Combination immunotherapy of the P815 murine mastocytoma with killer cells, IL-2 and anti-estrogens.
BACKGROUND: Lymphokine activated killer (LAK) cells, cytotoxic T lymphocytes (CTL) and interleukin-2 (IL-2) all are being tested in cancer immunotherapy with modest success. The anti-estrogenic drug, toremifene (T0), was found earlier to amplify cancer immunotherapy with killer cells in mice. Here T0 is examined in combination with CTL and IL-2 in immunotherapy experiments. MATERIALS AND METHODS: The P815 mastocytoma of DBA/2 mice was treated with combinations of CTL, LAK cells and T0 and combinations of CTL, IL-2 and T0 along with control groups. Tumor growth rate and mortality has been recorded. RESULTS: Combined treatment with CTL and LAK cells cured 25% of tumor bearing animals, as did treatment with tamoxifen (TX) or T0 alone. When killer cells were given in conjunction with anti-estrogens the cure rate was 75% with both TX and T0. Human recombinant IL-2 significantly inhibited tumor growth but no cures occurred. CTL alone cured 25% of the animals. When CTL and IL-2 treatment was given jointly with T0 75% of tumor bearing animals were cured. CONCLUSIONS: The results indicate that treatment with anti-estrogens increased the efficiency of immunotherapy by killer cells. This was true also when CTL therapy was supplemented with IL-2 treatment.