Forodesine with dGuo induces apoptosis in CLL cells in a time dependent manner and the apoptosis was abrogated by MSC (murine M210B4 and human NKtert). (A-B) Chronic lymphocytic leukemia (CLL) cells were incubated with 2μM forodesine and 20μM dGuo for 24 hours (n = 26, A) or 48 hours (n = 23, B), and the percentage viability was measured by DiOC6 in treated and untreated time-matched controls. (C-D) CLL cells were kept in suspension or cocultured with M210B4 or NKtert marrow stromal cells (MSCs) and incubated with or without forodesine and dGuo for 24 hours (n = 12, C) or 48 hours (n = 12, D), and the percentage viability was measured by DiOC6 in treated and untreated time-matched controls. C indicates CLL; F, forodesine plus dGuo; M, M210B4; and N, NKtert.