Role of VEGF-A and its receptors in sporadic and MEN2-associated pheochromocytoma

Tumour microenvironment in pheochromocytoma and paraganglioma

Pheochromocytomas and Paragangliomas (Pheo/PGL) are rare catecholamine-producing tumours derived from adrenal medulla or from the extra-adrenal paraganglia respectively. Around 10-15% of Pheo/PGL develop metastatic forms and have a poor prognosis with a 37% of mortality rate at 5 years. These tumours have a strong genetic determinism, and the presence of succinate dehydrogenase B (SDHB) mutations are highly associated with metastatic forms. To date, no effective treatment is present for metastatic forms. In addition to cancer cells, the tumour microenvironment (TME) is also composed of non-neoplastic cells and non-cellular components, which are essential for tumour initiation and progression in multiple cancers, including Pheo/PGL. This review, for the first time, provides an overview of the roles of TME cells such as cancer-associated fibroblasts (CAFs) and tumour-associated macrophages (TAMs) on Pheo/PGL growth and progression. Moreover, the functions of the non-cellular components of the TME, among which the most representatives are growth factors, extracellular vesicles and extracellular matrix (ECM) are explored. The importance of succinate as an oncometabolite is emerging and since Pheo/PGL SDH mutated accumulate high levels of succinate, the role of succinate and of its receptor (SUCNR1) in the modulation of the carcinogenesis process is also analysed. Further understanding of the mechanism behind the complicated effects of TME on Pheo/PGL growth and spread could suggest novel therapeutic targets for further clinical treatments.

Precision Medicine in Phaeochromocytoma and Paraganglioma

Precision medicine is a term used to describe medical care, which is specifically tailored to an individual patient or disease with the aim of ensuring the best clinical outcome whilst reducing the risk of adverse effects. Phaeochromocytoma and paraganglioma (PPGL) are rare neuroendocrine tumours with uncertain malignant potential. Over recent years, the molecular profiling of PPGLs has increased our understanding of the mechanisms that drive tumorigenesis. A high proportion of PPGLs are hereditary, with non-hereditary tumours commonly harbouring somatic mutations in known susceptibility genes. Through detailed interrogation of genotype-phenotype, correlations PPGLs can be classified into three different subgroups or clusters. Thus, PPGLs serve as an ideal paradigm for developing, testing and implementing precision medicine concepts in the clinic. In this review, we provide an overview of PPGLs and highlight how detailed molecular characterisation of these tumours provides current and future opportunities for precision oncology.

MicroRNAs, Long Non-Coding RNAs, and Circular RNAs: Potential Biomarkers and Therapeutic Targets in Pheochromocytoma/Paraganglioma

Around 40% of pheochromocytomas/paragangliomas (PPGL) harbor germline mutations, representing the highest heritability among human tumors. All PPGL have metastatic potential, but metastatic PPGL is overall rare. There is no available molecular marker for the metastatic potential of these tumors, and the diagnosis of metastatic PPGL can only be established if metastases are found at "extra-chromaffin" sites. In the era of precision medicine with individually targeted therapies and advanced care of patients, the treatment options for metastatic pheochromocytoma/paraganglioma are still limited. With this review we would like to nurture the idea of the quest for non-coding ribonucleic acids as an area to be further investigated in tumor biology. Non-coding RNA molecules encompassing microRNAs, long non-coding RNAs, and circular RNAs have been implicated in the pathogenesis of various tumors, and were also proposed as valuable diagnostic, prognostic factors, and even potential treatment targets. Given the fact that the pathogenesis of tumors including pheochromocytomas/paragangliomas is linked to epigenetic dysregulation, it is reasonable to conduct studies related to their epigenetic expression profiles and in this brief review we present a synopsis of currently available findings on the relevance of these molecules in these tumors highlighting their diagnostic potential.

VEGF-A/VEGF-B/VEGF-C expressions in non-hereditary, non-metastatic phaeochromocytoma

Vascular endothelial growth factor (VEGF) is important in pathogenesis of different cancers. The aim of this study is to investigate the relationships between different VEGFs and clinicopathological factors in patients with phaeochromocytomas. Twenty patients (10 men; 10 women) with non-hereditary, non-metastatic phaeochromocytomas were examined for VEGF mRNA expressions by polymerase chain reaction. The expressions were correlated with the clinical and pathological factors of the patients. In addition, mouse double minute 2 (MDM2) expression in these tumours were studied by immunohistochemistry. High expressions of VEGF-A, VEGF-B, and VEGF-C mRNA were detected in 11 (55%), 9 (45%), and 9 (45%) of the tumours respectively. High expression of VEGF-A in phaeochromocytomas was significantly correlated with the tumour size (p=0.025) but did not correlate with patients' age, gender, and tumour laterality. Besides, there was a trend of VEGF-A expression correlated with MDM2 expression (p=0.064). On the other hand, expressions of VEGF-B and VEGF-C were not significantly correlated with tumour size, patients' age, gender, tumour laterality, and MDM2 expression. In addition, high expressions of VEGF-B and VEGF-A were associated with increase of tumour size (p=0.042). Co-expression of different VEGFs did not correlate with MDM2 expression. To conclude, there is a role for VEGF-A/VEGF-B/VEGF-C in the pathogenesis of non-hereditary, non-metastatic phaeochromocytomas.

Case Report: Malignant Pheochromocytoma Without Hypertension Accompanied by Increment of Serum VEGF Level and Catecholamine Cardiomyopathy

INTRODUCTION

Pheochromocytoma is a catecholamine-producing tumor in the adrenal medulla and is often accompanied by hypertension, hyperglycemia, hypermetabolism, headache, and hyperhidrosis, and it is classified as benign and malignant pheochromocytoma. In addition, persistent hypertension is often observed in subjects with malignant pheochromocytoma.

CASE PRESENTATION

A 52-year-old Japanese male was referred and hospitalized in our institution. He had a health check every year and no abnormalities had been pointed out. In addition, he had no past history of hypertension. In endocrinology markers, noradrenaline level was as high as 7,693 pg/ml, whereas adrenaline level was within normal range. Abdominal contrast-enhanced computed tomography revealed a 50-mm hyper-vascularized tumor with calcification in the right adrenal gland and multiple hyper-vascularized tumors in the liver. In ¹³¹I MIBG scintigraphy, there was high accumulation in the right adrenal gland and multiple accumulation in the liver and bone. In echocardiography, left ventricular ejection fraction was as low as 14.3%. In coronary angiography, however, there was no significant stenosis in the coronary arteries. Based on these findings, we finally diagnosed him as malignant pheochromocytoma accompanied by multiple liver and bone metastases and catecholamine cardiomyopathy. However, blood pressure was continuously within normal range without any anti-hypertensive drugs. Right adrenal tumor resection was performed together with left hepatic lobectomy and cholecystectomy. Furthermore, serum levels of vascular endothelial growth factor (VEGF) and parathyroid (PTH)-related protein were very high before the operation but they were markedly reduced after the operation.

CONCLUSIONS

This is the first report showing the time course of serum VEGF level in a subject with malignant pheochromocytoma, clearly showing that malignant pheochromocytoma actually secreted VEGF. In addition, this case report clearly shows that we should bear in mind once again that malignant pheochromocytoma is not necessarily accompanied by hypertension.

Emerging Treatments for Advanced/Metastatic Pheochromocytoma and Paraganglioma

OPINION STATEMENT

The incidence of metastatic pheochromocytoma (PHEO) and paraganglioma (PGL) may occur in as many as 35% of patients particularly with PGL and even more frequently in those with specific mutations. Biochemical, morphological, and molecular markers have been investigated for use in the distinction of benign from malignant PHEO/PGL. PHEO/PGL metastasizes via hematogenous or lymphatic routes and shows differences based on mutational status. The most common sites of involvement in patients that have an SDHB mutation are the bone (78%), lungs (45%), lymph nodes (36%), and liver (35%). In patients with sporadic PHEO/PGL, the most common sites of metastasis are the bones (64%), lungs (47%), lymph nodes (36%), and liver (32%). Metastases may be present at presentation or may occur later. Metastases to the liver and lungs are associated with a shorter survival. Overall, the estimated 5-year survival rates are between 34 and 74%. Currently, treatments for metastatic PHEO/PGL are essentially palliative. Surgery is potentially curative; however, tumor dissemination limits the chance for a curative resection. When surgical intervention is not amenable, the therapeutic options include radiolabeled MIBG (Azedra®-iobenguane 131 was recently FDA-approved for patients > 12 years and older with iobenguane scan positive) or systemic chemotherapy with cyclophosphamide, vincristine, and dacarbazine (CVD) with an overall objective response rate (ORR) of less than 40%; however, it is not clear if the administration of CVD impacts overall survival, as nearly all patients develop progressive and ultimately fatal disease. Other treatment modalities under investigation include cytoreductive techniques, novel radiopharmaceuticals, chemotherapy, radiotherapy, immunotherapy, and experimental therapies. Here we are discussing emerging treatment for advanced/metastatic PHEO/PGL.

From clinic to mechanism: Proteomics-based assessment of angiogenesis in adrenal pheochromocytoma

Adrenal pheochromocytoma (PCC) is a very rare tumor that stems from chromaffin cells, which can develop into malignant tumor. During the operation, abundant blood vessels were often observed in PCC than other adrenal tumors, which increases the difficulty and risk of the surgery. Therefore, it is important to investigate the mechanism of PCC angiogenesis. Twelve surgical specimens of PCC from Ruijin Hospital, Shanghai Jiaotong University were grouped into high and low microvessel density (MVD) group. They were also divided into rich blood supply and nonenriched blood supply group, according to computed tomography (CT) manifestation. Comparative proteomic analysis based on liquid chromatography-tandem mass spectrometry (LC-MS/MS) and bioinformatics analysis revealed that 206 proteins differentially regulated in the high MVD group compared with low MVD group (p < 0.05). Besides, 61 proteins were discovered to be significantly changed when the 12 samples were grouped according to CT manifestation. By intersecting the differentially changed protein from MVD and CT grouping, 25 proteins were filtered out, with pathological function. COX4I2 was verified to be increased gradually with angiogenesis with increasing severity, and PLAT was shown to be decreased with angiogenesis in PCC, by quantitative reverse-transcription polymerase chain reaction and immunohistochemistry. The quantitative proteomics result indicated that the tumor angiogenesis in PCC is associated with hypoxia. COX4I2 and PLAT were highly correlated with blood supply in PCC which contribute to angiogenesis in PCC, which could be used as biomarkers to better indicate tumor angiogenesis, or targets to regress tumor angiogenesis as treatment.