Phosphoproteins and the dawn of functional phenotyping.

Phosphorylation is one of the most important processes in cell signal transduction. Detection of phosphorylated proteins in cancer tissue is useful for prognosis and diagnosis, and it might be very helpful in monitoring treatment using targeted therapy. For these reasons, the in situ quantitative measurement and subcellular localization of phosphoproteins will likely be important. However, phosphoproteins are extremely labile, a likely explanation for inconsistent or contradictory reports. Thus, the development of new paradigms for tissue handling, immunostaining, and quality control are needed.