Proteomic analysis of gastric cancer and immunoblot validation of potential biomarkers.

To search for and validate differentially expressed proteins in patients with gastric adenocarcinoma. We used two-dimensional gel electrophoresis and mass spectrometry to search for differentially expressed proteins in patients with gastric adenocarcinoma. A set of proteins was validated with immunoblotting. We identified 30 different proteins involved in various biological processes: metabolism, development, death, response to stress, cell cycle, cell communication, transport, and cell motility. Eight proteins were chosen for further validation by immunoblotting. Our results show that gastrokine-1, 39S ribosomal protein L12 (mitochondrial precursor), plasma cell-induced resident endoplasmic reticulum protein, and glutathione S-transferase mu 3 were significantly underexpressed in gastric adenocarcinoma relative to adjacent non-tumor tissue samples. On the other hand, septin-2, ubiquitin-conjugating enzyme E2 N, and transaldolase were significantly overexpressed. Translationally controlled tumor protein was shown to be differentially expressed only in patients with cancer of the gastric cardia/esophageal border. This work presents a set of possible diagnostic biomarkers, validated for the first time. It might contribute to the efforts of understanding gastric cancer carcinogenesis.