Objective:To investigate the role of Twist, E-cadherin and ER in the tumorigenesis, progression, invasion and metastasis of breast cancer, the expression and correlation of Twist, E-cadherin and ER in human breast cancer cell lines and invasive ductal carcinoma(IDC) samples were detected using RT-PCR and Immunohistochemistry. Methods:1. RT-PCR was employed to measure the expression of Twist, E-cadherin and ER mRNA in different invasive breast carcer cell lines (MCF-7, MDA-MB-435, MDA-MB-231, ZR-75-30) and16specimens of human IDC tissue and adjacent tissue, and the relationship of the expression levels with the invasive and metastatic characteristics was analyzed.2. By using immunohistochemical method, the expression of Twist, E-cadherin and ER protein in breast carcer cell lines as well as IDC and adjacent tissues was tested. The correlation of Twist, E-cadherin and ER was studied too.3. SPSS13.0statistics software was applied to analyze the results of experiment. T-test was used to compare the measurement data, while the enumeration data were compared by Fisher’s exact probability test, P<0.05indicating significant difference. Using the correlation parameters Spearman inspection, the correlation analysis was carried out. Results:1. RT-PCR results showed that Twist gene expression in MDA-MB-435, MDA-MB-231and ZR-75-30cell lines with high ability of invasion and metastasis was higher than that in MCF-7without ability of invasion and metastasis, while the expression of ER and E-cadherin was much more higher in MCF-7cell lines than those in MDA-MB-435, MDA-MB-231and ZR-75-30cell lines. In IDC tissues and adjacent tissues, the expression of Twist mRNA was1.05±0.52and0.25±0.13respectively, the expression of E-cadherin mRNA was0.03±0.03and0.11±0.06respectively, the expression of ER mRNA was0.04±0.03and0.37±0.31respectively. The differences were statistically significant in above-mentioned groups,(P<0.05).2. Immunohistochemistry results showed that the expression of Twist in high invasive and metastatic breast cancer cell lines MDA-MB-435, MDA-MB-231, ZR-75-30was significantly higher than those in non-invasive and non-metastatic breast carcer cell lines MCF-7, however, the expression levels of E-cadherin and ER was opposite to that of Twist. Negative correlation was observed between the expression of Twist and E-cadherin/ER protein, while positive correlation was gained between the expression of ER and E-cadherin protein. The expression rate of Twist in IDC tissues and adjacent tissues was81.3%and25%respectively. The positive expression of E-cadherin and ER were31.3%,37.5%in IDC tissues, and were75%and87.5%in adjacent tissues respectively(P<0.01).3. The correlation analysis showed that there were negative correlations between Twist and E-cadherin expression (r=-0.787, P<0.05; r=-0.713, P<0.01) and between Twist and ER (r=-0.741, P<0.05; r=-0.620, P<0.05) expression in IDC tissues in mRNA and protein levels.. There was a positive correlation between E-cadherin and ER in IDC tissues(r=0.854, P<0.01; r=0.592, P<0.05). Conclusions:1. In the level of mRNA and protein, the higher expression of Twist and the lower expression of E-cadherin and ER in IDC were related with tumorigenesis and progession of breast carcer.2. The higher expression of Twist and the lower expression of E-cadherin and ER in IDC were related to the invasive and the metastatic potentiality, which indicating that Twist, E-cadherin and ER may play an important role in the process of invasion and metastasia of breast cancer.3. There were negative correlations between Twist and E-cadherin/ER expression and positive correlation between E-cadherin and ER expression in breast cancer, suggesting that united measurement of the expression of Twist, E-cadherin and ER is helpful to predict metastasis and prognosis of breast cancer.This result may provide important clues in the clinical therapy of brest cancer.