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 8226, a multiple myeloma cell line) and on human bone marrow mononuclear cells from haematopoietic malignancy patients with acute myeloblastic leukaemia, chronic lymphocytic leukaemia or multiple myeloma. The growth of the myeloid 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-dependent manner. The results of the experiment with haematopoietic malignancy cells showed inhibitory effects on tumour cells from patients with acute myeloblastic leukaemia and multiple myeloma, but not on those from patients with chronic lymphocytic leukaemia. These findings suggest the usefulness of ubenimex for the treatment of multiple myeloma.