Recent progress in protein profiling of clinical tissues for next-generation molecular diagnostics.

Differences in protein levels and the activation of signaling pathways have been extensively studied in tumor tissues, but the implementation of protein profiling methods in routine hospital workflows lags far behind that of nucleic acid-based approaches. In this review, major technologies that are currently used for measuring protein abundances in human tissues are highlighted, and for each method several examples are provided. We differentiate between extract-based and section-based methods that are each further divided into targeted- and discovery-based approaches (i.e., when the proteins to be analyzed are known or for finding promising new biomarker candidates, respectively). Current problems in protein profiling are addressed and ways in which protein profiling can successfully be implemented in routine clinical workflows are shown.