Establishment and Characterization of Cell Lines from Primary Culture of Hemangioblastoma Stromal Cells

Context

A well-established cell line of hemangioblastomas (HBs) is still lacking.

Aim

This study aims to explore a stable way to establish primary cell lines of HB stromal cells and investigate the morphological and molecular features of these cells.

Patients and Methods

Specimens of HBs from 13 patients were collected for establishment of primary cell lines of stromal cells. The details on cell culture were described, and the characterizations of cultured cells were conducted by morphological observation, immunocytochemical staining of inhibin-α, brachyury, CD133, CD34, GFAP, CD31, NeuN, CD45, Oligo2, and transmission electron microscopy.

Results

Eleven cases were successfully cultured with a success rate of 84.6%. The cultured cells survived for 10 generations with an estimated doubling time of 77.2 ± 5.89 h. Light microscopy revealed that these cells showed vigorous growth status and presented as polygons or trigons with significant heterogeneity. The immunocytochemical staining showed that inhibin-α, brachyury, CD133, and CD34 were expressed in all the cultured cells, whereas the expression of GFAP, CD31, NeuN, CD45, and Oligo2 was all negative. Transmission electron microscopy confirmed that the cultured cells were stromal cells with typical lipid droplets. The phenomenon of lysosomal autophagy was commonly observed without apoptotic cells in late stage.

Conclusion

Appropriate selection of tumor specimens, short duration of devascularization, ideal digestion time, and nutritious medium are critical points for establishment of primary cell line of HB stromal cells. Stromal cells from both von Hippel-Lindau disease-related HBs and sporadic HBs might originate from embryologically arrested hemangioblasts.

Intermixed arteriovenous malformation and hemangioblastoma: case report and literature review

We report the third presentation of an intermixed arteriovenous malformation and hemangioblastoma. The rare occurrence of the diagnostic histologic features of both a neoplasm and vascular malformation in a single lesion is more common in gliomas, as angioglioma, and is termed an 'intermixed' lesion. We review the literature concerning the developmental biology of each lesion, and potential interplay in the formation of an intermixed vascular neoplasm and vascular malformation. The roles of cellular origin, genetic susceptibility, favourable microenvironment, altered local gene expression and key regulatory pathways are reviewed. Our review supports angiography and genetic profiling in intermixed lesions to inform management strategies. Consideration should be given to multimodality therapeutic interventions as required, including microsurgical resection, stereotactic radiosurgery and further research to exploit emerging molecular targets.

Stromal cells of hemangioblastomas exhibit mesenchymal stem cell-derived vascular progenitor cell properties

Hemangioblastoma is composed of neoplastic stromal cells and a prominent capillary network. To date, the identity of stromal cells remains unclear. Mesenchymal stem cells can give rise to committed vascular progenitor cells, and ephrin-B2/EphB4 and Notch signaling have crucial roles in these steps. The aim of our study was to elucidate that stromal cells of central nervous system hemangioblastomas have mesenchymal stem cell-derived vascular progenitor cell properties. Ten hemangioblastomas were investigated immunohistochemically. CD44, a mesenchymal stem cell marker, was detected in stromal cells of all cases, suggesting that stromal cells have mesenchymal stem cell-like properties. Neither CD31 nor α-SMA was expressed in stromal cells, suggesting that stromal cells have not acquired differentiated vascular cell properties. Both ephrin-B2 and EphB4, immature vascular cell markers, were detected in stromal cells of all cases. Jagged1, Notch1, and Hesr2/Hey2, which are known to be detected in both immature endothelial cells and mural cells, were expressed in stromal cells of all cases. Notch3, which is known to be detected in differentiating mural cells, was also expressed in all cases. These results suggest that stromal cells also have vascular progenitor cell properties. In conclusion, stromal cells of hemangioblastomas exhibit mesenchymal stem cell-derived vascular progenitor cell properties.

Role of Endothelial-to-Mesenchymal Transition in the Pathogenesis of Central Nervous System Hemangioblastomas

OBJECTIVE

Hemangioblastomas (HBs) are benign vascular tumors of the central nervous system and histologically contain abundant microvessels. Therefore, they clinically exhibit vascular malformation-like characteristics. It has been described that endothelial-to-mesenchymal transition (EndMT) contributes to the pathogenesis of cerebral cavernous malformations. However, it remains unknown whether EndMT contributes to the pathogenesis of central nervous system HBs. The aim of our study was to investigate whether EndMT occurs in central nervous system HBs.

METHODS

Ten central nervous system HBs were immunohistochemically investigated.

RESULTS

Cluster of differentiation (CD) 31 (an endothelial marker) and EndMT markers, such as α-smooth muscle actin (a mesenchymal marker) and CD44 (a mesenchymal stem cell marker), were expressed in the endothelial layer of microvessels in all cases. These findings suggest that endothelial cells (ECs) of microvessels in central nervous system HBs have acquired mesenchymal and stem cell-like characteristics and undergone EndMT. In all cases, both ephrin-B2 and EphB4, which are not detected in adult normal brain vessels, were expressed in the endothelial layer of microvessels. These data suggest that ECs of microvessels in central nervous system HBs are immature or malformed cells and have both arterial and venous characteristics.

CONCLUSIONS

To our knowledge, this is the first report showing the possibility that EndMT contributes to the pathogenesis of central nervous system HBs. It is likely that ECs of microvessels in central nervous system HBs are immature or malformed cells and have both arterial and venous characteristics. EndMT is expected to be a new therapeutic target in central nervous system HBs.

Extraneuraxial Hemangioblastoma: Clinicopathologic Features and Review of the Literature

Extraneuraxial hemangioblastoma occurs in nervous paraneuraxial structures, somatic tissues, and visceral organs, as part of von Hippel-Lindau disease (VHLD) or in sporadic cases. The VHL gene plausibly plays a key role in the initiation and tumorigenesis of both central nervous system and extraneuraxial hemangioblastoma, therefore, the underlying molecular and genetic mechanisms of the tumor growth are initially reviewed. The clinical criteria for the diagnosis of VHLD are summarized, with emphasis on the distinction of sporadic hemangioblastoma from the form fruste of VHLD (eg, hemangioblastoma-only VHLD). The world literature on the topic of extraneuraxial hemangioblastomas has been comprehensively reviewed with ∼200 cases reported to date: up to 140 paraneuraxial, mostly of proximal spinal nerve roots, and 65 peripheral, 15 of soft tissue, 6 peripheral nerve, 5 bone, and 39 of internal viscera, including 26 renal and 13 nonrenal. A handful of possible yet uncertain cases from older literature are not included in this review. The clinicopathologic features of extraneuraxial hemangioblastoma are selectively presented by anatomic site of origin, and the differential diagnosis is emphasized in these subsets. Reference is made also to 10 of the authors' personal cases of extraneuraxial hemangioblastomas, which include 4 paraneuraxial and 6 peripheral (2 soft tissue hemangioblastoma and 4 renal).

A Comprehensive Procedure to Evaluate the In Vitro Performance of the Putative Hemangioblastoma Neovascularization Using the Spheroid Sprouting Assay

The inactivation of the von Hippel-Lindau (VHL) tumor suppressor gene plays a crucial role in the development of hemangioblastomas (HBs) within the human central nervous system (CNS). However, both the cytological origin and the evolutionary process of HBs (including neovascularization) remain controversial, and anti-angiogenesis for VHL-HBs, based on classic HB angiogenesis, have produced disappointing results in clinical trials. One major obstacle to the successful clinical translation of anti-vascular treatment is the lack of a thorough understanding of neovascularization in this vascular tumor. In this article, we present a comprehensive procedure to evaluate in vitro whether classic tumor angiogenesis exists in HBs, as well as its role in HBs. With this procedure, researchers can accurately understand the complexity of HB neovascularization and identify the function of this common form of angiogenesis in HBs. These protocols can be used to evaluate the most promising anti-vascular therapy for tumors, which has high translational potential either for tumors treatment or for aiding in the optimization of the anti-angiogenic treatment for HBs in future translations. The results highlight the complexity of HB neovascularization and suggest that this common form angiogenesis is only a complementary mechanism in HB neovascularization.

Whole exome sequencing identified genetic variations in Chinese hemangioblastoma patients

Hemangioblastomas (HBs) are uncommon tumors characterized by the presence of inactivating alterations in the von Hippel-Lindau (VHL) gene in inherited cases and by infrequent somatic mutation in sporadic entities. We performed whole exome sequencing on 11 HB patients to further elucidate the genetics of HBs. A total of 270 somatic variations in 219 genes, of which there were 86 mutations in 67 genes, were found in sporadic HBs, and 184 mutations were found in 154 genes in familial HBs. C: G>T: A and T: A>C: G mutations are relatively common in most HB patients. Genes harboring the most significant mutations include PCDH9, KLHL12, DCAF4L1, and VHL in sporadic HBs, and ZNF814, DLG2, RIMS1, PNN, and MUC7 in familial HBs. The frequency of CNV varied considerably within sporadic HBs but was relatively similar within familial HBs. Five genes, including OTOGL, PLCB4, SCEL, THSD4, and WWOX, have CNVs in the six patients with sporadic HBs, and three genes, including ABCA6, CWC27, and LAMA2, have CNVs in the five patients with familial HBs. We found new genetic mutations and CNVs that might be involved in HBs; these findings highlight the complexity of the tumorigenesis of HBs and pinpoint potential therapeutic targets for the treatment of HBs.

Endothelial cells by inactivation of VHL gene direct angiogenesis, not vasculogenesis via Twist1 accumulation associated with hemangioblastoma neovascularization

Inactivation of the VHL tumour suppressor gene is a highly frequent genetic event in the carcinogenesis of central nervous system-(CNS) hemangioblastomas (HBs). The patterning of the similar embryonic vasculogenesis is an increasing concern in HB-neovascularization, and the classic vascular endothelial growth factor (VEGF)-mediated angiogenesis driven by VHL loss-of-function from human endothelium have been questioned. With this regard, we identify a distinct, VHL silencing-driven mechanism in which human vascular endothelial cells by means of increasing cell proliferation and decreasing cell apoptosis, is concomitant with facilitating accumulation of Twist1 protein in vascular endothelial cells in vitro. Importantly, this molecular mechanism is also pinpointed in CNS-HBs, and associated with the process of HB-neovascularization. In contrast with recent studies of HB-neovascularization, these modified cells did not endow with the typical features of vasculogenesis, indicating that this is a common angiogenesis implementing the formation of the vascular network. Taken together, these findings suggest that vasculogenesis and angiogenesis may constitute complementary mechanisms for HB-neovascularization, and could provide a rational recognition of single anti-angiogenic intervention including targeting to the Twist1 signalling for HBs.

Neuroprotective effects respond to cerebral ischemia without susceptibility to HB-tumorigenesis in VHL heterozygous knockout mice

The von Hippel-Lindau (VHL) tumor suppressor gene plays a prominent role in the development of hemangioblastomas (HBs) within specific regions of the human' central nervous system (CNS). Alterations in VHL gene are rarely observed in the more common features of human VHL-related tumors in animal models, and VHL heterozygous knockout (VHL+/-) mice do not develop HBs. We tested whether VHL heterozygous knockout mice exhibited genetic predisposition to the development of HBs and conferred a selective advantage involving growth of blood vessels to its carrier. No differences were observed between wild-type and VHL+/- mice in development ad reproduction. The heterozygous VHL+/- mice did not develop higher genetic susceptibility to CNS-HBs over their lifetime. Furthermore, this recessive VHL gene heterozygosity is relatively stable. Interestingly, we found these heterozygous VHL+/- mice gained an advantage conferring to angiogenic ability in a particular environment, compared with wild-type mice. The heterozygous VHL+/- mice obviously enhanced hypoxia inducible factor-1 (HIF)-dependent and Twist1 angiogenic mechanism in response to acute cerebral ischemia, resulting in decreased cerebral tissue damage and neuroprotective response through neovascularization. Our findings provide evidence of partial loss function of VHL as a novel precise therapeutic target in acute cerebral ischemia.

Specific immunohistochemical pattern of carbonic anhydrase IX is helpful for the diagnosis of CNS hemangioblastoma

Hemangioblastomas are rare capillary-rich tumors predominantly found in the CNS. The histological appearance of these tumors varies across a broad spectrum. Several entities show considerable histomorphological similarities to hemangioblastomas. Therefore, morphological evaluation can be challenging. In this study, we evaluated the diagnostic utility of immunohistochemistry using antibodies against carbonic anhydrase IX and cytokeratin staining. Within our files, we identified 20 hemangioblastomas. A collection of 46 other tumors relevant to the differential diagnosis (12 pilocytic astrocytomas, 11 meningiomas, one pleomorphic xanthoastrocytoma, one angiomatous fibrous histiocytoma, 14 carcinoma metastases and seven gliomas grades II-IX) served as control. The pattern of strong, diffuse expression of carbonic anhydrase IX with membranous accentuation in combination with keratin negativity was considered diagnostic for hemangioblastomas. It was found in 18 out of 20 (90%) hemangioblastomas and in none of the control cases (P < 0.001). This resulted in a sensitivity of 90% and a specificity of 100%. The positive and negative predictive values were 100% and 96%, respectively. Carbonic anhydrase IX with cytokeratin is thus a highly sensitive and specific marker combination for hemangioblastomas. It is therefore very helpful in the diagnosis of these tumors and in their discrimination from other entities.

Hypoxia mediated expression of stem cell markers in VHL-associated hemangioblastomas

Hemangioblastomas of the retina, central nervous system, and kidney are observed in patients with mutations in the von Hippel-Lindau (VHL) tumor suppressor gene. Mutations in the VHL lead to constitutive activation of hypoxia-inducible-factor (HIF) pathway. HIF-mediated expression of pro-angiogenic genes causes extensive pathological neovascularization in hemangioblastomas. A number of studies have shown coexistence of pro-angiogenic and stem cell markers in 'tumorlet-like stromal cells' in the retinal and optic nerve hemangioblastomas, leading to suggestions that hemangioblastomas originate from developmentally arrested stem cells or embryonic progenitors. Since recent studies have shown that the HIF pathway also plays a role in the maintenance/de-differentiation of normal and cancerous stem cells, we evaluated the role of the HIF pathway in the expression of stem cell markers in VHL-/- renal cell carcinoma cells under normoxia or VHL+/+ retinal pigment epithelial cells under hypoxia. Here we show that the expression of stem cell markers in hemangioblastomas is due to activation of the HIF pathway. Further, we show that honokiol, digoxin, and doxorubicin, three recently identified HIF inhibitors from natural sources, blocks the expression of stem cell markers. Our results show the mechanism for the cytological origin of neoplastic stromal cells in hemangioblastomas, and suggest that inhibition of the HIF pathway is an attractive strategy for the treatment of hemangioblastomas.

Nervous system involvement in von Hippel-Lindau disease: pathology and mechanisms

Patients with von Hippel-Lindau disease carry a germline mutation of the Von Hippel-Lindau (VHL) tumor-suppressor gene. We discuss the molecular consequences of loss of VHL gene function and their impact on the nervous system. Dysfunction of the VHL protein causes accumulation and activation of hypoxia inducible factor (HIF) which can be demonstrated in earliest stages of tumorigenesis and is followed by expression of VEGF, erythropoietin, nitric oxide synthase and glucose transporter 1 in VHL-deficient tumor cells. HIF-independent functions of VHL, epigenetic inactivation of VHL, pVHL proteostasis, and links between loss of VHL function and developmental arrest are also described. A most intriguing feature in VHL disease is the occurrence of primary hemangioblastic tumors in the nervous system, the origin of which has not yet been entirely clarified, and current hypotheses are discussed. Endolymphatic sac tumors may extend into the brain, but originally arise from proliferation of endolymphatic duct/sac epithelium; the exact nature of the proliferating epithelial cell, however, also has remained unclear, as well as the question why tumors almost consistently develop in the intraosseous portion of the endolymphatic sac/duct only. The epitheloid clear cell morphology of both advanced hemangioblastoma and renal clear cell carcinoma can make the differential diagnosis challenging, recent developments in immunohistochemical differentiation are discussed. Finally, metastasis to brain may not only be caused by renal carcinoma, but may derive from VHL disease-associated pheochromocytoma/paraganglioma, or pancreatic neuroendocrine tumor.

Hemangioblastoma stromal cells show committed stem cell phenotype

BACKGROUND

Hemangioblastomas are benign vascular tumors of the central nervous system that occur sporadically or in association with von Hippel-Lindau disease. These tumors are characteristically composed of a dense capillary network with intervening stromal/interstitial cells. To date, the histogenesis of hemangioblastoma remains unclear. We hypothesize that hemangioblastomas arise from a defective mesodermal stem cell, which gives rise to the atypical vasculature.

METHODS

To test our hypothesis, we have characterized the cellular composition of hemangioblastomas by immunophenotyping pluripotent and committed stem cells and vascular endothelial cells.

RESULTS

Our findings show that hemangioblastoma endothelial cells are positive for CD133, a stem and progenitor cell marker. Vascular endothelial cells also expressed nuclear Oct4. In addition to the endothelium, both CD133 and Oct4 were present in stromal and perivascular cells. Interestingly, neither the endothelium nor the stromal cells expressed Sox2 or Nanog suggesting a committed stem cell phenotype.

CONCLUSIONS

From these findings, we believe that hemangioblastoma stromal cells are committed stem cells producing both vascular cell types. The findings also show an unusual CD133-positive endothelial phenotype in hemangioblastoma.