INDUCTION OF ANTITUMOR IMMUNITY BY MOUSE-TUMOR CELLS TRANSFECTED WITHMOUSE INTERLEUKIN-12 GENE

Interleukin-12 (IL-12) is a heterodimeric cytokine. In order to transd uce both cDNAs for p35 and p40 of IL-12 in the tumor cells, a polycist ronic retroviral vector was constructed by inserting the internal ribo some entry site gene of encephalomyocarditis virus between two cDNAs. On the other hand, two cDNAs were sequentially transfected in the tumo r cells. Both polycistronic gene transfectants and double transfectant s produced biologically active mouse IL-12. IL-12-expressing tumor cel ls were all rejected in syngeneic mice, and induced cytotoxic T lympho cyte activity. The capacity to induce anti-tumor memory may depend on the amount of IL-12 produced by the transfectants, because the relativ ely higher IL-12 producer tumor cell line induced the anti-tumor memor y in the rejected mice, but the lower producer did not.