DIGE Saturation Labeling for Scarce Amounts of Protein from Formalin-Fixed Paraffin-Embedded (FFPE) Tissue

In this chapter, we describe the utility of difference gel electrophoresis (DIGE) as a proteomics platform for the global detection of expressed proteins in formalin-fixed paraffin-embedded (FFPE) tissues and its use for biomarker discovery/identification of proteins that may contribute to cancer development and progression. Formalin fixation and paraffin embedding of tissue is the standard processing methodology practiced in pathology laboratories worldwide, resulting in a highly stable form of tissue that is easily stored due to its inherent stability at room temperature. Consequently, FFPE tissues represent an attractive reservoir of clinical material for conducting retrospective protein biomarker analysis. A limitation for proteomics research in this type of clinical sample is the amount of viable protein that can be obtained from fixed tissues. Tissue biopsies are precious samples that can generally be acquired in very small amounts due to the invasive nature of the sample collection, mainly during surgery or biopsy. Subsequently, the amount of extracted protein can be, in many cases, very limited. The saturation DIGE technology has emerged as a useful method for protein analysis where only scarce amounts of protein are available. This approach can be adapted successfully to label low-level protein isolated from FFPE tissue.