Abstract: Background and purpose: The study of molecular markers for breast cancer is helpful to diagnosis of the disease and prediction of prognosis in breast cancer patients. The purpose of this study was to investigate the relationship between JMJD3 and Ki-67 and molecular typing and clinicopathological characteristics in invasive ductal carcinoma of breast. Methods: The levels of JMJD3 and Ki-67 were examined on tissues of 57 normal controls, 38 low-grade ductal carcinoma in situ, 52 high-grade ductal carcinoma in situ and 150 primary invasive ductal carcinoma of breast in People’s Hospital of Henan University of Chinese Medicine by immunohistochemical method. The levels of JMJD3 and Ki-67 were assessed quantitatively using Image-Pro Plus image analysis software, and their relationship with molecular subtypes and clinicopathological characteristics of breast cancer was analyzed. Results: Positive intensity of JMJD3 in normal control tissues, low-grade ductal carcinoma in situ, high-grade ductal carcinoma in situ and invasive ductal carcinoma of breast was decreased sequentially, whereas Ki-67 intensity was increased. The levels of JMJD3 and Ki-67 were positively correlated with the degree of histologic differentiation, lymph node metastasis status, TNM stage and molecular subtypes (P<0.05). The receiver operating characteristic (ROC) curve showed that the sensitivity and specificity of diagnosis of breast cancer were higher when the JMJD3 diagnostic threshold was less than 10.87 and the Ki-67 diagnostic threshold was more than 8.08. JMJD3 expression was negatively correlated with Ki-67 proliferation index (r _P =-0.540, P=0.000). Conclusion: JMJD3 and Ki-67 play an important role in the development of breast cancer. High expression of JMJD3 inhibits proliferation of breast cancer cells, and the specific molecular biological mechanism needs further study.

Key words: Invasive ductal carcinoma of breast, JMJD3, Ki-67, Correlation, Molecular subtypes