(160c) Studying Phenotype Differences of Prostate Cancer Cells Using Electrical Impedance Spectroscopy

Cancer cell plasticity, defined as the ability of a cancer cell to change its phenotype, in response to the microenvironment, is a key factor that limits the effectiveness of chemotherapy. Furthermore, it is difficult to identify and eliminate drug-resistant cancer cells found in static and metastatic tumors. Establishing techniques for real-time monitoring of changes in chemoresistance, therefore, important for understanding cancer cell dynamics and their plastic properties. A microfluidic device coupled with electrical impedance spectroscopy (EIS) can be used to monitor these changes. EIS is a label-free, noninvasive method that uses a frequency-dependent signal to measure the magnitude and phase angle of the impedance. Cell electrical properties (inductance, capacitance, and resistance) can be obtained using a resistor-capacitor circuit model. Variance in these electrical properties provide key information about unique signatures, or biomarkers, related to the behavior of these cancerous cells. In this work, we utilize EIS to study the electrical characteristics and phenotype changes for (1) prostate cancer cell lines DU145 and PC-3 (2) 2D and 3D cell culture, and (3) cells in the presence or absence of the anti-cancer drug Nigericin. To validate observations of phenotypic change, we used RT-qPCR gene expression markers E-Cadherin (CDH1) and Tight Junction Protein 1 (ZO-1). In the results, we found that EIS can distinguish between DU145 and PC-3 cell lines based on the differing impedance magnitude and phase angle. The impedance spectra for DU145 cells were higher than PC-3 cells, indicating that EIS can also potentially differentiate between cell membrane thickness. Additionally, we found that impedance can distinguish between phenotypes by growing the cells as 2D monolayer or 3D suspension, measuring their impedance and validating the data by looking at the PCR markers. Within the 2D PC-3 cells, the impedance magnitude was inversely related to the expression levels of CDH1 and ZO-1. For the 3D DU145 cells there is moderate inverse correlation between the impedance magnitude and E-cadherin. It was more difficult to find trends between 3D PC-3 cells, impedance, and PCR markers. The same was true for 2D DU145 cells. Another detectable phenotype change was found with in vitro age. The impedance spectra of both DU145 and PC-3 cells were measured at Day 1, Day 3, and Day 7of cell growth. For the PC-3 and DU145 cells, it was found that Day 1 did not have a large difference in the impedance spectra for the 2D and 3D culturing methods. The same was true at Day 7 for both cells. However, at Day 3 there was a discernible difference in the impedance values for the PC-3 and DU145 cells. This is significant because it is hypothesized that at Day 3 of 3D cell culture, cells are more chemoresistant. Studying the time period is important for understanding how 3D cell culture techniques can be used to model chemoresistance in vivo. To further study this, we assessed the cells when treated with Nigericin. 2D and 3D PC-3 cells were treated with high concentration of drug at 10μM for 48hr and 96hr to assess cell viability. There was a detectable impedance change for the 2D cells, the impedance increased indicating cell death. In the 3D cell culture, the impedance values did not vary as much based on the control and high concentration of drug added. Further development and verification of EIS will allow for the characterization of a wide range of other cell types in the future. Overall, this label-free method has much to contribute to research, diagnosis, and treatment of cancerous cells.