Identification of Annexin A1 protein expression in human gastric adenocarcinoma using proteomics and tissue microarray.

To study the differential expression of Annexin A1 (ANXA1) protein in human gastric adenocarcinoma. This study was also designed to analyze the relationship between ANXA1 expression and the clinicopathological parameters of gastric carcinoma. Purified gastric adenocarcinoma cells (GAC) and normal gastric epithelial cells (NGEC) were obtained from 15 patients with gastric cancer by laser capture microdissection. All of the peptide specimens were labeled as ¹⁸O/¹⁶O after trypsin digestion. Differential protein expressions were quantitatively identified between GAC and NGEC by nanoliter-reverse-phase liquid chromatography-mass/mass spectrometry (nano-RPLC-MS/MS). The expressions of ANXA1 in GAC and NGEC were verified by western blot analysis. The tissue microarray containing the expressed ANXA1 in 75 pairs of gastric carcinoma and paracarcinoma specimens was detected by immunohistochemistry (IHC). The relationship between ANXA1 expression and clinicopathological parametes of gastric carcinoma was analyzed. A total of 78 differential proteins were identified. Western blotting revealed that ANXA1 expression was significantly upregulated in GAC (2.17/1, P < 0.01). IHC results showed the correlations between ANXA1 protein expression and the clinicopathological parameters, including invasive depth (T stage), lymph node metastasis (N stage), distant metastasis (M stage) and tumour-lymph node metastasis stage (P < 0.01). However, the correlations between ANXA1 protein expression and the remaining clinicopathological parameters, including sex, age, histological differentiation and the size of tumour were not found (P > 0.05). The upregulated ANXA1 expression may be associated with carcinogenesis, progression, invasion and metastasis of GAC. This protein could be considered as a biomarker of clinical prognostic prediction and targeted therapy of GAC.