Role of BRCA1 in the Epithelial-Mesenchymal Transition (EMT) and Response to TGF-β1 in Breast Cancer Cells
Dan Li 3, Shane R. Stecklein1,3, Lisa M. Harlan-Williams2,3, Easwari Kumaraswamy1,3, Kelli E. Valdez1,3, Fariba Behbod1,3, and Roy A. Jensen1,2,3
1Department of Pathology and Laboratory Medicine, 2Department of Anatomy and Cell Biology, 3The University of Kansas Cancer Center
Background: In breast cancer, invasive ductal carcinoma (IDC) patients were observed to have a significantly lower expression of breast cancer susceptibility gene 1 (BRCA1), compared to patients with ductal carcinoma in situ (DCIS). Recent studies demonstrate that cancer cells undergoing epithelial-mesenchymal transition (EMT) may acquire invasive, metastatic and progressive carcinoma characteristics. EMT can be induced in vitro by exposing the cancer cells to various growth factors, such as transforming growth factor (TGF)-β1. The objective of this study is to investigate the role of BRCA1 in the EMT of breast cancer cells before and after TGF-β1 treatment. Methods: HCC1937 (BRCA1 deficient) and HMLE (human mammary epithelial) cell lines were evaluated for a number of EMT marker genes, CD44high/CD24-/low stem-like cell phenotypes, mammosphere formation, and invasion and migration ability. TGF-β1 (2.5ng/ml) was used to induce the EMT in breast cancer cells for 1, 4, 7, and 10 days. Results and conclusion: The expression of vimentin and slug increased, whereas E-cadherin and claudin-1 expression decreased in the breast cancer cells which lost BRCA1, compared to the cells expressing BRCA1. The ratio of CD44high/CD24-/low stem-like cells was higher in the breast cancer cells with less BRCA1 expression. Furthermore, the migration and invasion ability increased in the BRCA1-deficient HCC1937 cells, and the mammosphere forming efficiency increased in the HMLE cells upon BRCA1 knockdown. After TGF-β1 treatment, significant change of EMT marker genes was observed in the HCC1937 cells with the BRCA1 deficiency, whereas less change was observed in BRCA1-reconstituted HCC1937 cells. Thus, BRCA1 may contribute to the regulation of EMT phenomenon in these breast cancer cells, which indicates its potential role in the invasion and metastasis in IDC patients.