Study On The Correlation Between The Sequence Variation Of Mitochondrial D-loop Region And The Prognosis Of Early Breast Cancer In Women In Fujian Province Where The Han Population Is Concentrated

Object: Because of the synergistic effect of multiple genes and stages promotes the occurrence and development of breast cancer,individual genetic factors are important factors that cannot be ignored in the prognosis of breast cancer.In the past 10 years,many studies have found that mitochondrial DNA variation is related to the development and prognosis of tumors.As the main transcriptional regulation region of mitochondrial genes,D-Loop region include copying transcription starting area and promoter of replication and transcription.Variation of the region may be able to adjust the mitochondrial gene transcription and expression,thus cause the disorder of coding gene product,which in turn,affects the outcome of a variety of diseases,including cancer,mitochondrial diseases,etc.Therefore,in this study,we sequenced 714 mt DNA specimens from peripheral blood leukocyte of early breast cancer cases to explore the association between the variants of the D-Loop region and the early-stage breast cancer outcomes.This is of great significance for the individualized treatment of early breast cancer among women in Fujian Province and even the whole country.Method: In this study,Sanger sequencing method was used to detect the complete sequence on the mt DNA D-loop region of peripheral leukocyte in 714 cases of female early breast cancer patients in Fujian Province who visited the Union Hospital of Fujian Medical University from 2003 to 2013.Breast cancer special survival(BCSS)and overall survival(OS),invasive disease free survival(i DFS)and distant disease free survival(DDFS)were the primary and secondary endpoints.Logistic regression was used to evaluate the correlation between clinicopathological factors and prognosis of early breast cancer.As significant clinicopathological factors were used as correction factors,COX multivariate regression model was used to analyze the relation of variation of 344 bases in d-loop region and the prognosis of breast cancer.Stratified analysis was performed on the selected sites to look for subgroups which have an significative impact on the prognosis.Kaplan-Meier curve and log-rank test were used to compare the survival rate between different groups.The different predictive function of clinicopathological factors and variations on survival was determined by the area under the ROC curve.Result: All the 344 D-Loop locus were detected in this study.The main types of variation are substitution(315,91.6%),insertion(12,3.5%),deletion(9,2.6%)and substitution/deletion(6,2.3%).The variation types A change to G,T change to C are the most common.COX multivariate analysis revealed that variation of loci 146 and 16266 may be related to the prognosis of EBC patients in Fujian Province.Patients with 146 C can reduce the survival time in the i DFS [ad HR = 1.39(1.05-1.85),p = 0.023].Results of two sites integration analysis show that variation on loci 146 or 16266 had statistical significance for outcomes of breast cancer[i DFS: ad HR: 1.407(1.122-1.766),p = 0.0032;DDFS: ad HR: 1.366(1.083-1.723),p = 0.0085;BCSS: ad HR: 1.475(1.149-1.895),p = 0.0023,and OS: ad HR: 1.380(1.074-1.774),p = 0.0117].The ROC curve analysis shows that the prediction of survival when using clinicopathological characteristics and two SNPs are better than using clinicopathological factors alone[for BCSS,AUC = 0.7407 VS 0.7569,p = 0.0344;for OS AUC = 0.7359 vs 0.7473,p = 0.0340].Conclusions: This study shows that when patients have 146 or 16266 variation at the same time,it can affect the recurrence,metastasis and death of early breast cancer,especially for patients with tumor > 2cm,lymph node positive,ER positive,and histological grade 3.The 146 and 16266 variation(Two SNPs at D-Loop region)may be used as predictors of breast cancer specific survival or total survival.However,it cannot be proved as a predictor of recurrence or metastasis.