Identification of transgelin as a potential novel biomarker for gastric adenocarcinoma based on proteomics technology

Abstract

Purpose: To find a biomarker for gastric adenocarcinomas (GA).

Methods: Ten protein expression profiles of GA and paired non-neoplastic mucosa tissues were analyzed by two-dimensional gel electrophoresis. Forty-two protein spots that were differentially expressed by twofold or greater between cancer and normal mucosa tissue were excised and identified by MALDI-TOF/TOF MS. One of the over-expressed proteins identified in GA was transgelin, which was chosen for further verification by immunohistochemistry and western blotting.

Results: Forty-two distinct proteins that were differentially expressed at least twofold between the tissues were identified. Expression of 29 of these proteins was decreased (ratio >or= 2, P < 0.01), including adenosine deaminase; and 13 proteins displayed over-expression in cancer tissue (ratio >or= 2, P < 0.01), including transgelin. The results of immunohistochemistry confirmed that transgelin was indeed over-expressed in 22 cases of GA (22/41, 53.66%), with strong cytoplasmic staining in cancer cells of positive samples, this was absent in most paired non-neoplastic mucosa cells or gastric ulcer tissues (n = 20). Transgelin was found over-expressed in 21 samples of cancer tissue (21/41, 51.22%) when detected by western blot.

Conclusion: This work demonstrates that differentially expressed proteins can be identified by proteomics technology combined with immunohistochemistry and western blot analyses. We have identified one such protein, transgelin, as a novel biomarker for GA.

Fig. 1

Representative protein expression patterns of gastric adenocarcinoma tissues and paired non-neoplastic mucosa analyzed by two-dimensional electrophoresis. a Paired non-neoplastic mucosa; b gastric adenocarcinoma tissue. Transgelin was over-expressed in GA tissues (b, highlighted ellipse) compared to non-neoplastic mucosa (a). The spot was identified by MALDI-TOF/TOF MS, yielding a molecular weight for transgelin consistent with expectations

Fig. 2

Western blot analysis of transgelin expression. Over-expression of transgelin in GA tissue (Ca) compared to paired non-neoplastic tissue (N) was confirmed by western blotting. Equal amounts of protein from each sample were probed with anti-β-tubulin as a loading control. The signal Intensity was measured by ImageQuant TL v2003.03 analysis software, the relative intensity (RI) of transgelin, which was normalized to β-tubulin, and the ratios of RI of GA versus paired non-neoplastic tissue were indicated at the bottom

Fig. 3

Immunohistochemical analysis of transgelin expression in gastric adenocarcinoma. Transgelin displayed positive cytoplasmic staining in GA that was stronger than non-neoplastic tissue. The expression of transgelin in normal stomach (a, b), GA (c, d), and gastric ulcer (e–h); e, f the cells adjacent to the surface of ulcer. g, h cells from distal normal tissue of the same sample. Images on the left panel were made under ×100 magnification (e is ×40); the images on the right are magnified images (×400) of the boxed sections depicted at left