BACKGROUND: Emerging evidence suggests that pancreatic adenocarcinoma is hierarchically organized and sustained by pancreatic cancer stem cells. Furthermore, elimination of these cells is possible and therapeutically relevant. This study aimed to investigate the expression patterns of pancreatic cancer stem cell surface markers CD44, CD24 and ESA in pancreatic adenocarcinoma cell lines and explore the influence of their local microenvironment.
METHODS: Flow cytometry was used to analyze the expression patterns of CD44, CD24 and ESA in five pancreatic adenocarcinoma cell lines (PANC-1, PC-2, MIA-Paca-2, AsPC-1 and BxPC-3). In addition, the capacity for sphere-formation in serum-free medium of four cell lines (PANC-1, PC-2, MIA-Paca-2 and BxPC-3) was assessed. Then, the same assays were performed when tumor cell spheres were developed. The role of sonic hedgehog (SHH) in cell spheres from PANC-1 and MIA-Paca-2 were also assessed by RT-PCR.
RESULTS: CD44 and CD24 were detected in PANC-1. Only CD44 expression was detected in PC-2, MIA-Paca-2 and AsPC-1. CD44, CD24 and ESA were all detected in BxPC-3. Tumor cell spheres developed in PANC-1 and MIA-Paca-2 in serum-free medium. This was accompanied by an increase in CD24 expression and a decrease in CD44 expression in PANC-1. Interestingly, the expression of CD44 and CD24 returned to initial levels once the medium was changed back from serum-free to serum-containing medium. No significant change in the expression of CD44 was detected in MIA-Paca-2. Furthermore, the relative quantification of SHH mRNA in PANC-1 cell spheres was significantly higher than that in cells cultured in the serum-containing medium.
CONCLUSION: The expression patterns of the pancreatic cancer stem cell surface markers CD44, CD24 and ESA were diverse in different pancreatic adenocarcinoma cell lines and changed with their local microenvironment.