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Phaeochromocytomas and paragangliomas are rare neuroendocrine tumours. So far, over 20 causative genes have been identified, of which the most frequent and strongest indicator for malignancies are mutations in succinate dehydrogenase subunit B. No curative therapy is available for patients with metastases resulting in poor prognosis. Therapy development has been hindered by lack of suitable model systems. The succinate dehydrogenase complex is located in the inner membrane of the mitochondria and plays a crucial role in the oxidative phosphorylation chain and the tricarboxylic acid-cycle. Succinate dehydrogenase deficiency results in accumulation of the oncometabolite succinate inducing hypoxia inducible factor stabilization, deoxyribonucleic acid and histone methylation inhibition, and impaired production of adenosine triphosphate. It remains unknown which combination of pathways and/or triggers are decisive for metastases development. In this review, the role of mitochondria in malignant succinate dehydrogenase subunit B-associated phaeochromocytomas and paragangliomas and implications for mitochondria as therapeutic target are discussed., (Copyright © 2021 The Authors. Published by Elsevier Ltd.. All rights reserved.)

Purpose: Pheochromocytomas/paragangliomas (PHEOs/PGLs) are rare in children with only a few SDHB mutation-related cases. Previous studies on children were conducted in small cohorts. This large set of pediatric patients provides robust data in the evaluation of clinical outcomes., Methods: Sixty-four pediatric PHEO/PGL patients with SDHB germline mutations were included in the present study. The clinical presentation, disease course, and survival rate were evaluated., Results: Thirty-eight males and 26 females were diagnosed with PHEO/PGL at a median age of 13 years. The majority of patients displayed norepinephrine hypersecretion and 73.44% initially presented with a solitary tumor. Metastases developed in 70% of patients at the median age of 16 years and were mostly diagnosed first 2 years and in years 12-18 post-diagnosis. The presence of metastases at the time of diagnosis had a strong negative impact on survival in males but not in females. The estimated 5-, 10-, and 20-year survival rates were 100%, 97.14%, and 77.71%, respectively., Conclusion: The present report has highlighted several important aspects in the management of pediatric patients with SDHB mutations associated-PHEO/PGL. Initial diagnostic evaluation of SDHB mutation carriers should be started at age of 5-6 years with initial work-up focusing on abdominal region. Thorough follow-up is crucial first 2 years post-diagnosis and more frequent follow-ups are needed in years 10-20 post-diagnosis due to the increased risk of metastases. Although this age group developed metastasis as early as 5 years from diagnosis, we have shown that the overall 20-year prognosis and survival are good.

Succinate dehydrogenase (SDH), also named as complex II or succinate:quinone oxidoreductases (SQR) is a critical enzyme in bioenergetics and metabolism. This is because the enzyme is located at the intersection of oxidative phosphorylation and tricarboxylic acid cycle (TCA); the two major pathways involved in generating energy within cells. SDH is composed of 4 subunits and is assembled through a multi-step process with the aid of assembly factors. Not surprisingly malfunction of this enzyme has marked repercussions in metabolism leading to devastating tumors such as paraganglioma and pheochromocytoma. It is already known that mutations in the genes encoding subunits lead to tumorigenesis, but recent discoveries have indicated that mutations in the genes encoding the assembly factors also contribute to tumorigenesis. The mechanisms of pathogenesis of tumorigenesis have not been fully understood. However, a multitude of signaling pathways including succinate signaling was determined. We, here discuss how defective SDH may lead to tumor development at the molecular level and describe how yeast, as a model system, has contributed to understanding the molecular pathogenesis of tumorigenesis resulting from defective SDH., (Copyright © 2019 Elsevier GmbH. All rights reserved.)

Purpose: Phosphoinositide-dependent kinase 1 (PDK1) is highly expressed in many solid tumors. And several studies have demonstrated that PDK1 has been an emerging and promising target for anti-cancer therapies. However, the role of PDK1 has not been studied so far in malignant pheochromocytoma (PCC)., Methods: In this study, immunohistochemical staining was performed to investigate the protein level of PDK1 in 63 PCC tissue samples, of which 49 were benign and 14 were malignant. In addition, we evaluated the effect of inhibition of PDK1 with siRNA on cell growth, apoptosis and invasive capacity in PC12 cells and identified the underlying mechanisms., Results: We found that PDK1 was overexpressed in malignant PCC tissues, and knockdown of PDK1 with siRNA significantly inhibited cell proliferation, increased apoptosis induction, and attenuated cell migration and invasive capacity in PC12 cells. We also showed that knockdown of PDK1 significantly reduced the phosphorylation of Akt at threonine 308 (p-Akt T308) but did not alter the serine phosphorylation of Akt on the S473 site (p-Akt S473). Furthermore, we found that the p-Akt expression was noticeably decreased after knockdown of PDK1, but the t-Akt expression did not show a significant decrease., Conclusion: We have demonstrated for the first time that PDK1 is overexpressed in human malignant PCC and plays an important role in the malignant biological behaviors of PC12 cell. Specifically, we have revealed that knockdown of PDK1 could attenuate activation of the Akt signaling. These data suggest that PDK1 could be a new promising potential therapeutic target in human cancer treatment for malignant PCC.

Pheochromocytoma (PC) and paraganglioma (PGL) are rare neuroendocrine tumors that occur throughout the body from the base of the skull to the pelvis. Sympathetic catecholamine-secreting tumors may be associated with hyperadrenergic symptoms and long-term morbidity if they are untreated. Typically biochemically silent, head and neck PGLs may result in cranial nerve palsies and symptoms due to localized mass effect. Tumors can arise sporadically or as part of an inheritable PC-PGL syndrome. Up to 40% of tumors are recognized to be associated with germline mutations in an increasing array of susceptibility genes, including those that appear to arise sporadically. Most commonly, up to 25% of all PC-PGLs are associated with mutations in one of the succinate dehydrogenase (SDH) enzyme subunit genes. The resulting familial PC-PGL syndrome varies according to the affected enzyme subunit (most commonly SDHB and SDHD mutations) with respect to tumor prevalence, location, age of onset, and risk of malignancy. Patients with SDH enzyme mutations have increased lifetime risk of developing multifocal tumors and malignancy. Early recognition of individuals at high risk, genetic testing, screening of family members, and lifelong surveillance programs are recommended, but not without health, economic, and psychologic implications. Anatomic and functional imaging is key to diagnosis, staging, treatment planning, and lifelong surveillance of these individuals. Radiologists must be aware of the imaging appearance of these varied tumors. © RSNA, 2019.

Humans are constantly exposed to a multitude of environmental chemicals that may disturb endocrine functions. It is crucial to identify such chemicals and uncover their mode-of-action to avoid adverse health effects. 11β-hydroxylase (CYP11B1) and aldosterone synthase (CYP11B2) catalyze the formation of cortisol and aldosterone, respectively, in the adrenal cortex. Disruption of their synthesis by exogenous chemicals can contribute to cardio-metabolic diseases, chronic kidney disease, osteoporosis, and immune-related disorders. This study applied in silico screening and in vitro evaluation for the discovery of xenobiotics inhibiting CYP11B1 and CYP11B2. Several databases comprising environmentally relevant pollutants, chemicals in body care products, food additives and drugs were virtually screened using CYP11B1 and CYP11B2 pharmacophore models. A first round of biological testing used hamster cells overexpressing human CYP11B1 or CYP11B2 to analyze 25 selected virtual hits. Three compounds inhibited CYP11B1 and CYP11B2 with IC 50 values below 3 μM. The most potent inhibitor was epoxiconazole (IC 50 value of 623 nM for CYP11B1 and 113 nM for CYP11B2, respectively); flurprimidol and ancymidol were moderate inhibitors. In a second round, these three compounds were tested in human adrenal H295R cells endogenously expressing CYP11B1 and CYP11B2, confirming the potent inhibition by epoxiconazole and the more moderate effects by flurprimidol and ancymidol. Thus, the in silico screening, prioritization of chemicals for initial biological tests and use of H295R cells to provide initial mechanistic information is a promising strategy to identify potential endocrine disruptors inhibiting corticosteroid synthesis. A critical assessment of human exposure levels and in vivo evaluation of potential corticosteroid disrupting effects by epoxiconazole is required., (Copyright © 2019. Published by Elsevier Ltd.)

The mitochondrial enzyme succinate dehydrogenase (SDH) acts as a tumor suppressor. Biallelic inactivation of one of the genes encoding for SDH subunits (collectively named SDHx) leads to complete loss of the protein function and the development of diverse group of tumors. Pheochromocytomas-paragangliomas are the prime example of hereditary tumors caused by SDH deficiency. In this review, we discuss the roles of imaging examinations, and illustrate new insights into genotype-imaging phenotype relationships., Competing Interests: The authors declare that they have no conflict of interest., (© Georg Thieme Verlag KG Stuttgart · New York.)

In chromaffin cells, tyrosine hydroxylase (TH), aromatic L-amino acid decarboxylase (AADC), dopamine β-hydroxylase (DBH), and phenylethanolamine N-methyltransferase (PNMT) are mainly involved in catecholamine synthesis. In this study, we evaluated the association between the status of catecholamine-synthesizing enzymes and histopathological features of pheochromocytoma and extraadrenal paraganglioma with special emphasis upon their postoperative clinical behavior. Immunohistochemical evaluation of TH, DBH, AADC, PNMT, Ki 67, and S-100 was performed in 29 pheochromocytoma and 10 extraadrenal paraganglioma and one lymph node harboring metastatic pheochromocytoma. Among these cases, metastasis was subsequently developed in three cases. Urinary normetanephrine (U-NM) levels were significantly higher in clinical metastatic cases than non-metastatic ones. Ki 67 labeling index was significantly higher in both clinical metastatic cases and the Adrenal Gland Scaled Score (PASS) score of ≧ 4 cases than PASS < 4 cases, although this score was originally used in pheochromocytoma. H-score of AADC and DBH were significantly lower in PASS ≧ 4 cases than those with < 4 cases, and in the cases associated with intratumoral necrosis (n = 4), the presence of spindle shaped tumor cells (n = 4), and large nests of cells or diffuse growth (n = 5). Lower status of intratumoral AADC could be related to poor differentiation of tumor cells in both catecholamine production and morphology and could be related to aggressive biological behavior of both pheochromocytoma and extraadrenal paraganglioma.

Hypoxia is a primary factor in many pathological conditions. Hypoxic cell death is commonly attributed to metabolic failure and oxidative injury. cAMP-dependent protein kinase A (PKA) is activated in hypoxia and regulates multiple enzymes of the mitochondrial electron transport chain, thus may be implicated in cellular energy depletion and hypoxia-induced cell death. Wild type (WT) PC-12 cells and PKA activity-deficient 123.7 PC-12 cells were exposed to 3, 6, 12 and 24h hypoxia (0.1% or 5% O 2 ). Hypoxia, at 24h 0.1% O 2 , induced cell death and increased reactive oxygen species (ROS) in WT PC-12 cells. Despite lower ATP levels in normoxic 123.7 cells than in WT cells, hypoxia only decreased ATP levels in WT cells. However, menadione-induced oxidative stress similarly affected both cell types. While mitochondrial COX IV expression remained consistently higher in 123.7 cells, hypoxia decreased COX IV expression in both cell types. N-acetyl cysteine antioxidant treatment blocked hypoxia-induced WT cell death without preventing ATP depletion. Transient PKA catα expression in 123.7 cells partially restored hypoxia-induced ROS but did not alter ATP levels or COX IV expression. We conclude that PKA signaling contributes to hypoxic injury, by regulating oxidative stress rather than by depleting ATP levels. Therapeutic strategies targeting PKA signaling may improve cellular adaptation and recovery in hypoxic pathologies., (Copyright © 2017 Elsevier B.V. All rights reserved.)

Ganglioneuromas represent the most well-differentiated spectrum of neoplasia arising from the sympathetic nervous system, while neuroblastomas represent the most poorly differentiated counterpart, and ganglioneuroblastomas represent intermediate stages of differentiation. Small series of cases have documented the co-occurrence of ganglioneuroma with a pheochromocytoma (Pheo)/paraganglioma (PGL) component. We report the clinicopathologic features of eight such cases, diagnosed between 2003 and 2015 with a mean follow-up of 22 months (1-47), which were evaluated for syndrome associations, SDHB expression, and clinical outcome. Mutations of the succinate dehydrogenase (SDH) complex subunits (A, B, C, D, and SDHAF2) have been implicated in predicting metastatic behavior and in identifying possible paraganglioma syndromes. The proliferative index was calculated by manual quantification of Ki-67-positive cells at selected hot-spots using ImageJ (NIH). In our series, composite Pheo/PGL-ganglioneuromas predominantly involved the adrenal gland (Pheo 7, PGL 1). The cases had an equal gender distribution (males 4, females 4), with a mean age at diagnosis of 67 years (range 53 to 86 years), an average size of 5.2 cm (range 2 to 8.2 cm), an average weight of 49.3 g (7.8 to 144.7 g, n = 6), and the majority were functionally active (7 of 8, 88%). The mean Ki67 proliferation rate was 2% (range 0.3 to 3%), and all cases retained SDHB expression (8/8, 100%). No patient (0/8, 0%) developed metastatic disease on follow-up. One patient had a retroperitoneal composite PGL-ganglioneuroma in the setting of neurofibromatosis type 1. No recurrent disease or other associations were identified. In our study, composite Pheo/PGL-ganglioneuromas predominantly affected the adrenal gland in older patients, showed no loss of SDHB, and no disease recurrence was identified.

MicroRNAs (miRNAs) play an important role in multiple biological processes, and many miRNAs have been shown to regulate cell proliferation and apoptosis. In this study, we investigated the role of miR-15b-5p in cell proliferation and apoptosis in PC12 cells. We found that overexpression of miR-15b-5p could decrease cell proliferation and induce apoptosis and cytotoxic activities in PC12 cells. Bioinformatics analysis and luciferase activities assays showed that miR-15b-5p might target extracellular signal-regulated kinase 1 (ERK1) by binding to its 3'-untranslated region (3'-UTR). Moreover, we also found that overexpression of ERK1 could attenuate the effects of miR-15b-5p in PC12 cells. Finally, our results suggest that miR-15b-5p might inhibit cell proliferation and induce apoptosis in PC12 cells by targeting ERK1., (Copyright © 2017 Elsevier Masson SAS. All rights reserved.)

Oxidative stress has been implicated in the pathogenesis of many kinds of neurodegenerative disorders, particularly Parkinson's disease. Quercetin is a bioflavonoid found ubiquitously in fruits and vegetables, and has antioxidative activity. However, the underlying mechanism of the antioxidative effect of quercetin in neurodegenerative diseases has not been well explored. Here, we investigated the antioxidative effect and underlying molecular mechanisms of quercetin on PC-12 cells. We found that PC-12 cells pretreated with quercetin exhibited an increased cell viability and reduced lactate dehydrogenase (LDH) release when exposed to hydrogen peroxide (H₂O₂). The significantly-alleviated intracellular reactive oxygen species (ROS), malondialdehyde (MDA), and lipoperoxidation of the cell membrane of PC-12 cells induced by H₂O₂ were observed in the quercetin pretreated group. Furthermore, quercetin pretreatment markedly reduced the apoptosis of PC-12 cells and hippocampal neurons. The inductions of antioxidant enzyme catalase (CAT), superoxide dismutase (SOD), and glutathione peroxidase (GSH-Px) in PC-12 cells exposed to H₂O₂ were significantly reduced by preatment with quercetin. In addition, quercetin pretreatment significantly increased Bcl-2 expression, and reduced Bax, cleaved caspase-3 and p53 expressions. In conclusion, this study demonstrated that quercetin exhibited a protective effect against oxidative stress-induced apoptosis in PC-12 cells. Our findings suggested that quercetin may be developed as a novel therapeutic agent for neurodegenerative diseases induced by oxidative stress., Competing Interests: The authors declare no conflict of interest.

This study aims to examine the expression profiles of the miR-183 cluster (miR-96/182/183) in pheochromocytoma. Pheochromocytoma tissues were prospectively collected from 50 patients with pheochromocytoma. Expression of miR-183 cluster members and SDHB protein expression were analyzed in these tissues by quantitative real-time polymerase chain reaction and immunohistochemistry, respectively. The expression of miR-183 cluster members in pheochromocytomas was correlated with the clinical and pathological parameters of these patients. The expression levels of miR-183 cluster members were predominantly downregulated or deleted in pheochromocytoma. Low expression or deletion of miR-96 was predominantly noted in younger patients with pheochromocytoma (<50 years, P=.01). Female patients in the study group showed marked deletion of miR-182 (P=.05). Deletion of the cluster was also associated with SDHB protein expression in pheochromocytoma. Moreover, patients with low miR-183 cluster expression had a slightly better survival rate when compared with patients with high expression. To conclude, the findings indicate a role for miR-183 cluster members in the pathogenesis and clinical progression of pheochromocytoma., (Copyright © 2017 Elsevier Inc. All rights reserved.)

Hepatoid adenocarcinoma is a rare extrahepatic tumor, which shows morphological and immunohistochemical similarities to hepatocellular carcinoma (HCC). Hence, hepatoid adenocarcinoma can cause diagnostic confusion with HCC. Arginase-1 immunostain has been recently shown to be an excellent marker of normal hepatocytes and is a sensitive and specific marker for HCC. However, the expression of Arginase-1 in hepatoid adenocarcinoma has not been evaluated in detail. Eight cases of hepatoid adenocarcinoma were immunostained with Arginase-1, Hepar-1, Glypican-3, CK7, CK20, CK19, polyclonal carcinoembryonic antigen, ɑ-fetoprotein, CDX2, and TTF-1. Albumin in situ hybridization was performed in 4 cases. All 8 cases were positive for Hepar-1. Arginase-1 was positive in 5 (62.5%) of 8 cases; 2 of these cases showed diffuse staining, while 3 showed patchy staining. Glypican-3, CK7 and ɑ-fetoprotein were each positive in 4 (50%) of 8 cases. CK19 was positive in 3 (37.5%) of 8 cases. polyclonal carcinoembryonic antigen showed canalicular staining in 3 (37.5%) of 8 cases and albumin in situ hybridization was positive in 3 (75%) of 4 cases. CDX2 was positive in 2 (25%) of 8 cases, both arising from the stomach. CK20 was positive in 1 (12.5%) of 8 case while TTF-1 was negative in all cases. Hepatoid adenocarcinoma has a similar immunostaining profile as HCC. Arginase-1 expression is common (62.5%) in hepatoid adenocarcinoma and hence it is not useful in distinguishing HCC from hepatoid adenocarcinoma., (Copyright © 2016 Elsevier Inc. All rights reserved.)

Background and Objective: Multiple Endocrine Neoplasia type 2 (MEN2) is a rare genetic disorder characterized by medullary thyroid carcinoma (MTC), pheochromocytoma and primary hyperparathyroidism. MEN2 is an autosomal dominant syndrome caused by mutations in the RET proto-oncogene. In the vast majority of patients, the mutations are localized in exons 10, 11 and 13-15 of the RET gene. Rare variants located in exon 8 were recently identified but their clinical significance remains unclear., Design and Methods: We studied two sisters presenting with pheochromocytoma as the first tumor. One of the sisters was diagnosed with a right pheochromocytoma at the age of 44 and at age 53 she developed an invasive left pheochromocytoma with no other endocrine neoplasia. The other sister was diagnosed with a left pheochromocytoma at age 50 and at age 64 she had a right phemochromocytoma and MTC. Neither of the two sisters presented evidence of primary hyperparathyroidism. Mutations of the RET proto-oncogene were investigated by DNA sequencing., Results: We detected a germline missense variant in RET exon 8 (p.Cys531Arg) in both sisters. The p.Cys531Arg variant was not present in a third 50-year-old sister who has remained to date clinically unaffected., Conclusion: This is the first case showing the p.Cys531Arg variant in RET exon 8 co-segregating with family members affected by a syndrome reminiscent of MEN2A. Our results suggest that this variant has a specific genotype-phenotype correlation as it is associated with the development of pheochromocytoma before the onset of MTC.

Malignant pheochromocytoma/paraganglioma (PCC/PGL) is defined by the presence of metastases at non-chromaffin sites, which makes it difficult to prospectively diagnose malignancy. Here, we performed array CGH (aCGH) and paired gene expression profiling of fresh, frozen PCC/PGL samples (n = 12), including three malignant tumors, to identify genes that distinguish benign from malignant tumors. Most PCC/PGL cases showed few copy number aberrations, regardless of malignancy status, but mRNA analysis revealed that 390 genes were differentially expressed in benign and malignant tumors. Expression of the enzyme, phenylethanolamine N-methyltransferase (PNMT), which catalyzes the methylation of norepinephrine to epinephrine, was significantly lower in malignant PCC/PGL as compared to benign samples. In 62 additional samples, we confirmed that PNMT mRNA and protein levels were decreased in malignant PCC/PGL using quantitative real-time polymerase chain reaction and immunohistochemistry. The present study demonstrates that PNMT downregulation correlates with malignancy in PCC/PGL and identifies PNMT as one of the most differentially expressed genes between malignant and benign tumors., Competing Interests: The authors have no conflicts of interest to disclose.

Germline mutations occur in up to 30-40% of pheochromocytoma/paraganglioma, with mutations in the succinate dehydrogenase (SDH) subunits B (SDHB) and D (SDHD) being the most common. Blood samples are favored for obtaining high quality DNA, however, leukocytes can also be obtained by collecting saliva. The aim of this study was to determine whether SDHB and SDHD gene mutations in patients with pheochromocytoma/paraganglioma could be determined using a salivary sample. Paired blood and salivary samples were collected from 30 patients: 9 SDHB mutation positive, 13 with a SDHD mutation, and 8 without any SDHx mutations. The Oragene DISCOVER kit was used to collect and extract DNA from saliva. Blood DNA was extracted from EDTA blood samples. The DNA purification and concentration were measured by spectrophotometry. The 8 exons of SDHB and the 4 exons of SDHD were amplified and sequenced by PCR-based bidirectional Sanger sequencing. Total DNA yields from blood DNA were similar to those obtained from saliva DNA [mean (±SD) saliva vs. blood DNA concentration 514.6 (±580.8) ng/µl vs. 360.9 (±262.7) ng/µl; p=0.2)]. The purity of the saliva DNA samples was lower than that of blood [mean OD260/OD280 ratio 1.78 (±0.13) vs. 1.87 (±0.04); p=0.001, respectively], indicating more protein contamination in the saliva-extracted DNA. This study shows that salivary DNA collected from patients with pheochromocytoma/paraganglioma is a good alternative for extraction of genomic DNA for its high DNA concentration and acceptable purity and can be used as an alternative to blood derived DNA in screening for SDHB and SDHD mutations., (© Georg Thieme Verlag KG Stuttgart · New York.)

Background: Intersecting a genome-wide expression profile of metastatic and nonmetastatic human neuroblastoma xenograft variants with expression profiles of tumours from stage 1 and 4 neuroblastoma patients, we previously characterised hexokinase 2 (HK2) as a gene whose expression was upregulated in both metastatic neuroblastoma variants and tumours from stage 4 neuroblastoma patients., Methods: Local and metastatic neuroblastoma cell variants as well as metastatic neuroblastoma cells genetically manipulated to downregulate the expression of HK2 were utilised for in vitro and in vivo examinations of the involvement of HK2 in neuroblastoma., Results: Hexokinase 2 expression and its activity levels were increased in neuroblastoma metastatic variants as compared with the local variants. The upregulation of HK2 confers upon the metastatic cells high resistance to the antiproliferative effect of the HK2 inhibitor 3-BrPa and to the chemotherapy agent Deferoxamine. The inhibition of HK2 transcript lowered the proliferation and motility of sh-HK2 cells as compared with sh-control cells. Mice that were inoculated with sh-HK2 cells had a lower incidence of local tumours, smaller tumour volumes and a diminished load of lung metastasis compared with mice inoculated with sh-control cells., Conclusions: Hexokinase 2 plays a significant role in shaping the malignant phenotype of neuroblastoma and influences the progression of this disease.

Context: Although adrenal vein sampling is the standard method to distinguish unilateral from bilateral forms of primary aldosteronism, it is an invasive and technically difficult procedure. (11)C-metomidate (MTO)-positron emission tomography was reported as a potential replacement for adrenal vein sampling. However, MTO has low selectivity for CYP11B2 over CYP11B1., Objective: This study aimed to determine the selectivity of (18)F-CDP2230, a new imaging agent, for CYP11B2 over CYP11B1 and determine whether the biodistribution profile of (18)F-CDP2230 is favorable for imaging CYP11B2., Methods: The IC50 of CDP2230 for the enzymatic activities of CYP11B2 and CYP11B1 was determined using cells with stable expression of either enzyme. In vitro autoradiography of human adrenal sections with aldosterone-producing adenomas was performed to confirm the specific binding ability of (18)F-CDP2230 to CYP11B2-expressing regions. Furthermore, positron emission tomography and magnetic resonance imaging were performed to evaluate the biodistribution of (18)F-CDP2230 in rats., Results: Although CDP2230 showed a significantly lower affinity for CYP11B2 and CYP11B1 than did MTO analogues, its selectivity for CYP11B2 over CYP11B1 was higher than that of MTO analogues. In vitro autoradiography revealed that the binding of (18)F-CDP2230 to CYP11B2-expressing regions in the adrenal gland was more specific than that of (123)I-IMTO. Moreover, the biodistribution study showed that (18)F-CDP2230 accumulated in adrenal glands with low background uptake., Conclusions: Our study showed a high selectivity of (18)F-CDP2230 for CYP11B2 over CYP11B1 with a favorable biodistribution for imaging CYP11B2. (18)F-CDP2230 is a promising imaging agent for detecting unilateral subtypes of primary aldosteronism.

Succinate dehydrogenase (SDH) and fumarate hydratase (FH) are tricarboxylic acid (TCA) cycle enzymes and tumor suppressors. Loss-of-function mutations give rise to hereditary paragangliomas/pheochromocytomas and hereditary leiomyomatosis and renal cell carcinoma. Inactivation of SDH and FH results in an abnormal accumulation of their substrates succinate and fumarate, leading to inhibition of numerous α-ketoglutarate dependent dioxygenases, including histone demethylases and the ten-eleven-translocation (TET) family of 5-methylcytosine (5 mC) hydroxylases. To evaluate the distribution of DNA and histone methylation, we used immunohistochemistry to analyze the expression of 5 mC, 5-hydroxymethylcytosine (5 hmC), TET1, H3K4me3, H3K9me3, and H3K27me3 on tissue microarrays containing paragangliomas/pheochromocytomas (n = 134) and hereditary and sporadic smooth muscle tumors (n = 56) in comparison to their normal counterparts. Our results demonstrate distinct loss of 5 hmC in tumor cells in SDH- and FH-deficient tumors. Loss of 5 hmC in SDH-deficient tumors was associated with nuclear exclusion of TET1, a known regulator of 5 hmC levels. Moreover, increased methylation of H3K9me3 occurred predominantly in the chief cell component of SDH mutant tumors, while no changes were seen in H3K4me3 and H3K27me3, data supported by in vitro knockdown of SDH genes. We also show for the first time that FH-deficient smooth muscle tumors exhibit increased H3K9me3 methylation compared to wildtype tumors. Our findings reveal broadly similar patterns of epigenetic deregulation in both FH- and SDH-deficient tumors, suggesting that defects in genes of the TCA cycle result in common mechanisms of inhibition of histone and DNA demethylases.

Metastatic pheochromocytoma continues to be an incurable disease, and treatment with conventional cytotoxic chemotherapy offers limited efficacy. In the present study, we evaluated a novel topoisomerase I inhibitor, LMP-400, as a potential treatment for this devastating disease. We found a high expression of topoisomerase I in human metastatic pheochromocytoma, providing a basis for the evaluation of a topoisomerase 1 inhibitor as a therapeutic strategy. LMP-400 inhibited the cell growth of established mouse pheochromocytoma cell lines and primary human tumor tissue cultures. In a study performed in athymic female mice, LMP-400 demonstrated a significant inhibitory effect on tumor growth with two drug administration regimens. Furthermore, low doses of LMP-400 decreased the protein levels of hypoxia-inducible factor 1 (HIF-1α), one of a family of factors studied as potential metastatic drivers in these tumors. The HIF-1α decrease resulted in changes in the mRNA levels of HIF-1 transcriptional targets. In vitro, LMP-400 showed an increase in the growth-inhibitory effects in combination with other chemotherapeutic drugs that are currently used for the treatment of pheochromocytoma. We conclude that LMP-400 has promising antitumor activity in preclinical models of metastatic pheochromocytoma and its use should be considered in future clinical trials.

In solid tumors, neoplastic cells grow in contact with the so-called tumor microenvironment. The interaction between tumor cells and the microenvironment causes reciprocal metabolic reprogramming and favorable conditions for tumor growth and metastatic spread. To obtain an experimental model resembling the in vivo conditions of the succinate dehydrogenase B subunit (SDHB)-mutated paragangliomas (PGLs), we evaluated the effects of SDHB silencing on metabolism and proliferation in the human neuroblastoma cell line (SK-N-AS), cultured alone or in association with human fibroblasts. Silencing caused a 70% decrease in protein expression, an almost complete loss of the complex specific enzymatic activity, and a significant increase in HIF1α and HIF2α expression; it thus resembled the in vivo tumor cell phenotype. When compared with WT SK-N-AS cells, SDHB-silenced cells showed an altered metabolism characterized by an unexpected significant decrease in glucose uptake and an increase in lactate uptake. Moreover, silenced cells exhibited a significant increase in cell proliferation and metalloproteinase activity. When co-cultured with human fibroblasts, control cells displayed a significant decrease in glucose uptake and a significant increase in cell proliferation as compared with their mono-cultured counterparts. These effects were even more evident in co-cultured silenced cells, with a 70% decrease in glucose uptake and a 92% increase in cell proliferation as compared to their mono-cultured counterparts. The present data indicate for the first time, to our knowledge, that SDHB impairment causes metabolic and functional derangement of neural-crest-derived tumor cells and that the microenvironment, here represented by fibroblasts, strongly affects their tumor metabolism and growth capacity., (© 2015 Society for Endocrinology.)

Mitochondrial dysfunction, due to mutations of the gene encoding succinate dehydrogenase (SDH), has been implicated in the development of adrenal phaeochromocytomas, sympathetic and parasympathetic paragangliomas, renal cell carcinomas, gastrointestinal stromal tumours and more recently pituitary tumours. Underlying mechanisms behind germline SDH subunit B (SDHB) mutations and their associated risk of disease are not clear. To investigate genotype-phenotype correlation of SDH subunit B (SDHB) variants, a homology model for human SDH was developed from a crystallographic structure. SDHB mutations were mapped, and biochemical effects of these mutations were predicted in silico. Results of structural modelling indicated that many mutations within SDHB are predicted to cause either failure of functional SDHB expression (p.Arg27*, p.Arg90*, c.88delC and c.311delAinsGG), or disruption of the electron path (p.Cys101Tyr, p.Pro197Arg and p.Arg242His). GFP-tagged WT SDHB and mutant SDHB constructs were transfected (HEK293) to determine biological outcomes of these mutants in vitro. According to in silico predictions, specific SDHB mutations resulted in impaired mitochondrial localisation and/or SDH enzymatic activity. These results indicated strong genotype-functional correlation for SDHB variants. This study reveals new insights into the effects of SDHB mutations and the power of structural modelling in predicting biological consequences. We predict that our functional assessment of SDHB mutations will serve to better define specific consequences for SDH activity as well as to provide a much needed assay to distinguish pathogenic mutations from benign variants., (© 2015 Society for Endocrinology.)