Abstract: Background and purpose: Pathogenic gene polymorphism may affect the function of gene, leading to the difference of individual tumor susceptibility and heterogeneity of bioactive substances in individuals. The purpose of this study was to investigate the interrelationship between HER-2 gene polymorphism and its protein expression, and to evaluate their association with the clinicopathological characteristics of breast cancer. Methods: The data from a total number of 303 female breast cancer patients of Han ethnicity were collected. The MassARRAY platform was used to examine HER-2 gene rs2517954 and rs2517955 single nucleotide polymorphisms. Meanwhile immunohistochemistry was used to detect HER-2 protein expression and corresponding estrogen receptor (ER), progesterone receptor (PR), P53 and Ki-67 expressions in breast cancer tissues. Pearson chi-square test was used to study the relationship of the two loci and the protein expression, and their correlation with clinicopathological features of breast cancer was analyzed. Results: Under the codominant model, HER-2 gene rs2517954 and rs2517955 loci polymorphisms were associated with its protein expression (χ²=9.613, P=0.008; χ²=9.613, P=0.008). And under the dominant model, HER-2 gene rs2517955 loci TT homozygous and CT heterozygous mutant was associated with its protein expression (χ²=8.894, P=0.003). There were no significant correlations between HER-2 gene rs2517954, and rs2517955 loci polymorphisms, and breast cancer patients’ clinical stage, tumor size, histological grade, lymph node metastasis, ER, PR, Ki-67 and P53 expressions (P>0.05). Conclusion: HER-2 gene rs2517955 loci polymorphism is correlated with its protein expression. Further studies may be helpful to elucidate the mechanism of HER-2 protein expression in breast cancer.

Key words: Breast cancer, HER-2 gene, Gene polymorphism, rs2517954, rs2517955