Application Of Gene Chip In Detection Of Hereditary Breast Cancer-ovarian Cancer Syndrome

The interaction of external environment and genetic factors leads to the accumulation of deleterious gene mutations,leading to uncontrolled cell growth,cell division and resistance to apoptosis,which is the root cause of cancer.Gene embryonic pathogenic variations can be detected in almost 5-10% of patients in their genomes,resulting in a great increase of cancer risk in a lifetime,which is known as hereditary cancer.However,the accumulation of mutations is a long-term process,early detection of carriers of deleterious mutations in cancer susceptibility genes,timely medical intervention,will be effective in reducing the cancer risk of cancer susceptibility populations.Hereditary Breast-Ovarian Cancer Syndrome(HBOC)is the most common Hereditary Cancer syndrome,which involves more than 20 susceptibility genes.About 50%-70% of HBOC results from the genetic mutations of BRCA1 and BRCA2 genes in germ cell.In order to investigate the frequency and characteristics of the carriers of the deleterious variation of these genes in the population of Hunan province,and to provide data reference for screening risk population,the project collected samples from 986 breast/ovarian cancer patients and healthy women who volunteered for a free HBOC-related gene panel test study at a cancer genetic counseling clinic in 2019.A total of 496 patients,including 268 patients with breast cancer,226 patients with ovarian cancer,2 patients with breast cancer and ovarian cancer.The subjects were divided into four groups according to whether they had a family history of breast/ovarian cancer and a high risk of HBOC: patients with family history,patients with no family history,non-patients with family history,non-patients with no family history.Family history is defined as having a high risk of breast cancer,Ovarian Cancer(including Fallopian Tube and primary peritoneal cancer),prostate cancer,melanoma,male breast cancer and pancreatic cancer.A BRCA1/2 gene panel developed by ourselves was used to detect the genes of the above population,the detected mutations were classified into 5 types: pathogenic,likely pathogenic,variants of uncertain significance,likely benign and benign in accordance with the American College of Medical Genetics and Genomics and the Association for Molecular Pathology(ACMG)classification criteria and guidelines.In this study,the pathogenic and likely pathogenic variants were classified as positive variants,while the likely benign and benign variants were classified as negative variants.Our main results are as follows:1、Based on second-generation sequencing technology,targeted all exons of BRCA1/2 gene(NM＿007294.3、NM＿000053.3)and 10 bp sequences of its flanks,and developed a BRCA1/2 gene mutation detection method(patent release number: CN109694904A)to provide technical and data support.2、19 new mutations in BRCA1 that have not been documented were identified in the local population,among which 7 mutations in BRCA1 were identified as pathogenic or suspected pathogenic: c.3599＿3600del,c.3449 del,c.220 del,c.2293 G>T,c.956＿957ins TGGGCTCCAA,c.4017 del and c.4485-1 G>T.For BRCA2 gene,27 mutations were identified,among which 4 were identified as pathogenic and likely pathogenic variants: c.3628＿3629del,c.4982 dup A,c.4983 G>T and c.9257-2A>G.In addition,the BRCA2 gene c.943T>A,a mutation was re-evaluated with local data accumulation and network database updating,and was reduced from undefined mutation to likely benign mutation.In the practical application of ACMG scoring rules,PM2 and PP4 scoring rules were refined for BRCA1/2 gene by adding frequency evidence of gene population and family history.3、The positive rates of BRCA1/2 gene mutation in were patients with family history were 34(30.08%);in patients with no family history were32(9.30%);in non-patients with family history were 8(5.19%)and in non-patients with no family history were 3(0.83%).It should be noted that the detection rate of HBOC was 0.83% in non-patients with no family history of HBOC,and 5.19% in non-patients with family history,it is suggested that breast cancer/ovarian cancer susceptibility gene screening should be carried out according to the local population data.4、For 61 patients who met the American Society of Clinical Oncology(ASCO)HBOC diagnostic criteria and were negative for BRCA1/2 gene panel,the range of gene detection was further expanded,other HBOC related gene variants including BRIP1,PALB2,CHEK2 and RAD51 C were detected in 7 families.