Recent advances in two-dimensional electrophoresis (2-DE) such as fluorescent 2-D differential gel electrophoresis (2-D DIGE) has made it possible to detect and quantitate the critical changes involved in disease pathogenesis. We have previously identified novel
proteins with altered expression in primary
colorectal cancer using
agarose 2-DE that has a higher loading capacity than immobilized pH gradient gel. The aim of this study is to identify novel
proteins with altered expression in primary
esophageal cancer using the powerful method of
agarose 2-DE and
agarose 2-D DIGE. Excised tissues from 12 patients of primary
esophageal cancer were obtained.
Proteins with altered expression between
cancer and adjacent non-
cancer tissues were analyzed by
agarose 2-D DIGE and identified by mass spectrometry. Thirty-three
proteins out of 74 spots with altered expression in
tumors were identified. Among them, a 195-kDa
protein, periplakin, was significantly downregulated in
esophageal cancer, which was confirmed by immunoblotting. Immunohistochemistry showed that periplakin was mainly localized at cell-cell boundaries in normal epithelium and dysplastic lesions, while it disappeared from cell boundaries, shifted to cytoplasm, in early
cancers and scarcely expressed in advanced
cancers. These results suggest that periplakin could be a useful marker for detection of early
esophageal cancer and evaluation of
tumor progression.