Identification of the Aberrantly-Expressed Proteins in Human Gastric Cancer by Itraq

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. Many 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 for clinical significance. 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 has been accepted and will be published in Annal of Oncology. The aim of this project 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 via quantitative proteomic approach. Furthermore, the latter may be more representative in vivo status than the former. In the past one year, we had collected surgical samples, and used laser-capture-microdissection to separate tumor from normal tissues and had analyzed differentially expressed proteins by the quantitative proteomic approach. The potential biomarkers will be selected to study the clinical significance. In the coming two years by this new project, we will continue to analyze these proteins by quantitative-RT-PCR, or immunohistochemisty and their clinicopathological correlations. Subsequently, the functional characterization, including adenovirus transfection, flow cytometry, and tumorigenesis study in nude mice, of the candidate proteins, which were identified previously. Thereby, the newly identified proteins can be useful in establishing early diagnosis, prognostic factors, and developing novel therapeutic targets in the future. This 2-year project actually follows the preceding project (NSC 99-2314-B-182 -022), where only one-year budget was granted, because NSC supposed that I would have retired in 2011. However, in this July I was honored by our hospital as ‘consultant’ physician, privileging to conduct medical practice or any research work without a term limitation. Therefore, I hope to continue and complete my aims through this new project.

Project ID:PC10007-0390 
External Project ID:NSC100-2314-B182-011