RESUMO
Objective:To explore the application potential of 18F-Asp-Glu-val-Asp (DEVD)-Cys(StBu)-PPG(CBT)-AmBF 3 ( 18F-1; PPG: propargyl-glycine; CBT: 2-cyanobenzothiazole; AmBF 3: ammoniomethyl-trifluoroborate) PET imaging in early monitoring of triple-negative breast cancer (TNBC) radiotherapy response. Methods:Ten MDA-MB-231 tumor bearing nude mice models were constructed and divided into radiotherapy group ( n=5) and non-radiotherapy group ( n=5) by random sampling method. The radiotherapy group was treated with single irradiation at a dose of 8 Gy. 18F-1 microPET imaging was performed in the radiotherapy and non-radiotherapy groups, and the tumor uptake and muscle uptake in 2 groups at different time points (2.5, 7.5, 12.5, 17.5, 22.5, 27.5, 32.5, 37.5, 42.5, 47.5, 52.5, 57.5 min after injection) were analyzed. The specific uptake of the probe in apoptotic cells was verified by radioautography, HE staining and immunofluorescent staining. Repeated measures analysis of variance and one-way analysis of variance were used to analyze data. Results:18F-1 microPET imaging showed that there was significant difference between tumor uptake and muscle uptake in radiotherapy group ( F=20.27, P=0.011). The uptake of radiotherapy group was the highest at 7.5 min after injection ((4.64±0.35) percentage activity of injection dose per gram of tissue(%ID/g)). There was no significant difference between tumor uptake and muscle uptake in the non-radiotherapy group ( F=1.81, P=0.215). The tumor/muscle (T/M) ratio of radiotherapy group was higher than that of non-radiotherapy group ( F=31.95, P=0.005), with the highest at 47.5 min after injection (2.49±0.46). Radioautography showed that the tumor radioactivity in radiotherapy group was higher than that of muscle in radiotherapy group, and was also higher than tumor and muscle radioactivies in non-radiotherapy group ( F=116.79, P<0.001). HE staining and immunofluorescent staining verified that 18F-1 could specifically detect the activity of caspase-3 activated in tumor cells after radiotherapy. Conclusion:18F-1 can specifically recognize the activated caspase-3 after TNBC radiotherapy, and monitor radiotherapy response at the molecular level by apoptosis PET imaging.