Suneel D. Mundle

Measurement of apoptosis, proliferation and three cytokines in 46 patients with myelodysplastic syndromes

Extensive apoptosis or programmed cell death (PCD) of both hematopoietic (erythroid, myeloid, megakaryocytic) and stromal cells in myelodysplastic syndromes (MDS) cancels the high birth-rate resulting in ineffective hematopoiesis and has been demonstrated as the probable basis for peripheral cytopenias in MDS by our group. It is proposed that factors present in the microenvironment are inducing apoptosis in all the cells whether stromal or parenchymal. To investigate this hypothesis further, bone marrow biopsies from 46 MDS patients and eight normal individuals were examined for the presence of three cytokines, tumor necrosis factor-alpha (TNF-alpha), transforming growth factor-beta (TGF-beta) and granulocyte macrophage-colony stimulating factor (GM-CSF) and one cellular component, macrophages, by the use of monoclonal antibodies immunohistochemically. Results showed the presence of TNF-alpha and TGF-beta in 41/46 and 40/46 cases of MDS respectively, while only 15 cases showed the presence of GM-CSF. Further a significant direct relationship was found between the degree of TNF-alpha and the incidence of PCD (p= 0.0015). Patients who showed high PCD also had an elevated TNF-alpha level. Thus, the expression of high amounts of TNF-alpha and TGF-beta and low amounts of the viability factor GM-CSF may be responsible for the high incidence of PCD leading to ineffective hematopoiesis in MDS. Future studies will be directed at attempting to reverse the lesion in MDS by using anti-TNF-alpha drugs such as pentoxifylline.

Erythropoiesis-stimulating agents in the treatment of anemia in myelodysplastic syndromes: a meta-analysis

The present meta-analysis was undertaken to (1) assess erythroid response rates in myelodysplastic syndromes (MDS) patients treated with epoetin alfa as a monotherapy, (2) gain further insights into predictors of response rates, and (3) compare the erythroid response rates observed with epoetin alfa and darbepoetin alfa. A systematic review of studies from 1990 to 2006 in MDS patients treated with epoetin alfa or darbepoetin alfa was performed and yielded 30 studies evaluating a total of 1,314 patients (epoetin alfa: 22 studies, 925 patients; darbepoetin alfa: eight studies, 389 patients). Pooled estimates of erythroid response rates, stratified by the International Working Group criteria (IWGc) and treatment group, were calculated using random-effects meta-analysis methods. Univariate meta-regression analyses were further conducted to identify study characteristics associated with erythroid response rate. The pooled estimate of erythroid response rate was significantly higher for epoetin alfa IWGc studies (57.6%) as compared to non-IWGc studies (31.6%; p < 0.001). Study factors predictive of higher response rate in the epoetin alfa IWGc studies included higher proportion of patients with RA/RARS (p < 0.001), lower mean baseline serum erythropoietin level (p = 0.007), and fixed dosing regimen (p < 0.001). There was no significant difference in the pooled erythroid response rates between the two agents (epoetin alfa: 57.6% vs. darbepoetin alfa: 59.4%; p = 0.828). The current study reported significantly higher erythroid response rates predominantly in the more recent studies that primarily utilized IWGc to define response. With the use of standardized patient selection and response evaluation methods, epoetin alfa and darbepoetin alfa yielded comparable erythroid response rates in MDS patients.

Evolving intricacies and implications of E2F1 regulation

E2F transcription factors may play a pivotal role in the transcriptional regulation of several cellular processes far beyond the originally described cell cycle and proliferation. Among the six E2F family members, only E2F1 is noted for its role in apoptosis. The pocket protein family members Rb, p107, and p130 act as the main regulators of E2F activity. Nonetheless, in recent years other protein‐protein interactions have been described for E2Fs. The post‐translational modifications resulting from such protein interactions may have significant implications in the stability, half‐life, and functional activity of E2Fs. In human diseases the significance of E2Fs is still under appreciated and is primarily recognized only as a consequence of the impairment in retinoblastoma gene product (Rb). However, with increasing knowledge of other protein interactions, the derailment of E2F activity could be anticipated to stem from an abnormality of any node in the complex network governing their availability and activity. The present review is intended to provide a perspective on the diversity of biochemical mechanisms underlying abnormal E2F expression and activity, understanding of which may have significant clinical implications.

Biological significance of proliferation, apoptosis, cytokines, and monocyte/macrophage cells in bone marrow biopsies of 145 patients with myelodysplastic syndrome.

Labeling index (LI), apoptosis, levels of 2 pro-apoptotic cytokines tumor necrosis factor-α (TNF-α) and transforming growth factor-β (TGF-β), and the number of monocyte/macrophage cells that are the likely source of the cytokines were simultaneously measured in plastic-embedded bone marrow (BM) biopsy sections of 145 patients with myelodysplastic syndromes (MDS). TNF-α was correlated with TGF-β (P = .001) and with monocyte/macrophage cells (P = .003). Patients with excess blasts in their marrows had a higher TGF-β level (P = .01) and monocyte/macrophage number (P = .05). In a linear regression model, TGF-β emerged as the most significant biological difference between patients who have excess of blasts and those who do not (P = .01). We conclude that in addition to TNF-α, TGF-β also plays a significant role in the initiation and pathogenesis of MDS, and that a more precise definition of its role will likely identify better preventive and therapeutic strategies.

Correlation of tumor necrosis factor α (TNFα) with high Caspase 3-like activity in myelodysplastic syndromes

Increased intramedullary apoptotic death of hematopoietic cells is thought to contribute to the ineffective hematopoiesis in myelodysplastic syndromes (MDS). Furthermore, high amounts of tumor necrosis factor α (TNFα) have previously been correlated with apoptosis in MDS marrows. The present studies were undertaken to examine the status of two key downstream effectors of TNFα signaling, i.e. Caspase 1 and Caspase 3 enzymes, using a fluorometric assay in the bone marrow aspirate mononuclear cells (BMMNC) in relation to apoptotic DNA fragmentation detected by in situ end-labeling (ISEL) of DNA and with localization of TNFα in the corresponding biopsies from 14 MDS patients. Both Caspase 1 and 3 were detectable in freshly harvested BMMNC, albeit median Caspase 3 levels (47.5 units/mg protein) being almost 10 times higher than Caspase 1 (4.0 units/mg protein). Upon short-term culture for 4 h in a serum-supplemented medium in vitro a significant increase was seen in Caspase 3 activity (58.8±13.9 at 0 h vs. 177.8±55.2 units/mg protein at 4 h, n=14, P=0.017) and in percent cells labeled by ISEL (apoptotic index or AI%: 0.76%±0.25% vs. 3.99%±1.1%, n=14, P=0.004, respectively). Caspase 1 activity increased after 15 min in culture. Interestingly, TNFα levels measured by immunohistochemistry correlated with the net increase in Caspase 3 activity after 4 h (ρ=0.517, n=13, P=0.07) and the starting levels of Caspase 1 at 0 h correlated with the Caspase 3 levels attained at 4 h (ρ=0.593, n=13, P=0.033). Additionally when TNFα-positive bone marrows (8/14) were compared with the negative marrows (6/14) the Caspase 3 levels were significantly higher in the TNFα-positive marrows (189.6±66.2 vs. 25.0±14.6 units/mg protein, respectively, P=0.043). The increase in AI%, though not statistically significant, was also higher in the TNFα-positive marrows. Finally in HL60 cells the effects of different Caspase inhibitors and pentoxifylline (PTX) (interferes with lipid signaling of cytokines) on TNFα-induced apoptosis were evaluated. TNFα treatment significantly increased AI% (P<0.003) as compared to the untreated controls. A co-treatment with three Caspase inhibitors, zVAD.FMK (inhibitor of Caspases 1 and 3, 10 μM/l), Ac.YVAD.FMK (Caspase 1 inhibitor, 1 μM/l), Ac.DEVD.FMK (Caspase 3 inhibitor, 10 μM/l) as well as PTX (250 μM/l) significantly curtailed the AI% induced by TNFα The present studies thus identify the downstream effectors of TNFα-inducible apoptosis in MDS and so also the suppressors of TNFα apoptotic signaling. These results may have significant clinical implications in the therapy of MDS in the future.

Increased incidence of mitochondrial cytochrome c‐oxidase gene mutations in patients with myelodysplastic syndromes

Summary.  Mitochondria (mt) play an important role in both apoptosis and haem synthesis. The present study was conducted to determine DNA mutations in mitochondrial encoded cytochrome c‐oxidase I and II genes. Bone marrow (BM) biopsy and aspirate, peripheral blood (PB) and buccal smear samples were collected from 20 myelodysplastic syndrome (MDS) patients and 10 age‐matched controls. Cytochrome c‐oxidase I (CO I) and II (CO II) genes were amplified using polymerase chain reaction and sequenced. CO I mutations were found in 13/20 MDS patients and the CO II gene in 2/10 normal and 12/20 MDS samples, irrespective of MDS subtype. Mutations were substitutional, deletional and insertional. CO I mutations were most common at nucleotide positions 7264 (25%) and 7289 (15%), and CO II mutations were most common at nucleotide positions 7595 (40%) and 7594 (30%), suggesting the presence of potential ‘hot‐spots’. Mutations were not found in buccal smears of MDS patients and were significantly higher in MDS samples compared with age‐matched controls in all cell fractions (P < 0·05), with bone marrow high‐density fraction (BMHDF) showing a higher mutation rate than other fractions (P < 0·05). MDS marrows showed higher levels of apoptosis than normal controls (P < 0·05), and apoptosis in BMHDF was directly related to cytochrome c‐oxidase I gene mutations (P < 0·05). Electron microscopy revealed apoptosis affecting all haematopoietic lineages with highly abnormal, iron‐laden mitochondria. These results suggest a role for mt‐DNA mutations in the excessive apoptosis and resulting cytopenias of MDS patients.

An assessment of erythroid response to epoetin α as a single agent versus in combination with granulocyte– or granulocyte-macrophage–colony-stimulating factor in myelodysplastic syndromes using a meta-analysis approach†

Epoetin α (EPO) continues to be the initial treatment of choice for most anemic patients with myelodysplastic syndromes (MDS). Over the years, different therapeutic strategies have been adopted to optimize the clinical benefits of EPO in this setting.

Tumor necrosis factor-? induced DNA cleavage in human articular chondrocytes may involve multiple endonucleolytic activities during apoptosis

Apoptosis has been documented in chondrocytes both in the growth plates of young, healthy cartilages and in osteoarthritic cartilages; little, however, is known about apoptosis in chondrocytes of normal adult articular cartilage. For the current study, apoptosis in adult chondrocytes was evaluated by labeling DNA fragments using the ISEL in situ end labeling of 3′‐recessed strand breaks) or TUNEL (5′‐recessed or blunt‐ended strand breaks with terminal deoxynucleotidyl transferase‐mediated nick end labeling) techniques in primary cultures of chondrocytes in monolayer. Apoptosis was induced in the chondrocytes by either Tumor Necrosis Factor α (TNFα), Interleukin 1‐β (IL‐1β), or anti‐Fas antibody but only after 48 hours in culture. At 4 and 24 hours, there was no detectable DNA fragmentation. With TNFα, IL1β, and anti‐Fas antibody, chondrocytes show evidence of at least two types of DNA strand breaks within the same cell (as assessed by simultaneous labeling with ISEL and TUNEL). Therefore, some pathways leading to apoptosis in chondrocytes appear to involve more than one type of endonuclease activity. When the chondrocytes were cultured as explants with the articular matrix intact (ex vivo), neither IL‐1β, TNFα, the anti‐Fas antibody, nor fibronectin fragments were able to induce apoptosis in the chondrocytes. In normal human adult cartilage that was untreated and uncultured (in situ), DNA fragmentation was undetectable; however, a significant number of chondrocytes in osteoarthritic cartilage did contain strand breaks. These data suggest that apoptosis occurs in chondrocytes in which the matrix has been disrupted experimentally or destroyed by the osteoarthritic disease process. The results of these studies suggest that the ECM may be an essential survival factor for chondrocytes. Microsc. Res. Tech. 50:236–242, 2000.

bcl-2 and c-myc Expression, cell cycle kinetics and apoptosis during the progression of chronic myelogenous leukemia from diagnosis to blastic phase

Chronic myelogenous leukemia (CML) has a progressive course but little is known about the biologic characteristics of disease progression. This study was designed to assess the changes in cell proliferative characteristics, apoptosis, the expression of the bcl-2 and c-myc genes between the time of initial diagnosis and entrance into the blastic phase of the disease. We observed that the rate of cell proliferation decreased and the cell death rate did not significantly change as the disease accelerated. The level of bcl-2 expression was significantly higher in accelerated/blastic phase cells than in the chronic phase cells in the population as a whole, however, the bcl-2 expression level did not change in blast cell subpopulation. c-myc Expression was significantly higher in the blast cell subpopulation of accelerated/blastic phase than in that of earlier phases of the disease. In conclusion, the characteristics of CML cells, namely proliferation rate, c-myc and bcl-2 change during the course of the disease. It is possible that the change in c-myc expression plays a causative role in evolution of the blastic phase from the chronic phase.

Defining the dynamics of self-assembled Fas-receptor activation

Fas-Fas-ligand, the most well investigated apoptotic signaling system, plays a pivotal role in several human diseases. Its signaling through multiple pathways; multiple, complex regulatory points; and recently described tendency to undergo ligand-independent self-assembly warrant a comprehensive understanding of its physiologically well controlled function. In this review, we attempt to develop such a perspective on the regulation of Fas signaling. The multistep Fas regulation model presented here should be helpful in devising effective interventions for conditions resulting from the dysregulation of Fas.