Malignant pheochromocytomas and paragangliomas: molecular signaling pathways and emerging therapies

Transcriptome Analysis Reveals Significant Differences in Gene Expression of Malignant Pheochromocytoma or Paraganglioma

Prediction of malignant behavior of pheochromocytoma (PC) or paraganglioma (PG) is of limited value. The Cancer Genome Atlas (TCGA) and the French 'Cortico et Médullosurrénale: les Tumeurs Endocrines' (COMETE) network in Paris (France) facilitate accurate differentiation of malignant PC/PG based on genetic information. Therefore, the objective of this transcriptome analysis is to identify the prognostic genes underlying the differentiation of malignant PC/PG in the TCGA and COMETE databases. TCGA carries data pertaining to multigenomic analysis of 173 PC/PG surgical resection samples while the COMETE cohort contains data involving 188 PC/PG surgical resection samples. Clinical information and mRNA expression datasets were downloaded from TCGA and COMETE databases. Based on eligibility criteria, 58 of 173 PC/PG samples in TCGA and 171 of 188 PC/PG samples collected by the COMETE network were selected. Using Ingenuity Pathway Analysis, the mRNA expression of malignant and benign PC/PG was compared. The 58 samples in TCGA included 11 malignant and 47 benign cases. Among the 171 samples obtained from the COMETE cohort, 19 were malignant and 152 were benign. A comparative analysis of the mRNA expression data of the two databases revealed that 11 up/downregulated pathways involved in malignant PC/PG were related to cancer signaling, metabolic alteration, and prominent mitosis, whereas 6 upregulated genes and 1 downregulated gene were significantly enriched in the functional annotation pathways. The TCGA and COMETE databases showed differences in mRNA expression associated with malignant and benign PC/PG. Improved recognition of prognostic genes facilitates the diagnosis and treatment of PC/PG.

Treatment for Patients With Malignant Pheochromocytomas and Paragangliomas: A Perspective From the Hallmarks of Cancer

Malignant pheochromocytomas and paragangliomas affect a very small percentage of the general population. A substantial number of these patients have a hereditary predisposition for the disease and consequently, bear the risk of developing these tumors throughout their entire lives. It is, however, unclear why some patients with no hereditary predisposition develop these tumors, which frequently share a similar molecular phenotype with their hereditary counterparts. Both hereditary and sporadic tumors usually appear at an early age, and affected people often die before reaching their expected lifespans. Unfortunately, there is currently no systemic therapy approved for patients with this orphan disease. Therefore, pheochromocytomas and paragangliomas are very challenging malignancies. The recognition of genetic and molecular abnormalities responsible for the development of these tumors as well as the identification of effective therapies for other malignancies that share a similar pathogenesis is leading to the development of exciting clinical trials. Tyrosine kinase inhibitors, radiopharmaceutical agents, and immunotherapy are currently under evaluation in prospective clinical trials. A phase 2 clinical trial of the highly specific metaiodobenzylguanidine, iobenguane ¹³¹I, has provided impressive results; this radiopharmaceutical agent may become the first approved systemic therapy for patients with malignant pheochromocytoma and paraganglioma by the United States Food and Drug Administration. Nevertheless, systemic therapies are still not able to cure the disease. This review will discuss the development of systemic therapeutic approaches using the hallmarks of cancer as a framework. This approach will help the reader to understand where research efforts currently stand and what the future for this difficult field may be.

Clinical evaluation and treatment of phaeochromocytoma

Phaeochromocytoma and extra adrenal paraganglioma are rare neuroendocrine tumours and have the potential to secrete adrenaline, noradrenaline and dopamine causing a myriad of clinical symptoms. Prompt diagnosis is essential for clinicians and requires a multidisciplinary specialist approach for the clinical and laboratory investigation, diagnosis, treatment and follow-up of patients. This paper is an integrated review of the clinical and laboratory evaluation and treatment of patients suspected to have phaeochromocytoma or paraganglioma, highlighting recent developments and best practices from recent published clinical guidelines.

Malignancy in Pheochromocytoma or Paraganglioma: Integrative Analysis of 176 Cases in TCGA

Methods of diagnosing malignant pheochromocytoma (PCC) or paraganglioma (PGL) are needed. However, there are no reliable histopathologic criteria to distinguish malignant PCC/PGLs. The recent genomic analysis of The Cancer Genome Atlas (TCGA) provides in-depth information enabling more accurate diagnosis of disease entities. Therefore, we investigated genomic expression differences and mutational differences of malignant PCC/PGLs with TCGA. As of December 2014, TCGA had acquired multigenomic analysis of 176 PCC/PGL samples. Clinical information, mutation status, and 20,531 gene messenger RNA (mRNA) expression dataset of normalized RNA-sequencing mRNA read counts were downloaded from TCGA, and integrated into a table. Of the 176 PCC/PGL samples in the dataset, 14 had metastasis and 162 exhibited no metastasis. mRNA expression and mutations were compared in these two groups. There were 76 males in the dataset of 176 TCGA samples. Mean age was 47.6 ± 15.2 years (19-83 years). There was no significant gender or race difference between metastatic and non-metastatic groups. mRNA expression of malignant PCC/PGLs was upregulated in five pathways of cell cycle (BUB1, BUB1B, CCNB2, CDC2, ESPL1), calcium signaling (CCNB2, CDC2, PRKCB1), regulation of actin cytoskeleton (DIAPH3, FGF18, IQGAP3), gap junction (CDC2, PRKCB1), and phosphatidylinositol (PRKCB1, TTK). Disease-free survival rates were significantly correlated with the presence or absence of mutations, such as RP11-798G7.5, HERC2, SETD2, TGDS, TRHDE, FKBP9, and BMS1. TCGA showed differences in mRNA expression and mutations between metastatic and non-metastatic PCC/PGLs. The improved recognition of genetic causes can help to achieve proper diagnosis and provide appropriate treatment of PCC/PGL.

Sunitinib in the therapy of malignant paragangliomas: report on the efficacy in a SDHB mutation carrier and review of the literature

Metastatic pheochromocytomas (PHEOs) and paragangliomas (sPGLs) are rare neural crest-derived tumors with a poor prognosis. About 50% of them are due to germ-line mutations of the SDHB gene. At present, there is no cure for these tumors. Their therapy is palliative and represented by different options among which antiangiogenic drugs, like sunitinib, have been hypothesized to be effective especially in malignant SDHB mutated tumors. We report the effects of sunitinib therapy in a SDHB mutation carrier affected by a malignant sPGL. During 101 weeks of therapy at different doses, sunitinib was able to cause a partial response and then a stable disease for a total of 78 weeks. This favorable response is the longest, out of the 35 so far reported in the literature, registered in a patient treated exclusively with sunitinib but, similarly to the other responses, the effect was limited in time. From our analysis of the scanty data present in the literature, the effect of sunitinib does not seem to be different among wild-type patients and those carrying a cluster 1 germ-line mutation. Sunitinib seems able to slow the disease progression in some patients with malignant PHEO/PGL and therefore may represent a therapeutic option, although randomized controlled studies are needed to assess its efficacy definitively in the treatment of these aggressive tumors.

Target therapy in metastatic pheochromocytoma: current perspectives and controversies

Most of the pheochromocytomas (PCCs) are benign neoplasms, but when they are malignant, they can be difficult to treat. Despite advances in diagnosis and imaging, it remains an untreatable tumor, when metastases develop. A deeper understanding of the alteration of the specific molecular pathways causing malignant PCCs might hopefully lead in the future to the development of multiple molecular-targeted therapies to treat it successfully. Clinical experience and the use of murine models of metastatic PCCs have helped introduce new experimental treatment options which will significantly help the PCCs community explore novel targeted therapies that have already shown promising results in many other types of tumors.

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.

Combined inhibition of mTORC1 and mTORC2 signaling pathways is a promising therapeutic option in inhibiting pheochromocytoma tumor growth: in vitro and in vivo studies in female athymic nude mice

Several lines of evidence, including the recent discovery of novel susceptibility genes, point out an important role for the mammalian target of rapamycin (mTOR) signaling pathway in the development of pheochromocytoma. Analyzing a set of pheochromocytomas from patients with different genetic backgrounds, we observed and confirmed a significant overexpression of key mTOR complex (mTORC) signaling mediators. Using selective ATP-competitive inhibitors targeting both mTORC1 and mTORC2, we significantly arrested the in vitro cell proliferation and blocked migration of pheochromocytoma cells as a result of the pharmacological suppression of the Akt/mTOR signaling pathway. Moreover, AZD8055, a selective ATP-competitive dual mTORC1/2 small molecular inhibitor, significantly reduced the tumor burden in a model of metastatic pheochromocytoma using female athymic nude mice. This study suggests that targeting both mTORC1 and mTORC2 is a potentially rewarding strategy and supports the application of selective inhibitors in combinatorial drug regimens for metastatic pheochromocytoma.

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.

Combined blockade of signalling pathways shows marked anti-tumour potential in phaeochromocytoma cell lines

Currently, there is no completely effective therapy available for metastatic phaeochromocytomas (PCCs) and paragangliomas. In this study, we explore new molecular targeted therapies for these tumours, using one more benign (mouse phaeochromocytoma cell (MPC)) and one more malignant (mouse tumour tissue (MTT)) mouse PCC cell line - both generated from heterozygous neurofibromin 1 knockout mice. Several PCC-promoting gene mutations have been associated with aberrant activation of PI3K/AKT, mTORC1 and RAS/RAF/ERK signalling. We therefore investigated different agents that interfere specifically with these pathways, including antagonism of the IGF1 receptor by NVP-AEW541. We found that NVP-AEW541 significantly reduced MPC and MTT cell viability at relatively high doses but led to a compensatory up-regulation of ERK and mTORC1 signalling at suboptimal doses while PI3K/AKT inhibition remained stable. We subsequently investigated the effect of the dual PI3K/mTORC1/2 inhibitor NVP-BEZ235, which led to a significant decrease of MPC and MTT cell viability at doses below 50 nM but again increased ERK signalling. Accordingly, we next examined the combination of NVP-BEZ235 with the established agent lovastatin, as this has been described to inhibit ERK signalling. Lovastatin alone significantly reduced MPC and MTT cell viability at therapeutically relevant doses and inhibited both ERK and AKT signalling, but increased mTORC1/p70S6K signalling. Combination treatment with NVP-BEZ235 and lovastatin showed a significant additive effect in MPC and MTT cells and resulted in inhibition of both AKT and mTORC1/p70S6K signalling without ERK up-regulation. Simultaneous inhibition of PI3K/AKT, mTORC1/2 and ERK signalling suggests a novel therapeutic approach for malignant PCCs.

Phase 2 study of everolimus monotherapy in patients with nonfunctioning neuroendocrine tumors or pheochromocytomas/paragangliomas

BACKGROUND

The current study was conducted to evaluate the efficacy and safety of everolimus in the treatment of patients with nonfunctioning neuroendocrine tumors (NETs) or pheochromocytomas/paragangliomas.

METHODS

Patients with histologically confirmed nonfunctioning NETs or pheochromocytomas/paragangliomas and with documented disease progression before study enrollment were eligible for the current study. Everolimus was administered daily at a dose of 10 mg for 4 weeks. Response was assessed by Response Evaluation Criteria In Solid Tumors (RECIST; version 1.0) every 8 weeks. The primary endpoint was the 4-month progression-free survival rate (PFSR). The hypothesis of the current study was that the 4-month PFSR would increase from 50% to 65%. Safety was evaluated using the National Cancer Institute's Common Terminology Criteria for Adverse Events (version 3.0).

RESULTS

A total of 34 patients were enrolled. Of these, 27 patients had nonfunctioning NETs, 5 had pheochromocytomas, and 2 had paragangliomas. The 4-month PFSR was 78%. Partial response (PR) was observed in 3 patients. Twenty-eight patients had stable disease (SD) and 2 patients developed progressive disease (PD). The response rate (RR) and overall disease control rate (DCR) were 9.0% (95% confidence interval [95% CI], 0%-18.6%) and 93.9% (95% CI, 85.8%-100%), respectively. The PFS was 15.3 months (95% CI, 4.6 months-26.0 months). Of the patients with nonfunctioning NETs, 3 achieved a PR and 23 had SD (RR, 11.1%; DCR, 100%); the PFS was 17.1 months (95% CI, 11.1 months-23.0 months) and the 4-month PFSR was 90.0%. Twenty-one patients (80.8%) demonstrated tumor shrinkage. In 7 patients with pheochromocytomas/paragangliomas, 5 achieved SD, and 2 developed PD. The PFS was 3.8 months (95% CI, 0.5 months-7.0 months) and the 4-month PFSR was 42.9%. Four patients demonstrated tumor shrinkage. The major grade 3/4 adverse events were thrombocytopenia (14.7%), hyperglycemia (5.9%), stomatitis (5.9%), and anemia (5.9%).

CONCLUSIONS

Everolimus was associated with high therapeutic efficacy and tolerability in patients with nonfunctioning NETs, and demonstrated modest efficacy in patients with pheochromocytomas/paragangliomas.

Signaling pathways in pheochromocytomas and paragangliomas: prospects for future therapies

There is currently no completely effective therapy available for metastatic pheochromocytomas or paragangliomas. Increasing understanding of the germline and somatic mutations leading to pheochromocytoma and paraganglioma development has revealed crucial insights into the molecular pathology of these tumors. A detailed understanding of the molecular pathway alterations giving rise to pheochromocytomas and paragangliomas should allow for the exploration and development of new effective molecular-targeted therapy options for this rare but frequently fatal malignancy. Molecular analysis has shown that pheochromocytoma/paraganglioma-promoting gene mutations can be divided into two major groups-clusters 1 and 2-following two different routes to tumorigenesis. Cluster 1 mutations are associated with pseudohypoxia and aberrant VEGF signaling while cluster 2 mutations are associated with abnormal activation of kinase signaling pathways such as PI3 kinase/AKT, RAS/RAF/ERK, and mTORC1/p70S6K suggesting relevant targets for novel molecular-targeted therapy approaches which will be discussed in detail in this chapter.

Changing paradigms in the treatment of malignant pheochromocytoma

BACKGROUND

Pheochromocytomas and paragangliomas are intra- and extra-adrenal neoplasms that are rarely malignant. The treatment of those that are malignant has remained a challenge because little was known about the molecular pathways involved in its malignant transformation. Recently, however, the genetic and molecular changes involved in malignant pheochromocytoma have come to be understood.

METHODS

The authors review the recent literature about the changing treatment options for malignant pheochromocytomas and paragangliomas.

RESULTS

Traditional treatments for malignant pheochromocytoma remain unsuccessful. With the advances made in genomics and proteomics, novel pathways in pheochromocytoma carcinogenesis are becoming the targets of new treatment strategies and show promising results.

CONCLUSIONS

Although several studies and clinical trials show great promise for improving the treatment of pheochromocytomas and paragangliomas, the hope is that future collaborative efforts will allow for prospective clinical trials using an evidenced-based approach.

Paraganglioma syndrome type 1 in a patient with Carney-Stratakis syndrome

BACKGROUND

A 33-year-old man was referred to a specialist center with a left neck mass and hypertension. The patient underwent surgery, which confirmed a malignant neck paraganglioma with metastasis to a cervical lymph node. He had no family history of carotid body tumors or pheochromocytoma.

INVESTIGATIONS

Measurements of plasma free metanephrines and chromogranin A; radiographic evaluations with CT, (18)F-fluorodeoxyglucose PET and (123)I-labeled metaiodobenzylguanidine scan; gene analysis for mutations in the SDHD and the KIT gene.

DIAGNOSIS

Paraganglioma syndrome type 1 in a patient with a paraganglioma, bilateral pheochromocytomas and a gastrointestinal stromal tumor with a somatic Asp579del KIT mutation.

MANAGEMENT

The patient underwent surgical excision of all tumors after adequate preparation with alpha and beta blockers. Blood pressure normalized after surgery. The patient is examined regularly with biochemical and radiographic studies, and his follow-up is expected to last throughout life.