Comparative DIGE Proteomics

Gel-based proteomics has been widely used for the systematic cataloging of the protein constituents of defined biofluids, purified organelles, individual cell types, heterogeneous tissues and isolated organs, as well as being applied to comparative biochemical and biomedical analyses of complex biological specimens. Of the many electrophoretic techniques used in modern biochemical approaches, large-scale protein separation by difference gel electrophoresis (DIGE) has established itself as the most powerful analytical tool in comparative proteomics. Both 2-dye and 3-dye fluorescence systems with minimal or saturation labeling are routinely used. This chapter briefly describes the technical advantages of the pre-electrophoretic fluorescent labeling technique and discusses the bioanalytical usefulness of this highly successful electrophoretic method.

Stage-specific analysis of plasma protein profiles in ovarian cancer: Difference in-gel electrophoresis analysis of pooled clinical samples

INTRODUCTION

Ovarian cancer is the leading cause of death from gynecological cancer. Non-specific symptoms early in disease and the lack of specific biomarkers hinder early diagnosis. Multi-marker blood screening tests have shown promise for improving identification of early stage disease; however, available tests lack sensitivity, and specificity.

MATERIALS AND METHODS

In this study, pooled deeply-depleted plasma from women with Stage 1, 2 or 3 ovarian cancer and healthy controls were used to compare the 2-dimensional gel electrophoresis (2-DE) protein profiles and identify potential novel markers of ovarian cancer progression.

RESULTS/DISCUSSION

Stage-specific variation in biomarker expression was observed. For example, apolipoprotein A1 expression is relatively low in control and Stage 1, but shows a substantial increase in Stage 2 and 3, thus, potential of utility for disease confirmation rather than early detection. A better marker for early stage disease was tropomyosin 4 (TPM4). The expression of TPM4 increased by 2-fold in Stage 2 before returning to "normal" levels in Stage 3 disease. Multiple isoforms were also identified for some proteins and in some cases, displayed stage-specific expression. An interesting example was fibrinogen alpha, for which 8 isoforms were identified. Four displayed a moderate increase at Stage 1 and a substantial increase for Stages 2 and 3 while the other 4 showed only moderate increases.

CONCLUSION

Herein is provided an improved summary of blood protein profiles for women with ovarian cancer stratified by stage.