Proteomic analysis of SEG-1 human Barrett's-associated esophageal adenocarcinoma cells treated with keyhole limpet hemocyanin.

Keyhole limpet hemocyanin (KLH) is an immune stimulant derived from a circulating glycoprotein of the marine mollusk Megathura crenulata. We previously reported that KLH inhibited the growth of human Barrett's-associated esophageal adenocarcinoma in vitro via apoptotic and nonapoptotic mechanisms. We hypothesize that KLH reduces the growth of Barrett's cancer cells by altering protein expression profiles. A cell line (SEG-1) derived from Barrett's-associated adenocarcinomas of the distal esophagus was selected. Cells were administered KLH (500 microg/ml) or vehicle. After 24 hours, cytosolic fractions were separated through two-dimensional gel electrophoresis. Statistical analysis was performed with Evolution Pro software to identify spots that were differentially expressed between the KLH and control groups. Proteins displaying a twofold or greater change in expression levels were selected for identification. In a total of 420 spots, 31 were differentially expressed between the KLH and control groups. In all, 12 were upregulated and 19 were downregulated. Of the 31, 17 were identified by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry. Proteomic evaluation shows downregulation of proteins associated with metabolic processes (glycolysis, protein synthesis). KLH also induced proteins indicative of oxidative stress (heat shock 70 family and UDP-glucose 6-dydrogenase). Our results indicate that growth arrest by KLH is accompanied by a cellular stress response and attenuation of metabolic processes. The use of KLH as adjuvant or topical therapy for Barrett's adenocarcinoma provides a promising development in the treatment of this disease.