Indications and outcome of splenectomy in hematologic disease.

Splenectomy is part of the therapeutic arsenal for benign or malignant hematological disorders that constitute the main indication for elective splenectomy. With the development of minimally invasive approaches, and in particular, laparoscopy, as well as the advent of monoclonal antibody therapy, the indications and the outcomes of splenectomy for hematologic disease have changed in recent years. Nonetheless, splenectomy has its place in hemoglobinopathies and hemolytic diseases, improves thrombocytopenia in refractory immune thrombocytopenic purpura, can reverse sequelae linked to voluminous splenomegaly secondary to myelofibrosis, or can be used for diagnostic purposes or for splenomegaly in lymphoproliferative syndromes.

[HSP70, an erythropoiesis regulator that determines the fate of erythroblasts between death and differentiation]. / HSP70 un régulateur de l'érythropoïèse qui détermine le destin des érythroblastes entre mort et différenciation.

Erythropoiesis is finely regulated by two major cytokines, stem cell factor (SCF) and erythropoietin (Epo). Decrease levels of Epo result in caspase activation and erythroid progenitors apoptosis. However, normal erythroid cell maturation requests caspase activation and cleavage of various caspase substrates, except the erythroid transcription factor GATA-1, that is protected by interaction with the chaperone HSP70 in the nucleus. Therefore, molecular abnormalities associated with decrease of HSP70 expression in the nucleus may result in ineffective erythropoiesis characterized by apoptosis and impaired maturation of erythroid precursors. These findings open new potential targeted therapies for erythroid disorders.

Extensive chronic GVHD is associated with donor blood CD34+ cell count after G-CSF mobilization in non-myeloablative allogeneic PBSC transplantation.

The correlation between the incidence of GVHD and the number of infused CD34(+) cells remains controversial for PBSC transplantation after a reduced-intensity-conditioning (RIC) regimen. We evaluated 99 patients transplanted with an HLA-identical sibling after the same RIC (2-Gy-TBI/fludarabine). Donor and recipient characteristics, donor's blood G-CSF-mobilized CD34(+) cell count, and number of infused CD34(+) and CD3(+) cells were analyzed as risk factors for acute and chronic GVHD There was a trend for an increased incidence of extensive chronic GVHD in the quartile of patients receiving more than 10 × 10(6) CD34(+) cells/kg (P = 0.05). Interestingly, the number of donor's blood CD34(+) cells at day 5 of G-CSF mobilization was closely associated with the incidence of extensive chronic GVHD, that is, 48% (95% CI: 28-68) at 24-months in the quartile of patients whose donors had the highest CD34(+) cell counts versus 24.3% (95% CI: 14-34) in the other patients (P = 0.007). In multivariate analysis, the only factor correlating with extensive chronic GVHD (cGVHD) was the donor's blood CD34(+) cell count after G-CSF (HR 2.49; 95% CI: 1.16-5.35, P = 0.019). This study shows that the incidence of cGVHD is more strongly associated with the donor's ability to mobilize CD34(+) cells than with the number of infused CD34(+) cells.

Overexpression of the heat-shock protein 70 is associated to imatinib resistance in chronic myeloid leukemia.

Imatinib is an effective therapy for chronic myeloid leukemia (CML), a myeloproliferative disorder characterized by the expression of the recombinant oncoprotein Bcr-Abl. In this investigation, we studied an imatinib-resistant cell line (K562-r) generated from the K562 cell line in which none of the previously described mechanisms of resistance had been detected. A threefold increase in the expression of the heat-shock protein 70 (Hsp70) was detected in these cells. This increase was not associated to heat-shock transcription factor-1 (HSF-1) overexpression or activation. RNA silencing of Hsp70 decreased dramatically its expression (90%), and was accompanied by a 34% reduction in cell viability. Overexpression of Hsp70 in the imatinib-sensitive K562 line induced resistance to imatinib as detected by a large reduction in cell death in the presence of 1 muM of imatinib. Hsp70 level was also increased in blast cells of CML patients resistant to imatinib, whereas the level remained low in responding patients. Taken together, the results demonstrate that overexpression of Hsp70 can lead to both in vitro and in vivo resistance to imatinib in CML cells. Moreover, the overexpression of Hsp70 detected in imatinib-resistant CML patients supports this mechanism and identifies potentially a marker and a therapeutic target of CML evolution.

The VAD chemotherapy regimen plus a G-CSF dose of 10 microg/kg is as effective and less toxic than high-dose cyclophosphamide plus a G-CSF dose of 5 microg/kg for progenitor cell mobilization: results from a monocentric study of 82 patients.

A study was conducted to compare the efficiency and toxicity of two peripheral blood stem cell (PBSC) mobilization procedures for newly diagnosed patients with multiple myeloma. Patients from group 1 (n=51) were treated by high-dose cyclophosphamide (HD-CY) plus G-CSF (5 microg/kg/day), and the second group (n=31) by VAD regimen plus G-CSF administration (10 microg/kg/day). Successful mobilization, defined by a minimal count of 2.5 x 10(6) CD34(+) cells/kg collected, was achieved in 96 and 90% of patients in groups 1 and 2, respectively (P=0.15). The mean peripheral blood CD34(+) cells concentration and the mean CD34(+) cells/kg collected were higher in group 2 than in the group 1 (P=0.05). The mean number of leukaphereses necessary to collect a count of 2.5 x 10(6) CD34(+) cells/kg was reduced in group 2 compared to group 1. Adverse events, blood products consumption and time spent in the hospital were significantly greater after HD-CY. In conclusion, VAD plus a G-CSF dose of 10 microg/kg administration seems preferential to HD-CY plus a G-CSF dose of 5 microg/kg for PBSC collection because of equivalent or better efficiency in stem cell mobilization, strong favorable toxicity profile and reduced cost.

[Erythropoiesis: a paradigm for the role of caspases in cell death and differentiation]. / L'erythropoïèse : un paradigme pour l'etude du rôle des caspases dans la mort et la différenciation cellulaire.

Erythroid differentiation involves the transcription factor GATA-1 that positively regulates promoters of erythroid genes (including haemoglobin, glycophorin, erythropoietin receptor) and of erythropoietin. Terminal erythroid differentiation is characterized by major morphological changes that include chromatin condensation and cell size reduction. The morphological changes are partially similar at least to those observed during apoptosis. The production of red cells depends on the apoptosis rate of erythroid progenitors and precursors. Upon erythropoietin starvation or engagement of the death receptor Fas, caspases are activated in erythroid precursors and cleave GATA-1, thus inducing maturation arrest and apoptosis of immature erythroblasts. We have recently demonstrated that, upon erythropoietin stimulation, caspase-3 was also activated, an event required for human terminal erythroblast maturation. Proteins cleaved by caspases in erythroid cells undergoing terminal differentiation include Lamin B and Acinus, which are involved in chromatin condensation. In contrast, despite caspase-3 activation neither GATA-1 degradation nor apoptosis was observed. Thus, the fate of erythroid precursors is determined downstream of caspase activation by the pattern of cleaved targets. Therefore, there are some mechanisms underlying the selective protection of caspase-3 targets during erythropoiesis. This model in which caspases activation is required for differentiation may apply to other haematopoietic or non haematopoietic cellular systems which are described in this review.