Oxidative stress and mitochondrial dysfunction play a role in myelodysplastic syndrome development,diagnosis, and prognosis: A pilot study

Abstract

The imbalance between reactive oxygen species (ROS) production and their elimination by antioxidants leads to oxidative stress. Depending on their concentration, ROS can trigger apoptosis or stimulate cell proliferation. We hypothesized that oxidative stress and mitochondrial dysfunction may participate not only in apoptosis detected in some myelodysplastic syndrome (MDS) patients, but also in increasing proliferation in other patients. We investigated the involvement of oxidative stress and mitochondrial dysfunction in MDS pathogenesis, as well as assessed their diagnostic and prognostic values. Intracellular peroxides, superoxide, superoxide/peroxides ratio, reduced glutathione (GSH), and mitochondrial membrane potential (Δψ_mit) levels were analyzed in bone marrow cells from 27 MDS patients and 12 controls, by flow cytometry. We observed that all bone marrow cell types from MDS patients had increased intracellular peroxide levels and decreased GSH content, compared with control cells. Moreover, oxidative stress levels were MDS subtype— and risk group—dependent. Low-risk patients had the highest ROS levels, which can be related with their high apoptosis; and intermediate-2-risk patients had high Δψ_mit that may be associated with their proliferative potential. GSH levels were negatively correlated with transfusion dependency, and peroxide levels were positively correlated with serum ferritin level. GSH content proved to be an accurate parameter to discriminate patients from controls. Finally, patients with high ROS or low GSH levels, as well as high superoxide/peroxides ratio had lower overall survival. Our results suggest that oxidative stress and mitochondrial dysfunction are involved in MDS development, and that oxidative stress parameters may constitute novel diagnosis and/or prognosis biomarkers for MDS.     

Treatment of poor-risk myelodysplastic syndromes and acute myeloid leukemia with a combination of 5-azacytidine and valproic acid

5-azacytidine (AZA) has become standard treatment for patients with higher-risk myelodysplastic syndrome (MDS). Response rate is about 50% and response duration is limited. Histone deactylase (HDAC) inhibitors are attractive partners for epigenetic combination therapy. We treated 24 patients with AZA (100?mg/m(2), 5?days) plus valproate (VPA; continuous dosing, trough serum level 80-110?μg/ml). According to WHO classification, 5 patients had MDS, 2 had MDS/MPD, and 17 had acute myeloid leukemia (AML). Seven patients (29%) had previously received intensive chemotherapy, and five had previous HDAC inhibitor treatment. The overall response rate was 37% in the entire cohort but significantly higher (57%) in previously untreated patients, especially those with MDS (64%). Seven (29%) patients achieved CR (29%) and two PR (8%), respectively. Hematological CR was accompanied by complete cytogenetic remission according to conventional cytogenetics in all evaluable cases. Some patients also showed complete remission according to FISH on bone marrow mononuclear cells and CD34(+) peripheral blood cells, as well as by follow-up of somatic mitochondrial DNA mutations. Four additional patients achieved at least marrow remissions. Factors influencing response were AML (vs. MDS), marrow blast count, pretreatment, transfusion dependency, concomitant medication with hydroxyurea, and valproic acid (VPA) serum level. This trial is the first to assess the combination of AZA plus VPA without additional ATRA. A comparatively good CR rate, relatively short time to response, and the influence of VPA serum levels on response suggest that VPA provided substantial additional benefit. However, the importance of HDAC inhibitors in epigenetic combination therapy can only be proven by randomized trials.     

Reversal of anemia with allogenic RBC transfusion prevents post-cardiopulmonary bypass acute kidney injury in swine

Anemia during cardiopulmonary bypass (CPB) is strongly associated with acute kidney injury in clinical studies; however, reversal of anemia with red blood cell (RBC) transfusions is associated with further renal injury. To understand this paradox, we evaluated the effects of reversal of anemia during CPB with allogenic RBC transfusion in a novel large-animal model of post-cardiac surgery acute kidney injury with significant homology to that observed in cardiac surgery patients. Adult pigs undergoing general anesthesia were allocated to a Sham procedure, CPB alone, Sham+RBC transfusion, or CPB+RBC transfusion, with recovery and reassessment at 24 h. CPB was associated with dilutional anemia and caused acute kidney injury in swine characterized by renal endothelial dysfunction, loss of nitric oxide (NO) bioavailability, vasoconstriction, medullary hypoxia, cortical ATP depletion, glomerular sequestration of activated platelets and inflammatory cells, and proximal tubule epithelial cell stress. RBC transfusion in the absence of CPB also resulted in renal injury. This was characterized by endothelial injury, microvascular endothelial dysfunction, platelet activation, and equivalent cortical tubular epithelial phenotypic changes to those observed in CPB pigs, but occurred in the absence of severe intrarenal vasoconstriction, ATP depletion, or reductions in creatinine clearance. In contrast, reversal of anemia during CPB with RBC transfusion prevented the reductions in creatinine clearance, loss of NO bioavailability, platelet activation, inflammation, and epithelial cell injury attributable to CPB although it did not prevent the development of significant intrarenal vasoconstriction and endothelial dysfunction. In conclusion, contrary to the findings of observational studies in cardiac surgery, RBC transfusion during CPB protects pigs against acute kidney injury. Our study underlines the need for translational research into indications for transfusion and prevention strategies for acute kidney injury.     

Supportive care including growth factors in myelodysplastic syndromes

In spite of recent advances in the treatment of myelodysplastic syndromes (MDS), supportive care remains a very important part of the therapy. Red blood cells transfusions are the most important component of this supportive care. They transiently relieve anemia symptoms and alleviate their effects on quality of life and daily functioning. Platelet transfusion therapy is less frequently needed, at least in low-risk MDS. Dealing with an increased risk of infections linked to neutropenia, mainly by broad spectrum antibiotics, is also needed, more often in advanced stages of [dict: MDS] or when the MDS evolves to acute myeloid leukemia. Chronic red blood cell transfusions expose patients to various side-effects, including blood components intolerance reactions and alloimmunization risks, but also increased frequency of iron overload, a more significant problem in low-risk heavily transfused MDS patients, who have prolonged life expectancy. The use of growth factors is becoming a more and more important part of current supportive care. High-dose erythropoietin is able to reduce or suppress red blood cell transfusions needs in selected subgroups of MDS. The short-term use of granulocyte colony-stimulating factor is also often proposed in infections, although not formally established by prospective trials. Although trials of growth factors with thrombopoeitic activity have been performed with interleukin 11 and are underway with thrombopoeitin, none of them are available for routine use.     

Pacemaker Dependency after Cardiac Surgery: A Systematic Review of Current Evidence

Background

Severe postoperative conduction disturbances requiring permanent pacemaker implantation frequently occur following cardiac surgery. Little is known about the long-term pacing requirements and risk factors for pacemaker dependency in this population.

Methods

We performed a systematic review of the literature addressing rates and predictors of pacemaker dependency in patients requiring permanent pacemaker implantation after cardiac surgery. Using a comprehensive search of the Medline, Web of Science and EMBASE databases, studies were selected for review based on predetermined inclusion and exclusion criteria.

Results

A total of 8 studies addressing the endpoint of pacemaker-dependency were identified, while 3 studies were found that addressed the recovery of atrioventricular (AV) conduction endpoint. There were 10 unique studies with a total of 780 patients. Mean follow-up ranged from 6–72 months. Pacemaker dependency rates ranged from 32%-91% and recovery of AV conduction ranged from 16%-42%. There was significant heterogeneity with respect to the definition of pacemaker dependency. Several patient and procedure-specific variables were found to be independently associated with pacemaker dependency, but these were not consistent between studies.

Conclusions

Pacemaker dependency following cardiac surgery occurs with variable frequency. While individual studies have identified various perioperative risk factors for pacemaker dependency and non-resolution of AV conduction disease, results have been inconsistent. Well-conducted studies using a uniform definition of pacemaker dependency might identify patients who will benefit most from early permanent pacemaker implantation after cardiac surgery.     

Erectile dysfunction after myocardial infarction--myth or a real problem?

Erectile dysfunction is a common problem whose relation to cardiovascular diseases has scientifically been proved, but it has not been studied sufficiently in patients recovering from myocardial infarction. The objective of this study was to establish the frequency of erectile dysfunction in patients recovering from myocardial infarction. We examined 89 patients (aged 30 to 75 years) included in the program of cardiac rehabilitation after myocardial infarction. The results were compared with 91 healthy examinees of the same age. Even 82% of the patients who recovered from myocardial infarction have problems with erectile dysfunction, compared to 42.9% of healthy examinees. The prevalence of erectile dysfunction increases with the age in both groups. In the group of patients recovering from myocardial infarction aged 30 do 39 years, the erectile dysfunction decreased after 6 months, while in other age subgroups and between controls, there were no significant changes in erectile dysfunction prevalence during the analysed time period. We concluded that erectile dysfunction is a significant problem in patients recovering from myocardial infarction. It should be recognized on time in order to provide a better life quality for the patient with a multidisciplinary approach.     

Hepcidin levels and their determinants in different types of myelodysplastic syndromes

Iron overload may represent an additional clinical problem in patients with Myelodysplastic Syndromes (MDS), with recent data suggesting prognostic implications. Beyond red blood cells transfusions, dysregulation of hepcidin, the key iron hormone, may play a role, but studies until now have been hampered by technical problems. Using a recently validated assay, we measured serum hepcidin in 113 patients with different MDS subtypes. Mean hepcidin levels were consistently heterogeneous across different MDS subtypes, with the lowest levels in refractory anemia with ringed sideroblasts (RARS, 1.43 nM) and the highest in refractory anemia with excess blasts (RAEB, 11.3 nM) or in chronic myelomonocytic leukemia (CMML, 10.04 nM) (P = 0.003 by ANOVA). MDS subtypes remained significant predictors of hepcidin in multivariate analyses adjusted for ferritin and transfusion history. Consistently with current knowledge on hepcidin action/regulation, RARS patients had the highest levels of toxic non-transferrin-bound-iron, while RAEB and CMML patients had substantial elevation of C-Reactive Protein as compared to other MDS subtypes, and showed lost of homeostatic regulation by iron. Growth differentiation factor 15 did not appear as a primary hepcidin regulator in this series. If confirmed, these results may help to calibrate future treatments with chelating agents and/or hepcidin modulators in MDS patients.     

TNF-α Regulates the Effects of Irradiation in the Mouse Bone Marrow Microenvironment

Background

Secondary bone marrow (BM) myelodysplastic syndromes (MDS) are increasingly common, as a result of radio or chemotherapy administered to a majority of cancer patients. Patients with secondary MDS have increased BM cell apoptosis, which results in BM dysfunction (cytopenias), and an increased risk of developing fatal acute leukemias. In the present study we asked whether TNF-α, known to regulate cell apoptosis, could modulate the onset of secondary MDS.

Principal Findings

We show that TNF-α is induced by irradiation and regulates BM cells apoptosis in vitro and in vivo. In contrast to irradiated wild type (WT) mice, TNF-α deficient (TNF-α KO) mice or WT mice treated with a TNF-α-neutralizing antibody were partially protected from the apoptotic effects of irradiation. Next we established a 3-cycle irradiation protocol, in which mice were sub-lethally irradiated once monthly over a 3 month period. In this model, irradiated WT mice presented loss of microsatellite markers on BM cells, low white blood cell (WBC) counts, reduced megakaryocyte (MK) and platelet levels (thrombocytopenia) and macrocytic anemia, phenoypes that suggest the irradiation protocol resulted in BM dysfunction with clinical features of MDS. In contrast, TNF-α KO mice were protected from the irradiation effects: BM cell apoptosis following irradiation was significantly reduced, concomitant with sustained BM MK numbers and absence of other cytopenias. Moreover, irradiated WT mice with long term (≥5 months) BM dysfunction had increased BM angiogenesis, MMPs and VEGF and NFkB p65, suggestive of disease progression.

Conclusion

Taken together, our data shows that TNF-α induction following irradiation modulates BM cell apoptosis and is a crucial event in BM dysfunction, secondary MDS onset and progression.     

The HCM-causing Y235S cMyBPC mutation accelerates contractile function by altering C1 domain structure

Mutations in cardiac myosin binding protein C (cMyBPC) are a major cause of hypertrophic cardiomyopathy (HCM). In particular, a single amino acid substitution of tyrosine to serine at residue 237 in humans (residue 235 in mice) has been linked to HCM with strong disease association. Although cMyBPC truncations, deletions and insertions, and frame shift mutations have been studied, relatively little is known about the functional consequences of missense mutations in cMyBPC. In this study, we characterized the functional and structural effects of the HCM-causing Y235S mutation by performing mechanical experiments and molecular dynamics simulations (MDS). cMyBPC null mouse myocardium was virally transfected with wild-type (WT) or Y235S cMyBPC (KO^Y235S). We found that Y235S cMyBPC was properly expressed and incorporated into the cardiac sarcomere, suggesting that the mechanism of disease of the Y235S mutation is not haploinsufficiency or poison peptides. Mechanical experiments in detergent-skinned myocardium isolated from KO^Y235S hearts revealed hypercontractile behavior compared to KO^WT hearts, evidenced by accelerated cross-bridge kinetics and increased Ca²⁺ sensitivity of force generation. In addition, MDS revealed that the Y235S mutation causes alterations in important intramolecular interactions, surface conformations, and electrostatic potential of the C1 domain of cMyBPC. Our combined in vitro and in silico data suggest that the Y235S mutation directly disrupts internal and surface properties of the C1 domain of cMyBPC, which potentially alters its ligand-binding interactions. These molecular changes may underlie the mechanism for hypercontractile cross-bridge behavior, which ultimately results in the development of cardiac hypertrophy and in vivo cardiac dysfunction.     

Cytogenetic and molecular abnormalities in myelodysplastic syndrome

Myelodysplastic syndrome (MDS) is a heterogeneous group of clonal hematological disorders characterized by ineffective hematopoiesis which causes peripheral cytopenias and a risk of progression to acute myeloid leukemia. Although various forms of chromosomal abnormalities have been detected in approximately 50-60% of patients with de novo MDS and in up to 80% of patients with therapy-related MDS, their molecular significance for pathogenesis and disease progression is not yet fully understood. Recent technical advances in molecular biology have disclosed more accurately details of pathological chromosomal and molecular aberrations in MDS. Such details could not be identified with conventional cytogenetical techniques, including G-banding. In particular, with recent technical advances in comparative genome hybridization or single nucleotide polymorphism array technology, several candidate genes for the pathogenesis of MDS have been identified, which are located in minimally deleted or uniparental disomy segments. Moreover, epigenetic deregulation of gene expression is also likely to be involved in the pathogenesis of MDS. Accordingly, in addition to classical oncogenic abnormalities, such as p53 abnormalities, or NRAS mutation, various molecular abnormalities, such as TET2, RPS14, or c-CBL, have been identified and/or proposed as the novel candidates for molecular basis of the development and progression of MDS. A better understanding of the causative molecular events underlying MDS pathogenesis is essential for the development and establishment of a more effective treatment resulting in a complete cure for MDS. We here review current knowledge regarding the molecular significance of chromosomal and genetic aberrations in MDS and the proposed molecular mechanisms of action of new agents for MDS, such as lenalidomide or azacitidine.     

Adoptive transfer of neoantigen-specific T-cell therapy is feasible in older patients with higher-risk myelodysplastic syndrome

BackgroundMyelodysplastic syndromes (MDS) represent the most common type of acquired bone marrow failure in adults and is characterized by ineffective maturation of myeloid precursor cells and peripheral cytopenias associated with higher rates of infection, bleeding and transfusion dependence. In higher-risk patients with MDS who relapse or do not respond after standard hypomethylating agent (HMA) therapy, the 2-year survival rate is 15%.MethodsHere the authors report the feasibility and safety of a novel experimental T-cell therapy called personalized adoptive cell therapy, which selects, immunizes and expands T cells against MDS-specific mutations and is targeted to patient-specific tumor cell neoantigens. Somatic mutations serve as the pathogenic drivers of cancer, including MDS, as these transformative genetic mutations may generate novel immunogenic proteins (i.e., neopeptides and possible neoantigens) that may be targeted therapeutically.ResultsThe authors demonstrate that the adaptive immune system can be trained ex vivo to recognize neopeptides as neoantigens and that the infusion of culture-expanded, neoantigen-immunized autologous T cells has been feasible and safe in the three patients treated to date.DiscussionThe authors report on early results from their first-in-human phase 1 clinical trial that aims to assess the safety and tolerability of this novel form of adoptive T-cell immunotherapy for HMA-refractory patients with higher-risk MDS.     

Bone marrow macrophages are involved in the ineffective hematopoiesis of myelodysplastic syndromes

Myelodysplastic syndromes (MDS) are a group of heterogeneous myeloid clonal disorders characterized by ineffective hematopoiesis. Accumulating evidence has shown that macrophages (MΦs) are important components in the regulation of tumor progression and hematopoietic stem cells (HSCs). However, the roles of bone marrow (BM) MΦs in regulating normal and malignant hematopoiesis in different clinical stages of MDS are largely unknown. Age-paired patients with lower-risk MDS (N = 15), higher-risk MDS (N = 15), de novo acute myeloid leukemia (AML) (N = 15), and healthy donors (HDs) (N = 15) were enrolled. Flow cytometry analysis showed increased pro-inflammatory monocyte subsets and a decreased classically activated (M1) MΦs/alternatively activated (M2) MΦs ratio in the BM of patients with higher-risk MDS compared to lower-risk MDS. BM MФs from patients with higher-risk MDS and AML showed impaired phagocytosis activity but increased migration compared with lower-risk MDS group. AML BM MΦs showed markedly higher S100A8/A9 levels than lower-risk MDS BM MΦs. More importantly, coculture experiments suggested that the HSC supporting abilities of BM MΦs from patients with higher-risk MDS decreased, whereas the malignant cell supporting abilities increased compared with lower-risk MDS. Gene Ontology enrichment comparing BM MΦs from lower-risk MDS and higher-risk MDS for genes was involved in hematopoiesis- and immunity-related pathways. Our results suggest that BM MΦs are involved in ineffective hematopoiesis in patients with MDS, which indicates that repairing aberrant BM MΦs may represent a promising therapeutic approach for patients with MDS.     

Cytogenetic characteristics of patients with signs and symptoms of myelodysplastic syndromes in the State of Pará, Brazil

The myelodysplastic syndromes (MDS) are clonal hematopoietic diseases characterized by medullary dysplasia, cytopenias, and frequent evolution to acute myeloid leukemia. In 1982, the French-American-British (FAB) group proposed a classification for the MDS, based on morphological characteristics of peripheral blood and of the bone marrow. Later, cytogenetics proved to be a useful tool for the refinement of prognosis, through the use of the International Prognosis Score System (IPSS), as well as through evidence of clonality. Recently, the World Health Organization (WHO) proposed a new classification for the MDS, based on significant modifications of the FAB proposal, with the inclusion of chromosome analysis. A cytogenetic analysis was made of 17 patients with symptoms of MDS in the State of Para, based on WHO recommendations, and application of the IPSS. Good metaphases were obtained for 13 patients; 12 had a normal karyotype and only one had a clonal abnormality, del(3)(p25). The genes related to neoplastic processes that have been mapped to 3p are: XPC in 3p25.1 and FANCD2 and VHL in 3p25-26. Four patients had classic symptoms of MDS; in the rest the possibility of MDS was excluded or several months of observation before diagnosis were recommended. Among those with MDS, it was not possible to apply IPSS and WHO recommendations, because fundamental data were lacking, specifically the medullary blast and ring sideroblast counts. We advocate the implementation of routine cytogenetic analyses for the study of MDS, especially in patients with moderate hematopoietic dysplasia.     

超快通道麻醉联合BIS监测对心脏手术患者的效果及安全性

目的:探究超快通道麻醉辅助脑电双频指数(Bispectral index,BIS)监测对行心脏手术患者认知功能障碍的影响和安全性。方法:选取2014年1月-2017年1月于我院进行心脏手术的59例患者为研究对象,按照随机数字表法将其分为实验组(29例)和对照组(30例)。其中,对照组患者实施心脏超快通道麻醉,实验组患者实施心脏超快通道麻醉辅助BIS监测。术后6个月,使用韦氏成人智力量表对两组麻醉前后认知功能障碍情况进行比对,并比较两组术后6个月内并发症的发生率。结果:(1)两组术后6个月时智力测试得分对比差异无统计学意义(P0.05),各指数间对比差异也无统计学意义(P0.05);(2)实验组患者术后6个月内并发症发生率较对照组显著降低(P0.05)。结论:与单独使用超快速通道的患者相比,行全身麻醉心脏手术患者使用超快速通道麻醉辅助BIS监测麻醉及单用超快速通道对患者认知功能障碍的影响相当,但前者的安全性明显高于后者。     

Improvement of iron-mediated oxidative DNA damage in patients with transfusion-dependent myelodysplastic syndrome by treatment with deferasirox

Myelodysplastic syndrome (MDS) is characterized by dysplastic and ineffective hematopoiesis, peripheral blood cytopenias, and a risk of leukemic transformation. Most MDS patients eventually require red blood cell (RBC) transfusions for anemia and consequently develop iron overload. Excess free iron in cells catalyzes generation of reactive oxygen species that cause oxidative stress, including oxidative DNA damage. However, it is uncertain how iron-mediated oxidative stress affects the pathophysiology of MDS. This study included MDS patients who visited our university hospital and affiliated hospitals (n=43). Among them, 13 patients received iron chelation therapy when their serum ferritin (SF) level was greater than 1000ng/mL or they required more than 20 RBC transfusions (or 100mL/kg of RBC). We prospectively analyzed 8-hydroxy-2'-deoxyguanosine (8-OHdG) levels in peripheral blood mononuclear cells (PBMC) obtained from MDS patients before and after iron chelator, deferasirox, administration. We showed that the 8-OHdG levels in MDS patients were significantly higher than those in healthy volunteers and were positively correlated with SF and chromosomal abnormalities. Importantly, the 8-OHdG levels in PBMC of MDS patients significantly decreased after deferasirox administration, suggesting that iron chelation reduced oxidative DNA damage. Thus, excess iron could contribute to the pathophysiology of MDS and iron chelation therapy could improve the oxidative DNA damage in MDS patients.     

Role of the activation gate in determining the extracellular potassium dependency of block of HERG by trapped drugs

Drug induced long QT syndrome (diLQTS) results primarily from block of the cardiac potassium channel HERG (human-ether-a-go-go related gene). In some cases long QT syndrome can result in the lethal arrhythmia torsade de pointes, an arrhythmia characterized by a rapid heart rate and severely compromised cardiac output. Many patients requiring medication present with serum potassium abnormalities due to a variety of conditions including gastrointestinal dysfunction, renal and endocrine disorders, diuretic use, and aging. Extracellular potassium influences HERG channel inactivation and can alter block of HERG by some drugs. However, block of HERG by a number of drugs is not sensitive to extracellular potassium. In this study, we show that block of WT HERG by bepridil and terfenadine, two drugs previously shown to be trapped inside the HERG channel after the channel closes, is insensitive to extracellular potassium over the range of 0 mM to 20 mM. We also show that bepridil block of the HERG mutant D540K, a mutant channel that is unable to trap drugs, is dependent on extracellular potassium, correlates with the permeant ion, and is independent of HERG inactivation. These results suggest that the lack of extracellular potassium dependency of block of HERG by some drugs may in part be related to the ability of these drugs to be trapped inside the channel after the channel closes.     

A systematic modeling study on the pathogenic role of p38 MAPK activation in myelodysplastic syndromes

Myelodysplastic syndromes (MDS) are a group of clonal hematopoietic stem cell diseases. In addition to intrinsic genetic alterations, the effects of the extrinsic microenvironment also play a pathological role in MDS development. The presence of increased inflammatory cytokines, such as tumor necrosis factor-alpha (TNF-α), in marrow and abnormal activation of the p38 mitogen-activated protein kinase (MAPK) signaling pathway in hematopoietic cells are associated with the ineffective hematopoiesis in MDS. However, the molecular mechanism of p38 MAPK activation triggered by microenvironment cytokines remains poorly understood. To address this question, we combined computational modeling analysis and molecular biology studies to perform a systematic investigation of signaling events regulated by microenvironment cytokines in hematopoietic cells from MDS patients. We examined dynamic changes of key signaling events, including the p38 MAPK and the c-Jun N-terminal kinase (JNK) pathway in bone marrow mononuclear cells from MDS patients or normal donors in response to TNF-α stimulation using reverse phase protein array technology. The results were analyzed by a novel computational model and preliminarily validated by immunohistochemistry analysis of the bone marrow tissues from twelve MDS patients and normal donors. Our systematic model revealed that the dynamic response patterns of p38 MAPK and JNK to TNF-α stimulation in MDS were different from that observed in normal marrow cells. Particularly, B-cell lymphoma-X (BCL-XL) protein degradation was regulated by the JNK pathway in normal cells, but by p38 MAPK in MDS cells. By immunohistochemistry, BCL-XL was highly expressed in hematopoietic cells from normal marrow, but was minimally expressed in MDS marrow. Additionally, immunostaining for phosphorylated p38 MAPKα showed much higher p38 MAPK activation in MDS marrows, supporting over-activation of p38 MAPK-enhanced degradation of BCL-XL in MDS. The degradation of BCL-XL triggered by p38 MAPK over-activation may contribute to the increasing apoptosis of marrow cells, a phenomenon commonly observed in MDS, and lead to ineffective hematopoiesis. Our study suggests that the combination of molecular biological studies and systematic modeling is a powerful tool for comprehensive investigation of the complex cellular mechanisms involved in MDS pathogenesis.     

The Nonsteroidal Anti-Inflammatory Drug Exisulind Selectively Induces Apoptosis via JNK in Secondary Acute Myeloid Leukemia after Myelodysplastic Syndrome

Treatment of patients suffering from myelodysplastic syndromes and secondary acutemyeloid leukemia after MDS is often unsuccessful. Pro-apoptosis with arsenic trioxide hasrecently been proposed as a novel therapeutic approach. Exisulind is another potentially proapoptoticagent, and therefore, we investigated its influence on proliferation, differentiation,cell cycle and apoptosis in two sAML/MDS cell lines, one de-novo AML cell line and healthyCD34+ bone marrow cells. Treatment of sAML/MDS cells with Exisulind clearly inhibitedcolony formation in the CFU-assays. Interestingly, Exisulind did not alter the percentages ofsAML/MDS cells in G1-, G2-, M- or S-phase, but reduced proliferation and inducedapoptosis in this cell type. Exisulind had no effect on de-novo AML or normal CD34+ cells.We detected increased c-Jun NH2-terminal kinase activity in sAML/MDS cells treated withExisulind. Adding a specific JNK-inhibitor to Exisulind-treated sAML/MDS cells partiallyabrogated apoptosis, thus proving that Exisulind-mediated apoptosis in sAML/MDS cells isdependent on JNK activation. We conclude that JNK is one mediator of apoptosis insAML/MDS cells treated with Exisulind. Moreover, our data strongly suggests to explore thepotential use of Exisulind as a novel, pro-apoptotic therapy for patients with MDS andsAML/MDS.