Genetic Detection And Analysis Of The VHL Gene In Chinese Patients Of Sporadic Pheochromocytoma

Background and PurposePheochromocytomas are neuroendocrine tumours arising from chromaffin cells of the adrenal medulla or extra-adrenal medulla paraganglia. It is a major cause of secondary hypertension. According to genetic characteristics, pheo- chromocytoma can be divided into genetic and sporadic. Genetic pheochromo- cytoma are usually related with some pheochromocytoma-susceptibility genes,such as VHL gene, NF1 gene,et al.The pathogenesis of pheochromocytoma remains unclear. Abroad medical institutions recommend genetic testing for patients with an apparently sporadic pheochromocytoma. It was suggested by a report that placed the estimate of hereditary disease in apparently sporadic pheochromocytoma as high as 24%.Most of mutations in VHL gene are identified in earlier research of mutations screening.Therefore, VHL gene is usually taken as a preferred screening gene of pheochr- omocytoma. There are no domestic relevant research carried out,which are about VHL gene screening in sporadic pheochromocytoma.VHL gene is a tumor suppressor gene,encoding protein VHL that regu- lates hypoxia-inducible genes, the fibronectin matrix assembly, and angiogenesis. Theβ-subunit of pVHL binds to a region of HIF-αthat regulates the expression of VEGF. Under the conditions of hypoxic and dysfunctional of pVHL mutations,the expression of HIF-αand VEGF may arise,which may promote tumor incidence and growth. VHL gene mutations is related to the pathogenesis of VHLD. According to genotype and phenotype,VHLD can be divided into two types: Type I (not with pheochromocytoma) and TypeⅡ(with pheochromocytoma). It is begin to detect HIF-αand VEGF for tumor diagnosis and investigate HIF-αfor cancer treatment in aboard. There are no found relevant reports about the expression of HIF-αand VEGF in VHLD with pheochromocytoma.And it is a litter of domestic reports about the expression of HIF-αand VEGF in renal cell carcinoma.In the present study we evaluate the clinical features of pheochromocytoma.We investigate the genetic detection of VHL and the expression of HIF-1α,HIF-2αand VEGF in sporadic pheochromocytoma.We also inve- stigat the expression of HIF-1α,HIF-2αand VEGF in renal cell carci- noma. The purpose of the present study is to explore the association between VHL gene mutations and the pathopoiesis of pheochromocytoma and the relevance of HIF-αand VEGF in the tumors of the urinary system.Methods and Results(1)The summary and analysis of clinical feature in pheochromo- cytoma. By the clinical observations and long-term follow-up visit ,we found there were still some differences between sporadic and familial pheochromocytoma in terms of age of onset,clinical symptom, biochemi- cal diagnosis and genetics.(2)The research of the genetic detection of VHL gene and the expre- ssion of HIF-1α,HIF-2αand VEGF in sporadic pheochromocytoma. By general polymerase chain reaction and touchdown polymerase chain reac- tion and direct sequencing and immunohistochemistry,we investigated the genetic detection of VHL gene and the expression of HIF-1α,HIF-2αand VEGF in sporadic pheochromocytoma. Our data showed that there were three mutations in exon 2 and the proportion of mutations is 7%.One of mutations was located at nucleotide 572 (G→C) in exon 2,presenting a codon 120 from arginine (R) to threonine (T).Tow small insertions were locatated at nucleotide 623 (^TTTGTtG) in exon 2,leading to frameshift mutation. Other patients and 50 normal controls were not found the mutations.The novel mutations were identified. We found that the expression arose in HIF-1α,HIF-2αand VEGF in carriers of VHL gene mutations.HIF-1αarose in 11 cases and HIF-2αarose in 12 cases,in which the expression between HIF-1α,HIF-2αand VEGF is positively correlated.(3)The research of the expression of HIF-1α,HIF-2αand VEGF in renal cell carcinoma. By immunohistochemistry,we investigated the expression of HIF-1α,HIF-2αand VEGF in renal cell carcinoma. Our data showed that HIF-1αarose in 28 cases and HIF-2αarose in 25 cases,in which the expression between HIF-1α,HIF-2αand VEGF is positively correlated.ConclusionBased on these experimental findings, we conclude that (1) we firstly revealed that there were three mutations in exon 2 of VHL gene encodingβ-domain of pVHL;(2) under the conditions of pVHL mutations located atβ-domain and hy- poxic,the expression between HIF-1α,HIF-2αand VEGF is positively correlated in patients of pheoehromoeytoma,which could induce over-expression of VEGF and promote tumor angiogenesis and invasiveness;(3) The result of renal cell carcinoma may be in a similar situation of pheochromocytoma. Together, these findings provi- de experimental evidences for further understanding of pathogenesis of pheochromocytoma,genetic diagnosis of urinary tumors and cytokine targeted therapy.