Over-Expression of Alpha-Enolase as a Prognostic Biomarker in Patients with Pancreatic Cancer

Background: Alpha-enolase is an important glycolytic enzyme, and its aberrant expression has been associated with multiple tumor progression. However, few studies investigated the expression of alpha-enolase and its clinical significance in pancreatic cancer (PC). Objectives: To evaluate alpha-enolase level in PC tissues by immunohistochemical (IHC) analysis, and investigate the association of alpha-enolase expression with clinicopathologic features. Methods: The alpha-enolase levels in pancreatic cancer tissues were analyzed by using the Oncomine database. The expression of alpha-enolase, Ki67 and p53 in pancreatic cancer and adjacent normal tissues were evaluated by IHC using the corresponding primary antibodies on the commercial tissue arrays. We also examined their association with clinicopathologic parameters, and explored their prognostic value in PC. Results: We identified an elevation of alpha-enolase mRNA level in pancreatic cancer independent datasets from Oncomine. IHC analysis showed that alpha-enolase protein levels were elevated in 47% (n=100) PC tissue samples, but there was weak or no staining in the normal tissues. Statistical analysis revealed that high levels of alpha-enolase were significantly associated with Stage and Lymph node metastasis. Correlation analysis indicated that over-expression of alpha-enolase was positively associated with Ki67 expression and inversely correlated with p53 expression. Furthermore, membranous expression of alpha-enolase was also observed in 29.8% (14/47) total alpha-enolase positive samples, and was significantly associated with Lymph node metastasis. Kaplan-Meier survival analysis demonstrated that high total alpha-enolase expression was significantly associated with unfavorable survival, while membranous alpha-enolase expression was significantly associated with better survival of PC patients. Multivariate Cox analysis demonstrated that total alpha-enolase expression was an independent prognostic factor for PC patients. Conclusions: Our results suggested that alpha-enolase level was significantly elevated in pancreatic cancer tissues, which was closely associated with PC progression. It might be a candidate target for targeted pancreatic cancer treatments.