The extent to which protein targets are modulated by drugs or small molecule compounds depends on a number of factors, including the expression levels of the target, the effective concentration of the compound, and the time needed for the compound to perturb the target. One of the limitations of current multidimensional phenotypic profiling approaches is that typically a single time point is chosen to assess the effect of compounds. The conclusion, regarding the compounds´ mechanism of action, is based on the time point at which the samples are processed.
To address these restrictions, researchers Abassi et al. have devised a live cell morphological profiling approach for dynamic monitoring of the effect of small molecule compounds that was based on impedance measurement of cells with the xCELLigence RTCA System of Roche Applied Science (SIX: RO, ROG; OTCQX: RHHBY). The approach was tested by screening a library containing FDA approved drugs, experimental compounds, and natural compounds. Compounds with similar activity produced similar impedance-based Time-dependent Cell Response Profiles (TCRPs). The compounds were clustered then based on TCRP similarity.
The researchers identified novel mechanisms for existing drugs, confirmed previously reported calcium modulating activity for COX-2 inhibitor celecoxib, and discovered an additional mechanism for the experimental compound monastrol. They also recognized and characterized a new antimitotic agent. This approach will also help to detect the off target effect of a given compound.
The TCRP technique described by Abassi et al. can overcome the limitations of current approaches, because the profile generated is time dependent. In combination with measurement of cell number, morphology, and adhesion, the TCR technique allows greater expansion of the ‘‘biological space’’ at which compounds are screened. It provides ample opportunity to detect and identify biological activity associated with small molecules.
In conclusion, these findings indicate that the time-dependant resolution, provided by the TCRP approach, can be used in conjunction with phenotypic profiling approaches to obtain additional data associated with small molecule compounds. TCRP approach provides predictive mechanistic information for small molecule compounds.
The non-invasive and label-free xCELLigence analysis method, originally invented by ACEA Biosciences in San Diego, USA is based on measuring the impedance of cells. The technique utilizes an electronic readout of impedance to non-invasively quantify cellular status in real-time. Cells are seeded in E-Plate microtiter plates, which are integrated with microelectronic sensor arrays. The interaction of cells with the microelectrode surface generates a cell-electrode impedance response, which not only indicates cell viability but also correlates with the number of the cells seeded in the well. In conjunction with its user-friendly data collection and analysis capabilities, the xCELLigence System makes a unique platform for continuous, real-time cell-based assays and provides a huge opportunity for cellular and molecular biology.