Overexpression and oncogenic function of aldo-keto reductase family 1B10 (AKR1B10) in pancreatic carcinoma

Aldo-keto reductase family 1B10 (AKR1B10) exhibits more restricted lipid substrate specificity (including farnesal, geranylgeranial, retinal and carbonyls), and metabolizing these lipid substrates has a crucial role in promoting carcinogenesis. Overexpression of AKR1B10 has been identified in smoking-related carcinomas such as lung cancer. As development of pancreatic cancer is firmly linked to smoking, the aim of the present study was to examine the expression and oncogenic role of AKR1B10 in pancreatic adenocarcinoma. AKR1B10 expression was analyzed in 50 paraffin-embedded clinical pancreatic cancer samples using immunohistochemistry. Oncogenic function of AKR1B10 was examined in pancreatic carcinoma cells in vitro using western blotting and siRNA approaches, mainly on cell apoptosis and protein prenylation including KRAS protein and its downstream signals. Immunohistochemistry analysis revealed that AKR1B10 overexpressed in 70% (35/50) of pancreatic adenocarcinomas and majority of pancreatic intraepithelial neoplasia, but not in adjacent morphologically normal pancreatic tissue. Compared with a normal pancreatic ductal epithelial cell (HPDE6E7), all of the six cultured pancreatic adenocarcinoma cell lines had an overexpression of AKR1B10 using immunoblotting, which correlated with increase of enzyme activity. siRNA-mediated silencing of AKR1B10 expression in pancreatic cancer cells resulted in (1) increased cell apoptosis, (2) increased non-farnesyled HDJ2 protein and (3) decreased membrane-bound prenylated KRAS protein and its downstream signaling molecules including phosphorylated ERK and MEK and membrane-bound E-cadherin. Our findings provide first time evidence that AKR1B10 is a unique enzyme involved in pancreatic carcinogenesis possibly via modulation of cell apoptosis and protein prenylation.