Comprehensive genetic analyses have identified germline
and
gene mutations as predominant causes of metastatic paraganglioma and pheochromocytoma. However, some suspicious cases remain unexplained. ...In this study, we performed whole-exome sequencing of a paraganglioma exhibiting an
-like molecular profile in the absence of
or
mutations and identified a germline mutation in the
gene, which encodes the mitochondrial 2-oxoglutarate/malate carrier. Germline
mutations were identified in six other patients, five of whom had metastatic disease. These mutations were associated with loss of heterozygosity, suggesting that
acts as a tumor-suppressor gene. Pseudohypoxic and hypermethylator phenotypes comparable with those described in
- and
-related tumors were observed both in tumors with mutated
and in
immortalized mouse chromaffin knockout cells generated by CRISPR-Cas9 technology. These data show that
is a novel paraganglioma susceptibility gene for which loss of function correlates with metastatic presentation.
A gene encoding a mitochondrial carrier is implicated in a hereditary cancer predisposition syndrome, expanding the role of mitochondrial dysfunction in paraganglioma.
.
Paragangliomas are neuroendocrine tumors frequently associated with mutations in RET, NF1, VHL, and succinate dehydrogenase (SDHx) genes. Methylome analysis of a large paraganglioma cohort identified ...three stable clusters, associated with distinct clinical features and mutational status. SDHx-related tumors displayed a hypermethylator phenotype, associated with downregulation of key genes involved in neuroendocrine differentiation. Succinate accumulation in SDH-deficient mouse chromaffin cells led to DNA hypermethylation by inhibition of 2-OG-dependent histone and DNA demethylases and established a migratory phenotype reversed by decitabine treatment. Epigenetic silencing was particularly severe in SDHB-mutated tumors, potentially explaining their malignancy. Finally, inactivating FH mutations were identified in the only hypermethylated tumor without SDHx mutations. These findings emphasize the interplay between the Krebs cycle, epigenomic changes, and cancer.
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•SDH and FH mutations establish a hypermethylator phenotype in PGL/PCC•Succinate inhibits DNA and histone demethylases in SDH-deficient chromaffin cells•DNA hypermethylation silences key genes involved in neuroendocrine differentiation•A stronger hypermethylator phenotype may explain malignancy of SDHB-mutated tumors
Approximately 20% of patients diagnosed with a phaeochromocytoma or paraganglioma carry a germline mutation in one of the succinate dehydrogenase (SDHx) genes (SDHA, SDHB, SDHC and SDHD), which ...encode the four subunits of the SDH enzyme. When a pathogenic SDHx mutation is identified in an affected patient, genetic counselling is proposed for first-degree relatives. Optimal initial evaluation and follow-up of people who are asymptomatic but might carry SDHx mutations have not yet been agreed. Thus, we established an international consensus algorithm of clinical, biochemical and imaging screening at diagnosis and during surveillance for both adults and children. An international panel of 29 experts from 12 countries was assembled, and the Delphi method was used to reach a consensus on 41 statements. This Consensus Statement covers a range of topics, including age of first genetic testing, appropriate biochemical and imaging tests for initial tumour screening and follow-up, screening for rare SDHx-related tumours and management of elderly people who have an SDHx mutation. This Consensus Statement focuses on the management of asymptomatic SDHx mutation carriers and provides clinicians with much-needed guidance. The standardization of practice will enable prospective studies in the near future.
Pheochromocytomas and paragangliomas (PPGLs) are rare neuroendocrine tumors. Whereas most PPGLs are benign, up to 20% may become metastatic with
- and
-mutated tumors showing the higher risk. We ...aimed at determining the contribution of immortalization mechanisms to metastatic progression.
Immortalization mechanisms were investigated in 200 tumors. To identify telomerase (+) tumors, we analyzed genomic alterations leading to transcriptional activation of
comprising promoter mutations, hypermethylation and gain copy number. To identify tumors that activated the alternative lengthening of telomere (ALT) mechanism, we combined analyses of telomere length by slot blot, telomere heterogeneity by telomere FISH, and
mutations by next-generation sequencing. Univariate/multivariate and metastasis-free survival (MFS) and overall survival (OS) analyses were carried out for assessment of risk factors and clinical outcomes.
Only 37 of 200 (18.5%) tumors achieved immortalization. Telomerase activation occurred in 12 metastatic tumors and was prevalent in
-mutated paragangliomas (
= 2.42e-09). ALT features were present in 25 tumors, mostly pheochromocytomas, regardless of metastatic status or molecular group (
= 0.169), yet
mutations were found preferentially in
-mutated metastatic tumors (
= 0.0014). Telomerase activation and
mutations were independent factors of poor prognosis: MFS (hazard ratio, 48.2 and 33.1;
= 6.50E-07 and 1.90E-07, respectively); OS (hazard ratio, 97.4 and 44.1;
= 4.30E-03 and 2.00E-03, respectively) and were associated with worse MFS and OS (log-rank tests
< 0.0001).
Assessment of telomerase activation and
mutations could be used to identify metastatic PPGLs, particularly in tumors at high risk of progression.
The SNORD116 locus lies in the 15q11-13 region of paternally expressed genes implicated in Prader-Willi Syndrome (PWS), a complex disease accompanied by obesity and severe neurobehavioural ...disturbances. Cases of PWS patients with a deletion encompassing the SNORD116 gene cluster, but preserving the expression of flanking genes, have been described. We report a 23-year-old woman who presented clinical criteria of PWS, including the behavioural and nutritional features, obesity, developmental delay and endocrine dysfunctions with hyperghrelinemia. We found a paternally transmitted highly restricted deletion of the SNORD116 gene cluster, the shortest described to date (118 kb). This deletion was also present in the father. This finding in a human case strongly supports the current hypothesis that lack of the paternal SNORD116 gene cluster has a determinant role in the pathogenesis of PWS. Moreover, targeted analysis of the SNORD116 gene cluster, complementary to SNRPN methylation analysis, should be carried out in subjects with a phenotype suggestive of PWS.
Chuvash polycythemia is an autosomal recessive form of erythrocytosis associated with a homozygous p.Arg200Trp mutation in the von Hippel-Lindau (VHL) gene. Since this discovery, additional VHL ...mutations have been identified in patients with congenital erythrocytosis, in a homozygous or compound-heterozygous state. VHL is a major tumor suppressor gene, mutations in which were first described in patients presenting with VHL disease, which is characterized by the development of highly vascularized tumors. Here, we identify a new VHL cryptic exon (termed E1′) deep in intron 1 that is naturally expressed in many tissues. More importantly, we identify mutations in E1′ in 7 families with erythrocytosis (1 homozygous case and 6 compound-heterozygous cases with a mutation in E1′ in addition to a mutation in VHL coding sequences) and in 1 large family with typical VHL disease but without any alteration in the other VHL exons. In this study, we show that the mutations induced a dysregulation of VHL splicing with excessive retention of E1′ and were associated with a downregulation of VHL protein expression. In addition, we demonstrate a pathogenic role for synonymous mutations in VHL exon 2 that altered splicing through E2-skipping in 5 families with erythrocytosis or VHL disease. In all the studied cases, the mutations differentially affected splicing, correlating with phenotype severity. This study demonstrates that cryptic exon retention and exon skipping are new VHL alterations and reveals a novel complex splicing regulation of the VHL gene. These findings open new avenues for diagnosis and research regarding the VHL-related hypoxia-signaling pathway.
•Mutations in a VHL cryptic exon may be found in patients with familial erythrocytosis or VHL disease.•Synonymous mutations in VHL exon 2 may induce exon skipping and cause familial erythrocytosis or VHL disease.
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Pheochromocytomas and paragangliomas (PCCs/PGLs) are neural crest-derived tumours with a very strong genetic component. Here we report the first integrated genomic examination of a large collection ...of PCC/PGL. SNP array analysis reveals distinct copy-number patterns associated with genetic background. Whole-exome sequencing shows a low mutation rate of 0.3 mutations per megabase, with few recurrent somatic mutations in genes not previously associated with PCC/PGL. DNA methylation arrays and miRNA sequencing identify DNA methylation changes and miRNA expression clusters strongly associated with messenger RNA expression profiling. Overexpression of the miRNA cluster 182/96/183 is specific in SDHB-mutated tumours and induces malignant traits, whereas silencing of the imprinted DLK1-MEG3 miRNA cluster appears as a potential driver in a subgroup of sporadic tumours. Altogether, the complete genomic landscape of PCC/PGL is mainly driven by distinct germline and/or somatic mutations in susceptibility genes and reveals different molecular entities, characterized by a set of unique genomic alterations.
Purpose
Germline mutations in genes encoding succinate dehydrogenase (SDH) are frequent in patients with pheochromocytoma and paraganglioma (PPGL). They lead to SDH inactivation, mediating a massive ...accumulation of succinate
,
which constitutes a highly specific biomarker of
SDHx
-mutated tumors when measured in vitro. In a recent pilot study, we showed that magnetic resonance spectroscopy (
1
H-MRS) optimized for succinate detection (SUCCES) could detect succinate in vivo in both allografted mouse models and PPGL patients. The objective of this study was to prospectively assess the diagnostic performances of
1
H-MRS SUCCES sequence for the identification of SDH deficiency in PPGL patients.
Methods
Forty-nine patients presenting with 50 PPGLs were prospectively enrolled in our referral center for
1
H-MRS SUCCES. Two observers blinded to the clinical characteristics and genetic status analyzed the presence of a succinate peak and confronted the results to a composite gold standard combining PPGL genetic testing and/or in vitro protein analyses in the tumor.
Results
A succinate peak was observed in 20 tumors, all of which had proven SDH deficiency using the gold standard (17 patients with germline
SDHx
mutations, 2 with a somatic
SDHD
mutation, and 1 with negative SDHB IHC and SDH loss of function). A false negative result was observed in 3 tumors. Sensitivity, specificity, positive predictive value, negative predictive value, and accuracy of
1
H-MRS SUCCES were respectively 87%, 100%, 100%, 90%, and 94%.
Conclusions
Detection of succinate using
1
H-MRS is a highly specific and sensitive hallmark of SDH
-
deficiency in PPGLs.
Germline mutations in the RET, SDHA, SDHAF2, SDHB, SDHC, SDHD, MAX, TMEM127, NF1 or VHL genes are identified in about 30% of patients with pheochromocytoma or paraganglioma and somatic mutations in ...RET, VHL or MAX genes are reported in 17% of sporadic tumors. In the present study, using mutation screening of the NF1 gene, mapping of chromosome aberrations by single nucleotide polymorphism (SNP) array, microarray-based expression profiling and immunohistochemistry (IHC), we addressed the implication of NF1 somatic alterations in pheochromocytomas and paragangliomas. We studied 53 sporadic tumors, selected because of their classification with RET/NF1/TMEM127-related tumors by genome wide expression studies, as well as a second set of 11 independent tumors selected on their low individual levels of NF1 expression evaluated by microarray. Direct sequencing of the NF1 gene in tumor DNA identified the presence of an inactivating NF1 somatic mutation in 41% (25/61) of analyzed sporadic tumors, associated with loss of the wild-type allele in 84% (21/25) of cases. Gene expression signature of NF1-related tumors highlighted the downregulation of NF1 and the major overexpression of SOX9. Among the second set of 11 tumors, two sporadic tumors carried somatic mutations in NF1 as well as in another susceptibility gene. These new findings suggest that NF1 loss of function is a frequent event in the tumorigenesis of sporadic pheochromocytoma and strengthen the new concept of molecular-based targeted therapy for pheochromocytoma or paraganglioma.
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