Spergualin treatment-dependent delayed relapse of mouse T cell leukemia (DL812) after chemotherapy

Abstract

A transplantable mouse T cell leukemia, DL 812, is characterized by high sensitivity to 3-[(4-amino-2-methyl-5-pyrimidinyl)methyl]-1-chloroethyl)-1-nitrosourea hydrochloride (ACNU) and intensive systemic infiltration. When subcutaneously inoculated, DL812 cells invade many organs and cause marked splenomegaly without forming local tumors. Disseminated DL812 leukemias are clinically completely cured by a single intraperitoneal injection of 1 mg ACNU, but more ACNU-resistant leukemias relapse immediately. A novel antitumor antibiotic, spergualin, is effective against various mouse leukemias. The effects of its analog with stronger anti-leukemia activity, 15-deoxyspergualin (DSG), on the relapse of DL812 leukemias after ACNU treatment were investigated. DDD mice were subcutaneously inoculated with 10(6) DL812 cells and intraperitoneally injected with 1 mg ACNU once on day 11 and with 100 micrograms DSG daily from day 12 on. The relapses were clinically completely suppressed for at least 30 days. Winn assays with spleen cells revealed that host immunity did not play a major role in maintenance of the clinical cure. Thus, when DSG treatment was discontinued after 15 or 30 daily injections, leukemias relapsed immediately. When it was extended to 50 daily injections, permanent cure was attained in 1 of 15 mice but relapses occurred under DSG treatment in the others. DSG is available for combined treatment of the leukemia. The current and previous results suggest that DL812 leukemias may serve as a model in study on immunochemotherapy of the disease.