Loss of Heterozygosity Reveals Non-VHL Allelic Loss in Hemangioblastomas at 22q13 MARIE E. BECKNER, MD, EIZABURO SASATOMI, MD, PHD, PATRICIA A. SWALSKY, BS, RONALD L. HAMILTON, MD, IAN F. POLLACK, MD, AND SYDNEY D. FINKELSTEIN, MD Hemangioblastomas (HBs) are low-grade (World Health Orga- nization grade I/IV) central nervous system (CNS) tumors that fre- quently contain VHL (3p26) mutations. They occur sporadically and in von Hippel Lindau (VHL) disease. Encoded pVHL aids degrada- tion of hypoxia-inducible factors (HIFs) in the presence of normal oxygen levels. HBs provide an in vivo view of HIF effects within a CNS tumor. Typically, HBs are cystic tumors containing a mural nodule formed by noninvasive, vacuolated stromal cells that are embedded in a network of capillaries. Nine HBs, consecutively re- sected from 8 patients at our institution during a recent 2-year time span, were evaluated for additional losses of tumor suppressor genes. Non-VHL microsatellites studied for loss of heterozygosity (LOH) are near tumor suppressor genes lost in gliomas, pituitary adenomas, several CNS tumors on 22q, neurofibromatosis 1, and colon carcino- mas (13, 2, 2, 1, and 2 markers for each, respectively). LOH in the region of 3p21.3-3p26.3 occurred in 3 of 8 HBs informative for at least 1 marker (D3S1539, D3S2303, or D3S2373). By using 2 markers (D22S417 and D22S532) for 22q13.2, LOH was found in 5 of 8 informative HBs. All 3 HBs with allelic losses near VHL also showed LOH at 22q13.2. No consistent losses were found with markers for 1p34, LMYC, 5q21, 5q32, 9p21, 10q23, 17p13, and 19q13. LOH for the 22q13.2 region in HBs suggests that the loss of another tumor suppressor gene is involved in the pathogenesis of HBs in addition to VHL. Absence of LOH for glioma markers is consistent with the low-grade behavior of HBs. HUM PATHOL 35:1105-1111. © 2004 Elsevier Inc. All rights reserved. Key words: hemangioblastoma, von Hippel Lindau, tumor sup- pressor genes, loss of heterozygosity. Abbreviations: HBs, hemangioblastomas; VHL, von Hippel Lindau; HIFs, hypoxia-inducible factors; LOH, loss of heterozygos- ity; VEGF, vascular endothelial growth factor; APC, adenomatous pol- yposis coli; NF1, neurofibromatosis type 1, NF2, neurofibromatosis type 2; CNS, central nervous system; PCR, polymerase chain reaction. Hemangioblastomas (HBs) are slow-growing cen- tral nervous system tumors (World Health Organiza- tion grade I/IV) that occur either sporadically or as part of the von Hippel Lindau (VHL) syndrome. HBs are most frequently found in the cerebellum. However, patients with VHL disease can have multiple HBs that sometimes involve the retina, brainstem, spinal cord, and cerebral cortex. HBs occur as well-circumscribed nodules that are often found in the wall of an intracra- nial (usually posterior fossa) cyst or are associated with a syrinx in the spinal cord. The microscopic appear- ance of HBs is characterized by a proliferation of cap- illaries, forming a rich vascular network supporting neoplastic, vacuolated stromal cells. Although the nat- ural history of HBs includes both growth and quiescent phases, the mitotic rates of HBs are usually low, and these tumors characteristically do not behave aggressively. 1 Mutational loss of the tumor suppressor gene, VHL, chromosome 3p26.11, often occurs in HBs. A second allele is lost either after germline mutations in patients with VHL disease or after somatic mutations in sporadic HBs. 2-7 Also, somatic mosaicism may occur in VHL disease. 8 Mutations of the VHL gene are fre- quently indicated by loss of heterozygosity (LOH) for nearby microsatellites. 7,9-11 The encoded protein, pVHL, regulates several transcriptional cellular responses to hypoxia. Nor- mally, ubiquitination of the  subunit of the hypoxia- inducible factor (HIF) transcription factor is medi- ated by pVHL and leads to HIF degradation in the presence of oxygen. 12 Accordingly, the loss of pVHL promotes increased production of proteins encoded by the genes transcriptionally regulated by HIF, in- cluding vascular endothelial growth factor (VEGF) and erythropoietin. 13-18 Although the loss of VHL leading to increased VEGF expression explains the proliferation of non- neoplastic blood vessels in HBs and increased perme- ability allowing fluid accumulation, 19-22 stromal cell proliferation and histogenesis remain controversial. The loss of VHL alone with activation of HIF has not promoted tumorigenesis in an animal model. 23 Muta- tions of the VHL gene also occur in retinal angiomas, renal carcinomas, pheochromocytomas, islet cell tu- mors, and endolymphatic sac tumors of the inner ear, 9,24-28 suggesting that the potential for tumorigenic- ity in neuroectodermal and neuroendocrine cells is sensitive to the loss of VHL, possibly promoted by the loss of 1 or more other tumor suppressor genes. A neuroectodermal origin has been proposed for HBs, 29,30 as well as a vascular origin. 18,31,32 Although stromal cells in HBs are antigenically polymorphous, several studies have shown positive immunohistochem- From the Department of Pathology and Department of Neuro- surgery, University of Pittsburgh School of Medicine, Pittsburgh, PA, and RedPath Integrated Pathology, Pittsburgh, PA. Accepted for publication May 13, 2004. Supported by The Nick Eric Wichman Foundation, Ellicott City, MD. Address correspondence and reprint requests to Marie E. Beck- ner, MD, 200 Lothrop Street, PUH, Rm. A-515, Department of Pa- thology, University of Pittsburgh School of Medicine, Pittsburgh, PA 15213. 0046-8177/$—see front matter © 2004 Elsevier Inc. All rights reserved. doi:10.1016/j.humpath.2004.05.014 1105