Combined Effect of Interleukin 2 and Bacillus Calmette-Guérin in the Therapy of Mice with Transitional Cell Carcinoma

We investigated the effect of combination therapy with interleukin 2 (IL-2) and Bacillus Calmette-Guerin (BCG) on C3H/HeN mice implanted with mouse bladder tumor cells (MBT2). MBT2-bearing mice were treated with a local injection of BCG into the tumor at a dose of 1 mg/day for a total of 3 times and/or a 10-day continuous subcutaneous infusion of 5 × 104 units IL-2/day from day 11 to day 20. As a result, the growth of the tumor in mice treated with IL-2 alone was slightly suppressed, while tumor growth was hardly suppressed in mice treated with BCG alone. However, when IL-2 was administered with BCG, tumor growth was strongly suppressed and mean survival time was prolonged. Natural killer cell activity in the spleen cells was most elevated in mice treated with IL-2 and BCG, while lymphokine-activated killer cell activity was not observed in all groups. Lymphocyte subset analysis showed that there was little change in the ratio of Lyt2-positive lymphocytes or that of L3T4-positive lymphocytes. These findings suggested that clinical evaluation of combination therapy with IL-2 and BCG may be worthwhile.