Immunogene therapy

Characterization of CSF2A fusion gene and its effect on Epstein-Barr virus-positive tumor cells

We build the latent membrane protein gene latent membrane protein 2A (LMP2A) and the granulocyte-macrophase colony-stimulating factor (GM-CSF) gene fusion gene (CSF2A) and discuss how the CSF2A fusion protein influenced the proliferation and apoptosis of Epstein-Barr virus-positive (EBV⁺ ) tumor cells. Reverse-transcription polymerase chain reaction (RT-PCR) method was used to amplify the LMP2A gene and GM-CSF gene fragments, respectively, according to the principle of overlap extension in the coding (Gly4Ser)₃ polypeptide gene fragments of DNA restructured under the connection. The CSF2A gene could be connected with the pIRES2-enhanced green fluorescent protein vector by recombinant DNA technology and identified by enzyme electrophoresis analysis and DNA sequencing. Then, the recombinant vector was transfected into dendritic cells (DCs); RT-PCR and Western blot analysis were used for testing the CSF2A gene messenger RNA and protein expression. The impacts of CSF2A on the proliferation and apoptosis of EBV⁺ tumor cells were determined by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay and Hochest 33342 staining. We successfully obtained the recombinant vector named pIRES2-CSF2A. The expression of CSF2A could be detected by transfecting pIRES2-CSF2A into DCs. The DCs were cocultured with T lymphocytes and then acted on the EBV⁺ CNE2 nasopharyngeal carcinoma cells. MTT assay showed that the inhibiting effect of CSF2A obviously increased and the time dependency (**P < 0.01, *P < 0.05) also existed. Hochest 33342 staining showed apoptosis morphological changes of cells in nucleus staining and generated the apoptotic body. Apoptosis cells of the pIRES2-CSF2A group increased significantly at 48 hours. The results showed that the pIRES2-CSF2A recombinant vector was effectively transfected into DCs and the fusion gene CSF2A could promote EBV⁺ CNE2 cell apoptosis, laying the foundation for the specificity of EBV⁺ tumor targeting immune gene therapy in the future.

Chitosan nanoparticle-based delivery of fused NKG2D-IL-21 gene suppresses colon cancer growth in mice

Nanoparticles can be loaded with exogenous DNA for the potential expression of cytokines with immune-stimulatory function. NKG2D identifies major histocompatibility complex class I chain-related protein in human and retinoic acid early induced transcript-1 in mouse, which acts as tumor-associated antigens. Biologic agents based on interleukin 21 (IL-21) have displayed antitumor activities through lymphocyte activation. The NKG2D-IL-21 fusion protein theoretically identifies tumor cells through NKG2D moiety and activates T cells through IL-21 moiety. In this study, double-gene fragments that encode the extracellular domains of NKG2D and IL-21 genes were connected and then inserted into the pcDNA3.1(-) plasmid. PcDNA3.1-dsNKG2D-IL-21 plasmid nanoparticles based on chitosan were generated. Tumor cells pretransfected with dsNKG2D-IL-21 gene nanoparticles can activate natural killer (NK) and CD8⁺ T cells in vitro. Serum IL-21 levels were enhanced in mice intramuscularly injected with the gene nanoparticles. DsNKG2D-IL-21 gene nanoparticles accumulated in tumor tissues after being intravenously injected for ~4-24 h. Treatment of dsNKG2D-IL-21 gene nanoparticles also retarded tumor growth and elongated the life span of tumor-bearing mice by activating NK and T cells in vivo. Thus, the dsNKG2D-IL-21 gene nanoparticles exerted efficient antitumor activities and would be potentially used for tumor therapy.