Acute myelogenous leukemia (AML) remains a deadly disease for most adult patients, due primarily to the emergence of chemoresistant cells. Defects in apoptosis pathways make important contributions to chemoresistance, suggesting a need to restore apoptosis sensitivity or to identify alternative pathways for apoptosis induction. Triterpenoids represent a class of naturally occurring and synthetic compounds with demonstrated antitumor activity, including 2-cyano-3,12-dioxoolean-1,9-dien-28-oic acid (CDDO) and its methyl ester (CDDO-m). We explored the effects of CDDO and CDDO-m in vitro on established AML cell lines (HL-60, U937, AML-2) and on freshly isolated AML blasts. CDDO and CDDO-m reduced the viability of all AML cell lines tested in a dose-dependent manner, with effective doses for killing 50% of cells (ED 50 ) within 48 h of B1 and 0.5 lM, respectively. CDDO or CDDO-m also induced substantial increases in cell death in five out of 10 samples of primary AML blasts. Cell death induced by CDDO and CDDO-m was attributed to apoptosis, based on characteristic cell morphology and evidence of caspase activation. Immunoblot analysis demonstrated proteolytic processing of caspase-3, -7, and -8, but not caspase-9, suggesting the involvement of the 'extrinsic' pathway, linked to apoptosis induction by TNF-family death receptors. Accordingly, CDDO and CDDO-m induced concentration-dependent reductions in the levels of FLIP protein, an endogenous antagonist of caspase-8, without altering the levels of several other apoptosis-relevant proteins. Reductions in FLIP were rapid, detectable within 3 h after exposure of AML cell lines to CDDO or CDDO-m. CDDO and CDDO-m also sensitized two of four leukemia lines to TRAIL, a TNF-family death ligand. The findings suggest that synthetic triterpenoids warrant further investigation in the treatment of AML, alone or in combination with TRAIL or other immunebased therapies.

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We investigated the effects of recombinant human thrombopoietin (TPO) in combination with various cytokines including erythropoietin (EPO), interleukin-3 (IL-3), interleukin-6 (IL-6), and stem cell factor (SCF) on megakaryopoiesis, and the expansion of CD34+CD41a+ cells from human cord blood CD34+ cells with these cytokines under serum-free conditions. Human cord blood CD34+ cells were cultured in Megacult (Stem Cell Technologies Inc. Vancouver, Canada) in the presence of recombinant growth factors. Colony-forming unit-megakaryocyte (CFU-M) colonies were counted on day 14. CD34+CD41a+ and CD34-CD41a+ cell expansion was analyzed using a serum-free liquid culture system for 7 days with recombinant growth factors. TPO alone had a concentration-dependent effect on megakaryocyte colony growth. At concentrations above 1 ng/ml, TPO supported significant CFU-Meg colony formation in a concentration-dependent manner. The combination of TPO plus other cytokines, including EPO, IL-3, and SCF, resulted in a synergistic enhancement of the number of CFU-Meg colonies, but IL-6 failed to enhance the effect of TPO. The number of CD41a+ cells increased after 7 days in liquid culture of human cord blood CD34+ cells with various cytokines (EPO, IL-3, IL-6, SCF) combined with TPO, but SCF plus TPO only resulted in a significant synergistic increment of CD34+CD41a+ cells compared with TPO alone. The results of the present study indicate that EPO, IL-3, and SCF can be synergistic with TPO to stimulate proliferation of CFU-Meg and suggest that SCF plus TPO can expand CD34+CD41a+ cells to effect the rapid recovery of platelets in patients following stem cell transplantation.

Early weaning of maternally derived measles antibodies therefore vaccination of MCV1 at a young age from 9 months to 12 months should be considered in situations of early exposure. Furthermore, there is a call for consideration of scheduling an earlier age for the first dose of MMR vaccine in Europe. It is necessary for Korea to investigate the duration of the presence and quantitative analysis of maternal measles antibodies in infants and to reconsider the timing of MCV1.