World-wide, metastasis continues to be the leading cause of death in cancer patients. Although epithelial-to-mesenchymal transition (EMT) and mesenchymal-to-epithelial transition (MET) have been implicated in the incidence of cancer metastasis and drug resistance, their impact in cancer progression and patient survival is not fully understood. This is partly due to the lack of suitable in vitro models. Thus, to facilitate the utility of the EMT concept in therapeutic development, we have utilized some of the basic biology of EMT/MET to create a novel advanced in vitro model for use in both basic research and discovery of new anti-EMT drugs.
In breast cancer, vimentin (VIM) intermediate filament (IF) proteins are generally upregulated during EMT and down-regulated during MET. Here, we employed CRISPR/Cas9 gene-editing technology to generate a VIM RFP (red fluorescent protein) reporter in the MDA-MB-231 (ATCC® HTB-26™) breast adenocarcinoma cell line. The VIM RFP C-terminal fusion gene at the endogenous VIM locus enables end-point or real-time tracking of the MET status as cells transition from the mesenchymal to epithelial phenotype under distinct conditions. We have validated the cell line at the nucleic acid (genomic and mRNA) and protein levels as well as in cell-based assays. Bio-functional evaluation of the MDA-MB-231 VIM RFP (ATCC® HTB-26MET™) cell line shows sensitivity to metastatic breast cancer drugs axitinib (tyrosine kinase inhibitor) and U0126 (MEK1/2 inhibitor) via the inhibition of the inherent signaling pathways which impact EMT. These effects provide the basis for the use of this cell line in high-throughput screening (HTS) applications such as the discovery of new anti-EMT drugs for metastatic breast cancer. Furthermore, the MDA-MB-231 VIM RFP reporter cell line is also a convenient and sensitive model for studying the mechanisms of metastasis and for basic science research.