Abstract 909: Tracking of migration using digital holography to monitor drug-induced phenotypic shifts in breast cancer cells

Abstract

Abstract This study aims to investigate the migration behaviour of individual JIMT-1 breast cancer cells during the cell cycle. Mechanisms behind cell migration are important to unravel in the context of cancer relapses caused by distant metastases. JIMT-1 cells were cultivated in normoxia or hypoxia and treated with 0.5 µM of the cancer stem cell inhibiting compound salinomycin. The cells were imaged in a digital holography microscope placed in a regular cell culturing CO2 incubator (normoxia) or in a hypoxia chamber (1% O2). In digital holography, a laser beam is split into two beams - the reference beam and the object beam. The object beam is directed through the sample, where the difference in refractive index between air, the cell medium, and the cell body induces a phase shift in the laser beam. After having passed the object, the beam is merged with the reference beam giving an interference pattern, which is used to construct a three-dimensional image of the cells in a software program. The laser is non-phototoxic and therefor it can be used for long-term studies. In our study, images were acquired every 5th minute during a 72-hour incubation period. After acquisition, the individual cells in the images were tracked throughout the time lapse. Cell movement is described by three parameters: motility, which is the length of the total cell movement path, migration, which is the shortest distance from the start to the end position, and migration directness, which is migration divided by motility. When cells were exposed to hypoxia and/or treated with salinomycin, the cell cycle time increased compared to non-treated cells in normoxia. When the cell cycle time increased, motility increased as well. However, migration directness decreased despite increase in motility implying increased local movement of cells treated with salinomycin compared to control cells. We have previously shown that salinomycin-treated JIMT-1 cells obtain an epithelia phenotype (Huang et al., 2016). Thus, we decided to investigate a breast cancer cell line with epithelial traits i.e, the MCF-7 cells. The MCF-7 cells behaved like the JIMT-1 cells treated with salinomycin i.e. the motility was high and the migration directness was low. Thus, we suggest that cells with mesenchymal and epithelial traits can be distinguished using digital holographic imaging based on motility and migration directness and that drug-induced phenotypic shifts can be studied using this technique.