Objective: Insufficient labeling efficiency and poor retention of radioactivity are the considerable shortcomings of fluorine-18-fluorodeoxyglucose (¹⁸F-FDG) labeling in human leukocytes. This study was conducted to evaluate the feasibility of using granulocyte colony-stimulating factor (G-CSF) to improve ¹⁸F-FDG labeling in human leukocytes.
Methods: Leukocyte separation was performed using methods reported earlier. Separated leukocytes were preincubated with G-CSF or insulin at 37°C for 1 h. After preincubation, labeling was performed with ¹⁸F-FDG (37-74 MBq) at 37°C for 30 min. Retained radioactivity was assessed at 1-4 h after labeling by the same method described in earlier reports. The viability of labeled leukocytes was assessed by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide assay.
Results: Labeling efficiency of leukocytes preincubated with G-CSF, G-CSF with insulin, insulin, and control leukocytes was 52.1±8.9%, 49.9±10.5%, 40.3±7.7%, and 40.3±6.0%, respectively. G-CSF significantly increased the labeling efficiency compared with insulin (P=0.005) and control (P=0.004). In leukocytes preincubated with G-CSF, 77.0±1.2%, and 59.0±1.8% of radioactivity was retained at 1 and 3 h after labeling. There was no significant difference in retained radioactivity compared with that of leukocytes with different treatment at all time points. Furthermore, no significant difference in viabilities among leukocytes with different treatments was observed.
Conclusion: Use of G-CSF significantly improved ¹⁸F-FDG labeling efficiency without a significant effect on cell viability and retention of radioactivity.