Engineering a Cell-Penetrating Anti-HER2 Monoclonal Antibody for Efficient Delivery of Gold Nanoparticles into Cancer Cells To Enhance X-Ray Cancer Radiation Therapy

Abstract

Gold nanoparticles (GNPs) can create heat and free radicals after absorbing high energy photons from radiation. This light absorptive property has been utilized in cancer radiotherapy to produce highly localized heating and destroy cancer cells. For specific tumor accumulation, GNPs can be attached to monoclonal antibodies (mAbs) that recognize cell surface proteins overexpressed in certain types of cancer. One of these surface receptors is HER2, which is overexpressed in 20-25% of breast cancers and, therefore, constituted a suitable target for such mAb-driven GNP tumor localization. However, many mAbs cannot cross the cell membrane efficiently. To enable the efficient shuttling of GNPs into cancer cells, protein engineering technology was implemented to fuse penetratin, a cell-penetrating peptide (CPP), to the C-terminus of a wide-type anti-HER2 antibody heavy chain, generating a cell-penetrating mAb specific to the HER2 receptor. One of the recombinant mAbs (mAb-2CPP) completely preserved the HER2-binding activity and could promote the internalization of the antibody into MCF-7 and PC3 cancer cells that express HER2 on the cell surface. Both cell lines were then treated with GNPs conjugated to wild-type mAb (mAb-GNP) or mAb-CPP fusion (mAb-2CPP-GNP). The MAb-2CPP-GNP complex generated a higher mortality rate than mAb-GNP, likely due to more accumulation of GNPs in the cells. The study also investigated the interaction between X-ray radiation and GNPs, demonstrating that GNPs augmented the efficacy of X-ray radiation. Thus, a much lower dose of radiation could be used to generate a similar cell mortality rate. More GNPs were carried by mAb-2CPP into cancer cells and increased the cell mortality rate in a dose-dependent manner. Thus, an effective cell-penetrating antibody could promote the delivery of GNPs into target cancer cells and augment the efficacy of cancer radiotherapy with reduced side effects to patients.

Improving Receptor-Mediated Intracellular Access and Accumulation of Antibody Therapeutics—The Tale of HER2

“…Unfortunately, the CPP-gold conjugates had significant increased uptake in SKBR3 and MCF7 cells compared to CPP-gold-trastuzumab conjugates. In contrast, Guo et al screened a panel of various anti-HER2 mAbs conjugated to the CPP penetratin [129]. One penetratin-anti-HER2 mAb retained HER2 specificity and efficiently internalized into MCF7 and PC-3 (HER2-positive) cells.…”