Genotype,Epigenetic Patterns And Clinical Differential Characteristics Associations In Head And Neck Paragangliomas

Objective: To investigate and study the correlation between clinical differentiation and genotype and epigenetic type in patients with head and neck paraganglioma.Hypermethylation and clinical significance of promoters in jugular paragangliomas.Method: The retrospective study examined a series of 37 patients(17 male and 20 female,respectively)with head and neck paraganglioma who underwent surgical resection between 2010 and 2015 in affiliated xinhua hospital of Shanghai jiaotong university.Meanwhile,the tumor tissue and peripheral blood of 37 patients were collected and DNA was extracted.The mutations in the succinate dehydrogenase A,B,C,D(SDHA,SDHB,SDHC,SDHD),succinate dehydrogenase complex assembly factor 2(SDHAF2)genes were detected using direct DNA sequencing.Aberrant hypermethylation of the Cp G islands of a panel of ten TSGs(p16,HIC1,Dc R1,Dc R2,DR4,DR5,CASP8,HSP47,MGMT and RASSF1A)was also analyzed using methylation-specific PCR.The expression level of gene(HIC1,Dc R2 and DR5)was detected by Real Time PCR.The clinical data of patients during hospitalization were statistically analyzed with the results of gene sequencing and methylation.Methylation-specific PCR(MSP)was used to analyze the methylation of the 4 promoters in 12 jugular paraganglioma specimens.Result: Direct sequencing demonstrated the presence of germline SDH mutations in ten HNPGLs.Comparisons of clinical features between mutated and non-mutated HNPGLs established an association of SDH mutations with progressive phenotypes,including an earlier formation,multiple lesions,or malignancy.There was also a significant correlation between the presence of SDH mutations and the number of TSGs methylated in HNPGLs.The SDH-related tumors were therefore more likely to suffer from a Cp G island methylator phenotype.Four differentially methylated TSGs in mutated tumors vs non-mutated counterparts were identified with inefficient expression through Real-Time PCR analysis.All the four genes showed methylation of promoters in jugular paraganglioma with respective methylation rates of 36.4%,41.7%,75.0% and 33.3%.Nomethylation promoters could be detected in the normal nerves.Patients with high methylation index(MI>0.05)were younger at diagnosis than those with low methylation index(MI?0.05,P=0.0189)Conclusion: Epigenetic inactivation on multiple TSGs may serve as a key mechanism for the progressive behaviors of SDH-mutated HNPGLs.Thus,an interplay between genetic status,epigenetic alterations,and clinical features might be established in the disease.Methylation of DcR1,DcR2,DR4 and D R5 promoters exists in jugular paragangliomas and maybe associated with the genesis and development of this tumor.Due to its reversibility,methylationis a potential target in further targeted therapy of tumor.