Target validation in drug discovery.

The process of target validation identifies and assesses whether a molecular target merits the development of pharmaceuticals for therapeutic application. The most valuable application of high content screening to target validation is at the early stages of the process when genetic methods (including RNA interference--RNAi) are being applied to many potential targets. At this stage both throughput and indepth analysis are required. This process is illustrated using various examples from the area of oncology target validation. The Akt signal transduction pathway is used to illustrate an efficient way of identifying HCS compatible reagents for use in assay development. RNAi transfection methods are discussed. A description is given of an HCS assay that simultaneously measures two nodes of the Akt pathway: Akt substrate phosphorylation and RPS6 phosphorylation. Another example of an assay measuring proliferation (DNA synthesis) and apoptosis (Histone H2B phosphorylation) within the same cell population is used to illustrate the combination of typical phenotypic assays.