Succinate dehydrogenase B gene mutations predict survival in patients with malignant pheochromocytomas or paragangliomas

Diagnostic Performance of (68)Ga-DOTATATE PET/CT, (18)F-FDG PET/CT and (131)I-MIBG Scintigraphy in Mapping Metastatic Pheochromocytoma and Paraganglioma

PURPOSE

To evaluate the diagnostic performance of (68)Ga-DOTATATE (18)F-fluorodeoxyglucose ((18)F-FDG) positron emission tomography (PET)/computed tomography (CT), (18)F-FDG PET/CT and (131)I-MIBG scintigraphy in the mapping of metastatic pheochromocytoma and paraganglioma.

MATERIALS AND METHODS

Seventeen patients (male = 8, female = 9; age range, 13-68 years) with clinically proven or suspicious metastatic pheochromocytoma or paraganglioma were included in this prospective study. Twelve patients underwent all three modalities, whereas five patients underwent (68)Ga-DOTATATE and (131)I-MIBG without (18)F-FDG. A composite reference standard derived from anatomical and functional imaging findings, along with histopathological information, was used to validate the findings. Results were analysed on a per-patient and on per-lesion basis. Sensitivity and accuracy were assessed using McNemar's test.

RESULTS

On a per-patient basis, 14/17 patients were detected in (68)Ga-DOTATATE, 7/17 patients in (131)I-MIBG, and 10/12 patients in (18)F-FDG. The sensitivity and accuracy of (68)Ga-DOTATATE, (131)I-MIBG and (18)F-FDG were (93.3 %, 94.1 %), (46.7 %, 52.9 %) and (90.9 %, 91.7 %) respectively. On a per-lesion basis, an overall of 472 positive lesions were detected; of which 432/472 were identified by (68)Ga-DOTATATE, 74/472 by (131)I-MIBG, and 154/300 (patient, n = 12) by (18)F-FDG. The sensitivity and accuracy of (68)Ga-DOTATATE, (131)I-MIBG and (18)F-FDG were (91.5 %, 92.6 % p < 0.0001), (15.7 %, 26.0 % p < 0.0001) and (51.3 %, 57.8 % p < 0.0001) respectively. Discordant lesions were demonstrated on (68)Ga-DOTATATE, (131)I-MIBG and (18)F-FDG.

CONCLUSIONS

Ga-DOTATATE PET/CT shows high diagnostic accuracy than (131)I-MIBG scintigraphy and (18)F-FDG PET/ CT in mapping metastatic pheochromocytoma and paraganglioma.

Paraganglioma and phaeochromocytoma: from genetics to personalized medicine

Paragangliomas and phaeochromocytomas are neuroendocrine tumours whose pathogenesis and progression are very strongly influenced by genetics. A germline mutation in one of the susceptibility genes identified so far explains ∼40% of all cases; the remaining 60% are thought to be sporadic cases. At least one-third of these sporadic tumours contain a somatic mutation in a predisposing gene. Genetic testing, which is indicated in every patient, is guided by the clinical presentation as well as by the secretory phenotype and the immunohistochemical characterization of the tumours. The diagnosis of an inherited form drives clinical management and tumour surveillance. Different 'omics' profiling methods have provided a neat classification of these tumours in accordance with their genetic background. Transcriptomic studies have identified two main molecular pathways that underlie development of these tumours, one in which the hypoxic pathway is activated (cluster 1) and another in which the MAPK and mTOR (mammalian target of rapamycin) signalling pathways are activated (cluster 2). DNA methylation profiling has uncovered a hypermethylator phenotype in tumours related to SDHx genes (a group of genes comprising SDHA, SDHB, SDHC, SDHD and SDHAF2) and revealed that succinate acts as an oncometabolite, inhibiting 2-oxoglutarate-dependent dioxygenases, such as hypoxia-inducible factor prolyl-hydroxylases and histone and DNA demethylases. 'Omics' data have suggested new therapeutic targets for patients with a malignant tumour. In the near future, new 'omics'-based tests are likely to be transferred into clinical practice with the goal of establishing personalized medical management for affected patients.

Multi-omics analysis defines core genomic alterations in pheochromocytomas and paragangliomas

Pheochromocytomas and paragangliomas (PCCs/PGLs) are neural crest-derived tumours with a very strong genetic component. Here we report the first integrated genomic examination of a large collection of PCC/PGL. SNP array analysis reveals distinct copy-number patterns associated with genetic background. Whole-exome sequencing shows a low mutation rate of 0.3 mutations per megabase, with few recurrent somatic mutations in genes not previously associated with PCC/PGL. DNA methylation arrays and miRNA sequencing identify DNA methylation changes and miRNA expression clusters strongly associated with messenger RNA expression profiling. Overexpression of the miRNA cluster 182/96/183 is specific in SDHB-mutated tumours and induces malignant traits, whereas silencing of the imprinted DLK1-MEG3 miRNA cluster appears as a potential driver in a subgroup of sporadic tumours. Altogether, the complete genomic landscape of PCC/PGL is mainly driven by distinct germline and/or somatic mutations in susceptibility genes and reveals different molecular entities, characterized by a set of unique genomic alterations.

Pathophysiology and diagnosis of disorders of the adrenal medulla: focus on pheochromocytoma

The principal function of the adrenal medulla is the production and secretion of catecholamines. During stressful challenging conditions, catecholamines exert a pivotal homeostatic role. Although the main adrenomedullary catecholamine, epinephrine, has a wide array of adrenoreceptor-mediated effects, its absence does not cause life-threatening problems. In contrast, excess production of catecholamines due to an adrenomedullary tumor, specifically pheochromocytoma, results in significant morbidity and mortality. Despite being rare, pheochromocytoma has a notoriously bad reputation because of its potential devastating effects if undetected and untreated. The paroxysmal signs and symptoms and the risks of missing or delaying the diagnosis are well known for most physicians. Nevertheless, even today the diagnosis is still overlooked in a considerable number of patients. Prevention and complete cure are however possible by early diagnosis and appropriate treatment but these patients remain a challenge for physicians. Yet, biochemical proof of presence or absence of catecholamine excess has become more easy and straightforward due to developments in assay methodology. This also applies to radiological and functional imaging techniques for locating the tumor. The importance of genetic testing for underlying germline mutations in susceptibility genes for patients and relatives is increasingly recognized. Yet, the effectiveness of genetic testing, in terms of costs and benefits to health, has not been definitively established. Further improvement in knowledge of genotype-phenotype relationships in pheochromocytoma will open new avenues to a more rationalized and personalized diagnostic approach of affected patients.

Pheochromocytoma

Pheochromocytoma and paraganglioma are catecholamine-producing tumors that are associated with substantial serious morbidity and mortality. A carefully taken medical history and early consideration of such tumors are key for early diagnosis and treatment. The biochemical diagnosis should include measurements of metanephrines in either plasma or urine. In addition to anatomical imaging, sensitive functional imaging modalities offer extra benefit for most patients in locating the tumor and eventual metastases. In at least 30% of all patients with a pheochromocytoma/paraganglioma, an underlying germline is responsible for tumor development and genetic testing should be considered in all patients. Current treatment options for malignant pheochromocytoma/paraganglioma are still very modest. New developments in the therapeutic armamentarium may improve the prospect for these patients.

Therapy of endocrine disease: treatment of malignant pheochromocytoma and paraganglioma

Metastatic pheochromocytomas and paragangliomas (MPPs) present clinicians with three major challenges: scarcity, complexity of characterization, and heterogeneous behavior and prognosis. As with the treatment for all neuroendocrine tumors, the control of hormonal symptoms and tumor growth is the main therapeutic objective in MPP patients. A significant number of MPP patients still die from uncontrolled hormone secretion. In addition, the management of MPPs remains palliative. Steps forward include proper characterization of MPP patients at large cancer referral centers with multidisciplinary teams; improved strategies to stratify patients prognostically; and implementation of trials within national and international networks. Progress in the molecular characterization and staging of MPPs constitutes the basis for significant treatment breakthroughs.

The size of the primary tumor and age at initial diagnosis are independent predictors of the metastatic behavior and survival of patients with SDHB-related pheochromocytoma and paraganglioma: a retrospective cohort study

Background

Succinate dehydrogenase subunit B (SDHB) mutations are associated with aggressive pheochromocytoma (PHEO)/paraganglioma (PGL) behavior, often resulting in metastatic disease and fatal outcomes. These tumors are often larger, extra-adrenal, and contain lower catecholamine concentrations than other hereditary PHEOs/PGLs. This study evaluated the size and age at diagnosis of primary SDHB-related PHEOs/PGLs as independent predictors of their metastatic behavior and outcome (survival).

Methods

One hundred six patients with SDHB mutation-related PHEO/PGL were included in this retrospective study. The recorded largest diameters, locations, and patient ages at initial diagnosis of SDHB-related primary tumors were analyzed in the context of time to metastasis and patient survival.

Results

First, the development of metastatic disease in patients with primary tumors ≥4.5 cm was significantly earlier than in patients with smaller tumors (P = 0.003). Second, patients with primary tumors larger than 5.5 cm also had worse overall survival than patients with smaller tumors (P = 0.008). Third, age at initial diagnosis was found to be an independent predictor of patient survival (PHEOs: P = 0.041; PGLs: P < 0.001). Fourth, we did not observe a significant difference in survival based on the specific SDHB mutations or patient sex.

Conclusion

Receiver operating characteristic curves established 4.5 cm as the best value to dichotomize the primary SDHB-related PHEO/PGL in order to evaluate the development of metastatic disease and 5.5 cm as the best value for survival prediction. Subsequently, the size of the primary tumor was found as an age-independent predictor of patient survival and metastases development in PGL. In both PHEO and PGL, age at diagnosis was found to be a size-independent predictor of patient survival. No significant difference was found in metastases development or patient survival between males and females or among specific SDHB mutations. This data further extends and supports previous recommendations that carriers with SDHB mutations must undergo early and regular evaluations to detect PHEO/PGL in order to achieve the best clinical outcome.

Powerhouse down: Complex II dissociation in the respiratory chain

Complex II of the respiratory chain (RC) recently emerged as a prominent regulator of cell death. In both cancer cells as well as neurodegenerative diseases, mutations in subunits have been found along with other genetic alterations indirectly affecting this complex. Anticancer compounds were developed that target complex II and cause cell death in a tumor-specific way. Our mechanistic understanding of how complex II is activated for cell death induction has recently been made clearer in recent studies, the results of which are covered in this review. This protein assembly is specifically activated for cell death via the dissociation of its SDHA and SDHB subunits from the membrane-anchoring proteins through pH change or mitochondrial Ca(2+) influx. The SDH activity contained in the SDHA/SDHB subcomplex remains intact and then generates, in an uncontrolled fashion, excessive amounts of reactive oxygen species (ROS) for cell death. Future studies on this mitochondrial complex will further elucidate it as a target for cancer treatments and reveal its role as a nexus for many diverse stimuli in cell death signaling.

Genetic testing in the clinical care of patients with pheochromocytoma and paraganglioma

PURPOSE OF REVIEW

Paraganglioma and pheochromocytoma (PGL/PCC) are tumours of neural crest origin that can present along a clinical spectrum ranging from apparently sporadic, isolated tumours to a more complex phenotype of one or multiple tumours in the context of other clinical features and family history suggestive of a defined hereditary syndrome. Genetic testing for hereditary PGL/PCC can help to confirm a genetic diagnosis for sporadic and syndromic cases. Informative genetic testing serves to clarify future risks for the patient and family members.

RECENT FINDINGS

Genetic discovery in the last decade has identified new PGL/PCC susceptibility loci. We summarize a contemporary approach adopted in our programme for genetic evaluation, testing and prospective management involving biochemical monitoring and imaging for hereditary PGL/PCC. A clinical vignette is presented to illustrate our practice.

SUMMARY

Current estimates that up to 40% of PGL/PCC are associated with germline mutations have implications for genetic testing recommendations. Prospective management of patients with defined hereditary susceptibility is based on established guidelines for well characterized syndromes. Management of tumour risk for rare syndromes, newly defined genetic associations and undefined genetic susceptibility in the setting of significant family history presents a challenge. Sustained discovery of new PGL/PCC genes underscores the need for a practice of continued genetic evaluation for patients with uninformative results. All patients with PGL/PCC should undergo genetic testing to identify potential hereditary tumour susceptibility.

Overexpression of miR-210 is associated with SDH-related pheochromocytomas, paragangliomas, and gastrointestinal stromal tumours

miR-210 is a key regulator of response to hypoxia. Pheochromocytomas (PCs) and paragangliomas (PGLs) with germline SDHx or VHL mutations have pseudohypoxic gene expression signatures. We hypothesised that PC/PGLs containing SDHx or VHL mutations, and succinate dehydrogenase (SDH)-deficient gastrointestinal stromal tumours (GISTs), would overexpress miR-210 relative to non-SDH or -VHL-mutated counterparts. miR-210 was analysed by quantitative PCR in i) 39 PC/PGLs, according to genotype (one SDHA, five SDHB, seven VHL, three NF1, seven RET, 15 sporadic, one unknown) and pathology (18 benign, eight atypical, 11 malignant, two unknown); ii) 18 GISTs, according to SDHB immunoreactivity (nine SDH-deficient and nine SDH-proficient) and iii) two novel SDHB-mutant neurosphere cell lines. miR-210 was higher in SDHx- or VHL-mutated PC/PGLs (7.6-fold) compared with tumours without SDHx or VHL mutations (P=0.0016). miR-210 was higher in malignant than in unequivocally benign PC/PGLs (P=0.05), but significance was lost when benign and atypical tumours were combined (P=0.08). In multivariate analysis, elevated miR-210 was significantly associated with SDHx or VHL mutation, but not with malignancy. In GISTs, miR-210 was higher in SDH-deficient (median 2.58) compared with SDH-proficient tumours (median 0.60; P=0.0078). miR-210 was higher in patient-derived neurosphere cell lines containing SDHB mutations (6.5-fold increase) compared with normal controls, in normoxic conditions (P<0.01). Furthermore, siRNA-knockdown of SDHB in HEK293 cells increased miR-210 by 2.7-fold (P=0.001) under normoxia. Overall, our results suggest that SDH deficiency in PC, PGL and GISTs induces miR-210 expression and substantiates the role of aberrant hypoxic-type cellular responses in the development of these tumours.

Pheochromocytoma and paraganglioma: an endocrine society clinical practice guideline

OBJECTIVE

The aim was to formulate clinical practice guidelines for pheochromocytoma and paraganglioma (PPGL).

PARTICIPANTS

The Task Force included a chair selected by the Endocrine Society Clinical Guidelines Subcommittee (CGS), seven experts in the field, and a methodologist. The authors received no corporate funding or remuneration.

EVIDENCE

This evidence-based guideline was developed using the Grading of Recommendations, Assessment, Development, and Evaluation (GRADE) system to describe both the strength of recommendations and the quality of evidence. The Task Force reviewed primary evidence and commissioned two additional systematic reviews.

CONSENSUS PROCESS

One group meeting, several conference calls, and e-mail communications enabled consensus. Committees and members of the Endocrine Society, European Society of Endocrinology, and Americal Association for Clinical Chemistry reviewed drafts of the guidelines.

CONCLUSIONS

The Task Force recommends that initial biochemical testing for PPGLs should include measurements of plasma free or urinary fractionated metanephrines. Consideration should be given to preanalytical factors leading to false-positive or false-negative results. All positive results require follow-up. Computed tomography is suggested for initial imaging, but magnetic resonance is a better option in patients with metastatic disease or when radiation exposure must be limited. (123)I-metaiodobenzylguanidine scintigraphy is a useful imaging modality for metastatic PPGLs. We recommend consideration of genetic testing in all patients, with testing by accredited laboratories. Patients with paraganglioma should be tested for SDHx mutations, and those with metastatic disease for SDHB mutations. All patients with functional PPGLs should undergo preoperative blockade to prevent perioperative complications. Preparation should include a high-sodium diet and fluid intake to prevent postoperative hypotension. We recommend minimally invasive adrenalectomy for most pheochromocytomas with open resection for most paragangliomas. Partial adrenalectomy is an option for selected patients. Lifelong follow-up is suggested to detect recurrent or metastatic disease. We suggest personalized management with evaluation and treatment by multidisciplinary teams with appropriate expertise to ensure favorable outcomes.

Anti-cancer potential of MAPK pathway inhibition in paragangliomas-effect of different statins on mouse pheochromocytoma cells

To date, malignant pheochromocytomas and paragangliomas (PHEOs/PGLs) cannot be effectively cured and thus novel treatment strategies are urgently needed. Lovastatin has been shown to effectively induce apoptosis in mouse PHEO cells (MPC) and the more aggressive mouse tumor tissue-derived cells (MTT), which was accompanied by decreased phosphorylation of mitogen-activated kinase (MAPK) pathway players. The MAPK pathway plays a role in numerous aggressive tumors and has been associated with a subgroup of PHEOs/PGLs, including K-RAS-, RET-, and NF1-mutated tumors. Our aim was to establish whether MAPK signaling may also play a role in aggressive, succinate dehydrogenase (SDH) B mutation-derived PHEOs/PGLs. Expression profiling and western blot analysis indicated that specific aspects of MAPK-signaling are active in SDHB PHEOs/PGLs, suggesting that inhibition by statin treatment could be beneficial. Moreover, we aimed to assess whether the anti-proliferative effect of lovastatin on MPC and MTT differed from that exerted by fluvastatin, simvastatin, atorvastatin, pravastatin, or rosuvastatin. Simvastatin and fluvastatin decreased cell proliferation most effectively and the more aggressive MTT cells appeared more sensitive in this respect. Inhibition of MAPK1 and 3 phosphorylation following treatment with fluvastatin, simvastatin, and lovastatin was confirmed by western blot. Increased levels of CASP-3 and PARP cleavage confirmed induction of apoptosis following the treatment. At a concentration low enough not to affect cell proliferation, spontaneous migration of MPC and MTT was significantly inhibited within 24 hours of treatment. In conclusion, lipophilic statins may present a promising therapeutic option for treatment of aggressive human paragangliomas by inducing apoptosis and inhibiting tumor spread.

SDHB mutations are associated with response to temozolomide in patients with metastatic pheochromocytoma or paraganglioma

Cyclophosphamide-dacarbazine-vincristine regimen is recommended for the treatment of malignant pheochromocytoma and paraganglioma (MPP); however, dacarbazine is the only recognized active drug in neuroendocrine tumours. We investigated the therapeutic benefit of temozolomide (TMZ), an oral alternative to dacarbazine, in patients with MPP. This is a retrospective study of consecutive patients with documented progressive MPP. We examined the correlation between Succinate dehydrogenase B (SDHB) mutation and O(6)-methylguanine-DNA methyltransferase (MGMT) promoter methylation and MGMT expression in the French nation-wide independent cohort of 190 pheochromocytomas or paragangliomas (PP). Progression-free survival (PFS) according to RECIST 1.1 and PERCIST 1.0 criteria was the primary end point. Fifteen consecutive patients with MPP were enrolled; ten (67%) carried a mutation in SDHB. The mean dose intensity of TMZ was 172 mg/m(2) /d for 5 days every 28 days. Median PFS was 13.3 months after a median follow-up of 35 months. There were five partial responses (33%), seven stable (47%) and three progressive diseases (20%). Grade 3 toxicities were lymphopenia in two patients and hypertension in one. Partial responses were observed only in patients with mutation in SDHB. MGMT immunohistochemistry was negative in tumour samples from four patients who responded to treatment. SDHB germline mutation was associated with hypermethylation of the MGMT promoter and low expression of MGMT in 190 samples of the French nation-wide independent cohort. This study demonstrates that TMZ is an effective antitumour agent in patients with SDHB-related MPP. The silencing of MGMT expression as a consequence of MGMT promoter hypermethylation in SDHB-mutated tumours may explain this finding.

Electron-transfer pathways in the heme and quinone-binding domain of complex II (succinate dehydrogenase)

Single electron transfers have been examined in complex II (succinate:ubiquinone oxidoreductase) by the method of pulse radiolysis. Electrons are introduced into the enzyme initially at the [3Fe–4S] and ubiquinone sites followed by intramolecular equilibration with the b heme of the enzyme. To define thermodynamic and other controlling parameters for the pathways of electron transfer in complex II, site-directed variants were constructed and analyzed. Variants at SdhB-His207 and SdhB-Ile209 exhibit significantly perturbed electron transfer between the [3Fe–4S] cluster and ubiquinone. Analysis of the data using Marcus theory shows that the electronic coupling constants for wild-type and variant enzyme are all small, indicating that electron transfer occurs by diabatic tunneling. The presence of the ubiquinone is necessary for efficient electron transfer to the heme, which only slowly equilibrates with the [3Fe–4S] cluster in the absence of the quinone.

Integrative genetic characterization and phenotype correlations in pheochromocytoma and paraganglioma tumours

BACKGROUND

About 60% of Pheochromocytoma (PCC) and Paraganglioma (PGL) patients have either germline or somatic mutations in one of the 12 proposed disease causing genes; SDHA, SDHB, SDHC, SDHD, SDHAF2, VHL, EPAS1, RET, NF1, TMEM127, MAX and H-RAS. Selective screening for germline mutations is routinely performed in clinical management of these diseases. Testing for somatic alterations is not performed on a regular basis because of limitations in interpreting the results.

AIM

The purpose of the study was to investigate genetic events and phenotype correlations in a large cohort of PCC and PGL tumours.

METHODS

A total of 101 tumours from 89 patients with PCC and PGL were re-sequenced for a panel of 10 disease causing genes using automated Sanger sequencing. Selected samples were analysed with Multiplex Ligation-dependent Probe Amplification and/or SNParray.

RESULTS

Pathogenic genetic variants were found in tumours from 33 individual patients (37%), 14 (16%) were discovered in constitutional DNA and 16 (18%) were confirmed as somatic. Loss of heterozygosity (LOH) was observed in 1/1 SDHB, 11/11 VHL and 3/3 NF1-associated tumours. In patients with somatic mutations there were no recurrences in contrast to carriers of germline mutations (P = 0.022). SDHx/VHL/EPAS1 associated cases had higher norepinephrine output (P = 0.03) and lower epinephrine output (P<0.001) compared to RET/NF1/H-RAS cases.

CONCLUSION

Somatic mutations are frequent events in PCC and PGL tumours. Tumour genotype may be further investigated as prognostic factors in these diseases. Growing evidence suggest that analysis of tumour DNA could have an impact on the management of these patients.

Hereditary kidney cancer syndromes

Inherited susceptibility to kidney cancer is a fascinating and complex topic. Our knowledge about types of genetic syndromes associated with an increased risk of disease is continually expanding. Currently, there are 10 syndromes associated with an increased risk of all types of kidney cancer, which are reviewed herein. Clear cell kidney cancer is associated with von Hippel Lindau disease, chromosome 3 translocations, PTEN hamartomatous syndrome, and mutations in the BAP1 gene as well as several of the genes encoding the proteins comprising the succinate dehydrogenase complex (SDHB/C/D). Type 1 papillary kidney cancers arise in conjunction with germline mutations in MET and type 2 as part of hereditary leiomyomatosis and kidney cell cancer (fumarate hydratase [FH] mutations). Chromophone and oncocytic kidney cancers are predominantly associated with Birt-Hogg-Dubé syndrome. Patients with Tuberous Sclerosis Complex (TSC) commonly have angiomyolipomas and rarely their malignant counterpart epithelioid angiomyolipomas. The targeted therapeutic options for the kidney cancer associated with these diseases are just starting to expand and are an area of active clinical research.

Paragangliomas: update on differential diagnostic considerations, composite tumors, and recent genetic developments

Recent developments in molecular genetics have expanded the spectrum of disorders associated with pheochromocytomas (PCCs) and extra-adrenal paragangliomas (PGLs) and have increased the roles of pathologists in helping to guide patient care. At least 30% of these tumors are now known to be hereditary, and germline mutations of at least 10 genes are known to cause the tumors to develop. Genotype-phenotype correlations have been identified, including differences in tumor distribution, catecholamine production, and risk of metastasis, and types of tumors not previously associated with PCC/PGL are now considered in the spectrum of hereditary disease. Important new findings are that mutations of succinate dehydrogenase genes SDHA, SDHB, SDHC, SDHD, and SDHAF2 (collectively "SDHx") are responsible for a large percentage of hereditary PCC/PGL and that SDHB mutations are strongly correlated with extra-adrenal tumor location, metastasis, and poor prognosis. Further, gastrointestinal stromal tumors and renal tumors are now associated with SDHx mutations. A PCC or PGL caused by any of the hereditary susceptibility genes can present as a solitary, apparently sporadic, tumor, and substantial numbers of patients presenting with apparently sporadic tumors harbor occult germline mutations of susceptibility genes. Current roles of pathologists are differential diagnosis of primary tumors and metastases, identification of clues to occult hereditary disease, and triaging of patients for optimal genetic testing by immunohistochemical staining of tumor tissue for the loss of SDHB and SDHA protein. Diagnostic pitfalls are posed by morphological variants of PCC/PGL, unusual anatomic sites of occurrence, and coexisting neuroendocrine tumors of other types in some hereditary syndromes. These pitfalls can be avoided by judicious use of appropriate immunohistochemical stains. Aside from loss of staining for SDHB, criteria for predicting risk of metastasis are still controversial, and "malignancy" is diagnosed only after metastases have occurred. All PCCs/PGLs are considered to pose some risk of metastasis, and long-term follow-up is advised.

Germline mutations in FH confer predisposition to malignant pheochromocytomas and paragangliomas

Malignant pheochromocytoma (PCC) and paraganglioma (PGL) are mostly caused by germline mutations of SDHB, encoding a subunit of succinate dehydrogenase. Using whole-exome sequencing, we recently identified a mutation in the FH gene encoding fumarate hydratase, in a PCC with an 'SDH-like' molecular phenotype. Here, we investigated the role of FH in PCC/PGL predisposition, by screening for germline FH mutations in a large international cohort of patients. We screened 598 patients with PCC/PGL without mutations in known PCC/PGL susceptibility genes. We searched for FH germline mutations and large deletions, by direct sequencing and multiplex ligation-dependent probe amplification methods. Global alterations in DNA methylation and protein succination were assessed by immunohistochemical staining for 5-hydroxymethylcytosine (5-hmC) and S-(2-succinyl) cysteine (2SC), respectively. We identified five pathogenic germline FH mutations (four missense and one splice mutation) in five patients. Somatic inactivation of the second allele, resulting in a loss of fumarate hydratase activity, was demonstrated in tumors with FH mutations. Low tumor levels of 5-hmC, resembling those in SDHB-deficient tumors, and positive 2SC staining were detected in tumors with FH mutations. Clinically, metastatic phenotype (P = 0.007) and multiple tumors (P = 0.02) were significantly more frequent in patients with FH mutations than those without such mutations. This study reveals a new role for FH in susceptibility to malignant and/or multiple PCC/PGL. Remarkably, FH-deficient PCC/PGLs display the same pattern of epigenetic deregulation as SDHB-mutated malignant PCC/PGL. Therefore, we propose that mutation screening for FH should be included in PCC/PGL genetic testing, at least for tumors with malignant behavior.

Tianeptine interferes with microtubule organization and hormone secretion of pheochromocytoma cells

Pheochromocytoma originates from chromaffin cells in the adrenal medulla and sympathetic paraganglia. 36-53% of pheochromocytoma becomes malignant and, thereafter, resistant to conventional treatments. Pheochromocytoma also causes hyper-secretion of catecholamines that cause severe hypertension. We found that an antidepressant, tianeptine, interfered with normal life cycle of pheochromocytoma cells at its clinical doses. Treatment with tianeptine caused microtubule bundling and specific degradation of cytoplasmic dynein, a retrograde microtubule motor that mediates various microtubule-dependent processes during interphase and mitosis, in the rat pheochromocytoma PC12 cells. Tianeptine also increased the levels of pro-apoptotic proteins, slowed cell cycle progression, and increased apoptosis in PC12 cells. Importantly, tianeptine treatment decreased high K(+)-stimulated secretion of norepinephrine and chromogranin A in PC12 cells and of epinephrine in the mouse pheochromocytoma MPC cells. Our study demonstrates, for the first time, that tianeptine interferes with normal life cycle of pheochromocytoma cells.

Usefulness of negative and weak-diffuse pattern of SDHB immunostaining in assessment of SDH mutations in paragangliomas and pheochromocytomas

This is a confirmatory study about usefulness of SDHB and SDHA immunostaining in assessment of SDH mutations in paragangliomas and pheochromocytomas. Paraganglioma/pheochromocytoma syndrome (PGL/PCC syndrome) consists of different entities, associated with germline mutations in five different genes: SDHD, SDHAF2, SDHC, SDHA and SDHB. It has been suggested that negative immunostaining of SDHB can be taken as an indicator of the presence of a mutation in one of the five SDH genes. We have performed SDHB and SDHA immunohistochemical staining in a series of paragangliomas and pheochromocytomas from 64 patients. The patients had been previously checked for mutations in SDHD, SDHC and SDHB, but also for mutation in RET and VHL. All 14 patients with SDH mutations (9 with SDHB and 5 with SDHD mutations) exhibited negative or weak-diffuse SDHB staining pattern in tumour tissue, whereas cells of the 23 RET mutated and 8 VHL mutated tumours showed a positive SDHB immunostaining. Sixteen of the patients that did not exhibit a mutation in any gene showed positive SDHB immunostaining in tumour tissue, while only three of the patients without mutation exhibited negative staining. All patients exhibited positive pattern of SDHA immunostaining. The results confirm the value of SDHB immunohistochemical status in assessment of germline mutations in PGL/PCC syndrome.

Genetics of hereditary head and neck paragangliomas

BACKGROUND

The purpose of this study was to give an overview on hereditary syndromes associated with head and neck paragangliomas (HNPGs).

METHODS

Our methods were the review and discussion of the pertinent literature.

RESULTS

About one third of all patients with HNPGs are carriers of germline mutations. Hereditary HNPGs have been described in association with mutations of 10 different genes. Mutations of the genes succinate dehydrogenase subunit D (SDHD), succinate dehydrogenase complex assembly factor 2 gene (SDHAF2), succinate dehydrogenase subunit C (SDHC), and succinate dehydrogenase subunit B (SDHB) are the cause of paraganglioma syndromes (PGLs) 1, 2, 3, and 4. Succinate dehydrogenase subunit A (SDHA), von Hippel-Lindau (VHL), and transmembrane protein 127 (TMEM127) gene mutations also harbor the risk for HNPG development. HNPGs in patients with rearranged during transfection (RET), neurofibromatosis type 1 (NF1), and MYC-associated factor X (MAX) gene mutations have been described very infrequently.

CONCLUSION

All patients with HNPGs should be offered a molecular genetic screening. This screening may usually be restricted to mutations of the genes SDHD, SDHB, and SDHC. Certain clinical parameters can help to set up the order in which those genes should be tested.

One-year progression-free survival of therapy-naive patients with malignant pheochromocytoma and paraganglioma

CONTEXT

The natural history of malignant pheochromocytoma or paragangliomas (MPP) remain unknown.

OBJECTIVE

The primary aim of this study was to define progression-free survival at 1 year in therapy-naive patients with MPP. Secondary objectives were to characterize MPP and to look for prognostic parameters for progression at 1 year.

DESIGN AND SETTING

The files of MPP followed up between January 2001 and January 2011 in two French Endocrine Networks were retrospectively reviewed. Therapy-naive patients were enrolled.

MAIN OUTCOME MEASURES

The main outcome was progression-free survival at 1 year in therapy-naive MPP patients according to Response Evaluation Criteria In Solid Tumors 1.1 criteria.

RESULTS

Ninety files (46 men, 44 women, mean age of 47.5 ± 15 years) were reviewed on site by one investigator. MPP characteristics were as follows: presence of an adrenal primary, a mitotic count exceeding 5 per high power field, hypertension, inherited disease, and presence of bone metastases in 50%, 22%, 60%, 49%, and 56% patients, respectively. Fifty-seven of the 90 patients with MPP (63%) were classified as therapy-naive. The median follow-up of these 57 patients was 2.4 years (range, 0.4-5.7). At 1 year, progression-free survival was 46% (CI 95: 33-59). Twenty-six of 30 (87%) patients with progression at 1 year had exhibited progressive disease at the first imaging workup performed after a median of 5.7 months. No prognostic parameter was identified.

CONCLUSIONS

Half of the therapy-naive patients with MPP achieved stable disease at 1 year. In symptom-free patients with MPP, a wait-and-see antitumor policy seems appropriate as first line. Modality for a prospective follow-up is proposed.

Response after surgical resection of metastatic pheochromocytoma and paraganglioma: can postoperative biochemical remission be predicted?

BACKGROUND

Aggressive surgical resection with intent to cure and surgical debulking procedures are commonly recommended in patients with metastatic pheochromocytoma and paraganglioma. To date there are no data on operative outcomes of patients after surgical resection of metastatic pheochromocytoma and paraganglioma to determine if such an approach is appropriate and what factors may be associated with a favorable outcome.

STUDY DESIGN

We performed a retrospective analysis of 30 patients with metastatic pheochromocytoma/paraganglioma who underwent surgical treatment. Clinical characteristics and genetic factors were analyzed as predictors of biochemical response to surgery.

RESULTS

Thirty patients underwent a total of 42 operations, with a median follow-up time of 24 months (range 1 to 114 months). Complete disease resection (R0/R1) was achieved in 18 (42.9%) cases; 24 cases (57.1%) were debulking (R2) procedures without intent to cure. Complete biochemical remission was achieved in 10 (23.8%) cases and partial biochemical response was achieved in 23 (54.8%) cases. Patients with disease confined to the abdomen were more likely to achieve and maintain a biochemical response postoperatively than those with extra-abdominal disease (p = 0.0003). Debulking operations were significantly less likely to achieve or maintain biochemical palliation, with only 1 patient maintaining a biochemical response 12 months postoperatively (p < 0.0001). Patients were less likely to obtain pharmacologic independence after debulking (p = 0.0003), with only 2 (8.3%) not requiring pharmacotherapy 6 months after the intervention. Factors not associated with biochemical response to surgery include sex, family history, SDHB mutation status, systemic therapy, and preoperative biochemical profile.

CONCLUSIONS

Depending on the extent of disease, patients with metastatic pheochromocytoma/paraganglioma can benefit from aggressive operative intervention and resection with intent to cure. Debulking procedures are unlikely to achieve clinically significant biochemical response, with any biochemical response achieved being very short-lived.

Functional characterization of nonmetastatic paraganglioma and pheochromocytoma by (18) F-FDOPA PET: focus on missed lesions

AIMS AND METHODS

To evaluate the clinical value of (18) F-fluorodihydroxyphenylalanine ((18) F-FDOPA) PET in relation to tumour localization and the patient's genetic status in a large series of pheochromocytoma/paraganglioma (PHEO/PGL) patients and to discuss in detail false-negative results. A retrospective study of PGL patients who were investigated with (18) F-FDOPA PET or PET/CT imaging in two academic endocrine tumour centres was conducted (La Timone University Hospital, Marseilles, France and National Institutes of Health (NIH), Bethesda, MD, USA).

RESULTS

One hundred sixteen patients (39·7% harbouring germline mutations in known disease susceptibility genes) were evaluated for a total of 195 PHEO/PGL foci. (18) F-FDOPA PET correctly detected 179 lesions (91·8%) in 107 patients (92·2%). Lesion-based sensitivities for parasympathetic PGLs (head, neck, or anterior/middle thoracic ones), PHEOs, and extra-adrenal sympathetic (abdominal or posterior thoracic) PGLs were 98·2% [96·5% for Timone and 100% for NIH], 93·9% [93·8 and 93·9%] and 70·3% [47·1 and 90%] respectively (P < 0·001). Sympathetic (adrenal and extra-adrenal) SDHx-related PGLs were at a higher risk for negative (18) F-FDOPA PET than non-SDHx-related PGLs (14/24 vs 0/62, respectively, P < 0·001). In contrast, the risk of negative (18) F-FDOPA PET was lower for parasympathetic PGLs regardless of the genetic background (1/90 in SDHx vs 1/19 in non-SDHx tumours, P = 0·32). (18) F-FDOPA PET failed to detect two head and neck PGLs (HNPGL), likely due to their small size, whereas most missed sympathetic PGL were larger and may have exhibited a specific (18) F-FDOPA-negative imaging phenotype. (18) F-FDG PET detected all the missed sympathetic lesions.

CONCLUSIONS

(18) F-FDOPA PET appears to be a very sensitive functional imaging tool for HNPGL regardless of the genetic status of the tumours. Patients with false-negative tumours on (18) F-FDOPA PET should be tested for SDHx mutations.

Current and future treatments for malignant pheochromocytoma and sympathetic paraganglioma

Pheochromocytomas (PHs) and sympathetic paragangliomas (SPGs) are rare neuroendocrine tumors. Approximately 17 % of these tumors are malignant, but because no molecular or histologic markers for malignancy exist, patients are often diagnosed with malignant PHs or SPGs after unresectable disease has formed. Patients with progressive metastatic tumors and overwhelming symptoms are currently treated with systemic chemotherapy and radiopharmaceutical agents such as metaiodobenzylguanidine. These therapies lead to partial radiographic response, disease stabilization, and symptomatic improvement in approximately 40 % of patients, and systemic chemotherapy is associated with a modest improvement in overall survival duration. However, over the past decade, substantial progress has been made in clinical, biochemical, and radiographic diagnosis of PHs and SPGs. Approximately 50 % of patients with malignant PHs and SPGs have been found to carry hereditary germline mutations in the succinate dehydrogenase subunit B gene (SDHB), and anti-angiogenic agents such as sunitinib have been found to potentially play a role in the treatment of malignant disease, especially in patients with SDHB mutations. In some patients, treatment with sunitinib has been associated with partial radiographic response, disease stabilization, decreased fluorodeoxyglucose uptake on positron emission tomography, and improved blood pressure control. These findings have led to the development of prospective clinical trials of new targeted therapies for metastatic disease. Here, we provide an updated review of the clinical and genetic predictors of malignant disease, radiographic diagnosis of malignant disease, and information from the most relevant studies of systemic therapies, as well as proposed treatment guidelines for patients with metastatic or potentially malignant PHs and SPGs.

Translational research in endocrine surgery

This article reviews translational research in endocrine surgery, with a focus on disorders of the thyroid, parathyroids, adrenals, and endocrine pancreas. Discovery of genes responsible for heritable endocrine cancer syndromes has increased knowledge of the causes and mechanisms of endocrine cancer and has refined surgical treatment options. Knowledge of mutations in sporadic cancer has led to rapid progress in small-molecule kinase inhibitor strategies. These breakthroughs and their influence on current therapy are discussed to provide surgeons with an overview of the basic science research currently creating new clinical treatments and improving patient care.

Rare insights into cancer biology

Cancer-associated mutations have been identified in the metabolic genes succinate dehydrogenase (SDH), fumarate hydratase (FH) and isocitrate dehydrogenase (IDH), advancing and challenging our understanding of cellular function and disease mechanisms and providing direct links between dysregulated metabolism and cancer. Some striking parallels exist in the cellular consequences of the genetic mutations within this triad of cancer syndromes, including accumulation of oncometabolites and competitive inhibition of 2-oxoglutarate-dependent dioxygenases, particularly, hypoxia-inducible factor (HIF) prolyl hydroxylases, JmjC domain-containing histone demethylases (part of the JMJD family) and the ten-eleven translocation (TET) family of 5methyl cytosine (5mC) DNA hydroxylases. These lead to activation of HIF-dependent oncogenic pathways and inhibition of histone and DNA demethylation. Mutations in FH, resulting in loss of enzyme activity, predispose affected individuals to a rare cancer, hereditary leiomyomatosis and renal cell cancer (HLRCC), characterised by benign smooth muscle cutaneous and uterine tumours (leiomyomata) and an aggressive form of collecting duct and type 2 papillary renal cancer. Interestingly, loss of FH activity results in the accumulation of high levels of fumarate that can lead to the non-enzymatic modification of cysteine residues in multiple proteins (succination) and in some cases to their disrupted function. Here we consider that the study of rare diseases such as HLRCC, combining analyses of human tumours and cell lines with in vitro and in vivo murine models has provided novel insights into cancer biology associated with dysregulated metabolism and represents a useful paradigm for cancer research.

SDH mutations establish a hypermethylator phenotype in paraganglioma

Paragangliomas are neuroendocrine tumors frequently associated with mutations in RET, NF1, VHL, and succinate dehydrogenase (SDHx) genes. Methylome analysis of a large paraganglioma cohort identified three stable clusters, associated with distinct clinical features and mutational status. SDHx-related tumors displayed a hypermethylator phenotype, associated with downregulation of key genes involved in neuroendocrine differentiation. Succinate accumulation in SDH-deficient mouse chromaffin cells led to DNA hypermethylation by inhibition of 2-OG-dependent histone and DNA demethylases and established a migratory phenotype reversed by decitabine treatment. Epigenetic silencing was particularly severe in SDHB-mutated tumors, potentially explaining their malignancy. Finally, inactivating FH mutations were identified in the only hypermethylated tumor without SDHx mutations. These findings emphasize the interplay between the Krebs cycle, epigenomic changes, and cancer.

Efficacy of everolimus in patients with metastatic insulinoma and refractory hypoglycemia

BACKGROUND

Refractory hypoglycemia in patients with metastatic insulinoma is an important cause of morbidity and mortality. Everolimus could be a new therapeutic option.

METHODS

Within the French Group, we conducted a retrospective, multicentric study of endocrine tumors to evaluate the time to the first recurrence of symptomatic hypoglycemia, after everolimus initiation, in patients with metastatic insulinoma and refractory hypoglycemia. Ongoing hyperglycemic medical options, tumor response, and safety information were recorded.

RESULTS

Twelve patients with metastatic insulinoma and refractory hypoglycemia who were treated with everolimus between May 2007 and June 2011 were reviewed. Everolimus (starting dose, 10 mg/day, except in one patient, 5 mg/day) was given after a median of four previous therapeutic lines. Medication aimed at normalizing blood glucose levels in 11 patients. After a median duration of 6.5 months (range 1-35+ months), median time to the first recurrence of symptomatic hypoglycemia was 6.5 months (range 0 to 35+ months). Three patients discontinued everolimus because of cardiac and/or pulmonary adverse events at 1, 1.5, and 7 months after initiation, which led to two deaths. Three patients discontinued everolimus because of tumor progression at 2, 3, and 10 months after initiation, without recurrence of hypoglycemia.

CONCLUSION

Everolimus appears to be a new effective treatment for patients with metastatic insulinoma and refractory hypoglycemia. Tolerance should be carefully monitored.

Molecular and therapeutic advances in the diagnosis and management of malignant pheochromocytomas and paragangliomas

Pheochromocytomas (PCCs) and paragangliomas (PGLs) are rare catecholamine-secreting tumors derived from chromaffin cells originating in the neural crest. These tumors represent a significant diagnostic and therapeutic challenge because the diagnosis of malignancy is frequently made in retrospect by the development of metastatic or recurrent disease. Complete surgical resection offers the only potential for cure; however, recurrence can occur even after apparently successful resection of the primary tumor. The prognosis for malignant disease is poor because traditional treatment modalities have been limited. The last decade has witnessed exciting discoveries in the study of PCCs and PGLs; advances in molecular genetics have uncovered hereditary and germline mutations of at least 10 genes that contribute to the development of these tumors, and increasing knowledge of genotype-phenotype interactions has facilitated more accurate determination of malignant potential. Elucidating the molecular mechanisms responsible for malignant transformation in these tumors has opened avenues of investigation into targeted therapeutics that show promising results. There have also been significant advances in functional and radiological imaging and in the surgical approach to adrenalectomy, which remains the mainstay of treatment for PCC. In this review, we discuss the currently available diagnostic and therapeutic options for patients with malignant PCCs and PGLs and detail the molecular rationale and clinical evidence for novel and emerging diagnostic and therapeutic strategies.

Bone metastases and skeletal-related events in patients with malignant pheochromocytoma and sympathetic paraganglioma

CONTEXT

Bone metastases (BM) can cause severe pain, spinal cord compression, pathological fractures, and/or hypercalcemia. These skeletal-related events (SREs) may cause immobilization, loss of independence, poor quality of life, and reduced survival. There is limited information on the clinical effects of BM and SREs in patients with malignant pheochromocytoma or sympathetic paraganglioma (PHEO/sPGL).

OBJECTIVES

We studied the prevalence and clinical characteristics of BM and SREs in patients with PHEO/sPGL and investigated the risk factors for SRE development.

DESIGN

Using a large institutional database, we conducted a retrospective study of 128 patients with malignant PHEO/sPGL at The University of Texas MD Anderson Cancer Center from 1967 through 2011.

RESULTS

Of the patients, 91 (71%) had BM, and 57 of these (63%) developed metachronous BM at a median time of 3.4 years (range, 5 months to 23 years) after the primary tumor diagnosis. Metastatic disease was confined exclusively to the skeleton in 26 of 128 (20%) patients. Sufficient information to assess SRE occurrence was available for 67 patients, and 48 of 67 (72%) patients had at least 1 SRE. The median overall survival for the 128 patients was 12 years for patients with only BM, 7.5 years for patients with nonosseous metastases, and 5 years for patients with both BM and nonosseous metastases (log rank test P value = .005). We were unable to identify factors predictive of SRE development, but the occurrence of a first SRE was associated with the development of subsequent SREs in 48% of subjects. In responsive patients, the use of systemic therapy was associated with fewer SREs (P < .0001).

CONCLUSIONS

BM and SREs are frequent in patients with malignant PHEO/sPGL. SREs often develop shortly after the diagnosis of BM; severe pain is the most frequent SRE. These patients should be followed long-term by a multidisciplinary team to promptly identify the need for medical or surgical intervention.

Loss of expression of SDHA predicts SDHA mutations in gastrointestinal stromal tumors

Gastrointestinal stromal tumors (GISTs) are usually driven by mutations in KIT or PDGFRA, although 15% of GISTs in adults and >90% in children lack such mutations. The majority of gastric KIT/PDGFRA wild-type GISTs show distinctive morphological and clinical features and loss of expression of succinate dehydrogenase (SDH) B. Only a small subset of SDHB-deficient GISTs carries loss-of-function mutations in SDHB, SDHC, or SDHD. Because of the complexity of its locus (15 exons) and the presence of three pseudogenes, SDHA is rarely analyzed. Recently, mutations in SDHA were shown to lead to loss of expression of SDHA in a small group of paragangliomas. We sought to determine whether immunohistochemistry for SDHA could identify GISTs with SDHA mutations. Tumors (n=33) with pathological features of SDH-deficient GIST were analyzed for expression of SDHA and SDHB by immunohistochemistry, and SDHA exons were sequenced from tumors lacking SDHA expression. Exons harboring somatic mutations were examined in DNA from corresponding normal tissue. All 33 tumors showed loss of SDHB expression. A total of 9 out of 33 (27%) tumors also lacked expression of SDHA. SDHA-deficient GISTs affected five men and four women (median age 38 years). SDHA expression was intact in the 24 remaining tumors, including those with known SDHB (n=3) or SDHC (n=2) mutations. Nonsense (n=8) or missense (n=1) mutations in SDHA were identified in all SDHA-deficient tumors. Heterozygous mutations were also found in DNA from normal tissues from six patients with available material. Somatic loss of the second allele has been found in seven tumors, five by loss of heterozygosity, one by a 13-bp deletion, and one by a missense mutation. Loss of SDHA expression in GIST reliably predicts the presence of SDHA mutations, which represent a relatively common cause of SDH-deficient GIST in adults. Immunohistochemistry for SDHA can be used to select patients for SDHA-specific genetic testing.

Role of hypoxia and HIF2α in development of the sympathoadrenal cell lineage and chromaffin cell tumors with distinct catecholamine phenotypic features

Hypoxia has wide-ranging impact in normal physiology and disease processes. This stimulus evokes changes in gene expression mediated by transcription factors termed hypoxia-inducible factors (HIFs) that affect numerous processes: angiogenesis, cell survival, cellular metabolism, stem cell self-renewal and multipotency, migration, invasiveness, and metastatic progression in tumor cells. Over the past decade, increasing numbers of reports have emerged documenting differential roles of HIF1α and HIF2α in these processes. In cells of the sympathoadrenal lineage, both HIFs differentially mediate influences of hypoxia on catecholamine synthesis and secretion, but HIF2α signaling has particularly prominent functions in regulating developmental processes of growth and differentiation. This chapter discusses the role of HIF2α and HIF1α in the context of the development, phenotypic features, and functions of chromaffin cells. Moreover, current knowledge about tumor formation in cells of the sympathoadrenal lineage, leading to catecholamine-producing pheochromocytomas and paragangliomas, is analyzed in the light of the HIF2α signaling network.

Trp53 inactivation leads to earlier phaeochromocytoma formation in pten knockout mice

Phaeochromocytomas (PCCs) are benign neuroendocrine tumours of the adrenal medulla. Approximately 10% of PCC patients develop metastases, but this frequency is much higher in specific subtypes of patients. The reliable diagnosis of malignant PCC can only be made after identification of a metastasis. To study the effect of Trp53 inactivation on PCC pathogenesis in Pten KO mice, we investigated the adrenals of a large cohort of mice with conditional monoallelic and biallelic inactivation of Trp53 and Pten. The adrenal weights were determined for all mice, and in a proportion of these mice, immunohistochemistry for tyrosine hydroxylase and dopamine β-hydroxylase was performed on the adrenals and corresponding lungs. Finally, comparative genomic hybridization (CGH) was performed. The histological and immunohistochemical results confirmed that the adrenal tumours were PCCs. Inactivation of one or both alleles of Trp53 resulted in earlier tumour occurrence in the Pten(loxP/loxP) mice as well as in the Pten(loxP/+) mice. In addition, lung metastases were found in up to 67% of mice. The CGH results showed that the most frequent genomic alterations were loss of chromosome 19 (86%) and gain of chromosome 15 (71%). In this study, we have shown that Pten/Trp53 KO mice showed metastatic PCC at high frequency and primary tumours occurred at younger ages in mice with Trp53 inactivation. Therefore, the present model appears to be a suitable model that might allow the preclinical study of new therapeutics for these tumours.

Treatment with sunitinib for patients with progressive metastatic pheochromocytomas and sympathetic paragangliomas

CONTEXT

Patients with progressive metastatic pheochromocytomas (PHEOs) or sympathetic paragangliomas (SPGLs) face a dismal prognosis. Current systemic therapies are limited.

OBJECTIVES

The primary end point was progression-free survival determined by RECIST 1.1 criteria or positron emission tomography with [(18)F]fluorodeoxyglucose/computed tomography ([(18)F]FDG-PET/CT), in the absence of measurable soft tissue targets. Secondary endpoints were tumor response according to RECIST criteria version 1.1 or FDG uptake, blood pressure control, and safety.

DESIGN

We conducted a retrospective review of medical records of patients with metastatic PHEO/SPGL treated with sunitinib from December 2007 through December 2011. An intention-to-treat analysis was performed.

PATIENTS AND SETTING

Seventeen patients with progressive metastatic PHEO/SPGLs treated at the Institut Gustave-Roussy and MD Anderson Cancer Center.

INTERVENTIONS

Patients treated with sunitinib.

RESULTS

According to RECIST 1.1, eight patients experienced clinical benefit; three experienced partial response, and five had stable disease, including four with predominant skeletal metastases that showed a 30% or greater reduction in glucose uptake on [(18)F]FDG-PET/CT. Of 14 patients who had hypertension, six became normotensive and two discontinued antihypertensives. One patient treated with sunitinib and rapamycin experienced a durable benefit beyond 36 months. The median overall survival from the time sunitinib was initiated was 26.7 months with a progression-free survival of 4.1 months (95% confidence interval = 1.4-11.0). Most patients who experienced a clinical benefit were carriers of SDHB mutations.

CONCLUSION

Sunitinib is associated with tumor size reduction, decreased [(18)F]FDG-PET/CT uptake, disease stabilization, and hypertension improvement in some patients with progressive metastatic PHEO/PGL. Prospective multi-institutional clinical trials are needed to determine the true benefits of sunitinib.

Succinate dehydrogenase B subunit immunohistochemical expression predicts aggressiveness in well differentiated neuroendocrine tumors of the ileum

Immunohistochemical loss of the succinate dehydrogenase subunit B (SDHB) has recently been reported as a surrogate biomarker of malignancy in sporadic and familial pheocromocytomas and paragangliomas through the activation of hypoxia pathways. However, data on the prevalence and the clinical implications of SDHB immunoreactivity in ileal neuroendocrine tumors are still lacking. Thirty-one consecutive, advanced primary midgut neuroendocrine tumors and related lymph node or liver metastases from 24 males and seven females were immunohistochemically assessed for SDHB. All patients were G1 tumors (Ki-67 labeling index ≤2%). SDHB immunohistochemistry results were expressed as immunostaining intensity and scored as low or strong according to the internal control represented by normal intestinal cells. Strong positivity for SDHB, with granular cytoplasmatic reactivity, was found in 77% of primary tumors (T), whilst low SDHB expression was detected in 90% of metastases (M). The combined analysis (T+M) confirmed the loss of SDHB expression in 82% of metastases compared to 18% of primary tumors. SDHB expression was inversely correlated with Ki-67 labeling index, which accounted for 1.54% in metastastic sites and 0.7% in primary tumors. A correlation between SDHB expression loss, increased Ki-67 labeling index and biological aggressiveness was shown in advanced midgut neuroendocrine tumors, suggesting a role of tumor suppressor gene.