18F-FDG PET/CT in evaluating the radiosensitizing effect of oleanolic acid / 中华核医学与分子影像杂志

ABSTRACT

Objective To evaluate the feasibility of 18F-FDG PET/CT in assessing the radiosensitizing effect of oleanolic acid (OA) in C6 rat glioma model,and to explore the possible mechanism of radiosensitizing effect of OA.Methods Thirty-two C6 glioma-bearing SD rats were divided into 4 groups by random number tablegroup A without OA and radiotherapy,group B with OA alone,group C with radiotherapy alone,group D with OA and radiotherapy.18F-FDG PET/CT was performed before radiotherapy,at 24 h and 7 d after radiotherapy.The tumor SUVmax was measured.All rats were sacrificed and tumor tissues were excised for HE and immunohistochemistry staining.Paired t test,one-way analysis of variance,LSD-t test and Spearman correlation analysis were performed to analyze the data using SPSS 13.0.Results There was no statistically significant difference in SUVmax among the 4 groups (SUVmax of groups A,B,C,D5.252± 0.536,5.261±0.544,5.273±0.520,5.232±0.507) before treatment (F=0.008,P＞0.05).At 24 h postradiotherapy,SUVmax of groups C and D (4.766±0.511 and 4.403 ±0.486) decreased significantly (t =14..788,13.366,both P＜0.05);while groups A and B (5.680±0.635 and 5.763±0.689) increased significantly (t =-11.578,-8.651,both P＜0.05;F=10.550,P＜0.05).However,there was no statistically significant difference between groups C and D (t =1.453,P＞0.05).At 7 d post-radiotherapy,SUVmax of groups C and D decreased significantly (t =9.750,10.530,both P＜0.05);while SUVmax of groups A and B (t=-35.353,-6.884,both P＜0.05) increased significantly (F=97.691,P＞0.05).SUVmax of Group D decreased significantly compared with that of group C (t =5.329,P＞0.05).Less tumor cells and more areas of necrosis were observed in group D compared with those in other groups by HE staining.The expression of HIF-1α was lower in group D than that in other groups by immunohistochemistry staining.HIF-1α expression was positively correlated with SUVmax(r=0.853,P＜0.05).Conclusion 18F-FDG PET/CT has potential to evaluate the radiosensitizing effect of OA in vivo,and the radiosensitization of OA might be related to the down regulation of HIF-1α.