The Evolving Role of Succinate in Tumor Metabolism: An 18 F-FDG–Based Study: succinate and [18F]-FDG.

International audienceIn recent years, inherited and acquired mutations in the tricarboxylic acid (TCA) cycle enzymes have been reported in diverse cancers. Pheochromocytomas and paragangliomas often exhibit dysregula-tion of glucose metabolism, which is also driven by mutations in genes encoding the TCA cycle enzymes or by activation of hypoxia signaling. Pheochromocytomas and paragangliomas associated with succinate dehydrogenase (SDH) deficiency are characterized by high 18 F-FDG avidity. This association is currently only partially explained. Therefore, we hypothesized that accumulation of succi-nate due to the TCA cycle defect could be the major connecting hub between SDH-mutated tumors and the 18 F-FDG uptake profile. Methods: To test whether succinate modifies the 18 F-FDG metabolic profile of tumors, we performed in vitro and in vivo (small-animal PET/CT imaging and autoradiography) experiments in the presence of succinate, fumarate, and phosphate-buffered saline (PBS) in different cell models. As a control, we also evaluated the impact of succinate on 18 F-fluorocholine uptake and retention. Glucose transporter 1 (GLUT1) immunohistochemistry was performed to assess whether 18 F-FDG uptake correlates with GLUT1 staining. Results: Intratumoral injection of succinate significantly increased 18 F-FDG uptake at 24 h on small-animal PET/CT imaging and au-toradiography. No effect of succinate was observed on cancer cells in vitro, but interestingly, we found that succinate caused increased 18 F-FDG uptake by human umbilical vein endothelial cells in a concentration-dependent manner. No significant effect was observed after intratumoral injection of fumarate or PBS. Succinate, fumarate, and PBS have no effect on cell viability, regardless of cell lineage. Intramuscular injection of succinate also significantly increases 18 F-FDG uptake by muscle when compared with either PBS or fumarate, highlighting the effect of succinate on connective tissues. No difference was observed between PBS and succinate on 18 F-fluorocholine uptake in the tumor and muscle and on hind limb blood flow. GLUT1 expression quantification did not significantly differ between the study groups. Conclusion: The present study shows that succinate stimulates 18 F-FDG uptake by endothelial cells, a finding that partially explains the 18 F-FDG metabotype observed in tumors with SDH deficiency. Although this study is an 18 F-FDG–based approach, it provides an impetus to better characterize the determinants of 18 F-FDG uptake in various tumors and their surrounding microenvironment, with a special emphasis on the role of tumor-specific oncometabolite

Lymph node thyroglobulin in the diagnosis of metastases of thyroid carcinoma with the thyroid in situ: A prospective intraoperative study

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Pathological and Genetic Characterization of Bilateral Adrenomedullary Hyperplasia in a Patient with Germline MAX Mutation

International audienceIn recent years, familial pheochromocytoma (PHEO) with germline mutations in the MAX (MYC associated factor X) gene has been reported in a few cases. Here, we investigated a 25-year-old patient with multiple PHEOs associated with a non-sense germline MAX mutation. Preoperative 18F-FDOPA PET/CT revealed bilateral adrenal involvement with multiple tumors. In addition, both adrenal glands were found to have diffuse or nodular adrenal medullary hyperplasia (AMH), a histopathological feature previously described as a precursor of MEN2- and SDHB-related PHEOs but not MAX. After bilateral adrenalectomy, different paraffin-embedded and frozen samples were analyzed for allelic imbalances of the MAX gene using allelic quantification by pyrosequencing. The expression of the protein MAX was studied by immunohistochemistry. All PHEOs but also nodular AMH exhibited a loss of the normal allele. By contrast, the diffuse AMH did not show loss-of-heterozygosity. Nevertheless, immunohistochemistry demonstrated loss of protein MAX expression in all samples including diffuse hyperplasia, suggesting a causative role of MAX mutation for both PHEOs and AMH. The present case shows that both nodular and diffuse AMH belongs to the spectrum of MAX-related disease. These data support the possible continuum between nodular AMH and PHEO, expanding the qualification of micro-PHEO to nodular AMH

Paraganglioma of the organ of Zuckerkandl associated with a somatic HIF2α mutation: A case report

International audienceParagangliomas of the organ of Zuckerkandl (OZ-PGL) are rare tumors that, in >70% of cases, occur in association with succinate dehydrogenase complex iron sulfur subunit B (SDHB) or SDHD gene mutations. The aim of the current study was to determine whether a somatic genetic defect in the hypoxia-inducible factor 2α (HIF2α) gene was present in a case of sporadic OZ-PGL. A 32-year-old African female presented with uncontrolled hypertension during the first trimester of pregnancy. A diagnostic hysteroscopy was performed 3 months after delivery, precipitating a hyper-tensive crisis. Thereafter, the patient was diagnosed with noradrenaline-secreting OZ-PGL. A complete blood count identified mild normocytic anemia of an inflammatory origin. Surgical removal of the tumor resulted in normalization of plasma and urinary normetanephrine levels. Genetic testing for germline mutations (including large deletions) in the von Hippel-Lindau tumor suppressor, SDHB, SDHC and SDHD genes was normal. However, a heterozygous missense mutation (c.1589Cys>Tyr) was detected in exon 12 of HIF2α, which results in a substitution of alanine 530 with valine (Ala530Val) in the HIF2α protein. A germline mutation was excluded based on the negative results of blood DNA testing. A three-dimensional homology model of Ala530Val was constructed, which showed impaired HIF2α/VHL interaction and decreased HIF2α ubiquitination. 1 H-high-resolution magic-angle-spinning nuclear magnetic resonance spectroscopy detected low succinate levels and high α and β glucose levels. To the best of our knowledge, the present case represents the first of its kind to associate a somatic HIF2α gain-of-function mutation with OZ-PGL. It is therefore recommended that patients without germline SDHx mutations should be tested for HIF2α mutations

Germinal defects of SDHx genes in patients with isolated pituitary adenoma

International audienceThe ‘3PAs’ syndrome, associating pituitary adenoma (PA) and pheochromocytoma/paraganglioma (PPGL), is sometimes associated with mutations in PPGL-predisposing genes, such as SDHx or MAX . In ’3PAs’ syndrome, PAs can occur before PPGL, suggesting a new gateway into SDHx/MAX- related diseases. Objective: To determine the SDHx/MAX mutation prevalence in patients with isolated PAs and characterize PAs of patients with SDHx/MAX mutations. Design: Genes involved in PAs ( AIP/MEN1/CDKN1B ) or PPGLs ( SDHx/MAX ) were sequenced in patients with isolated PAs. We then conducted a review of cases of PA in the setting of ’3PAs’ syndrome. Results: A total of 263 patients were recruited. Seven (likely) pathogenic variants were found in AIP , two in MEN1 , two in SDHA , and one in SDHC . The prevalence of SDHx mutations reached 1.1% (3/263). Of 31 reported patients with PAs harboring SDHx/MAX mutations (28 published cases and 3 cases reported here), 6/31 (19%) developed PA before PPGL and 8/31 (26%) had isolated PA. The age of onset was later than in patients with AIP/MEN1 mutations. PAs were mainly macroprolactinomas and showed intracytoplasmic vacuoles seen on histopathology. Conclusions: We discovered SDHx mutations in patients bearing PA who had no familial or personal history of PPGL. However, the question of incidental association remains unresolved and data to determine the benefit of SDHx/MAX screening in these patients are lacking. We recommend that patients with isolated PA should be carefully examined for a family history of PPGLs. A family history of PPGL, as well as the presence of intracytoplasmic vacuoles in PA, requires SDHx/MAX genetic testing of patients

F-18-FDOPA PET/CT Imaging of MAX-Related Pheochromocytoma

International audienceContext: MYC-associated factor X (MAX) has been recently described as a new susceptibility pheochromocytoma (PHEO) gene with a total of similar to 40 reported cases. At present, no study has specifically described the functional imaging phenotype of MAX-related PHEO. Objective, Patients, and Design: The objective of the present study was to present our experience with contrast-enhanced computed tomography (CT) and F-18-fluorodihydroxyphenylalanine (F-18-FDOPA) positron emission tomography (PET)/CT in six consecutive patients (four at the initial diagnosis and two at the follow-up evaluation) with rare, but clinically important, MAX-related PHEOs. In five patients, F-18-FDOPA was also compared with other radiopharmaceutical agents. Results: The patients had five different mutations in the MAX gene that caused disruption of Max/Myc interaction and/or abolished interaction with DNA based on in silico analyses. All but one patient developed bilateral PHEOs during their lifetime. In all cases, F-18-FDOPA PET/CT accurately visualized PHEOs that were often multiple within the same gland or bilaterally and detected more adrenal and extra-adrenal lesions than did CT (per-lesion sensitivity, 90.9% vs 52.4% for CT/magnetic resonance imaging). The two PHEOs missed on F-18-FDOPA PET/CT were,1 cm, corresponding to nodular adrenomedullary hyperplasia. Ga-68-DOTA, Tyr3-octreotate PET/CT detected fewer lesions than did F-18-FDOPA PET/CT in one of three patients, and F-18-fluorodeoxyglucose PET/CT was only faintly positive in two of four patients with underestimation of extra-adrenal lesions in one patient. Conclusions: MAX-related PHEOs exhibit a marked F-18-FDOPA uptake, a finding that illustrates the common well-differentiated chromaffin pattern of PHEOs associated with activation of kinase signaling pathways. F-18-FDOPA PET/CT should be considered as the first-line functional imaging modality for diagnostic or follow-up evaluations for these patients

Implications of SDHB genetic testing in patients with sporadic pheochromocytoma

International audiencePURPOSE: Succinate dehydrogenase B (SDHB) associated pheochromocytomas (PHEOs) are associated with a higher risk of tumor aggressiveness and malignancy. The aim of the present study was to evaluate (1) the frequency of germline SDHB mutations in apparently sporadic patients with PHEO who undergo preoperative genetic testing and (2) the ability to predict pathogenic mutations.METHODS: From 2012 to 2016, 82 patients underwent a PHEO surgical resection. Sixteen were operated in the context of hereditary PHEO and were excluded from analysis. Among the 66 remaining cases, 48 were preoperatively screened for an SDHB mutation. In addition to imaging studies with specific radiopharmaceuticals (123I-MIBG or 18F-FDOPA) for exclusion of multifocality/metastases, 36 patients underwent 18F-FDG PET/CT.RESULTS: From the 48 genetically screened patients, genetic testing found a germline SDHB variant in two (4.2%) cases: a variant of unknown significance, exon 1, c.14T>G (p.Val5Gly), and a most likely pathogenic mutation, exon 5, c.440A>G (p.Tyr147Cys), according to in silico analysis. Structural and functional analyses of the protein predicted that p.Tyr147Cys mutant was pathogenic. Both tumors exhibited moderate 18F-FDG PET uptake with similar uptake patterns to non-SDHB mutated PHEOs. The two patients underwent total laparoscopic adrenalectomies. Of the remaining patients, 44 underwent a laparoscopic adrenalectomy, and two had an open approach. Pathological analysis of the tumors from patients bearing two germline SDHB variants revealed a typical PHEO (PASS 0 and 2). Ex-vivo analyses (metabolomics, SDHB immunohistochemistry, loss of heterozygosity analysis) allowed a reclassification of the two SDHB variants as probably non-pathogenic variants.CONCLUSIONS:This study illustrates that SDHx mutational analysis can be misleading, even if structural and functional analyses are done. Surgeons should be aware of the difficulty of classifying new SDHB variants prior to implementing SDHB mutation status into a tailored surgical management strategy of a patient

Characterization of adrenocortical tumors by 18F-FDG PET/CT: does steroid hormone hypersecretion status modify the uptake pattern?

Background adrenal tumor-to-liver uptake value (Tmx:Lmx) on 18F-FDG PET/CT is an accurate and reproducible PET parameter in the distinction between benign and malignant adrenal masses. The potential impact of steroid hormone secretion on 18F-FDG uptake is still debatable. The aim of this study was to evaluate this relationship. Methods 2010–2015: 73 patients who underwent adrenalectomy for adrenocortical tumors [49 secreting/(SA) and 24 non-secreting/(NSA)] were retrospectively included in the study. Fourteen were malignant. All patients underwent hormonal evaluation, functional and anatomical imaging, Weiss scoring and Ki 67 evaluation. Results malignant tumors exhibit higher SUVmax than benign tumors (median 7.75 vs 3.06 respectively, p < 0.001) and Tmx:Lmx was 2.7 vs 1.17 for benign tumors, p < 0.001. Tmx:Lmx was positively correlated to Weiss score (p < 0.001). No significant difference was observed for Tmx:Lmx between SA and NSA overall (p = 0.851), regardless of the subgroup of tumors analyzed. Tmx:Lmx was not correlated to tumor size (p < 0.508) or 24 h free urinary cortisol level (p < 0.522). Conclusions no correlation was observed between Tmx:Lmx and hormonal status, however the correlation between ratio, malignancy and Weiss score confirm the utility of 18F-FDG PET/CT for the differentiation of benign from malignant adrenal lesions, irrespective of the hormone secretory status of the tumor. 18F-FDG PET/CT is a useful biomarker in the diagnosis of adrenal tumors, regardless of the secretion status