Von Hippel-Lindau disease and endocrine tumour susceptibility.

Von Hippel-Lindau (VHL) disease is a dominantly inherited familial cancer syndrome caused by mutations in the VHL tumour suppressor gene. VHL disease is characterised by marked phenotypic variability and the most common tumours are haemangioblastomas of the retina and central nervous system and clear cell renal cell carcinoma. However, endocrine tumours, most commonly phaeochromocytoma and non-secretory pancreatic islet cell cancers, demonstrate marked interfamilial variations in frequency and are significant causes of morbidity and, sometimes, mortality. Genotype-phenotype correlations have revealed that certain missense mutations are associated with a high risk of phaeochromocytoma but total loss of function mutations are associated with a low risk. Furthermore, rare mutations may predispose to a phaeochromocytoma-only phenotype. Germline VHL mutations may be detected in 5-11% of all phaeochromocytoma cases and mutation analysis of VHL and other phaeochromocytoma susceptibility genes (SDHB, SDHD and RET) should be performed in all cases of familial, multiple or early onset phaeochromocytomas, and considered in other cases. The VHL gene product has a key role in regulating the stability of hypoxia-inducible factors (HIF-1 and HIF-2) such that inactivation of VHL leads to up-regulation of HIF-1 and HIF-2 protein expression and activation of hypoxic gene response pathways. Germline SDHB and SDHD mutations also lead to increased expression of HIF target genes, but it appears that phaeochromocytoma susceptibility in VHL disease cannot be attributed to HIF activation alone. Recently, it has been suggested that an HIF-independent failure of developmental apoptosis is a common feature of all inherited phaeochromocytoma susceptibility syndromes.