BREAST-CANCER GENE-THERAPY - TRANSGENIC IMMUNOTHERAPY

A number of studies have demonstrated that potent anti-tumor immunity can be induced using cytokine gene transfer, a strategy termed transge nic immunotherapy. Our aim is to express cytokine genes in the vicinit y of tumor cells, either by transducing tumor cells themselves, or by delivering cytokine-expressing endothelial cells to tumor sites. We co mpared the ability of cytokine-expressing tumor cells or endothelial c ells to inhibit the tumorigenesis of MDA-MB-435 breast cancer cells in athymic nude mice. Retroviral vectors containing either human interle ukin 2 (hIL-2) or interleukin 1 (hIL-1 alpha) were used to transduce M DA-MB-435 cells or human umbilical vein endothelial cells (HUVEC). Usi ng a modified MTT bioassay and an ELISA specific for hIL-2, 43 of 70 M DA-MB-435 clones transduced with IL-2 were found to secrete between 10 0-800 units of IL-2/10(6) cells/24 hr. hIL-2 and hIl-1 alpha-transduce d HUVEC secreted 40 ng/IL-2/10(6)/24 hr and 1.8 ng/10(6)/24 hr, respec tively. To facilitate in vivo tracking of tumor cells, both nontransdu ced and IL-2-expressing MDA-MB-435 cells were genetically-marked with the E. coli lacZ gene and selected using flow cytometry. To study in v iva tumorigenicity, cells were injected into the mammary fat pad of at hymic nude mice: (1) lacZ/MDA-MB-435 cells injected alone formed tumor s in all animals; (2) IL-2-expressing lacZ/MDA-MB-435 cells did not fo rm any tumors; (3) co-inoculation of MDA-MB-435/IL-2, HUVEC/IL-2 or HU VEC/IL-1 alpha with lacZ/MDA-MB-435 cells prevented or delayed tumor g rowth. These results suggest that local cytokine secretion was capable of activating natural killer cell activity in host animals. Transgeni c immunotherapy is a promising approach that may be useful for the era dication of minimal residual disease.