Cell cycle dependency of FDG and 67Ga citrate uptake in HeLa S 3 cells

Positron emission tomography using fluorine-18 fluoro-deoxyglucose (FDG PET) is useful for the detection of malignant tumor recurrences and for the evaluation of a therapeutic response to these; including ones found in the lung, colon, head and neck regions. The experimental study demonstrated FDG uptake was higher in faster-growing rather than in slower-growing tumors. These findings show FDG accumulation exhibits cell cycle dependency. However, the precise mechanism remains to be elucidated. In this study, the relationship between FDG uptake and the cell cycle phase in HeLa S 3 cells, as well as how they compare to the conventional tracer 67Ga citrate (Ga) with single photon emission tomography (SPECT) was assessed. Synchronization of HeLa S 3 cells was accomplished via a double thymidine block. The uptake of FDG and Ga was determined after cell cycle synchronization. The glucose transporter was independently evaluated for the level of its Glut 1 glucose transporter membrane protein. FDG uptake in HeLa S 3 cells was significantly higher in the early S phase and G2/M phase compared to the G1 phase. In addition, Ga uptake was higher in the G2/M phase. Immunochemical assays for the Glut 1 transporter showed an increase in membrane expression within S phase cells. It has been concluded that cell cycle dependency is reflected in the uptake of FDG and Ga, seen during PET or SPECT imaging of tumor tissue. These results reveal tumor proliferative activity, and can assist in evaluating a therapeutic response. Furthermore, the increased FDG uptake, in part due to increased membrane expression of the Glut 1 glucose transporter, contributes to this phenomenon. (author)