BackgroundUsefulness of iron chelation therapy in myelodysplastic patients is still under debate but many authors suggest its possible role in improving survival of low-risk myelodysplastic patients. Several reports have described an unexpected effect of iron chelators, such as an improvement in hemoglobin levels, in patients affected by myelodysplastic syndromes. Furthermore, the novel chelator deferasirox induces a similar improvement more rapidly. Nuclear factor-κB is a key regulator of many cellular processes and its impaired activity has been described in different myeloid malignancies including myelodysplastic syndromes. Design and MethodsWe evaluated deferasirox activity on nuclear factor-κB in myelodysplastic syndromes as a possible mechanism involved in hemoglobin improvement during in vivo treatment. Forty peripheral blood samples collected from myelodysplastic syndrome patients were incubated with 50 μM deferasirox for 18h. ResultsNuclear factor-κB activity dramatically decreased in samples showing high basal activity as well as in cell lines, whereas no similar behavior was observed with other iron chelators despite a similar reduction in reactive oxygen species levels. Additionally, ferric hydroxyquinoline incubation did not decrease deferasirox activity in K562 cells suggesting the mechanism of action of the drug is independent from cell iron deprivation by chelation. Finally, incubation with both etoposide and deferasirox induced an increase in K562 apoptotic rate. ConclusionsNuclear factor-κB inhibition by deferasirox is not seen from other chelators and is iron and reactive oxygen species scavenging independent. This could explain the hemoglobin improvement after in vivo treatment, such that our hypothesis needs to be validated in further prospective studies.Key words: iron chelation therapy, nuclear factor-κB, myelodysplastic symdrome. Haematologica 2010;95(8):1308-1316. doi:10.3324/haematol.2009 Deferasirox is a powerful NF-κB inhibitor in myelodysplastic cells and in leukemia cell lines acting independently from cell iron deprivation by chelation and reactive oxygen species scavenging Citation: Messa E, Carturan S, Maffè C, Pautasso M, Bracco E, Roetto A, Messa F, Arruga F, Defilippi I, Rosso V, Zanone C, Rotolo A, Greco E, Pellegrino RM, Alberti D, Saglio G, and Cilloni D. Deferasirox is a powerful NF-κB inhibitor in myelodysplastic cells and in leukemia cell lines acting independently from cell iron deprivation by chelation and reactive oxygen species scavenging.

Imatinib represents at present the most attractive therapy for BCR-ABL positive leukemias, even though a percentage of CML patients develop resistance to this compound. For these resistant patients a therapeutic approach based on a combination of drugs is more likely to be effective. In the last years, constitutive NF-jB/Rel activity has been demonstrated in several hematological malignancies. As a result, NFkB/Relblocking approaches have been proposed as antineoplastic strategies. Furthermore, the identification of specific kinases within the NF-jB activation pathway offers a selective target to address tailored therapies. In the current study, we show that the IKK inhibitor PS1145 is able to inhibit the proliferation of CML cell lines and primary BM cells. Moreover, the addition of Imatinib increases the effects of PS1145 in resistant cell lines and BM cells from resistant patients, with a further increase of apoptosis and inhibition of proliferation and colony growth. Our data provide the rational for a new therapeutic approach, which combines Imatinib and the IKK inhibitor PS1145 in CML resistant patients.

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BACKGROUNDThe objective of this study was to evaluate the ability of the clinically available histone deacetylase (HDAC) inhibitor valproate to enhance the cytotoxicity of the Bcr‐Abl inhibitor imatinib in imatinib‐resistant cell lines.METHODSInteractions between imatinib, and valproate have been examined in imatinib‐sensitive and ‐resistant chronic myeloid leukemia (CML)cell lines (K562, KCL‐22, CML‐T1) and in bone marrow mononuclear cells (MNCs) derived from imatinib‐resistant CML patients.RESULTSIn imatinib‐sensitive cell lines, cotreatment with imatinib 0.5 μM and valproate 5 μM for 48 hours potently enhanced imatinib‐induced growth arrest and apoptosis. In resistant cell lines and in primary MNCs derived from imatinib‐resistant patients, valproate restored sensitivity to the cytotoxic effects of imatinib. Coexposure of cells to valproate and imatinib was associated with repression of several genes involved in Bcr‐Abl transformation. In particular, the combination valproate–imatinib downregulated the expression of Bcr‐Abl and the antiapoptotic protein Bcl‐2, which is particularly overexpressed in imatinib‐resistant clones.CONCLUSIONSData from this study suggested that administration of the clinically available HDAC inhibitor valproate may be a powerful strategy to enhance cytotoxic effects of imatinib in those patient resistant to imatinib or in which complete cytogenetic remission has been not reached. Cancer 2006. © 2006 American Cancer Society.

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