Gallium-67 citrate uptake by cultured tumor cells, stimulated by serum transferrin

The uptake of the tumor scanning agent 67-Ga citrate by cultured mouse tumor cells wqs greatly enhanced with small additons of certain sera to the culture medium. This stimulation of uptake was due to a macromolecular serum component, provisionally identified with transferrin. The response under optimum conditions was so great as to suggest that the 67-Ga uptake process depends entirely on the action of transferrin. The same mechanism probably operates in vivo and may help explain interesting features of the tracer's tissue distribution, particularly its tumor affinity.