Herceptin Research Today is a free monthly online journal that collates and summarizes the latest research about Herceptin, including details on side-effects, breast cancer, treatment, therapy.

Trastuzumab-polyethylenimine-polyethylene glycol conjugates for targeting Her2-expressing tumors.

Germershaus O, Merdan T, Bakowsky U, Behe M, Kissel T

Department of Pharmaceutics and Biopharmacy, Philipps University Marburg, Ketzerbach 63, 35032 Marburg, Germany.

In this study, we describe the synthesis and characterization of a conjugate consisting of poly(ethylene glycol 2,000 Da)(10)-graft-poly(ethylene imine 25 kDa) (PEG-PEI) covalently coupled to Trastuzumab (Herceptin) via N-succinimidyl-3-(2-pyridyldithio)propionate (SPDP) for specific gene delivery to Her2-expressing cell lines. The efficiency of DNA condensation was studied using an ethidium bromide exclusion assay and demonstrated negligible differences compared to PEG-PEI. Conjugate complex sizes were determined by dynamic light scattering to be in the range 130-180 nm. zeta potentials at different N/P ratios were close to neutral. Flow cytometry and confocal microscopy revealed efficient binding and uptake of Trastuzumab-PEI-PEG complexes using Her2-positive SK-BR-3 cells. In contrast, binding and uptake into Her2-negative OVCAR-3 cells was negligible. In good correlation with these findings, reporter gene expression using targeted complexes in SK-BR-3 cells was up to sevenfold higher than that of unmodified PEG-PEI complexes. With the use OVCAR-3 cells, no significant difference in expression efficiencies could be observed between conjugate and PEG-PEI complexes. Inhibition experiments with free Trastuzumab showed a significant decrease in reporter gene expression using SK-BR-3 cells but no decrease using OVCAR-3 cells, strongly supporting a specific Her2-receptor-mediated uptake mechanism. Our results suggest that Trastuzumab-PEI-PEG might be a promising new bioconjugate for targeted gene transfer to Her2-positive tumor cells in vivo.

Published 20 September 2006 in Bioconjug Chem, 17(5): 1190-9.
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