Complex impedance quantification of cell migration for the physics of cancer*

Cell migration is a crucial step in cancer metastasis, the complex process which accounts for over 90% of cancer-related deaths. There is emerging evidence that radiotherapeutic doses meant to kill cancer cells can promote metastasis by enhancing cell migration. Here we quantify radiation-induced changes in cell migration as part of the physics of cancer: a novel research frontier unraveling the roles of physical properties of cells in cancer. We used a standard laboratory irradiator to irradiate both non-cancer (HCN2 neurons) and cancer cells (T98G glioblastoma) with 2 Gy, 10 Gy and 20 Gy of X-rays. To assess cell migration post-irradiation, we used a commercially available device, ECIS Z-Theta, which non-invasively measures and converts complex cell-substrate electric impedance into series resistance and capacitance in real time. We also used CdSe/ZnS core-shell quantum dots to quantify molecular changes in cells following radiotherapy. Both irradiated cell lines showed significantly (p <0.01) enhanced migration compared to non-irradiated cells, within the first 40 hours following irradiation with 20 Gy. Our results suggest cell migration as a new therapeutic target in anti-metastasis strategies for improved radiotherapy outcomes.