Levels Of Spontaneous Apoptosis Research Articles

Spontaneous apoptosis and BCL2 gene expression as predictors of early death and short overall survival in acute leukemia patients: a prospective, case cohort study

BackgroundSpontaneous apoptosis and expression of MCL1, BCL2, and BCL-XL may be useful prognostic markers in acute leukemia patients. The purpose of this study is to examine the prognosis in adult leukemia patients based on spontaneous apoptosis and anti-apoptosis gene expressions in circulating leukocytes.ResultsEarly, late, and total apoptosis were significantly increased in peripheral blood leukocytes from patients diagnosed with acute myeloid leukemia (AML) and acute lymphoblastic leukemia (ALL) compared to controls and in cases of ALL versus AML (P < 0.001). Total apoptosis decreased significantly in AML and ALL patients who died early (ED); P = 0.001 and P = 0.002, respectively. Anti-apoptosis genes MCL1, BCL2, and BCL-XL were upregulated in 62.4%, 64.2%, and 62.4% of the acute leukemia patients, respectively. Among the AML patients, the up-regulation of BCL2 was paradoxically associated with increased apoptosis and low rates of ED. The expression levels of MCL1 and BCL-XL had no significant prognostic values; among patients diagnosed with non-acute promyelocytic leukemia (non-APL-AML), total spontaneous apoptosis, expression of BCL2, and performance status were independent predictors of overall survival (OS).ConclusionTotal spontaneous apoptosis and BCL2 gene expression may be valuable independent markers for OS in patients with non-APL-AML. Moreover, in ALL patients decreased levels of spontaneous apoptosis were associated with ED, although this was not a significant predictor of OS.

Comparison of the effects of co-transplantation of bone marrow hematopoietic stem cells and thymic multipotent stromal cells on the immune system of mice depending on methods

Physical interaction of multipotent stromal cells (MSCs) and hematopoietic stem cells (HSCs) is a modern approach to effective and focused changes in the properties of HSCs. Resulting of those contact interaction is significant activation of cells with following immune system restoration.&#x0D; The purpose of the study is to investigate the effect of co-transplantation of bone marrow hematopoietic stem cells (HSCs) and thymic multipotent stromal cells (MSCs) separately and as a union of cells on regeneration of the murine immune system, damaged by cyclophosphamide.&#x0D; MSCs were obtained from thymuses of C57BL mice using explant technique. Bone marrow cells (BMCs) were obtained by flushing out the femur with a nutrient medium. BMCs were cocultivated for 2 hours on the monolayer of thymus-derived MSCs. The immune deficiency of mice was modelled by the treatment with cyclophosphamide (CP). After that, the cells were co-transplanted in two methods (separately into different the retroorbital sinus and as a union after co-cultivation) and the parameters of the immune system were evaluated. It was shown, that separate co-transplantation of BMCs and thymus-derived MSCs is associated with the restoration of the number of bone marrow cells, thymus, spleen and lymph nodes with an increase in the proliferation index of lymph node cells by 1.4 times compared to control. It normalized the previous reduced concentration of hemoglobin and hematocrit in the blood. Co-transplantation had a suppressive effect on the blast transformation reaction, induced by phytohemagglutinin, by 4.3 times, but showed a stimulating effect on DTHR response by 1.6 times compared to control.&#x0D; Co-transplantation of the union of BMCs and MSCs is associated with the restoration of the number of bone marrow cells, spleen and lymph nodes. The level of spontaneous apoptosis of lymph node cells significantly increased by 3.3 times compared to control. It had not effect on hematological parameters, but is activated to impact the immune system. Thus, as a result of cells union administration showed normalization of the bactericidal activity of peritoneal macrophages, unlike the separate co-transplantation. This cells graft had a suppressive effect on the number of antibody-producing cells in the spleen by 4.2 times compared to control.&#x0D; Previous co-cultivation and contact interaction of cells change the properties of cell graft. The effect of co-transplantation of BMCs and thymic MSCs is not a simple additive effect of cells. It is acquiring the features typical to certain cell types, and the expression of new characteristics. We assume this phenomenon as a result development of complex cells cooperative processes in vivo and in vitro

MIF-Induced Stromal PKCβ/IL8 Is Essential in Human Acute Myeloid Leukemia

Acute myeloid leukemia (AML) cells exhibit a high level of spontaneous apoptosis when cultured in vitro but have a prolonged survival time in vivo, indicating that tissue microenvironment plays a critical role in promoting AML cell survival. In vitro studies have shown that bone marrow mesenchymal stromal cells (BM-MSC) protect AML blasts from spontaneous and chemotherapy-induced apoptosis. Here, we report a novel interaction between AML blasts and BM-MSCs, which benefits AML proliferation and survival. We initially examined the cytokine profile in cultured human AML compared with AML cultured with BM-MSCs and found that macrophage migration inhibitory factor (MIF) was highly expressed by primary AML, and that IL8 was increased in AML/BM-MSC cocultures. Recombinant MIF increased IL8 expression in BM-MSCs via its receptor CD74. Moreover, the MIF inhibitor ISO-1 inhibited AML-induced IL8 expression by BM-MSCs as well as BM-MSC-induced AML survival. Protein kinase C β (PKCβ) regulated MIF-induced IL8 in BM-MSCs. Finally, targeted IL8 shRNA inhibited BM-MSC-induced AML survival. These results describe a novel, bidirectional, prosurvival mechanism between AML blasts and BM-MSCs. Furthermore, they provide biologic rationale for therapeutic strategies in AML targeting the microenvironment, specifically MIF and IL8. Cancer Res; 77(2); 303-11. ©2016 AACR.

Protein Kinase C-ß Dependent IL-8 Release Promotes Acute Myeloid Leukemia Blast Cell Survival in Co-Cultures with Bone Marrow Stromal Cells

Introduction:Acute myeloid leukemia (AML) cells exhibit a high level of spontaneous apoptosis when cultured in vitro but have a prolonged survival time in vivo indicating that the tissue microenvironment plays a critical role in promoting AML cell survival. Knowledge of the complexity of the bone marrow microenvironment is increasing especially with respect to the bone marrow mesenchymal stromal cells [BM-MSC] which are considered a major protective cell type. Other studies have demonstrated the ability of BM-MSC to protect leukemia cells from spontaneous and chemotherapy-induced apoptosis. Increasing evidence suggests the existence of crosstalk between leukemia cells and BM stromal cells to create a leukemia-promoting environment. Recently our group and others have shown that this crosstalk is achieved by a complex communication system that involves multiple bidirectional signals which enhance AML survival and proliferation. Here we report a novel interaction between AML blasts and BM-MSC which benefits AML proliferation and survival.Methods:To investigate the interaction between primary AML blasts and BM-MSC we isolated AML and BM-MSC from the same patient and used an autologous in vitro culture assay to analyze the cytokine profile. Conditioned medium was collected from cultures of primary human AML alone or cultured with autologous BM-MSC and analyzed using Proteome Profiler Human XL Cytokine Array and target specific ELISAs. Real-time PCR was also used to verify the array data. MIF-Receptor inhibitors (SB 225002- CXCR2, AMD3100 - CXCR4 and CD74 blocking antibody - CD74) and signaling kinase inhibitors (LY294002- PI3K/AKT, PD098059 - MAPK, Ro-31-8220 - PKC) were used for initial determination of MIF signaling pathways in BM-MSC. Specific PKC isoform inhibitors (Go6976-PKCα/ß and enzastaurin -PKCß) were then used to determine isoform specific activation. Western blot and siRNA were used to confirm the role of AML derived MIF in regulating downstream BM-MSC signaling pathways including MAPK, PI3K/AKT, and PKC.Results:We initially examined the cytokine profile in cultured human AML compared to AML cultured with autologous BM-MSC or BM-MSC alone and found that MIF was highly expressed by primary AML and that IL-8 was increased in AML/BM-MSC co-cultures. The observed changes in IL-8 were confirmed by ELISA assays. RT-PCR was used to measure MIF and IL-8 gene expression from RNA extracted from primary AML or BM-MSC cultured alone or in combination. Results confirmed that MIF is highly expressed at the RNA and protein level by AML blasts and IL-8 transcription and cytokine release was upregulated in BM-MSC in response to co-culture with AML.Next we found that recombinant MIF increases IL-8 mRNA and protein expression in BM-MSC. Moreover, the MIF inhibition by, ISO-1, inhibits AML induced IL-8 expression and secretion by BM-MSC. Next we sought to determine which kinase signaling cascade is activated by MIF. We used a panel of protein kinase inhibitors and found that the pan-PKC inhibitor Ro-31-8220 completely inhibits AML and MIF induced IL-8 mRNA at sub micromolar concentrations. To further identify the specific PKC isoform responsible for linking AML induced MIF to IL-8 we used PKC isoform specific inhibitors (Go6976 and enzastaurin) which significantly inhibited MIF induced IL-8 expression and protein in BM-MSC. The introduction of PKCß siRNA dramatically inhibited MIF induced IL-8 mRNA expression in BM-MSC confirming that PKCß regulates AML induced BM-MSC derived IL-8 expression. Finally, inhibition of AML/BM-MSC co-cultures with the PKCß inhibitor enzastaurin inhibits BM-MSC induced AML survival in vitro.Conclusions:These results reported here show a novel bidirectional survival mechanism between AML blasts and BM-MSC. Furthermore this work identifies the PKC-ß-IL8 pathway in the BM-MSC of patients with AML as a novel target for future treatment strategies. DisclosuresNo relevant conflicts of interest to declare.

Loss of Nfkb1 leads to early onset aging.

NF-κB is a major regulator of age-dependent gene expression and the p50/NF-κB1 subunit is an integral modulator of NF-κB signaling. Here, we examined Nfkb1-/- mice to investigate the relationship between this subunit and aging. Although Nfkb1-/- mice appear similar to littermates at six months of age, by 12 months they have a higher incidence of several observable age-related phenotypes. In addition, aged Nfkb1-/- animals have increased kyphosis, decreased cortical bone, increased brain GFAP staining and a decrease in overall lifespan compared to Nfkb1+/+. In vitro, serially passaged primary Nfkb1-/- MEFs have more senescent cells than comparable Nfkb1+/+ MEFs. Also, Nfkb1-/- MEFs have greater amounts of phospho-H2AX foci and lower levels of spontaneous apoptosis than Nfkb1+/+, findings that are mirrored in the brains of Nfkb1-/- animals compared to Nfkb1+/+. Finally, in wildtype animals a substantial decrease in p50 DNA binding is seen in aged tissue compared to young. Together, these data show that loss of Nfkb1 leads to early animal aging that is associated with reduced apoptosis and increased cellular senescence. Moreover, loss of p50 DNA binding is a prominent feature of aged mice relative to young. These findings support the strong link between the NF-κB pathway and mammalian aging.

Tumour cells expressing single VEGF isoforms display distinct growth, survival and migration characteristics.

Vascular endothelial growth factor-A (VEGF) is produced by most cancer cells as multiple isoforms, which display distinct biological activities. VEGF plays an undisputed role in tumour growth, vascularisation and metastasis; nevertheless the functions of individual isoforms in these processes remain poorly understood. We investigated the effects of three main murine isoforms (VEGF188, 164 and 120) on tumour cell behaviour, using a panel of fibrosarcoma cells we developed that express them individually under endogenous promoter control. Fibrosarcomas expressing only VEGF188 (fs188) or wild type controls (fswt) were typically mesenchymal, formed ruffles and displayed strong matrix-binding activity. VEGF164- and VEGF120-producing cells (fs164 and fs120 respectively) were less typically mesenchymal, lacked ruffles but formed abundant cell-cell contacts. On 3D collagen, fs188 cells remained mesenchymal while fs164 and fs120 cells adopted rounded/amoeboid and a mix of rounded and elongated morphologies respectively. Consistent with their mesenchymal characteristics, fs188 cells migrated significantly faster than fs164 or fs120 cells on 2D surfaces while contractility inhibitors accelerated fs164 and fs120 cell migration. VEGF164/VEGF120 expression correlated with faster proliferation rates and lower levels of spontaneous apoptosis than VEGF188 expression. Nevertheless, VEGF188 was associated with constitutively active/phosphorylated AKT, ERK1/2 and Stat3 proteins. Differences in proliferation rates and apoptosis could be explained by defective signalling downstream of pAKT to FOXO and GSK3 in fs188 and fswt cells, which also correlated with p27/p21 cyclin-dependent kinase inhibitor over-expression. All cells expressed tyrosine kinase VEGF receptors, but these were not active/activatable suggesting that inherent differences between the cell lines are governed by endogenous VEGF isoform expression through complex interactions that are independent of tyrosine kinase receptor activation. VEGF isoforms are emerging as potential biomarkers for anti-VEGF therapies. Our results reveal novel roles of individual isoforms associated with cancer growth and metastasis and highlight the importance of understanding their diverse actions.

Spontaneousin vitroapoptosis ofde novochronic lymphocytic leukemia cells correlates with risk of the disease progression

Despite significant progress in treatment, chronic lymphocytic leukemia (CLL) still remains an incurable disease. Major advances have been recently made to understand the molecular pathogenesis underlying CLL, but defects in apoptosis are considered to be the most important factors. Although neoplastic cells are resistant to apoptosis in vivo, they show decreased level of spontaneous in vitro apoptosis, with significant differences among CLL patients. This work compares the level of spontaneous CLL cell apoptosis with prognostic factors and clinical course of the disease. In vitro spontaneous apoptosis of peripheral blood lymphocytes was analyzed using Annexin-V assay (confirmed by TUNEL method) in 135 treatment naïve patients with CLL. Levels of apoptosis after 48 h culture in patients with stable disease were found to be significantly higher than in the group with progressive course of the disease (P = 0.015). Moreover, the level of spontaneous apoptosis after 24 and 48 h of incubation correlated inversely with the progression free survival (P = 0.026 and 0.009, respectively). These results suggest that in vitro spontaneous apoptosis of CLL cells may be a simple and cheap prognostic test which is relatively quick to use, and can predict the course of the disease and response to treatment.

Spontaneous in vitro apoptosis of de novo chronic lymphocytic leukemia cells correlates with risk of the disease progression.

Despite significant progress in treatment, chronic lymphocytic leukemia (CLL) still remains an incurable disease. Major advances have been recently made to understand the molecular pathogenesis underlying CLL, but defects in apoptosis are considered to be the most important factors. Although neoplastic cells are resistant to apoptosis in vivo, they show decreased level of spontaneous in vitro apoptosis, with significant differences among CLL patients. This work compares the level of spontaneous CLL cell apoptosis with prognostic factors and clinical course of the disease. In vitro spontaneous apoptosis of peripheral blood lymphocytes was analyzed using Annexin-V assay (confirmed by TUNEL method) in 135 treatment naïve patients with CLL. Levels of apoptosis after 48h culture in patients with stable disease were found to be significantly higher than in the group with progressive course of the disease (p=0.015). Moreover, the level of spontaneous apoptosis after 24h and 48h of incubation correlated inversely with the progression free survival (p=0.026 and 0.009, respectively). These results suggest that in vitro spontaneous apoptosis of CLL cells may be a simple and cheap prognostic test which is relatively quick to use, and can predict the course of the disease and response to treatment. © 2014 Clinical Cytometry Society.

Gfi1 As a Novel Prognostic Marker and Tumor Suppressor In Acute Myeloid Leukemia

The differentiation of hematopoietic stem cells to mature cells is essential for the function of the hematopoietic system. Disturbance of this process can lead to the emergence of Acute Myeloid Leukemia (AML). AML is characterized by an accumulation of immature, malignant blasts, which disturb the function of the “normal” hematopoietic cells. The differentiation to myeloid cells is regulated among others by transcription factors. Growth factor independence 1 (GFI1) is such a hematopoietic transcription factor regulating the differentiation of myeloid cells.We sought to investigate whether different Gfi1 levels are causative for emergence of AML and how different levels of Gfi1 might influence the prognosis of patients. Using published expression array data, we observed that Gfi1 is expressed at a lower expression level in blast cells and in leukemic stem cells compared to the control non-malignant cells and stem cells.We then correlated Gfi1 expression level in blast cells of patients from different centers in with the event free survival. In Essen and Dresden (Germany), low expression levels in blast cells were (n=39) associated with an inferior prognosis (EFS 9 months for low expression compared to 42 months; p=0.0095).We confirmed our observation with an independent cohort from Rotterdam and Nijmegen. Patients with low Gfi1 expression (n=32) had an inferior event free survival (9 months) compared to patients with higher Gfi1 levels (n=144; 17 months; p=0.02). To further investigate how different levels of Gfi1 might influence initiation and progression of leukemia, we used mice expressing Gfi1 at different levels, i.e. Gfi1 deficient mice (Gfi1KO), mice heterozygous for Gfi1 (Gfi1 het) or mice expressing Gfi1 only at 20% of normal Gfi1 expression levels (Gfi1KD). We used different murine AML models to examine the role of Gfi1 in AML development. First we crossed these mice with Nup98HoxD13 mice that recapitulate MDS disease course. We observed that knockdown of Gfi1 (Gfi1KD n=15, P=0.05) and heterozygosity of Gfi1 (Gfi1 het) (n=12) accelerated AML development and were associated with higher blast cell number compared to Gfi1 wt mice (n=16). Interestingly, complete loss of Gfi1 (Gfi1KO, n=16) inhibited leukemia development.To confirm our findings, we used an independent approach. It has been shown previously that enforced retroviral expression of certain onco-fusion proteins such as MLL-AF9 or AML1-ETO9a or proteins such as MN1 can cause AML in mice. To this end we transduced lineage negative (Lin-) cells from the different mouse strains with retroviruses overexpressing these different proteins and plated the Lin-cells in methycellulose media. Similar to above, transduced Gfi1 KD cells generated more colonies and proliferated at higher levels than wt or Gfi1 KO cells (ranging between 1,5 to 4 fold KD compared to wt, depending on oncofusionprotein or oncogene, p=0.05). We also transplanted these cells into lethally irradiated mice. Again, mice transplanted with MLL-AF9 transduced Gfi1 KD cells (n=6) developed leukemia faster than mice transplanted with transduced wt (n=8; p= 0.05). We hypothesized that if lower expression of Gfi1 promotes leukemia formation, then overexpression of Gfi1 should inhibit leukemia formation.To this end we transduced Lin neg cells simultaneously with retroviruses overexpressing either MLL-AF9 or AMLETO9a and either Gfi1 or an empty vector. The cells were then plated in methycellulose and cells overexpressing Gfi1 generated fewer colonies (between 3-5 fold less, depending on oncogene, p=0.01) than cells transduced with an empty control vector.Thus, up to now our data suggests that decreased levels of Gfi1 influence prognosis of AML development and are involved in the pathogenesis of AML. On a molecular level, we found that knock-down and complete loss of Gfi1 leads to deregulation of genes in AML development such as HoxA9. However, whereas Gfi1KD cells show a normal response to apoptotic events, complete loss of Gfi1 is associated with a very high level of spontaneous apoptosis, possibly explaining why knock-down but not complete loss of Gfi1 accelerates AML development. In summary we demonstrate that Gfi1 plays a crucial role in AML development depending on the expression level, which in turn might explain the role of Gfi1 in human AML. Disclosures:No relevant conflicts of interest to declare.

Apoptosis and dysfunction of blood dendritic cells in patients with falciparum and vivax malaria

Malaria causes significant morbidity worldwide and a vaccine is urgently required. Plasmodium infection causes considerable immune dysregulation, and elicitation of vaccine immunity remains challenging. Given the central role of dendritic cells (DCs) in initiating immunity, understanding their biology during malaria will improve vaccination outcomes. Circulating DCs are particularly important, as they shape immune responses in vivo and reflect the functional status of other subpopulations. We performed cross-sectional and longitudinal assessments of the frequency, phenotype, and function of circulating DC in 67 Papuan adults during acute uncomplicated P. falciparum, P. vivax, and convalescent P. falciparum infections. We demonstrate that malaria patients display a significant reduction in circulating DC numbers and the concurrent accumulation of immature cells. Such alteration is associated with marked levels of spontaneous apoptosis and impairment in the ability of DC to mature, capture, and present antigens to T cells. Interestingly, sustained levels of plasma IL-10 were observed in patients with acute infection and were implicated in the induction of DC apoptosis. DC apoptosis was reversed upon IL-10 blockade, and DC function recovered when IL-10 levels returned to baseline by convalescence. Our data provide key information on the mechanisms behind DC suppression during malaria and will assist in developing strategies to better harness DC's immunotherapeutic potential.

Increased Susceptibility of Radiation-Induced Intestinal Apoptosis in SMP30 KO Mice

Recently, senescence marker protein-30 (SMP30) knockout (KO) mice have been reported to be susceptible to apoptosis, however, the role of SMP30 has not been characterized in the small intestine. The aim of the present study is to investigate the role of SMP30 in the process of spontaneous and γ-radiation-induced apoptosis in mouse small intestine. Eight-week-old male wild-type (WT) mice and SMP30 KO mice were examined after exposure to 0, 1, 3, 5, and 9 Gy of γ-radiation. Apoptosis in the crypts of the small intestine increased in the 0 to 5 Gy radiated SMP30 KO and WT mice. Radiation-induced apoptosis and the BAX/Bcl-2 ratio in the SMP30 KO mice were significantly increased in comparison to each identically treated group of WT mice (p < 0.05). The levels of spontaneous apoptosis in both WT and KO mice were similar (p > 0.05), indicating that increased apoptosis of crypt cells of SMP30 KO by irradiation can be associated with SMP30 depletion. These results suggested that SMP30 might be involved in overriding the apoptotic homeostatic mechanism in response to DNA damage.

Phenotypic heterogeneity and evidence of a founder effect associated with G6PC3 mutations in patients with severe congenital neutropenia

Phenotypic heterogeneity and evidence of a founder effect associated with <i>G6<scp>PC</scp>3</i> mutations in patients with severe congenital neutropenia

Hairy Cell Leukaemia Displaying Multiple Surface Immunoglobulin Isotypes Reveal a Functional B-Cell Receptor In Which Isotype Roles Differ

Abstract 1567The B-cell receptor (BCR) is critical to survival of normal B-cells, and regulates key aspects of cellular behavior. Of these, response to antigen determines pathways of normal B-cell maturation, including isotype switch events that occur by deletional class switch recombination (CSR), an irrevocable event, to yield IgG/A memory B-cells. Less frequently, CSR via a cryptic site generates IgD+ B-cells whereas IgM+IgD+ antigen experienced B-cells synthesize each isotype by an alternative transcript splicing mechanism. The role of the BCR in survival of malignant B-cells however is less well defined, in particular in response to antigen. Intriguingly, in Hairy cell leukemia (HCL), BCR assembly occurs with multiple surface immunoglobulin (sIg) isotypes (mult-HCL), many co-expressed on individual hairy cells (HCs) in an otherwise monoclonal tumor. Multiple isotypes appear to exclude deletional CSR events, and suggests a RNA processing mechanism of molecular assembly. This phenotype is rare even amongst malignant B-cells, and raises the question of the functional relevance of individual variant isotypes. It also potentially presents a model to dissect roles of multiple isotypes on single B-cells. To examine this, we investigated the BCR in CD19+CD11c+CD103+ mult-HCL cases (n=10), in which 2–4 differing sIg isotypes were present on most HCs, with single or, in 3 cases, dual sIgL expression. In all cases, IGHV genes were mutated, and confirmed monoclonality. Phenotype revealed 2 distinct subsets by sIg isotype co-expression, IgD+ve and IgD-ve. Using Ca2+ flux and ERK phosphorylation assays after cross-linking with specific anti-sIg antibodies, we observed a functional BCR in all mult-HCL examined, in both subsets (10/10 cases Ca2+, 6/6 cases ERK). However, striking differences emerged between the two subsets. In sIgD+ve mult-HCL, IgD mediated persistent Ca2+ flux, with flux also evident via >1 sIgH isotype. In marked contrast, in sIgD-ve mult-HCL Ca2+ flux was restricted to a single sIgH isotype, but not via IgM. Flux signals in this subset were transient. In most cases only a single sIgL transduced flux. We next evaluated BCR endocytosis after cross-linking individual isotypes and IgL. In 2 sIgD+ve cases, anti-IgD and anti-Igλ stimulation led to endocytosis of both sIgD and sIgλ, and in 1 case, where examined, anti-IgM stimulation endocytosed both sIgM and sIgλ. In 3 sIgD-ve cases, functional sIgH and sIgL induced endocytosis of the stimulated isotype, but again sIgM was dysfunctional, remaining immobilized on the cell surface. Ca2+ flux through endocytosed isotypes was correspondingly either significantly reduced or ablated in both subsets. In HCs, BCR endocytosis is clearly dependent on functional isotypes and IgL, and parallels events in normal B-cells. Lastly, we examined downstream effects of BCR signalling on cell viability, using soluble (sAb) and bound (bAb) anti-sIg antibodies. In a single IgD+ve mult-HCL case, both sAb and bAb anti-IgM yielded a significant level of apoptosis compared to control antibodies, whereas anti-IgD sAb resulted in no appreciable difference to level of spontaneous apoptosis, suggesting a disengagement of signals from this pathway. This disengagement was also observed in a separate HCL case expressing only IgD, and not in the mult-HCL cohort initially selected, where anti-IgD signals again did not increase levels of apoptosis. In IgD-ve mult-HCL (n=4), sAb and bAb specific cross-linking of IgG/A triggered significant apoptosis. These data demonstrate, for the first time, that mult-HCL retains a functional responsiveness via the BCR, suggesting an absence of anergic effects that may follow chronic antigen exposure in-vivo to self-antigen. Signals via sIgM/G/A isotypes, where functional, induce apoptosis in mult-HCL, whereas sIgD opposes such effects. Despite an apparently unique molecular mechanism of IgD expression in mult-HCL, this isotype appears to be hardwired in B-cells to mediate responses that differ from IgM. The persistent flux observed here indicates a more sustained and robust IgD signaling cascade, as also observed in B-cell models. These data reveal distinctive and opposing effects of individual isotypes on BCR mediated behavior in mult-HCL. While apoptotic responses appear to negate a role for antigen in tumor drive in-vivo, potential antigen engagement via IgD, if dominant leaves this question open. Disclosures:No relevant conflicts of interest to declare.

Biological Effects and Adaptive Response from Single and Repeated Computed Tomography Scans in Reticulocytes and Bone Marrow of C57BL/6 Mice

This study investigated the biological effects and adaptive responses induced by single and repeated in vivo computed tomography (CT) scans. We postulated that, through the induction of low-level oxidative stress, repeated low-dose CT scans (20 mGy, 2 days/week, 10 weeks) could protect mice (C57BL/6) from acute effects of high-dose radiation (1 Gy, 2 Gy). The micronucleated reticulocyte (MN-RET) count increased linearly after exposure to single CT scans of doses ranging from 20 to 80 mGy (P = 0.033). Ten weeks of repeated CT scans (total dose 400 mGy) produced a slight reduction in spontaneous MN-RET levels relative to levels in sham CT-scanned mice (P = 0.04). Decreases of nearly 10% in γ-H2AX fluorescence levels were observed in the repeated CT-scanned mice after an in vitro challenge dose of 1 Gy (P = 0.017) and 2 Gy (P = 0.026). Spontaneous apoptosis levels (caspase 3 and 7 activation) were also significantly lower in the repeated CT-scanned mice than the sham CT-scanned mice (P < 0.01). In contrast, mice receiving only a single CT scan showed a 19% elevation in apoptosis (P < 0.02) and a 10% increase in γ-H2AX fluorescence levels after a 2-Gy challenge (P < 0.05) relative to sham CT controls. Overall, repeated CT scans seemed to confer resistance to larger doses in mice, whereas mice exposed to single CT scans exhibited transient genotoxicity, enhanced apoptosis, and characteristics of radiation sensitization.

Antitumor Activity of YM155, a Selective Small-Molecule Survivin Suppressant, Alone and in Combination with Docetaxel in Human Malignant Melanoma Models

Aggressive cell growth and chemoresistance are notorious obstacles in melanoma therapy. Accumulating evidence suggests that survivin is preferentially expressed in cancer cells and plays a crucial role in cell division and apoptosis dysfunction. Here, we evaluated the therapeutic potential of YM155, a selective survivin suppressant, alone and in combination with docetaxel using human melanoma models. A375 and SK-MEL-5 human malignant melanoma cells were treated with siRNA, YM155, and/or docetaxel, and cell viability, mRNA and protein expression levels, cell-cycle distribution, and immunohistochemical staining were then evaluated. Furthermore, the efficacy of YM155 combined with docetaxel was further examined in established xenograft models. Survivin suppression was sufficient to induce spontaneous apoptosis of melanoma cells. YM155 showed nanomolar antiproliferative effects and induced tumor regression in established melanoma xenograft models. Docetaxel showed antitumor activity against melanoma cells, although it also induced survivin upregulation and G(2)/M mitotic arrest; however, cotreatment with YM155 decreased survivin expression below basal levels. Combination treatment of YM155 and docetaxel induced a greater rate of apoptosis than the sum of the single-treatment rates and promoted tumor regression without enhanced body weight loss in the melanoma xenograft models. Survivin is responsible for the inherent low levels of spontaneous apoptosis in melanoma cells. The concomitant combination of YM155 with docetaxel diminished the accumulation of survivin in G(2)/M mitotic arrest, and induced more intense apoptosis compared with each single treatment. YM155 in combination with docetaxel is well tolerated and shows greater efficacy than either agent alone in mouse xenograft models.

MicroRNA miR-125b induces senescence in human melanoma cells

MicroRNAs (miRNAs) are small noncoding RNA molecules involved in gene regulation. Aberrant expression of miRNA has been associated with the development or progression of several diseases, including cancer. In a previous study, we found that the expression of miRNA-125b (miR-125b) was two-fold lower in malignant melanoma producing lymph node micrometastases than in nonmetastasizing tumors. To get further insight into the functional role of miR-125b, we assessed whether its overexpression or silencing affects apoptosis, proliferation, or senescence in melanoma cell lines. We showed that overexpression of miR-125b induced typical senescent cell morphology, including increased cytoplasmatic/nucleus ratio and intensive cytoplasmatic β-galactosidase expression. In contrast, inhibition of miR-125b resulted in 30-35% decreased levels of spontaneous apoptosis. We propose that downregulation of miR-125b in an early cutaneous malignant melanoma can contribute to the increased metastatic capability of this tumor.

α‐TEA induces apoptosis of human breast cancer cells via activation of TRAIL/DR5 death receptor pathway

Vitamin E derivative RRR-α-tocopherol ether-linked acetic acid analog (α-TEA) induces apoptosis in MCF-7 and HCC-1954 human breast cancer cells in a dose- and time-dependent manner. α-TEA induces increased levels of tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) and death receptor-5 (DR5) and decreased levels of antiapoptotic factor, cellular FLICE-like inhibitory protein (c-FLIP L). DR5/TRAIL induced apoptosis involves downregulation of c-FLIP (L), caspase-8 activation, activated proapoptotic mediators tBid and Bax, mitochondrial permeability transition, and activation of caspase-9. siRNA knockdown of either DR5 or TRAIL blocks the ability of α-TEA to enhance DR5 protein levels, downregulate c-FLIP(L) protein levels and induce apoptosis. Combination of α-TEA + TRAIL acts cooperatively to induce apoptosis, and increase DR5 and decrease c-FLIP (L) protein levels. siRNA knockdown of c-FLIP produces a low level of spontaneous apoptosis and enhances α-TEA- and TRAIL-induced apoptosis. Taken together, these studies show that α-TEA induces TRAIL/DR5 mitochondria-dependent apoptosis in human breast cancer cells, and that TRAIL/DR5-dependent increases in DR5 and decreases in c-FLIP expression are triggered by TRAIL or α-TEA treatments.

Siglec-G Regulates B1 Cell Survival and Selection

Siglec-G is a negative regulator of BCR-mediated signaling in B1a cells. This population of B cells is highly increased in Siglec-G-deficient mice, but the mechanism of this expansion is not known so far. In this study, we demonstrate that Siglecg(-/-) B1a cells show a lower level of spontaneous apoptosis and a prolonged life span. Mechanistically, the lower apoptosis could result from higher expression levels of the transcription factor NFATc1 in Siglec-G-deficient B1a cells. Interestingly, Siglecg(-/-) B1a cells display an altered BCR repertoire compared with wild-type B1a cells. As the BCR repertoire and the VDJ composition of Igs of Siglecg(-/-) B1a cells resembles more the Abs produced by adult bone marrow-derived B cells rather than canonical fetal liver-derived B1a cells, this suggest that the selection into the B1a cell population is altered in Siglec-G-deficient mice.

Abstract 135: Apoptotic cell death triggering in the prostate carcinoma cell line PC3 by the anoikis effector Bit1

Abstract Highly aggressive cancer cells often are associated with resistance to caspase-dependent apoptosis, due, in part to loss in function or mutation in caspase effectors. Such apoptotic defects in caspase signaling pathway may provide a selective growth advantage for tumor cells and potentiate their aggressiveness and resistance to chemotherapeutic agents. Here, we test the responsiveness of the highly aggressive prostate cancer cell line PC3 cells to the apoptotic function of the novel, caspase-independent anoikis effector Bcl2 inhibitor of transcription (Bit1). Overexpression of the cytoplasmic localized Bit1 in PC3 cells results in significant induction of apoptosis as evidenced by the increased levels of histone-DNA fragments. Furthermore, PC3 cells transfected with the mitochondrial localized Bit1 exhibit significant apoptosis following loss of cell attachment as compared to vector treated cells, and such induction of anoikis is associated with increased levels of Bit1 in the cytosol. In contrast, both the control and Bit1 transfected PC3 cells show the same level of spontaneous apoptosis when grown attached to a culture dish. We also tested whether Bit1 alters the chemoresistant phenotype of PC3 cells. Consistent with the induction of anoikis sensitivity, overexpression of mitochondrial Bit1 also renders PC3 cells more sensitive to etoposide-induced apoptosis. Interestingly, the Bit1-mediated apoptosis in PC3 cells is correlated with increased NFkappa B activity as evidenced by increased nuclear translocation and transcription factor activity of the p65 subunit. Taken together, these findings indicate that activation of the caspase-independent Bit1 apoptotic pathway may serve as a preferred alternate approach in triggering apoptosis in aggressive prostate cancer cells. Bit1 may thus serve as a future therapeutic target for the treatment and alleviation of the chemoresistance characteristic of prostate cancer. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 135.

Abstract B26: Targeting glucose and glutamine metabolism in melanoma cells influences Noxa and Mcl-1 levels as well as susceptibility to TRAIL-induced apoptosis

Abstract Melanoma cells are notoriously resistant to conventional therapeutics (some of which trigger the intrinsic mitochondrial-based apoptotic pathway), whilst some melanoma cells are also resistant to extrinsic death ligand-mediated apoptosis. Emerging studies focused on metabolomics of cancer cells revealed that metabolic alterations in tumors could be exploited as novel targets for cancer therapy. Many tumor cells not only display a high rate of glucose uptake and glycolysis, but also exhibit increased glutamine consumption. In this study, apoptotic susceptibility to tumor necrosis factor (TNF)-related apoptosis-inducing ligand (TRAIL/APO2L) was investigated in four human melanoma cell lines in the presence of a metabolic inhibitor of glucose (2-deoxyglucose, 2DG, 10 mM) or glutamine (aminooxyacetate; AOA; 1mM, inhibitor of glutamate dependent transaminase). 2DG or AOA alone did not trigger significant apoptosis measured by Annexin V-PI staining and FACS analysis in these melanoma cell lines within a period of 24 hrs. However, the combined treatment with either 2DG plus TRAIL (100ng/ml), or AOA plus TRAIL, significantly induced apoptosis in 3 of 4 melanoma cell lines, compared to a single treatment protocol. Furthermore, the co-treatment selectively enhanced TRAIL mediated cytotoxicity only in melanoma cells, but not in normal human melanocytes or skin derived dermal fibroblasts. To more firmly establish the vital links between inhibition of glucose or glutamine metabolism and TRAIL efficacy, melanoma cells were also cultured with medium depleted of either glucose or glutamine for 1 day followed by adding TRAIL for another 24 hrs. Withdrawal of either glucose or glutamine by itself induced low level of spontaneous apoptosis in both melanoma cell lines tested. Similar to the treatment with 2DG or AOA, withdrawal of glucose or glutamine also sensitized both melanoma cell lines to TRAIL mediated apoptosis. The apoptosis induced by co-treatment with 2DG or AOA plus TRAIL was markedly blocked by a pan caspase inhibitor (Z-VAD), implicating a caspase-dependency. Western blotting analysis confirmed cotreatments effectively induced caspases 3 cleavage and Bid degradation in melanoma cells. Additionally 2DG or AOA plus TRAIL also resulted in loss of mitochondrial membrane potential (reduced Rhodamine123 uptake). Furthermore, both 2DG and AOA changed the balance between anti- and pro- apoptotic proteins of Bcl-2 family members. AOA was a stronger inducer compared to 2DG in enhancing BH3-only protein Noxa levels. 2DG was more effective in reducing Bcl-XL levels, while AOA more strongly inhibited Mcl-1 expression. Taken together, the findings of this study described a novel strategy to overcome the apoptotic resistance of melanoma cells by potentially activating both TRAIL-based, and mitochondrial-based, apoptosis by targeting either glucose or glutamine metabolic pathways for future melanoma therapeutic trials. Citation Information: Mol Cancer Ther 2009;8(12 Suppl):B26.