Specifically, we aimed to optimize the therapeutic efficacy of Flt3L/TK treatment in the RG2 model by overexpressing the following genes within the brain tumor microenvironment: 1) a TK mutant with enhanced cytotoxicity (SR39 mutant TK), 2) Flt3L-IgG fusion protein that has a longer half-life, 3) CD40L to stimulate DC maturation, 4) T helper cell type 1 polarizing dendritic cell cytokines interleukin-12 or C-X-C motif ligand 10 chemokine (CXCL)-10, 5) C-C motif ligand 2 chemokine (CCL2) or C-C motif ligand 3 chemokine (CCL3) to enhance dendritic cell recruitment into the tumor microenvironment, 6) T helper cell type 1 cytokines interferon-γ or interleukin-2 to enhance effector T-cell functions, and 7) IκBα or p65RHD (nuclear factor kappa-B [NF-κB] inhibitors) to suppress the function of Foxp3+ Tregs and enhanced effector T-cell functions.
The results indicate that IL-2-secreting allogeneic fibroblasts can be effective in the treatment of an established brain tumor.These data also suggest that i.c. injection of allogeneic IL-2-secreting fibroblasts is effective in prevention of the development of a brain tumor when the fibroblasts are introduced into the same site where the tumor is subsequently injected.
The present study may also raise the possibility of a therapeutic strategy for brain tumors by the combinatory expression of IL-2 gene using s.c. immunization followed by direct gene transfer into brain tumors.
In this study, specific binding of radiolabeled IL-2 to PHA-stimulated lymphocytes from brain tumor patients demonstrates that the number of high affinity interleukin 2 receptors (IL-2R) is greatly reduced.