Expression and clinical significance of apolipoprotein E in pancreatic ductal adenocarcinoma

Pancreatic ductal adenocarcinoma (PDAC) is a lethal cancer with a poor prognosis. Our previous proteomic analysis found apolipoprotein E (ApoE) protein to be up-regulated in the sera of patients with PDAC. In this study, we sought to confirm this finding and investigate the relationship between ApoE and PDAC. We measured ApoE expression in tissues from PDAC patients and normal controls (NC) by real-time PCR, western blot, and immunohistochemistry. Enzyme-linked immunosorbent assay (ELISA) was applied to measure the levels of ApoE and carbohydrate antigen 19-9 (CA19-9) in the sera from patients with PDAC and NC. Real-time PCR and western blots showed that the ApoE mRNA and protein levels were up-regulated in PDAC tissues. The immunohistochemical results revealed that overexpression of ApoE was detected in 43 of 55 (78.2 %) PDAC cases and 3 of 20 (15 %) NC. High levels of ApoE were more likely in PDAC patients with advanced T status and TNM stages (p = 0.023 and p = 0.018, respectively). The ELISA results also confirmed that ApoE levels were elevated in the sera of PDAC patients. The sensitivity and specificity for distinguishing PDAC from NC were 76.2 and 71.4 %, respectively, for ApoE, 66.7 and 85.7 %, respectively, for CA19-9, and 81.0 and 85.7 %, respectively, for their combination. These results suggest that ApoE may be a potential PDAC-related biomarker and alone or in combination with other markers may provide additional information for the diagnosis and clinical management of PDAC.