Fluorine-18-deoxyglucose positron emission tomography/computed tomography with Ki67 and GLUT-1 immunohistochemistry for evaluation of the radiosensitization effect of oleanolic acid on C6 rat gliomas

ObjectiveThe aim of this study was to investigate the radiosensitization effect of oleanolic acid (OA) in an in-vivo C6 rat glioma model using fluorine-18-deoxyglucose PET/computed tomography (F-18-FDG PET/CT) and Ki67 and glucose transporter-1 (GLUT-1) immunohistochemistry (IHC) and evaluate the utility of F-18-FDG PET/CT in assessing early changes after radiotherapy.Materials and methodsTumor-bearing rats were divided into four groups: the control group (group A), the OA group (group B), the radiotherapy group (group C), and the OA combined with radiotherapy group (group D). F-18-FDG PET/CT images were obtained to monitor the tumor/muscle (T/M) ratio of F-18-FDG uptake before treatment, 1 day after treatment, and 7 days after treatment. Tumor volume changes were also assessed, and hematoxylin and eosin staining and Ki67 and GLUT-1 IHC staining were also carried out.ResultsBefore treatment, there were no obvious differences between the T/M ratios (F=0.147, P=0.931) and tumor volumes (F=0.177, P=0.911) among the four groups. At day 1 after treatment, statistical differences were observed in the T/M ratios (F=2.891, P=0.05), with decreased values in groups C and D compared with group A (t(CA)=2.354, t(DA)=2.356, P<0.05). At day 7 after treatment, the T/M values of group D were lower than those of the other three groups (t(DC)=2.416, P=0.03; t(DA)=8.133, t(DB)=7.656, P<0.01), and the tumor volumes of group D were significantly decreased compared with group C (t=2.351, P=0.02). There were significant differences in tumor cell densities and in the expression of Ki67 and GLUT-1 in the four groups (F=16.667, 22.082, and 39.555, P<0.001). The T/M ratio showed a significant correlation with the expression of Ki67 and GLUT-1, and our study also found a significant relationship between the expression of Ki67 and the expression of GLUT-1.ConclusionOA has a radiosensitization effect on C6 rat glioma tumors in vivo, detected using F-18-FDG PET/CT and Ki67 and GLUT-1 IHC staining. F-18-FDG PET/CT is a potentially sensitive tool for the evaluation of early changes after radiotherapy.