Preloading with L-tyrosine increases the uptake of boronophenylalanine in mouse melanoma cells.

To improve the effectiveness of boron neutron capture therapy, the possibility of stimulating boron uptake was investigated in an experimental model. B16F1 mouse melanoma cells were exposed to boronophenylalanine (BPA). The intracellular boron concentration followed Michaelis-Menten kinetics in the early incubation phase. In the late phase, cellular boron concentration was linearly related to the BPA concentration in the culture medium. Incubation with L-tyrosine before exposure to BPA (preloading) increased the intracellular boron concentration by a factor of three. It is concluded that in B16F1 cells BPA is transported by L and presumably ASC (alanine, serine, and cysteine) transport systems, and that boron uptake can be effectively stimulated by L-tyrosine preloading.