Cellular targeting and subcellular distribution of HER-2 targeting boron liposomes

Objective: To investigate HER-2 targeting boron liposomes as a potential drug delivery vehicle for boron neutron capture therapy, in respect to cellular uptake, retention and the subcellular location. Methods: Cellular uptake and retention of 125I-Trastuzumab-WSA-3H-Liposomes were studied using SK-BR-3 cells, with regard to the targeting agent, carriers, and the loaded WSA. As there was 125I labeled on Trastuzumab and 3H on liposomes, Trastuzumab and the liposomes could be measured using a gamma counter and a liquid scintillation counter, respectively. WSA could be measured by inductively coupled plasma mass spectrometry (ICP-MS). Subcellular distribution of WAS was studied using confocal microscopy. Results: The uptake of 125I labeled Trastuzumab reached a plateau after 8 h and declined after 24 h incubation. For 3H-Liposome, there was a different uptake pattern, i. e., no plateau was reached and no decline was seen even after 48 h incubation. The boron uptake increased with prolongation of incubation time, for 4, 8 and 24 hours' incubation, it reached 55 ppm, 78 ppm, and 123 ppm, respectively. After incubation in conventional medium for 24 h over 90% WSA and 70% of the 3H-Liposomes still remained in the cells, while only 35% of the 125I-Trastuzumab remained. The difference was even more pronounced after 48 h when 67% WSA and 55% of the 3H-Liposome still remained in the cells as compared to 18% for the 125I-Trastuzumab. WSA was clearly visualized within the cell mainly in the cytoplasm. Conclusion: The developed HER-2 targeting boron liposomes could be considered as a potent drug delivery system for boron neutron capture therapy, since it has high cellular boron uptake with a long retention time. (authors)