Abstract

In this study, we first sought to determinethe existence of side population (SP) cells in pancreatic cancer cell lines.Furthermore, we compared the biological characteristics of SP and non-SP cells.The presence of side population cells in pancreatic cancer cell lines wasdetected by Hoechst 33342 staining and FACS analysis. Cell cycle distributionwas analyzed using flow cytometry. SP and non-SP cells were exposed to variousconcentrations of gemcitabine; drug sensitivity was examined using the MTTassay and flow cytometry using Annexin-V and PI staining. To compare thetumorigenic ability in vivo, groups of nude mice were orthotopically inoculatedwith varying numbers of SP and non-SP cells. The percentages of CD44+CD24+ andCD133+ in SP and non-SP cells were also detected by FACS analysis. The SPfraction was detected in BxPc-3, CFPAC-1, MIA PaCa-2, PANC-1 and SW1990pancreatic cancer cell lines. Cell cycle analysis revealed that the SP cellscontained more cells in the G1 phase and fewer cells in the S phase whencompared with the non-SP cells. The SP cells exhibited increased tumorigeneticability following in vivo transplantation into BALB/C nude mice and increasedchemoresistance following in vitro exposure to gemcitabine. FACS analysisshowed that the SP cells contained more CD44+CD24+ and CD133+ cells than thenon-SP cells. In conclusion, these observations suggest that SP cells in thepancreatic cancer cell lines possess the property of cancer stem cells. SPcells may therefore be novel specific targets for the effective treatment ofpancreatic cancer.