Deferasirox reduces oxidative DNA damage in bone marrow cells from myelodysplastic patients and improves their differentiation capacity.

Patients with low-risk myelodysplastic syndromes (MDS) usually develop iron overload. This leads to a high level of oxidative stress in the bone marrow (BM) and increases haematopoietic cell dysfunction. Our objective was to analyse whether chelation with deferasirox (DFX) alleviates the consequences of oxidative stress and improves BM cell functionality. We analysed 13 iron-overloaded MDS patients' samples before and 4-10 months after treatment with DFX. Using multiparametric flow cytometry analysis, we measured intracellular reactive oxygen species (ROS), DNA oxidation and double strand breaks. Haematopoietic differentiation capacity was analysed by colony-forming unit (CFU) assays. Compared to healthy donors, MDS showed a higher level of intracellular ROS and DNA oxidative damage in BM cells. DNA oxidative damage decreased following DFX treatment. Furthermore, the clonogenic assays carried out before treatment suggest an impaired haematopoietic differentiation. DFX seems to improve this capacity, as illustrated by a decreased cluster/CFU ratio, which reached values similar to controls. We conclude that BM cells from MDS are subject to higher oxidative stress conditions and show an impaired haematopoietic differentiation. These adverse features seem to be partially rectified after DFX treatment.

Hb Palencia: a novel δßδ-type two-way fusion variant with ß-globin-like expression levels.

AIMS: Fusion proteins of unequal recombination events at the ß-globin locus have pathological effect. The haemoglobin (Hb) variants of type Lepore are fusion proteins characterised by ß-like globin chains with a δ-globin (HBD) N-terminus and a ß-globin (HBB) C-terminus, whereas reciprocal products of underlying crossover events hold a HBB N-terminus and HBD C-terminus instead. Finally, Hb Parchman contains a ß-like globin chain with a central HBB fragment and HBD-derived N-termini and C-termini, whereas reciprocal hybrid proteins are as yet unknown. METHODS: The propositus was an 80-year-old Caucasian man, whose HbA1c quantification by HPLC (Variant II turbo) for exclusion of type-2 diabetes revealed an abnormal peak. Haemoglobins were analysed by ion-exchange HPLC (Variant II) and capillary electrophoresis (Sebia Capillarys Flex) and DNA by automatic Sanger sequencing of δ-globin and ß-globin genes. RESULTS: Sequencing showed an HBB-HBD-HBB hybrid gene, with HBD-derived central codons 9-31, and HBB-derived UTRs and complementary coding regions. The corresponding new hybrid haemoglobin (Hb Palencia) is represented at ≈40%, similar to HbA. CONCLUSION: Hb Palencia contains the first globin variant with internal HBD sequences and HBB-derived N-terminal and C-terminal and regulatory sequences. Relative quantity of the new ßδß-type variant suggests transcriptional control by HBB elements and a half-life similar to normal HBB.