Molecular Epidemiological Research On DICER1 Gene In Patients With Pleuropulmonary Blastoma

Objective: In order to improve genetic counseling and disease management of DICER1 syndrome,systematic review was conducted to investigate the multimorbidity and genetic characteristics of DICER1 syndrome.At the same time,DICER1 mutation frequency,distribution of pathological type and multimorbidity status of Chinese patients with PPB were described,which will provide the foundation for developing screening programs.Methods: We systematically searched bibliographic databases,including PubMed,Embase,Wanfang and CNKI for articles which are related to diseases covered by DICER1 syndrome.The weighted summary of mutation frequencies among patients with pleuropulmonary blastoma(PPB),cystic nephroma,and Sertoli-Leydig cell tumor were calculated.Furthermore,medical history and family history of 12 Chinese children with PPB were collected consecutively.Blood samples from children with PPB and their first degree relative were tested for DICER1 mutations by Next-Gen sequencing.The sequencing results were annotated by the annovar,VEP and snp EFF software.According to the reliability of the data,the location of the mutation,the impact of variation on the function of the protein,the mutation results were screened.All participants’ parents signed a consent form to genetic testing and medical historycollection.Information of PPB in Beijing Children’s Hospital from 2006 to 2016 were extracted retrospectively,including date of diagnosis,first diagnosis,admission diagnosis,primary diagnosis in discharge,pathological type,medical history and so on.Result:(1)Forty-nine eligible articles were included in the systematic review.In total,72 cases with multimorbidity of DICER1 syndrome were identified.More females(n=46,64%)presented with multimorbidity than males(n=18,25%)and the remaining 8 patients’ gender were unknown.Thirty-one of 72 cases(>40%)were identified to have 3 or more coexisting diseases.Nineteen of 72 patients with multimorbidity suffered from another disease that was not yet included in DICER1 syndrome,which would provide potential phenotypes of DICER1 syndrome.The pooled germline DICER1 mutation frequencies in PPB,cystic nephroma,and Sertoli-Leydig cell tumo were 66.9%,73.2%,and 57.1%,respectively.The pooled somatic DICER1 mutation frequencies of PPB,cystic nephroma,and Sertoli-Leydig cell tumor were 92.4%,87.9%,and 43.3%,respectively.(2)Twelve patients with PPB(6 patients suffering from type Ⅱ PPB and 6 patients suffering from type Ⅲ PPB,respectively)were evaluated for germline DICER1 mutations.Seven patients were identified deleterious DICER1 mutation,among which 6 mutations lead to premature protein truncation as a result of frameshift mutation or nonsense mutations.Another one case carried a germline DICER1 mutation which was suspected to deleteriously affect splice site.The whole genome sequencing results show that the twins are monozygotic twins.Somatic mutation analysis identified a total of 135,109 somatic mutations,consisting of a nonsynonymous variant of DICER1(c.G5125A)fell within RNase III domain and a nonsense mutation located within TDG.Moreover,some well-characterized cancer driver genes,such as EGFR,ALK and FOXA1,were also mutated in the PPB FFPEsample.Two DICER1 mutation positive cases were found to have lung cysts preceding the diagnosis of PPB.Furthermore,one child was found a remarkable family history of thyroid diseases.(3)A total of 27 patients(15 males,12 females)with PPB were treated in Beijing children’s hospital from 2006 to 2016.Only 2 cases were diagnosed as type Ⅰ PPB,5 cases were type Ⅱ and 6 cases were type Ⅲ.Only one patient were diagnosed as PPB for the first time,most of patients were diagnosed as unknown tumor(N = 9,33.3%)or pulmonary cystic lesions(N = 5,18.5%)for the first time.One patient with DICER1 mutation suffered from bilateral PPB;two patients had lung cysts;two patients suffered from bullae of lung;one patient had an adrenal tumor.Conclusion: Majority of patients with multimorbidity of DICER1 syndrome were mutation positive individuals so that multimorbidity may suggest the possible germline mutation of these patients and their relatives.It is therefore necessary to provide molecular genetic testing,genetic counseling and disease management for patients with multimorbidity.Germline mutation frequency of Chinese patients with PPB is similar with published studies.However,the major pathological types in Chinese patients were type Ⅱ and Ⅲ,which suggested that children with PPB in China were faced with the high misdiagnosis rate.The results suggest that we can tentatively integrate the DICER1 mutations test in clinical process,in order to assist diagnosis and disease managementbecause patients with pathogenic DICER1 mutations are prone to bilateral disease and other diseases included in the DICER1 syndrome.