Tumor heterogeneity, which describes the genetically and phenotypically distinct subpopulations of
tumor cells present within the same
tumor or patient, presents a major challenge to targeted delivery of diagnostic and/or therapeutic agents. An ideal targeting strategy should deliver a given nanocarrier to the full diversity of
cancer cells, which is difficult to achieve with conventional
ligand-conjugated nanoparticles. We evaluated pretargeting (i.e., multistep targeting) as a strategy to facilitate nanoparticle delivery to multiple target cells by measuring the uptake of biotinylated nanoparticles by
lymphoma cells with distinct
surface antigens pretreated with different bispecific
streptavidin-scFv fusion
proteins. Fusion
proteins targeting CD20 or
tumor-associated
glycoprotein 72 (TAG-72) mediated the specific in vitro uptake of 100nm
biotin-functionalized nanoparticles by Raji and Jurkat
lymphoma cells (CD20-positive and TAG-72-positive cells, respectively). Greater uptake was observed for pretargeted nanoparticles with increasing amounts of surface
biotin, with 6- to 18-fold higher uptake vs. non-biotinylated nanoparticle and fusion
protein controls. Fully
biotin-modified particles remained resistant to cultured macrophage cell uptake, although they were still quickly cleared from systemic circulation in vivo (t1/2<1h). For single Raji
tumor-bearing mice, pretargeting with CD20-specific FP significantly increased nanoparticle
tumor targeting. In mice bearing both Raji and Jurkat
tumors, pretargeting with both fusion
proteins markedly increased nanoparticle targeting to both
tumor types, compared to animals dosed with nanoparticles alone. These in vitro and in vivo observations support further evaluations of pretargeting fusion
protein cocktails as a strategy to enhance nanoparticle delivery to a diverse array of molecularly distinct target cells.