EXPERIMENTAL GENE-THERAPY OF CANCER USING TUMOR-CELLS ENGINEERED TO SECRETE INTERLEUKIN-13

Cytokines locally delivered to the site of a tumor boost both specific and nonspecific host anti-tumor defenses. Interleukin (IL)-13 is a re cently described cytokine produced by a mouse type 2 helper T lymphocy tes. The aim of this study was to evaluate the inhibition of tumor gro wth induced by IL-13 delivered locally within or around transplanted t umor cells in mice. We observed that local administration of IL-13 at the site of transplanted tumor cells in vivo had potent inhibitory eff ects on growth of both immunogenic (P815 mastocytoma, H-2(d)) or nonim munogenic (3LL lung carcinoma, H-2(b)) tumor cells. Mice injected with transfected P815 cells secreting large amounts of IL-13 rejected the P815 tumor and developed systemic specific anti-tumor immunity leading to long-lasting specific anti-tumor protection. Less efficient anti-t umoral effects were obtained with the nonimmunogenic 3LL tumor model w hen local administration of IL-13 was achieved by co-inoculating xenog eneic chinese hamster ovary (CHO) IL-13 cells. Several local injection s of CHO IL-13 cells were needed to obtain rejection of 3LL tumors and no induction of long-lasting anti-3LL memory was obtained. Several st udies were performed to elucidate the IL-13 anti-tumoral effects. Expe riments with mude mice indicated that IL-13 can also stimulate nonspec ific anti-tumor defenses. The histological examination of P815 IL-13 c ells under-going rejection showed monocytic cells and neutrophils infi ltrating the tumor. Studies indicated that IL-13 administered in vitro did not directly stimulate the cytotoxicity of peritoneal macrophages and natural killer cells. However, experiments with Boyden chemotaxis chambers indicated that IL-13 was chemotactic for macrophages. Finall y, preliminary experiments in vitro suggest that IL-13 improved antige nic presentation of P815 membranes. Thus, anti-tumor effects of IL-13 in vivo most probably result from pleiotropic effects including recrui tment of nonspecific cells and improved stimulation of immune-specific anti-tumor effectors.