Marked Out: Identifying Biomarkers with Flow Cytometry

To meet the challenge of evaluating new therapeutics, the pharmaceutical and biotechnological industry has turned to cutting-edge technologies and multiple platforms in order to develop specific tests designed to identify biomarkers and testing endpoints that will define drug efficacy. This emphasises the need for strong research and development efforts, focused on understanding unique drug activity and the disease processes they may target very early on in the evaluation of novel therapeutics. The availability of ‘cross-over’ testing platforms that combine multiple technologies/methodologies is becoming invaluable to the process of developing analytical systems that will identify specific biomarkers for use in clinical trials. With the new generation of targeted therapies, the drug development industry is starting to experience a paradigm shift away from basic testing performed on plasma or serum components, toward analysis systems that are cell-based.

Flow cytometry is a unique technology platform that has the capability to count, examine and sort cells/particles suspended in a fluid stream. It allows simultaneous multiparametric analysis of the physical and/or chemical characteristics of single cells flowing through an optical and/or electronic detection matrix. When flow cytometry was first introduced, about 30 years ago, it was primarily used as a research tool to identify and/or sort specific cell populations from culture or whole blood by using fluorescently labelled antibodies that could detect cell surface markers/receptors. The first real clinical applications of this technology was associated with monitoring changes in T-cell subsets or activation markers in transplant patients or patients infected with the HIV virus.

For some time it was thought that the technology, although unique, was limited in its capacity to provide information beyond the level of cell identification. However, major advances such as:

• Methods/reagents that resulted in the ability to detect more unique antigens/receptors, perform quantitative fluorescent for expression analysis and to identify and detect intracellular proteins in permeablilised cells
• Methods/reagents that resulted in the ability to detect cell function
• Methods/reagents that combined the technologies of molecular biology and flow cytometry resulted in the ability to detect specific RNA and DNA sequences within cells

These, to name a few, pushed the technology into the realm of drug discovery and development.