Aminopeptidase inhibitor ubenimex inhibits the growth of leukaemic cell lines and myeloma cells through its cytotoxicity

We investigated the effect of ubenimex, which has been demonstrated to have immunomodulating activities, on the proliferation of human leukaemic cell lines (HL 60 and K 562, myelogenic lines, Jurkat, a T-cell line and RPMI 82 26, a multiple myeloma cell line) and on human bone marrow mononuclear cell s from haematopoietic malignancy patients with acute myeloblastic leukaemia , chronic lymphocytic leukaemia or multiple myeloma. The growth of the myel oid cell lines and of a multiple myeloma cell line, but not the T-cell line , was significantly inhibited by cocultivation with ubenimex in a dose-depe ndent manner. The results of the experiment with haematopoietic malignancy cells showed inhibitory effects on tumour cells from patients with acute my eloblastic leukaemia and multiple myeloma, but not on those from patients w ith chronic lymphocytic leukaemia. These findings suggest the usefulness of ubenimex for the treatment of multiple myeloma.