Identifying And Functional Validation Causative Variants From Breast Cancer And Blue Rubber Bleb Nevus Syndrome

Breast cancer is prevalent among female worldwide.Multiple breast cancer predisposition genes have been identified via linkage analysis or candidate gene screening.However,the predisposition genes of more than 50%breast cancer patients are still undetermined.In this study,we applied whole exome sequencing to all patients of one Chinese breast cancer pedigree;meanwhile,we reanalyzed whole exome sequencing data about 13 non-BRCA1/2 breast cancer pedigrees and 78 sporadic Korean breast cancer patients.In our analysis,we identified certain known pathogenic variants from both familial and sporadic breast cancer patients.Secondly,we identified novel predisposition ones,which impaired gene MRE11A,RECQL and NCKl.Finally,we deciphered four mutational signatures,including APOBEC-related and mismatch repair deficiency-related signatures,from the sporadic breast cancer cohort.To confirm the roles of the novel predisposition genes,we focused on gene NCK1.In vitro,NCK1(p.D73H)could promote viability and invasion of breast cancer cell line MCF7.Expression of NCK1 was correlated with risk of breast cancer metastasis and relapse.Our results confirm that breast cancer is highly heterogeneous,more predisposition genes will be identified with sample size increasing.Blue rubber bleb nevus syndrome(BRBNS),which is a rare venous malformation associated disorder and mostly affects skin and gastrointestinal tract in early childhood.Both familial and sporadic VM can be explained by mutations in TEK/TIE2.Recently,some somatic mutations in TEK have also been identified from cases of BRBNS.In addition,somatic mutations in PIK3CA have also been determined to be disease-causing in sporadic VM.Therefore,the underlying genetic factors contributing to pathogenesis of VM and associated sysdrome could have high heterogeneity.Through whole-exome sequencing,we identified one somatic mutation in the TEK gene(p.L914F)from one case of sporadic VM and two rare germline GLMN variants,GLMN(p.P254R)and GLMN(p.E544X),from two separate cases of BRBNS.HUVECs transfected with GLMN mutants exhibited increased mTOR signaling compared with that of cells expressing the wild-type protein.In addition,in some cases of TEK-mutation-negative and GLMN-mutation-negative BRBNS,symptoms were relieved after rapamycin treatment.Therefore,abnormal mTOR signaling might be a major cause of BRBNS.