Case 1 -

VHL-Associated Clear Cell Renal Cell Carcinoma as an Example for Familial Renal Cell Carcinoma John N Eble, M.D. Holger Moch, M.D.

Case history: 37 year old man with detection of left renal tumor by computerized tomography (CT). In addition, multiple smaller renal tumors in the same and contralateral kidney were observed. Some tumors were cystic. In addition, imaging revealed a few cysts. The largest tumor was removed by organ-sparing surgery. Macroscopic findings: The tumor measured 5 x 5 x 1.5 cm. The cut-surface of the tumor was yellow. Diagnosis: VHL-associated clear cell renal cell carcinoma as an example for familial renal cell carcinoma A surprising number of hereditary syndromes predispose to the development of renal cell carcinoma. Within the last few years 7 renal cancer syndromes have been characterized. Five of the predisposing genes have meanwhile been identified: VHL, MET, FH, BHD, and HRPT2 (Table 1). VHL disease is the most frequent familial renal cancer syndrome and is associated with clear cell renal carcinoma and multi-organ neoplasia, associated with mutations in the VHL gene and loss of the wild-type VHL-allele. Patients with hereditary papillary renal carcinoma syndrome (HPRC) have a germline activating mutation in the MET-proto-oncogene which can cause renal cancers with papillary type 1 histology. Papillary type 2 renal carcinomas and uterine smooth-muscle tumors are associated with the hereditary leiomyomatosis and renal cell cancer syndrome (HLRCC), which is caused by germline loss-of-function mutations in the Fumarate-Hydratase (FH) gene. The hyperparathyreoidism-jaw tumor (HPT-JT) syndrome is associated with parathyroid adenomas, fibro-myalgious tumors of the jaw and renal tumors. This syndrome is caused by germline mutations in HRPT2. The Birt-Hogg-Dubé syndrome (BHD) is associated with an increased risk for renal cancers of various histological types, such as chromophobe RCC and oncocytic hybrid tumors. Von Hippel-Lindau (VHL) disease is inherited through an autosomal dominant trait and characterized by the development of capillary hemangioblastomas of the central nervous system and retina, clear cell renal carcinoma, pheochromocytoma, pancreatic and inner ear tumors The syndrome is caused by germ line mutations of the VHL tumor suppressor gene, located on chromosome 3p25-26. The VHL-protein is involved in cell cycle regulation and angiogenesis (figure1). Inactivation of the VHL gene affects VHL protein function. The VHL protein negatively regulates hypoxia-inducible factor, which activates genes involved in cell proliferation, neo-vascularization, and extracellular matrix formation. The hypoxic response, as a result of dysregulation of HIF subunits, results in transcriptional activation of hypoxia-inducible genes. These genes encode growth and angiogenic factors such as vascular-endothelial growth factor, erythropoietin and platelet-derived growth factor-β that enhance neovascularization of these proliferating renal tumors. Transforming growth factor-a (TGF- a), another HIF target gene, might function in the development of renal tumors, as TGF-a and its receptor, epidermal growth factor receptor, are commonly over expressed in renal carcinoma. The von Hippel-Lindau syndrome is estimated to occur at rates of 1:36,000 to 1:45,500 population. The typical renal manifestations of VHL are kidney cysts and clear cell carcinomas. Multiple kidney tumors of other histological types rule out the diagnosis of VHL syndrome. Histological examination of renal tissue from VHL patients may reveal several hundred independent tumors and cysts. The mean age of manifestation is 37 years versus 61 years for sporadic clear cell renal carcinomas, with an onset age of 16 to 67 years. Metastatic RCC is the leading cause of death from VHL. The median life expectancy of VHL-patients is 49 years. In order to detect VHL-associated tumors in time, analysis of germ line mutations of the VHL gene have been recommended in every patient with retinal or CNS hemangioblastoma, particularly those of younger age and with multiple lesions. Germ line mutations of the VHL-gene are spread all over the 3 exons. Missense-mutations are most common, but nonsense-mutations microdeletions/insertions, splice mutations and large deletions also occur. The spectrum of clinical manifestations of VHL reflects the type of germ line mutations. Phenotypes are based on the absence (type 1) or presence (type 2) of pheochromocytoma. VHL type 2 is usually associated with missense-mutations and subdivided on the presence (type 2a) or absence (2b) of renal cell carcinoma. In contrast to loss of functions variance in VHL type 1, mutations predisposing to pheochromocytoma (VHL type 1) are mainly of the missense type predicted to give rise to conformational change of pVHL. In addition, VHL type 2c has been used for patients with only pheochromocytoma; however several years later some of these cases developed other VHL manifestations. Figure 1: Dysregulation of HIF-1a by VHL inactivation leads to clear cell renal tumors in patients with von Hippel-Lindau disease Under normoxic conditions, hypoxia-inducible factor-1α (HIF-1α) is hydroxylated (-OH) on two conserved proline residues (for simplicity, only one is shown) by a family of prolyl hydroxylases at its oxygen-dependent degradation domain. This hydroxylation provides a substrate-recognition site for the von Hippel-Lindau (VHL) E3 ubiquitin ligase complex, which contains elongins C and B, cullin-2 (CUL2) and RBX1. Polyubiquitylation of HIF-1α by the VHL complex leads to its proteasomal degradation by the 26S proteasome. HIF-1α is also hydroxylated at an asparagine residue in its carboxy-terminal transactivation domain by FIH-1, an asparaginyl hydroxylase. This blocks binding of the transcriptional coactivators CREB-binding protein (CBP) and p300 to HIF-1α, thereby inhibiting transcription of HIF-target genes. Hypoxic conditions block both types of hydroxylation, allowing HIF-1α subunits to accumulate and activate transcription of hypoxia-responsive genes. VHL inactivation - as occurs in renal cells from patients with a germline VHL mutation and loss of the wild-type allele - mimics the hypoxic response by preventing degradation of HIF-1α subunits. Loss of VHL function causes accumulation of HIF-1α subunits in the cytoplasm and their translocation to the nucleus. HIF-1 a dimerizes with HIF-1 b and is coactivated by CBP/p300. HIF-1 a/b binds to hypoxia response elements (HRE) in gene promoters, thereby activating transcription of genes upregulated in clear-cell renal tumors, including vascular endothelial growth factors, erythropoietin and platelet-derived growth factor- b. (HIF-1α is shown, but HIF-2a is also recognized as a VHL substrate.). from: Nature 4, 2004, 381-393 Table 1: Hereditary causes of renal cell carcinoma and angiomyolipomas Syndrome Gene Protein Chromosome Kidney Skin Other Tissue von Hippel-Lindau VHL pVHL 3p25 Multiple, bilateral clear-cell renal cell carcinoma (CCRCC), renal cysts - Retinal and CNS haemangioblastomas, phaechromocytoma, pancreatic cysts Hereditary papillary renal cancer c-MET HGF-R 7q31 Multiple, bilateral papillary renal cell carcinomas (PRCC), Type 1 - Hereditary leiomyomatosis and RCC FH FH 1q42-43 Papillary renal cell carcinoma (PRCC), non-Type 1 Nodules (leiomyomas) Uterine leiomyomas and leiomyosarcomas Birt-Hogg-Dubé BHD Folliculin 17p11.2 Multiple chromophobe RCC, conventional RCC, hybrid oncocytoma, papillary RCC, oncocytic tumors Facial fibrofolliculomas Lung cysts, spontaneous pneumothorax Constitutional chromosome 3 translocation unknown Multiple, bilateral clear-cell renal cell carcinomas (CCRCC) - - Hyperparathyreoidism-jaw tumor (HP-JT) HRTP2 1q25-32 Mixed epithelial and stromal tumors, papillary RCC: cysts - Parathyroid tumors, fibro-osseous mandibular and maxillary tumors Familial papillary thyroid cancer (FPTC) Unknown gene 1q21 Papillary RCC, oncocytoma - Papillary thyroid cancer, nodular thyroid disease Tuberous sclerosis TSC1 Hamartin TSC2 Tuberin 9q34 16p13 Multiple, bilateral angio-myolipomas, lymph-angioleiomyomatosis Cutaneous angiofibroma ('adenoma sebaceum') peau chagrin, subungual fibromas Cardiac rhabdomyomas, adenomatous polyps of the duodenum and the small intestine, lung and kidney cysts, cortical tubers and subependymal giant cell astrocytomas (SEGA) References: Pavlovich CP and Schmidt LS, Searching for the hereditary causes of renal-cell carcinoma. 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