Use of thymidine kinase gene-modified endothelial progenitor cells as a vector targeting angiogenesis in glioma gene therapy

Abstract

Objective: The poor prognosis of patients with glioma is due to infiltrative growth of glioma cells, which correlates with their ability to induce angiogenesis. Tumor angiogenesis is supported by the mobilization and functional incorporation of endothelial progenitor cells (EPCs). The aim of this study was to propose the use of gene-modified EPCs as a vector system that allowed systemic gene delivery into multiple areas of tumor angiogenesis for glioma therapy.

Methods: Thymidine kinase (TK) gene-modified EPCs were mixed with glioma cells or human umbilical vein endothelial cells (HUVECs) at varying ratios for ganciclovir in vitro. Cell proliferation was evaluated by MTT assay, and apoptosis was examined by annexin-V and phosphatidylserine (propidium iodide) staining. EPCs were injected via tail vein into nude mice bearing glioma, and EPC incorporation into the tumor was determined immunohistochemically. The antitumor effects of TK gene-modified EPCs in vivo were evaluated by apoptosis assay and microvessel density analysis.

Results: TK gene-modified EPCs exerted a potent bystander effect on glioma cells and HUVECs by induction of apoptosis via caspase activation in vitro. EPCs incorporated preferentially into glioma vasculatures. Furthermore, TK gene-modified EPCs clearly augmented the antitumor effect by inhibition of angiogenesis following repeated intravenous injection in vivo.

Conclusion: The results indicate the feasibility of EPC-based gene delivery into disseminated areas of tumor angiogenesis as a rational strategy for glioma gene therapy.