Identification of tumor markers using two-dimensional electrophoresis in gastric carcinoma

To study the differential expression of proteins in normal and cancerous gastric tissues, and further identify new molecular markers for diagnosis and prognosis of gastric carcinoma, as well as develop new therapeutic targets of the disease.

Matched pairs of tissues from 6 gastric cancer patients were analyzed for their two-dimensional electrophoresis (2DE) profiles. Soluble fraction proteins from human normal and cancerous gastric tissue were separated in the first dimension by isoelectric focusing on immobilized pH gradient (IPG, pH3-10) strips, and by 125 g/L sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) in the second dimension with silver nitrate staining. Protein differential expression was analyzed by use of image analysis software to find out candidates for gastric cancer-associated proteins.

Nine protein spots overexpressed in tumor tissues as compared with noncancerous regions. In the next step, 9 tumor-specific spots were cut off from Coomassie Brilliant Blue staining gels, digested in gel with L-1-tosylamide-2-phenylethyl chloromethyl ketone (TPCK)-trypsin. Protein identification was done by peptide mass fingerprinting with matrix assisted laser desorption/ionization-time of flight-mass spectrometry (MALDI-TOF-MS). In total, 5 tumor-specific protein spots corresponding to 5 different polypeptide chains were identified, including annexin V, carbonic anhydrase, prohibitin, fibrin beta and fibrinogen fragment D. Among these 5 spots, the potential significance of the differential expressions is discussed. CONCLUSION Differential expression analysis of proteomes may be useful for the development of new molecular markers for diagnosis and prognosis of gastric carcinoma.