Nitric oxide and caspase 3 mediated cytokine induced apoptosis in acute leukemia.

BACKGROUND Leukemia is characterized by the uncontrolled accumulation of white blood cells. Recently, cytokines have been used in immunotherapy, which is a new strategy for leukemia treatment. OBJECTIVE To investigate the effect of cytokines on induction of apoptosis in acute leukemic cell lines; HL-60, MV4-11, K-562 and Molt-4 and in addition, to study the involvement of nitric oxide (NO) in apoptotic pathways. METHODS Leukemic cell lines were incubated with cytokines; interleukin-1beta, tumor necrosis factor-alpha, and interferon-gamma in various concentrations and for variable periods of time. The percent apoptosis and caspase 3 activation were examined by flow cytometry. Moreover, NO production and inducible nitric oxide synthase (iNOS) mRNA were measured by using Griess method and Real-time PCR, respectively. RESULTS Cytokines caused a time and dose-dependent induction of apoptosis in leukemic cell lines. The highest cell apoptosis was found in K-562 treated with 40 U/ml interferon-gamma for 48 hours; this correlated with the result of cell growth inhibition and caspase 3 activation. NO and iNOS mRNA were increased in cytokines treated cells. Moreover, apoptosis was reduced by SMT, an iNOS inhibitor, which confirms the possible involvement of NO in the apoptotic pathway. CONCLUSION Cytokines especially interferon-y induced apoptosis in acute leukemia via NO and caspase 3 pathway.