Epigenetics of pheochromocytoma and paraganglioma

A comprehensive characterisation of phaeochromocytoma and paraganglioma tumours through histone protein profiling, DNA methylation and transcriptomic analysis genome wide

BACKGROUND

Phaeochromocytomas and paragangliomas (PPGLs) are rare neuroendocrine tumours. Pathogenic variants have been identified in more than 15 susceptibility genes; associated tumours are grouped into three Clusters, reinforced by their transcriptional profiles. Cluster 1A PPGLs have pathogenic variants affecting enzymes of the tricarboxylic acid cycle, including succinate dehydrogenase. Within inherited PPGLs, these are the most common. PPGL tumours are known to undergo epigenetic reprograming, and here, we report on global histone post-translational modifications and DNA methylation levels, alongside clinical phenotypes.

RESULTS

Out of the 25 histone post-translational modifications examined, Cluster 1A PPGLs were distinguished from other tumours by a decrease in hyper-acetylated peptides and an increase in H3K4me2. DNA methylation was compared between tumours from individuals who developed metastatic disease versus those that did not. The majority of differentially methylated sites identified tended to be completely methylated or unmethylated in non-metastatic tumours, with low inter-sample variance. Metastatic tumours by contrast consistently had an intermediate DNA methylation state, including the ephrin receptor EPHA4 and its ligand EFNA3. Gene expression analyses performed to identify genes involved in metastatic tumour behaviour pin-pointed a number of genes previously described as mis-regulated in Cluster 1A tumours, as well as highlighting the tumour suppressor RGS22 and the pituitary tumour-transforming gene PTTG1.

CONCLUSIONS

Combined transcriptomic and DNA methylation analyses revealed aberrant pathways, including ones that could be implicated in metastatic phenotypes and, for the first time, we report a decrease in hyper-acetylated histone marks in Cluster 1 PPGLs.

Possible role of miRNAs in pheochromocytoma pathology - Signaling pathways interaction

Pheochromocytoma (PCC) is a type of neuroendocrine tumor that originates from adrenal medulla or extra-adrenal chromaffin cells and results in the production of catecholamine. Paroxysmal hypertension and cardiovascular crises were among the clinical signs experienced by people with PCC. Five-year survival of advanced-stage PCC is just around 40% despite the identification of various molecular-level fundamentals implicated in these pathogenic pathways. MicroRNAs (miRNAs, miRs) are a type of short, non-coding RNA (ncRNA) that attach to the 3'-UTR of a target mRNA, causing translational inhibition or mRNA degradation. Evidence is mounting that miRNA dysregulation plays a role in the development, progression, and treatment of cancers like PCC. Hence, this study employs a comprehensive and expedited survey to elucidate the potential role of miRNAs in the development of PCC, surpassing their association with survival rates and treatment options in this particular malignancy.

Succinate dehydrogenase and MYC-associated factor X mutations in pituitary neuroendocrine tumours

Pituitary neuroendocrine tumours (PitNETs) associated with paragangliomas or phaeochromocytomas are rare. SDHx variants are estimated to be associated with 0.3-1.8% of PitNETs. Only a few case reports have documented the association with MAX variants. Prolactinomas are the most common PitNETs occurring in patients with SDHx variants, followed by somatotrophinomas, clinically non-functioning tumours and corticotrophinomas. One pituitary carcinoma has been described. SDHC, SDHB and SDHA mutations are inherited in an autosomal dominant fashion and tumorigenesis seems to adhere to Knudson's two-hit hypothesis. SDHD and SDHAF2 mutations most commonly have paternal inheritance. Immunohistochemistry for SDHB or MAX and loss of heterozygosity analysis can support the assessment of pathogenicity of the variants. Metabolomics is promising in the diagnosis of SDHx-related disease. Future research should aim to further clarify the role of SDHx and MAX variants or other genes in the molecular pathogenesis of PitNETs, including pseudohypoxic and kinase signalling pathways along with elucidating epigenetic mechanisms to predict tumour behaviour.

Complex roles of nicotinamide N-methyltransferase in cancer progression

Nicotinamide N-methyltransferase (NNMT) is an intracellular methyltransferase, catalyzing the N-methylation of nicotinamide (NAM) to form 1-methylnicotinamide (1-MNAM), in which S-adenosyl-l-methionine (SAM) is the methyl donor. High expression of NNMT can alter cellular NAM and SAM levels, which in turn, affects nicotinamide adenine dinucleotide (NAD⁺)-dependent redox reactions and signaling pathways, and remodels cellular epigenetic states. Studies have revealed that NNMT plays critical roles in the occurrence and development of various cancers, and analysis of NNMT expression levels in different cancers from The Cancer Genome Atlas (TCGA) dataset indicated that NNMT might be a potential biomarker and therapeutic target for tumor diagnosis and treatment. This review provides a comprehensive understanding of recent advances on NNMT functions in different tumors and deciphers the complex roles of NNMT in cancer progression.

Adrenal pheochromocytoma as a rare cause of reversible left ventricular systolic dysfunction and malignant arrhythmias: a case series

Background

Pheochromocytoma is a neuroendocrine tumour originating from the chromaffin cells of adrenal glands or sympathetic paraganglia. It produces most frequently norepinephrine, epinephrine, and dopamine. As a result of non-specific and variable clinical presentation, pheochromocytoma is difficult to diagnose.

Case summary

A 37-year-old female without medical history and 57-year-old male patient with diabetes, arterial hypertension, and aortic valve replacement with a mechanical prosthesis were admitted to the hospital after successful cardiopulmonary resuscitation due to ventricular fibrillation. In both patients, coronary angiography demonstrated a normal finding, and echocardiography showed left ventricular (LV) contractile dysfunction with improvement in the subsequent examination. In the first patient, the diagnosis of stress-induced cardiomyopathy was considered as the most probable cause. She was later admitted to hospital due to acute pulmonary oedema with hypertensive crisis. Echocardiography documented reversible LV systolic dysfunction with improvement after 3 days. The course of hospitalization of the male was complicated by multi-organ dysfunction syndrome comprising renal failure, paralytic ileus, and pancreatic irritation, which normalized after 2 weeks. The diagnosis of pheochromocytoma was confirmed by laboratory tests and imaging methods. After pharmacological pre-treatment with doxazosin in both patients and bisoprolol in the female, successful adrenalectomies were performed with no relapse of tumour.

Discussion

We describe an atypical clinical presentation of pheochromocytoma with initial cardiac arrest due to ventricular fibrillation and reversible LV systolic dysfunction. Our cases underline that clinical suspicion of pheochromocytoma as a potentially correctable cause should be raised in unexplained cases of severe heart failure, ventricular arrhythmias, and cardiac arrest.

Treatment of Pheochromocytoma Cells with Recurrent Cycles of Hypoxia: A New Pseudohypoxic In Vitro Model

Continuous activation of hypoxia pathways in pheochromocytomas and paragangliomas (PPGLs) is associated with higher disease aggressiveness, for which effective treatment strategies are still missing. Most of the commonly used in vitro models lack characteristics of these pseudohypoxic tumors, including elevated expression of hypoxia-inducible factor (HIF) 2α. To address this shortcoming, we investigated whether recurrent hypoxia cycles lead to continuous activation of hypoxia pathways under normoxic conditions and whether this pseudohypoxia is associated with increased cellular aggressiveness. Rat pheochromocytoma cells (PC12) were incubated under hypoxia for 24 h every 3–4 days, up to 20 hypoxia–reoxygenation cycles, resulting in PC12 Z20 cells. PC12 Z20 control cells were obtained by synchronous cultivation under normoxia. RNA sequencing revealed upregulation of HIF2α in PC12 Z20 cells and a pseudohypoxic gene signature that overlapped with the gene signature of pseudohypoxic PPGLs. PC12 Z20 cells showed a higher growth rate, and the migration and adhesion capacity were significantly increased compared with control cells. Changes in global methylation, together with the pseudohypoxic conditions, may be responsible for the increased aggressiveness of this new model. The established sub-cell line with characteristics of pseudohypoxic PPGLs represent a complementary model for further investigations, for example, with regard to new therapeutic approaches.

What Have We Learned from Molecular Biology of Paragangliomas and Pheochromocytomas?

Recent advances in molecular genetics and genomics have led to increased understanding of the aetiopathogenesis of pheochromocytomas and paragangliomas (PPGLs). Thus, pan-genomic studies now provide a comprehensive integrated genomic analysis of PPGLs into distinct molecularly defined subtypes concordant with tumour genotypes. In addition, new embryological discoveries have refined the concept of how normal paraganglia develop, potentially establishing a developmental basis for genotype-phenotype correlations for PPGLs. The challenge for modern pathology is to translate these scientific discoveries into routine practice, which will be based largely on histopathology for the foreseeable future. Here, we review recent progress concerning the cell of origin and molecular pathogenesis of PPGLs, including pathogenetic mechanisms, genetic susceptibility and molecular classification. The current roles and tools of pathologists are considered from a histopathological perspective, including differential diagnoses, genotype-phenotype correlations and the use of immunohistochemistry in identifying hereditary predisposition and validating genetic variants of unknown significance. Current and potential molecular prognosticators are also presented with the hope that predictive molecular biomarkers will be integrated into risk stratification scoring systems to assess the metastatic potential of these intriguing neoplasms and identify potential drug targets.

Volume-outcome correlation in adrenal surgery-an ESES consensus statement

BACKGROUND

Published data in the last decade showed that a majority of adrenal operations are done by surgeons performing only one such case per year and based on the distribution of personal workloads 'high-volume' surgeons are defined as those doing 4 or more cases/year.

PURPOSE

This paper summarises literature data identified by a working group established by the European Society of Endocrine Surgeons (ESES). The findings were discussed during ESES-2019 conference and members agreed on a consensus statement.

RESULTS

The annual of adrenal operations performed yearly in individual countries was reported to be 800/year in UK and over 1600/year in France. The learning curve of an individual surgeon undertaking laparoscopic, retroperitoneoscopic or robotic adrenalectomy is estimated to be 20-40 cases. Preoperative morbidity and length of stay are more favourable in high-volume centres.

CONCLUSION

The main recommendations are that adrenal surgery should continue only in centres performing at least 6 cases per year, surgery for adrenocortical cancer should be restricted to centres performing at least 12 adrenal operations per year, and an integrated multidisciplinary team should be established in all such centres. Clinical information regarding adrenalectomies should be recorded prospectively and contribution to the established EUROCRINE and ENSAT databases is strongly encouraged. Surgeons wishing to develop expertise in this field should seek mentorship and further training from established adrenal surgeons.

Application of Three-Dimensional Visualization Technology in Laparoscopic Surgery for Pheochromocytoma/Paraganglioma: A Single-Center Experience

OBJECTIVE

To compare the feasibility of three-dimensional visualization technology (3DVT) with that of routine computed tomography (CT) examination during planning of laparoscopic surgery for pheochromocytoma (PHEO) and paraganglioma (PGL) and the effects on operative and postoperative outcomes.

PATIENTS AND METHODS

The clinical data for 36 patients who underwent laparoscopic surgery for PHEO/PGL in our department from January 2016 to April 2017 were analyzed retrospectively. Fourteen patients underwent laparoscopic surgery for PHEO/PGL after preoperative 3DVT-based assessment and 22 after conventional CT examination. The demographic parameters, surgical procedures used, and perioperative outcomes were compared between the two groups. Data were entered into a Microsoft Excel worksheet and analyzed using SPSS version 24.0.

RESULTS

No significant differences were found between the groups with regard to age, gender, body mass index, tumor size, surgical approach, estimated blood loss, mean length of hospital stay, number of hypertensive and hypotensive episodes during surgery, peak blood pressure (BP) values during tumor handling, and minimum values after tumor excision. However, the operating time was significantly shorter and the fluctuations in BP were significantly lower in the 3DVT group.

CONCLUSIONS

3DVT is a feasible and useful preoperative assessment method in patients undergoing laparoscopic surgery for PHEO/PGL. This imaging technique accurately shows the relationship between the tumor and peripheral structures and aids the surgeon's understanding of the anatomic structure in the operative area and in surgical planning.

Pheochromocytomas and Hypertension

PURPOSE OF REVIEW

Pheochromocytomas and paragangliomas (PPGLs) are uncommon catecholamine-producing neuroendocrine neoplasms that usually present with secondary hypertension. This review is to update the current knowledge about these neoplasms, the pathophysiology, genetic aspects and diagnostic and therapeutic algorithms based on scientific literature mostly within the past 3 years.

RECENT FINDINGS

Eighty to eighty-five percent of PPGLs arise from the adrenal medulla (pheochromocytomas; PCCs) and the remainder from the autonomic neural ganglia (paragangliomas; PGLs). Catecholamine excess causes chronic or paroxysmal hypertension associated with sweating, headaches and palpitations, the presenting features of PPGLs, and increases the cardiovascular morbidity and mortality. Genetic testing should be considered in all cases as mutations are reported in 35-40% of cases; 10-15% of PCCs and 20-50% of PGLs can be malignant. Measurements of plasma-free metanephrines or 24-h urine-fractionated metanephrines help biochemical diagnosis with high sensitivity and specificity. Initial anatomical localization after biochemical confirmation is usually with computed tomography (CT) or magnetic resonance imaging (MRI). ¹²³Iodine metaiodobenzylguanidine (¹²³I-MIBG) scintigraphy, positron emission tomography (PET) or single-photon emission computed tomography (SPECT) is often performed for functional imaging and prognostication prior to curative or palliative surgery. Clinical and biochemical follow-up is recommended at least annually after complete tumour excision. Children, pregnant women and older people have higher morbidity and mortality risk. De-bulking surgery, chemotherapy, radiotherapy, radionuclide agents and ablation procedures are useful in the palliation of incurable disease. PPGLs are unique neuroendocrine tumours that form an important cause for endocrine hypertension. The diagnostic and therapeutic algorithms are updated in this comprehensive article.