Minireview: the busy road to pheochromocytomas and paragangliomas has a new member, TMEM127

An Unexpected Death Due to a Subclinical Pheochromocytoma After an Induced Abortion

ABSTRACT

Deaths due to hypertensive crisis can be unexplained because of the impossibility to identify-before the decease-the specific cause of the crisis. In these cases, autopsy and microscopic examinations are needed. It can happen that the request to conduct these examinations can be submitted to forensic pathologists by prosecutors to ascertain medical malpractice claims. Indeed, we report the case of a 36-year-old woman who died after a minimally invasive medical procedure because of the occurrence of a severe hypertensive crisis. After death, the woman's relatives raised formal complaint for medical malpractice. For this reason, the prosecutor ordered to perform an autopsy. Examining the abdominal cavity, the forensic pathologists identified the left adrenal gland as expanded; in correspondence with organ's medulla, there was a gray and noncapsulated mass. Immunohistochemistry was performed: the microscopic samples were diffusely positive for chromogranin A, suggesting the diagnosis of a subclinical pheochromocytoma. In light of the above, medical malpractice was excluded. This case highlights that forensic pathologists should be aware that, in case of unexpected deaths due to hypertensive crisis, adrenal glands should be always accurately evaluated, performing specific immunohistochemistry study to exclude the presence of a pheochromocytoma.

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.

Hypoxia Signaling and Circadian Disruption in and by Pheochromocytoma

Disruption of the daily (i.e., circadian) rhythms of cell metabolism, proliferation and blood perfusion is a hallmark of many cancer types, perhaps most clearly exemplified by the rare but detrimental pheochromocytomas. These tumors arise from genetic disruption of genes critical for hypoxia signaling, such as von Hippel-Lindau and hypoxia-inducible factor-2 or cellular metabolism, such as succinate dehydrogenase, which in turn impacts on the cellular circadian clock function by interfering with the Bmal1 and/or Clock transcription factors. While pheochromocytomas are often non-malignant, the resulting changes in cellular physiology are coupled to de-regulated production of catecholamines, which in turn disrupt circadian blood pressure variation and therefore circadian entrainment of other tissues. In this review we thoroughly discuss the molecular and physiological interplay between hypoxia signaling and the circadian clock in pheochromocytoma, and how this underlies endocrine disruption leading to loss of circadian blood pressure variation in the affected patients. We furthermore discuss potential avenues for targeting these tumor-specific pathophysiological mechanisms therapeutically in the future.

Pheochromocytoma and Paraganglioma: Genetics, Diagnosis, and Treatment

Pheochromocytomas (PCCs) and paragangliomas (PGLs) are rare but unique neuroendocrine tumors. The hypersecretion of catecholamines from the tumors can be associated with high morbidity and mortality, even when tumors are benign. Up to 40% of PCCs/PGLs are associated with germline mutations in susceptibility genes. About one-quarter are malignant, defined by the presence of distant metastases. Treatment options for unresectable metastatic disease, including chemotherapy, (131)I-MIBG, and radiation, can offer limited tumor and hormone control, although none are curative. This article reviews the inherited genetics, diagnosis, and treatment of PCCs and PGLs.

Patient with inoperable pheochromocytoma

Malignant pheochromocytoma is a tumour with a very low incidence that occurs sporadically or in the presence of multiple endocrine neoplasia. We present the case of a woman with a sporadic occurrence of pheochromocytoma diagnosed in the phase of multiple dissemination in the abdominal cavity and overexpressing adrenaline, noradrenaline, and dopamine. Local transarterial chemoembolization and systemic treatment with lanreotide resulted in a very good response, a decrease in the production of catecholamines for 12 months and a partial decrease for another 8 months, with stabilization of disease determined by imaging. Systemic treatment with tegafur resulted in disease stabilization lasting 50 months, after which the drug was discontinued because of adverse effects. Maintenance therapy with lanreotide continues, and no disease progression has been observed for 4 months. The treatment algorithm for such patients is multidisciplinary and must always take into account the current scope of the disease, intercurrence, and the general condition of the patient.

HIF signaling pathway in pheochromocytoma and other neuroendocrine tumors

Hypoxia-inducible factors (HIFs) are transcription factors controlling energy, iron metabolism, erythropoiesis, and development. Dysregulation of these proteins contributes to tumorigenesis and cancer progression. Recent findings revealed the important role of HIFs in the pathogenesis of neuroendocrine tumors, especially pheochromocytoma (PHEO) and paraganglioma (PGL). PHEOs and PGLs are catecholamine-producing tumors arising from sympathetic- or parasympathetic-derived chromaffin tissue. To date, eighteen PHEO/PGL susceptibility genes have been identified. Based on the main signaling pathways, PHEOs/PGLs have been divided into two clusters, pseudohypoxic cluster 1 and cluster 2, rich in kinase receptor signaling and protein translation pathways. Recent data suggest that both clusters are interconnected via the HIF signaling and its role in tumorigenesis is supported by newly described somatic and germline mutations in HIF2A gene in patients with PHEOs/PGLs associated with polycythemia, and in some of them also with somatostatinoma. Moreover, HIFalpha signaling has also been shown to be upregulated in neuroendocrine tumors other than PHEO/PGL. Some of these tumors are components of hereditary tumor syndromes which can be associated with PHEO/PGL, but also in ileal carcinoids or melanoma. HIF signaling appears to be one of the crucial players in tumorigenesis, which could suggest new therapeutic approaches for treatment of neuroendocrine tumors.

Management and follow up of extra-adrenal phaeochromocytoma

Introduction

The prevalence of phaeochromocytoma (PCC) in patients with hypertension is 0.1–0.6% and about 10% of PCCs are detected in extra–adrenal tissue. The diagnosis and therapy of this rare disease detected as a retroperitoneal tumor mass can be difficult for clinicians.

Material and methods

A PubMed database was searched for the peer–reviewed articles, the listed articles until Dec 2012 were included. Following key words were used: “extra–adrenal phaeochromocytoma”, “paraganglioma”, “diagnosis”, “therapy”, “surgery”, “genetic analysis”, and “SDH mutation”.

Results

Magnetic Resonance Imaging (MRI) and Computed Tomography (CT) are first choice imaging tools for PCC (sensitivity 90–100%). For the validation of the diagnosis or follow up, the functional imaging 123I–metaiodobenzylguanidine (MIBG) or Fluorine–18–L–dihydroxyphenylalanine (18F–DOPA) positron emission tomography (excellent specificity and sensitivity of 90–100% in detection of small tumors >1–2 cm) are used. Laparoscopic surgery with complete resection is a safe and a first choice approach. The conversion (about 5%) to direct open operation was needed for large lesions (>8 cm) with the suspicion of malignancy. Currently, there are no histological criteria for distinguishing benign and malignant tumors. The genetic testing (Sanger DNA sequencing) for hereditary syndromes (von Hippel–Lindau, neurofibromatosis, etc.) is used for prediction of malignancy and recurrence. All patients should get individual and risk–adapted genetic analysis and consultation, including family members. The rate of malignancy in ePCC is about 30% (PCC about 5–10%). In patients with proven SDHB germline mutations, higher malignancy rate, multiple PCCs and recurrences are likely. A stringent lifelong clinical follow–up is recommended in these cases. Patients with syndromic hereditary forms should be screened for other often associated neoplasms.

Conclusions

New imaging tools and genetic analysis are crucial to improve the diagnosis and prognosis of phaeochromocytoma.

Hereditary Pheochromocytoma

INTRODUCTION

Pheochromocytomas (PHEO) and paragangliomas (PGL) are rare neuroendocrine tumors with an estimated occurrence of 2 to 5 patients per million per year and an incidence of about 1 per 100 000 in the general population. These tumors may arise sporadically or be associated to various syndromes, namely multiple endocrine neoplasia type 2, neurofibromatosis type 1, Von Hippel-Lindau syndrome, and hereditary paraganglioma-pheochromocytoma syndromes.

OBJECTIVES

This article aims to review the current epidemiology, pathogenesis, clinical presentation, and genetic aspects of syndromes associated with hereditary PHEO/PGL.

METHODS

The literature research, conducted at PubMed database, included review articles, published from February 2009 to February 2014, written in English or Portuguese, using as query: "Hereditary AND Pheochromocytoma."

CONCLUSION

These tumors can be part of a myriad hereditary conditions that are not yet fully understood. Nevertheless, important systemic symptoms and even fatal outcomes can occur. Knowledge of these hereditary conditions can ensure a more efficient detection, treatment, and even prevention of these neuroectodermal tumors, thus new tests and studies should be conducted.

Genetic testing in the clinical care of patients with pheochromocytoma and paraganglioma

PURPOSE OF REVIEW

Paraganglioma and pheochromocytoma (PGL/PCC) are tumours of neural crest origin that can present along a clinical spectrum ranging from apparently sporadic, isolated tumours to a more complex phenotype of one or multiple tumours in the context of other clinical features and family history suggestive of a defined hereditary syndrome. Genetic testing for hereditary PGL/PCC can help to confirm a genetic diagnosis for sporadic and syndromic cases. Informative genetic testing serves to clarify future risks for the patient and family members.

RECENT FINDINGS

Genetic discovery in the last decade has identified new PGL/PCC susceptibility loci. We summarize a contemporary approach adopted in our programme for genetic evaluation, testing and prospective management involving biochemical monitoring and imaging for hereditary PGL/PCC. A clinical vignette is presented to illustrate our practice.

SUMMARY

Current estimates that up to 40% of PGL/PCC are associated with germline mutations have implications for genetic testing recommendations. Prospective management of patients with defined hereditary susceptibility is based on established guidelines for well characterized syndromes. Management of tumour risk for rare syndromes, newly defined genetic associations and undefined genetic susceptibility in the setting of significant family history presents a challenge. Sustained discovery of new PGL/PCC genes underscores the need for a practice of continued genetic evaluation for patients with uninformative results. All patients with PGL/PCC should undergo genetic testing to identify potential hereditary tumour susceptibility.

Current views on cell metabolism in SDHx-related pheochromocytoma and paraganglioma

Warburg's metabolic hypothesis is based on the assumption that a cancer cell's respiration must be under attack, leading to its damage, in order to obtain increased glycolysis. Although this may not apply to all cancers, there is some evidence proving that primarily abnormally functioning mitochondrial complexes are indeed related to cancer development. Thus, mutations in complex II (succinate dehydrogenase (SDH)) lead to the formation of pheochromocytoma (PHEO)/paraganglioma (PGL). Mutations in one of the SDH genes (SDHx mutations) lead to succinate accumulation associated with very low fumarate levels, increased glutaminolysis, the generation of reactive oxygen species, and pseudohypoxia. This results in significant changes in signaling pathways (many of them dependent on the stabilization of hypoxia-inducible factor), including oxidative phosphorylation, glycolysis, specific expression profiles, as well as genomic instability and increased mutability resulting in tumor development. Although there is currently no very effective therapy for SDHx-related metastatic PHEOs/PGLs, targeting their fundamental metabolic abnormalities may provide a unique opportunity for the development of novel and more effective forms of therapy for these tumors.

A new twist in neuroendocrine tumor research: Pacak-Zhuang syndrome, HIF-2α as the major player in its pathogenesis and future therapeutic options

Backround. There is increasing evidence of the role of hypoxia or pseudohypoxia in tumorigenesis, including pheochromocytoma (PHEO) and paraganglioma (PGL). (Pseudo)hypoxia leads to activation of hypoxia-inducible transcription factors (HIFs) and thus, promotes the transcription of hypoxia-responsive genes which are involved in tumorigenesis. Recently identified is a new syndrome consisting of multiple and recurrent PGLs or PHEOs, somatostatinoma, and congenital polycythemia, due to somatic hypoxia-inducible factor 2α gene (HIF2A) mutations.

METHODS AND RESULTS

PubMed and Web of Science online databases were used to search reviews and original articles on the HIF, PHEO/PGL, and Pacak-Zhuang syndrome.

CONCLUSIONS

The novel somatic and germline gain-of-function HIF2A mutations described latterly emphasize the role of the HIF-2α in the PHEO/PGL development and these findings designate HIF, especially HIF-2α, as a promising treatment target.

The genetic basis of pheochromocytoma and paraganglioma: implications for management

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

Red face revisited: Flushing

The term red face is reserved for lesions located exclusively or very predominantly on the face that result from changes in cutaneous blood flow triggered by multiple different conditions. Facial erythema may not only present clinically as a distinct entity, but can also be a sign of other diseases. Patients with a red face challenge clinicians to consider a broad differential diagnosis. Diagnosis is based on date and mode of appearance, characteristics of the erythema, functional signs, and associated systemic manifestations. In most cases, the cause is a benign disease such as rosacea, contact dermatitis, photodermatosis, and climacterium, and a thorough history and physical examination is enough to make a diagnosis; facial erythema may also present as a symptom of drug allergies, cardiac disease, carcinoid syndrome, pheochromocytoma, mastocytosis, and anaphylaxis, as well as some rare causes such as medullary carcinoma of the thyroid, pancreatic cell tumor, and renal carcinoma where further laboratory, radiologic, or histopathologic studies are required. In this review, the mechanisms of flushing, its clinical differential diagnosis, and management of various conditions that cause flushing are discussed.

Molecular genetics of paragangliomas of the skull base and head and neck region: implications for medical and surgical management

Paragangliomas are rare, slow-growing tumors that frequently arise in the head and neck, with the carotid bodies and temporal bone of the skull base being the most common sites. These neoplasms are histologically similar to pheochromocytomas that form in the adrenal medulla and are divided into sympathetic and parasympathetic subtypes based on functionality. Skull base and head and neck region paragangliomas (SHN-PGs) are almost always derived from parasympathetic tissue and rarely secrete catecholamines. However, they can cause significant morbidity by mass effect on various cranial nerves and major blood vessels. While surgery for SHN-PG can be curative, postoperative deficits and recurrences make these lesions challenging to manage. Multiple familial syndromes predisposing individuals to development of paragangliomas have been identified, all involving mutations in the succinate dehydrogenase complex of mitochondria. Mutations in this enzyme lead to a state of “pseudohypoxia” that upregulates various angiogenic, survival, and proliferation factors. Moreover, familial paraganglioma syndromes are among the rare inherited diseases in which genomic imprinting occurs. Recent advances in gene arrays and transcriptome/exome sequencing have identified an alternate mutation in sporadic SHN-PG, which regulates proto-oncogenic pathways independent of pseudohypoxia-induced factors. Collectively these findings demonstrate that paragangliomas of the skull base and head and neck region have a distinct genetic signature from sympathetic-based paragangliomas occurring below the neck, such as pheochromocytomas. Paragangliomas serve as a unique model of primarily surgically treated neoplasms whose future will be altered by the elucidation of their genomic complexities. In this review, the authors present an analysis of the molecular genetics of SHN-PG and provide future directions in patient care and the development of novel therapies.

Hypoxia-inducible factor signaling in pheochromocytoma: turning the rudder in the right direction

Many solid tumors, including pheochromocytoma (PHEO) and paraganglioma (PGL), are characterized by a (pseudo)hypoxic signature. (Pseudo)hypoxia has been shown to promote both tumor progression and resistance to therapy. The major mediators of the transcriptional hypoxic response are hypoxia-inducible factors (HIFs). High levels of HIFs lead to transcription of hypoxia-responsive genes, which are involved in tumorigenesis. PHEOs and PGLs are catecholamine-producing tumors arising from sympathetic- or parasympathetic-derived chromaffin tissue. In recent years, substantial progress has been made in understanding the metabolic disturbances present in PHEO and PGL, especially because of the identification of some disease-susceptibility genes. To date, fifteen PHEO and PGL susceptibility genes have been identified. Based on the main transcription signatures of the mutated genes, PHEOs and PGLs have been divided into two clusters, pseudohypoxic cluster 1 and cluster 2, rich in kinase receptor signaling and protein translation pathways. Although these two clusters seem to show distinct signaling pathways, recent data suggest that both clusters are interconnected by HIF signaling as the important driver in their tumorigenesis, and mutations in most PHEO and PGL susceptibility genes seem to affect HIF-α regulation and its downstream signaling pathways. HIF signaling appears to play an important role in the development and growth of PHEOs and PGLs, which could suggest new therapeutic approaches for the treatment of these tumors.

Integrative analysis of miRNA and mRNA expression profiles in pheochromocytoma and paraganglioma identifies genotype-specific markers and potentially regulated pathways

Pheochromocytomas (PCCs) and paragangliomas (PGLs) are rare neuroendocrine neoplasias of neural crest origin that can be part of several inherited syndromes. Although their mRNA profiles are known to depend on genetic background, a number of questions related to tumor biology and clinical behavior remain unanswered. As microRNAs (miRNAs) are key players in the modulation of gene expression, their comprehensive analysis could resolve some of these issues. Through characterization of miRNA profiles in 69 frozen tumors with germline mutations in the genes SDHD, SDHB, VHL, RET, NF1, TMEM127, and MAX, we identified miRNA signatures specific to, as well as common among, the genetic groups of PCCs/PGLs. miRNA expression profiles were validated in an independent series of 30 composed of VHL-, SDHB-, SDHD-, and RET-related formalin-fixed paraffin-embedded PCC/PGL samples using quantitative real-time PCR. Upregulation of miR-210 in VHL- and SDHB-related PCCs/PGLs was verified, while miR-137 and miR-382 were confirmed as generally upregulated in PCCs/PGLs (except in MAX-related tumors). Also, we confirmed overexpression of miR-133b as VHL-specific miRNAs, miR-488 and miR-885-5p as RET-specific miRNAs, and miR-183 and miR-96 as SDHB-specific miRNAs. To determine the potential roles miRNAs play in PCC/PGL pathogenesis, we performed bioinformatic integration and pathway analysis using matched mRNA profiling data that indicated a common enrichment of pathways associated with neuronal and neuroendocrine-like differentiation. We demonstrated that miR-183 and/or miR-96 impede NGF-induced differentiation in PC12 cells. Finally, global proteomic analysis in SDHB and MAX tumors allowed us to determine that miRNA regulation occurs primarily through mRNA degradation in PCCs/PGLs, which partially confirmed our miRNA-mRNA integration results.

Simultaneous presentation of giant pheochromocytoma, primary hyperparathyroidism, and mixed-medullary-papillary thyroid cancer in MEN 2A

The aim of this study was to describe a young man with probably the largest pheochromocytoma associated with MEN 2A, described till date. The patient, a non-vegetarian, fifth of eight siblings, married, having five children, presented with episodes of difficult-to-control hypertension requiring over five antihypertensives. He was referred to us with an abdominal CT scan that revealed a 16 cm left-sided adrenal mass. Biochemical testing confirmed a catecholamine secreting pathology. Histopathology confirmed the mass as a pheochromocytoma weighing 1.8 kg. Further evaluation suggested a parathormone-dependent hypercalcemia and a left-sided thyroid mass. Histopathology confirmed parathyroid hyperplasia and medullary carcinoma of the thyroid mixed with papillary carcinoma of thyroid. Putting all the findings together showed that the patient was suffering from multiple endocrine neoplasia 2. Multiple endocrine neoplasia 2A is a rare syndrome. The case is unique in the way it presented, with all the three tumors at the same time. The management was bold and addressed all the three lesions in the same hospital admission. We are also reporting the largest described case of pheochromocytoma from India.

Genetics of pheochromocytoma and paraganglioma syndromes: new advances and future treatment options

PURPOSE OF REVIEW

To summarize the recent advances in the genetics of pheochromocytoma and paraganglioma (PHEO/PGL), focusing on the new susceptibility genes and dividing PHEOs/PGLs into two groups based on their transcription profile.

RECENT FINDINGS

Recently, TMEM127, MYC-associated factor X, and hypoxia-inducible factor (HIF) 2α have been described in the pathogenesis of PHEOs/PGLs. Thus, now about 30-40% of these tumors are linked to the germline mutations, which also include mutations in the VHL, RET, NF1, SDHx, and SDHAF2 genes. Furthermore, PHEOs/PGLs have been divided into two groups, cluster 1 (SDHx/VHL) and cluster 2 (RET/NF1), based on the transcription profile revealed by genome-wide expression microarray analysis.

SUMMARY

PHEOs/PGLs are the most inherited tumors among (neuro)endocrine tumors. Future approaches in genetics, including whole-genome sequencing, will allow the discovery of additional PHEO/PGL susceptibility genes. The current division of PHEOs/PGLs into cluster 1 and 2 provides us with additional knowledge related to the pathogenesis of these tumors, including the introduction of new treatment options for patients with metastatic PHEOs/PGLs. New discoveries related to the role of the HIF-1/HIF-2α genes in the pathogenesis of almost all inherited PHEOs/PGLs may call for a new regrouping of these tumors and discoveries of new treatment targets.

Combined inhibition of mTORC1 and mTORC2 signaling pathways is a promising therapeutic option in inhibiting pheochromocytoma tumor growth: in vitro and in vivo studies in female athymic nude mice

Several lines of evidence, including the recent discovery of novel susceptibility genes, point out an important role for the mammalian target of rapamycin (mTOR) signaling pathway in the development of pheochromocytoma. Analyzing a set of pheochromocytomas from patients with different genetic backgrounds, we observed and confirmed a significant overexpression of key mTOR complex (mTORC) signaling mediators. Using selective ATP-competitive inhibitors targeting both mTORC1 and mTORC2, we significantly arrested the in vitro cell proliferation and blocked migration of pheochromocytoma cells as a result of the pharmacological suppression of the Akt/mTOR signaling pathway. Moreover, AZD8055, a selective ATP-competitive dual mTORC1/2 small molecular inhibitor, significantly reduced the tumor burden in a model of metastatic pheochromocytoma using female athymic nude mice. This study suggests that targeting both mTORC1 and mTORC2 is a potentially rewarding strategy and supports the application of selective inhibitors in combinatorial drug regimens for metastatic pheochromocytoma.

Identical germline mutations in the TMEM127 gene in two unrelated Japanese patients with bilateral pheochromocytoma

OBJECTIVE

Recently, TMEM127 was shown to be a new pheochromocytoma susceptibility gene; this is consistent with its function as a tumour suppressor gene (Journal of Clinical Endocrinology and Metabolism, 2009, 94, 2817). Most pheochromocytomas arise from the adrenal medulla, and in approximately half of the cases, the tumours are bilateral (Journal of Clinical Endocrinology and Metabolism, 2009, 94, 2817; Journal of the American Medical Association, 2004, 292, 943; Human Mutation, 2010, 31, 41; Science, 2009, 325, 1139). The aim of the present study was to determine whether TMEM127 mutations are involved in the pathogenesis of pheochromocytomas/paragangliomas in Japanese subjects.

PATIENTS AND METHODS

For this study, 74 unrelated patients with pheochromocytoma/paraganglioma who tested negative for mutations and deletions in RET, VHL, SDHB and SDHD were recruited through a multi-institutional collaborative effort in Japan. The TMEM127 gene sequence was determined in their germline DNA, and tumour DNA was analysed for the loss of heterozygosity. In addition, their TMEM127 gene sequences were compared with sequences from 114 normal healthy, ethnically matched controls.

RESULTS

Among the 74 eligible patients, two unrelated patients (2·7%) with bilateral adrenal pheochromocytoma were found to have an identical germline TMEM127 mutation (c.116_119delTGTC, p.Ile41ArgfsX39) associated with 2q deletion loss of heterozygosity, which was also previously described in a Brazilian case (Journal of the American Medical Association, 2004, 292, 943). We also determined that none of the 114 normal healthy controls had this deletion mutation.

CONCLUSION

This is the first report showing that TMEM127 mutation plays a pathological role in pheochromocytoma in an Asian population. Although our surveillance is limited, the prevalence and the phenotype of this gene mutation appear to be similar to those reported in previous studies.

Immunohistochemical evidence of dysregulation of the mammalian target of rapamycin pathway in primary and metastatic pheochromocytomas

OBJECTIVE

To characterize the status of the mammalian target of rapamycin pathway using formalin-fixed, paraffin-embedded specimens from patients with primary and metastatic pheochromocytoma.

METHODS

Tissue microarrays were built from 19 normal adrenal medullas, 39 primary pheochromocytomas, and 8 unrelated metastatic pheochromocytomas. In 2 of the 8 cases of metastatic pheochromocytoma tissues, samples from the primary tumor were available. The expression levels of phosphatase and tensin homolog, phosphorylated Akt, phosphorylated S6, p27, and c-myc were evaluated by immunohistochemistry.

RESULTS

The levels of phosphatase and tensin homolog and p27 were greater in the nontumor tissue than in the primary and metastatic pheochromocytomas. Increasing levels of phosphorylated Akt were noted in the nontumor adrenal medulla, primary pheochromocytomas, and metastatic pheochromocytomas. Finally, the levels of phosphorylated S6 were greater in the metastatic pheochromocytomas than in the nontumor adrenal medulla and primary pheochromocytomas.

CONCLUSION

We found evidence of dysregulation of the mammalian target of rapamycin pathway in primary and metastatic pheochromocytomas, with increased phosphorylated S6 and phosphorylated Akt, and decreased phosphatase and tensin homolog and p27 expression levels. Because the currently available treatment modalities are less than optimal, our findings lend additional support to continuing to explore the utility of mammalian target of rapamycin pathway-targeted therapy for pheochromocytomas.

An update on the genetics of pheochromocytoma

Pheochromocytomas (PHEOs) and paragangliomas (PGLs) are rare neuroendocrine tumors. About 30% or more of them are thought to be of inherited origin due to germ-line mutations in at least 10 well-characterized genes. There are data linking specific genotypes of these tumors to specific locations, typical biochemical phenotypes or future clinical behaviors. Conversely, clinical features, catecholamine production and immunohistochemistry evaluation can help with the proper order of genetic testing for PHEO and PGL. The identification of a germ-line mutation can lead to an early diagnosis, appropriate treatment, regular surveillance and better prognosis not only for the patient but also for their family members. Moreover, the latest discoveries in molecular pathogenesis of these tumors will provide an important basis for future personalized therapy.

Genetics and clinical characteristics of hereditary pheochromocytomas and paragangliomas

Pheochromocytomas (PCCs) and paragangliomas (PGLs) are rare neuroendocrine tumors of the adrenal glands and the sympathetic and parasympathetic paraganglia. They can occur sporadically or as a part of different hereditary tumor syndromes. About 30% of PCCs and PGLs are currently believed to be caused by germline mutations and several novel susceptibility genes have recently been discovered. The clinical presentation, including localization, malignant potential, and age of onset, varies depending on the genetic background of the tumors. By reviewing more than 1700 reported cases of hereditary PCC and PGL, a thorough summary of the genetics and clinical features of these tumors is given, both as part of the classical syndromes such as multiple endocrine neoplasia type 2 (MEN2), von Hippel-Lindau disease, neurofibromatosis type 1, and succinate dehydrogenase-related PCC-PGL and within syndromes associated with a smaller fraction of PCCs/PGLs, such as Carney triad, Carney-Stratakis syndrome, and MEN1. The review also covers the most recently discovered susceptibility genes including KIF1Bβ, EGLN1/PHD2, SDHAF2, TMEM127, SDHA, and MAX, as well as a comparison with the sporadic form. Further, the latest advances in elucidating the cellular pathways involved in PCC and PGL development are discussed in detail. Finally, an algorithm for genetic testing in patients with PCC and PGL is proposed.