Influence Of IL-6 On Infiltration And Invasion In Breast Cancer

Objectives: Interleukin-6(IL-6), one of pleiotropic cytokines, has been found to be involved in immune regulation and modulation of cellular growth. The high expression level of serum IL-6 has been found in different types of malignant neoplasm, which specially indicated poor outcome for breast cancer patients in our previours research. However, the sourse of serum IL-6 and the mechanism are still uncovered fullyunder in breast cancer. Epithelial-mesenchymal transition plays important roles in a wide range of biological activities during the development and progression of malignancy.Meanwhle EMT is the important cytology foundation in the process of invasion and metastasis for malignant tumor. This study aimed at elucidating the expression of IL-6 and its clinical significance in human breast cancer, as well as exploring whether IL-6 influeces on their biologic behaviors and functions by inducing EMT in breast cancer cells.Methods: 1. Immunohistochemical staining was performed to evaluate the expression of IL-6 and epithelial-mesenchymal transition(EMT)–related proteins in 68 breast cancer tissue samples. The correlation between IL-6 and clinicopathological parameters and epithelial-mesenchymal transition(EMT)–related proteins were further investigated. 2. We used RT-PCR to detect the relative expression of m RNA of IL-6 in breast cancer cell lines MCF-7 and MDA-MB-231. Different methods were conducted to culture the two breast cancer cells according to the result of RT-PCR. 3. Cells in different groups were collected to the following test. Wound scratch assay and transwell assay were used to further investigate the effect of IL-6 on the ability of migration and invasion in differently treated breast cancer cell lines. 4. The level of expression of epithelial-mesenchymal transition(EMT)–related proteins was validated by Western Blot after we collected cytoplasmprotein extraction from cells in different groups.Results: 1. The expression of IL-6 was observed in the carcinoma nest rather than the mesenchymal cells. 36 breast cancer patients overexpressed IL-6 and the over-expression rate was 52.9%. 2. IL-6 expression was significantly correlated with lymph nodes invasion(p=0.003) and pathological TNM stage(p=0.012) of breast cancer patients, rather than other parameters(p>0.05). 3. The expression of E-cadherin decreased(r=-0.320,p=0.008), β-catenin was translocated to cytoplasm(r=0.267,p=0.028) and the expression of Vimentin increased in IL-6high samples(r=0.281,p=0.020), compared with IL-6low samples. 4. The level of m RNA of IL-6 in MDA-MB-231 cells was significantly higher than that of MCF-7 cells(p=0.0004). 5. Wound healing assay and tanswell assay showed that their migration and invasion ability were significantly enhanced when the MCF-7 cells were treated with IL-6-conditioned medium, while the migration and invasion ability of MDA-MB-231 cells were significantly inhibited when IL-6 was neutralized with its monoclonal antibody, compared with the control groups. 6. When MCF-7 cells were cultured with IL-6-conditioned medium, the expression level of the epithelial marker E-cadherin deseased, but mesenchymal marker β-catenin and transcription factors Slug and Snail increased as determined. On the contrary, MDA-MB-231 cells showed the completely opposite consequence after their IL-6 was neutralized with its monoclonal antibody.Conclusions: 1. The expression of carcinoma-derived IL-6 was associated with invasion and metastasis in breast cancer patients. 2. A correlation between the expression of carcinoma-derived IL-6 and epithelial-mesenchymal transition(EMT)–related proteins was observed, indicating that carcinoma-derived IL-6 could induce EMT in breast cancer patients. 3. IL-6 could promote migration and invasion of breast cancer cells by inducing EMT in vitro.