Granulocyte-Macrophage Colony-Stimulating Factor and B7-2 Combination Immunogene Therapy in an Allogeneic Hu-PBL-SCID/Beige Mouse–Human Glioblastoma Multiforme Model

Abstract

Glioblastoma multiforme is the most common primary central nervous system neoplasm. Its dismal prognosis has led to investigation of new treatment strategies such as immunogene therapy. We transduced the human glioblastoma cell line D54MG in vitro with genes encoding the proinflammatory cytokine granulocyte-macrophage colony-stimulating factor (GM-CSF), the T cell co-stimulatory molecule B7-2, or both (in a bicistronic vector) via retroviral vectors. Therapeutic gene expression by D54MG was high after transduction and selection (30 ng/10⁶ cells/day for GM-CSF and >2 orders of magnitude fluorescence shift on flow cytometry for B7-2). The effect of GM-CSF and/or B7-2 transducion on D54MG tumor growth in vivo was monitored in a novel allogeneic human peripheral blood lymphocyte–severe combined immunodeficiency mouse (Hu-PBL–SCID) model. GM-CSF- or B7-2-transduced tumors showed growth suppression in hu-PBL-recon-stituted mice compared to untransduced and/or unreconstituted controls. Growth suppression was greatest for B7-2. Furthermore, vaccination with irradiated GM-CSF/B7-2-transduced tumor cells markedly inhibited growth of wild-type tumors at distant sites. Thus, this study illustrates a potential gene therapy strategy for glioblastoma multiforme patients using GM-CSF and/or B7-2 transduced tumor vaccines. Although extension of these allogeneic studies to an autologous system is critical, this is the first demonstration of in vivo efficacy of combination GM-CSF and B7-2 immunogene therapy for human glioblastoma multiforme.

Overview summary

In this study, we transferred B7-2 and GM-CSF genes to human glioblastoma multiforme cells in vitro via retroviral vectors and showed significant gene expression. In a novel allogeneic human lymphocyte–human glioblastoma–SCID mouse model, B7-2 or granulocyte-macrophage colony-stimulating factor (GM-CSF) gene expression inhibited tumor growth potential in vivo. Furthermore, vaccination with irradiated GM-CSF/B7-2-transduced tumor cells induced a human lymphocyte-mediated systemic response that inhibited wild-type tumor growth at distant sites. This demonstrated the efficacy of combination immunogene therapy using GM-CSF and B7-2 genes and a useful preclinical in vivo human glioblastoma–human lymphocyte model for immunogene therapy.