Flow cytometry as platform for biomarker discovery and clinical validation

Abstract

Flow cytometry (FC) is a highly versatile method that is constantly expanding. Its field of application is extremely wide (oncology, hematology, transplantation, autoimmunity, tumor immunology, chemotherapy, etc.), making it highly useful not only in the discovery of new biomarkers but also in clinical validation and routine implementation. FC simultaneously provides information about the phenotypic and functional characteristics of cells and enables quantification of large numbers of cells and assessment of their subset distribution, activation status, cytokine production profile, and other cellular functions. Furthermore, because FC allows the performance of many different types of assays (immunophenotyping, intracellular staining, cell cycle, cell proliferation, apoptosis, phosphoflow assays, etc.), it yields different types of information, ranging from elucidation of mechanisms of action (for drugs and disease progression) to functional assays. This technique plays an important role in the prioritization, verification, and clinical validation of new biomarkers. However, because of the high complexity of the panels of reagents involved, greater expertise is needed for correct interpretation of the data obtained, and the technique continues to have several limitations. One of the most important limitations is the lack of standardization in assay and instrument setup, as well as the absence of good quality controls, especially external controls. There is a need to develop mathematical algorithms able to predict clinical evolution/disease progression based on FC measurement of biomarkers. New biostatistics models should be developed to establish the most appropriate correlation among biomarkers, drug effect, and clinical outcome, which would allow personalized treatment.