Mechanism involved in gallium-67 (Ga-67) uptake by human lymphoid cell lines

The gallium-67 (Ga-67) is a radionuclide used for diagnostic imaging. It is known for its ability to accumulate in inflammatory lesions and tumors, especially in lymphomas. The intracellular distribution and the uptake mechanism of Ga-67 remains a subject of discussion. In this work, we studied the mechanism of Ga-67 uptake in 4 human lymphoid cell lines: 38658, Jurkat, DG75 and U715. Our results have pointed out the heterogeneity of Ga-67 uptake among these cell lines. Using flow cytometry analysis, we reported the expression of transferrin-receptor (TfR) in each lymphoid cell line, and found a positive correlation between TfR density and the Ga-67 uptake (r = 0.99) in lymphoid cells. The anti-TfR monoclonal antibody (MoAb) blocked significantly the Ga-67 uptake in all lymphoid cell lines indicating the Ga-67 uptake as a TfR-dependent mechanism. This mechanism has been saturated with different cold gallium concentrations. A total inhibition of Ga-67 uptake was obtained at a 10(-4) M cold gallium concentration. To conclude, we have shown that the Ga-67 uptake is TfR-dependent in lymphoid cells. Thus, the gallium penetrates in lymphoid cells by an active mechanism which can be saturated.