(229bp) Detection of Epithelial-to-Mesenchymal Transition in Breast Cancer Cells Using Endoplasmic Reticulum Stress

Epithelial-to-mesenchymal transition (EMT) is a complex remodeling of cell signaling pathways that activates metastatic abilities in cancer cells. Detection of EMT is essential for evaluation and management of cancer progression in patients. EMT is commonly detected using cell morphology changes and EMT markers expression, however, real-time detection of EMT in live cells is challenging. Endoplasmic reticulum (ER) stress is due to accumulation of unfolded proteins in the ER lumen, and has been related to EMT in cancer. Here, we describe the previously unknown role of ER stress in EMT in breast cancer cells, and evaluate the use of ER stress as an indicator of EMT. We have observed that induction of EMT in mammary cell lines using TGF-β1 is accompanied by a transient increase of ER stress, as measured by immunostaining of GRP78 marker. Surprisingly, specific inhibition of ER stress using 4-PBA during EMT induction does not affect early EMT marker ZEB1, however, it completely blocks the induction of late EMT markers E-cadherin and Vimentin. Considering the essential role of ER stress in EMT in mammary cells, we hypothesized that measuring the transient ER stress increase after TGF-β1 treatment would a good indicator of EMT. Thioflavin T (ThT) is an inexpensive fluorescent compound capable of quantitatively detecting ER stress in live cells. We observed that ThT can be used conveniently to detect the transient increase of ER stress during EMT in live breast cancer cells at the single cell level. We expect that this new inexpensive and easy-to-use EMT detection method will help the investigation of EMT in breast cancer, in laboratory and clinical settings.