EGF-receptor targeted liposomes with boronated acridine: growth inhibition of cultured glioma cells after neutron irradiation.

PURPOSE: To study survival of cultured U-343MGaCl 2:6 glioma cells after incubation with boron-containing liposomes targeting the epidermal growth factor receptor following neutron irradiation. MATERIALS AND METHODS: Epidermal growth factor-tagged liposomes were loaded with water-soluble boronated acridine developed for boron neutron capture therapy, (BNCT). Cellular uptake and distribution were studied. Further, cells were placed at 3 cm depth in a phantom and exposed to an epithermal neutron beam to study clonogenic cell survival. RESULTS: The cellular uptake of boron reached 90 ppm and it was determined by subcellular fractionation that most of the cell-associated boron was located outside of the nucleus. For clonogenic survival, the cells were incubated with epidermal growth factor receptor-targeted liposomes for 4 hours resulting in a cellular concentration of 55 ppm boron (11 ppm 10B). At a fluence of 3 x 10(12) neutrons/cm2 the cell killing effect of the boron-containing epidermal growth factor-liposomes was about ten times higher than for neutrons only. Furthermore, theoretical calculation of the survival by enriched compound (55 ppm 10B), using the parameters from non-enriched compound (11 ppm 10B), shows that the killing effect in this case would be approximately five orders of magnitude higher than for neutrons only. CONCLUSION: The results in this study show that epidermal growth factor-receptor targeted liposomes are suitable as tumor-cell delivery agents of boron for BNCT and support further studies to demonstrate their effectiveness in vivo.

An aminoacridine derivative for radionuclide therapy: DNA binding properties studied in a novel cell-free in vitro assay.

Radiolabelled DNA-binding compounds can be used to increase the efficiency of radionuclide cancer therapy of disseminated disease. In this work, the aminoacridine compound N-[3-(acridine-9-ylamino)-propyl]-3-iodobenzamide (A3) labelled with the Auger-emitting nuclide 125I using Chloramine-T was studied. Optimal labelling conditions of 125I-A3 were investigated and the interaction with DNA was studied using a novel cell-free in vitro assay with naked human genomic DNA in agarose plugs. This novel assay showed to be simple and reliable. The results verify that 125I-A3 specifically binds DNA with low dissociation and is potent in causing double-strand breaks, yielding 1.0-1.4 breaks per decay. In conclusion, 125I-A3 is a most suitable DNA-binding compound for future therapeutic studies of Auger-electron emitters like 125I.

Trastuzumab-conjugated boron-containing liposomes for tumor-cell targeting; development and cellular studies.

The goal of the present study was to investigate HER-2-targeted boron-containing liposomes as a potential drug delivery vehicle for boron neutron capture therapy (BNCT). Trastuzumab was conjugated to the distal end of PEG-DSPE-NHS in micelles and the Trastuzumab-PEG-DSPE were then transferred to preformed liposomes, either empty or loaded with water soluble boronated acridine (WSA), using the micelle transfer method. The final conjugates were referred to as Trastuzumab-liposome and Trastuzumab-liposome-WSA. The binding specificity, uptake, retention and internalization of Trastuzumab-liposome-WSA conjugates were studied in cultured SK-BR-3 cells, with regard to the targeting agent, carrier, and the load. The subcellular location of WSA was studied using confocal microscopy. The conjugates showed specific binding to the HER-2 receptors of SK-BR-3 cells. High cellular uptake and internalization of the conjugates was seen, reaching 132 ppm of boron in the targeted cells after 24 h. WSA was distributed mainly in the cytoplasm and was shown to have long cellular retention, with 90% and 67% of the boron remained in the cells after 24 h and 48 h, respectively. The conjugate Trastuzumab-liposome-WSA could be considered as a potent drug delivery system for BNCT.

Ligand liposomes and boron neutron capture therapy.

Boron neutron capture therapy (BNCT) has been used both experimentally and clinically for the treatment of gliomas and melanomas, with varying results. However, the therapeutic effects on micro-invasive tumor cells are not clear. The two drugs that have been used clinically, p-boronophenylalanine, (BPA), and the sulfhydryl borane, (BSH), seem to be taken up preferentially in solid tumor areas but it is uncertain whether enough boron is taken up by micro-invasive tumor cells. To increase the selective uptake of boron by such cells, would be to exploit tumor transformation related cellular changes such as over-expression of growth factor receptors. However, the number of receptors varies from small to large and the uptake of large amounts of boron for each receptor interaction is necessary in order to deliver sufficient amounts of boron. Therefore, each targeting moiety must deliver large number of boron atoms. One possible way to meet these requirements would be to use receptor-targeting ligand liposomes, containing large number of boron atoms. This will be the subject of this review and studies of boron containing liposomes, with or without ligand, will be discussed. Two recent examples from the literature are ligand liposomes targeting either folate or epidermal growth factor (EGF) receptors on tumor cells. Other potential receptors on gliomas include PDGFR and EGFRvIII. Besides the appropriate choice of target receptor, it is also important to consider delivery of the ligand liposomes, their pharmacodynamics and pharmacokinetics and cellular processing, subjects that also will be discussed in this review.

Tumor-cell targeted epiderimal growth factor liposomes loaded with boronated acridine: uptake and processing.

PURPOSE: The aim of this work was to investigate the cellular binding and processing of polyethylene glycol-stabilized epidermal growth factor (EGF) liposomes. The liposomes were actively loaded with water-soluble boronated acridine (WSA), primarily developed for boron neutron capture therapy. METHODS: The uptake, internalization, and retention of EGF-liposome conjugates were studied in two cultured monolayer cell-lines, A-431 and U-343, with regard to the nuclide-label on the targeting agent, the carrier, and the load. The subcellular localization of WSA was studied using confocal microscopy. RESULTS: We found that the liposome complex was internalized after specific binding to the EGF receptor. After internalization in the tumor cells, WSA was distributed mainly in the cytoplasm and was shown to have long cellular retention, with 80% of the boron remaining after 48 h. CONCLUSIONS: The long retention of the compound and the cellular boron concentration reached makes these targeted liposomes interesting for further development toward boron neutron capture therapy.