Growth and rejection of leukemia cells in individual mice after combined treatment with amphotericin B and 1,3-bis(2-chloroethyl)-1-nitrosourea.

We assayed the femoral marrows of individual AKR mice for leukemia colony-units (LCFU) after treatment with amphotericin B (AmB) and 1,3-bis(2-chloroethyl)-1-nitrosourea (BCNU) or with BCNU alone. No differences between the groups were noted in the first 7 days after treatment. All the mice treated with BCNU alone were dead by day 8, and all the survivors among the animals receiving AmB and BCNU retained high levels of LCFU for 2 more days; these LCFU were subsequently rejected by the host. By day 12, LCFU were undetectable. Histologic examination of organs from the same mice on day 5 showed fewer leukemia cells in the mice treated with the combination of agents. In all treatment groups, mice dying of leukemia early (by day 9) had systemic leukemia and most had central nervous system (CNS) involvement. All animals dying between days 10 and 14 had CNS leukemia, but few had systemic leukemia; at later times, though few animals died, they invariably had CNS leukemia without systemic involvement.