Abstract: Objective To study the correlation of mitochondrial DNA(mtDNA) np16 189、np16 223、np16 519 and D310 region polymorphisms as well as its interaction effects with breast cancer and its pathological features in Ningxia Han population. Method Based on case-control study design, polymerase chain reaction-restriction fragment length polymorphisms (PCR-RFLP) was used to analyze the genotype and genotype frequency of the four polymorphisms of mtDNA among 195 sporadic breast cancer patients and 196 healthy controls from Ningxia Hui Autonomous Region. Chi-square test and odds ratio were used to analyze the correlation between each SNP and their interaction effects with breast cancer and pathological features. Result 1）The genotype frequency distribution differences of np16189、np16223 and np16519 between case and control group were show no significance (p＞0.05); There was significant difference of the three genotypes distribution of D310 region between case and control group (χ2=6.629, P＜0.05), individual who carry heterogeneous genotype has a lower risk to breast cancer than those carry mutant genotype (OR=0.216, 95%CI is 0.058～0.809). 2）There were no significant difference of the interactions of the four polymorphisms between case and control group (P＞0.05). 3）There were no significance difference between four polymorphisms and pathological features of breast cancer (P＞0.05). Conclusion There is no association between mitochondrial DNA(mtDNA) np16 189、np16 223、np16 519 and D310 region polymorphisms and breast cancer in Ningxia Hui Autonomous Region.

Key words: Breast cancer, mtDNA, gene polymorphism, Ningxia Han population, pathological features