The significance of angiogenesis in malignant pheochromocytomas

Clinicopathological and genomic analysis of pediatric pheochromocytoma and sympathetic paraganglioma

Pediatric patients with pheochromocytoma (PCC)/paraganglioma (PGL) (PPGL) are rare, and clinicopathological investigations, especially the relationship between gene analysis and histological features, are insufficient. We comprehensively examined the clinical data, germline/somatic variants (mutations), and pathological characteristics of operated tumors using immunohistochemical expression and histological grading by Grading of Adrenal PCC and PGL score. This study included 28 patients (15 males and 13 females) aged <19 years. The age at the diagnosis was 12.8 ± 4.5 years. The included patient often had multiple PPGLs, with 39 tumors, including 21 PCCs and 18 PGLs, with average tumor sizes of 45.0 ± 22.8 and 42.6 ± 23.6 mm, respectively. Genomic types examined by gene mutations and immunohistochemistry of CA9 for VHL, SDHB for SDHx, and MAX for MAX, classified them into 14 VHL (50%), ten SDHx (35.7%), one MAX (3.6%), and three unknown (10.7%) types. Tumor metastasis was limited to two SDHB-related PPGLs, but not to VHL-related PPGLs. In both patients, the metastatic sites were the bones. The average GAPP score of the PPGLs was 2.9 ± 1.5 in VHL and 5.3 ± 1.7 in SDHB, and histological grades were well-differentiated in VHL and moderately differentiated in SDHB. SSTR2 expression was positive in 90% of SDHB-related PPGLs, but negative in 75% and weakly or focally positive in 25% of VHL-related PPGLs. Most pediatric PPGLs (90%) demonstrated mutations in VHL, SDHB, and MAX, with histological features depending on the mutation type. Combined genetic and immunohistochemical examination is desirable for accurate genomic diagnosis, and clinicopathological study.

Expression of Amine Oxidase Proteins in Adrenal Cortical Neoplasm and Pheochromocytoma

We delved into the expression of amine oxidase family proteins and their potential significance in adrenal gland neoplasm. Tissue microarrays were prepared for 132 cases of adrenal cortical neoplasm (ACN) consisting of 115 cases of adrenal cortical adenoma (ACA), 17 cases of adrenal cortical carcinoma (ACC), and 163 cases of pheochromocytoma (PCC). Immunohistochemical stainings for MAOA, MAOB, LOX, and AOC3 were performed to evaluate the H-scores and compare them with clinicopathological parameters. The H-scores of MAOA (T; p = 0.005) and MAOB (T; p = 0.006) in tumor cells (T) were high in ACN, whereas LOX (T, S; p < 0.001) in tumor and stromal cells (S) and AOC3 (T; p < 0.001) were higher in PCC. In stromal cells, MAOA (S; p < 0.001) and AOC3 (S; p = 0.010) were more expressed in ACA than in ACC. MAOB (S) in PCC showed higher H-scores when the grading of adrenal pheochromocytoma and paraganglioma (GAPP) score was 3 or higher (p = 0.027). In the univariate analysis, low MAOA expression in stromal cells of ACN was associated with shorter overall survival (p = 0.008). In conclusion, monoamine oxidase proteins revealed differences in expression between ACN and PCC and also between benign and malignant cells.

Vascular pattern analysis for the prediction of clinical behaviour in pheochromocytomas and paragangliomas

Pheochromocytomas (PCCs) are neuroendocrine tumors arising from chromaffin cells of the adrenal medulla. Related tumors that arise from the paraganglia outside the adrenal medulla are called paragangliomas (PGLs). PCC/PGLs are usually benign, but approximately 17% of these tumors are malignant, as defined by the development of metastases. Currently, there are no generally accepted markers for identifying a primary PCC or PGL as malignant. In 2002, Favier et al. described the use of vascular architecture for the distinction between benign and malignant primary PCC/PGLs. The aim of this study was to validate the use of vascular pattern analysis as a test for malignancy in a large series of primary PCC/PGLs. Six independent observers scored a series of 184 genetically well-characterized PCCs and PGLs for the CD34 immunolabeled vascular pattern and these findings were correlated to the clinical outcome. Tumors were scored as malignant if an irregular vascular pattern was observed, including vascular arcs, parallels and networks, while tumors with a regular pattern of short straight capillaries were scored as benign. Mean sensitivity and specificity of vascular architecture, as a predictor of malignancy was 59.7% and 72.9%, respectively. There was significant agreement between the 6 observers (mean κ = 0.796). Mean sensitivity of vascular pattern analysis was higher in tumors >5 cm (63.2%) and in genotype cluster 2 tumors (100%). In conclusion, vascular pattern analysis cannot be used in a stand-alone manner as a prognostic tool for the distinction between benign and malignant PCC, but could be used as an indicator of malignancy and might be a useful tool in combination with other morphological characteristics.

Both sunitinib and sorafenib are effective treatments for pheochromocytoma in a xenograft model

Pheochromocytomas and paragangliomas are rare neuroendocrine tumors which develop from chromaffin cells of the adrenal medulla and extra-adrenal sites, leading to excess catecholamine release and hypertension. Many of the tumors are characterized by a high vascularity, suggesting the possible implementation of anti-angiogenic therapies for patients. Here, the efficacy of the tyrosine kinase inhibitors sunitinib and sorafenib was investigated in vivo and in vitro. Oral treatment with either sunitinib or sorafenib (40mg/kg/day) for 14days induced a marked reduction in the volume and weight of PC12 pheochromocytoma cell tumor xenografts in mice. Assessment of tumoral neo-angiogenesis, assessed by morphometric analysis of the vascular network after CD31 immunolabeling, showed that both sunitinib and sorafenib reduced the microvessel area (-85% and -80%, respectively) and length (-80% and -78%, respectively) in treated compared to control tumors. In addition, the number of vessel nodes was significantly lower in treated tumors (-95% and -84%, respectively). Furthermore, cleaved caspase 3 immunolabeling revealed a marked increase in the number of apoptotic cells in tumors from treated animals. Sunitinib and sorafenib could exert a direct effect on PC12 cell viability in vitro. While sunitinib induced a rapid (4h) and pronounced (5-fold) increase in caspase-3/7-dependent apoptosis, sorafenib seems to exert its cytotoxic activity through a different mechanism. Altogether, our data demonstrate that sunitinib and sorafenib have the ability to impair pheochromocytoma development by inhibiting angiogenesis and reducing tumor cell viability. These results strongly suggest that both sunitinib and sorafenib could represent valuable therapeutic tools for pheochromocytoma.

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

Pheochromocytoma (PHEO), a rare catecholamine producing tumor arising from the chromaffin cells, may occurs sporadically (76%–80%) or as part of inherited syndromes (20%–24%). Angiogenesis is a fundamental step in tumor proliferation and vascular endothelial growth factor (VEGF-A) is the most well-characterized angiogenic factor. The role of angiogenic markers in PHEO is not fully understood; investigations were therefore made to evaluate the expression of VEGF-A and its receptors in PHEO and correlate to clinical parameters. Twenty-nine samples of PHEO were evaluated for VEGF-A, VEGF receptor-1 (VEGFR-1) VEGFR-2 expression and microvessel density (MVD) by immunohistochemistry. Clinical data were reviewed in medical records. The mean age of patients was 38 ± 14 years, and 69% were woman. VEGF-A, VEGFR-1 and VEGFR-2 staining were detected in nearly all PHEO samples. No significant correlation was observed between VEGF-A, VEGFR-1, VEGFR-2 expression or MVD and age at diagnosis, tumor size or sporadic and hereditary PHEO. However, the levels of expression of these molecules were significantly higher in malignant PHEO samples (p = 0.027, p = 0.003 and p = 0.026, respectively).VEGF-A and its receptors were shown to be up-regulated in malignant PHEO, suggesting that these molecules might be considered as therapeutic targets for unresectable or metastatic tumors.

Study of microvessel density and the expression of vascular endothelial growth factors in adrenal gland pheochromocytomas

Angiogenesis (neoangiogenesis), a process of neovascularization, is an essential step for local tumor growth and distant metastasis formation. We have analysed angiogenesis status: vascular architecture, microvessel density, and vascular endothelial growth factors expression in 62 adrenal pheochromocytomas: 57 benign and 5 malignant. Immunohistochemical evaluation revealed that vascular architecture and vessel density are different in the central and subcapsular areas of the tumor. Furthermore, we have observed a strong correlation between number of macrophages and microvessel density in the central and subcapsular areas of the tumor and between the expression of VEGF-A in tumor cells and microvessel density in central and subcapsular areas of the tumor. Secondary changes in these tumors influence the results and both vascular architecture and microvessel density are markedly disturbed by hemorrhagic and cystic changes in pheochromocytomas. These changes are partially caused by laparoscopic operation technique. However, no differences in vascular parameters were found between pheochromocytomas with benign and malignant clinical behavior. Our observation showed that analysis of angiogenesis, as a single feature, does not help in differentiating malignant and benign pheochromocytomas and has no independent prognostic significance. On the other hand, high microvessel density in pheochromocytoma is a promising factor for antiangiogenic therapy in malignant cases.

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.

Targeting heat shock protein 90 for the treatment of malignant pheochromocytoma

Metastatic pheochromocytoma represents one of the major clinical challenges in the field of neuroendocrine oncology. Recent molecular characterization of pheochromocytoma suggests new treatment options with targeted therapies. In this study we investigated the 90 kDa heat shock protein (Hsp90) as a potential therapeutic target for advanced pheochromocytoma. Both the first generation, natural product Hsp90 inhibitor 17-allylamino-17-demethoxygeldanamycin (17-AAG, tanespimycin), and the second-generation synthetic Hsp90 inhibitor STA-9090 (ganetespib) demonstrated potent inhibition of proliferation and migration of pheochromocytoma cell lines and induced degradation of key Hsp90 clients. Furthermore, ganetespib induced dose-dependent cytotoxicity in primary pheochromocytoma cells. Using metastatic models of pheochromocytoma, we demonstrate the efficacy of 17-AAG and ganetespib in reducing metastatic burden and increasing survival. Levels of Hsp70 in plasma from the xenograft studies served as a proximal biomarker of drug treatment. Our study suggests that targeting Hsp90 may benefit patients with advanced pheochromocytoma.

Sunitinib inhibits catecholamine synthesis and secretion in pheochromocytoma tumor cells by blocking VEGF receptor 2 via PLC-γ-related pathways

Sunitinib is an oral, small molecule multitargeted receptor tyrosine kinase inhibitor with antiangiogenic and antitumor activity that primarily targets vascular endothelial growth factor receptors (VEGFRs). Although sunitinib is an active agent for the treatment of malignant pheochromocytomas, it is unclear whether sunitinib acts through only antiangiogenic mechanisms or also directly targets tumor cells. We previously showed that sunitinib directly induced apoptosis of PC-12 cells. To further confirm these direct effects, we examined the effects of sunitinib on tyrosine hydroxylase (TH) (the rate-limiting enzyme in catecholamine biosynthesis) activity and catecholamine secretion in PC-12 cells and the underlying mechanisms. Sunitinib inhibited TH activity in a dose-dependent manner, and decreased TH protein levels. Consistent with this finding, sunitinib decreased TH phosphorylation at Ser(31) and Ser(40) and significantly decreased catecholamine secretion. VEGFR-2 knockdown attenuated these effects, including inhibition of TH activity and catecholamine secretion, suggesting that they were mediated by VEGFR-2. Sunitinib significantly decreased phospholipase C (PLC)-γ phosphorylation and subsequent protein kinase C (PKC) activity. Because Ser(40) phosphorylation significantly affects TH activity and is known to be regulated by PKC, sunitinib may inhibit Ser(40) phosphorylation via the VEGFR-2/PLC-γ/PKC pathway. Additionally, sunitinib markedly decreased the activity of extracellular signal-regulated kinase (ERK), but not c-Jun NH(2)-terminal kinase or p38 mitogen-activated protein kinase. Therefore, sunitinib may reduce TH Ser(31) phosphorylation through inhibition of the VEGFR-2/PLC-γ/PKC/Raf/mitogen-activated protein kinase/extracellular signal-regulated kinase kinase/ERK pathway. Sunitinib also significantly reduced inositol 1,4,5-trisphosphate production. However, because PC-12 cells do not precisely reflect the pathogenesis of malignant cells, we confirmed the key findings in a human neuroblastoma cell line, SK-N-SH. In conclusion, sunitinib directly inhibits catecholamine synthesis and secretion in pheochromocytoma PC-12 cells.

Sunitinib induces apoptosis in pheochromocytoma tumor cells by inhibiting VEGFR2/Akt/mTOR/S6K1 pathways through modulation of Bcl-2 and BAD

Sunitinib is an oral multitargeted receptor tyrosine kinase inhibitor with antiangiogenic and antitumor activity that mainly targets vascular endothelial growth factor receptors (VEGFRs). Very recently, sunitinib has been shown to be an active agent for the treatment of malignant pheochromocytomas. However, it is unclear whether sunitinib acts only through an antiangiogenic mechanism or whether it may also directly target tumor cells. Sunitinib markedly induced apoptosis of PC12 cells in a dose-dependent and time-dependent manner. Furthermore, in support of these findings, we found that sunitinib induced a reduction in the expression of the antiapoptotic molecule Bcl-2 as well as dephosphorylation of the proapoptotic molecule BAD, which results in the activation of BAD in these cells. Consistent with these apoptotic effects, our results showed that sunitinib inhibited phosphorylation of Akt and mTOR and was followed by a reduction of S6K1, which is a well-known target of mTOR. Knockdown of VEGFR-2 attenuated the sunitinib-induced effects, including apoptosis and inhibition of signaling pathways such as the phosphorylation of Akt as well as mTOR, and Bcl-2, which confirmed that these effects could be mediated by VEGFR-2. In addition, silencing of S6K1 induced apoptosis accompanied by a decrease in the phosphorylation of BAD and Bcl-2, similar to that observed with sunitinib treatment. Thus, these results together suggest that sunitinib initially exerts its apoptotic effect through the inhibition of VEGFR-2, which, when followed by reduction of its downstream effectors, including Akt/mTOR/S6K1, may lead to inhibition of the antiapoptotic molecule Bcl-2 and activation of the proapoptotic molecule BAD in PC12 cells. However, PC12 cells do not precisely reflect the pathogenesis of malignant cells. Therefore, we confirmed the key findings by replicating these experiments in human neuroblastoma SK-N-SH cells.

Rationale for anti-angiogenic therapy in pheochromocytoma and paraganglioma

Pheochromocytomas and paragangliomas are highly vascularized tumors which are candidates for anti-angiogenic therapies. Several studies have reported the association of vascular endothelial growth factor (VEGF) overexpression with malignancy, but none took into account the genetic status of the patients or tumors, which may have a major influence on such observations. Transcriptome studies indeed revealed that pheochromocytomas and paragangliomas can be classified into two major clusters depending on their gene expression profile: Cluster 1 comprises samples associated with a hypoxic signature such as SDHx- and VHL-related tumors and cluster 2 includes RET, NF1, and TMEM127-mutated tumors, as well as most of sporadic tumors. The aim of this study was to provide a comprehensive rationale for the targeting of angiogenesis in patients with malignant forms of the disease. We used in situ hybridization, immunohistochemistry, and microarray gene expression profiling to evaluate angiogenesis and the expression of several angiogenic factors in a large cohort of pheochromocytomas and paragangliomas. We also studied the activation of mTOR by assessing the phosphorylation of its targets, P70 S6 kinase and 4E-BP1. These results were correlated with both malignancy and transcription signature. Our results reveal that cluster 1 tumors display a marked increase in both vascularization and in the expression of major angiogenic molecules, including VEGF, its receptors, HIF2α, Angiopoietin-2, and the endothelin receptors ETA and ETB. These overexpressions were observed in both benign and malignant samples of cluster 1 and thus appeared to be mainly dependent on the pseudo-hypoxic status of these tumors. The mTOR pathway was potentially activated in half of the tumors studied, with a slight increase in cluster 2 pheochromocytomas. Our results suggest that there is a strong rationale for anti-VEGF-based therapeutic strategies in malignant pheochromocytomas and paragangliomas, in particular in those associated with mutations in the SDHB gene.

Adrenal cortical tumors, pheochromocytomas and paragangliomas

Distinguishing adrenal cortical adenomas from carcinomas may be a difficult diagnostic problem. The criteria of Weiss are very useful because of their reliance on histologic features. From a practical perspective, the most useful criteria to separate adenomas from carcinomas include tumor size, presence of necrosis and mitotic activity including atypical mitoses. Adrenal cortical neoplasms in pediatric patients are more difficult to diagnose and to separate adenomas from carcinomas. The diagnosis of pediatric adrenal cortical carcinoma requires a higher tumor weight, larger tumor size and more mitoses compared with carcinomas in adults. Pheochromocytomas are chromaffin-derived tumors that develop in the adrenal gland. Paragangliomas are tumors arising from paraganglia that are distributed along the parasympathetic nerves and sympathetic chain. Positive staining for chromogranin and synaptophysin is present in the chief cells, whereas the sustentacular cells are positive for S100 protein. Hereditary conditions associated with pheochromocytomas include multiple endocrine neoplasia 2A and 2B, Von Hippel-Lindau disease and neurofibromatosis I. Hereditary paraganglioma syndromes with mutations of SDHB, SDHC and SDHD are associated with paragangliomas and some pheochromocytomas.

Development and validation of pheochromocytoma of the adrenal gland scaled score for predicting malignant pheochromocytomas

OBJECTIVES

To evaluate the diagnostic performances of the pheochromocytoma of the adrenal gland scaled score (PASS) proposed in a previous report and that of a logistic model developed in this investigation.

METHODS

In all 130 patients with malignant or assumed benign pheochromocytomas, 15 predictive variables were observed. Receiver operating characteristic (ROC) curve analysis was performed to evaluate the diagnostic performance of PASS. The logistic model was developed using the 15 predictive variables. Its performance was evaluated by calculating the area under the ROC curve and comparing it with that of the PASS.

RESULTS

The PASS had the area under the ROC curve of 0.899 (95% confidence interval 0.844 to 0.954). Of the 15 variables entered in the logistic regression analysis, 9 were retained in the model. The area under the ROC curve for the logistic model was 0.983 (95% confidence interval 0.967 to 0.998).

CONCLUSIONS

ROC analysis indicated that the PASS could be used for the diagnosis of malignant pheochromocytomas. The logistic model was able to improve the diagnostic performance of the PASS using a different variable weighting method. We emphasize, however, that a clinical prospective evaluation is needed to confirm their actual value.

Courses of Malignant Pheochromocytoma: Implications for Therapy

Survival of patients with metastatic pheochromocytoma that have exceeded 30 years without therapy to reduce tumors have been reported. We reviewed the records of 38 patients with malignant pheochromocytoma who had received 131I-metaiodiobenzylguanidine (131I-MIBG) treatments between 1981 and 1996 to evaluate longevity. Survival from diagnosis to last follow-up exceeded 5 years in 21 of 38 (55%) and >or=10 years in 50%. In 17 of 21, the interval from diagnosis to 131I-MIBG therapy was greater than 5 years. Survival following 131I-MIBG was >or=5 years in 12 of 17 and >or=10 years in 7 of 17 patients despite continued evidence of excessive circulating catecholamines. Objective responses to 131I-MIBG therapy were seen in about 30% and were usually of a few years, duration, but one individual exhibited marked reductions in volume and function of tumors that have persisted for 21 years. No feature, including a remission of >5 years following surgical excision, was found to predict prolonged survival. In summary, many patients with malignant pheochromocytoma will follow a course extending over many years. The role of 131I-MIBG therapy in longevity is uncertain, but this radiopharmaceutical reduces evidence of tumors in some patients. Criteria for selecting patients who will benefit from treatment remain to be determined.