Proteomic profiling of autoantibodies in patients with esophageal squamous cell carcinoma

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To identify proteins associated with esophageal carcinogenesis, we performed protein profiling of 16 esophageal squamous cell carcinomas (ESCCs) and paired non-cancerous tissues by two-dimensional electrophoresis (2-DE) and tandem mass spectrometry. In cancerous tissues, three spots showed significant up-regulation in the amount of protein, while eight spots were significantly down-regulated. The identities of the spots were determined by peptide mass fingerprinting (PMF) with liquid chromatography-mass spectrometry/mass spectrometry (LC-MS/MS) and were confirmed by immunoblotting. The up-regulated proteins were tropomyosin alpha 4 chain, transgelin, and pyruvate kinase. The down-regulated proteins were serum albumin precursor, isoforms of annexin Al, tropomyosin beta chain, 14-3-3 protein sigma and isoforms of serotransferrin precursor. In all 16 cases, up-regulation of the tropomyosin alpha 4 chain was confirmed by immunoblotting. Localization of the tropomyosin alpha 4 chain in ESCC cells and adjacent fibroblasts was confirmed by immunohistochemistry.