Quantifying evidence toward pathogenicity for rare phenotypes: The case of succinate dehydrogenase genes, SDHB and SDHD

PURPOSE

The weight of the evidence to attach to observation of a novel rare missense variant in SDHB or SDHD in individuals with the rare neuroendocrine tumors, pheochromocytomas and paragangliomas (PCC/PGL), is uncertain.

METHODS

We compared the frequency of SDHB and SDHD very rare missense variants (VRMVs) in 6328 and 5847 cases of PCC/PGL, respectively, with that of population controls to generate a pan-gene VRMV likelihood ratio (LR). Via windowing analysis, we measured regional enrichments of VRMVs to calculate the domain-specific VRMV-LR (DS-VRMV-LR). We also calculated subphenotypic LRs for variant pathogenicity for various clinical, histologic, and molecular features.

RESULTS

We estimated the pan-gene VRMV-LR to be 76.2 (54.8-105.9) for SDHB and 14.8 (8.7-25.0) for SDHD. Clustering analysis revealed an SDHB enriched region (ɑɑ 177-260, P = .001) for which the DS-VRMV-LR was 127.2 (64.9-249.4) and an SDHD enriched region (ɑɑ 70-114, P = .000003) for which the DS-VRMV-LR was 33.9 (14.8-77.8). Subphenotypic LRs exceeded 6 for invasive disease (SDHB), head-and-neck disease (SDHD), multiple tumors (SDHD), family history of PCC/PGL, loss of SDHB staining on immunohistochemistry, and succinate-to-fumarate ratio >97 (SDHB, SDHD).

CONCLUSION

Using methodology generalizable to other gene-phenotype dyads, the LRs relating to rarity and phenotypic specificity for a single observation in PCC/PGL of a SDHB/SDHD VRMV can afford substantial evidence toward pathogenicity.

Undifferentiated and dedifferentiated urological carcinomas: lessons learned from the recent developments

Loss of the morphological and immunophenotypic characteristics of a neoplasm is a well-known phenomenon in surgical pathology and occurs across different tumor types in almost all organs. This process may be either partial, characterized by transition from well differentiated to undifferentiated tumor component (=dedifferentiated carcinomas) or complete (=undifferentiated carcinomas). Diagnosis of undifferentiated carcinoma is significantly influenced by the extent of sampling. Although the concept of undifferentiated and dedifferentiated carcinoma has been well established for other organs (e.g. endometrium), it still has not been fully defined for urological carcinomas. Accordingly, undifferentiated/ dedifferentiated genitourinary carcinomas are typically lumped into the spectrum of poorly differentiated, sarcomatoid, or unclassified (NOS) carcinomas. In the kidney, dedifferentiation occurs across all subtypes of renal cell carcinoma (RCC), but certain genetically defined RCC types (SDH-, FH- and PBRM1- deficient RCC) seem to have inherent tendency to dedifferentiate. Histologically, the undifferentiated component displays variable combination of four patterns: spindle cells, pleomorphic giant cells, rhabdoid cells, and undifferentiated monomorphic cells with/without prominent osteoclastic giant cells. Any of these may occasionally be associated with heterologous mesenchymal component/s. Their immunophenotype is often simple with expression of vimentin and variably pankeratin or EMA. Precise subtyping of undifferentiated (urothelial versus RCC and the exact underlying RCC subtype) is best done by thorough sampling supplemented as necessary by immunohistochemistry (e.g. FH, SDHB, ALK) and/ or molecular studies. This review discusses the morphological and molecular genetic spectrum and the recent develoments on the topic of dedifferentiated and undifferentiated genitourinary carcinomas.

LncRNA expression and SDHB mutations in pheochromocytomas and paragangliomas

Although pheochromocytomas and paragangliomas (PPGLs) are usual low-grade neoplasms, the metastatic forms of these lesions are associated with high morbidity and mortality. Recent studies have discovered multiple aberrantly expressed long non-coding RNAs (lncRNAs) in cancers that may have regulatory roles in tumor pathogenesis and metastasis; however, the roles of some lncRNAs in PPGLs are still unknown. The expression levels of lncRNAs including metastasis-associated lung adenocarcinoma transcript (MALAT1), prostate cancer antigen 3 (PCA3), and HOX transcript antisense intergenic RNA (HOTAIR) in PPGLs were analyzed by in situ hybridization, using two tissue microarrays (TMAs). The pheochromocytoma (PCC) TMA consisted of normal adrenal medulla (N = 25), non-metastatic PCCs (N = 76) and metastatic PCCs (N = 5) while the paraganglioma (PGL) TMA had 73 non-metastatic PGLs and 5 metastatic PGLs. Immunohistochemical staining was performed on all samples with an anti-SDHB antibody. The correlations between lncRNA expression, loss of SDHB expression and clinical characteristics including tumor progression and disease prognosis were investigated. The expression levels of MALAT1 and PCA3 were significantly elevated (2.5-3.9 folds) in both non-metastatic and metastatic PCCs compared to normal adrenal medulla, although there were no significant differences between the non-metastatic and metastatic neoplasms. In contrast to non-metastatic PGLs, metastatic PGLs had significantly upregulated expression of MALAT1, PCA3, and HOTAIR. SDHB loss was more frequently observed in PGLs (25 of 78), especially in metastatic PGLs (5 of 5), compared to PCCs (2 of 81) and in 0 of 5 metastatic PCCs. Patients with SDHB loss, in contrast to SDHB retained, were younger at diagnosis, had higher rates of tumor recurrence, metastatic disease, and mortality. In addition, PGLs with SDHB loss had significantly increased expression of PCA3 compared to tumors with intact SDHB expression. Our findings suggest that specific lncRNAs may be involved in the SDHx signaling pathways in the tumorigenesis and in the development of PPGL.

Prevalence of Germline Variants in a Large Cohort of Japanese Patients with Pheochromocytoma and/or Paraganglioma

Simple Summary

Pheochromocytoma/paraganglioma (PPGL) has been recognised as one of the most frequent inherited tumours with genetic heterogeneity based on studies in Caucasian populations. Early identification of germline variants is crucial for accurate treatment and follow-up in affected patients and relatives. However, there are only a few large cohort studies in Asia and none from the Japanese population. In this first comprehensive study of Japanese patients with PPGL, we found one in four PPGLs with apparently sporadic presentation harboured germline variant in any of the seven susceptibility genes (MAX, SDHB, SDHC, SDHD, TMEM127, VHL, and RET). SDHB was the most frequently mutated gene and was strongly associated with metastatic PPGLs. Our findings emphasise the importance of genetic testing in determining appropriate treatment and follow-up strategies for patients and relatives.

Abstract

The high incidence of germline variants in pheochromocytoma and paraganglioma (PPGL) has been reported mainly in Europe, but not among Japanese populations in Asia. We aimed to study the prevalence of germline variants in Japanese PPGL patients and the genotype–phenotype correlation. We examined 370 PPGL probands, including 43 patients with family history and/or syndromic presentation and 327 patients with apparently sporadic (AS) presentation. Clinical data and blood samples were collected, and the seven major susceptibility genes (MAX, SDHB, SDHC, SDHD, TMEM127, VHL, and RET) were tested using Sanger sequencing. Overall, 120/370 (32.4%) patients had pathogenic or likely pathogenic variants, with 81/327 (24.8%) in AS presentation. SDHB was the most frequently mutated gene (57, 15.4%), followed by SDHD (27, 7.3%), and VHL (18, 4.9%). The incidence of metastatic PPGL was high in SDHB carriers (21/57, 36.8%). A few unique recurrent variants (SDHB c.137G>A and SDHB c.470delT) were detected in this Japanese cohort, highlighting ethnic differences. In summary, almost a quarter of patients with apparently sporadic PPGL in Japan harboured germline variants of the targeted genes. This study reinforces the recommendation in Western guidelines to perform genetic testing for PPGL and genotype-based clinical decision-making in the Japanese population.

Efficacy of Immunohistochemistry for SDHB in the Screening of Hereditary Pheochromocytoma-Paraganglioma

The most common genetic backgrounds of hereditary paraganglioma and pheochromocytoma (PPGL) are SDHx germline mutations. Given the fact that the immunohistochemistry (IHC) result for SDHB is always negative regardless of the type of SDHx mutation, we aimed to evaluate the efficacy of using SDHB IHC for screening SDHx mutations in PPGL cases. In total, 52 patients who underwent surgery for PPGL treatment between 2006 and 2020 and underwent genetic analysis at diagnosis were included. Tissue microarrays (TMAs) were constructed with PPGL tissues and IHC for SDHB was performed on TMA sections. All 10 patients with SDHB-negative IHC contained SDHB or SDHD mutations. The genetic test results of patients with SDHB-weakly positive IHC varied (one SDHB, two RET, one VHL, and three unknown gene mutations). There were no SDHx mutations in the SDHB-positive IHC group. Six patients with weakly positive SDHB IHC with primarily unknown genetic status were re-called and underwent next-generation sequencing. None of them had SDHx mutations. In conclusion, SDHB-negative IHC is a cost-effective and reliable method to predict SDHx mutations. However, in the case of weakly positive SDHB staining, an additional gene study should be considered.

Identification and Characterization of the Succinate Dehydrogenase Complex Iron Sulfur Subunit B Gene in the Oriental River Prawn, Macrobrachium nipponense

Previous studies have revealed that SDHB has potential functions in the male sexual differentiation and development in M. nipponense through providing ATP. In this study, the functions of Mn-SDHB were further analyzed in depth using quantitative polymerase chain reaction (qPCR), in situ hybridization, western-blot, and RNA interference (RNAi), combined with the histological observations. The full-genome sequence of Mn-SDHB was 54,608 bp at Chromosome 34, including 7 introns and 6 exons. The full-length cDNA sequence of Mn-SDHB was 1,268 base pairs (bp) long with an open reading frame of 807 bp, encoding for 268 amino acids. The highest expression level of Mn-SDHB in different tissues was observed in the testis, and male prawns at post-larval developmental stage 25 during different developmental stages, indicating that SDHB was potentially involved in the male sexual development in M. nipponense. In situ hybridization and western-blot analysis indicated that SDHB plays essential roles in the testis development. The in situ hybridization analysis also implies the potential roles of Mn-SDHB in ovarian development. The expressions of Mn-IAG were decreased after Mn-SDHB dsRNA injection, indicating SDHB has the positive regulatory effects on IAG in M. nipponese. Thus, SDHB was involved in the mechanism of the male sexual development. The testis development was inhibited, and sperms were rarely observed after 10 days of Mn-SDHB dsRNA injection, indicating SDHB has positive effects on the male sexual development in M. nipponense. This study highlights the functions of SDHB in M. nipponense, which provide new insights for the future studies of the male sexual development in other crustacean species.

SDHB-Associated Paraganglioma Syndrome in Africa-A Need for Greater Genetic Testing

A germline mutation is identified in almost 40% of pheochromocytoma/paraganglioma (PPGL) syndromes. Genetic testing and counseling are essential for the management of index cases as well as presymptomatic identification and preemptive management of affected family members. Mutations in the genes encoding the mitochondrial enzyme succinate dehydrogenase (SDH) are well described in patients with hereditary PPGL. Among patients of African ancestry, the prevalence, phenotype, germline mutation spectrum, and penetrance of SDH mutations is poorly characterized. We describe a multifocal paraganglioma in a young African male with an underlying missense succinate dehydrogenase subunit B (SDHB) mutation and a history of 3 first-degree relatives who died at young ages from suspected cardiovascular causes. The same SDHB mutation, Class V variant c.724C>A p.(Arg242Ser), was detected in one of his asymptomatic siblings. As there are limited data describing hereditary PPGL syndromes in Africa, this report of an SDHB-associated PPGL is a notable contribution to the literature in this growing field. Due to the noteworthy clinical implications of PPGL mutations, this work highlights the existing need for broader genetic screening among African patients with PPGL despite the limited healthcare resources available in this region.

Succinate Dehydrogenase Complex Iron Sulfur Subunit B (SDHB) Immunohistochemistry in Pheochromocytoma, Head and Neck Paraganglioma, Thoraco-Abdomino-Pelvic Paragangliomas: Is It a Good Idea to Use in Routine Work?

Background:

In this study, we aimed to detect Succinate Dehydrogenase Complex Iron Sulfur Subunit B (SDHB) frequency in paragangliomas and pheochromocytomas (PPGL) with immunohistochemistry; compare with Pheochromacytoma of the Adrenal Gland Scaled Score (PASS) classification and analyse the differences between pheochromocytoma (Pheo), head-neck paragangliomas (HNPGL) and thoraco-abdominal-pelvic paraganglioma (TAPPGL) sub-groups.

Methods:

A total 114 PPGL cases (73 HNPGL, 15 TAPPGL and 27 Pheo belonging to 112 cases) are included. Immunohistochemically, SDHB and Ki-67 are investigated and malignancy risks are determined by PASS classification. Results are assessed statistically with chi-square test and p <0,01 is considered significant.

Results:

SDHB mutations are observed in 20 of 114 (17.54 %) PPGL cases, 3 (11,12%) of which is Pheo, 12 (16,44) is HNPGL, and 5 (35,71%) is TAPPGL (P <0,02). While 15/82 (18,29%) cases with SDHB mutations do not have a malignancy potential according to PASS classification, 5/32 (15,63%) cases has (p=0,73). TAPPGL, HNPGL and Pheo sub-groups have a significant difference between SDHB expression (p <0,02), malignancy potential according to PASS classification (p <0,0001) and Ki-67 proliferation index (p <0,0001).

Conclusion:

To identify patients for molecular pathological examination, routine application of SDHB immunohistochemistry to PPGL tumors are suggested especially in HNPGLs.

SDHB Suppresses the Tumorigenesis and Development of ccRCC by Inhibiting Glycolysis

Metabolic reprogramming is the prominent feature of clear cell renal cell carcinoma (ccRCC). Succinate dehydrogenase subunit B (SDHB) is one of subunits of mitochondrial respiratory chain complex II. The loss of SDHB function is closely related with metabolic changes in kidney cancer cells. However, the role and molecular mechanism of SDHB in ccRCC occurrence and progression are still unclear. In this study, the results of bioinformatics analyses on GEO, TCGA and oncomine databases and immunohistochemistry showed that the expression level of SDHB was downregulated in ccRCC tissues. SDHB level was gradually downregulated as ccRCC stage and grade progressed. The low level of SDHB was associated with poor prognosis of ccRCC patients, especially for advanced ccRCC patients. Increased methylation levels in SDHB gene promoter led to the downregulation of SDHB level in ccRCC tissues. SDHB was correlated with many metabolism related genes and its interacting proteins were enriched in metabolic pathways. SDHB overexpression suppressed the proliferation, colony formation and migration of ccRCC cells by inhibiting aerobic glycolysis. SDHB may be a potential prognostic marker and therapeutic target for ccRCC.

Inherited Follicular Epithelial-Derived Thyroid Carcinomas: From Molecular Biology to Histological Correlates

Cancer derived from thyroid follicular epithelial cells is common; it represents the most common endocrine malignancy. The molecular features of sporadic tumors have been clarified in the past decade. However the incidence of familial disease has not been emphasized and is often overlooked in routine practice. A careful clinical documentation of family history or familial syndromes that can be associated with thyroid disease can help identify germline susceptibility-driven thyroid neoplasia. In this review, we summarize a large body of information about both syndromic and non-syndromic familial thyroid carcinomas. A significant number of patients with inherited non-medullary thyroid carcinomas manifest disease that appears to be sporadic disease even in some syndromic cases. The cytomorphology of the tumor(s), molecular immunohistochemistry, the findings in the non-tumorous thyroid parenchyma and other associated lesions may provide insight into the underlying syndromic disorder. However, the increasing evidence of familial predisposition to non-syndromic thyroid cancers is raising questions about the importance of genetics and epigenetics. What appears to be "sporadic" is becoming less often truly so and more often an opportunity to identify and understand novel genetic variants that underlie tumorigenesis. Pathologists must be aware of the unusual morphologic features that should prompt germline screening. Therefore, recognition of harbingers of specific germline susceptibility syndromes can assist in providing information to facilitate early detection to prevent aggressive disease.

Succinate dehydrogenase deficient gastrointestinal stromal tumor in a three month old boy with a fatal clinical course: a case report and review of literature

Background

Succinate dehydrogenase deficient gastrointestinal stromal tumors (SDH-deficient GISTs), which lack KIT or PDGFRA mutations demonstrate unique clinical and pathological features, and they respond poorly to standard targeted therapy. We herein present a novel case of SDH-deficient GIST in a three-month-old infant’s colon mesentery, and he is the youngest patientto date.

Case presentation

The infantpresented with complaints of blood in the stool. CT showed a 6.3 × 4.6 cm mass in the left lower retroperitoneal. Complete resection of tumor and segmental bowel resection was performed without regional lymphadenectomy. Histologically, tumor cells were distinctive in their multinodular colon wall involvement with interspersed tracts of colon wall smooth muscle. The tumor was composed mainly of epithelioid cells. Immunohistochemically, the tumor cells were positive for Vim, CD117, PDGFR, while negative for SDHB. Mutational analysis showed a synonymous mutation for SDHB and wild-type for KIT and PDGFRA. Two months after surgery, metastases were found and Imatinib was administered. Unfortunately, the disease continued to progress, and the infant died 5 months after surgery.

Conclusions

SDH-deficient GISTs comprise a subgroup of a relatively rare tumor type and show a number of clinically and biologically unique features, especially for infants. It is of great importance to developing new therapeutic targets and novel specific drugs.

Update on Molecular Genetics of Gastrointestinal Stromal Tumors

Gastrointestinal stromal tumors (GISTs) are the most common mesenchymal tumors of the gastrointestinal tract. The majority are sporadic, solitary tumors that harbor mutually exclusive KIT or PDGFRA gain-of-function mutations. The type of mutation in addition to risk stratification corresponds to the biological behavior of GIST and response to treatment. Up to 85% of pediatric GISTs and 10–15% of adult GISTs are devoid of these (KIT/PDGFRA) mutations and are referred to as wild-type GISTs (wt-GIST). It has been shown that these wt-GISTs are a heterogeneous tumor group with regard to their clinical behavior and molecular profile. Recent advances in molecular pathology helped to further sub-classify the so-called “wt-GISTs”. Based on their significant clinical and molecular heterogeneity, wt-GISTs are divided into a syndromic and a non-syndromic (sporadic) subgroup. Recently, the use of succinate dehydrogenase B (SDHB) by immunohistochemistry has been used to stratify GIST into an SDHB-retained and an SDHB-deficient group. In this review, we focus on GIST sub-classification based on clinicopathologic, and molecular findings and discuss the known and yet emerging prognostic and predictive genetic alterations. We also give insights into the limitations of targeted therapy and highlight the mechanisms of secondary resistance.

Metastatic Paraganglioma of the Spine With SDHB Mutation: Case Report and Review of the Literature

BACKGROUND

Paragangliomas (PGLs) are rare neuroendocrine tumors that can arise from any autonomic ganglion of the body. Most PGLs do not metastasize. Here, we present a rare case of metastatic PGL of the spine in a patient with a germline pathogenic succinate dehydrogenase subunit B (SDHB) mutation.

METHODS

In addition to a case report we provide a literature review of metastatic spinal PGL to highlight the importance of genetic testing and long-term surveillance of these patients.

RESULTS

A 45-year-old woman with history of spinal nerve root PGL, 17 years prior, presented with back pain of several months' duration. Imaging revealed multilevel lytic lesions throughout the cervical, thoracic, and lumbar spine as well as involvement of the right mandibular condyle and clavicle. Percutaneous biopsy of the L1 spinal lesion confirmed metastatic PGL and the patient underwent posterior tumor resection and instrumented fusion of T7-T11. Postoperatively the patient was found to have a pathogenic SDHB deletion.

CONCLUSIONS

Patients with SDHx mutation, particularly SDHB, have increased risk of developing metastatic PGLs. Consequently, these individuals require long-term surveillance given the risk for developing new tumors or disease recurrence, even years to decades after primary tumor resection. Surgical management of spinal metastatic PGL involves correcting spinal instability, minimizing tumor burden, and alleviating epidural cord compression. In patients with metastatic PGL of the spine, genetic testing should be considered.

Carney Triad, Carney-Stratakis Syndrome, 3PAS and Other Tumors Due to SDH Deficiency

Succinate dehydrogenase (SDH) is a key respiratory enzyme that links Krebs cycle and electron transport chain and is comprised of four subunits SDHA, SDHB, SDHC and SDHD. All SDH-deficient tumors are caused by or secondary to loss of SDH activity. As many as half of the familial cases of paragangliomas (PGLs) and pheochromocytomas (PHEOs) are due to mutations of the SDHx subunits. Gastrointestinal stromal tumors (GISTs) associated with SDH deficiency are negative for KIT/PDGFRA mutations and present with distinctive clinical features such as early onset (usually childhood or adolescence) and almost exclusively gastric location. SDH-deficient GISTs may be part of distinct clinical syndromes, Carney-Stratakis syndrome (CSS) or dyad and Carney triad (CT). CSS is also known as the dyad of GIST and PGL; it affects both genders equally and is inherited in an autosomal dominant manner with incomplete penetrance. CT is a very rare disease; PGL, GIST and pulmonary chondromas constitute CT which shows female predilection and may be a mosaic disorder. Even though there is some overlap between CT and CSS, as both are due to SDH deficiency, CSS is caused by inactivating germline mutations in genes encoding for the SDH subunits, while CT is mostly caused by a specific pattern of methylation of the SDHC gene and may be due to germline mosaicism of the responsible genetic defect.

Differences in Clinical Manifestations and Tumor Features Between Metastatic Pheochromocytoma/Paraganglioma Patients With and Without Germline SDHB Mutation

OBJECTIVE

To compare metastatic pheochromocytoma/paraganglioma (MPP) patients with germline SDHB mutations (SDHB MPP) and without SDHB mutations (non-SDHB MPP) in terms of baseline clinical manifestations, tumor characteristics, and outcomes.

METHODS

Clinical data were retrospectively reviewed in 101 MPP patients, including 34 SDHB MPP patients and 61 non-SDHB MPP patients.

RESULTS

SDHB MPP patients presented at a younger age at onset, diagnosis, or metastasis (25 ± 16 vs 36 ± 14, 28 ± 17 vs 38 ± 15, and 31 ± 17 vs 44 ± 14 years old, respectively, P < .01 for all) than non-SDHB patients. Compared with their non-SDHB counterparts, SDHB patients were more likely to have paragangliomas (83% vs 47%, P < .05), synchronous metastases (44% vs 23%, P < .05), bone metastases (80% vs 48%, P < .01), and a shorter progression-free survival (3 years vs 5 years, P < .01). The Ki-67 index was higher in SDHB tumors (P < .05). The 5- and 10-year survival rates were 79% and 74%, respectively, in all patients. Seventeen patients died from MPP, and the time from metastasis to death in patients who had received systemic therapy was significantly longer than in those who had not (3.1 ± 1.5 vs 1.4 ± 0.7 years, P < .01).

CONCLUSION

Compared with MPP patients without SDHB mutations, MPP patients with SDHB mutations were younger at onset, diagnosis, or metastasis; had a higher incidence of synchronous metastases, higher ratio of paraganglioma, and higher Ki-67 index; had a shorter postoperative progression-free survival; and were more likely to develop bone metastasis or sole liver metastasis. Our results suggest that patients with SDHB mutations should be identified early and monitored regularly to achieve optimal clinical outcomes.

Characteristics and genetic testing outcomes of patients with clinically suspected paraganglioma/pheochromocytoma (PGL/PCC) syndrome in Singapore

BACKGROUND

Hereditary paraganglioma (PGL) and pheochromocytoma (PCC) syndromes are rare conditions, with limited data on spectrum of causative gene variants of these syndromes in Asian patients.

METHODS

We describe the clinical characteristics and genetic testing outcomes of patients with suspected hereditary PGL/PCC who were referred to a tertiary cancer genetics clinic in Singapore.

RESULTS

Among 2196 patients with suspected hereditary cancer syndrome evaluated at the cancer genetics clinic from 2000 to 2019, 13/2196 (0.6%) patients fulfilled clinical suspicion for hereditary PGL/PCC syndrome. After genetic counselling, 10 patients underwent multi-gene next generation sequencing and deletion/duplication analysis, including SDHAF2, SDHA, SDHB, SDHC, SDHD, VHL, NF1, RET, MAX, and TMEM127. Seven of 10 patients (70%) were identified to carry pathogenic variants, including 3 unrelated Chinese patients with head and neck PGL who carried the same SDHD: c.3G > C (p.Met1Ile) variant that was previously reported to be a possible founder variant in Chinese, and 3 patients with urogenital PGL and 1 patient with retroperitoneal PGL who carried different SDHB variants. Variant carriers were younger, more likely to present with multiple tumours, or have family history of paraganglioma or pheochromocytoma, than non- variant carriers.

CONCLUSION

Hereditary PGL/PCC accounts for only 0.6% of patients seen in an adult cancer genetics clinic in Asia. SDHD and SDHB genes remain the most important causative genes of hereditary PGL/PCC in Asia even when patients are tested with multi-gene NGS panel.

One genotype, many phenotypes: SDHB p.R90X mutation-associated paragangliomas

CONTEXT

SDHB p.R90X germline mutation is the most common genetic alteration in our patients with familial or apparently sporadic pheochromocytoma/paraganglioma (PPGL).

OBJECTIVE

To analyze the clinical and pathological characteristics, response to therapy, and outcome of patients with SDHB p.R90X-associated PPGL and describe the clinical phenotypic variability in the patients carrying this mutation.

METHODS

We reviewed the clinical and pathological characteristics and analyzed the phenotypic variability of all 13 patients that have SDHB p.R90X mutation-associated PPGL.

RESULTS

Thirteen patients (five females and eight males). The median age at diagnosis was 23 years (range 8-43). Although the mutation was the same, there was significant phenotypic variability between patients and even within the same family. Four patients (30.8%) had a family history of PPGL and six patients (46%) had distant metastasis. Surgery of the primary tumor was performed in 11 patients (84.6%). Two patients had inoperable PPGL. Patients with metastasis received different combinations of chemotherapy, Lu¹⁷⁷ radiotherapy, multikinase inhibitors, and external irradiation. Only five patients (38.5%) were in remission at a follow-up duration of 4-9 years. The other patients either died due to their disease progression (four patients, 30.8%) or continue to have progressive disease (two patients, 15.4%) or recurrence (one patient, 7.7%). Patients with distant metastasis were older, had larger primary tumors, were more likely to have a family history of PPGL and had a worse outcome.

CONCLUSION

SDHB p.R90X mutation-associated PPGL have significant phenotypic variability and are associated with a high risk of distant metastasis and mortality.

Molecular characterization of CNS paragangliomas identifies cauda equina paragangliomas as a distinct tumor entity

Paragangliomas/pheochromocytomas are rare neuroendocrine tumors that arise from the adrenal gland or ganglia at various sites throughout the body. They display a remarkable diversity of driver alterations and are associated with germline mutations in up to 40% of the cases. Comprehensive molecular profiling of abdomino-thoracic paragangliomas revealed four molecularly defined and clinically relevant subtypes. Paragangliomas of the cauda equina region are considered to belong to one of the defined molecular subtypes, but a systematic molecular analysis has not yet been performed. In this study, we analyzed genome-wide DNA methylation profiles of 57 cauda equina paragangliomas and show that these tumors are epigenetically distinct from non-spinal paragangliomas and other tumors. In contrast to paragangliomas of other sites, chromosomal imbalances are widely lacking in cauda equina paragangliomas. Furthermore, RNA and DNA exome sequencing revealed that frequent genetic alterations found in non-spinal paragangliomas—including the prognostically relevant SDH mutations—are absent in cauda equina paragangliomas. Histologically, cauda equina paragangliomas show frequently gangliocytic differentiation and strong immunoreactivity to pan-cytokeratin and cytokeratin 18, which is not common in paragangliomas of other sites. None of our cases had a familial paraganglioma syndrome. Tumors rarely recurred (9%) or presented with multiple lesions within the spinal compartment (7%), but did not metastasize outside the CNS. In summary, we show that cauda equina paragangliomas represent a distinct, sporadic tumor entity defined by a unique clinical and morpho-molecular profile.

A Comprehensive Proteomics Analysis of the JC Virus (JCV) Large and Small Tumor Antigen Interacting Proteins: Large T Primarily Targets the Host Protein Complexes with V-ATPase and Ubiquitin Ligase Activities While Small t Mostly Associates with Those Having Phosphatase and Chromatin-Remodeling Functions

The oncogenic potential of both the polyomavirus large (LT-Ag) and small (Sm t-Ag) tumor antigens has been previously demonstrated in both tissue culture and animal models. Even the contribution of the MCPyV tumor antigens to the development of an aggressive human skin cancer, Merkel cell carcinoma, has been recently established. To date, the known primary targets of these tumor antigens include several tumor suppressors such as pRb, p53, and PP2A. However, a comprehensive list of the host proteins targeted by these proteins remains largely unknown. Here, we report the first interactome of JCV LT-Ag and Sm t-Ag by employing two independent “affinity purification/mass spectroscopy” (AP/MS) assays. The proteomics data identified novel targets for both tumor antigens while confirming some of the previously reported interactions. LT-Ag was found to primarily target the protein complexes with ATPase (v-ATPase and Smc5/6 complex), phosphatase (PP4 and PP1), and ligase (E3-ubiquitin) activities. In contrast, the major targets of Sm t-Ag were identified as Smarca1/6, AIFM1, SdhA/B, PP2A, and p53. The interactions between “LT-Ag and SdhB”, “Sm t-Ag and Smarca5”, and “Sm t-Ag and SDH” were further validated by biochemical assays. Interestingly, perturbations in some of the LT-Ag and Sm t-Ag targets identified in this study were previously shown to be associated with oncogenesis, suggesting new roles for both tumor antigens in novel oncogenic pathways. This comprehensive data establishes new foundations to further unravel the new roles for JCV tumor antigens in oncogenesis and the viral life cycle.

Targeting pheochromocytoma/paraganglioma with polyamine inhibitors

BACKGROUND

Pheochromocytomas (PCCs) and paragangliomas (PGLs) are neuroendocrine tumors that are mostly benign. Metastatic disease does occur in about 10% of cases of PCC and up to 25% of PGL, and for these patients no effective therapies are available. Patients with mutations in the succinate dehydrogenase subunit B (SDHB) gene tend to have metastatic disease. We hypothesized that a down-regulation in the active succinate dehydrogenase B subunit should result in notable changes in cellular metabolic profile and could present a vulnerability point for successful pharmacological targeting.

METHODS

Metabolomic analysis was performed on human hPheo1 cells and shRNA SDHB knockdown hPheo1 (hPheo1 SDHB KD) cells. Additional analysis of 115 human fresh frozen samples was conducted. In vitro studies using N¹,N¹¹-diethylnorspermine (DENSPM) and N¹,N¹²- diethylspermine (DESPM) treatments were carried out. DENSPM efficacy was assessed in human cell line derived mouse xenografts.

RESULTS

Components of the polyamine pathway were elevated in hPheo1 SDHB KD cells compared to wild-type cells. A similar observation was noted in SDHx PCC/PGLs tissues compared to their non-mutated counterparts. Specifically, spermidine, and spermine were significantly elevated in SDHx-mutated PCC/PGLs, with a similar trend in hPheo1 SDHB KD cells. Polyamine pathway inhibitors DENSPM and DESPM effectively inhibited growth of hPheo1 cells in vitro as well in mouse xenografts.

CONCLUSIONS

This study demonstrates overactive polyamine pathway in PCC/PGL with SDHB mutations. Treatment with polyamine pathway inhibitors significantly inhibited hPheo1 cell growth and led to growth suppression in xenograft mice treated with DENSPM. These studies strongly implicate the polyamine pathway in PCC/PGL pathophysiology and provide new foundation for exploring the role for polyamine analogue inhibitors in treating metastatic PCC/PGL. PRéCIS: Cell line metabolomics on hPheo1 cells and PCC/PGL tumor tissue indicate that the polyamine pathway is activated. Polyamine inhibitors in vitro and in vivo demonstrate that polyamine inhibitors are promising for malignant PCC/PGL treatment. However, further research is warranted.

Epidural anesthesia and hypotension in pheochromocytoma and paraganglioma

Postoperative hypotension frequently occurs after resection of pheochromocytoma and/or paraganglioma (PPGLs). Epidural anesthesia (EA) is often used for pain control in open resection of these tumors; one of its side effects is hypotension. Our aim is to determine if EA is associated with an increased risk of postoperative hypotension after open resection of PPGLs. We conducted a retrospective review of patients who underwent open resection of PPGLs at the National Institutes of Health from 2004 to 2019. Clinical and perioperative parameters were analyzed by the use of EA. The primary endpoint was postoperative hypotension. Ninety-seven patients (46 female and 51 male; mean age, 38.5 years) underwent open resection of PPGLs and 69 (71.1%) received EA. Patients with EA had a higher rate beta-blocker use (79.7% vs 57.1%, P = 0.041), metastasis (69.6% vs 39.3%, P = 0.011), and were more frequently hypotensive after surgery (58.8% vs 25.0%, P = 0.003) compared to those without EA. Patients with postoperative hypotension had higher plasma normetanephrines than those without (7.3 fold vs 4.1 fold above the upper limit of normal, P = 0.018). Independent factors associated with postoperative hypotension include the use of beta-blockers (HR = 3.35 (95% CI: 1.16-9.67), P = 0.026) and EA (HR = 3.49 (95% CI: 1.25-9.76), P = 0.017). Data from this retrospective study suggest that, in patients with open resection of PPGLs, EA is an independent risk factor for early postoperative hypotension. Special caution is required in patients on beta-blockade. A prospective evaluation with standardized protocols for the use of EA and management of hemodynamic variability is necessary.

HEREDITARY ENDOCRINE TUMOURS: CURRENT STATE-OF-THE-ART AND RESEARCH OPPORTUNITIES: Metastatic pheochromocytomas and paragangliomas: proceedings of the MEN2019 workshop

Pheochromocytomas and paragangliomas (PPGLs) are adrenal or extra-adrenal autonomous nervous system-derived tumors. Most PPGLs are benign, but approximately 15% progress with metastases (mPPGLs). mPPGLs are more likely to occur in patients with large pheochromocytomas, sympathetic paragangliomas, and norepinephrine-secreting tumors. Older subjects, those with larger tumors and synchronous metastases, advance more rapidly. Germline mutations of SDHB, FH, and possibly SLC25A11, or somatic MAML3 disruptions relate to a higher risk for metastatic disease. However, it is unclear whether these mutations predict outcome. Once diagnosed, there are no well-established predictors of outcome in mPPGLs, and aggressive tumors have few therapeutic options and limited response. High-specific activity (HSA) metaiodine-benzyl-guanidine (MIBG) is the first FDA approved treatment and shows clinical effectiveness for MIBG-avid mPPGLs. Ongoing and future investigations should involve validation of emerging candidate outcome biomarkers, including somatic ATRX, TERT, and microRNA disruptions and identification of novel prognostic indicators. Long-term effect of HSA-MIBG and the role of other radiopharmaceuticals should be investigated. Novel trials targeting molecular events prevalent in SDHB/FH mutant tumors, such as activated hypoxia inducible factor 2 (HIF2), angiogenesis, or other mitochondrial defects that might confer unique vulnerability to these tumors should be developed and initiated. As therapeutic options are anticipated to expand, multi-institutional collaborations and well-defined clinical and molecular endpoints will be critical to achieve higher success rates in improving care for patients with mPPGLs.

Paraganglioma of the spermatic cord: report of one case and review of literature

Extra-adrenal paraganglioma is rare, and occurs in the retroperitoneum, and head and neck. The incidence rate of paraganglioma in urogenital system is very low, especially in the spermatic cord. A case of paraganglioma of spermatic cord is reported and relevant literature is reviewed. A spermatic cord mass was found in the right scrotum in a middle-aged man 2 years ago, without hormone symptoms. Understanding of clinical and intraoperative frozen pathology was inadequate. Ultrasound images showed that there was abundant blood supply around the right spermatic cord with clear boundaries. The conventional pathology of the tumor presented a typical histologic morphology of paraganglioma. Immunohistochemistry showed that chief tumor cells were CGA (+), syn (+), CD56 (+), SDHB (+), and sertoli cells were S-100 (strong+). There are few reported cases at present, and the etiology and pathogenesis are not clear yet. The rapid frozen pathologic diagnosis during operation is very challenging, and it is easily diagnosed by routine histology combined with immunohistochemistry. Gene detection is recommended if necessary. Early diagnosis is helpful to the choice of operation mode and the prevention and control of intraoperative risk.

Pheochromocytoma and Paraganglioma in Children and Adolescents: Experience of the French Society of Pediatric Oncology (SFCE)

Purpose

The purpose of this work is to assess the clinical outcome of pediatric patients diagnosed with pheochromocytoma and paraganglioma (PPGL) detected in France since 2000.

Methods

A retrospective multicenter study was conducted that included all patients younger than 18 years with PPGL diagnosed in France between 2000 and 2016. Patients were identified from 4 different sources: the National Registry of Childhood Solid Tumors, the French Pediatric Rare Tumors Database, the French registry of succinate dehydrogenase (SDH)-related hereditary paraganglioma, and the nationwide TenGen network.

Results

Among 113 eligible patients, 81 children with available data were enrolled (41 with adrenal and 40 with extra-adrenal PPGL). At diagnosis, 11 had synchronous metastases. After a median follow-up of 53 months, 27 patients experienced a new event (n = 7 second PPGL, n = 1 second paraganglioma [PGL], n = 8 local recurrences, n = 10 metastatic relapses, n = 1 new tumor) and 2 patients died of their disease. The 3- and 10-year event-free survival rates were 80% (71%-90%) and 39% (20%-57%),respectively, whereas the overall survival rate was 97% (93%-100%)at 3 and 10 years. A germline mutation in one PPGL-susceptibility gene was identified in 53 of the 68 (77%) patients who underwent genetic testing (SDHB [n = 25], VHL [n = 21], RET [n = 2], HIF2A [n = 2], SDHC [n = 1], SDHD [n = 1], NF1 [n = 1]). Incomplete resection and synchronous metastases were associated with higher risk of events (P = .011, P = .004), but presence of a germline mutation was not (P = .11).

Conclusions

Most pediatric PPGLs are associated with germline mutations and require specific follow-up because of the high risk of tumor recurrence.