Tat-BMPs-PAMAM Conjugates Enhance Therapeutic Effect of Small Interference RNA on U251 Glioma Cells In Vitro and In Vivo

Han and colleagues engineer an existing nonviral biocarrier based on polyamidoamine dendrimers to deliver an interfering RNA to downregulate expression of the oncogenic epidermal growth factor receptor in gliomas. To enable cell targeting and entry, and eventual transduction, portions of the HIV-1 Tat protein and magnetic nanoparticle technology were incorporated in the design. Polyamidoamine (PAMAM) dendrimer and Tat peptides were conjugated to bacterial magnetic nanoparticles (BMPs) for the construction of an efficient and targeted gene delivery system with transmembrane ability for the gene therapy of brain tumors. Tat-BMPs-PAMAM was complexed with small interfering RNA expression plasmid (psiRNA) corresponding to the open reading frame of the human epidermal growth factor receptor gene (psiRNA-EGFR) to downregulate the EGFR gene by electrostatic interaction. The antitumor effect of psiRNA-EGFR delivered via Tat-BMPs-PAMAM was assessed both in human glioblastoma U251-MG cells and in nude mouse models. Compared with control groups, Tat-BMPs-PAMAM/psiRNA-EGFR resulted in better suppression of EGFR expression and a more obviously arrested effect on the proliferation and invasion ability of U251 cells in vitro. In addition, the growth rate of tumor in the U251 subcutaneous nude mouse model treated with Tat-BMPs-PAMAM/psiRNA-EGFR was slower than in those treated with phosphate-buffered saline or Lipofectamine 2000/psiRNA-Scr. Also, compared with control groups, the expression of oncoproteins (EGFR, p-AKT, MMP2/9, PCNA, VEGF, Bcl-2, and cyclin D1) was obviously downregulated and the number of apoptotic cells was clearly increased in the Tat-BMPs-PAMAM/psiRNA-EGFR treatment groups. In addition, there was no significant difference between the results in vitro and in vivo for the Tat-BMPs-PAMAM/psiRNA-EGFR treatment groups and those of the Lipofectamine 2000/psiRNA-EGFR treatment groups. These results show that Tat-BMPs-PAMAM, with its targeted delivery and transmembrane ability, may be a novel gene delivery system with potential applications in the targeted gene therapy of brain tumors.