genomic era

Background

Germline mutations are present in 20–30 per cent of patients with phaeochromocytoma. For patients who develop bilateral disease, complete removal of both adrenal glands (total adrenalectomy) will result in lifelong adrenal insufficiency with an increased risk of death from adrenal crisis. Unilateral/bilateral adrenal-sparing surgery (subtotal adrenalectomy) offers preservation of cortical function and independence from steroids, but leaves the adrenal medulla in situ and thus at risk of developing new and possibly malignant disease. Here, present knowledge about how tumour genotype relates to clinical behaviour is reviewed, and application of this knowledge when choosing the extent of adrenalectomy is discussed.

Methods

A literature review was undertaken of the penetrance of the different genotypes in phaeochromocytomas, the frequency of bilateral disease and malignancy, and the underlying pathophysiological mechanisms, with emphasis on explaining the clinical phenotypes of phaeochromocytomas and their associated syndromes.

Results

Patients with bilateral phaeochromocytomas most often have multiple endocrine neoplasia type 2 (MEN2) or von Hippel–Lindau disease (VHL) with high-penetrance mutations for benign disease, whereas patients with mutations in the genes encoding SDHB (succinate dehydrogenase subunit B) or MAX (myelocytomatosis viral proto-oncogene homologue-associated factor X) are at increased risk of malignancy.

Conclusion

Adrenal-sparing surgery should be the standard approach for patients who have already been diagnosed with MEN2 or VHL when operating on the first side, whereas complete removal of the affected adrenal gland(s) is generally recommended for patients with SDHB or MAX germline mutations. Routine assessment of a patient's genotype, even after the first operation, can be crucial for adopting an appropriate strategy for follow-up and future surgery.

New Perspectives on Pheochromocytoma and Paraganglioma: Toward a Molecular Classification

A molecular biology-based taxonomy has been proposed for pheochromocytoma and paraganglioma (PPGL). Data from the Cancer Genome Atlas revealed clinically relevant prognostic and predictive biomarkers and stratified PPGLs into three main clusters. Each subgroup has a distinct molecular-biochemical-imaging signature. Concurrently, new methods for biochemical analysis, functional imaging, and medical therapies have also become available. The research community now strives to match the cluster biomarkers with the best intervention. The concept of precision medicine has been long awaited and holds great promise for improved care. Here, we review the current and future PPGL classifications, with a focus on hereditary syndromes. We discuss the current strengths and shortcomings of precision medicine and suggest a condensed manual for diagnosis and treatment of both adult and pediatric patients with PPGL. Finally, we consider the future direction of this field, with a particular focus on how advanced molecular characterization of PPGL can improve a patient's outcome, including cures and, ultimately, disease prevention.

Treatment for Malignant Pheochromocytomas and Paragangliomas: 5 Years of Progress

PURPOSE OF REVIEW

The purpose of this manuscript is to review the progress in the field of therapeutics for malignant pheochromocytomas and sympathetic paraganglioma (MPPG) over the past 5 years.

RECENT FINDINGS

The manuscript will describe the clinical predictors of survivorship and their influence on the first TNM staging classification for pheochromocytomas and sympathetic paragangliomas, the treatment of hormonal complications, and the rationale that supports the resection of the primary tumor and metastases in patients with otherwise incurable disease. Therapeutic options for patients with bone metastasis to the spine will be presented. The manuscript will also review chemotherapy and propose a maintenance regimen with dacarbazine for patients initially treated with cyclophosphamide, vincristine, and dacarbazine. Finally, the manuscript will review preliminary results of several phase 2 clinical trials of novel radiopharmaceutical agents and tyrosine kinase inhibitors. MPPGs are very rare neuroendocrine tumors. MPPGs are usually characterized by a large tumor burden, excessive secretion of catecholamines, and decreased overall survival. Recent discoveries have enhanced our knowledge of the pathogenesis and phenotypes of MPPG. This knowledge is leading to a better understanding of the indications and limitations of the currently available localized and systemic therapies as well as the development of phase 2 clinical trials for novel medications.

The clinical genetics of phaeochromocytoma and paraganglioma

Phaeochromocytoma and paraganglioma are rare catecholamine-producing tumours, recognised to have one of the richest hereditary backgrounds of all neoplasms, with germline mutations seen in approximately 30% of patients. They can be a part of genetic syndromes such as MEN 2 or Neurofibromatosis type 1, or can be found as apparently sporadic tumours. Germline mutations are almost always found in syndromic patients. Nonetheless, apparently sporadic phaeochromocytoma too show high germline mutation rates. Early detection of a genetic mutation can lead to early diagnosis of further tumours via surveillance, early treatment and better prognosis. Apart from this, the genetic profile has important relevance for tumour location and biochemical profile, and can be a useful predictor of future tumour behaviour. It also enables family screening and surveillance. Moreover, recent studies have demonstrated significant driver somatic mutations in up to 75% of all tumours. Arch Endocrinol Metab. 2017;61(5):490-500.

Clinical Characterization of the Pheochromocytoma and Paraganglioma Susceptibility Genes SDHA, TMEM127, MAX, and SDHAF2 for Gene-Informed Prevention

Importance

Effective cancer prevention is based on accurate molecular diagnosis and results of genetic family screening, genotype-informed risk assessment, and tailored strategies for early diagnosis. The expanding etiology for hereditary pheochromocytomas and paragangliomas has recently included SDHA, TMEM127, MAX, and SDHAF2 as susceptibility genes. Clinical management guidelines for patients with germline mutations in these 4 newly included genes are lacking.

Objective

To study the clinical spectra and age-related penetrance of individuals with mutations in the SDHA, TMEM127, MAX, and SDHAF2 genes.

Design, Setting, and Patients

This study analyzed the prospective, longitudinally followed up European-American-Asian Pheochromocytoma-Paraganglioma Registry for prevalence of SDHA, TMEM127, MAX, and SDHAF2 germline mutation carriers from 1993 to 2016. Genetic predictive testing and clinical investigation by imaging from neck to pelvis was offered to mutation-positive registrants and their relatives to clinically characterize the pheochromocytoma/paraganglioma diseases associated with mutations of the 4 new genes.

Main Outcomes and Measures

Prevalence and spectra of germline mutations in the SDHA, TMEM127, MAX, and SDHAF2 genes were assessed. The clinical features of SDHA, TMEM127, MAX, and SDHAF2 disease were characterized.

Results

Of 972 unrelated registrants without mutations in the classic pheochromocytoma- and paraganglioma-associated genes (632 female [65.0%] and 340 male [35.0%]; age range, 8-80; mean [SD] age, 41.0 [13.3] years), 58 (6.0%) carried germline mutations of interest, including 29 SDHA, 20 TMEM127, 8 MAX, and 1 SDHAF2. Fifty-three of 58 patients (91%) had familial, multiple, extra-adrenal, and/or malignant tumors and/or were younger than 40 years. Newly uncovered are 7 of 63 (11%) malignant pheochromocytomas and paragangliomas in SDHA and TMEM127 disease. SDHA disease occurred as early as 8 years of age. Extra-adrenal tumors occurred in 28 mutation carriers (48%) and in 23 of 29 SDHA mutation carriers (79%), particularly with head and neck paraganglioma. MAX disease occurred almost exclusively in the adrenal glands with frequently bilateral tumors. Penetrance in the largest subset, SDHA carriers, was 39% at 40 years of age and is statistically different in index patients (45%) vs mutation-carrying relatives (13%; P < .001).

Conclusions and Relevance

The SDHA, TMEM127, MAX, and SDHAF2 genes may contribute to hereditary pheochromocytoma and paraganglioma. Genetic testing is recommended in patients at clinically high risk if the classic genes are mutation negative. Gene-specific prevention and/or early detection requires regular, systematic whole-body investigation.

ARHI is a novel epigenetic silenced tumor suppressor in sporadic pheochromocytoma

Pheochromocytoma (PCC) is related to germline mutations in 12 susceptibility genes. Although comparative genomic hybridization array has revealed some putative tumor suppressor genes on the short arm of chromosome 1 that are likely to be involved in PCC tumorigenesis, the molecules involved, except for those encoded by known susceptibility genes, have not been found in the generation of sporadic tumors. In the present work, we first identified that the unmethylated allele of Aplasia Ras homolog member I (ARHI) was deleted in most PCC tumors which retained a hypermethylated copy, while its mRNA level was significantly correlated with the unmethylated copy. De-methylation experiments confirmed that expression of ARHI was also regulated by the methylation level of the remaining allele. Furthermore, ARHI overexpression inhibited cell proliferation, with cell cycle arrest and induction of apoptosis, in ARHI-negative primary human PCC cells, whereas knockdown of ARHI demonstrated the opposite effect in ARHI-positive primary human PCC cells. Finally, we demonstrated that ARHI has the ability to suppress pAKT and pErK1/2, to promote the expression of p21^Waf1/Cip1 and p27^Kip1, and also to increase p27^Kip1 protein stability. In summary, ARHI was silenced or downregulated in PCC tissues harboring only one hypermethylated allele. ARHI contributes to tumor suppression through inhibition of PI3K/AKT and MAKP/ERK pathways, to upregulate cell cycle inhibitors such as p27^Kip1. We therefore reasoned that ARHI is a novel epigenetic silenced tumor suppressor gene on chromosome 1p that is involved in sporadic PCC tumorigenesis.

Primary Renal Paragangliomas and Renal Neoplasia Associated with Pheochromocytoma/Paraganglioma: Analysis of von Hippel-Lindau (VHL), Succinate Dehydrogenase (SDHX) and Transmembrane Protein 127 (TMEM127)

Alterations of von Hippel-Lindau (VHL), succinate dehydrogenase (SDHX), and TMEM127 have been associated with the development of pheochromocytomas (PCs) and paragangliomas (PGLs) and are also associated with the development of renal neoplasms. This study involved 2 primary renal PGL and 12 cases of PC/PGL with associated renal neoplasia with a mean follow up of 74 months. Germline VHL and SDHX mutation status was obtained from the medical record. Immunohistochemistry for SDHB and mutation analysis for TMEM127 was performed, in addition to analysis of The Cancer Genome Atlas datasets for SDHX and TMEM127 mutated renal cell carcinomas (RCCs). The spectrum of renal neoplasia included clear cell and tubulocystic and papillary RCC, as well as a case of multiple papillary adenomas. Three patients had metastatic PC/PGL and three patients had VHL syndrome. Previously unreported TMEM127 alterations were identified in two patients, both without evidence of VHL syndrome or SDH-deficiency, and were classified as variants of uncertain significance. Primary renal PGL and neoplasia was associated with about 2% of 710 cases of PC/PGL. These were diagnosed concurrently or on average 27 months prior to the PC/PGL, and most were low-grade, low-stage clear cell RCCs. Up to half of patients with PC/PGL and renal neoplasia had VHL syndrome, SDH deficiency, or alterations in TMEM127. One (of three) case of metastatic PC/PGL had SDHB mutation and loss of SDHB by immunohistochemistry. The other two cases had retained SDHB expression.