Roche's xCELLigence System Offers Dynamic and Label-free Assessing of Kinase Activity in Living Cells

The central role of receptor tyrosine kinases (RTKs) in cellular processes, especially in cancer, has made them an important target for several antibody- and small molecule-based inhibitors specific for various RTKs for the treatment of different tumour entities. The electrical impedance detection method with Roche's real-time cell microelectronic sensor-based platform xCELLigence system is a facile, high content, and cell based kinase assay allowing for monitoring short term RTK activation and the long term biologic effect of the activation in real time in a single well. The novel technology has improved utility over existing in vitro and cell based assay in the identification and characterization of selective and potent kinase inhibitors, as shown in a recent study.

Several approaches have been developed to identify RTK inhibitors such as antibody-dependent and independent technologies. However, most of these current approaches are end point, in vitro based assays that require substantial reagent optimization, and are inadequate in providing information on their effective intracellular activity. Roche Applied Science’s xCELLigence System – originally invented by the US-based ACEA Biosciences and co-developed by Roche and ACEA - addresses several of these limitations. Unlike other RTK assays, this technology is cell-based, label-free, capable of monitoring cellular changes in real-time, and non-invasive. The method utilizes an electronic readout of impedance to quantify cellular status, including cell number, viability, morphology, and cytoskeletal dynamics. Cells are seeded in E-Plate microtiter plates, which are integrated with microelectronic sensor arrays. The interaction of cells with the microelectrode surface leads to the generation of a cell-electrode impedance response, which indicates the status of the cells in terms of morphology, quality of adhesion and number.

According to experimental data, the xCELLigence System provides a facile, easy platform for identification and further characterization of RTK inhibitors. In a recent study¹, the kinetic of epidermal growth factor (EGF)-mediated changes of COS7 cells pretreated with epidermal growth factor receptor (EGFR) inhibitor and insulin were monitored using the xCELLigence System.

As the authors concluded, the electrical impedance detection method was able to screen, identify, and characterize a potent and selective EGF receptor inhibitor from a compound library. The assay quantified morphological changes in response to growth factor treatment and therefore mimics proximal events in kinase activation. Additionally, the xCELLigence System provided valuable information about the state of the cell and the signalling pathways being activated. Furthermore, the technology does not require intensive optimization or special reagents such as peptides, antibodies, or probes, nor suffers from assay component interference. Since the readout is non-invasive, multiple treatments can be performed in the same well. The assay can also be used in conjunction with other existing cell-based assays for RTK. More important, because the assay is cell based, the studies are done in a physiologically relevant environment, allowing for concurrent assessment of a compound's solubility, stability, membrane permeability, cytotoxicity, and off-target interaction effects. Finally, the system requires very little user training, making this assay amenable for use in both primary and secondary screens.

For more information on the technology, please visit the article webpage.

¹ xCELLigence System, Application Note No. 4, 2008, Roche Applied Science.