Bone marrow stromal cell-derived vascular endothelial growth factor (VEGF) rather than chronic lymphocytic leukemia (CLL) cell-derived VEGF is essential for the apoptotic resistance of cultured CLL cells

CD38/NAD+ glycohydrolase and associated antigens in chronic lymphocytic leukaemia: From interconnected signalling pathways to therapeutic strategies

Chronic lymphocytic leukaemia (CLL) is a heterogenous disease characterized by the accumulation of neoplastic CD5+/CD19+ B lymphocytes. The spreading of the leukaemia relies on the CLL cell's ability to survive in the blood and migrate to and proliferate within the bone marrow and lymphoid tissues. Some patients with CLL are either refractory to the currently available therapies or relapse after treatment; this emphasizes the need for novel therapeutic strategies that improving clinical responses and overcome drug resistance. CD38 is a marker of a poor prognosis and governs a set of survival, proliferation and migration signals that contribute to the pathophysiology of CLL. The literature data evidence a spatiotemporal association between the cell surface expression of CD38 and that of other CLL antigens, such as the B-cell receptor (BCR), CD19, CD26, CD44, the integrin very late antigen 4 (VLA4), the chemokine receptor CXCR4, the vascular endothelial growth factor receptor-2 (VEGF-R2), and the neutrophil gelatinase-associated lipocalin receptor (NGAL-R). Most of these proteins contribute to CLL cell survival, proliferation and trafficking, and cooperate with CD38 in multilayered signal transduction processes. In general, these antigens have already been validated as therapeutic targets in cancer, and a broad repertoire of specific monoclonal antibodies and derivatives are available. Here, we review the state of the art in this field and examine the therapeutic opportunities for cotargeting CD38 and its partners in CLL, e.g. by designing novel bi-/trispecific antibodies.

Mesenchymal stromal cell senescence in haematological malignancies

Acute myeloid leukaemia (AML), chronic lymphocytic leukaemia (CLL), and multiple myeloma (MM) are age-related haematological malignancies with defined precursor states termed myelodysplastic syndrome (MDS), monoclonal B-cell lymphocytosis (MBL), and monoclonal gammopathy of undetermined significance (MGUS), respectively. While the progression from asymptomatic precursor states to malignancy is widely considered to be mediated by the accumulation of genetic mutations in neoplastic haematopoietic cell clones, recent studies suggest that intrinsic genetic changes, alone, may be insufficient to drive the progression to overt malignancy. Notably, studies suggest that extrinsic, microenvironmental changes in the bone marrow (BM) may also promote the transition from these precursor states to active disease. There is now enhanced focus on extrinsic, age-related changes in the BM microenvironment that accompany the development of AML, CLL, and MM. One of the most prominent changes associated with ageing is the accumulation of senescent mesenchymal stromal cells within tissues and organs. In comparison with proliferating cells, senescent cells display an altered profile of secreted factors (secretome), termed the senescence-associated-secretory phenotype (SASP), comprising proteases, inflammatory cytokines, and growth factors that may render the local microenvironment favourable for cancer growth. It is well established that BM mesenchymal stromal cells (BM-MSCs) are key regulators of haematopoietic stem cell maintenance and fate determination. Moreover, there is emerging evidence that BM-MSC senescence may contribute to age-related haematopoietic decline and cancer development. This review explores the association between BM-MSC senescence and the development of haematological malignancies, and the functional role of senescent BM-MSCs in the development of these cancers.

Endothelial PERK-ATF4-JAG1 axis activated by T-ALL remodels bone marrow vascular niche

The endoplasmic reticulum unfolded protein response (UPR) is a conserved adaptive signaling in ER homeostasis and has emerged as critical in highly proliferating cells and potential treatment target for acute T-cell lymphoblastic leukemia (T-ALL). Methods: in this study, we assessed the transcriptomic and phenotypic alterations in UPR response of the bone marrow endothelial cells (ECs) in mice engrafted with T-ALL and in bone marrow specimens from patients who have T-ALL. We used PERK inhibitor and generated endothelial specific PERK knockout mice to study the impact of PERK on leukemia progression and hematopoiesis. We performed chromatin immunoprecipitation (ChIP) to study the mechanistic regulation of JAG1 by ATF4. We characterized small extracellular vesicles (SEV) from leukemia-developing mice and studied the effect of SEVs on EC function. Results: we found that T-ALL development induced a robust activation of protein kinase RNA-like endoplasmic reticulum kinase (PERK)-dominant UPR in the bone marrow endothelial vascular niche. The activation of PERK-eIF2a-ATF4 axis remodels the vascular niche, upregulates angiogenic factors including VEGFα and ATF4-regulated JAG1, and suppresses the expression of SCF and CXCL12, which are important to HSC maintenance and regeneration. Further, targeting endothelial PERK significantly improved T-ALL outcome. EC-specific deletion of PERK abolished the aberrant JAG1 up-regulation, improved HSC maintenance, promoted leukemia apoptosis, and improved overall survival. Finally, we showed that small extracellular vesicles are critical mediators of endothelial PERK-eIF2a-ATF4 activation and JAG1 up-regulation in leukemia. Corroborating animal model studies, activation of PERK-ATF4-JAG1 is prominent in human T-ALL bone marrow and T-ALL xenografts. Conclusion: our studies thus revealed for the first time that the leukemia-initiated PERK-ATF4-JAG1 axis plays a critical role in the remodeling of the bone marrow vascular niche and that targeting vascular niche UPR is a potential therapeutic opportunity in T-ALL.

The novel multiple sclerosis susceptibility gene ATXN1 regulates B cell receptor signaling in B-1a cells

Multiple sclerosis (MS) is an autoimmune demyelinating disease of the central nervous system (CNS) caused by complex gene-environment interactions. ATXN1 maps to 6p22.3, within the 233 loci associated with an increased risk of developing MS. Toxic gain-of-function mutations in ATXN1 cause the neurodegenerative disorder spinocerebellar ataxia type 1 (SCA1). Conversely, ATXN1 loss-of-function is involved in Alzheimer's disease (AD) and tumorigenesis. We have recently shown that ATXN1 exerts a protective immunomodulatory activity in the MS model experimental autoimmune encephalomyelitis (EAE). Specifically, we demonstrated that mice lacking Atxn1 experience aggravated EAE due to aberrant B cell functions. Atxn1-null mice exhibit increased B cell proliferation with the concomitant expansion of specific B cell subsets including B-1a cells. This population of B cells is responsible for the production of natural immunoglobulins and has been associated with the etiology of multiple autoimmune diseases. To understand the role played by Atxn1 in these cells, we performed comprehensive transcriptomic profiling of Atxn1-null B-1a cells before and after stimulation with an encephalitogenic antigen. Importantly, we show that in this sub-population Atxn1 regulates immunoglobulin gene transcription and signaling through the B cell receptor (BCR).

Antiapoptotic Proteins mcl-1 and bcl-2 as well as Growth Factors FGF and VEGF Influence Survival of Peripheral Blood and Bone Marrow Chronic Lymphocytic Leukemia Cells

Apoptosis inhibition in chronic lymphocytic leukemia (CLL) is one of the most important mechanism in the disease onset, progression and therapy response and is dependent of interaction with different microenvironments.

Aim of our paper is to determine expression of antiapoptoic proteins mcl-1 and bcl-2 in CLL cells isolated from two different compartments (peripheral blood and bone marrow) and its relation to percent of apoptotic cells and concentration of growth factors (FGF and VEGF).

Our results showed that peripheral blood CLL lymphocytes have lower apoptotic rate then those isolated from bone marrow, though bone marrow CLL lymphocytes express higher levels of antipoptotic proteins bcl-2 and mcl-1. In bone marrow FGF concentration is 10-fold higher then in patients plasma but has an limited impact on mcl-1 expression. In contrary, VEGF concentration is higher in peripheral blood and corelate with percent of apoptotic cells and mcl-1 expression in this compartment.

CLL cells derived from two different microenvironmets acts differently when tested for apoptosis „ex vivo“. In peripheral blood apoptosis is strongly connected with expression of antiapoptoic proteins (mcl-1 and bcl-2) and growth factors, but not in bone marrow.

Importance of Crosstalk Between Chronic Lymphocytic Leukemia Cells and the Stromal Microenvironment: Direct Contact, Soluble Factors, and Extracellular Vesicles

Chronic lymphocytic leukemia (CLL) is caused by the accumulation of malignant B cells due to a defect in apoptosis and the presence of small population of proliferating cells principally in the lymph nodes. The abnormal survival of CLL B cells is explained by a plethora of supportive stimuli produced by the surrounding cells of the microenvironment, including follicular dendritic cells (FDCs), and mesenchymal stromal cells (MSCs). This crosstalk between malignant cells and normal cells can take place directly by cell-to-cell contact (assisted by adhesion molecules such as VLA-4 or CD100), indirectly by soluble factors (chemokines such as CXCL12, CXCL13, or CCL2) interacting with their receptors or by the exchange of material (protein, microRNAs or long non-coding RNAs) via extracellular vesicles. These different communication methods lead to different activation pathways (including BCR and NFκB pathways), gene expression modifications (chemokines, antiapoptotic protein increase, prognostic biomarkers), chemotaxis, homing in lymphoid tissues and survival of leukemic cells. In addition, these interactions are bidirectional, and CLL cells can manipulate the normal surrounding stromal cells in different ways to establish a supportive microenvironment. Here, we review this complex crosstalk between CLL cells and stromal cells, focusing on the different types of interactions, activated pathways, treatment strategies to disrupt this bidirectional communication, and the prognostic impact of these induced modifications.

Bone Marrow Stromal Cells Drive Key Hallmarks of B Cell Malignancies

All B cell leukaemias and a substantial fraction of lymphomas display a natural niche residency in the bone marrow. While the bone marrow compartment may only be one of several sites of disease manifestations, the strong clinical significance of minimal residual disease (MRD) in the bone marrow strongly suggests that privileged niches exist in this anatomical site favouring central elements of malignant transformation. Here, the co-existence of two hierarchical systems, originating from haematopoietic and mesenchymal stem cells, has extensively been characterised with regard to regulation of the former (blood production) by the latter. How these two systems cooperate under pathological conditions is far less understood and is the focus of many current investigations. More recent single-cell sequencing techniques have now identified an unappreciated cellular heterogeneity of the bone marrow microenvironment. How each of these cell subtypes interact with each other and regulate normal and malignant haematopoiesis remains to be investigated. Here we review the evidences of how bone marrow stroma cells and malignant B cells reciprocally interact. Evidently from published data, these cell-cell interactions induce profound changes in signalling, gene expression and metabolic adaptations. While the past research has largely focussed on understanding changes imposed by stroma- on tumour cells, it is now clear that tumour-cell contact also has fundamental ramifications for the biology of stroma cells. Their careful characterisations are not only interesting from a scientific biological viewpoint but also relevant to clinical practice: Since tumour cells heavily depend on stroma cells for cell survival, proliferation and dissemination, interference with bone marrow stroma-tumour interactions bear therapeutic potential. The molecular characterisation of tumour-stroma interactions can identify new vulnerabilities, which could be therapeutically exploited.

The opportunistic effect of exosomes on Non-Hodgkin Lymphoma microenvironment modulation

There has been a shift in the paradigm of Non-Hodgkin lymphomas, changing from the classical genetic aberration-based model to a more complex and dynamic model involving tumor microenvironment interactions. In this instance, exosomes have emerged as important mediators in intercellular communication by providing survival and proliferation signals, licensing immune evasion and acquisition of drug resistance. The capability to transfer molecular cargo made exosomes a focus of research to understand cancer pathogenesis and its progression pathways. Several studies identified exosomes transporting tumor-released components in peripheral blood and focused on understanding their clinical relevance in the diagnosis, prognostic and in monitoring cancer progression. Moreover, due to their biophysical properties and physiological function, exosomes have drawn attention as potential therapeutic target and drug delivery vehicles. This review will discuss the function of exosomes in Non-Hodgkin lymphomagenesis, highlight their potential as diagnosis and prognosis biomarkers, and as new therapeutic opportunities in lymphoma management.

Ectopic expression of BIRC5-targeting miR-101-3p overcomes bone marrow stroma-mediated drug resistance in multiple myeloma cells

Background

Multiple myeloma (MM) cells gain protection against drugs through interaction with bone marrow stromal cells (BMSCs). This form of resistance largely accounts for resistance to therapy in MM patients which warrants further exploration to identify more potential therapeutic targets.

Methods

We performed miRNA/mRNA qPCR arrays and western blotting to analyze transcriptional and translational changes in MM cells co-cultured with BMSCs. Drug cytotoxicity and apoptosis in MM^GFP-BMSC co-cultures were measured using fluorescence plate reader and flowcytometry, respectively. miRNA was overexpressed in MM cell lines using Lentiviral transduction, miRNA-3’UTR binding was examined using luciferase assay.

Results

We found that BMSCs downregulated miR-101-3p and upregulated survivin (BIRC5) in MM cells. Survivin was downregulated by miR-101-3p overexpression and found to be a direct target of miR-101-3p using 3’UTR luciferase assay. Overexpression of survivin increased viability of MM cells in the presence of anti-myeloma drugs, and miR-101-3p inhibition by anti-miR against miR-101-3p upregulated survivin. Furthermore, overexpression of miR-101-3p or silencing of survivin triggered apoptosis in MM cells and sensitized them to anti-myeloma drugs in the presence of BMSCs overcoming the stroma-induced drug resistance.

Conclusions

Our study demonstrates that BMSC-induced resistance to drugs is associated with survivin upregulation which is a direct target of miR-101-3p. This study also identifies miR-101-3p-survivin interaction as a druggable target involved in stroma-mediated drug resistance in MM and suggests it for developing more efficient therapeutic strategies.

Overexpression of heme oxygenase-1 in microenvironment mediates vincristine resistance of B-cell acute lymphoblastic leukemia by promoting vascular endothelial growth factor secretion

Chemoresistance often causes treatment failure of B-cell acute lymphoblastic leukemia (B-ALL). However, the mechanism remains unclear at present. Herein, overexpression of heme oxygenase-1 (HO-1) was found in the bone marrow stromal cells (BMSCs) from B-ALL patients developing resistance to vincristine (VCR), a chemotherapeutic agent. Two B-ALL cell lines Super B15 and CCRF-SB were cocultured with BMSCs transfected with lentivirus to regulate the expression of HO-1. Silencing HO-1 expression in BMSCs increased the apoptotic rates of B-ALL cell lines induced by VCR, whereas upregulating HO-1 expression reduced the rate. Cell cycle can be arrested in the G2/M phase by VCR. In contrast, B-ALL cells were arrested in the G0/G1 phase due to HO-1 overexpression in BMSCs, which avoided damage from the G2/M phase. Vascular endothelial growth factor (VEGF) in BMSCs, as a key factor in the microenvironment-associated chemoresistance, was also positively coexpressed with HO-1. VEGF secretion was markedly increased in BMSCs with HO-1 upregulation but decreased in BMSCs with HO-1 silencing. B-ALL cell lines became resistant to VCR when cultured with VEGF recombinant protein, so VEGF secretion induced by HO-1 expression may promote the VCR resistance of B-ALL cells. As to the molecular mechanism, the PI3K/AKT pathway mediated regulation of VEGF by HO-1. In conclusion, this study clarifies a mechanism by which B-ALL is induced to resist VCR through HO-1 overexpression in BMSCs, and provides a novel strategy for overcoming VCR resistance in clinical practice.

Efficient lysis of B-chronic lymphocytic leukemia cells by the plant-derived sesquiterpene alcohol α-bisabolol, a dual proapoptotic and antiautophagic agent

The sesquiterpene α-bisabolol (α-BSB) is a cytotoxic agent against acute leukemia and chronic myeloid leukemia cells. Here the profile of α-BSB citotoxicity was evaluated ex vivo in primary mononuclear blood cells isolated from 45 untreated B-chronic lymphocytic leukemia (B-CLL) patients. We studied the effects of α-BSB by flow cytometric and western blotting techniques with the following findings: (1) α-BSB was an effective proapoptotic agent against B-CLL cells (IC50 42 ± 15 μM). It was also active, but to a lesser extent, on normal residual B cells and monocytes (IC50 68 ± 34 and 74 ± 28 μM, respectively; p < 0.01), while T-cells, though not achieving IC50, were nevertheless decreased. (2) Lipid raft content positively correlated with α-BSB cell sensitivity, while neither the phenotype of B-CLL cells nor the disease clinical stage did affect the sensitivity to α-BSB. (3) Flow cytometry analysis evidenced the induction of pores in mitochondrial and lysosomal membrane after 3- to 5-hour exposure of B-CLL cells to α-BSB, leading to apoptosis; in contrast, western blotting analysis showed inhibition of the autophagic flux. Therefore, according to cellular selectivity, α-BSB is a cytotoxic agent preferentially active against leukemic cells, while its lower activity on normal B cells, monocytes and T cells may account for an additive anti-inflammatory effect targeting the leukemia-associated pro-inflammatory microenvironment. Consistent with the observed effects on intracellular processes, α-BSB should be regarded as a dual agent, both activating mitochondrial-based apoptosis and inhibiting autophagy by disrupting lysosomes.

From genome to proteome: Looking beyond DNA and RNA in chronic lymphocytic leukemia

Chronic lymphocytic leukemia (CLL) remains the most common leukemia in the Western world. Whilst its disease course is extremely heterogeneous (ranging from indolent to aggressive), current methods are unable to accurately predict the clinical journey of each patient. There is clearly a pressing need for both improved prognostication and treatment options for patients with this disease. Whilst molecular studies have analyzed both genetic mutations and gene expression profiles of these malignant B-cells, and as a result have shed light on the pathogenesis of CLL, proteomic studies have been largely overlooked to date. This review summarizes our current knowledge of the proteomics of CLL, and discusses some of the issues in CLL proteomic research, such as reproducibility and data interpretation. In addition, we look ahead to how proteomics may significantly help in the development of a successful treatment for this currently incurable disease.

Green tea polyphenol "epigallocatechin-3-gallate", differentially induces apoptosis in CLL B-and T-Cells but not in healthy B-and T-Cells in a dose dependant manner

B-cell chronic lymphocytic leukaemia (CLL) is characterized by an accumulation of CD5-positive monoclonal B-cells due in large part to a failure of apoptosis. The ability to study CLL B-cells in vitro has always been a challenge and hampered by the low viability of the CLL B-cells in cell culture systems. In this study, we present a multicellular cell culture system to maintain CLL B-cells viable in culture for 60h in the presence of a stromal cell feeder layer in combination with a whole white blood cell preparation. Using this optimized system, we tested and showed that the addition of epigallocatechin-3-gallate (EGCG) at concentrations ranging from 25 to 100μg/ml induced apoptosis in CLL B-cells whilst not affecting healthy control B-cells. Moreover, the results showed that in contrast to healthy controls, T-cells from CLL patients underwent apoptosis in the presence of EGCG. This study demonstrated that the combination of a cell feeder layer with a whole white blood cell preparation maintained B-cell viability in vitro over an extended period of time. In addition, the study showed that EGCG differentially induces apoptosis in CLL B-and T-Cells but not in healthy B-and T-Cells in a dose dependent manner.

Angiogenesis in Liquid Tumors: An In Vitro Assay for Leukemic-Cell-Induced Bone Marrow Angiogenesis

The critical role of angiogenesis for solid tumor growth and metastatic spread has been well established. In contrast, even though increased vascularity has been commonly observed in bone marrows of patients with hematological malignancies (liquid tumors), the pathophysiology of leukemia-induced angiogenesis in the bone marrow remains elusive. This paper demonstrates the usage of a microengineered 3D biomimetic model to study leukemic-cell-induced bone marrow angiogenesis. Rational design of the 3D angiogenesis chip incorporating endothelial cells (ECs), leukemic cells, and bone marrow stromal fibroblasts provide an efficient biomimetic means to promote and visualize early angiogenic processes. Morphological features of angiogenesis induced by three different leukemic cell lines (U937, HL60, and K562) are investigated and compared. Quantitative measurements of angiogenic factors secreted from monocultures and cocultures of leukemic cells with bone marrow stromal fibroblasts suggest a synergistic relationship between ECs, leukemic cells, and bone marrow stromal fibroblasts for angiogenic induction, and also confirm the necessity of conducting functional angiogenic assays in proper 3D biomimetic cell culture systems like the one developed in this work.

The MEK1/2 inhibitor, MEKi-1, induces cell death in chronic lymphocytic leukemia cells under conditions that mimic the tumor microenvironment and is synergistic with fludarabine

The Raf-1/MEK/ERK1/2 pathway has become a focus for novel cancer therapies. This study sought to investigate whether targeting MEK1/2 may represent a therapeutic option for chronic lymphocytic leukemia (CLL). The MEK1/2 inhibitor, MEKi-1, induced apoptosis of CLL cells and was synergistic with fludarabine under conditions that mimic the tumor microenvironment, irrespective of poor-risk characteristics. MEKi-1 down-regulated the activities of AKT and ERK1/2 and was synergistic with fludarabine through a mechanism that involved potentiation of DNA damage and attenuation of the activity of ERK1/2 and expression of Mcl-1. This study highlights the significant role of the mitogen-activated protein kinase (MAPK)-ERK1/2 pathway in mediating the effects of the CLL tumor microenvironment and suggests that targeting MEK1/2 in CLL cells may impact upon the activity of both ERK1/2 and AKT. Inhibitors of MEK1/2 as single agents or in combination with DNA-damaging agents may represent a novel therapeutic strategy for CLL.

Targeting chronic lymphocytic leukemia cells in the tumor microenviroment: A review of the in vitro and clinical trials to date

Chronic lymphocytic leukemia (CLL) is the most common leukemia in the western world. Despite significant advances in therapy over the last decade CLL remains incurable. Current front-line therapy often consists of chemoimmunotherapy-based regimens, most commonly the fludarabine, cyclophosphamide plus rituximab combination, but rates of relapse and refractory disease are high among these patients. Several key signaling pathways are now known to mediate the survival and proliferation of CLL cells in vivo, the most notable of which are the pathways mediated by the B-cell receptor (BCR) and cytokine receptors. A better understanding of the pathogenesis of the disease, the underlying biology of the CLL-cell and the roles of the tumour microenvironment has provided the rationale for trials of a range of novel, more targeted therapeutic agents. In particular, clinical trials of ibrutinib and idelalisib, which target the Brutons tyrosine kinase and the delta isoform of phosphoinositol-3 kinase components of the BCR signaling pathway respectively, have shown extremely promising results. Here we review the current literature on the key signaling pathways and interactions of CLL cells that mediate the survival and proliferation of the leukemic cells. For each we describe the results of the recent clinical trials and in vitro studies of novel therapeutic agents.

The Therapeutic Effects of Human Mesenchymal Stem Cells Primed with Sphingosine-1 Phosphate on Pulmonary Artery Hypertension

Stem cell (SC) therapy has become a potential treatment modality for pulmonary artery hypertension (PAH), but the efficacy of human SC and priming effects have not yet been established. The mobilization and homing of hematopoietic stem cells (HSCs) are modulated by priming factors that include a bioactive lipid, sphingosine-1-phosphate (S1P), which stimulates CXCR4 receptor kinase signaling. Here, we show that priming human mesenchymal stem cells (MSCs) with S1P enhances their therapeutic efficacy in PAH. Human MSCs, similar to HSCs, showed stronger chemoattraction to S1P in transwell assays. Concomitantly, MSCs treated with 0.2 μM S1P showed increased phosphorylation of both MAPKp42/44 and AKT protein compared with nonprimed MSCs. Furthermore, S1P-primed MSCs potentiated colony forming unit-fibroblast, anti-inflammatory, and angiogenic activities of MSCs in culture. In a PAH animal model induced by subcutaneously injected monocrotaline, administration of human cord blood-derived MSCs (hCB-MSCs) or S1P-primed cells significantly attenuated the elevated right ventricular systolic pressure. Notably, S1P-primed CB-MSCs, but not unprimed hCB-MSCs, also elicited a significant reduction in the right ventricular weight ratio and pulmonary vascular wall thickness. S1P-primed MSCs enhanced the expression of several genes responsible for stem cell trafficking and angiogenesis, increasing the density of blood vessels in the damaged lungs. Thus, this study demonstrates that human MSCs have potential utility for the treatment of PAH, and that S1P priming increases the effects of SC therapy by enhancing cardiac and vascular remodeling. By optimizing this protocol in future studies, SC therapy might form a basis for clinical trials to treat human PAH.

DNA damage response and evasion from immunosurveillance in CLL: new options for NK cell-based immunotherapies

Chronic lymphocytic leukemia (CLL) is the most prominent B cell malignancy among adults in the Western world and characterized by a clonal expansion of B cells. The patients suffer from severe immune defects resulting in increased susceptibility to infections and failure to generate an antitumor immune response. Defects in both, DNA damage response (DDR) pathway and crosstalk with the tissue microenvironment have been reported to play a crucial role for the survival of CLL cells, therapy resistance and impaired immune response. To this end, major advances over the past years have highlighted several T cell immune evasion mechanisms in CLL. Here, we discuss the consequences of an impaired DDR pathway for detection and elimination of CLL cells by natural killer (NK) cells. NK cells are considered to be a major component of the immunosurveillance in leukemia but NK cell activity is impaired in CLL. Restoration of NK cell activity using immunoligands and immunoconstructs in combination with the conventional chemotherapy may provide a future perspective for CLL treatment.

Vascular endothelial growth factor A (VEGFA) gene polymorphisms have an impact on survival in a subgroup of indolent patients with chronic lymphocytic leukemia

Vascular endothelial growth factor (VEGF)-mediated angiogenesis contributes to the pathogenesis of B-cell chronic lymphocytic leukaemia (CLL). We investigated the impact of VEGFA gene diversity on the clinical outcome of patients with this disease. A VEGFA haplotype conformed by positions rs699947 (–1540C>A), rs833061 (–460T>C) and rs2010963 (405C>G) and two additional single-nucleotide polymorphisms (SNPs), rs3025039 (936C>T) and rs25648 (1032C>T), were analysed in 239 patients at the time of their CLL diagnosis. Here, we showed that homozygosity for rs699947/rs833061/rs2010963 ACG haplotype (ACG^+/+ genotype) correlated with a reduced survival in CLL patients (ACG^+/+ vs other genotypes: HR = 2.3, p = 0.002; recessive model). In multivariate analysis, the ACG^+/+ genotype was identified as a novel independent prognostic factor (HR = 2.1, p = 0.005). Moreover, ACG homozygosity subdivided patients with CLL with otherwise indolent parameters into prognostic subgroups with different outcomes. Specifically, patients carrying the ACG^+/+ genotype with mutated IgV_H, very low and low-risk cytogenetics, initial clinical stage, CD38 negative status or early age at diagnosis showed a shorter survival (ACG^+/+ vs other genotypes: HR = 3.5, p = 0.035; HR = 3.4, p = 0.001; HR = 2.2, p = 0.035; HR = 3.4, p = 0.0001 and HR = 3.1, p = 0.009, respectively). In conclusion, VEGFA ACG^+/+ genotype confers an adverse effect in overall survival in CLL patients with an indolent course of the disease. These observations support the biological and prognostic implications of VEGFA genetics in CLL.

Biology of chronic lymphocytic leukemia in different microenvironments: clinical and therapeutic implications

Chronic lymphocytic leukemia (CLL) is characterized by the accumulation of mature monoclonal B cells in peripheral blood, bone marrow, spleen, and lymph nodes. The trafficking, survival, and proliferation of CLL cells is tightly regulated by the surrounding tissue microenvironment and is mediated by antigenic stimulation, close interaction with various accessory cells and exposure to different cytokines, chemokines, and extracellular matrix components. In the last decade there have been major advances in the understanding of the reciprocal interactions between CLL cells and the various microenvironmental compartments. This article discusses the role of the microenvironment in the context of efforts to develop novel therapeutics that target the biology of CLL.

IL-21 and CD40L signals from autologous T cells can induce antigen-independent proliferation of CLL cells

Chronic lymphocytic leukemia (CLL) cells multiply in secondary lymphoid tissue, but the mechanisms leading to their proliferation are still uncertain. In addition to B-cell receptor (BCR)-triggered signals, other microenvironmental factors might well be involved. In proliferation centers, leukemic B cells are in close contact with CD4(+)CD40L(+) T cells. Therefore, we here dissected the signals provided by autologous activated T cells (Tact) to CLL cells. Although the gene expression profile induced by Tact was highly similar to that induced by sole CD40 signaling, an obvious difference was that Tact induced proliferation of CLL cells. We determined that stimulation with only CD40L+IL-21 was sufficient to induce robust proliferation in CLL cells. We then defined an interleukin (IL)-21-induced gene signature in CLL, containing components of Janus kinase/signal transducer and activator of transcription and apoptosis pathways, and this signature could be detected in lymph node (LN) samples from patients. Finally, we could detect IL-21 RNA and protein in LN, and IL-21 production ex vivo by LN CD4(+)CXCR5(+) follicular helper T cells. These results indicate that in addition to BCR signaling, activated T cells might contribute to CLL cell proliferation via CD40 and IL-21. Targeting these signaling pathways might offer new venues for treatment of CLL.

VEGF and bFGF gene polymorphisms in Polish patients with B-CLL

Among a variety of angiogenic factors involved in the B cell chronic lymphocytic leukemia (B-CLL), vascular endothelial growth factor (VEGF) and basic fibroblast growth factor (bFGF) were identified. Their levels have been regarded as prognostic markers of the progression of disease. The objective of the present study was to assess whether polymorphisms located within the genes coding for these key angiogenic activators contribute to disease susceptibility and/or progression in patients with B-CLL. For this purpose, 180 individuals were investigated, including 68 B-CLL patients and 112 healthy controls. All individuals were typed for the VEGF (936 C > T) and bFGF (−921 C > G) alleles using PCR–RFLP technique. Only a slight prevalence of the VEGF T variant was observed among patients as compared to healthy individuals (p = 0.095) with a significant difference when high risk (stage III/IV) patients were considered (OR = 3.81, p = 0.045). No other significant association was observed between the VEGF polymorphism and progression of the disease. The VEGF alleles and genotypes segregated similarly in patients with different stage of the disease according to Rai classification. No significant relationships were also observed for the bFGF polymorphism with either susceptibility to B-CLL (when compared to control group) or progression of the disease. These results suggest the possible association of the VEGF polymorphism with high risk B-CLL.

Effect of bone marrow mesenchymal stem cells on experimental pulmonary arterial hypertension

The aim of the present study was to investigate the effect of bone marrow mesenchymal stem cell (BMSC) transp1antation on lung and heart damage in a rat model of monocrotaline (MCT)-induced pulmonary arterial hypertension (PAH). The animals were randomly divided into 3 groups: control, PAH and BMSC implantation groups. Structural changes in the pulmonary vascular wall, such as the pulmonary artery lumen area (VA) and vascular area (TAA) were measured by hematoxylin and eosin (H&E) staining, and the hemodynamics were detected by echocardiography. Two weeks post-operation, our results demonstrated that sublingual vein injection of BMSCs significantly attenuated the pulmonary vascular structural and hemodynamic changes caused by pulmonary arterial hypertension. The mechanism may be executed via paracrine effects.

Angiogenic factors in chronic lymphocytic leukemia

Angiogenesis is a complex process controlled by the balance of a large number of regulating factors, the pro- and anti-angiogenic factors. Dysregulation of angiogenesis occurs in various pathologies and is one of the hallmarks for cancer. Recent emphasis on the microenvironment's influence in chronic lymphocytic leukemia (CLL) progression and drug resistance nurtures the interest in angiogenesis. Researchers have already identified a variety of angiogenic factors involved in the CLL, including vascular endothelial growth factor (VEGF), basic fibroblast growth factor (bFGF), platelet-derived growth factor (PDGF), angiopoietin-2(Ang-2), thrombospondin-1 (TSP-1), as well as extracellular proteinases such as matrix metalloproteinase-9 (MMP-9). Besides modulating neovascularization, angiogenic factors also participate in the regulation of pro-survival effects of CLL cells. However, the precise mechanism involved still needs to be elucidated further. At present, the levels of some angiogenic factors are regarded as prognostic markers of the progression of CLL, although it is not widely used. Several anti-VEGF agents are currently under clinical trial. Advances in the understanding of the bases of angiogenesis regulators will be benefit for the comprehension of CLL pathogenesis and help to conquer the disease.

Vascular endothelial growth factor levels in childhood acute lymphoblastic and myeloblastic leukemia

Angiogenesis has been associated with the growth, dissemination and metastasis and has been shown to be a prognostic. Although there are some data suggesting that angiogenesis may have a role in the pathophysiology of leukemia, its role in patient prognosis is yet to be defined. We analyzed the expression level of vascular endothelial growth factor (VEGF), an angiogenesis promoter and its possible- prognostic value in bone marrow samples at the time of diagnosis and remission of acute childhood leukemia patients. Besides 46 patients diagnosed as ALL or AML, 16 children were also included as a control group in the study. Our data have demonstrated that VEGF levels of AML patients were found higher than the control group statistically (P = 0.022). However we could not find any significant difference between VEGF levels of diagnosis and remission in both AML and ALL groups by blastic VEGF expression (P > 0.05). In this study the higher levels of VEGF in AML patients is one of the main findings although we were not able to assess any role of VEGF in predicting prognosis in pediatric leukemia patients by evaluating blastic cell VEGF expression. These results have demonstrated that the relationship between angiogenesis or angiogenesis promoters and hematological malignancies is not clear and simple as different methods or different cells beside different angiogenesis promotors are involved to these studies. So that not only tumor cells and their cytokines but also surrounding cells and their cytokines must be taken into consideration with the standardized study methods in the further studies to obtain a promising treatment approach.