Study On The Function Of Transcription Factor Slug In Breast Cancer

A critical process "Epithelial-Mesenchymal Transition(EMT)" plays an important role in tumor development, progression and metastasis, especially in the study of breast cancer, which has been treated as a major threat to human health. As one of the transcription factors induding EMT, Slug has been recognized as a key molecular in the process of EMT and other aspects of tumors.In this study, by using lenti-virus mediated RNA interference and cDNA microarray analysis, we established a Slug knockdown MDA-MB-231cell line and several genes whose expression could be modulated by Slug were identified, including our final target gene ARHGDIB. Further, by using real-time PCR and Western Blot, we confirmed the expression modulation of ARHGDIB by Slug, but the result of dual-luciferase assay indicated that Slug might not play a significant role in regulating the activity of ARHGDIB promoter.By RhoGTPases activity assay in a series MDA231related cell lines, we proved that Slug could postively regulate the expression of RhoA, and both the expression and activity of Racl and Cdc42. Our immuno-staining experment results suggested that the Slug expression interference could transfer RhoGDI2protein from nucleus to cytoplasma, which provided one possible mechanism explanation for the regulation of RhoGTPases by Slug.Furthermore, we also proved that Slug could have a positive effect on the expression of c-Jun and both expression and phosphorylation level of JNK, while an opposite effect on the expression of Fral. Besides, the positive regulation of ARHGDIB promoter activity and protein expression was also confirmed, suggesting a critical role of c-Jun in the moduation of ARHGDIB by Slug. In sum, Slug related gene modulation network in breast cancer cell line was preliminary established and related regulations between Slug and RhoGDI2or RhoGTPases were well defined. These results provided possible explanations for some critical problems involved in breast cancer and also laid a solid foundation for further mechanism study.