Quantitative impedance-based characterization of breast cancer cell migration and metastatic potential

Cellular impedance-based assays offer a sensitive, label-free, and non-destructive method to continuously monitor cells in real time, allowing the assessment of both kinetics and degree of migration for breast cancer cells. A scratch assay is one of the most commonly used methods for testing cell migration in a two-dimensional (2D) monolayer culture. Traditional methods to evaluate 2D cancer migration commonly use image analysis to determine the rate of wound closure over a set of timepoints as an indicator of migratory/metastatic potential for cancer cells. An impedance-based assay system was employed towards establishing a modified wound healing assay technique that can measure wound coverage and therefore, 2D cancer migration continuously. This method can also be used to measure a variety of cell characteristics, including proliferation and epithelial barrier integrity.

Using the Maestro Z Live-cell Analysis System by Axion Biosystems, cell spread, related to single cell morphology, and cell proliferation were observed for multiple breast cancer cell lines. A distinct quantifiable difference in the behavior of aggressive triple-negative breast cancer cells (HCC1806, MDA-MB-231), compared to less aggressive luminal MCF7 cells was determined. With an established assay method, cells were then treated with pro-inflammatory cytokine leptin, which plays a crucial role in metabolism and epithelial to mesenchymal transition (EMT), to verify assay sensitivity. The effects of leptin concentration in media were measurable for MCF7 and HCC1806 cells, and cell barrier integrity was significantly higher in the luminal MCF7 cells as compared to the more aggressive triple-negative cell lines. Cell migration to close a physical wound was measured over 36 hours, with the modified wound healing assay providing quantifiable evidence that the more aggressive breast cancer cells migrated to close the gap.

This work validates the use of cellular impedance-based assay systems to evaluate multiple cell characteristics. In a single experiment, cell spread, cell proliferation, cell-cell barrier integrity, and 2D cell migration were able to be quantified. These findings parallel previously published data for cell migration of the specific cell lines used, while highlighting the role of leptin in cancer behavior. Overall, the potential for a bioelectronic impedance assay system was demonstrated and its validity in effectively detecting and quantifying cell behaviors was proven.