Identification of the Aberrantly-Expressed Proteins in Human Gastric Cancer by iTRAQ Labeling-Based Quantitative Proteomics Approach and Study Their Clinical Significance

The identification of a novel biomarker presents a new approach for early diagnosis and chance of cure for gastric cancer. We hope to find novel biomarkers of the diseases by means of differential expression analysis. Previously, we have identified many genes that aberrantly expressed in gastric cancer tissues by means of cDNA microarray analysis. Some of them had been verified by Northern blot analysis, quantitative-RT-PCR, and immunohistochemisty. Three of highly upregulated genes: SPARC (osteonectins), SLPI (secretory leukocyte protease inhibitor), and Gro1 (Growth-related oncogene) have been studied. we demonstrated that the 3 genes were over expressed in gastric cancer patients and were significantly correlated with more advanced disease, and worse survival outcome. The article of our SPARC and SLPL data have been published and that of Gro1 was submitted for publication. The aim of this study is to identify novel putative diagnostic or prognostic markers using iTRAQ labeling-based protein identification and quantification approach with off-line basic reverse phase HPLC (bRP-HPLC) by Thermo LTQ-orbitrapTM mass spectrometer systems. The differential expression profile from cDNA microarray could be different from that of from proteomic approach. Furthermore, the latter may be more representative in vivo status than the former. In the first year, we will collect surgical samples, and use laser-capture-microdissection to separate tumor or normal tissues and will analyze differentially expressed proteins by the quantitative proteomic approach. The clinical significance or the potential biomarkers will be selected. In the second to third year of this study, we will analyze the expression of these proteins by quantitative-RT-PCR, or immunohistochemisty and their clinicopathological significance. Subsequently, the functional characterization, including adenovirus transfection, flow cytometry, and tumorigenesis study in nude mice, of the candidate proteins, which are identified in the first year. Thereby, the newly identified proteins can be used for establishing early diagnosis, prognostic factors, and developing novel therapeutic targets in the future.

Project ID:PC9908-0469
External Project ID:NSC99-2314-B182-022