Despite two decades of paraganglioma-pheochromocytoma research, the fundamental question of how the different succinate dehydrogenase (SDH)-related tumor phenotypes are initiated has remained... Show moreDespite two decades of paraganglioma-pheochromocytoma research, the fundamental question of how the different succinate dehydrogenase (SDH)-related tumor phenotypes are initiated has remained unanswered. Here, we discuss two possible scenarios by which missense (hypomorphic alleles) or truncating (null alleles) SDH gene variants determine clinical phenotype. Dysfunctional SDH is a major source of reactive oxygen species (ROS) but ROS are inhibited by rising succinate levels. In scenario 1, we propose that SDH missense variants disrupt electron flow, causing elevated ROS levels that are toxic in sympathetic PPGL precursor cells but well controlled in oxygen-sensing parasympathetic paraganglion cells. We also suggest that SDHAF2 variants, solely associated with HNPGL, may cause the reversal of succinate dehydrogenase to fumarate reductase, producing very high ROS levels. In scenario 2, we propose a modified succinate threshold model of tumor initiation. Truncating SDH variants cause high succinate accumulation and likely initiate tumorigenesis via disruption of 2-oxoglutarate-dependent enzymes in both PPGL and HNPGL precursor tissues. We propose that missense variants (including SDHAF2) cause lower succinate accumulation and thus initiate tumorigenesis only in very metabolically active tissues such as parasympathetic paraganglia, which naturally show very high levels of succinate. Show less
Background: Presurgical treatment with an alpha-adrenergic receptor blocker is recommended to antagonize the catecholamine-induced alpha-adrenergic receptor mediated vasoconstriction in patients... Show moreBackground: Presurgical treatment with an alpha-adrenergic receptor blocker is recommended to antagonize the catecholamine-induced alpha-adrenergic receptor mediated vasoconstriction in patients with pheochromocytoma or sympathetic paraganglioma (PPGL). There is, however, a considerable interindividual variation in the dose-response relationship regarding the magnitude of blood pressure reduction or the occurrence of side effects. We hypothesized that genetically determined differences in alpha-adrenergic receptor activity contribute to this variability in dose-response relationship. Methods: Thirty-one single-nucleotide polymorphisms (SNPs) of the alpha 1A, alpha 1B, alpha 1D adrenoreceptor (ADRA1A, ADRA1B, ADRA1D) and alpha 2A, alpha 2B adrenoreceptor (ADRA2A, ADRA2B) genes were genotyped in a group of 116 participants of the PRESCRIPT study. Haplotypes were constructed after determining linkage disequilibrium blocks. Results: The ADRA1B SNP rs10515807 and the ADRA2A SNPs rs553668/rs521674 were associated with higher dosages of alpha-adrenergic receptor blocker (p < 0.05) and with a higher occurrence of side effects (rs10515807) (p = 0.005). Similar associations were found for haplotype block 6, which is predominantly defined by rs10515807. Conclusions: This study suggests that genetic variability of alpha-adrenergic receptor genes might be associated with the clinically observed variation in beneficial and adverse therapeutic drug responses to alpha-adrenergic receptor blockers. Further studies in larger cohorts are needed to confirm our observations. Show less
Context: Pheochromocytomas and paragangliomas (PPGLs) are neuroendocrine tumors in which altered central metabolism appears to be a major driver of tumorigenesis, and many PPGL genes encode... Show moreContext: Pheochromocytomas and paragangliomas (PPGLs) are neuroendocrine tumors in which altered central metabolism appears to be a major driver of tumorigenesis, and many PPGL genes encode proteins involved in the tricarboxylic acid (TCA) cycle.Objective/design: While about 40% of PPGL cases carry a variant in a known gene, many cases remain unexplained. In patients with unexplained PPGL showing clear evidence of a familial burden or multiple tumors, we aimed to identify causative factors using genetic analysis of patient DNA and functional analyses of identified DNA variants in patient tumor material and engineered cell lines.Patients and Setting: Patients with a likely familial cancer burden of pheochromocytomas and/or paragangliomas and under investigation in a clinical genetic and clinical research setting in university hospitals.Results: While investigating unexplained PPGL cases, we identified a novel variant, c.1151C>T, p.(Pro384Leu), in exon 14 of the gene encoding dihydrolipoamide S-succinyltransferase (DLST), a component of the multi-enzyme complex 2-oxoglutarate dehydrogenase. Targeted sequence analysis of further unexplained cases identified a patient carrying a tumor with compound heterozygous variants in DLST, consisting of a germline variant, c.1121G>A, p.(Gly374Glu), together with a somatic missense variant identified in tumor DNA, c.1147A>G, p.(Thr383Ala), both located in exon 14. Using a range of in silico and functional assays we show that these variants are predicted to be pathogenic, profoundly impact enzyme activity, and result in DNA hypermethylation.Conclusions: The identification and functional analysis of these DLST variants further validates DLST as an additional PPGL gene involved in the TCA cycle. Show less
This review describes human and rodent-derived cell lines and xenografts developed over the last five decades that are suitable or potentially suitable models for paraganglioma-pheochromocytoma... Show moreThis review describes human and rodent-derived cell lines and xenografts developed over the last five decades that are suitable or potentially suitable models for paraganglioma-pheochromocytoma research. We outline the strengths and weaknesses of various models and emphasize the recurring theme that, despite the major challenges involved, more effort is required in the search for valid human and animal cell models of paraganglioma-pheochromocytoma, particularly those relevant to cancers carrying a mutation in one of the succinate dehydrogenase genes. Despite many setbacks, the recent development of a potentially important new model, the RSO cell line, gives reason for optimism regarding the future of models in the paraganglioma-pheochromocytoma field. We also note that classic approaches to cell line derivation such as SV40-mediated immortalization and newer approaches such as organoid culture or iPSCs have been insufficiently explored. As many existing cell lines have been poorly characterized, we provide recommendations for reporting of paraganglioma and pheochromocytoma cell lines, including the strong recommendation that cell lines are made widely available via the ATCC or a similar cell repository. Basic research in paraganglioma-pheochromocytoma is currently transition ing from the analysis of genetics to the analysis of disease mechanisms and the clinically exploitable vulnerabilities of tumors. A successful transition will require many more disease-relevant human and animal models to ensure continuing progress. Show less
Context: Pretreatment with alpha-adrenergic receptor blockers is recommended to prevent hemodynamic instability during resection of a pheochromocytoma or sympathetic paraganglioma (PPGL).Objective:... Show moreContext: Pretreatment with alpha-adrenergic receptor blockers is recommended to prevent hemodynamic instability during resection of a pheochromocytoma or sympathetic paraganglioma (PPGL).Objective: To determine which type of alpha-adrenergic receptor blocker provides the best efficacy.Design: Randomized controlled open-label trial (PRESCRIPT; ClinicalTrials.gov NCT01379898)Setting: Multicenter study including 9 centers in The Netherlands.Patients: 134 patients with nonmetastatic PPGL.Intervention: Phenoxybenzamine or doxazosin starting 2 to 3 weeks before surgery using a blood pressure targeted titration schedule. lntraoperative hemodynamic management was standardized.Main Outcome Measures: Primary efficacy endpoint was the cumulative intraoperative time outside the blood pressure target range (ie, SBP >160 mmHg or MAP <60 mmHg) expressed as a percentage of total surgical procedure time. Secondary efficacy endpoint was the value on a hemodynamic instability score.Results: Median cumulative time outside blood pressure targets was 11.1% (interquartile range [IQR]: 4.3-20.6] in the phenoxybenzamine group compared to 12.2% (5.3-20.2)] in the doxazosin group (P = .75, r = 0.03). The hemodynamic instability score was 38.0 (28.8-58.0) and 50.0 (35.3-63.8) in the phenoxybenzamine and doxazosin group, respectively (P = .02, r = 0.20). The 30-day cardiovascular complication rate was 8.8% and 6.9% in the phenoxybenzamine and doxazosin group, respectively (P = .68). There was no mortality after 30 days.Conclusions: The duration of blood pressure outside the target range during resection of a PPGL was not different after preoperative treatment with either phenoxybenzamine or doxazosin. Phenoxybenzamine was more effective in preventing intraoperative hemodynamic instability, but it could not be established whether this was associated with a better clinical outcome. Show less
Purpose of review Although the majority of pheochromocytoma and paraganglioma are benign, 15-17% develop metastatic disease, being present at the initial diagnosis in about 11-31% of cases. The... Show morePurpose of review Although the majority of pheochromocytoma and paraganglioma are benign, 15-17% develop metastatic disease, being present at the initial diagnosis in about 11-31% of cases. The natural course of metastasized disease is highly heterogeneous, with an overall 5-year survival rate varying between 40% and 85%. For individual patients, overall survival, progression-free survival, and clinical outcome are difficult to predict. Management of metastasized pheochromocytoma and paraganglioma is challenging. Currently available therapeutic options are surgical debulking, treatment with radiopharmaceuticals (I-131-MIBG, Y-90 and Lu-177-DOTATATE), chemotherapy and targeted therapy. Recent findings The pathogenesis of pheochromocytoma and paraganglioma (PPGL) is largely driven by genomic alterations in PPGL susceptibility genes related to three different clusters: altered pseudo-hypoxic signaling (cluster-1), altered MAP-kinase signaling (cluster-2) and altered Wnt signaling (cluster-3). Novel targeted therapies (tyrosine kinase inhibitors) and potential future therapeutic options, guided by improved knowledge about the oncogenic cluster 1-3 signaling pathways, will be discussed. Treatment of metastasized pheochromocytoma and paraganglioma remains challenging. Profiling of gene expression and methylation can serve as a powerful tool for characterizing disease clusters and for guiding targeted therapy to improve selectivity and efficacy. Current knowledge of signatures involved in molecular signaling, metabolism, and resistance mechanisms of PPGLs suggests that therapeutic regimens can be optimized to each molecular subtype. Show less
Berkel, A. van; Vriens, D.; Visser, E.P.; Janssen, M.J.R.; Gotthardt, M.; Hermus, A.R.M.M.; ... ; Timmers, H.J.L.M. 2019
Eijkelenkamp, K.; Olderode-Berends, M.J.W.; Luijt, R.B. van der; Robledo, M.; Dooren, M. van; Feelders, R.A.; ... ; Horst-Schrivers, A.N.A. van der 2018
