Interleukin 12 gene transfer into skin distant from the tumor site elicitsantimetastatic effects equivalent to local gene transfer

We have reported that particle-mediated interleukin 12 (IL-12) gene transfe r into the skin overlying the local tumor inhibits systemic metastases. To further characterize this effect, we compared the antitumor and antimetasta tic effects of IL-12 cDNA delivered at the local tumor site versus at a sit e distant from the primary tumor, in a spontaneous metastasis model of LLC- F5 tumor. Local IL-12 gene delivery into the skin overlying the intradermal tumor (local IL-12 treatment) on days 7, 9, and 11 after tumor implantatio n resulted in the most suppression of the growth of the primary LLC-F5 tumo r, whereas IL-12 gene transfer into the skin distant from the tumor (distan t LL-12 treatment) was less effective. In contrast, both local IL-12 and di stant IL-12 treatment, followed by tumor excision, inhibited lung metastase s to a similar extent, resulting in significantly extended survival of test mice. The results of in vivo studies using depleting anti-asialo GM1 antib ody and anti-CD3/anti-CD8 monoclonal antibodies, or neutralizing anti-inter feron gamma (IFN-gamma) monoclonal antibody demonstrated that natural kille r (NK) cells, CD8(+) T cells, and IFN-gamma contributed to the antimetastat ic effects in both treatment groups. Furthermore, the levels of mRNA expres sion of vascular endothelial growth factor and matrix methalloproteinase 9 at the tumor microenvironment were suppressed after both local and distant IL-12 treatment. These results suggest that the current particle-mediated I L-12 gene delivery in the spontaneous LLC-F5 metastasis model can confer an timetastatic activities, irrespective of the gene transfection site, via a combination of several mechanisms involving CD8(+) T cells, NK cells, IFN-g amma, and antiangiogenesis.