Comprehensive Multigene Mutation Spectra Of Breast Cancer In Northeast China And MicroRna-206 Inhibits The Biological Behavior Of TNBC By Targeting TM4SF1

Breast cancer is a malignant tumor that occurs in the epithelial tissue of the breast gland.It seriously affects the health of females on account of its high incidence and heterogeneity.Triple-negative breast cancer(TNBC)is a special subtype of breast cancer.It is not sensitive to endocrine therapy and targeted therapy in addition to traditional radiotherapy and chemotherapy.Therefore,personalized and precise treatments must be developed based on the heterogeneity of breast cancer.Moreover,undersanding the mechanism of the tumor invasion and metastasis,and exploring effective therapeutic agents for TNBC have profound significance.This topic consists of two parts.The objectives of the the first part were to obtain the multigene mutation spectra of female breast cancer patients in Northeast China,to explore the correlation between mutations and clinicopathological characteristics,and to identify genetic mutations that correlate with the prognosis and survival of breast cancer patients.The results showed that a total of 286 patients were enrolled in this study.Eleven harmful/pathogenic gene mutations were found in54.2%(155/286)of the patients,and 179 somatic nonsynonymous mutations were detected.Approximately 5.6%(16/286)of the patients carried two or more gene mutations.Among the 11 pathogenic gene mutations,those in PIK3 CA were the most common and were detected in 65.4%(117/179)of the patients;TP53 gene mutations were the second most common and were detected in 20.7%(37/179)of the patients.Additional mutations were found in AKT(14/179;7.8%)and PTEN(4/179;2.2%),and mutations in the remaining 7 genes were each detected in approximately 0.6%(1/179)of the patients.Excluding 6 cases of breast ductal carcinoma in situ,the remaining 280 breast cancer cases were divided into four groups by molecular subtype,and the mutation frequencies of the 11 breast cancer-associated genes differed among the four groups.Furthermore,these 280 breast cancer cases were divided into two clinically relevant therapeutic groups: the HR+ /HER2-and triple-negative groups.The triple-negative group had a high frequency of TP53 mutations(21.8%)and a low frequency of PIK3 CA mutations(21.8%),whereas the HR+ /HER2-group harbored TP53 mutations at a low frequency(10.1%)and PIK3 CA mutations at a high frequency(50.0%).Cancerous,paracancerous,and normal tissues were collected from 72 patients and subjected to next-generation sequencing.The types and frequencies of somatic nonsynonymous mutations differed among the three studied tissue types,reflecting the genetic heterogeneity of different tissues from the same individual.In addition,tissues from70 patients(excluding 2 patients with ductal carcinoma in situ)were divided into four groups according to molecular subtype,and the gene mutation frequencies in cancerous,paracancerous,and normal tissues differed among the four groups.After normalization,gene mutations were detected at a higher rate in cancerous tissues than in paracancerous and normal tissues in all groups,except for the HER2-positive group(which had a small sample size).In addition,Cox multivariate analyses of clinicopathological data,gene sequencing results,and 5-year survival rates of the286 patients showed that gene mutations in the PTEN-PI3K/AKT signaling pathway were independently associated with a poor prognosis(P=0.044),especially for triple-negative group(P=0.038).The objectives of the the second part were to innvestigate the impact of miR-206 on transmembrane 4 L6 family member 1(TM4SF1)in TNBC for therapeutic purpose.The results showed that twenty breast cancer tissues from diagnosed breast cancer patients were analyzed viareal-time PCR and Western blotting for expression of TM4SF1 and miR-206.The expressionof TM4SF1 was studied in relationship with miR-206 in MDA-MB-231 cells.The biological impact of TM4SF1 and miR-206 on MDA-MB-231 cells and BALB/c nude mice model was studied using proliferation,transwell migration,and invasion assays both in vitro and in vivo.In conclusion,the first part indicates that gene mutation spectra of breast cancer cases in Northeast China differes from those in Europe,the United States,Japan,South Korea,and southern China.Mutations in the PTEN-PI3K/AKT signaling pathway may be valuable in the prediction of the prognosis and survival of breast cancer patients,especially for TNBC.In addition,miR-206 negatively regulated gene expression of TM4SF1 in TNBC;miR-206 affects the migration and invasion of MDA-MB-231 cells by targeting TM4SF1;In vivo,miR-206 inhibits the invasive growth and lung metastasis of MDA-MB-231 cells by targeting TM4SF1.These findings indicate that miR-206/TM4SF1 could be used as a potential therapeutic agent/ target for TNBC.