CD44+CD24+ subset of PANC-1 cells exhibits radiation resistance via decreased levels of reactive oxygen species

Emerging evidence has suggested that pancreatic adenocarcinoma is sustained by pancreatic cancer stem cells. The present study aimed to investigate the expression patterns of the pancreatic cancer stem cell surface markers cluster of differentiation CD44 and CD24 in a pancreatic adenocarcinoma cell line, and to investigate the possible mechanisms for their radiation resistance. Flow cytometry was used to analyze the expression patterns of CD44 and CD24 in the pancreatic adenocarcinoma PANC-1 cell line. In addition, a multi-target click model was used to fit cell survival curves and determine the sensitizer enhancement ratio. The apoptosis and cycle distribution of the four cell subsets was determined using flow cytometry, and the level of reactive oxygen species (ROS) was determined using the 2',7'-dichlorofluorescin diacetate probe. The present results identified that the ratios of CD44+ and CD24+ in the sorted PANC-1 cell line were 92.0 and 4.7%, respectively. Prior to radiation, no statistically significant differences were observed among the four groups. Following treatment with 6 MV of X-rays, the rate of apoptosis was decreased in the CD44+CD24+ group compared with other subsets. The percentage of G0/G1 cells was highest in the CD44+CD24+ group compared with the three other groups, which exhibited increased radiosensitivity. In addition, the level of ROS in the CD44+CD24+ group was reduced compared with the other groups. In summary, the results of the present study indicated that CD44+CD24+ exhibited stem cell properties. The lower level of ROS and apoptosis in CD44+CD24+ cells may contribute to their resistance to radiation in pancreatic adenocarcinoma.