PAUF is overexpressed in pancreatic cancer stem cells and confers chemoresistance

Abstract

Pancreatic ductal adenocarcinoma (PDAC) is one of the most aggressive malignancies. Similar to other tumors, pancreatic cancer stem cells (CSCs) have also been identified, and play an important role in development, maintenance, and metastasis of PDAC. Novel secretory protein of pancreatic adenocarcinoma up-regulated factor (PAUF) has been shown to contribute to cancer progression and metastasis. Because the clinical relationship between PAUF and pancreatic CSCs is largely unknown, we investigated the association between the functional role of PAUF and pancreatic CSCs. CFPAC-1 cancer spheres were cultured under nonadherent conditions with serum free media. PDAC spheres showed an elevated expression of PAUF protein and pluripotent stemness genes (Oct4, Nanog, Stat3, and Sox2). The mRNA expression of PAUF was also upregulated in CD44+CD24+ESA+ pancreatic CSCs. Sphere formation and soft agar assays showed diminished number of spheres and colonies by PAUF knockdown (shPAUF) in CFPAC-1 cells. Expression of stemness genes and CSC surface markers (CD133, c-MET and ALDH1) were also lower in shPAUF CFPAC-1 cells than in normal control cells. MTT assay revealed that PAUF silent (siPAUF) CFPAC-1 cells had lower mRNA expression of multidrug resistant protein 5 (MRP5) and ribonucleotide reductase M2 (RRM2) and were more vulnerable to gemcitabine and 5-FU than negative control cells (p<0.05).

In conclusion, PAUF is a novel human pancreatic CSC-associated protein that may confer chemoresistance by modulating MRP5 and RRM2. Thus, PAUF may constitute a therapeutic target for overcoming drug-resistant pancreatic CSCs.