Vascular endothelial growth factor, basic fibroblast growth factor and epithelial growth factor receptor in peripheral nerve sheath tumors of neurofibromatosis type 1

BACKGROUND/AIM

Neurofibromas, benign tumors of the nerve sheaths, are the hallmark of neurofibromatosis type 1 (NF1), an autosomal-dominant inherited tumor predisposition syndrome. Malignant tumors arising from nerve sheath cells are an important factor influencing the life expectancy of NF1 patients. Expression of growth factors and growth factor receptors play a key role in the development of tumors. Therapy of peripheral nerve sheath (PNS) tumors is predominantly surgical. The outcome in malignant entities of NF1-affected patients remains poor, despite many efforts to implement pharmacological therapy into the treatment modalities. Growth of peripheral nerve sheath tumors is finely-adjusted by growth factors and PNS tumors express growth factor receptors. However, quantification of receptor expression and comparison to the expression of other related factors are not available. The aim of the present study was to determine growth factor expression relevant for growth control in neurofibromas of NF1.

MATERIALS AND METHODS

Fifty-eight dermal, dermal/diffuse and plexiform neurofibromas and malignant peripheral nerve sheath tumors (MPNST) of NF1-affected patients were analyzed immunohistochemically for the expression of growth factors relevant for angiogenesis: vascular endothelial growth factor (VEGF), basic fibroblast growth factor (bFGF) and epithelial growth factor receptor (EGFR). The vessel density was also determined quantitatively by light microscopy.

RESULTS

Plexiform neurofibroma revealed a higher expression level for VEGF compared to dermal/diffuse neurofibroma. However, statistical significant differences for VEGF expression and of all other proteins investigated were found in comparison to MPNST only. EGFR expression was remarkably high in NF1 patients in their first decade of life. However, this result has to be interpreted with caution in view of the high number of young patients with MPNST in this age group. Vessel density correlated with tumor type. Vessel density increased significantly comparing benign nerve sheath tumors and MPNST (p<0.05).

DISCUSSION/CONCLUSION

This study revealed the presence of factors and receptors involved in angiogenesis as a prerequisite for tumor development and maintenance of PNS in NF1. These factors are highly expressed in all tumors of this study. This study reveals these relevant factors in nerve sheath tumors and also described the significant increase of vessel density in MPNST compared to benign counterparts. Anti-angiogenic drugs are presently investigated for application in NF1 tumor treatment, in particular for patients with a surgically-intractable high tumor burden. Drugs capable of blocking the EGFR receptor-mediated pathway are promising tools within the pharmacological repertoires to treat these patients.

An orthotopic xenograft model of intraneural NF1 MPNST suggests a potential association between steroid hormones and tumor cell proliferation

Malignant peripheral nerve sheath tumors (MPNST) are the most aggressive cancers associated with neurofibromatosis type 1 (NF1). Here we report a practical and reproducible model of intraneural NF1 MPNST, by orthotopic xenograft of an immortal human NF1 tumor-derived Schwann cell line into the sciatic nerves of female scid mice. Intraneural injection of the cell line sNF96.2 consistently produced MPNST-like tumors that were highly cellular and showed extensive intraneural growth. These xenografts had a high proliferative index, were angiogenic, had significant mast cell infiltration and rapidly dominated the host nerve. The histopathology of engrafted intraneural tumors was consistent with that of human NF1 MPNST. Xenograft tumors were readily examined by magnetic resonance imaging, which also was used to assess tumor vascularity. In addition, the intraneural proliferation of sNF96.2 cell tumors was decreased in ovariectomized mice, while replacement of estrogen or progesterone restored tumor cell proliferation. This suggests a potential role for steroid hormones in supporting tumor cell growth of this MPNST cell line in vivo. The controlled orthotopic implantation of sNF96.2 cells provides for the precise initiation of intraneural MPNST-like tumors in a model system suitable for therapeutic interventions, including inhibitors of angiogenesis and further study of steroid hormone effects on tumor cell growth.

Multiple filum terminale hemangioblastomas symptomatic during pregnancy

✓Hemangioblastomas are low-grade, highly vascular tumors commonly associated with von Hippel–Lindau (VHL) syndrome and most often appearing in the cerebellum. They very rarely occur in the spinal nerve roots, and an origin in the filum terminale is exceptional with no instances of multiple hemangioblastomas of the filum terminale reported in the literature. Because of their vascular nature, these lesions can enlarge and become symptomatic in the context of the changes that take place during pregnancy, as has been noted with cerebellar hemangioblastomas. In any case, the evolution of spinal hemangioblastomas during pregnancy is not well known given its rarity. The conjunction of both processes—that is, multiple hemangioblastomas arising in the filum terminale and pregnancy—is unique. The authors describe the case of a 41-year-old woman with multiple hemangioblastomas of the filum terminale and no other evidence of VHL syndrome, in whom pregnancy precipitated symptoms. The interruption of gestation led to a remission of the symptoms. The literature concerning filum terminale hemangioblastomas and pregnancy is also reviewed.

Hemangioblastoma of filum terminale associated with arteriovenous shunting

BACKGROUND

Spinal arteriovenous shunt typically presents in middle age or in the elderly with a strong male predilection. The clinical presentation is usually progressive neurological deficits such as paraparesis or incontinence due to cord edema, although back pain is also a common presentation. Progress of neurological deficit is typically stopped by occlusion of the shunt (surgically or endovascularly), but the return of loss of function may be found in less than half of these patients. In contrast, spinal hemangioblastomas usually occur in adults, and the most common presentation is pain with radiculopathy. Location in the filum terminale is very rare.

CASE DESCRIPTION

After a review of the medical literature, we identified 7 cases of hemangioblastomas arising from the filum terminale (Am J Neuroradiol. 2005;26:936-945; Acta Neurochir [Wien]. 2000;142:1059-1062; J Neurosurg Sci. 2001;45:58-62; J Clin Neurosci. 2006;13:285-288; Neurosurgery. 1999;44:220-223; Clin Neurol Neurosurg. 1985;87:55-59). We report an additional case of a filum terminale hemangioblastoma occurring in a 64-year-old man with 1 month exacerbation of chronic low back pain. Preoperatively, it was misdiagnosed as filum terminale arteriovenous fistula.

CONCLUSION

Even with modern imaging, preoperative diagnosis can still be difficult.

A patient with a VEGF and endostatin producing gastrointestinal autonomic nerve tumour

Tumour associated neovascularisation has been characterised as chaotic and insufficient. This report details the results of the analysis of angiogenic factors in tumour cyst fluid, pleural fluid, and blood from a patient with a gastrointestinal autonomic nerve tumour. The tumour produced vascular endothelial growth factor and endostatin in large quantities, which may explain the dysfunctional angiogenesis and tendency to bleeding seen in this tumour type.

In vivo angiogenic activity of neuroblastoma correlates with MYCN oncogene overexpression

Neuroblastoma (NB) is the most common malignant solid tumor in early childhood. Amplification of the MYCN oncogene is associated with a more malignant course of disease and poor outcome. The role that MYCN plays in the regulation of angiogenesis in NB remains unclear. To better elucidate this matter, fresh biopsy samples from 21 patients, 10 with MYCN-amplified tumors (defined as having >10 copies of the oncogene) and 11 with nonamplified tumors, were tested for their angiogenic capacity using the chick embryo chorioallantoic membrane assay, a useful model for such investigation. Moreover, using the same experimental model, conditioned media obtained from 5 different human NB cell lines MYCN-amplified (HTLA-230, LAN-5 and GI-LI-N) or nonamplified (ACN and SH-SY5Y) and biopsy fragments obtained from xenografts derived from 4 NB cell lines (HTLA-230, GI-LI-N, ACN and SH-SY5Y) injected in nude mice were assayed for angiogenic potential. Our results clearly demonstrated that MYCN amplification parallels angiogenesis in NB. When fresh biopsy samples from patients, CM derived from NB cell lines and biopsy fragments derived from xenografts of the same cell lines injected in nude mice were tested, the response was univocal: the angiogenic response, evaluated both macroscopically and microscopically, was significantly higher in the MYCN-amplified specimens compared to the nonamplified ones.

Ischemia and failed regeneration in chronic experimental neuromas

Neuromas are generally considered to be swollen uniform collections of uncontrolled aberrantly sprouting axons. In early experimental neuromas, there are substantial rises in local blood flow associated with their formation, but human studies of chronic lesions have suggested that neuromas develop ischemia and become impediments to regeneration. The issue is important because traumatically severed human nerves are frequently considered for repair some time after injury, when neuroma formation has occurred. In this work, we examined local perfusion, axon penetration and other characteristics of long-term (6 month) experimental neuromas created by sciatic nerve transection and resection of the distal sciatic nerve and its branches. The scenario was designed to model prior transection in a human nerve, where late surgical reconnection might be contemplated. Local blood flow in the extrinsic plexus of neuromas, examined using a laser Doppler flowmetry probe, declined in distal portions of the stump to values considerably lower than observed in intact nerves. Intrinsic blood flow near the stump tip, examined using microelectrode hydrogen clearance polarography was highly nonuniform and included zones with very low perfusion. Correlated with these findings were nonuniform histological features with zones of absent axons and blood vessels, progressive distal disorganization, marked declines in distal axon penetration, nonremodelled microfascicles and persistent expression of 'regenerative' axon and Schwann cell markers. Uncontrolled axon sprouting was not a feature. Longstanding neuromas include zones of relative ischemia and limited axon penetration that develop in the absence of nerve trunk reconnection. These features would limit their suitability for later repair.

Paraganglioma of the cauda equina: MR findings. One case

Paraganglioma of the filum terminale is a rare tumor but well described in the neurosurgery and pathology literature. Few MRI reports are mentioned. Paraganglioma, often misdiagnosed with ependymoma or schwannoma on MRI images, must be kept in mind, when a highly vascular lesion with serpentine vessels is observed.

Exogenous opioids influence the microcirculation of injured peripheral nerves

Local microvessels of peripheral nerve trunks (vasa nervorum) dilate following capsaicin-induced inflammation or local nerve trunk injury. In previous work, we observed that morphine blocked capsaicin-induced dilation of vasa nervorum presumably through the action of local opioid receptors. In the present work, we studied injury-related hyperemia of the rat sciatic vasa nervorum using laser Doppler and hydrogen clearance microelectrode measurements of local perfusion. Systemic morphine reversed hyperemia by vasoconstricting both extrinsic and intrinsic microvessels supplying 48-h-old "neuroma" preparations or crush zones of peripheral nerve trunks. Morphine did not constrict microvessels of contralateral uninjured or sham exposed but uninjured sciatic nerves. In contrast to the injured nerves, contralateral uninjured nerves exposed to morphine frequently had a rise in local perfusion, indicating vasodilation. The vasoconstrictive actions of morphine were blocked by pretreatment with naloxone and were not mimicked by saline injections alone. Systemic doses of selective opioid agonists to mu-, kappa-, and delta-receptors also selectively constricted microvessels of injured nerves. Local blood flow in older experimental neuromas at 7 days had partial sensitivity to morphine, whereas at 14 days perfusion flow was not influenced by morphine. Exogenous opioids dampen early but not later inflammatory microvasodilation and could have important influences on the nerve regenerative milieu.

Proliferative activity, angiogenesis, and necrosis in peripheral nerve sheath tumors: a quantitative evaluation for prognosis

Malignant peripheral nerve sheath tumors (MPNSTs) are distinguished from a control group of typical benign schwannomas and neurofibromas on the basis of a set of quantitatively evaluated parameters, i.e., the cell density; the number of mitoses and apoptotic bodies; the nuclear area and shape; the number and absolute and relative areas of silver-staining nucleolar organizer regions; necrosis; and angiogenesis. Only the extent of tumor necrosis, the mitotic rate, and the parameters related to silver-staining nucleolar organizer regions discriminate between less aggressive MPNSTs (disease-free patients after 4 years of follow-up) and more aggressive MPNSTs (with recurrences or metastases during the first 4 years of follow-up).

Evidence for CGRP accumulation and activity in experimental neuromas

Calcitonin gene-related peptide (CGRP) is a potent vasodilator and widely distributed neuropeptide that may participate in the injury response of peripheral nerve. We examined evidence for the presence of CGRP immunoreactivity (IR) and its activity in experimental neuromas of Sprague-Dawley rats created by sectioning the midsciatic nerve with resection of 2-3 cm of its distal portion and branches. CGRP activity was evaluated by measuring local blood flow in neuromas using hydrogen polarography and laser-Doppler flowmetry. At all time points studied after nerve section (24 h, 48 h, 7 days, 14 days) there was a rise in local blood flow in the neuroma stumps. At 48 h the hyperemia was maximum but was reversed by topical application of human CGRP(8--37), a specific CGRP-receptor antagonist. CGRP presence was evaluated by immunohistochemistry and radioimmunoassay (RIA). At 24 and 48 h, CGRP IR was intense and distributed in a globular and diffuse pattern apparently not confined to discrete axonlike profiles. At 7 and 14 days, CGRP IR remained prominent and was associated with disorganized axonlike profiles, sometimes directed in a circumferential pattern around the outside of the neuroma. RIA confirmed rises in CGRP content at 24 and 48 h that accompanied the changes in local blood flow and altered distribution of CGRP IR. CGRP accumulates in a time-related fashion within experimental neuromas, where it induces among other possible actions prominent local vasodilatation. CGRP may be important in the regenerative milieu of injured nerves.

Accumulation and degranulation of mast cells in experimental neuromas

Mast cell accumulation and degranulation occur within the endoneurium of injured peripheral nerves. We investigated the time course of mast cell accumulation and degranulation in experimental neuromas of the sciatic nerve in rats. Mast cell accumulation and degranulation were significant only after the first week following neuroma creation and were prominent at 14 days within the neuroma stump. Mast cell degranulation could account for microvascular changes within neuromas after the first week following injury.

[Selective epidural phlebography in the diagnosis of tumors of the cervical spinal cord and of the cauda equina roots]

The method of selective epidural phlebography (SEP) was applied in the diagnosis of tumors of the cervical segment of the spinal cord and the roots of cauda equina in 45 patients. The diagnosis was confirmed in 32 of the 37 patients who were operated on. The SEP method does not produce serious complications and allows circulatory disorders in the vertebral venous plexuses to be revealed. The diagnostic value of the method is higher in tumors of superocervical localization and hourglass tumors.

Benign schwannomas: a histopathological and morphometric study

A conventional histopathological and quantitative morphometric study of 28 capsulated peripheral and spinal nerve benign schwannomas demonstrated linear and parabolic correlation between Antoni B tissue, vascularity and tumour size. The results support the endoneural connective tissue origin of Antoni B, and suggest a model of tumor growth that is partially limited by the growth potential of the Antoni B and/or the vascular component.

[Comments on the problem of differential diagnosis of tumours of the nerve sheaths in angiography (author's transl)]

The article describes the special features governing the assessment of angiographic findings in tumours of the nerve sheaths. Considerations of differential diagnosis, especially between neurinoma and neurofibroma, are discussed. Likewise, the problems of differential diagnosis of such tumours against neoplasms of the tissue of the soft parts, are also discussed. Angiography permits only a limited determination of the degree of malignancy of the neurinoma and neurofibroma. It is always mandatory to correlate these findings with the histological findings. However, angiography does seem to be justified as an additional examination technique, since it supplies fundamental pointers for surgery.

Gross vascularization of experimentally induced transplanted tumors of the central and peripheral nervous system

Subcutaneously and intracerebrally transplanted neurinomas as well as intracerebrally grafted gliomas, both derived from primary tumors with resorptive carcinogens were investigated after injection of micropaque by conventional histologic methods and by postmortem X-ray analysis. Growth pattern and vasculature were similar in subcutaneously and intracerebrally transplanted malignant neurinomas. The most common feature was a parallel arrangement of vessels as shown by microradiography and vessel free zones. In intracerebrally grafted glioma, the growth of tumors was confined to or starting from the ventricular system. Sinusoidal vessels, capillary proliferations and proliferation of vessel wall were found. The outstanding feature was the occurrence of extravascular contrast deposits, thus indicating the vulnerability of tumor vessels and frequency of hemorrhages into these tumors.

[Neuroradiologic diagnosis of trigeminal neurinoma originating from the gasserian ganglion (author's transl)]

Three cases of trigeminal neurinoma originating from the Gasserian ganglion were reported. The findings observed on plain roentgenograms, cerebral angiograms and pneumoencephalograms were described in detail. Neuroradiologic examinations used routinely our department for the diagnosis of the skull base tumors were as follows; (1) plain skull examinations, including lateral, straight posterior-anterior, anterior-posterior half axial (Towne), axial, Stenvers, optic canal as well as tomograms in frontal, sagittal and axial projections; (2) angiographies by transfemoral catheter technique including selective internal carotid, external carotid and vertebral angiograms, and orbital-cavernous sinus venography via frontal and femoral veins; (3) pneumoencephalography with tomography. Bone destruction of the middle fossa including foramen ovale, foraman spinosum and lateral aspect of the sella was seen in all cases. Superior orbital fissure, optic canal and anterior surface of the petrous bone were also eroded depending upon the extent of tumors. Sharply circumscribed erosion of the petrous apex was seen in one of 3 cases, indicating the tumor extention into the posterior fossa. A soft tissue mass in the sphenoid sinus and ethmoidal air cells was recognized in all cases. Selective internal and external carotid angiograms demonstrated tumor vessels in 2 of 3 cases. Orbital-cavernous sinus venography was helpful for the interpretation of the lesion extending to the cavernous sinus and its neighboring structures. Conventional gas encephalography showed elevation of the temporal horn, and the concave arch formed by the supracornual cleft and lateral cleft was directed basally and medially in all of the cases. Tomography was also useful in the more detailed analysis of temporal horn. It should be stressed that the plain skull features are most important for deciding which contrast examination should be performed further.