Gallbladder cancer is the most common malignant tumor of the biliary tract. Early diagnosis of gallbladder cancer is difficult because of the latent onset and lack of good biomarkers. To identify new biomarkers that improve the early diagnosis and/or serve as possible therapeutic targets in gallbladder cancer is essential. In the present study, serum proteins were separated by two-dimensional gel electrophoresis (2-DE) in 3 patients with gallbladder cancer and 3 healthy volunteers. The differentially expressed spots were identified by matrix-assisted laser desorption ionization time-of-flight mass spectrometry (MALDI-TOF-MS). Western blotting and immunohistochemistry were performed to verify the expression of certain candidate proteins. Protein expression and clinical correlation was evaluated. We found that 64 protein spots were significantly changed in gallbladder cancer. Twenty-four proteins including S100A10, haptoglobin, cystatin-B, profilin-1 and superoxide dismutase were successfully identified. Among these proteins, S100A10 and haptoglobin were validated using Western blotting. Immunohistochemically, the expression of S100A10 and haptoglobin proteins was found to be higher in gallbladder cancer tissues compared to that in gallbladder adenoma, liver cholangiocarcinoma and cholecystitis tissue. Patients with high expression of S100A10 and haptoglobin were linked to late stage disease and poor clinical prognosis. Our data suggest that combined comparative proteomic analysis by 2-DE and MALDI-TOF-MS is an effective method for identifying differentially expressed proteins in serum samples. These proteomic approaches could be used for identifying new serum biomarkers in gallbladder cancer. S100A10, haptoglobin and other identified proteins may be potential molecular targets for early gallbladder cancer diagnostics and therapeutic applications.

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