Increased PDX-1 expression is associated with outcome in patients with pancreatic cancer

Background. During pancreatic development, pancreatic duodenal homeobox gene-1 (PDX-1) is expressed in pancreatic duct cells that have the potential to differentiate into islets. Therefore, PDX-1 is thought to be a marker of de-diffffentiated cells with the capacity to redifferentiate into several pancreatic cell types. We analyzed PDX-1 expression in human pancreatic cancer specimens, pancreatic cancer cell lines, and the affects of forced expression of PDX-1 in pancreatic cancer cells. Methods. Thirty-five pancreatic adenocarcinomas were immunohistochemically stained with a polyclonal rabbit antibody against mouse PDX-1. Correlations with tumor characteristics were made with chi-squared analysis. The influence of clinicopathologic factors on survival was assessed. The expression of PDX-1 in pancreatic cancer cells was examined. Replication-deficient recombinant adenoviruses were constructed by the cosmid-adenoviral DNA terminal protein complex method. PANG-1 cells were infected with Ad-pdx-1 or Ad-LacZ. PANC-1 cells that were infected with adenovirus were used in a cell growth assay and a migration assay and for morphologic analysis. Results. Interestingly, 43% of pancreatic cancers were positive for PDX-1 expression, and 57% of pancreatic cancers were negative (normal pancreatic exocrine tissue shows little or no staining for PDX-1). Lymph node metastasis (P = .02) and histologic grade (P = .04) were correlated significantly with PDX-1 expression. Patients with positive PDX-1 had a significantly worse prognosis than those patients with negative PDX-1 (P =. 02). Importantly, PDX-1 was an independent variable that effected overall survival (P = .03). Pancreatic cancer cell lines showed no PDX-1 expression. There were no significant differences in cell proliferation or morphologic condition between Ad-pdx-1- and Ad-lacZ-infected PANC-1 cells. However, Ad-pdx-1-infected PANC-1 cells did show a significantly higher migration rate than Ad-lacZ-infected PANC-1 cells. Conclusion. Re-expression of PDX-1 may represent a return to a more de-differentiated state by more aggressive pancreatic cancers and may also represent an important new tumor marker for these aggressive cancers.