Proteomics in clinical laboratory diagnosis

Mass spectrometry based targeted protein quantification: methods and applications

The recent advance in technology for mass spectrometry-based targeted protein quantification has opened new avenues for a broad range of proteomic applications in clinical research. The major breakthroughs are highlighted by the capability of using a "universal" approach to perform quantitative assays for a wide spectrum of proteins with minimum restrictions and the ease of assembling multiplex detections in a single measurement. The quantitative approach relies on the use of synthetic stable isotope labeled peptides or proteins, which precisely mimic their endogenous counterparts and act as internal standards to quantify the corresponding candidate proteins. This report reviews recently developed platform technologies for emerging applications of clinical proteomics and biomarker development.

Plasma proteomic analysis of patients with squamous cell carcinoma of the uterine cervix

OBJECTIVE

To compare plasma protein expression between patients with squamous cell carcinoma (SCC) of the cervix and normal controls.

METHODS

Plasma samples from patients with benign gynecological disease (normal cervix, n=6) and cervical cancer (SCC, n=6) were subjected to plasma proteomic analysis using two dimensional gel electrophoresis (2-DE) and matrix-assisted laser desorption/ionization mass spectroscopy (MALDI-MS). Western blotting and immunoturbidimetric assay were performed to validate the results of 2-DE.

RESULTS

Eight proteins showed differential expression between controls and SCC patients; six (ceruloplasmin, complement C3, afamin precursor, alpha-1-B-glycoprotein, transferrin, alpha-fibrinogen precursor) were up-regulated, while two (chain A, crystal structure of antithrombin and apolipoprotein A-IV precursor) were down-regulated in the plasma of SCC patients. Western blotting analysis revealed significant elevation of ceruloplasmin, complement C3, afamin, and alpha-1-B-glycoprotein in the plasma of SCC patients in comparison to controls. Immunoturbidimetric assay of a larger group confirmed the results of 2-DE and Western blotting, and showed that ceruloplasmin and complement C3 were significantly elevated in the plasma of SCC patients in comparison with controls and patients with carcinoma in situ (CIS) of the uterine cervix.

CONCLUSION

Plasma protein expression determined using 2-DE and MALDI-MS will give a chance to identify tumor-specific biomarkers for SCC of the cervix.

Comparison of proteomes in various human plasma preparations by two-dimensional gel electrophoresis

Serum or plasma can be utilized in a variety of studies targeted toward the discovery of disease biomarkers. In this study, the proteome profiles of plasma samples prepared using various anticoagulants (EDTA, heparin or citrate), were compared with those of serum using two-dimensional electrophoresis (2-DE). Proteins which evidenced different levels in the plasma and serum were screened and identified using ESI-Q-TOF MS/MS. The proteins which became detectable after the removal of fibrinogen from serum were identified as pigment epithelial differentiating factor (four spots), fetuin-like protein, and the hemopexin precursor. In particular, three proteins, pre-serum amyloid P component, plasma glutathione peroxidase precursor, and tetranectin, evidenced increased volume intensity only in the plasma samples prepared with EDTA.