Protein clusters associated with carcinogenesis, histological differentiation and nodal metastasis in esophageal cancer.

We examined the proteomic background of esophageal cancer. We used laser microdissection to obtain tumor tissues from 72 esophageal squamous cell carcinoma cases and adjacent normal tissues in 57 of these cases. The 2D-DIGE generated quantitative expression profiles with 1730 protein spots. Based on the intensity of the protein spots, unsupervised classification distinguished the tumor tissues from their normal counterparts, and subdivided the tumor tissues according to their histological differentiation. We identified 498 protein spots with altered intensity in the tumor tissues, which protein identification by LC-MS/MS showed to correspond to 217 gene products. We also found 41 protein spots that were associated with nodal metastasis, and identified 33 proteins corresponding to the spots, including cancer-associated proteins such as alpha-actinin 4, hnRNP K, periplakin, squamous cell carcinoma antigen 1 and NudC. The identified cancer-associated proteins have been previously reported to be individually involved in a range of cancer types, and our study observed them collectively in a single type of malignancy, esophageal cancer. As the identified proteins are involved in important biological processes such as cytoskeletal/structural organization, transportation, chaperon, oxidoreduction, transcription and signal transduction, they may function in a coordinate manner in carcinogenesis and tumor progression of esophageal cancer.