Cationic lipid gene transfer of an IL-2 transgene leads to activation of natural killer cells in a SCID mouse human tumor xenograft

Natural killer (NR) cells play an important role in combating infectious and malignant diseases and interleukin-2 (IL-2) has been shown to promote proliferation and activation of Mt cells in vitro and in vivo, Here we investigate the effects of local cationic lipid-mediated IL-2 gene transfer on intratumoral accumulation and activation of NK cells in a SCID mouse tumor model. UM449 human melanoma tumors in SCID mice received intratumoral injections of DMRIE/ DOPE admired with VR1103, a DNA plasmid encoding the gene for human IL-2. Dissagregated tumor cells were tested for IL-2 secretion and were characterized using antibodies to asGM1, MAC-I, and F4/80 antigens, Granzyme A, a proteolytic serine esterase, was also measured in tumor cell lysates, IL-2 secretion from tumors injected with VR1103:DMRIE/DOPE peaked at 48 h after injection and fell to baseline levels on day 8, Intratumoral granzyme A activity was significantly increased in tumors injected with IL-2 plasmid:DMRIE/DOPE complexes, but not by an irrelevant plasmid DNA:DMRIE/DOPE control. Importantly, the growth of UM449 tumors was slowed in VR1103:DMRLE/DOPE-injected tumors, These results indicate that local cationic lipid-mediated gene transfer of IL-2 induces activation of intratumoral NK cells and slows tumor growth. (C) 2000 Academic Press.