Systemic mastocytosis and bone involvement in a cohort of 75 patients.

OBJECTIVES: To investigate bone involvement in a large cohort of systemic mastocytosis (SM) patients, and evaluate the efficacy of bisphosphonate therapy. PATIENTS AND METHODS: From 2000 to 2004, 75 patients with SM according to WHO criteria underwent skeletal x-rays and bone mineral density (BMD) assessment. Sequential BMD assessments were performed in nine patients treated with bisphosphonate (mean follow-up 65 months). RESULTS: 37 patients (49%) had bone involvement according to both x-rays and BMD evaluations: osteoporosis (23 patients, 31%, mean lumbar spine T score: -3 SD), with vertebral fracture (13 patients, 17%), axial skeleton osteosclerosis (six patients, 8%), mixed patterns (three patients), osteopenia with pre-existing fractures (four patients) and focal osteolytic lesion (one patient). Blood count abnormalities were associated with osteosclerosis (p=0.005). In nine patients with osteoporosis and bisphosphonate therapy, mean lumbar spine BMD increased from 0.83 to 0.92 g/cm(2) (+11.1%; ie, +2.05% per year) without recurrence of vertebral fracture. CONCLUSION: Half of adult patients with SM have bone involvement. Osteoporosis is the most prevalent bone manifestation in SM (31%). Bisphosphonate therapy seems efficient to improve lumbar spine BMD during SM-related osteoporosis. Spine x-ray and BMD should be performed in all SM patients to detect those who may benefit from anti-osteoporotic therapy.

[Applications of molecular biology to care of patients with malignant hematological disease]. / Applications de la biologie moléculaire dans la prise en charge des hémopathies malignes.

The improvement of the techniques of molecular biology allowed greater performances in the field of detection and characterization of chromosomal abnormalities and/or molecular defects observed in human hematological malignancies. Cytological and immunophenotypical results are reinforced by data obtained with standard and molecular cytogenetic tools and with PCR based techniques. Molecular data are usefull at diagnosis in order to define different types of leukemias and to score patient prognosis. Therefore, these techniques help to choose among various therapeutic options. In post induction treatment period, PCR tools allowed to measure minimal residual disease (MRD) and to distinguish new prognosis factors essential for patient's management.

Mast cells as a source and target for nitric oxide.

Mast cells (MC), which are tissue-resident cells found widely distributed in the body, are derived from primitive hematopoietic cells. MC produce a variety of biologically active substances such as histamine, proteases, lipid derivatives and numerous cytokines and chemokines in response to immunologic or non-immunologic stimuli. Of interest, it has been reported that rodent MC can also be a source of nitric oxide (NO) derivatives, that they synthesize spontaneously, or only after activation, depending on their subtype. This synthesis appears to be under the control of the expression of the inducible isoform of the nitric oxide synthase (iNOS) and of the constitutive neuronal NOS (nNOS). MC might thus be able to influence the survival and functions of other types of NO-sensitive cells in close vicinity. Apart from being a source of NO, MC can also be the target for NO and its derivatives. Indeed, survival and reactivity of rodent MC is influenced by NO derivatives produced by MC themselves or by other cellular elements in close contact with the MC in tissues. By contrast, the existence of such mechanisms of cross-talk between MC and NO remains poorly documented in humans. If evidence are supplied in favor of such relationship, pharmacological modulation by agents acting at the level of the NO pathway might be of interest in order to regulate the functions of MC in immunologic, neoplastic, inflammatory and other conditions.

Autocrine regulation of cord blood-derived human mast cell activation by IL-10.

BACKGROUND: Ligation of the high-affinity receptor for IgE on human mast cells (MCs) induces the release of proinflammatory mediators, including vasoactive amines and cytokines (TNF-alpha, IL-5, and IL-8). Moreover, we have recently shown that IL-10 inhibits the release of proinflammatory mediators by activated MCs. OBJECTIVE: We investigated whether human cord blood-derived MCs (CBMCs) could produce IL-10 and whether this production could inhibit their activation in an autocrine fashion. METHODS: IL-10 synthesis by resting or activated human MCs derived from cord blood progenitors was investigated in cell supernatants or by using immunostaining and RT-PCR methods. In addition, the effect of IL-4 on such synthesis was also studied. Anti-IL-10-neutralizing antibodies were used to investigate the validity of the hypothesis of an autocrine regulation of MCs by IL-10. Finally, the presence of specific receptors for IL-10 was searched on human CBMCs by using flow cytometric analysis. RESULTS: Human CBMCs spontaneously synthesize and release IL-10, and this synthesis is increased after IgE/anti-IgE stimulation. In addition, the presence of IL-10 in resting or in activated MCs was proved by immunostaining. Interestingly, the release of IL-10 was also increased after incubation of the cells with IL-4. Besides, the use of neutralizing antibodies against IL-10 confirmed that IL-10 released inhibited MC activation in an autocrine fashion. Finally, the presence of specific receptors for this cytokine was observed on the membranes of our population of human CBMCs. CONCLUSION: Taken together, our data are in favor of an autocrine regulation pathway through synthesis and release of IL-10 by human MCs. Such an autoregulatory mechanism is, to our knowledge, the first described for these elements.

Role of iron in tumor cell protection from the pro-apoptotic effect of nitric oxide.

F2The host defense against tumor cells is in part based upon the production of nitric oxide (NO) by activated macrophages. However, carcinogenesis may involve mechanisms that protect tumor cells from NO-mediated apoptosis. In the present study, we have assessed the effects of exogenous NO on the proliferation and survival of human liver (AKN-1), lung (A549), skin (HaCat), and pancreatic (Capan-2) tumor cell lines, compared with normal skin-derived epithelial cell cultures. Except to the HaCat cell line, all of the other human epithelioid cells were sensitive to the antiproliferation effect of S-nitroso-N-acetyl-penicillamine or Deta NONOate, whereas tumor cells had low if any response to sodium nitroprusside. Growth inhibition with exogenous NO correlated with increased apoptosis, but was not mediated by cyclic GMP, peroxynitrite generation, or poly(ADP-ribose) polymerase modulation, all of which involved in NO-mediated growth inhibition of normal skin-derived epithelial cell cultures. The simultaneous addition of iron-containing compounds protected tumor cells from NO-mediated growth inhibition and apoptosis. Intracellular iron quantification indicated that, as deferoxamine, exogenous NO significantly decreased intracellular ferric iron levels in tumor cells. Together, the current study reveals that intracellular iron elevation rescues tumor cells from NO-mediated iron depletion and subsequent growth inhibition and apoptosis.

c-Kit and c-kit mutations in mastocytosis and other hematological diseases.

Mast cells (MC) are tissue elements derived from hematopoietic stem cells. Their differentiation and proliferation processes are under the influence of cytokines, including one of utmost importance known as stem cell factor (SCF). SCF receptor is encoded by the protooncogene c-kit, belongs to the type III receptor tyrosine kinase subfamily, and is also expressed on other hematopoietic or non-hematopoietic cells. Ligation of c-kit receptor by SCF induces its dimerization, followed by induction of multiple intracellular signaling pathways leading to cell proliferation and activation. Mastocytosis, a relatively rare group of diseases characterized by accumulation of MC in various tissues, are found isolated or sometimes associated with other hematological malignancies in humans. Although the initial events leading to mastocytosis are not yet unraveled, alterations of the c-kit gene have been described. Particularly interesting are acquired mutations resulting in a constitutively activated receptor, possibly involved in the increased numbers of MC in tissues. For this reason, future strategies might be envisaged to target specifically the mutated c-kit and/or its intracellular signaling.

Inhibition of erythroid differentiation and induction of megakaryocytic differentiation by thrombopoietin are regulated by two different mechanisms in TPO-dependent UT-7/c-mpl and TF-1/c-mpl cell lines.

Thrombopoietin (TPO) regulates megakaryocytic (MK) maturation and platelet production. Molecular and cellular mechanisms of the TPO-induced MK differentiation are not totally understood. In order to develop cellular models to study these mechanisms, we introduced c-mpl into UT-7 and TF-1 cells by means of a retroviral vector and compared the effects of TPO on these two cell lines. UT-7 and TF-1 cell lines are two factor-dependent leukemic cell lines with an erythroid and MK phenotype. They proliferate in response to IL-3, GM-CSF and EPO, but not to TPO. The erythroid differentiation of both cell lines can be markedly increased by EPO. Several UT-7/c-mpl and TF-1/c-mpl cell clones which express different levels of the c-mpl protein (Mpl) were obtained and all became TPO-dependent for their proliferation. The UT-7/c-mpl clones, but not the TF-1/c-mpl clones, were capable of undergoing MK differentiation in response to TPO. This was demonstrated by the increase in MK markers (GPIIb, GPIIIa, GPIb alpha, GPIX and vWF), the appearance of cytoplasmic alpha-granules, intracellular membranes resembling demarcation membranes which were immunologically labeled with an GPIIb/IIIa anti-antibody, and a small percentage of polyploid cells (8N and 16N). In contrast, TPO inhibited the erythroid program of differentiation (glycophorin A, beta-globin and EPO receptor) as well as the differentiative activity of EPO in both UT-7/c-mpl and TF-1/c-mpl clones. It is noteworthy that the differentiative effect of EPO in TF-1/c-mpl cells was associated with an increase in GATA-1 transcripts which was totally suppressed by TPO. Overall the effects of TPO are the same as those of phorbol myristate acetate (PMA) which also induces MK differentiation and inhibits erythroid differentiation. These results suggest that: (1) Mpl expression is necessary but not sufficient for induction of MK differentiation; and (2) induction of Mk differentiation and inhibition of erythroid differentiation by TPO involve different signaling pathways; the pathway involved in the inhibition of erythroid differentiation might be related to a downregulation of GATA-1 expression in TF-1 cells.

Evolution and significance of circulating procalcitonin levels compared with IL-6, TNF alpha and endotoxin levels early after thermal injury.

To determine the evolution and significance of circulating procalcitonin (ProCT), IL-6 TNF alpha and endotoxin levels early after thermal injury, we performed a prospective, single unit, longitudinal study. Forty burn patients with total body surface area (TBSA) > 30 per cent were studied, of whom 33 suffered an inhalation injury. Blood samples were taken on the day of admission, every 4 h during the first day and daily during the first week. All patients had increased ProCT and IL-6 levels without any proven infection. Endotoxin and TNF alpha levels remained very low or undetectable. ProCT and IL-levels correlated well with the severity of skin burn injury (respectively, p < 0.006 and p < 0.028, using the non-parametric Kruskal-Wallis test). ProCT levels are not associated with smoke inhalation. ProCT and IL6 are prognostic factors of mortality at the time of admission but less reliable than the clinical UBS (unit burn standard) score. Endotoxin and TNF alpha were undetectable, suggesting that the problem of the early gut bacterial translocation remains to be proven.

Ectopic expression of the erythropoietin receptor in a murine interleukin-6-dependent plasmacytoma cell line (TEPC-2027) confers proliferative responsiveness to erythropoietin.

To compare the signal transduction pathways used by erythropoietin (Epo) and interleukin-6 (IL-6), the cDNA for the murine Epo receptor (Epo-R) was introduced into an IL-6-responsive plasmacytoma cell line (TEPC-2027) by retrovirally mediated gene transfer. G418-resistant clones were amplified in IL-6 and studied for their ability to grow and differentiate in response to Epo. Epo-R synthesized from the viral gene showed the same affinity for Epo as did the receptor on erythroid cells; however, the numbers of Epo receptors expressed on the cell membrane varied among clones. After a delay of 3 to 5 days in the presence of Epo, all the clones studied proliferated as well in response to Epo as in response to IL-6. In response to IL-6, Stat3 was activated and JunB mRNA was accumulated, whereas in response to Epo, Jak2 and Stat5 were activated and JunB mRNA was not accumulated in Epo-R-expressing TEPC (Epo-R/TEPC) cells. These results suggest that Epo and IL-6 transduced their proliferative signals through different pathways. Further studies showed that, in Epo-R/TEPC cells, Epo neither induces the synthesis of erythroid-specific mRNA nor modifies the synthesis of gamma 1 lg heavy chain, suggesting that ectopic expression of the Epo-R in plasmacytoma cells does not modify their differentiative potential. The data show that Epo induces a proliferative response without differentiation providing a new cellular model for evaluating molecular events specific for proliferation.

Missense mutation of the erythropoietin receptor is a rare event in human erythroid malignancies.

Human erythroid malignancies (polycythemia vera [PV] and erythroleukemia) are associated with erythropoietin (Epo)-independent growth and differentiation. Missense or nonsense mutations in the Epo receptor (Epo-R) have been recently described in experimental erythroleukemia in mice and in cases of erythrocytosis in humans. To search for a similar genetic alteration in erythroleukemia and PV, we entirely sequenced the exons of the Epo-R gene as well as the intron-exon junctions in these disorders using polymerase chain reaction. In 1 of 10 cases of erythroleukemia, a single allele mutation was found in the 8th Epo-R gene exon that changed asparagine 487 into a serine. No Epo-r gene mutation was found in 12 PV cases studied, but the same mutation (N487S) was found in 1 patient with polycythemia that did not fulfill the criteria of PV (polycythemia of unknown origin). We did not detect this mutation after sequencing part of the 8th exon of the Epo-R gene from 21 other patients with polycythemia of unknown origin and 51 normal controls. The Epo-R mutation was also found in Epstein-Barr virus-derived cell lines from both cases, suggesting that it is not related to the malignant clone. Therefore, this mutation does not appear to be somatic, although no familial cases were found. The biologic effect of this mutation was subsequently studied. Erythroid progenitors from the polycythemic patient normally responded to Epo, whereas those from the erythroleukemic patient were Epo-independent due to autocrine stimulation by Epo. The normal and the mutated Epo-R were transfected into the murine Ba/F3 cell line. Both types of cells displayed the same response to Epo for proliferation, differentiation, and inhibition of apoptosis. Although this mutation may destroy a consensus binding site for Grb2, no obvious differences either in the pattern of Epo-induced tyrosine phosphorylated proteins or in the binding of Grb2 to the Epo-R were observed. In conclusion, a somatic Epo-R missense mutation does not appear to be a molecular mechanism involved in the abnormal growth of human erythroleukemia and PV. However, the Epo-R mutation (N487S) that we describe is located in the same tyrosine sequence beginning at AA 485 as the one previously observed (P488S) in as case of polycythemia (Sokol et al, Exp Hematol 22:447, 1994). These results suggest that this phosphopeptide sequence may play an important role in Epo signalling.

Murine pluripotent hematopoietic progenitors constitutively expressing a normal erythropoietin receptor proliferate in response to erythropoietin without preferential erythroid cell differentiation.

Erythropoietin (EPO) is a prime regulator of the growth and differentiation of erythroid blood cells. The EPO receptor (EPO-R) is expressed in late erythroid progenitors (mature BFU-E and CFU-E), and EPO induces proliferation and differentiation of these cells. By introducing, with a retroviral vector, a normal EPO-R cDNA into murine adult bone marrow cells, we showed that EPO is also able to induce proliferation in pluripotent progenitor cells. After 7 days of coculture with virus-producing cells, bone marrow cells were plated in methylcellulose culture in the presence of EPO, interleukin-3, or Steel factor alone or in combination. In the presence of EPO alone, EPO-R virus-infected bone marrow cells gave rise to mixed colonies comprising erythrocytes, granulocytes, macrophages and megakaryocytes. The addition of interleukin-3 or Steel factor to methylcellulose cultures containing EPO did not significantly modify the number of mixed colonies. The cells which generate these mixed colonies have a high proliferative potential as shown by the size and the ability of the mixed colonies to give rise to secondary colonies. Thus, it appears that EPO has the same effect on EPO-R-expressing multipotent cell proliferation as would a combination of several growth factors. Finally, our results demonstrate that inducing pluripotent progenitor cells to proliferate via the EPO signaling pathway has no major influence on their commitment.