Recurrent Germline DLST Mutations in Individuals with Multiple Pheochromocytomas and Paragangliomas

SLC25A11, a Novel Gene Associated With Carney-Stratakis Syndrome

Background

Carney-Stratakis syndrome (CSS), a rare condition characterized by paragangliomas and/or pheochromocytomas and gastrointestinal stromal tumors (GIST), is caused by germline heterozygous pathogenic variants in the succinate dehydrogenase subunit genes (SDHB, SDHC, SDHD).

Methods

Histological, genetic, and functional analyses were conducted in a 59-year-old female with CSS (9 cm left pheochromocytoma, 4.8 cm paraganglioma, and 9.3 cm GIST). Whole-exome sequencing (WES) of germline DNA paired with tumor DNA was performed.

Results

WES identified a rare heterozygous germline variant (c.293G>A/p.Arg98His) in the mitochondrial 2-oxoglutarate/malate carrier gene (SLC25A11). This variant, located in a highly conserved residue of the SLC25A11 mitochondrial carrier domain, is predicted to be deleterious in silico (REVEL score = 0.81). WES of pheochromocytoma, paraganglioma, and GIST did not reveal somatic pathogenic variants in genes previously associated with these tumors. A significant reduction in SLC25A11 expression was observed in the tumors of this patient with the SLC25A11 c.293G>A variant (0.69 ± 0.003) compared to tumors from cluster 1 (1.39 ± 0.45; P = 0.0229) and cluster 2 (1.79 ± 0.71; P = .0154). Consistent with the mRNA findings, SLC25A11 protein levels were markedly reduced in the pheochromocytoma and paraganglioma compared to other tumors. Negative staining for 5-hydroxymethylcytosine in all 3 tumors suggests a DNA hypermethylation profile characteristic of cluster 1A, despite normal SDHB expression levels. However, genome-wide copy number variation analysis did not reveal any loss of heterozygosity at the SLC25A11 locus.

Conclusion

The loss of SLC25A11 expression in tumors, the absence of somatic drivers, and the hypermethylation status strongly support the role of SLC25A11 in CSS pathogenesis.

Screening and validating genes associated with cuproptosis in systemic lupus erythematosus by expression profiling combined with machine learning

Cell death has long been a focal point in life sciences research, and recently, scientists have discovered a novel form of cell death induced by copper, termed cuproptosis. This paper aimed to identify genes associated with cuproptosis in systemic lupus erythematosus (SLE) through machine learning, combined with single-cell RNA sequencing (scRNA-seq), to screen and validate related genes. The analytical results were then experimentally verified. Two published microarray gene expression datasets (GSE65391 and GSE61635) from SLE and control peripheral blood samples were downloaded from the GEO database. The GSE65391 dataset was used as the training group, while the GSE61635 dataset served as the validation group. Differentially expressed genes from GSE65391 identified 12 differential genes. Nine diagnostic genes, considered potential biomarkers, were selected using the least absolute shrinkage and selection operator and support vector machine recursive feature elimination analysis. The receiver operating characteristic (ROC) curves for both the training and validation groups were used to calculate the area under the curve to assess discriminatory properties. CIBERSORT was used to assess the relationship between these diagnostic genes and a reference set of infiltrating immune cells. scRNA-seq data (GSE162577) from SLE patients were also obtained from the GEO database and analyzed. Experimental validation of the most important SLE biomarkers was performed. Twelve significantly different cuproptosis-related genes were identified in the GSE65391 training set. Immune cell analysis revealed 12 immune cell types and identified nine signature genes, including PDHB, glutaminase (GLS), DLAT, LIAS, MTF1, DLST, DLD, LIPT1, and FDX1. In the GSE61635 validation set, seven genes were weakly expressed, and two genes were strongly expressed in the treatment group. According to the ROC curves, PDHB and GLS demonstrated significant diagnostic value. Additionally, correlation analysis was conducted on the nine characteristic genes in relation to immune infiltration. The distribution of key genes in immune cells was determined using scRNA-seq data. Finally, the mRNA expression of the nine diagnostic genes was validated using qPCR.

MAML3-fusions modulate vascular and immune tumour microenvironment and confer high metastatic risk in pheochromocytoma and paraganglioma

Pheochromocytomas and paragangliomas are rare neuroendocrine tumours. Around 20-25 % of patients develop metastases, for which there is an urgent need of prognostic markers and therapeutic stratification strategies. The presence of a MAML3-fusion is associated with increased metastatic risk, but neither the processes underlying disease progression, nor targetable vulnerabilities have been addressed. We have compiled a cohort of 850 patients, which has shown a 3.65 % fusion prevalence and represents the largest MAML3-positive series reported to date. While MAML3-fusions mainly cause single pheochromocytomas, we also observed somatic post-zygotic events, resulting in multiple tumours in the same patient. MAML3-tumours show increased expression of neuroendocrine-to-mesenchymal transition markers, MYC-targets, and angiogenesis-related genes, leading to a distinct tumour microenvironment with unique vascular and immune profiles. Importantly, our findings have identified MAML3-tumours specific vulnerabilities beyond Wnt-pathway dysregulation, such as a rich vascular network, and overexpression of PD-L1 and CD40, suggesting potential therapeutic targets.

Recent progress in molecular classification of phaeochromocytoma and paraganglioma

Phaeochromocytomas (PC) and paragangliomas (PG) are neural crest cancers with high heritability. Recent advances in molecular profiling, including multi-omics and single cell genomics has identified up to seven distinct molecular subtypes. These subtypes are defined by mutations involving hypoxia-inducible factors (HIFs), Krebs cycle, kinase and WNT signalling, but are also defined by chromaffin differentiation states. PCPG have a dominant proangiogenic microenvironment linked to HIF pathway activity and are generally considered "immune cold" tumours with a high number of macrophages. PCPG subtypes can indicate increased metastatic risk but secondary mutations in telomere maintenance genes TERT or ATRX are required to drive the metastatic phenotype. Molecular profiling can identify molecular therapeutic (e.g. RET and EPAS1) and radiopharmaceutical targets while also helping to support variant pathogenicity and familial risk. Molecular profiling and subtyping of PCPG therefore confers the possibility of nuanced prognostication and individual treatment stratification but this still requires large-scale prospective validation.

Long-telomeropathy is associated with tumor predisposition syndrome

Telomeres protect chromosomal integrity, and telomere length (TL) is influenced by environmental and genetic factors. While short-telomeres are linked to rare telomeropathies, this study explored the hypothesis that a "long-telomeropathy" is associated with a cancer-predisposing syndrome. Using genomic and health data from 113,861 individuals, a trans-ancestry polygenic risk score for TL (PRS TL ) was developed. A phenome-wide association study (PheWAS) identified 65 tumor traits linked to elevated PRS TL . Using this result, a trans-ancestry phenotype risk score for a long-TL (PheRS LTL ) was develop and validated. Rare variant analyses revealed 13 genes associated with PheRS LTL . Individuals who were carriers of these rare variants had a predisposition for long-TL validating original hypothesis. Most of these genes were new to both cancer and telomere biology. In conclusion, this study identified a novel tumor-predisposing syndrome shaped by both common and rare genetic variants, broadening the understanding of telomeropathies to those with a predisposition for long telomeres.

Non-Susceptibility Gene Variants in Head and Neck Paragangliomas

Head and neck paragangliomas (HNPGLs) are rare neoplasms that, along with pheochromocytomas and extra-adrenal paragangliomas, are associated with inherited mutations in at least 12 susceptibility genes in approximately 40% of cases. However, due to the rarity of HNPGLs, only a series of small-scale studies and individual cases have reported mutations in additional genes that may be involved in tumorigenesis. Consequently, numerous disease-causing mutations and genes responsible for the pathogenesis of HNPGLs remain poorly investigated. The aim of this study was to gain a deeper understanding of the genetic basis of HNPGLs by focusing on variants in genes that were not previously identified as well-known drivers. A whole-exome data analysis was conducted on a representative set of 152 HNPGLs. In 30% of the tumors examined, 53 potentially deleterious variants were identified in 36 different genes. The analysis identified pathogenic or likely pathogenic variants in the ARNT, IDH2, L2HGDH, MYH3, PIK3CA, and TERT genes. A functional network analysis of the mutated genes revealed numerous associations and a list of metabolic pathways (e.g., the TCA cycle, carbon metabolism, pyruvate metabolism, etc.) and signaling pathways (e.g., HIF1, PI3K-Akt, FoxO, AMPK, MAPK, etc.) that may play an important role in the development of HNPGLs. The identified range of genetic alterations affecting multiple genes and, potentially, influencing diverse cellular pathways provides an enhanced molecular genetic characterization of HNPGLs.

Clinical and molecular markers guide the genetics of pheochromocytoma and paraganglioma

Over the past two decades, research into the genetic susceptibility behind pheochromocytoma and paraganglioma (PPGL) has surged, ranking them among the most heritable tumors. Massive sequencing combined with careful patient selection has so far identified more than twenty susceptibility genes, leading to an over-detection of variants of unknown significance (VUS) that require precise molecular markers to determine their pathogenic role. Moreover, some PPGL patients remain undiagnosed, possibly due to mutations in regulatory regions of already known genes or mutations in undiscovered genes. Accurate classification of VUS and identification of new genes require well-defined clinical and molecular markers that allow effective genetic diagnosis of most PPGLs.

A Systematic Review of Proteomics in Obesity: Unpacking the Molecular Puzzle

PURPOSE OF REVIEW

The present study aims to review the existing literature to identify pathophysiological proteins in obesity by conducting a systematic review of proteomics studies. Proteomics may reveal the mechanisms of obesity development and clarify the links between obesity and related diseases, improving our comprehension of obesity and its clinical implications.

RECENT FINDINGS

Most of the molecular events implicated in obesity development remain incomplete. Proteomics stands as a powerful tool for elucidating the intricate interactions among proteins in the context of obesity. This methodology has the potential to identify proteins involved in pathological processes and to evaluate changes in protein abundance during obesity development, contributing to the identification of early disease predisposition, monitoring the effectiveness of interventions and improving disease management overall. Despite many non-targeted proteomic studies exploring obesity, a comprehensive and up-to-date systematic review of the molecular events implicated in obesity development is lacking. The lack of such a review presents a significant challenge for researchers trying to interpret the existing literature. This systematic review was conducted following the PRISMA guidelines and included sixteen human proteomic studies, each of which delineated proteins exhibiting significant alterations in obesity. A total of 41 proteins were reported to be altered in obesity by at least two or more studies. These proteins were involved in metabolic pathways, oxidative stress responses, inflammatory processes, protein folding, coagulation, as well as structure/cytoskeleton. Many of the identified proteomic biomarkers of obesity have also been reported to be dysregulated in obesity-related disease. Among them, seven proteins, which belong to metabolic pathways (aldehyde dehydrogenase and apolipoprotein A1), the chaperone family (albumin, heat shock protein beta 1, protein disulfide-isomerase A3) and oxidative stress and inflammation proteins (catalase and complement C3), could potentially serve as biomarkers for the progression of obesity and the development of comorbidities, contributing to personalized medicine in the field of obesity. Our systematic review in proteomics represents a substantial step forward in unravelling the complexities of protein alterations associated with obesity. It provides valuable insights into the pathophysiological mechanisms underlying obesity, thereby opening avenues for the discovery of potential biomarkers and the development of personalized medicine in obesity.

Case report: A rare DLST mutation in patient with metastatic pheochromocytoma: clinical implications and management challenges

Background

Pheochromocytoma is one of the most hereditary human tumors with at least 20 susceptible genes undergoing germline and somatic mutations, and other mutations less than 1% -2%. In recent years, other rare mutations have gradually been discovered to be possibly related to the pathogenesis and metastasis of pheochromocytoma. Most patients with pheochromocytoma experience common symptoms like headaches, palpitations, and sweating, while some may have less common symptoms. The diversity of symptoms, genetic mutations, and limited treatment options make management challenging.

Case presentation

A 53-year-old woman was hospitalized after experiencing episodic epigastric pain for one month. A mass was found in her right adrenal gland and she underwent robot-assisted laparoscopic surgery, revealing a pheochromocytoma. At the 16-month follow-up, multiple metastatic lesions consistent with metastatic pheochromocytoma were found. A germline mutation in the dihydrolipoamide succinyltransferase (DLST) gene (c.330 + 14A>G) was detected, and despite trying chemotherapy and adjuvant therapy, the patient had a limited response with an overall survival of 27 months.

Conclusions

DLST mutation is one of the rare pheochromocytoma-related mutated genes, and genetic sequencing is crucial for effective clinical management.

Hypoxia-inducible factor in cancer: from pathway regulation to therapeutic opportunity

Cancer remains one of the most formidable challenges in modern medicine, due to its complex and dynamic nature, which demands innovative therapeutic approaches. One major challenge to cancer treatment is the tumour microenvironment and in particular tumour hypoxia (low oxygen levels), which contributes to tumour progression and immune evasion. At the cellular level, this is primarily governed by hypoxia-inducible factor (HIF). HIF is a transcription factor that orchestrates cellular responses to low oxygen levels, driving angiogenesis, metabolic adaptation and immune regulation. HIF's dysregulation is frequently observed in various cancer types and correlates with increased aggressiveness, metastasis, resistance to therapy and poor patient prognosis. Consequently, understanding the cellular mechanisms underlying HIF activation and its downstream effects has become crucial to developing targeted cancer therapies for improving cancer patient outcomes and represents a key step towards precision medicine. Recent advancements in drug development have led to the emergence of HIF inhibitors, which aim to disrupt HIF-driven processes in cancer providing therapeutic benefit. Here, we provide a review of the molecular mechanisms through which HIF promotes tumour growth and resistance, emphasising the potential clinical benefits of HIF-targeted therapies. This review will discuss the challenges and opportunities associated with translating HIF inhibition into clinical practice, including ongoing clinical trials and future directions in the development of HIF-based cancer treatments.

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.

Identification of a novel cuproptosis-related gene signature for multiple myeloma diagnosis

BACKGROUND

Multiple myeloma (MM) ranks second among the most prevalent hematological malignancies. Recent studies have unearthed the promise of cuproptosis as a novel therapeutic intervention for cancer. However, no research has unveiled the particular roles of cuproptosis-related genes (CRGs) in the prediction of MM diagnosis.

METHODS

Microarray data and clinical characteristics of MM patients were obtained from the Gene Expression Omnibus (GEO) database. Differentially expressed gene analysis, least absolute shrinkage and selection operator (LASSO) and support vector machine-recursive feature elimination (SVM-RFE) algorithms were applied to identify potential signature genes for MM diagnosis. Predictive performance was further assessed by receiver operating characteristic (ROC) curves, nomogram analysis, and external data sets. Functional enrichment analysis was performed to elucidate the involved mechanisms. Finally, the expression of the identified genes was validated by quantitative real-time polymerase chain reaction (qRT-PCR) in MM cell samples.

RESULTS

The optimal gene signature was identified using LASSO and SVM-RFE algorithms based on the differentially expressed CRGs: ATP7A, FDX1, PDHA1, PDHB, MTF1, CDKN2A, and DLST. Our gene signature-based nomogram revealed a high degree of accuracy in predicting MM diagnosis. ROC curves showed the signature had dependable predictive ability across all data sets, with area under the curve values exceeding 0.80. Additionally, functional enrichment analysis suggested significant associations between the signature genes and immune-related pathways. The expression of the genes was validated in MM cells, indicating the robustness of these findings.

CONCLUSION

We discovered and validated a novel CRG signature with strong predictive capability for diagnosing MM, potentially implicated in MM pathogenesis and progression through immune-related pathways.

Exosome Liberation by Human Neutrophils under L-Amino Acid Oxidase of Calloselasma rhodostoma Venom Action

L-Amino acid oxidase (LAAO) is an enzyme found in snake venom that has multifaceted effects, including the generation of hydrogen peroxide (H2O2) during oxidative reactions, leading to various biological and pharmacological outcomes such as apoptosis, cytotoxicity, modulation of platelet aggregation, hemorrhage, and neutrophil activation. Human neutrophils respond to LAAO by enhancing chemotaxis, and phagocytosis, and releasing reactive oxygen species (ROS) and pro-inflammatory mediators. Exosomes cellular nanovesicles play vital roles in intercellular communication, including immune responses. This study investigates the impact of Calloselasma rhodostoma snake venom-derived LAAO (Cr-LAAO) on human neutrophil exosome release, including activation patterns, exosome formation, and content. Neutrophils isolated from healthy donors were stimulated with Cr-LAAO (100 μg/mL) for 3 h, followed by exosome isolation and analysis. Results show that Cr-LAAO induces the release of exosomes with distinct protein content compared to the negative control. Proteomic analysis reveals proteins related to the regulation of immune responses and blood coagulation. This study uncovers Cr-LAAO's ability to activate human neutrophils, leading to exosome release and facilitating intercellular communication, offering insights into potential therapeutic approaches for inflammatory and immunological disorders.

L-2hydroxyglutaric acid rewires amino acid metabolism in colorectal cancer via the mTOR-ATF4 axis

Oncometabolites, such as D/L-2-hydroxyglutarate (2HG), have directly been implicated in carcinogenesis; however, the underlying molecular mechanisms remain poorly understood. Here, we showed that the levels of the L-enantiomer of 2HG (L2HG) were specifically increased in colorectal cancer (CRC) tissues and cell lines compared with the D-enantiomer of 2HG (D2HG). In addition, L2HG increased the expression of ATF4 and its target genes by activating the mTOR pathway, which subsequently provided amino acids and improved the survival of CRC cells under serum deprivation. Downregulating the expression of L-2-hydroxyglutarate dehydrogenase (L2HGDH) and oxoglutarate dehydrogenase (OGDH) increased L2HG levels in CRC, thereby activating mTOR-ATF4 signaling. Furthermore, L2HGDH overexpression reduced L2HG-mediated mTOR-ATF4 signaling under hypoxia, whereas L2HGDH knockdown promoted tumor growth and amino acid metabolism in vivo. Together, these results indicate that L2HG ameliorates nutritional stress by activating the mTOR-ATF4 axis and thus could be a potential therapeutic target for CRC.

Co-occurrence of mutations in NF1 and other susceptibility genes in pheochromocytoma and paraganglioma

Introduction

The percentage of patients diagnosed with pheochromocytoma and paraganglioma (altogether PPGL) carrying known germline mutations in one of the over fifteen susceptibility genes identified to date has dramatically increased during the last two decades, accounting for up to 35-40% of PPGL patients. Moreover, the application of NGS to the diagnosis of PPGL detects unexpected co-occurrences of pathogenic allelic variants in different susceptibility genes.

Methods

Herein we uncover several cases with dual mutations in NF1 and other PPGL genes by targeted sequencing. We studied the molecular characteristics of the tumours with co-occurrent mutations, using omic tools to gain insight into the role of these events in tumour development.

Results

Amongst 23 patients carrying germline NF1 mutations, targeted sequencing revealed additional pathogenic germline variants in DLST (n=1) and MDH2 (n=2), and two somatic mutations in H3-3A and PRKAR1A. Three additional patients, with somatic mutations in NF1 were found carrying germline pathogenic mutations in SDHB or DLST, and a somatic truncating mutation in ATRX. Two of the cases with dual germline mutations showed multiple pheochromocytomas or extra-adrenal paragangliomas - an extremely rare clinical finding in NF1 patients. Transcriptional and methylation profiling and metabolite assessment showed an "intermediate signature" to suggest that both variants had a pathological role in tumour development.

Discussion

In conclusion, mutations affecting genes involved in different pathways (pseudohypoxic and receptor tyrosine kinase signalling) co-occurring in the same patient could provide a selective advantage for the development of PPGL, and explain the variable expressivity and incomplete penetrance observed in some patients.

Recurrent Disease in Patients With Sporadic Pheochromocytoma and Paraganglioma

CONTEXT

Long-term follow-up has been recommended for patients with pheochromocytoma or paraganglioma (PPGL) due to potential for recurrent disease. However, the need to follow patients with sporadic PPGL has recently become controversial.

OBJECTIVE

To investigate the prevalence of recurrence among patients with sporadic compared with hereditary PPGL and to identify predictors of recurrence for sporadic disease.

METHODS

This multicenter study included retrospective data from 1127 patients with PPGL. In addition to sex and age at primary tumor diagnosis, clinical information included location, size, and catecholamine phenotype of primary tumors, genetic test results, and subsequent development of recurrent and/or metastatic disease. Patients with sporadic PPGL were defined as those with negative genetic test results.

RESULTS

Prevalence of recurrence among patients with sporadic PPGL (14.7%) was lower (P < 0.001) than for patients with pathogenic variants that activate pseudohypoxia pathways (47.5%), but similar to those with variants that activate kinase pathways (14.9%). Among patients with sporadic recurrent PPGL, 29.1% and 17.7% were respectively diagnosed at least 10 and 15 years after first diagnosis. Multivariable regression analysis showed that a noradrenergic/dopaminergic phenotype (HR 2.73; 95% CI, 1.553-4.802; P < 0.001), larger size (HR 1.82; 95% CI, 1.113-2.962; P = 0.017) and extra-adrenal location (HR 1.79; 95% CI, 1.002-3.187; P = 0.049) of primary tumors were independent predictors of recurrence in sporadic PPGL.

CONCLUSION

Patients with sporadic PPGL require long-term follow-up, as supported by the 14.7% prevalence of recurrent disease, including recurrences at more than 10 years after first diagnosis. The nature of follow-up could be individualized according to tumor size, location, and biochemical phenotype.

Nuclear and mitochondrial DNA alterations in pheochromocytomas and paragangliomas, and their potential treatment

Mitochondrial DNA (mtDNA) alterations have been reported in different types of cancers and are suggested to play important roles in cancer development and metastasis. However, there is little information about its involvement in pheochromocytomas and paragangliomas (PCCs/PGLs) formation. PCCs and PGLs are rare endocrine tumors of the chromaffin cells in the adrenal medulla and extra-adrenal paraganglia that can synthesize and secrete catecholamines. Over the last 3 decades, the genetic background of about 60% of PCCs/PGLs involving nuclear DNA alterations has been determined. Recently, a study showed that mitochondrial alterations can be found in around 17% of the remaining PCCs/PGLs. In this review, we summarize recent knowledge regarding both nuclear and mitochondrial alterations and their involvement in PCCs/PGLs. We also provide brief insights into the genetics and the molecular pathways associated with PCCs/PGLs and potential therapeutical targets.

Tumour microenvironment in pheochromocytoma and paraganglioma

Pheochromocytomas and Paragangliomas (Pheo/PGL) are rare catecholamine-producing tumours derived from adrenal medulla or from the extra-adrenal paraganglia respectively. Around 10-15% of Pheo/PGL develop metastatic forms and have a poor prognosis with a 37% of mortality rate at 5 years. These tumours have a strong genetic determinism, and the presence of succinate dehydrogenase B (SDHB) mutations are highly associated with metastatic forms. To date, no effective treatment is present for metastatic forms. In addition to cancer cells, the tumour microenvironment (TME) is also composed of non-neoplastic cells and non-cellular components, which are essential for tumour initiation and progression in multiple cancers, including Pheo/PGL. This review, for the first time, provides an overview of the roles of TME cells such as cancer-associated fibroblasts (CAFs) and tumour-associated macrophages (TAMs) on Pheo/PGL growth and progression. Moreover, the functions of the non-cellular components of the TME, among which the most representatives are growth factors, extracellular vesicles and extracellular matrix (ECM) are explored. The importance of succinate as an oncometabolite is emerging and since Pheo/PGL SDH mutated accumulate high levels of succinate, the role of succinate and of its receptor (SUCNR1) in the modulation of the carcinogenesis process is also analysed. Further understanding of the mechanism behind the complicated effects of TME on Pheo/PGL growth and spread could suggest novel therapeutic targets for further clinical treatments.

Advances in Adrenal and Extra-adrenal Paraganglioma: Practical Synopsis for Pathologists

Adrenal paraganglioma (or "pheochromocytoma") and extra-adrenal paraganglioma, collectively abbreviated PPGL, are rare but spectacular nonepithelial neuroendocrine neoplasms. These are the most inheritable neoplasia of all, with a metastatic potential in a varying degree. As of such, these lesions demand careful histologic, immunohistochemical, and genetic characterization to provide the clinical team with a detailed report taking into account the anticipated prognosis and risk of syndromic/inherited disease. While no histologic algorithm, immunohistochemical biomarker, or molecular aberration single-handedly can identify potentially lethal cases upfront, the combined analysis of various risk parameters may stratify PPGL patients more stringently than previously. Moreover, the novel 2022 WHO Classification of Endocrine and Neuroendocrine Tumors also brings some new concepts into play, not least the reclassification of special neuroendocrine neoplasms (cauda equina neuroendocrine tumor and composite gangliocytoma/neuroma-neuroendocrine tumor) previously thought to belong to the spectrum of PPGL. This review focuses on updated key diagnostic and prognostic concepts that will aid when facing this rather enigmatic tumor entity in clinical practice.

SDHB and SDHD silenced pheochromocytoma spheroids respond differently to tumour microenvironment and their aggressiveness is inhibited by impairing stroma metabolism

Germline mutations in more than 20 genes, including those encoding for the succinate dehydrogenase (SDH), predispose to rare tumours, such as pheochromocytoma/paraganglioma (PPGL). Despite encoding for the same enzymatic complex, SDHC and SDHD mutated PHEO/PGLs are generally benign, while up to 80% of SDHB mutated ones are malignant. In this study, we evaluated the different effects of tumour microenvironment on tumour cell migration/invasion, by co-culturing SDHB or SDHD silenced tumour spheroids with primary cancer-associated fibroblasts (CAFs). We observed that SDHD silenced spheroids had an intermediate migration pattern, compared to the highest migration capability of SDHB and the lowest one of the wild type (Wt) spheroids. Interestingly, we noticed that co-culturing Wt, SDHB and SDHD silenced spheroids with CAFs in low glucose (1 g/l) medium, caused a decreased migration of all the spheroids, but only for SDHB silenced ones this reduction was significant. Moreover, the collective migration, observed in high glucose (4.5 g/l) and characteristic of the SDHB silenced cells, was completely lost in low glucose. Importantly, migration could not be recovered even adding glucose (3.5 g/l) to low glucose conditioned medium. When we investigated cell metabolism, we found that low glucose concentration led to a reduction of oxygen consumption rate (OCR), basal and maximal oxidative metabolism, and ATP production only in CAFs, but not in tumour cells. These results suggest that CAFs metabolism impairment was responsible for the decreased invasion process of tumour cells, most likely preventing the release of the pro-migratory factors produced by CAFs. In conclusion, the interplay between CAFs and tumour cells is distinctive depending on the gene involved, and highlights the possibility to inhibit CAF-induced migration by impairing CAFs metabolism, indicating new potential therapeutic scenarios for medical therapy.

Targeting 2-oxoglutarate dehydrogenase for cancer treatment

Tricarboxylic acid (TCA) cycle, also called Krebs cycle or citric acid cycle, is an amphoteric pathway, contributing to catabolic degradation and anaplerotic reactions to supply precursors for macromolecule biosynthesis. Oxoglutarate dehydrogenase complex (OGDHc, also called α-ketoglutarate dehydrogenase) a highly regulated enzyme in TCA cycle, converts α-ketoglutarate (αKG) to succinyl-Coenzyme A in accompany with NADH generation for ATP generation through oxidative phosphorylation. The step collaborates with glutaminolysis at an intersectional point to govern αKG levels for energy production, nucleotide and amino acid syntheses, and the resources for macromolecule synthesis in cancer cells with rapid proliferation. Despite being a flavoenzyme susceptible to electron leakage contributing to mitochondrial reactive oxygen species (ROS) production, OGDHc is highly sensitive to peroxides such as HNE (4-hydroxy-2-nonenal) and moreover, its activity mediates the activation of several antioxidant pathways. The characteristics endow OGDHc as a critical redox sensor in mitochondria. Accumulating evidences suggest that dysregulation of OGDHc impairs cellular redox homeostasis and disturbs substrate fluxes, leading to a buildup of oncometabolites along the pathogenesis and development of cancers. In this review, we describe molecular interactions, regulation of OGDHc expression and activity and its relationships with diseases, specifically focusing on cancers. In the end, we discuss the potential of OGDHs as a therapeutic target for cancer treatment.

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.

Retroperitoneal Paraganglioma With Asymptomatic Follicular Lymphoma: A Case Report

Paraganglioma (PGL) is a rare tumor originating from extra-adrenal paraganglionic chromaffin tissues, and most sympathetic PGLs have excessive catecholamine secretion. However, nonfunctional PGLs are sometimes found. Although malignant PGL is defined by metastasis to nonchromaffin tissues, it is difficult to predict malignancies due to the lack of reliable markers of potential malignancies. We report the case of a 69-year-old Japanese woman with an incidental retroperitoneal tumor and multiple enlarged mesenteric lymph nodes simultaneously. The patient had no subjective symptoms and there were no laboratory findings suggesting catecholamine hypersecretion. Both the retroperitoneal tumor and the enlarged mesenteric lymph nodes showed high accumulation of fluorodeoxyglucose (FDG), whereas metaiodobenzylguanidine (MIBG) was accumulated only at the retroperitoneal tumor. Although a retroperitoneal tumor was diagnosed as nonfunctional PGL by examination including MIBG scintigraphy, the cause of enlarged mesenteric lymph nodes could not be diagnosed by imaging and biochemical tests. As a result of retroperitoneal tumor resection and mesenteric lymph nodes sampling, histopathological examination revealed that a retroperitoneal tumor was PGL and enlarged mesenteric lymph nodes were follicular lymphoma. To reveal an underlying genetic factor, we performed whole exome sequencing of genomic DNA, and we identified 2 possible candidate variants in SDHD and DLST, but the pathogenicity of these variants remains uncertain in the present case. This rare case reinforces the importance of histopathological diagnosis of nonchromaffin tissue lesions in patients with PGL for the appropriate treatment strategy.

Analysis of Telomere Maintenance Related Genes Reveals NOP10 as a New Metastatic-Risk Marker in Pheochromocytoma/Paraganglioma

Simple Summary

Telomere maintenance involving TERT and ATRX genes has been recently described in metastatic pheochromocytoma and paraganglioma, reinforcing the importance of immortalization mechanisms in the progression of these tumors. Thus, the aim of this study was to analyze additional telomere-related genes to uncover potential new markers capable of identifying metastatic-risk patients more accurately. After analyzing 29 telomere-related genes, we were able to validate the predictive value of TERT and ATRX in mPPGL progression. In addition, we were able to identify NOP10 as a novel prognostic risk marker of mPPGLs, which also facilitates telomerase-dependent telomere length maintenance in these tumors. Interestingly, NOP10 overexpression assessment by IHC could be easily included within the current battery of markers for stratifying PPGL patients to fine-tune their clinical diagnoses.

Abstract

One of the main problems we face with PPGL is the lack of molecular markers capable of predicting the development of metastases in patients. Telomere-related genes, such as TERT and ATRX, have been recently described in PPGL, supporting the association between the activation of immortalization mechanisms and disease progression. However, the contribution of other genes involving telomere preservation machinery has not been previously investigated. In this work, we aimed to analyze the prognostic value of a comprehensive set of genes involved in telomere maintenance. For this study, we collected 165 PPGL samples (97 non-metastatic/63 metastatic), genetically characterized, in which the expression of 29 genes of interest was studied by NGS. Three of the 29 genes studied, TERT, ATRX and NOP10, showed differential expression between metastatic and non-metastatic cases, and alterations in these genes were associated with a shorter time to progression, independent of SDHB-status. We studied telomere length by Q-FISH in patient samples and in an in vitro model. NOP10 overexpressing tumors displayed an intermediate-length telomere phenotype without ALT, and in vitro results suggest that NOP10 has a role in telomerase-dependent telomere maintenance. We also propose the implementation of NOP10 IHC to better stratify PPGL patients.

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.

Significance of Alpha-inhibin Expression in Pheochromocytomas and Paragangliomas

Alpha-inhibin expression has been reported in pheochromocytomas and paragangliomas (PPGLs). We analyzed alpha-inhibin immunohistochemistry in 77 PPGLs (37 pheochromocytomas [PCCs] and 40 paragangliomas) and correlated the results with catecholamine profile, tumor size, Ki-67 labeling index, succinate dehydrogenase B subunit and carbonic anhydrase IX (CAIX) staining, and genetic pathogenesis. PPGLs were classified as pseudohypoxic cluster 1 disease with documented VHL mutation or SDHx mutation or biochemical phenotype, whereas NF1-driven and RET-driven PPGLs and those with a mature secretory (adrenergic or mixed adrenergic and noradrenergic) phenotype were classified as cluster 2 disease. The Cancer Genome Atlas data on INHA expression in PPGLs was examined. Alpha-inhibin was positive in 43 PPGLs (56%). Ki-67 labeling indices were 8.07% and 4.43% in inhibin-positive and inhibin-negative PPGLs, respectively (P<0.05). Alpha-inhibin expression did not correlate with tumor size. Alpha-inhibin was expressed in 92% of SDHx-related and 86% of VHL-related PPGLs. CAIX membranous staining was found in 8 of 51 (16%) tumors, including 1 SDHx-related PCC and all 5 VHL-related PCCs. NF1-driven and RET-driven PPGLs were negative for alpha-inhibin and CAIX. Alpha-inhibin was expressed in 77% of PPGLs with a pseudohypoxia signature, and 20% of PPGLs without a pseudohypoxia signature (P<0.05). PPGLs with a mature secretory phenotype were negative for CAIX. The Cancer Genome Atlas data confirmed higher expression of INHA in cluster 1 than in cluster 2 PPGLs. This study identifies alpha-inhibin as a highly sensitive (90.3%) marker for SDHx/VHL-driven pseudohypoxic PPGLs. Although CAIX has low sensitivity, it is the most specific biomarker of VHL-related pathogenesis. While alpha-inhibin cannot replace succinate dehydrogenase B subunit immunohistochemistry for detection of SDHx-related disease, it adds value in prediction of cluster 1 disease. Importantly, these data emphasize that alpha-inhibin is not a specific marker of adrenal cortical differentiation, as it is also expressed in PCCs.

Genetic stratification of inherited and sporadic phaeochromocytoma and paraganglioma: implications for precision medicine

Over the past two decades advances in genomic technologies have transformed knowledge of the genetic basis of phaeochromocytoma and paraganglioma (PPGL). Though traditional teaching suggested that inherited cases accounted for only 10% of all phaeochromocytoma diagnosis, current estimates are at least three times this proportion. Inherited PPGL is a highly genetically heterogeneous disorder but the most frequently results from inactivating variants in genes encoding subunits of succinate dehydrogenase. Expanding knowledge of the genetics of PPGL has been translated into clinical practice by the provision of widespread testing for inherited PPGL. In this review, we explore how the molecular stratification of PPGL is being utilized to enable more personalized strategies for investigation, surveillance and management of affected individuals and their families. Translating recent genetic research advances into clinical service can not only bring benefits through more accurate diagnosis and risk prediction but also challenges when there is a suboptimal evidence base for the clinical consequences or significance of rare genotypes. In such cases, clinical, biochemical, pathological and functional imaging assessments can all contribute to more accurate interpretation and clinical management.

Metabolic Enzyme DLST Promotes Tumor Aggression and Reveals a Vulnerability to OXPHOS Inhibition in High-Risk Neuroblastoma

High-risk neuroblastoma remains therapeutically challenging to treat, and the mechanisms promoting disease aggression are poorly understood. Here, we show that elevated expression of dihydrolipoamide S-succinyltransferase (DLST) predicts poor treatment outcome and aggressive disease in patients with neuroblastoma. DLST is an E2 component of the α-ketoglutarate (αKG) dehydrogenase complex, which governs the entry of glutamine into the tricarboxylic acid cycle (TCA) for oxidative decarboxylation. During this irreversible step, αKG is converted into succinyl-CoA, producing NADH for oxidative phosphorylation (OXPHOS). Utilizing a zebrafish model of MYCN-driven neuroblastoma, we demonstrate that even modest increases in DLST expression promote tumor aggression, while monoallelic dlst loss impedes disease initiation and progression. DLST depletion in human MYCN-amplified neuroblastoma cells minimally affected glutamine anaplerosis and did not alter TCA cycle metabolites other than αKG. However, DLST loss significantly suppressed NADH production and impaired OXPHOS, leading to growth arrest and apoptosis of neuroblastoma cells. In addition, multiple inhibitors targeting the electron transport chain, including the potent IACS-010759 that is currently in clinical testing for other cancers, efficiently reduced neuroblastoma proliferation in vitro. IACS-010759 also suppressed tumor growth in zebrafish and mouse xenograft models of high-risk neuroblastoma. Together, these results demonstrate that DLST promotes neuroblastoma aggression and unveils OXPHOS as an essential contributor to high-risk neuroblastoma. SIGNIFICANCE: These findings demonstrate a novel role for DLST in neuroblastoma aggression and identify the OXPHOS inhibitor IACS-010759 as a potential therapeutic strategy for this deadly disease.

Genetic approaches to understand cellular responses to oxygen availability

Oxygen-sensing mechanisms have evolved to allow organisms to respond and adapt to oxygen availability. In metazoans, oxygen-sensing is predominantly mediated by the hypoxia inducible factors (HIFs). These transcription factors are stabilised when oxygen is limiting, activating genes involved in angiogenesis, cell growth, pH regulation and metabolism to reset cell function and adapt to the cellular environment. However, the recognition that other cellular pathways and enzymes can also respond to changes in oxygen abundance provides further complexity. Dissecting this interplay of oxygen-sensing mechanisms has been a key research goal. Here, we review how genetic approaches have contributed to our knowledge of oxygen-sensing pathways which to date have been predominantly focused on the HIF pathway. We discuss how genetic studies have advanced the field and outline the implications and limitations of such approaches for the development of therapies targeting oxygen-sensing mechanisms in human disease.

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.

Metastatic Pheochromocytomas and Abdominal Paragangliomas

CONTEXT

Pheochromocytomas and paragangliomas (PPGLs) are believed to harbor malignant potential; about 10% to 15% of pheochromocytomas and up to 50% of abdominal paragangliomas will exhibit metastatic behavior.

EVIDENCE ACQUISITION

Extensive searches in the PubMed database with various combinations of the key words pheochromocytoma, paraganglioma, metastatic, malignant, diagnosis, pathology, genetic, and treatment were the basis for the present review.

DATA SYNTHESIS

To pinpoint metastatic potential in PPGLs is difficult, but nevertheless crucial for the individual patient to receive tailor-made follow-up and adjuvant treatment following primary surgery. A combination of histological workup and molecular predictive markers can possibly aid the clinicians in this aspect. Most patients with PPGLs have localized disease and may be cured by surgery. Plasma metanephrines are the main biochemical tests. Genetic testing is important, both for counseling and prognostic estimation. Apart from computed tomography and magnetic resonance imaging, molecular imaging using 68Ga-DOTATOC/DOTATATE should be performed. 123I-MIBG scintigraphy may be performed to determine whether 131I-MIBG therapy is a possible option. As first-line treatment in patients with metastatic disease, 177Lu-DOTATATE or 131I-MIBG is recommended, depending on which shows best expression. In patients with very low proliferative activity, watch-and-wait or primary treatment with long-acting somatostatin analogues may be considered. As second-line treatment, or first-line in patients with high proliferative rate, chemotherapy with temozolomide or cyclophosphamide + vincristine + dacarbazine is the therapy of choice. Other therapies, including sunitinib, cabozantinib, everolimus, and PD-1/PDL-1 inhibitors, have shown modest effect.

CONCLUSIONS

Metastatic PPGLs need individualized management and should always be discussed in specialized and interdisciplinary tumor boards. Further studies and newer treatment modalities are urgently needed.

The North American Neuroendocrine Tumor Society Consensus Guidelines for Surveillance and Management of Metastatic and/or Unresectable Pheochromocytoma and Paraganglioma

ABSTRACT

This manuscript is the result of the North American Neuroendocrine Tumor Society consensus conference on the medical management and surveillance of metastatic and unresectable pheochromocytoma and paraganglioma held on October 2 and 3, 2019. The panelists consisted of endocrinologists, medical oncologists, surgeons, radiologists/nuclear medicine physicians, nephrologists, pathologists, and radiation oncologists. The panelists performed a literature review on a series of questions regarding the medical management of metastatic and unresectable pheochromocytoma and paraganglioma as well as questions regarding surveillance after resection. The panelists voted on controversial topics, and final recommendations were sent to all panel members for final approval.

Recurrent Germline Mutations of CHEK2 as a New Susceptibility Gene in Patients with Pheochromocytomas and Paragangliomas

PURPOSE

Recently, pheochromocytomas and paragangliomas (PPGLs) have been strongly suspected as hereditary tumors, as approximately 40% of patients carry germline mutations. In the cancers where defects occur to corrupt DNA repair and facilitate tumorigenesis, a CHEK2 strong association has been observed. Therefore, the purpose of this study was to investigate the effect of CHEK2 mutations for its possible pathogenicity in PPGLs.

METHODS

Four patients with CHEK2 mutations were recruited, as previously detected by the whole exome sequencing. Sanger sequencing was used to verify the germline mutations as well as the loss of heterozygosities (LOHs) in their somatic DNAs. Immunohistochemistry was used to analyze the expression of CHEK2 and its downstream target p53 Ser20 (phosphorylated p53).

RESULTS

The average age of studied patients was 44.25 ± 11.18 years, at the time diagnosis. One patient had multiple tumors which recurred quickly, while two patients had distant metastasis. None of the patient had any relevant family history. Four germline CHEK2 mutations were identified (c.246_260del; c.715G > A; c.1008+3A > T; and c.1111C > T). All the patients were predicted to have either pathogenic or suspected pathogenic mutations. There was no LOH of CHEK2 gene in somatic DNAs found. Additionally, neither CHEK2 proteins nor its downstream target p53 Ser20 were expressed in the tumor tissues. The inactivation of CHEK2 leads to the decrease in the p53 phosphorylation, which might promote tumorigenesis.

CONCLUSIONS

For the first time, CHEK2 was identified as a susceptibility gene for PPGLs. However, the penetrance of CHEK2 gene with genotype-phenotype correlation needs to be investigated.

An update on adult forms of hereditary pheochromocytomas and paragangliomas

PURPOSE OF REVIEW

Pheochromocytomas and paragangliomas (PPGL) display a strong genetic determinism with 40% of inherited forms. The purpose of this review is to provide an update on current knowledge on adult forms of hereditary PPGL and their management.

RECENT FINDINGS

PPGL are genetically-driven in 70% of cases, with germline and/or somatic mutations identified in more than 20 genes. Although eight new susceptibility genes have recently emerged, mutations on SDHx genes remain the most frequent. In addition to SDHB, mutations in SLC25A11, FH and MDH2 may predispose to a metastatic disease and somatic alterations including TERT and ATRX mutations, and the differential expression on noncoding RNAs are also associated with the occurrence of metastases.The biochemical diagnosis remains the mainstay of functional PPGL and does not differ between hereditary PPGL while the choice of the best nuclear imaging approach is dictated by the tumor type and can be influenced by the presence of a germline mutation (18F-DOPA PET/CT for cluster 2 mutation and Ga-DOTATATE PET/CT for cluster 1 mutation).

SUMMARY

A systematic genetic testing and counselling is recommended for all PPGL patients and should lead to conservative surgery and an adapted follow up, in case of hereditary form.

Novel DNMT3A Germline Variant in a Patient with Multiple Paragangliomas and Papillary Thyroid Carcinoma

Simple Summary

The use of next generation technologies has helped to unravel the genetics of rare inherited diseases, facilitating the discovery of new susceptibility genes. Nonetheless, the sequencing of all protein-coding genes of an individual may lead to doubtful assignments of causality for non-pathological variants, so it is mandatory to perform comprehensive studies and screening of additional patients for new mutations. Here we describe a novel DNMT3A germline variant identified by whole-exome sequencing in a patient with multiple paragangliomas and papillary thyroid carcinoma. The increased methylation of DNMT3A target genes observed in the proband’s sample points towards a gain-of-function effect of the variant, contrasting with the inactivation caused by loss-of-function alterations commonly seen in other neoplasia and in patients with Tatton-Brown-Rahman syndrome. This finding stresses the diverse molecular outcomes and suggests a heterogeneous phenotypic spectrum related to DNMT3A germline variants.

Abstract

Over the past few years, next generation technologies have been applied to unravel the genetics of rare inherited diseases, facilitating the discovery of new susceptibility genes. We recently found germline DNMT3A gain-of-function variants in two patients with head and neck paragangliomas causing a characteristic hypermethylated DNA profile. Here, whole-exome sequencing identifies a novel germline DNMT3A variant (p.Gly332Arg) in a patient with bilateral carotid paragangliomas, papillary thyroid carcinoma and idiopathic intellectual disability. The variant, located in the Pro-Trp-Trp-Pro (PWWP) domain of the protein involved in chromatin targeting, affects a residue mutated in papillary thyroid tumors and located between the two residues found mutated in microcephalic dwarfism patients. Structural modelling of the variant in the DNMT3A PWWP domain predicts that the interaction with H3K36me3 will be altered. An increased methylation of DNMT3A target genes, compatible with a gain-of-function effect of the alteration, was observed in saliva DNA from the proband and in one independent acute myeloid leukemia sample carrying the same p.Gly332Arg variant. Although further studies are needed to support a causal role of DNMT3A variants in paraganglioma, the description of a new DNMT3A alteration in a patient with multiple clinical features suggests a heterogeneous phenotypic spectrum related to DNMT3A germline variants.

ABHD11 maintains 2-oxoglutarate metabolism by preserving functional lipoylation of the 2-oxoglutarate dehydrogenase complex

2-oxoglutarate (2-OG or α-ketoglutarate) relates mitochondrial metabolism to cell function by modulating the activity of 2-OG dependent dioxygenases involved in the hypoxia response and DNA/histone modifications. However, metabolic pathways that regulate these oxygen and 2-OG sensitive enzymes remain poorly understood. Here, using CRISPR Cas9 genome-wide mutagenesis to screen for genetic determinants of 2-OG levels, we uncover a redox sensitive mitochondrial lipoylation pathway, dependent on the mitochondrial hydrolase ABHD11, that signals changes in mitochondrial 2-OG metabolism to 2-OG dependent dioxygenase function. ABHD11 loss or inhibition drives a rapid increase in 2-OG levels by impairing lipoylation of the 2-OG dehydrogenase complex (OGDHc)-the rate limiting step for mitochondrial 2-OG metabolism. Rather than facilitating lipoate conjugation, ABHD11 associates with the OGDHc and maintains catalytic activity of lipoyl domain by preventing the formation of lipoyl adducts, highlighting ABHD11 as a regulator of functional lipoylation and 2-OG metabolism.

Metabolic Drivers in Hereditary Cancer Syndromes

Cancer is a multifaceted disease in which inherited genetic variants can be important drivers of tumorigenesis. The discovery that germline mutations of metabolic genes predispose to familial forms of cancer caused a shift in our understanding of how metabolism contributes to tumorigenesis, providing evidence that metabolic alterations can be oncogenic. In this review, we focus on mitochondrial enzymes whose mutations predispose to familial cancer, and we fully appraise their involvement in cancer formation and progression. Elucidating the molecular mechanisms that orchestrate transformation in these diverse tumors may answer key biological questions about tumor formation and evolution, leading to the identification of new therapeutic targets of intervention.

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.

Mutational profile and genotype/phenotype correlation of non-familial pheochromocytoma and paraganglioma

About 30%-40% of patients with pheochromocytoma (PCC) and paraganglioma (PGL) have underlying germline mutations in certain susceptibility genes despite absent family history of these tumors. Here, we present mutational profile of 101 such patients with PCC/PGL (PPGL) from the highly consanguineous population of Saudi Arabia. Results: Of 101 cases with PPGL, 37/101 (36.6%) had germline mutations. Mutations were detected in 30 cases by PCR and direct Sanger sequencing and in 7 additional cases by NGS. The most commonly mutated gene was SDHB (21/101 cases, 20.8%) and the most common SDHB mutation was c.268C>T, p.R90X occurring in 12/21 (57%) cases. Mutations also occurred in SDHC (4/101, 3.96%), SDHD (3/101, 3%), VHL (2/101, 2%) and MAX (2/101, 2%) genes. The following genes were mutated in 1 patient each (1%), RET, SDHA, SDHAF2, TMEM127 and NF1. Metastatic PPGL occurred in 6/21 cases (28.6%) with SDHB mutations and in 1 case with SDHAF2 mutation. Patients and Methods: DNA was isolated from peripheral blood (53 patients) or from non-tumorous formalin fixed paraffin embedded (FFPE) tissue (48 patients). PCR and direct Sanger sequencing of RET, SDHx, VHL, MAX and TMEM127 genes were performed. Cases without mutations were subjected to whole exome sequencing using next generation sequencing (NGS). Conclusion: About 37% of PPGL without family history of such tumors harbor germline mutations. The most commonly mutated gene is SDHB followed by SDHC, SDHD, VHL, MAX and rarely RET, SDHA, SDHAF2, TMEM127 and NF1. SDHB mutations were associated with metastatic PPGL in more than a quarter of cases.

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.

Optimizing Genetic Workup in Pheochromocytoma and Paraganglioma by Integrating Diagnostic and Research Approaches

Pheochromocytomas and paragangliomas (PPGL) are rare neuroendocrine tumors with a strong hereditary background and a large genetic heterogeneity. Identification of the underlying genetic cause is crucial for the management of patients and their families as it aids differentiation between hereditary and sporadic cases. To improve diagnostics and clinical management we tailored an enrichment based comprehensive multi-gene next generation sequencing panel applicable to both analyses of tumor tissue and blood samples. We applied this panel to tumor samples and compared its performance to our current routine diagnostic approach. Routine diagnostic sequencing of 11 PPGL susceptibility genes was applied to blood samples of 65 unselected PPGL patients at a single center in Dresden, Germany. Predisposing germline mutations were identified in 19 (29.2%) patients. Analyses of 28 PPGL tumor tissues using the dedicated PPGL panel revealed pathogenic or likely pathogenic variants in known PPGL susceptibility genes in 21 (75%) cases, including mutations in IDH2, ATRX and HRAS. These mutations suggest sporadic tumor development. Our results imply a diagnostic benefit from extended molecular tumor testing of PPGLs and consequent improvement of patient management. The approach is promising for determination of prognostic biomarkers that support therapeutic decision-making.

Targeting Cyclooxygenase-2 in Pheochromocytoma and Paraganglioma: Focus on Genetic Background

Cyclooxygenase 2 (COX-2) is a key enzyme of the tumorigenesis-inflammation interface and can be induced by hypoxia. A pseudohypoxic transcriptional signature characterizes pheochromocytomas and paragangliomas (PPGLs) of the cluster I, mainly represented by tumors with mutations in von Hippel–Lindau (VHL), endothelial PAS domain-containing protein 1 (EPAS1), or succinate dehydrogenase (SDH) subunit genes. The aim of this study was to investigate a possible association between underlying tumor driver mutations and COX-2 in PPGLs. COX-2 gene expression and immunoreactivity were examined in clinical specimens with documented mutations, as well as in spheroids and allografts derived from mouse pheochromocytoma (MPC) cells. COX-2 in vivo imaging was performed in allograft mice. We observed significantly higher COX-2 expression in cluster I, especially in VHL-mutant PPGLs, however, no specific association between COX-2 mRNA levels and a hypoxia-related transcriptional signature was found. COX-2 immunoreactivity was present in about 60% of clinical specimens as well as in MPC spheroids and allografts. A selective COX-2 tracer specifically accumulated in MPC allografts. This study demonstrates that, although pseudohypoxia is not the major determinant for high COX-2 levels in PPGLs, COX-2 is a relevant molecular target. This potentially allows for employing selective COX-2 inhibitors as targeted chemotherapeutic agents and radiosensitizers. Moreover, available models are suitable for preclinical testing of these treatments.

Pheochromocytomas and Paragangliomas: Bypassing Cellular Respiration

Abstract: Pheochromocytomas and paragangliomas (PPGL) are rare neuroendocrine tumors that show the highest heritability of all human neoplasms and represent a paradoxical example of genetic heterogeneity. Amongst the elevated number of genes involved in the hereditary predisposition to the disease (at least nineteen) there are eleven tricarboxylic acid (TCA) cycle-related genes, some of which are also involved in the development of congenital recessive neurological disorders and other cancers such as cutaneous and uterine leiomyomas, gastrointestinal tumors and renal cancer. Somatic or germline mutation of genes encoding enzymes catalyzing pivotal steps of the TCA cycle not only disrupts cellular respiration, but also causes severe alterations in mitochondrial metabolite pools. These latter alterations lead to aberrant accumulation of "oncometabolites" that, in the end, may lead to deregulation of the metabolic adaptation of cells to hypoxia, inhibition of the DNA repair processes and overall pathological changes in gene expression. In this review, we will address the TCA cycle mutations leading to the development of PPGL, and we will discuss the relevance of these mutations for the transformation of neural crest-derived cells and potential therapeutic approaches based on the emerging knowledge of underlying molecular alterations.