EFFECT OF PERIOPERATIVE CHEMOIMMUNOTHERAPY WITH CYCLOPHOSPHAMIDE AND AUTOLOGOUS TUMOR VACCINE IN MURINE MBT-2 BLADDER-CANCER

The in vitro cytotoxic activity of splenocytes from C3H/He mice implan ted subcutaneously with 10(6) syngeneic MBT-2 tumor cells on day 0 was significantly enhanced after cyclophosphamide (100 mg./kg., intraperi toneally) given 2 days before tumor resection on day 17, with or witho ut active specific immunization with BCG plus autologous irradiated tu mor cells (vaccine) 1 week after tumor resection. Furthermore, a signi ficantly lower tumor incidence was seen in mice challenged with 10(5), but not 10(6), tumor cells per mouse 24 hours after tumor resection o n day 17 and treated with cyclophosphamide on day 15 and postoperative ly with vaccine than was found in nontreated tumor resected mice. Phen otypic analysis of cells from spleen showed that cyclophosphamide pret reatment and postoperative vaccine, either singly or in combination, i nduced a significant increase of both CD44(+) memory T cells and CD11b (+) myeloid/macrophage cells. Thus, in addition to a specific antitumo r immune response, a nonspecific cytolytic mechanism may also play a r ole in the observed antitumor effect.