Increased angiogenesis induced by chronic lymphocytic leukemia B cells is mediated by leukemia-derived Ang2 and VEGF

Inflammation mediated angiogenesis in chronic lymphocytic leukemia

Chronic inflammation has been identified in leukemias as an essential regulator of angiogenesis. B-chronic lymphocytic leukemia (CLL) cells secrete high levels of vascular endothelial growth factor (VEGF) and hypoxia inducible factor 1 alpha (HIF1α). The aim was to assess the role of inflammation in activation of angiogenic factors: endothelial nitric oxide synthase (eNOS), HIF1α and VEGF via proliferation related signaling pathways and VEGF autocrine control. We isolated mononuclear cells (MNC) and CD19+ cells from peripheral blood of 60 patients with CLL. MNC were treated with pro-inflammatory interleukin-6 (IL-6) and VEGF, in combination with inhibitors of JAK1/2 (Ruxolitinib), mTOR (Rapamycin), NF-κB (JSH23), SMAD (LDN-193189) and PI3K/AKT (Ly294002) signaling pathways, to evaluate eNOS, VEGF and HIF1α expression by immunoblotting, immunocytochemistry and RT-qPCR. Also, we investigated IL-6 dependent neovascularization in human microvascular endothelial cells (HMEC-1) in co-culture with MNC of CLL. The angiogenic factors eNOS, VEGF and HIF1α had significantly higher frequencies in MNC of CLL in comparison to healthy controls (p < 0.001) and CD19+ cells of CLL. IL-6 increased the quantity of HIF1α (p < 0.05) and VEGF positive cells in the presence of JSH23 (p < 0.01). VEGF increased HIF1α (p < 0.05), and decreased eNOS gene expression (p < 0.01) in MNC of CLL. VEGF significantly (p < 0.001) increased the number of HIF1α positive MNC of CLL, prevented by inhibitors of JAK1/2, PI3K and mTOR signaling pathways. VEGF stimulation of SMAD (p < 0.05) and STAT5 (p < 0.01) signaling has been prevented by inhibitors of JAK1/2, mTOR, PI3K and SMAD signaling, individually (p < 0.01) or mutually (p < 0.001). Also, we showed that MNC of CLL and IL-6 individually stimulate neovascularization in co-culture with HMEC-1, without a cumulative effect. We demonstrated elevated angiogenic factors in CLL, while VEGF and IL-6 independently stimulated HIF1α. VEGF stimulation of HIF1α was mostly mTOR dependent, while IL-6 stimulation was NF-κB dependent.

The Role of the Microenvironment and Cell Adhesion Molecules in Chronic Lymphocytic Leukemia

Chronic lymphocytic leukemia (CLL) is a B-cell malignancy whose progression largely depends on the lymph node and bone marrow microenvironment. Indeed, CLL cells actively proliferate in specific regions of these anatomical compartments, known as proliferation centers, while being quiescent in the blood stream. Hence, CLL cell adhesion and migration into these protective niches are critical for CLL pathophysiology. CLL cells are lodged in their microenvironment through a series of molecular interactions that are mediated by cellular adhesion molecules and their counter receptors. The importance of these adhesion molecules in the clinic is demonstrated by the correlation between the expression levels of some of them, in particular CD49d, and the prognostic likelihood. Furthermore, novel therapeutic agents, such as ibrutinib, impair the functions of these adhesion molecules, leading to an egress of CLL cells from the lymph nodes and bone marrow into the circulation together with an inhibition of homing into these survival niches, thereby preventing disease progression. Several adhesion molecules have been shown to participate in CLL adhesion and migration. Their importance also stems from the observation that they are involved in promoting, directly or indirectly, survival signals that sustain CLL proliferation and limit the efficacy of standard and novel chemotherapeutic drugs, a process known as cell adhesion-mediated drug resistance. In this respect, many studies have elucidated the molecular mechanisms underlying cell adhesion-mediated drug resistance, which have highlighted different signaling pathways that may represent potential therapeutic targets. Here, we review the role of the microenvironment and the adhesion molecules that have been shown to be important in CLL and their impact on transendothelial migration and cell-mediated drug resistance. We also discuss how novel therapeutic compounds modulate the function of this important class of molecules.

A comprehensive insight into the role of molecular pathways affected by the Angiopoietin and Tie system involved in hematological malignancies' pathogenesis

Angiogenesis has been recognized as a critical factor in developing solid tumors and hematological malignancies. How angiogenesis affects the molecular pathways in malignancies is still a mystery. The angiopoietin family, one of the known molecular mediators for angiogenesis, encourages angiogenesis by attaching to Tie receptors on cell surfaces. Angiopoietin, Tie, and particularly the molecular pathways they mediate have all been the subject of recent studies that have established their diagnostic, prognostic, and therapeutic potential. Here, we've reviewed the function of molecular pathways impacted by the Angiogenin and Tie system in hematological malignancies.

An overview of the molecular and clinical significance of the angiopoietin system in leukemia

The angiogenesis efficacy in solid tumors and hematological malignancies has been identified for more than twenty years. Although the exact role of angiogenesis in leukemia as a common hematological malignancy has not yet been extensively studied, its effect is demonstrated on the initiation and maintenance of a favorable microenvironment for leukemia cell proliferation. The angiopoietin family is a defined molecular mediator for angiogenesis, which contributes to vascular permeability and angiogenesis initiation. They participate in the angiogenesis process by binding to tyrosine kinase receptors (Tie) on endothelial cells. Considering the role of angiogenesis in leukemia development and the crucial effects of the Ang-Tie system in angiogenesis regulation, many studies have focused on the correlation between the Ang-Tie system and leukemia diagnosis, monitoring, and treatment. In this study, we reviewed the Ang-Tie system's potential diagnostic and therapeutic effects in different types of leukemia in the gene expression level analysis approach. The angiopoietin family context-dependent manner prevents us from defining its actual function in leukemia, emphasizing the need for more comprehensive studies.

Soluble markers of B cell activation suggest a role of B cells in the pathogenesis of systemic sclerosis-associated pulmonary arterial hypertension

Introduction

Soluble markers of B cell activation are interesting diagnostic and prognostic tools in autoimmune diseases. Data in systemic sclerosis (SSc) are scarce and few studies focused on their association with disease characteristics.

Methods

1. Serum levels of 14 B cell biomarkers (β2-microglobulin, rheumatoid factor (RF), immunoglobulins (Ig) G, IgA, IgM, BAFF, APRIL, soluble (s)TACI, sBCMA sCD21, sCD23, sCD25, sCD27, CXCL13) were measured in SSc patients and healthy controls (HC). 2. Associations between these biomarkers and SSc characteristics were assessed. 3. The pathophysiological relevance of identified associations was explored by studying protein production in B cell culture supernatant.

Results

In a discovery panel of 80 SSc patients encompassing the broad spectrum of disease manifestations, we observed a higher frequency of RF positivity, and increased levels of β2-microglobulin, IgG and CXCL13 compared with HC. We found significant associations between several biomarkers and SSc characteristics related to disease phenotype, activity and severity. Especially, serum IgG levels were associated with pulmonary hypertension (PH); β2-microglobulin with Nt-pro-BNP and DLCO; and BAFF with peak tricuspid regurgitation velocity (TRV). In a validation cohort of limited cutaneous SSc patients without extensive ILD, we observed lower serum IgG levels, and higher β2-microglobulin, sBCMA, sCD23 and sCD27 levels in patients with pulmonary arterial hypertension (PAH). BAFF levels strongly correlated with Nt-pro-BNP levels, FVC/DLCO ratio and peak TRV in SSc-PAH patients. Cultured SSc B cells showed increased production of various angiogenic factors (angiogenin, angiopoietin-1, VEGFR-1, PDGF-AA, MMP-8, TIMP-1, L-selectin) and decreased production of angiopoietin-2 compared to HC.

Conclusion

Soluble markers of B cell activation could be relevant tools to assess organ involvements, activity and severity in SSc. Their associations with PAH could plead for a role of B cell activation in the pathogenesis of pulmonary microangiopathy. B cells may contribute to SSc vasculopathy through production of angiogenic mediators.

Immunomodulatory Drugs for the Treatment of B Cell Malignancies

Accumulating evidence suggests that the tumor microenvironment (TME) is involved in disease progression and drug resistance in B cell malignancies, by supporting tumor growth and facilitating the ability of malignant cells to avoid immune recognition. Immunomodulatory drugs (IMiDs) such as lenalidomide have some direct anti-tumor activity, but critically also target various cellular compartments of the TME including T cells, NK cells, and stromal cells, which interfere with pro-tumor signaling while activating anti-tumor immune responses. Lenalidomide has delivered favorable clinical outcomes as a single-agent, and in combination therapy leads to durable responses in chronic lymphocytic leukemia (CLL) and several non-Hodgkin lymphomas (NHLs) including follicular lymphoma (FL), diffuse large B cell lymphoma (DLBCL), and mantle cell lymphoma (MCL). Recently, avadomide, a next generation cereblon E3 ligase modulator (CELMoD), has shown potent anti-tumor and TME immunomodulatory effects, as well as promising clinical efficacy in DLBCL. This review describes how the pleiotropic effects of IMiDs and CELMoDs could make them excellent candidates for combination therapy in the immuno-oncology era-a concept supported by preclinical data, as well as the recent approval of lenalidomide in combination with rituximab for the treatment of relapsed/refractory (R/R) FL.

Prognostic Value of Tie2-Expressing Monocytes in Chronic Lymphocytic Leukemia Patients

Simple Summary

Tie2-expressing monocytes (TEM) characterized by the phenotype of CD14+CD16+Tie2+ are seen as the new immunosuppressive force in tumors. However, little is known about the role of circulating TEM in chronic lymphocytic leukemia (CLL) as opposed to their role in solid tumors. In the current study, we observed an increased percentage of TEMs in CLL patients. A greater than 14.82% proportion of TEM foretells an unfavorable prognosis. This threshold has predicted a shorter time from diagnosis to therapy, and worse overall survival. Despite these results, a multivariable Cox regression model performed in 104 CLL patients did not identify TEM as an independent predictor of survival. However, TEM, as an important element of the tumor-microenvironment, can be an important complement to other prognostic indicators.

Abstract

Tie2-expressing monocytes (TEMs) are associated with tumor progression and metastasis. This unique subset of monocytes has been identified as a potential prognostic marker in several solid tumors. However, TEMs remain poorly characterized in hematological cancers, including chronic lymphocytic leukemia (CLL). This study analyzed, for the first time, the clinical significance of TEM population in CLL patients. Flow cytometry analysis of TEMs (defined as CD14⁺CD16⁺Tie2⁺ cells) was performed at the time of diagnosis on peripheral blood mononuclear cells from 104 untreated CLL patients. Our results revealed an expansion of circulating TEM in CLL patients. These monocytes express high levels of VEGF and suppressive IL-10. A high percentage of TEM was associated closely with unfavorable prognostic markers (ZAP-70, CD38, 17p and 11q deletion, and IGHV mutational status). Moreover, increased percentages of circulating TEMs were significantly higher in patients not responding to the first-line therapy as compared to responding patients, suggesting its potential predictive value. High TEM percentage was also correlated with shorter overall survival (OS) and shorter time to treatment (TTT). Importantly, based on multivariate Cox regression analysis, TEM percentage was an independent predictor for TTT. Thus, we can suggest the adverse role of TEMs in CLL.

Alternatively Spliced Form of Angiopoietin-2 as a New Vascular Rheostat

Angiopoietin (ANPGT)-TIE signaling serves as a critical regulator of vessel maturation controlling vascular quiescence, maintenance, and homeostasis (primarily through ANGPT1-TIE2 signaling), as well as enabling vascular plasticity and responsiveness to exogenous cytokines (primarily through antagonistically acting ANGPT2). An alternatively spliced form of ANGPT2 (ANGPT2₄₄₃) was first reported 20 years ago. Yet, little is known to this day about its biological functions. In this issue of Cancer Research, Kapiainen and colleagues report an elegant series of experiments adding to the complexity and contextuality of ANGPT-TIE signaling. The authors studied the function of ANGPT2₄₄₃ in cellular experiments as well as in a genetic model in vivo, revealing that it is proteolytically cleaved into a lower molecular weight isoform (termed ANGPT2_DAP) that lacks the superclustering domain necessary for multimer formation. When compared with full-length ANGPT2, ANGPT2₄₄₃ and ANGPT2_DAP showed lower binding affinity to α5β1 integrin, but were more potent inhibitors of ANGPT1-TIE2 signaling. Functionally, ANGPT2₄₄₃ impaired vessel enlargement and vein morphogenesis during postnatal retinal angiogenesis. Tumor experiments in Angpt2₄₄₃-expressing mice showed enhanced destabilization of the lung vasculature, with varying effects on metastasis. Taken together, the study provides important insight into the significance of ANGPT2 alternative splicing and identifies ANGPT2₄₄₃ and ANGPT2_DAP as a biological rheostat of ANGPT1-TIE2 signaling. Future work will need to characterize the relative ratios and functional contributions of the ANGPT2 variants in different pathophysiologic settings.See related article by Kapiainen et al., p. 129.

Nurse-Like Cells and Chronic Lymphocytic Leukemia B Cells: A Mutualistic Crosstalk inside Tissue Microenvironments

Chronic lymphocytic leukemia (CLL) is the most common adult leukemia in Western countries and is an example of hematological disease where cooperation between genetic defects and tumor microenvironmental interaction is involved in pathogenesis. CLL is a disease that is considered as "addicted to the host"; indeed, the crosstalk between leukemic cells and the tumor microenvironment is essential for leukemic clone maintenance supporting CLL cells' survival, proliferation, and protection from drug-induced apoptosis. CLL cells are not innocent bystanders but actively model and manipulate the surrounding microenvironment to their own advantage. Besides the different players involved in this crosstalk, nurse-like cells (NLC) resemble features related to leukemia-associated macrophages with an important function in preserving CLL cell survival and supporting an immunosuppressive microenvironment. This review provides a comprehensive overview of the role played by NLC in creating a nurturing and permissive milieu for CLL cells, illustrating the therapeutic possibilities in order to specifically target and re-educate them.

The Amino-Terminal Oligomerization Domain of Angiopoietin-2 Affects Vascular Remodeling, Mammary Gland Tumor Growth, and Lung Metastasis in Mice

Angiopoietin-2 (ANGPT2) is a context-dependent TIE2 agonistic or antagonistic ligand that induces diverse responses in cancer. Blocking ANGPT2 provides a promising strategy for inhibiting tumor growth and metastasis, yet variable effects of targeting ANGPT2 have complicated drug development. ANGPT2₄₄₃ is a naturally occurring, lower oligomeric protein isoform whose expression is increased in cancer. Here, we use a knock-in mouse line (mice expressing Angpt2₄₄₃), a genetic model for breast cancer and metastasis (MMTV-PyMT), a syngeneic melanoma lung colonization model (B16F10), and orthotopic injection of E0771 breast cancer cells to show that alternative forms increase the diversity of Angpt2 function. In a mouse retina model of angiogenesis, expression of Angpt2₄₄₃ caused impaired venous development, suggesting enhanced function as a competitive antagonist for Tie2. In mammary gland tumor models, Angpt2₄₄₃ differentially affected primary tumor growth and vascularization; these varying effects were associated with Angpt2 protein localization in the endothelium or in the stromal extracellular matrix as well as the frequency of Tie2-positive tumor blood vessels. In the presence of metastatic cells, Angpt2₄₄₃ promoted destabilization of pulmonary vasculature and lung metastasis. In vitro, ANGPT2₄₄₃ was susceptible to proteolytical cleavage, resulting in a monomeric ligand (ANGPT2_DAP) that inhibited ANGPT1- or ANGPT4-induced TIE2 activation but did not bind to alternative ANGPT2 receptor α5β1 integrin. Collectively, these data reveal novel roles for the ANGPT2 N-terminal domain in blood vessel remodeling, tumor growth, metastasis, integrin binding, and proteolytic regulation. SIGNIFICANCE: This study identifies the role of the N-terminal oligomerization domain of angiopoietin-2 in vascular remodeling and lung metastasis and provides new insights into mechanisms underlying the versatile functions of angiopoietin-2 in cancer.See related commentary by Kamiyama and Augustin, p. 35.

Endothelial dysfunction in patients with lymphoproliferative disorders and its changes in the course of polychemotherapy

The article is dedicated to contemporary views on the change of endothelial function in the patients with lymphoproliferative disorders prior to, and in the process of, chemotherapeutic treatment. Considering that possibilities of standard examination do not always help identifying subclinical endothelial dysfunction, it is necessary to use specific methods, in particular, to determine the levels of endothelin-1 and vascular endothelial growth factor to monitor endothelial function. The objective of this review is to identify problems and prospects for recognizing early subclinical changes of endothelial function in the patients with lymphoproliferative disorders before and after chemotherapy. Assessing presence and severity of endothelial dysfunction may be useful for determining subclinical stages of cardiovascular damage, stratifying the risk of the patients with confirmed cardiovascular disease, and reducing the likelihood of cardio- and endotheliotoxic effects in patients long after chemotherapy. That is why early detection and immediate therapy of cardiovascular toxicity is currently the most important task in the patients with lymphoproliferative disorders, receiving chemotherapy.

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.

Tumor Cell-Derived Angiopoietin-2 Promotes Metastasis in Melanoma

The angiopoietin (Angpt)-TIE signaling pathway controls vascular maturation and maintains the quiescent phenotype of resting vasculature. The contextual agonistic and antagonistic Tie2 ligand ANGPT2 is believed to be exclusively produced by endothelial cells, disrupting constitutive ANGPT1-TIE2 signaling to destabilize the microvasculature during pathologic disorders like inflammation and cancer. However, scattered reports have also portrayed tumor cells as a source of ANGPT2. Employing ISH-based detection of ANGPT2, we found strong tumor cell expression of ANGPT2 in a subset of patients with melanoma. Comparative analysis of biopsies revealed a higher fraction of ANGPT2-expressing tumor cells in metastatic versus primary sites. Tumor cell-expressed Angpt2 was dispensable for primary tumor growth, yet in-depth analysis of primary tumors revealed enhanced intratumoral necrosis upon silencing of tumor cell Angpt2 expression in the absence of significant immune and vascular alterations. Global transcriptional profiling of Angpt2-deficient tumor cells identified perturbations in redox homeostasis and an increased response to cellular oxidative stress. Ultrastructural analyses illustrated a significant increase of dysfunctional mitochondria in Angpt2-silenced tumor cells, thereby resulting in enhanced reactive oxygen species (ROS) production and downstream MAPK stress signaling. Functionally, enhanced ROS in Angpt2-silenced tumor cells reduced colonization potential in vitro and in vivo. Taken together, these findings uncover the hitherto unappreciated role of tumor cell-expressed ANGPT2 as an autocrine-positive regulator of metastatic colonization and validate ANGPT2 as a therapeutic target for a well-defined subset of patients with melanoma. SIGNIFICANCE: This study reveals that tumor cells can be a source of ANGPT2 in the tumor microenvironment and that tumor cell-derived ANGPT2 augments metastatic colonization by protecting tumor cells from oxidative stress.

Effect of the lymphocyte-to-monocyte ratio on the clinical outcome of chemotherapy administration in advanced melanoma patients

Skin cancer affects more individuals in the USA than any other malignancy and malignant melanoma is particularly deadly because of its metastatic potential. Melanoma has been recognized as one of the most immunogenic malignancies; therefore, understanding the mechanisms of tumor-immune interaction is key for developing more efficient treatments. As the tumor microenvironment shows an immunosuppressive action, immunotherapeutic agents promoting endogenous immune response to cancer have been tested (interleukin-2, anticytotoxic-T-lymphocyte-associated antigen 4, and antiprogrammed cell death protein 1 monoclonal antibodies) as well as combinations of cytotoxic chemotherapy agents and inhibitors of angiogenesis (taxol/carboplatin/avastin). However, clinical outcomes are variable, with only a minority of patients achieving durable complete responses. The variability of immune homeostasis, which may be more active or more tolerant at any given time, in cancer patients and the interaction of the immune system with the tumor could explain the inconsistency in clinical outcomes among these patients. Recently, the role of the lymphocyte-to-monocyte-ratio (LMR) in the peripheral blood has been investigated and has been proven to be an independent predictor of survival in different hematological malignancies and in solid tumors. In melanoma, our group has validated the significance of LMR as a predictor of relapse after resection of advanced melanoma. In this study, we examined the dynamics in the immune system of patients with advanced melanoma by performing serial multiday concentration measurements of cytokines and immune cell subsets in the peripheral blood. The analysis of outcomes of chemotherapy administration as related to LMR on the day of treatment initiation showed that progression-free survival was improved in the patients who received chemotherapy on the day when LMR was elevated.

VEGFR2-targeted fusion antibody improved NK cell-mediated immunosurveillance against K562 cells

MHC class I polypeptide-related sequence A (MICA), which is normally expressed on cancer cells, activates NK cells via NK group 2-member D pathway. However, some cancer cells escape NK-mediated immune surveillance by shedding membrane MICA causing immune suppression. To address this issue, we designed an antibody-MICA fusion targeting tumor-specific antigen (vascular endothelial growth factor receptor 2, VEGFR2) based on our patented antibody (mAb04) against VEGFR2. In vitro results demonstrate that the fusion antibody retains both the antineoplastic and the immunomodulatory activity of mAb04. Further, we revealed that it enhanced NK-mediated immunosurveillance against K562 cells through increasing degranulation and cytokine production of NK cells. The overall data suggest our new fusion protein provides a promising approach for cancer-targeted immunotherapy and has prospects for potential application of chronic myeloid leukemia.

Modeling the chronic lymphocytic leukemia microenvironment in vitro

Microenvironments within the lymph node and bone marrow promote proliferation and drug resistance in chronic lymphocytic leukemia (CLL). Successful treatment of CLL must therefore target the leukemic cells within these compartments. A better understanding of the interaction between CLL cells and the tumor microenvironment has led to the development of in vitro models that mimic the mechanisms that support leukemic cell survival and proliferation in vivo. Employing these models as part of the pre-clinical evaluation of novel therapeutic agents enables a better approximation of their potential clinical efficacy. In this review we summarize the current literature describing how different aspects of the tumor microenvironment have been modeled in vitro and detail how these models have been employed to study the biology of the disease and potential efficacy of novel therapeutic agents.

Angiopoietins Modulate Survival, Migration, and the Components of the Ang-Tie2 Pathway of Chronic Lymphocytic Leukaemia (CLL) Cells In Vitro

In actuality, chronic lymphocytic leukaemia (CLL) remains an incurable haematopoietic malignancy of high prevalence amongst elderly populations in the West. Malignant CLL cells characteristically accumulate in the peripheral blood, bone marrow, lymph nodes, and spleen of CLL patients. There is evidence that CLL cells express Ang2 and Tie1, two central components of the Ang-Tie2 pro-angiogenic pathway. Central to blood vessel development and maintenance, at present it remains unclear how the Ang-Tie2 pathway modulates CLL pathophysiology. Here we evaluate the status of the Ang-Tie2 pathway in CLL cells and assess Ang1 levels in plasma/cell medium from CLL samples. To understand how angiopoietins in the microenvironment regulate the components of Ang-Tie2 pathway, survival, migration, and metabolic fitness of CLL cells, we exposed CLL cells to recombinant angiopoietins. CLL plasma and CLL cells in culture present significant lower levels of Ang1. CLL cells simultaneously express Ang1, Ang2, and Tie1 mRNA, but lack that of Tie2 and its regulator, VE-PTP. Exposure to Ang1 confers survival advantage in the long-term, whereas Ang2 and trebananib, an angiopoietin blocker, proved detrimental. Angiopoietins differentially modulate expression of Ang1, Ang2, and Tie1 transcripts. Ang2, but not Ang1, induces the concomitant and transient expression of Tie2 and VE-PTP mRNA. Both angiopoietins, particularly Ang2, increase CLL-Tie1 expression and Ang1 clearly induces chemotaxis and transendothelial-like migration of CLL cells. Besides, changes in caspase and ATP content corroborate the sensitivity of CLL cells to angiopoietin exposure. Altogether, this work shows that angiopoietins regulate the fate of CLL cells in a Tie2-independent manner and highlights the potential of the Ang-Tie2 pathway as a therapeutic target in CLL research.

The progress of angiogenic factors in the development of leukemias

Angiogenic factors have been demonstrated to play important roles in modulating angiogenesis of solid tumors. Recently, accumulating studies extensively indicated that some angiogenic factors widely exist in malignant cells of hematologic malignancy, which regulated the expression of a number of genes that were involved in abnormal proliferation, differentiation and apoptosis of these cells. With deep research of angiogenic factors, its expression, function and regulatory mechanism were gradually elucidated, and some of them were related to the development and prognosis of leukemia, or provide more possible strategies for treatment of patients with leukemia. Herein, we summarize the progress in study of some important angiogenic factors and hematological malignancies.

Signaling and molecular basis of bone marrow niche angiogenesis in leukemia

Angiogenesis, the process of blood vessel formation, is necessary for tissue survival in normal and pathologic conditions. Increased angiogenesis in BM niche is correlated with leukemia progression and resistance to treatment. Angiogenesis can interfere with disease progression and several angiogenic (such as vascular growth factors) as well as anti-angiogenic factors (i.e. angiostatin) can affect angiogenesis. Furthermore, miRs can affect the angiogenic process by inhibiting angiogenesis or increasing the expression of growth factors. Given the importance of angiogenesis in BM for maintenance of leukemic clones, recognition of angiogenic and anti-angiogenic factors and miRs as well as drug resistance mechanisms of leukemic blasts can improve the therapeutic strategies. We highlight the changes in angiogenic balance within the BM niche in different leukemia types. Moreover, we explored the pathways leading to drug resistance in relation to angiogenesis and attempted to assign interesting candidates for future research.

Angiopoietin-2 in Bone Marrow milieu promotes Multiple Myeloma-associated angiogenesis

Angiopoietin-2 (Ang-2) is involved in angiogenesis in both solid and hematological malignancies. In Multiple Myeloma (MM), serum Ang-2 correlates with disease progression and response to therapy. To address the patho-physiologic role of Ang-2 in MM associated angiogenesis, we used sera from patients with active MM, which contained significantly higher levels of the molecule, compared to those from patients with smoldering MM and Monoclonal Gammopathy of Undetermined Significance. MM Bone Marrow (BM) sera with high Ang-2 concentration specifically contributed to endothelial cell (EC) activation, while Ang-1 containing sera maintained EC stabilization. The functional dichotomy of Ang-1 and Ang-2 was confirmed by the triggering of distinctive signaling pathways down-stream the common Tie-2 receptor, i.e., the Akt or the ERK- phosphorylation pathway. Notably, Ang-2 but not VEGF serum levels correlated with BM micro-vessel density, further underscoring the key role of Ang-2 in angiogenesis. Western Blot, RT-PCR and immunocytochemistry identified MMEC as the major source of Ang-2, at variance with MM cells and CD14(+) BM monocytes. These data suggest that Ang-2 produced in the BM milieu may contribute to MM angiogenesis and suggest that the molecule can be further exploited both as angiogenesis biomarker and as a potential therapeutic target.

Angiogenic factors in chronic lymphocytic leukaemia (CLL): Where do we stand?

The role of angiogenesis in haematological malignancies such as chronic lymphocytic leukaemia (CLL) is difficult to envision, because leukaemia cells are not dependent on a network of blood vessels to support basic physiological requirements. Regardless, CLL cells secrete high levels of major angiogenic factors, such as vascular endothelial growth factor (VEGF), basic fibroblast growth factor (bFGF), and platelet derived growth factor (PDGF). Nonetheless, it remains unclear how most angiogenic factors regulate accumulation and delayed apoptosis of CLL cells. Angiogenic factors such as leptin, granulocyte colony-stimulating factor (G-CSF), follistatin, angiopoietin-1 (Ang1), angiogenin (ANG), midkine (MK), pleiotrophin (PTN), progranulin (PGRN), proliferin (PLF), placental growth factor (PIGF), and endothelial locus-1 (Del-1), represent novel therapeutic targets of future CLL research but have remained widely overlooked. This review aims to outline our current understanding of angiogenic growth factors and their relationship with CLL, a still uncured haematopoietic malignancy.

FCR and bevacizumab treatment in patients with relapsed chronic lymphocytic leukemia

BACKGROUND

Patients with relapsed chronic lymphocytic leukemia (CLL) often achieve response with chemoimmunotherapy but have short remission durations. Studies have shown that patients with CLL have increased angiogenesis in the microenvironment; levels of proangiogenic growth factors such as VEGF and/or angiopoietin-2 are also elevated. Increased angiogenesis correlates with poor outcome in CLL. Bevacizumab (B) is a humanized monoclonal antibody targeting VEGF-A.

METHODS

In this study, we analyzed whether a combination of bevacizumab with fludarabine, cyclophosphamide, and rituximab chemoimmunotherapy (FCR-B) could improve outcomes in patients with relapsed CLL. Sixty-two patients were enrolled. The median age of the patients was 60 years (range, 31-84 years) and 40% had received >1 prior therapy for CLL. Sixty-one patients were evaluable for toxicity, and 57 were evaluable for response. Six cycles were planned; 36 patients (59%) completed ≥4-6 cycles of the regimen.

RESULTS

The overall response rate was 79%, with 13 (23%) complete remissions (CRs), 8 nodular partial remissions (14%), and 24 partial remissions (43%). The median progression-free survival and overall survival rates were 13.5 and 45 months, respectively. Grade 3 or 4 toxicities included febrile neutropenia (n = 40), infections (n = 21), thrombocytopenia (n = 18) and anemia (n = 9).

CONCLUSIONS

Results with FCR-B were similar to those observed with an historical cohort of relapsed patients treated with FCR.

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.

Immunohistochemical analysis of IL-6, IL-8/CXCR2 axis, Tyr p-STAT-3, and SOCS-3 in lymph nodes from patients with chronic lymphocytic leukemia: correlation between microvascular characteristics and prognostic significance

A number of studies have looked into the pathophysiological role of angiogenesis in CLL, but the results have often been inconsistent. We aimed to gain direct insight into the angiogenic process in lymph nodes involved by CLL, focusing on proangiogenic cytokines and microvessel morphometry. The tissue levels of VEGF, Th-2 cytokines IL-6 and IL-8, IL-8 receptor CXCR2, and tyrosine p-STAT-3/SOCS-3 axis modulating cytokine expression were evaluated immunohistochemically in 62 CLL/SLL cases. Microvascular characteristics were evaluated by image analysis. Results were analyzed with regard to clinicopathological characteristics. Proliferation centers (PCs) were less well vascularised compared to non-PC areas. IL-8 and CXCR2 expression was distinctly uncommon as opposed to IL-6, VEGF and SOCS-3, which were detected in the vast majority of cases. The latter two molecule expressions were more pronounced in the PCs in ∼40% of the cases. p-STAT-3 immunoreactivity was recorded in 66.67% of the cases with a predilection for PCs. Microvessel morphometry was unrelated to proangiogenic cytokines, p-STAT-3, SOCS-3, or survival. Microvascular caliber and VEGF expression were higher in Binet stage A, whereasIL-6 expression was higher in stage C. VEGF and p-STAT-3 exerted a favorable effect on progression, which remained significant in multivariate analysis, thereby constituting potential outcome predictors in CLL patients.

The PI3-kinase delta inhibitor idelalisib (GS-1101) targets integrin-mediated adhesion of chronic lymphocytic leukemia (CLL) cell to endothelial and marrow stromal cells

CLL cell trafficking between blood and tissue compartments is an integral part of the disease process. Idelalisib, a phosphoinositide 3-kinase delta (PI3Kδ) inhibitor causes rapid lymph node shrinkage, along with an increase in lymphocytosis, prior to inducing objective responses in CLL patients. This characteristic activity presumably is due to CLL cell redistribution from tissues into the blood, but the underlying mechanisms are not fully understood. We therefore analyzed idelalisib effects on CLL cell adhesion to endothelial and bone marrow stromal cells (EC, BMSC). We found that idelalisib inhibited CLL cell adhesion to EC and BMSC under static and shear flow conditions. TNFα-induced VCAM-1 (CD106) expression in supporting layers increased CLL cell adhesion and accentuated the inhibitory effect of idelalisib. Co-culture with EC and BMSC also protected CLL from undergoing apoptosis, and this EC- and BMSC-mediated protection was antagonized by idelalisib. Furthermore, we demonstrate that CLL cell adhesion to EC and VLA-4 (CD49d) resulted in the phosphorylation of Akt, which was sensitive to inhibition by idelalisib. These findings demonstrate that idelalisib interferes with integrin-mediated CLL cell adhesion to EC and BMSC, providing a novel mechanism to explain idelalisib-induced redistribution of CLL cells from tissues into the blood.

Psychosocial factors and hematopoietic stem cell transplantation: potential biobehavioral pathways

While psychosocial factors are known to affect cancer progression via biobehavioral pathways in many patient populations, these relationships remain largely unexplored in hematopoietic stem cell transplant (HCT) patients. The purpose of this paper is to critically review the literature regarding psychosocial and endocrine/immune aspects of HCT, with an emphasis on exploring pathways that may mediate the associations between psychosocial factors and disease outcomes. These include the roles of catecholamines, glucocorticoids, inflammation, vascular endothelial growth factor (VEGF), immune reconstitution and infectious susceptibility, as well as the new opportunities available in genomics research. We also discuss the implications for potential immunomodulating psychosocial interventions. Elucidating the biological pathways that account for the associations between psychosocial factors and clinical course could ultimately lead to improved outcomes for this psychologically and immunologically vulnerable population.

Stanniocalcin-1 and -2 promote angiogenic sprouting in HUVECs via VEGF/VEGFR2 and angiopoietin signaling pathways

The members of stanniocalcins (STCs: STC-1 and STC-2) family are known to be involved in tumor progression and metastasis. Although current evidences suggest the involvement of STCs in vascular biology, the functional roles of STCs in angiogenesis have not yet been elucidated. The objective of this study was to decipher the roles of STCs in angiogenesis of human umbilical vascular endothelial cells (HUVECs). We prepared STC1 or STC2 lentiviral particles to transduce the cells to reveal their effects on the processes of cell proliferation, migration and tube formation. The stimulatory effects of STCs on these processes were demonstrated, supporting the notion of STCs in angiogenesis. To dissect the molecular components involved, STC1 or STC2 transduction led to significant increases in the expression levels of cell cycle regulators (i.e. cyclin-D and phospho-retinoblastoma), matrix metalloproteinase (MMP)-2 but a decrease of tissue inhibitors of metalloproteases (TIMP)-1. The expression levels of the cell adhesion/junctional proteins vimentin and VE-cadherin, were significantly induced. Moreover the transduction induced both mRNA and protein levels of eNOS, VEGF and VEGFR2 (KDR mRNA and pKDR), highlighting the stimulatory effects of STCs on VEGF-signaling pathway. Furthermore STC2 transduction but not STC1, activated angiopoietin (Ang)-2 pathway. Taken together, STC1 and STC2 play positive roles in angiogenic sprouting. The action of STC1 was mediated via VEGF/VEGFR2 pathway while STC2 were mediated via VEGF/VEGFR2 and Ang-2 pathways.

ANGPT2 promoter methylation is strongly associated with gene expression and prognosis in chronic lymphocytic leukemia

Increasing evidence suggests a key role for angiopoietin-2 (ANGPT2) in influencing the aggressiveness of chronic lymphocytic leukemia (CLL). In the presence of vascular endothelial growth factor (VEGF), ANGPT2 causes vessel destabilization leading to neoangiogenesis. Accordingly, high expression levels of ANGPT2 and high degree of angiogenesis have consistently been associated with poor prognosis in CLL; however, the molecular mechanisms behind the variability in ANGPT2 expression are still to be discovered. Here, for the first time, we investigated the DNA methylation status of the ANGPT2 promoter in a large CLL cohort (n = 88) using pyrosequencing and correlated methylation data with ANGPT2 expression levels, prognostic factors and outcome. Importantly, methylation levels of the ANGPT2 gene correlated inversely with its mRNA expression levels (p<0.001). Moreover, low ANGPT2 methylation status was highly associated with adverse prognostic markers, shorter time to first treatment and overall survival. Finally, treatment with methyl inhibitors induced re-expression of ANGPT2 in two B-cell lymphoma cell lines, underscoring the importance of DNA methylation in regulating transcriptional silencing of this gene. In conclusion, we believe that the known variability in ANGPT2 expression among CLL patients could be explained by differential promoter DNA methylation and that low methylation levels of the ANGPT2 promoter have an adverse prognostic impact in CLL.

Angiogenesis as a treatment target in leukemia

SUMMARY The importance of angiogenesis in the growth and survival of leukemia has been well established and confirmed by several studies. In the last 20 years, several antiangiogenic agents have been used in preclinical and clinical studies of the treatment of leukemia. This review article summarizes the literature focusing on the relationship between angiogenesis and disease progression, and the advantages and limits of the antiangiogenic treatment of leukemia.

Cross-talk between leukemic and endothelial cells promotes angiogenesis by VEGF activation of the Notch/Dll4 pathway

Angiogenesis is suggested to be important for leukemogenesis and chemosensitivity in acute myeloid leukemia (AML). The vascular endothelial growth factor (VEGF) and Notch/Dll4 pathways have been identified as critical in the regulation of embryonic vascular development and tumor angiogenesis. However, the potential role of the Notch/Dll4 pathway in leukemia-endothelium cross-talk and its functional link with VEGF remains obscure. This study assessed the expression of VEGF and Notch/Dll4 pathway molecules in primary AML and investigated their biological function in the coculture of endothelial cells with AML cells. The results demonstrated that bone marrow vascularity in the newly diagnosed AML patients was increased and correlated with high VEGF and Dll4 expression. Patients with untreated AML expressed higher levels of VEGFR2, Notch1, Dll4 and Hes1 than healthy controls. Moreover, the activation of the Notch/Dll4 pathway is associated with poor prognosis in AML. In addition, AML cells were shown to increase endothelial cell proliferation in Transwell coculture. This was associated with concomitant activation of the Notch/Dll4 pathway and upregulation of its downstream genes, such as matrix metalloproteinases, resulting in the enhancement of endothelial cell migration and tube formation. Our study also showed that upregulation of Dll4 expression in AML cells by cDNA transfection suppressed VEGF-induced endothelial cell proliferation and angiogenesis in direct contact coculture. These results elucidate a novel mechanism by which the interplay between AML and endothelial cells promotes angiogenesis through the Notch/Dll4 pathway. Modulation of this pathway may, therefore, hold promise as a novel antiangiogenic strategy for the treatment of AML.

Prognostic impact of δ-like ligand 4 and Notch1 in acute myeloid leukemia

Notch signaling plays a critical role in embryonic vascular development and tumor angiogenesis. The present study was conducted to investigate the prognostic role of the angiogenesis-related Notch ligand and the receptor in acute myeloid leukemia (AML) and assess whether their expression correlates with that of the vascular endothelial growth factor (VEGF) and angiopoietin (Ang)-2. Bone marrow mononuclear cells from 60 untreated AML patients and 40 healthy controls were obtained. Real-time RT-PCR was performed to evaluate the mRNA expression of δ-like ligand 4 (Dll4), Notch1, VEGF, VEGF receptor (VEGFR)-1, VEGFR-2, Ang-1, Ang-2 and Tie2. Western blot analysis was used to determine the protein levels of Dll4 and Notch1. The results demonstrated that Dll4, Notch1, VEGF, VEGFR-2 and Ang-2 expression were significantly higher in untreated AML patients than in the controls. Univariate analysis of factors associated with the overall survival showed a significantly shorter survival in patients with the unfavorable karyotype, higher Dll4 expression, higher Notch1 expression, higher VEGF expression or higher Ang-2 expression. Furthermore, multivariate analysis revealed that the karyotype and expression levels of Notch1, Dll4, VEGF and Ang-2 were independent prognostic factors for overall survival. Additionally, the prognostic value of Dll4 expression (but not Notch1) was more significant in the subgroup consisting of patients with intermediate-risk cytogenetics. Subgroup analysis showed that Notch1 and Dll4 expression levels had a prognostic impact on patients with high VEGF or Ang-2 levels. Taken together, our data provide evidence that the activation of the Notch pathway may indicate an unfavorable prognosis in AML. In particular, Dll4 may be a relevant prognostic marker in intermediate-risk AML.

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.

Physical contact with endothelial cells through β1- and β2- integrins rescues chronic lymphocytic leukemia cells from spontaneous and drug-induced apoptosis and induces a peculiar gene expression profile in leukemic cells

BACKGROUND

Chronic lymphocytic leukemia B cells display prolonged survival in vivo, but when cultured in vitro rapidly undergo spontaneous apoptosis. We hypothesize that interactions with endothelial cells in infiltrated tissues and during recirculation may have a pathogenic role in chronic lymphocytic leukemia.

DESIGN AND METHODS

We evaluated apoptosis of leukemic cells after co-culture on a monolayer of human umbilical vein endothelial cells with addition of fludarabine and antibodies that block adhesion. Then, we compared microarray-based gene expression profiles between leukemic cells at baseline and after co-culture.

RESULTS

We found that the endothelial layer protected leukemic cells from apoptosis inducing a 2-fold mean decrement in apoptotic cells after 2 days of co-culture. Moreover, the endothelial layer decreased the sensitivity of chronic lymphocytic leukemia B cells to fludarabine-induced apoptosis. Physical contact with endothelium mediated by both β(1)- and β(2)- integrins is essential for the survival advantage of leukemic cells. In particular, blocking CD106 on endothelial cells or CD18 on leukemic B cells led to the almost complete abrogation of the survival advantage (>70% inhibition of viability). However, a reduction of apoptosis was also measured in leukemic cells cultured in conditioned medium collected after 2 days of co-culture, implying that survival is partially mediated by soluble factors. Overall, the contact with endothelial cells modulated 1,944 genes in chronic lymphocytic leukemia B cells, establishing a peculiar gene expression profile: up-regulation of angiogenesis-related genes, an increase of genes involved in TGFβ and Wnt signaling pathways, secretion of cytokines recruiting stromal cells and macrophages and up-regulation of anti-apoptotic molecules such as Bcl2 and Survivin.

CONCLUSIONS

Our study supports the notion that endothelial cells are major players in the chronic lymphocytic leukemia microenvironment. Adhesion to endothelium strongly supports survival, protects from drug-induced apoptosis and extensively modifies the gene expression profile of leukemic cells.

Angiogenesis: A Target in Solid Tumors, Also in Leukemia?

Targeting angiogenesis has become an established therapeutic approach to fighting solid tumor growth in cancer patients. Even though increased angiogenesis has long been recognized in various types of hematologic malignancies, the molecular basis underlying this angiogenic switch in leukemias remains poorly understood. The BM stroma is gaining increasing attention for its role in promoting leukemia growth and resistance against current treatments with tyrosine kinase inhibitors. This article provides a brief overview of the role of angiogenesis in leukemias, discusses recent insights into the role of placenta growth factor (PlGF), a VEGF family member, as a novel disease candidate in chronic myeloid leukemia (CML), and highlights the therapeutic potential of PlGF blockade for imatinib-resistant CML.

Role of ZNRD1 (zinc ribbon domain-containing 1) in angiogenesis of leukaemia cells

Here, we have first investigated the roles of ZNRD1 in angiogenesis of leukaemia. The leukaemia cell line K562 was transfected with the vector that included the full-length cDNA of ZNRD1, then the growth and angiogenesis of cells were detected. Up-regulation of ZNRD1 could significantly inhibit the growth of cells, reduce tumour microvessel densities and inhibit the VEGF (vascular endothelial growth factor) production. The results of human miRNA array and real-time PCR showed that ZNRD1 could significantly up-regulate the expression of miR-214 and down-regulate the expression of miR-296. Taken together, ZNRD1 might inhibit tumour angiogenesis and could be considered as a target for leukaemia therapy.

Loss or inhibition of stromal-derived PlGF prolongs survival of mice with imatinib-resistant Bcr-Abl1(+) leukemia

Imatinib has revolutionized the treatment of Bcr-Abl1(+) chronic myeloid leukemia (CML), but, in most patients, some leukemia cells persist despite continued therapy, while others become resistant. Here, we report that PlGF levels are elevated in CML and that PlGF produced by bone marrow stromal cells (BMSCs) aggravates disease severity. CML cells foster a soil for their own growth by inducing BMSCs to upregulate PlGF, which not only stimulates BM angiogenesis, but also promotes CML proliferation and metabolism, in part independently of Bcr-Abl1 signaling. Anti-PlGF treatment prolongs survival of imatinib-sensitive and -resistant CML mice and adds to the anti-CML activity of imatinib. These results may warrant further investigation of the therapeutic potential of PlGF inhibition for (imatinib-resistant) CML.

In vitro effect of aspartame in angiogenesis induction

Aspartame (APM) is the most widely used artificial sweetener and is added to a wide variety of foods, beverages, drugs, and hygiene products. In vitro and in vivo tests have reported contradictory data about APM genotoxicity. We evaluated the angiogenic effect of APM in an in vitro model using blood vessel development assay (Angio-Kit), cultured endothelial cells and fibroblasts. The release of IL-6, VEGF-A, and their soluble receptors sIL-R6 and sVEGFR-2 were determined over time in the conditioned medium of the Angio-Kit system, endothelial cells and cell lines with fibroblast properties after APM treatment. Reactive oxygen species (ROS) formation, cell viability, and stimulation of the extracellular signal-regulated kinases (erk1/2) and protein p38 were also evaluated. Exposure to APM induced blood vessel formation. ROS production was observed in endothelial cells after APM treatment, which was associated with a slight cell cytotoxicity. Neither intracellular ROS formation nor cell death was observed in fibroblasts. APM increases the levels of inflammatory mediator IL-6, VEGF and their soluble receptors released from endothelial cells into the medium. APM treatment induces VEGF-pathway activation by erk1/2 and p38 phosphorylation. APM at low doses is an angiogenic agent that induces regenerative cytokine production leading to the activation of MAPKs and resulting in the formation of new blood vessels.

Determination of genes and microRNAs involved in the resistance to fludarabine in vivo in chronic lymphocytic leukemia

BACKGROUND

Chronic lymphocytic leukemia (CLL) cells are often affected by genomic aberrations targeting key regulatory genes. Although fludarabine is the standard first line therapy to treat CLL, only few data are available about the resistance of B cells to this purine nucleoside analog in vivo. Here we sought to increase our understanding of fludarabine action and describe the mechanisms leading to resistance in vivo. We performed an analysis of genomic aberrations, gene expression profiles, and microRNAs expression in CLL blood B lymphocytes isolated during the course of patients' treatment with fludarabine.

RESULTS

In sensitive patients, the differentially expressed genes we identified were mainly involved in p53 signaling, DNA damage response, cell cycle and cell death. In resistant patients, uncommon genomic abnormalities were observed and the resistance toward fludarabine could be characterized based on the expression profiles of genes implicated in lymphocyte proliferation, DNA repair, and cell growth and survival. Of particular interest in some patients was the amplification of MYC (8q) observed both at the gene and transcript levels, together with alterations of myc-transcriptional targets, including genes and miRNAs involved in the regulation of cell cycle and proliferation. Differential expression of the sulfatase SULF2 and of miR-29a, -181a, and -221 was also observed between resistant and sensitive patients before treatment. These observations were further confirmed on a validation cohort of CLL patients treated with fludarabine in vitro.

CONCLUSION

In the present study we identified genes and miRNAs that may predict clinical resistance of CLL to fludarabine, and describe an interesting oncogenic mechanism in CLL patients resistant to fludarabine by which the complete MYC-specific regulatory network was altered (DNA and RNA levels, and transcriptional targets). These results should prove useful for understanding and overcoming refractoriness to fludarabine and also for predicting the clinical outcome of CLL patients before or early during their treatment.

Angiopoietin-2 plasma dosage predicts time to first treatment and overall survival in chronic lymphocytic leukemia

The clinical relevance of angiopoietin-2 (Ang2) in chronic lymphocytic leukemia (CLL) was previously suggested by the association between high Ang2, and shorter progression-free survival reported in small series of patients. Here, we evaluated Ang2 glycoprotein levels in plasma samples collected from a multicentric cohort of CLL patients (n = 316) using an enzyme-linked immunosorbent assay method, and we investigated its prognostic role in relation to time to first treatment (TTFT) and overall survival. Based on a cutoff equal to 2459 pg/mL, we divided our cohort in 2 subsets (high and low Ang2) composing 100 (31.6%) and 216 (68.4%) patients, respectively. High Ang2 was predictive of reduced TTFT (P < .001) and overall survival (P = .002). Multivariate analysis confirmed that high Ang2 was an independent prognosticator for TTFT (hazard ratio = 1.739; 95% confidence interval, 1.059-2.857; P = .029). Significant associations were found between high Ang2 and advanced Binet stages (P < .001), high beta(2)-microglobulin (P < .001), unmutated variable region of immunoglobulin heavy chain gene status (P < .001), high CD38 and zeta-chain-associated protein kinase 70 expression (P < .001 and P = .003), and intermediate/high cytogenetic risk (P = .005). Moreover, Ang2 added prognostic power to other conventional prognosticators and helped to refine prognosis among CLL subsets with both high and low vascular endothelial growth factor plasma levels. Ang2 plasma level may be a useful independent prognosticator for CLL.