Effects of immunization with tumor cells double transfected with interleukin-2 (IL-2) and interleukin-12 (IL-12) genes on artificial metastasis of colon26 cells in BALB/c mice.

In order to induce tumor specific cytotoxicity, the poorly immunogenic murine colon cancer cell colon26 was transfected with murine IL-2 cDNA and/or IL-12 cDNA and their anti-tumor effects were investigated. Double transfectants produced murine IL-2 and murine IL-12, the same as single transfectants. Intraperitoneal administration of double transfectants inhibited pulmonary metastasis of colon26 inoculated intravenously to a stronger degree than that of single transfectants. Splenocytes from mice administered double transfectants intraperitonealy showed higher cytolytic activity against colon26 than those from mice administered single transfectants, and also showed cytolytic activity against murine B16-BL6 melanoma. In the NK cell-depleted mice, double transfectants inhibited pulmonary metastasis from the control markedly, but could not do completely, the same as in the NK cell-reserved mice. The difference of the metastatic colonies between NK cell-depleted mice and the control was much greater than that between NK cell-depleted mice and NK cell-reserved mice. These results suggested that cytotoxic T lymphocytes might participate in this anti-tumor effect.