Real-time impedance assay to follow the invasive activities of metastatic cells in culture

Abstract

Here we present research detecting the invasive activities of metastatic cells in vitro using electric cell-substrate impedance sensing (ECIS™). The assay is based on previous microscopic observations, where metastatic cells added over established endothelial cell layers were observed to attach to and invade the cell layer. Human umbilical vein endothelial cells (HUVECs) were first grown to confluence on small gold electrodes. The impedance of these electrodes was followed after the addition of suspensions of different sublines of the Dunning murine prostatic adenocarcinoma series (G, AT1, AT2, AT3, ML, and MLL). For highly metastatic sublines, within an hour after being challenged, the impedance of the confluent HUVEC layer was substantially reduced. The effect of the weakly metastatic sublines was less pronounced, and the extent and the rate of this drop in impedance could be correlated with the metastatic potential of each of six sublines tested. The real-time assay is effective in both normal and low (1%) serum concentrations, and the detected activity requires the presence of viable transformed cells. In addition to the murine cell lines, similar behavior was observed using four established human prostatic cancer lines (DUI45, PC3, TSU, and PPC1). These results suggest that this ECIS-based assay might be used with primary human cultures to establish the metastatic abilities of cells isolated from biopsies.