Abstract: Objective To investigate the mutations and polymorphisms of NBS in breast cancer in north Chinese. Methods Direct sequencing analysis of 205 normal control and 188 breast cancers. Result There is no NBS gene mutation was detected in breast cancer patients. Four major NBS polymorphisms were detected, and D399D of NBS gene was significantly associated with risk of breast cancer. Comparing to D399D AA genotype, AG and GG genotype was associated with substantially increased risk of breast cancer in north Chinese (odd ratio = 2.34 and 1.93, 95% confidence interval = 1.34-4.07 and 0.93-4.02, respectively). Conclusion Current evidence suggests that NBS polymorphism D399D might contribute to the risk for breast cancer in north Chinese.

Key words: DNA repair, NBS, breast cancer