Increased bone marrow angiogenesis in B cell chronic lymphocytic leukemia

Kaposi's sarcoma-associated herpesvirus glycoproteins B and K8.1 regulate virion egress and synthesis of vascular endothelial growth factor and viral interleukin-6 in BCBL-1 cells

Kaposi's sarcoma-associated herpesvirus (KSHV) viral glycoproteins play important roles in the infectious life cycle and have been implicated in KSHV-associated endothelial cell transformation, angiogenesis, and KS-induced malignancies. KSHV-associated primary effusion lymphomas (PELs) secrete high levels of vascular endothelial growth factor (VEGF) and viral interleukin-6 (vIL-6) in vitro and VEGF, vIL-6, and basic-fibroblast growth factor (b-FGF) in mouse xenografts. KSHV-encoded glycoproteins B (gB) and K8.1 stimulate VEGF secretion, most likely mediated by direct or indirect binding to cell surface receptors, including the gB-specific alphaVbeta3 and alpha3beta1 integrins. In this study, the short interfering RNA (siRNA)-mediated inhibition of either gB or K8.1 transcription by anti-gB or -K8.1 siRNAs caused a substantial reduction in virion egress and a decrease in both vIL-6 and VEGF production. Similarly, the treatment of BCBL-1 cells with anti-gB or anti-K8.1 antibodies caused a substantial reduction in vIL-6 and VEGF production. Codon-optimized versions of either wild-type gB, mutant gB having the RGD amino acid motif changed to RAA, or K8.1 efficiently rescued virion egress and VEGF and vIL-6 production. These results suggest that the binding of gB via its RGD motif to integrin receptors was not responsible for the observed gB-associated regulation of VEGF and vIL-6 transcription. Conditioned medium collected from BCBL-1 cells transfected with anti-gB and anti-K8.1 siRNAs or treated with anti-gB and anti-K8.1 antibodies exhibited a significantly reduced ability to induce the formation of the capillary network of endothelial cells compared to the ability of medium from mock-infected BCBl-1 cells. Furthermore, medium obtained from BCBL-1 cells expressing smaller amounts of gB and K8.1 produced a substantial reduction in endothelial cell migration in a vertical migration assay compared to that of control medium containing wild-type levels of gB and K8.1. These results suggest a functional linkage between gB/K8.1 synthesis and VEGF/vIL-6 transcriptional regulation via paracrine and/or autocrine signaling pathways.

VEGF/VEGFR2 interaction down-regulates matrix metalloproteinase-9 via STAT1 activation and inhibits B chronic lymphocytic leukemia cell migration

B-cell chronic lymphocytic leukemia (B-CLL) migration involves several molecules, including matrix metalloproteinase-9 (MMP-9) and vascular endothelial growth factor (VEGF). We have studied whether VEGF regulates MMP-9. VEGF significantly reduced MMP-9 protein expression in a dose-dependent manner, measured by gelatin zymography. Blocking the VEGFR2 receptor restored MMP-9 levels, implicating this receptor in the observed effect. Down-regulation of MMP-9 by VEGF resulted in significant inhibition of B-CLL cell migration through Matrigel or human umbilical vein endothelial cells, confirming the crucial role of MMP-9 in these processes. Reverse-transcription polymerase chain reaction analyses revealed that VEGF regulated MMP-9 at the transcriptional level. Indeed, VEGF induced STAT1 tyrosine phosphorylation, and this was blocked by inhibiting VEGFR2. STAT1 was responsible for MMP-9 down-regulation, as STAT1 gene silencing restored MMP-9 production and B-CLL cell migration in the presence of VEGF. Thus, the levels of VEGF and MMP-9 influence B-CLL cell expansion and both molecules could constitute therapeutic targets for this disease.

The prognostic significance of VEGF-C and VEGF-A in non-Hodgkin lymphomas

Angiogenesis and lymphangiogensis are important in the proliferation and survival of the malignant hemeopoietic neoplasms. The aim of this study is to determine the prognostic role of angiogenesis and lymphangiogenesis in the development of lymphoma. For this aim, VEGF-A and VEGF-C were explored by immunohistochemistry in 177 cases. VEGF-C and VEGF-A were found to be positive in 34 and 61% of the samples. There was a good correlation between VEGF-C and VEGF-A expression (p = 0.0001). The clinical prognostic indicators were not significantly different between VEGF-C (+) and (-) and/or VEGF-A (+) and (-) cases. Overall survival (OS) rate was shorter in cases with VEGF-A (+) and VEGF-C (+) cases than with negative cases (p = 0.03 and p = 0.0005, respectively). The OS was significantly shorter in aggressive lymphomas expressing VEGF-A and VEGF-C but not in indolent lymphomas. The results of Cox regression analyses showed that VEGF-A and VEGF-C expressions are independent prognostic parameters (OR: 2.6, 95% CI: 1.3-5.0 for both (+) cases). In conclusion, VEGF-C and VEGF-A were positive in 34 and 61%, respectively, of the cases with NHL. The significant correlation between VEGF-C and VEGF-A suggests that lymphangiogenesis is important in the pathogenesis of lymphomas as shown in angiogenesis. The significantly shorter survival rates of VEGF-C and/or VEGF-A expressions indicate that angiogenesis and lymphangiogenesis are important in clinical outcome. Autocrine VEGF-A and VEGF-C crosstalks in lymphoma cells are important in lymphoma biology and inhibition of these signals with anti-angiogenic/anti-lymphangiogenic drugs and combination with chemo-immunotherapy regimens will be more useful in these cases.

Vascular density in childhood acute lymphoblastic leukaemia correlates to biological factors and outcome

The issue of angiogenesis and its clinical relevance in childhood acute lymphoblastic leukaemia (ALL) is controversial. In the present study, microvessel density (MVD), analysed in 185 diagnostic bone marrow biopsies, was higher in T-cell ALL compared to B-cell precursor (BCP)-ALL (P = 0.013). In the BCP group, cases with t(12;21) were characterized by a low MVD while patients with high-hyperdiploid leukaemia (HeH, 51-61 chromosomes) showed a high MVD compared to other BCP patients (P = 0.001 and 0.002 respectively). There was a correlation between MVD and white blood cell (WBC) count in high-risk BCP patients (P = 0.021). In addition, BCP patients with a high marrow reticulin fibre density and high MVD had an unfavourable outcome compared to the other BCP patients (P = 0.002). The fraction of vessels in which lumina were filled with blasts (blast congested vessel fraction) correlated strongly with WBC count (P < 0.001). These findings indicate that the angiogenic process interacts with other stroma-factors, such as reticulin fibre density, in its effect on outcome, and is coupled to both the ALL genotype and phenotype. One possible implication is that different subtypes of childhood ALL may respond differently to anti-angiogenic drugs as a supplement in first-line treatment.

N9986: a phase II trial of thalidomide in patients with relapsed chronic lymphocytic leukemia

We enrolled 28 eligible patients with relapsed chronic lymphocytic leukemia (CLL) to a phase II study of single agent thalidomide (200 mg/d, with dose escalation up to 1000 mg/d over 60 days). The median age was 66 years and 71% were males. Study participants received a median of 2 (range 1-7) prior treatment regimens and 61% had Rai stage 3-4 disease at enrollment. Grade 3 or higher hematologic toxicity was observed in 13 (46%) and 16 (57%) had grade 3 or higher non-hematologic toxicity. Grade 3-4 tumor flare was observed in five (18%) patients. The overall response rate was 11% (3 of 28) with one (4%) complete remission and two (7%) partial remissions. Duration of response for these three responders was 3, 14 and 15 months. Fourteen (50%) patients had stabilisation of disease for a median duration of 8 months (95% CI: 7-16 months). Median time to progression for all 28 patients was 7.3 months. Although thalidomide appears to have modest clinical activity in pretreated/relapsed CLL primarily based on reduction of the absolute lymphocyte count, in our opinion the toxicity profile precludes it from more active investigation in CLL.

Aberrant regulation of pVHL levels by microRNA promotes the HIF/VEGF axis in CLL B cells

The molecular mechanism of autocrine regulation of vascular endothelial growth factor (VEGF) in chronic lymphocytic leukemia (CLL) B cells is unknown. Here, we report that CLL B cells express constitutive levels of HIF-1alpha under normoxia. We have examined the status of the von Hippel-Lindau gene product (pVHL) that is responsible for HIF-1alpha degradation and found it to be at a notably low level in CLL B cells compared with normal B cells. We demonstrate that the microRNA, miR-92-1, overexpressed in CLL B cells, can target the VHL transcript to repress its expression. We found that the stabilized HIF-1alpha can form an active complex with the transcriptional coactivator p300 and phosphorylated-STAT3 at the VEGF promoter and recruit RNA polymerase II. This is initial evidence that pVHL, without any genetic alteration, can be regulated by microRNA and explains the aberrant autocrine VEGF secretion in CLL.

Choice of endothelial marker is crucial for assessment of bone marrow microvessel density in chronic lymphocytic leukemia

Angiogenesis is a potential prognostic factor in chronic lymphocytic leukemia (CLL). Elevated circulating levels of angiogenic factors in CLL have been repeatedly reported. Nevertheless, the issue of bone marrow neovascularization in CLL remains controversial, partly due to limited number of published studies, different methods of assessing microvessel density (MVD) and small patient cohorts. Moreover, there are very scarce data regarding the relationship of marrow angiogenesis to prognostic markers in CLL. Our objectives were: 1. To assess bone marrow MVD in CLL using two different monoclonal antibodies and a reproducible method of MVD quantification; 2. To examine the possible association of marrow MVD and clinical course, pattern of marrow infiltration, Rai stage, cytogenetic abnormalities detected by fluorescence in situ hybridization (FISH), and mutation status of immunoglobulin heavy chain variable region (IgVH). MVD was higher using CD34 vs vWF antibody (p<0.0001). However, no MVD differences were detected between CLL subgroups subdivided according to the above-mentioned prognostic factors. In conclusion, MVD assessment using anti-CD34 resulted in higher MVD counts than when using anti-vWF antibody. No association of MVD with any prognostic factors was observed, possibly due to the limited patient cohort. As the need for bone marrow trephine biopsies in CLL is significantly decreasing, a standardized method of neovascularization assessment is required to enable possible multicentre studies in order to conduct larger investigations and thereby shed more light on the real clinical significance of bone marrow angiogenesis in CLL.

Evaluation of circulating endothelial cells as noninvasive marker of angiogenesis in patients with chronic lymphocytic leukemia

An increased angiogenesis has been documented in bone marrow and lymph nodes of patients with chronic lymphocytic leukemia (CLL). There is accumulating evidence that circulating endothelial cells (CECs) play an important role in angiogenesis. The aim of our study was to compare the number of CECs in peripheral blood of CLL patients and healthy donors and to correlate these numbers with bone marrow microvessel density (MVD) and known prognostic factors in CLL. Proportions of resting CECs (rCECs), activated CECs (aCECs), apoptotic CECs (apoCECs) and circulating precursor endothelial cells (CPECs) were estimated by flow cytometry in 104 untreated CLL patients and 29 healthy blood donors. The MVD was analysed in the bone marrow biopsy in 21 CLL patients and 11 controls using the 'hot spot analysis' of vessels' density (x200 HPS). We found significantly higher numbers of CPECs, rCECs, aCECs and apoCECs in CLL patients than in healthy controls (p < 0.001 for all comparisons). Furthermore, the rCECs number was higher in advanced versus low clinical stage CLL (median 17.5 cells/microL vs. 13.5 cells/microL, p = 0.05). The MVD was significantly higher in the bone marrow of CLL patients when compared with controls (p = 0.016). However, we did not find any correlation between MVD and different CECs populations. In conclusion, the number of CECs is increased in CLL and correlates with stage of the disease, but does not seem to directly reflect the intensity of neovascularisaton in the bone marrow.

Evaluation of circulating endothelial cells, VEGF and VEGFR2 serum levels in patients with chronic myeloproliferative diseases

Authors evaluated some markers of angiogenetic activity in patients with chronic myeloproliferative diseases (CMDs). In this study by using a cytofluorimetric analysis we evaluated circulating endothelial progenitor cells (EPCs) in patients with chronic myeloproliferative disease. Moreover, in the same group of subjects, we evaluated serum levels of vascular endothelial growth factor (VEGF) and vascular endothelial growth factor receptor-2 (VEGFR2). In our patients, we have found an increase in the number of endothelial progenitor cells in primary myelofibrosis (PMF) and polycythaemia vera (PV) patients, while an increase of circulating endothelial cells (CECs) was found in all patients with CMD. Moreover, we found higher serum levels of VEGF with respect to control subjects in every group of patients with CMD, and a not significant reduction of VEGFR2 levels in essential thrombocythaemia (ET) patients. A correlation was also found in PV patients between VEGF levels and erythrocyte number and in PMF subjects with the count of white cells. Our data suggest that some markers of angiogenesis are activated in CMD patients and angiogenesis may have a role in the pathophysiology of chronic myeloproliferative disorders.

Lenalidomide induces complete and partial remissions in patients with relapsed and refractory chronic lymphocytic leukemia

This study investigated the activity of lenalidomide in patients with relapsed/refractory chronic lymphocytic leukemia (CLL). Lenalidomide was given at 10 mg daily with dose escalation up to 25 mg daily. Three patients (7%) achieved a complete response (CR), one a nodular partial remission, and 10 patients a partial remission (PR), for an overall response (OR) rate of 32%. Treatment with lenalidomide was associated with an OR rate of 31% in patients with 11q or 17p deletion, of 24% in patients with unmutated V(H), and of 25% in patients with fludarabine-refractory disease. The most common toxicity was myelosuppression, and the median daily dose of lenalidomide tolerated was 10 mg. Plasma levels of angiogenic factors, inflammatory cytokines, and cytokine receptors were measured at baseline, day 7, and day 28. There was a dramatic increase in median interleukin (IL)-6, IL-10, IL-2, and tumor necrosis factor receptor-1 levels on day 7, whereas no changes were observed in median vascular endothelial growth factor levels (20 patients studied). According to our experience, lenalidomide given as a continuous treatment has antitumor activity in heavily pretreated patients with CLL.

The antileukemia activity of a human anti-CD40 antagonist antibody, HCD122, on human chronic lymphocytic leukemia cells

B-cell chronic lymphocytic leukemia (B-CLL) is a lymphoproliferative disorder characterized by the surface expression of CD20, CD5 antigens, as well as the receptor CD40. Activation of CD40 by its ligand (CD40L) induces proliferation and rescues the cells from spontaneous and chemotherapy-induced apoptosis. CD40 activation also induces secretion of cytokines, such as IL-6, IL-10, TNF-alpha, IL-8, and GM-CSF, which are involved in tumor cell survival, migration, and interaction with cells in the tumor microenvironment. Here we demonstrate that in primary B-CLL tumor cells, the novel antagonist anti-CD40 monoclonal antibody, HCD122, inhibits CD40L-induced activation of signaling pathways, proliferation and survival, and secretion of cytokines. Furthermore, HCD122 is also a potent mediator of antibody-dependent cellular cytotoxicity (ADCC), lysing B-CLL cells more efficiently than rituximab in vitro, despite a significantly higher number of cell surface CD20 binding sites compared with CD40. Unlike rituximab, however, HCD122 (formerly CHIR-12.12) does not internalize upon binding to the cells. Our data suggest that HCD122 may inhibit B-CLL growth by blocking CD40 signaling and by ADCC-mediated cell lysis.

Dysregulated angiogenesis in B-chronic lymphocytic leukemia: morphologic, immunohistochemical, and flow cytometric evidence

BACKGROUND

The extent of enhanced bone marrow angiogenesis in chronic lymphocytic leukemia (CLL) and relationship to proangiogenic factors and prognostic indicators is largely unexplored.

METHODS

To further investigate the role of angiogenesis in CLL by evaluating the topography and extent of angiogenesis in a group of CLL bone marrow biopsies, to study the expression of pro and antiangiogenic vascular factors in CLL cells to more precisely document the cell types producing these factors, and to evaluate the role, if any, of localized hypoxia in upregulation of angiogenesis in CLL We used immunohistochemistry (IHC) (n = 21 pts) with antibodies to CD3 and CD20, proangiogenic (VEGF, HIF-1a) and antiangiogenic (TSP-1) factors, and VEGF receptors -1 and -2 to examine pattern/extent of CLL marrow involvement, microvessel density (MVD), and angiogenic characteristics; flow cytometry (FC) was performed on 21 additional cases for VEGF and TSP-1.

RESULTS

CLL patients had higher MVD (23.8 vs 14.6, p~0.0002) compared to controls (n = 10). MVD was highest at the periphery of focal infiltrates, was not enhanced in proliferation centers, and was increased irrespective of the presence or absence of cytogenetic/immunophenotypic markers of aggressivity. By IHC, CLL cells were VEGF(+), HIF-1a (+), TSP-1(-), VEGFR-1(+), and VEGFR-2(+). By FC, CLL cells were 1.4-2.0-fold brighter for VEGF than T cells and were TSP-1(-).

CONCLUSION

CLL demonstrates enhanced angiogenesis, with increased MVD, upregulated VEGF and downregulated TSP-1. Upregulation of HIF-1a in all CLL cases suggests localized tissue hypoxia as an important stimulant of microvessel proliferation. The presence of VEGF receptors on CLL cells implies an autocrine effect for VEGF. Differences in MVD did not correlate with traditional genetic/immunophenotypic markers of aggressiveness.

Increased microvessel density in involved organs from patients with HTLV-I associated adult T cell leukemia lymphoma

Adult T-cell leukemia-lymphoma (ATLL) is a rapidly progressive lymphoproliferative disorder secondary to infection with the human T cell lymphotropic virus type I (HTLV-I). The role of angiogenesis in the development and prognosis of many hematologic malignancies is established. We have previously shown that ATLL derived cells secrete high levels of vascular endothelial growth factor (VEGF) and basic fibroblast growth factor (b-FGF), induce endothelial tube formation in vitro and establish functional gap junction-mediated communication with endothelial cells. We also demonstrated that plasma from ATLL and tropical spastic paraparesis/HTLV-I associated myelopathy patients exhibit very high levels of VEGF and b-FGF. Recently, we showed that treatment with the combination of zidovudine and interferon alpha reduced both HTLV-I proviral load and importantly VEGF plasma levels suggesting a potential anti-angiogenic effect of this therapy. In this report, we evaluated microvessel density (MVD) in involved organs from 20 patients with ATLL, as compared to normal organs from matched controls. We show evidence of significantly increased MVD in all tested involved organs from ATLL patients, suggesting that angiogenesis plays an important role in the development or organ invasion of ATLL, and could represent a potentially interesting target for anti-angiogenic therapy of ATLL.

Prognostic significance of EBV-LMP1 and VEGF-A expressions in non-Hodgkin's lymphomas

BACKGROUND AND AIM

EBV is an important virus in the pathogenesis of NHL. VEGF-A is the essential factor in tumor angiogenesis. There is evidence of cross talk between angiogenesis and viral carcinogenesis. The viral latent protein LMP1, may play a role by inducing expression of angiogenic factors In this study EBV-LMP1 and VEGF-A expressions have been studied in cases with NHL and prognostic significance of these has been evaluated.

PATIENTS AND METHODS

One hundred seventy-seven cases (60 had low grade lymphoma (LGL), 117 had aggressive lymphoma (AL)) with NHL have been included in this analysis. Immunohistochemistry has been used for the detection of EBV and VEGF-A.

RESULTS

EBV was found in 25 cases (14%); 5 of 60 cases with LGL while 20 of 117 cases with AL had EBV positivity; (OR: 2.3, 95% CI: 0.8-6.3, p=0.113). VEGF-A expression was found in 108 cases (61%); 30 of 60 cases with LGL and 78 of 117 cases with AL showed VEGF-A expression. There was an association between VEGF-A and aggressive histology (OR: 2.0, 95% CI: 1.1-3.8, p=0.031). EBV positivity was associated with VEGF-A expression in diffuse large B cell lymphoma (DLBCL) (0.045). Mean Survival rates were shorter in EBV (+) and/or VEGF-A (+) cases.

COMMENT

Highly significant association between VEGF-A and EBV expression and survival rate, suggests an association between angiogenesis and viral lymphomagenesis. Targeting both the angiogenesis and EBV may be important in the therapy of cases with NHL expressing EBV and/or VEGF-A.

KSHV-transformed primary effusion lymphoma cells induce a VEGF-dependent angiogenesis and establish functional gap junctions with endothelial cells

Kaposi's sarcoma-associated herpesvirus (KSHV) is the causative agent of primary effusion lymphoma (PEL) and of Kaposi's sarcoma. PEL is an aggressive proliferation of B cells with poor prognosis. We evaluated both in vitro and in vivo the potential role of angiogenic factors secreted by PEL cells, that is, their interaction with endothelial cells and their implication in the invasive behavior of tumoral cells. In vitro, PEL-induced angiogenesis is dependent on vascular endothelial growth factor (VEGF) and VEGF receptors. However, although PEL cells produce VEGF and basic fibroblast growth factor (b-FGF) transcripts, they only secrete VEGF in vitro. In vivo, very high levels of both VEGF and b-FGF were found in the ascitic fluid of NOD/SCID mice injected with PEL cells. We then show evidence of cell adhesion and gap junction-mediated heterocellular communication between PEL cells and endothelial cells. Finally, we show that PEL cells extravasate through the endothelial barrier and that the specific tyrosine kinase inhibitor of VEGF receptors, PTK-787/ZK-222584, the anti-VEGF antibody, bevacizumab or the gap junction inhibitor 18-alpha-glycyrrhetinic acid, partially attenuate PEL cell extravasation. Angiogenesis, cell adhesion and communication likely contribute to the development of PEL and represent potential therapeutic targets.

[Molecular and parametric imaging with iron oxides]

Superparamagnetic iron oxide (SPIO) contrast agents, clinically established for high resolution magnetic resonance imaging of reticuloendothelial system containing anatomical structures, can additionally be exploited for the non-invasive characterization and quantification of pathology down to the molecular level. In this context, SPIOs can be applied for non-invasive cell tracking, quantification of tissue perfusion and target specific imaging, as well as for the detection of gene expression. This article provides an overview of new applications for clinically approved iron oxides as well of new, modified SPIO contrast agents for parametric and molecular imaging.

Increased expression of angiopoietin-2 characterizes early B-cell chronic lymphocytic leukemia with poor prognosis

We measured the angiopoietin-2 (Ang-2) expression in early chronic lymphocytic leukemia (CLL) patients, pointing our attention on the association with immunoglobulin (IgV(H)) mutational status, CD38 expression and clinical outcome. Our results indicate that Ang-2 expression is heterogeneous among Binet stage A CLL patients. CLL patients can be divided into two subgroups (Ang-2 positive and Ang-2 negative CLL) with 30% of them displaying Ang-2 RNA levels above the cut off. A shorter progression-free survival was observed in Ang-2 positive CLL subset (p=0.032). Abnormal Ang-2 expression was also associated with unmutated IgV(H) genes (p<0.0001) and increased bone marrow angiogenesis (p=0.028), suggesting a role of Ang-2 in disease-progression of early CLL patients.

Bone biopsy derived marrow stromal elements rescue chronic lymphocytic leukemia B-cells from spontaneous and drug induced cell death and facilitates an "angiogenic switch"

A novel bone biopsy technique was used to generate a robust stromal cell system to study how stroma modulates CLL B-cell apoptosis and how the leukemic cell-stromal interaction influences secretion of vascular factors. Marrow stromal elements (MSE) rescued CLL B-cells from both spontaneous and drug induced apoptosis, partly due to soluble factors. When CLL B-cells were added to the MSE cultures, a dramatic increase in the secretion of basic fibroblast growth factor and decrease in the secretion of thrombospondin was observed. These results indicate the interaction between CLL B-cells and marrow stromal elements regulates angiogenic switching and may be linked to disease progression.

B-cell chronic lymphocytic leukemia: correlation of clinical stages with angiogenic cytokine expression

B-cell chronic lymphocytic leukemia (B-CLL) is characterized by the accumulation of non-cycling B cells in lymphatic and extralymphatic tissues. Earlier studies had validated that angiogenesis was increased in B-CLL. Increased serum concentrations of vascular endothelial growth factor (VEGF) and basic fibroblast growth factor (bFGF) connote a poor prognosis in early-stage B-CLL. Early progression is also related to transforming growth factor-beta (TGF-beta), which inhibits B-cell proliferation and immunoglobulin production. The authors investigated the expression of CD34, VEGF, bFGF, and TGF-beta and their receptors in different stages of B-CLL by analyzing bone marrow samples from 23 patients (11 with Rai stages 0-II; 12 with stages III or IV). TGF-beta2 was expressed more strongly in stages 0 to II than in stages III or IV (P=0.03). There was no significant difference in the intensity of CD34, TGF-beta1, VEGF, and bFGF and their receptors between stages 0 to II and stages III or IV. Staining showed bFGF expression to be stronger than VEGF expression (P=0.001). Results did not confirm an association between the intensity of angiogenesis and B-CLL stage. The expression of TGF-beta2 was stronger in early-stage disease and may help slow disease progression.

Assessment of Bone Marrow Angiogenesis in Patients with Acute Myeloid Leukemia by Using Contrast-enhanced MR Imaging with Clinically Approved Iron Oxides: Initial Experience

PURPOSE

To prospectively assess bone marrow (BM) angiogenesis in patients with acute myeloid leukemia (AML) by using iron oxide-enhanced magnetic resonance (MR) imaging.

MATERIALS AND METHODS

The study was institutional ethics committee approved. Informed signed consent was obtained from each study participant. The requirement for informed consent for use of data from a reference database was waived. Eleven patients (seven women, four men; mean age, 53 years+/-4.40 [standard deviation]) with an initial diagnosis of AML were enrolled in the study and underwent T2*-weighted two-echo echo-planar MR imaging of the pelvis before and after intravenous injection of a clinically approved iron oxide blood-pool contrast agent. Six healthy control subjects (one woman, five men; mean age, 35 years+/-2.31) were examined with the same MR protocol. The iron oxide-induced change in R2* relaxation rate (DeltaR2*) was calculated, and the vascular volume fraction (VVF) of the BM was derived by dividing the DeltaR2* of the BM by the DeltaR2* of the muscle. Parametric DeltaR2* maps were calculated to visualize vessel distribution. Patients underwent BM biopsy for correlative determination of microvessel density (MVD) and vascular endothelial growth factor (VEGF). Differences in DeltaR2*, VVF, VEGF, and MVD were compared by using the Wilcoxon rank sum test.

RESULTS

DeltaR2* maps showed prominent areas of highly vascularized BM in the patients with AML, whereas the control subjects had moderately vascularized BM with homogeneous vessel distribution. Quantitative analysis revealed VVF values to be significantly higher in patients with AML than in control subjects: The mean VVF in the pelvis was 9.18%+/-1.54 for patients versus 3.91%+/-0.61 for control subjects (P=.010). In accordance with MR results, MVD (P=.009) and VEGF expression (P=.017) were significantly elevated in the AML group compared with values in the control group.

CONCLUSION

Iron oxide-enhanced MR imaging enables assessment of BM angiogenesis in patients with AML.

Emerging drugs for chronic lymphocytic leukaemia

Although the philosophy of management of patients with chronic lymphocytic leukaemia (CLL) has been altered with the advent of fludarabine-based therapies, impact on long-term survival is unclear and a significant proportion of patients will develop resistance to fludarabine. Similar to other haematological malignancies, a potential for 'cure' is likely to be achieved only if 'high-quality' complete remissions (CRs) are achieved. Treatment options for patients who develop resistance to fludarabine continue to be limited, with only a proportion obtaining a response (usually not CRs) with salvage therapies. This review summarises novel therapies that are being evaluated in patients with CLL, specifically those targeting the antiapoptotic Bcl-2 family of proteins and receptors (e.g., CD40, CD80, HLA-DR) involved in mediating survival signals from the microenvironment.

Role of angiogenesis in chronic lymphocytic leukemia

Angiogenesis is a physiologic process of new blood vessels formation mediated by various cytokines called angiogenic and angiostatic factors. Although its potential pathophysiologic role in solid tumors has been extensively studied for more than 3 decades, enhancement of angiogenesis in chronic lymphocytic leukemia (CLL) and other malignant hematological disorders has been recognized more recently. An increased level of angiogenesis has been documented by various experimental methods both in bone marrow and lymph nodes of patients with CLL. Although the role of angiogenesis in the pathophysiology of this disease remains to be fully elucidated, experimental data suggest that several angiogenic factors play a role in the disease progression. Biologic markers of angiogenesis were also shown to be of prognostic relevance in CLL. The current findings provide the rationale for investigating antiangiogenic agents in CLL. In the current review angiogenesis in CLL is discussed and its potential diagnostic and therapeutic applications.

Malignant hematopoietic cells induce an increased expression of VEGFR-1 and VEGFR-3 on bone marrow endothelial cells via AKT and mTOR signalling pathways

Angiogenesis plays a significant role in a variety of malignant hematologic diseases, and it is recognized that it has prognostic value. However, the cellular mechanisms by which malignant hematologic cells induce angiogenesis are not well understood. In order to investigate the role of cells from B-cell chronic lymphocytic leukemia (B-CLL) and multiple myeloma (MM) in angiogenesis on human bone marrow endothelial cells (HBMEC), we analyzed the impact of factors secreted by B-CLL cells and by MM cells on HBMEC capillary tube formation on matrigel. It was found that, in addition to the secretion of angiogenic factors VEGF and b-FGF by B-CLL and MM cells, MM cells (but not B-CLL cells) induced a dramatic increase in expression of VEGFR-1 and VEGFR-3 on human bone marrow endothelial cells (HBMEC). It would seem that this increase in VEGFR-3 occurred via the ERK and mTOR pathways, since their respective inhibitors U0126, LY294002 or rapamycin were responsible for a decrease of VEGFR-3. In response to MM cells-increased VEGF receptors on HBMEC, endothelial cell migration was enhanced in a wound artificially produced in a semi-confluent HBMEC culture, a phenomenon which was also down-regulated by the same inhibitors that reversed the increase in VEGF receptors. The present study suggests that, in addition to the classic angiogenic pathway, another mechanism related to an increased expression of VEGFRs on HBMEC might exist in malignant hematopoietic angiogenesis.

Circulating sCD138 and some angiogenesis-involved cytokines help to anticipate the disease progression of early-stage B-cell chronic lymphocytic leukemia

Syndecan-1 (CD138) is a transmembrane heparin sulfate proteoglycan expressed on distinct stages of differentiation of B-lymphoid cells. Its prognostic value in B-cell chronic lymphocytic leukemia (B-CLL) has not been evaluated so far. The serum concentration of sCD138 and some angiogenesis-involved cytokines: vascular endothelial growth factor (VEGF), basis fibroblast growth factor (bFGF), and endostatin were studied in 52 previously untreated patients with B-CLL. We found that bFGF and sCD138 levels were significantly higher in B-CLL patients than in controls. In patients with sCD138 level or endostatin level below the median value the lymphocyte count was higher than in patients with serum level of those cytokines above the median value. In patients with progressive disease bFGF level was significantly higher and sCD138 level significantly lower than in patients with stable one. Moreover, high sCD138 level was associated with longer lymphocyte doubling-free survival, and, on the limit of statistical significance, a high endostatin level was associated with shorter progression-free survival. We conclude that serum sCD138 level is increased in early stage B-CLL patients and may have a positive prognostic value as to the dynamics of the disease.

MMP-9 in B-cell chronic lymphocytic leukemia is up-regulated by alpha4beta1 integrin or CXCR4 engagement via distinct signaling pathways, localizes to podosomes, and is involved in cell invasion and migration

B-cell chronic lymphocytic leukemia (B-CLL) progression is determined by malignant cell extravasation and lymphoid tissue infiltration. We have studied the role and regulation of matrix metalloproteinase-9 (MMP-9) in B-CLL cell migration and invasion. Adhesion of B-CLL cells to the fibronectin fragment FN-H89, VCAM-1, or TNF-alpha-activated human umbilical vein endothelial cells (HUVECs) up-regulated MMP-9 production, measured by gelatin zymography. This effect was mediated by alpha4beta1 integrin and required PI3-K/Akt signaling. The chemokine CXCL12 also up-regulated MMP-9, independently of alpha4beta1 and involving ERK1/2 but not Akt activity. Accordingly, alpha4beta1 engagement activated the PI3-K/Akt/NF-kappaB pathway, while CXCL12/CXCR4 interaction activated ERK1/2/c-Fos signaling. Anti-MMP-9 antibodies, the MMP-9 inhibitor TIMP-1, or transfection with 3 different MMP-9 siRNAs significantly blocked migration through Matrigel or HUVECs. Cell-associated MMP-9 was mainly at the membrane and contained the proactive and mature forms. Moreover, B-CLL cells formed podosomes upon adhesion to FN-H89, VCAM-1, or fibronectin; MMP-9 localized to podosomes in a PI3-K-dependent manner and degraded a fibronectin/gelatin matrix. Our results are the first to show that MMP-9 is physiologically regulated by alpha4beta1 integrin and CXCL12 and plays a key role in cell invasion and transendothelial migration, thus contributing to B-CLL progression. MMP-9 could therefore constitute a target for treatment of this malignancy.

Angiogenesis in multiple myeloma

Multiple myeloma (MM) was the first haematological malignancy in which a prognostic relevance of bone marrow microvessel density (MVD) was shown. Myeloma-induced angiogenesis involves either the direct production of angiogenic molecules by myeloma cells or their induction in bone marrow stromal cells or endothelial cells (EC). Recent data demonstrate an increased angiogenic potential and a paracrine stimulatory effect of bone marrow EC on plasma cells (PC) in MM. Soluble angiogenic factors are elevated in bone marrow (BM) and in peripheral blood samples from myeloma patients. Furthermore, correlation with disease stage and prognosis was shown for serum levels of the angiogenic factors basic fibroblast growth factor (bFGF), hepatocyte growth factor (HGF) and vascular endothelial growth factor (VEGF). In this review we summarize recent data which give strong evidence for an increased angiogenic activity in bone marrow microenvironment and support the hypothesis that angiogenesis is not only an epiphenomenon of tumour growth but may also promote PC growth in MM.

Leukemia-stimulated bone marrow endothelium promotes leukemia cell survival

Extensive endothelial cell proliferation and marked neovascularization are the most pronounced microenvironmental changes consistently observed in the bone marrow (BM) of patients with acute lymphoblastic leukemia (ALL). It is not known whether ALL cells induce this phenotype and whether they receive critical signals from the tumor-associated BM endothelium. Here, we show that leukemia cells actively stimulate BM endothelium, promote de novo angiogenesis, and induce neovascularization in the leukemic BM. Soluble factors, present in the leukemic BM microenvironment, promote the proliferation, migration, and morphogenesis of BM endothelial cells, which are critical processes in tumor angiogenesis. We also show in vitro that leukemia cells display directional motion towards assembled BM endothelium and following adherence exhibit cell polarization, pseudopodia, and ultrastructural features that suggest the existence of leukemia-endothelium cross-talk. Finally, we show that BM endothelium promotes leukemia cell survival through a mechanism mediated through the anti-apoptotic molecule bcl-2. These studies indicate that ALL cells actively recruit BM endothelium and mediate the leukemia-associated neovascularization observed in ALL. Therefore, disruption of interactions between leukemia cells and BM endothelium may constitute a valid therapeutic strategy.

VEGFR-1 (FLT-1) activation modulates acute lymphoblastic leukemia localization and survival within the bone marrow, determining the onset of extramedullary disease

The presence of persistent circulating leukemia cells, or engrafted into extramedullary tissues, is a bad prognostic factor for patients with acute leukemia. However, little is known about the mechanisms that regulate the exit of leukemia cells from the bone marrow (BM) microenvironment. We reveal that vascular endothelial growth factor receptor 1 (FLT-1) modulates acute leukemia distribution within the BM, along VEGF and PlGF gradients, regulating leukemia survival and exit into the peripheral circulation. FLT-1 activation on acute lymphoblastic leukemia (ALL) cells results in cell migration and proliferation in vitro, whereas in vivo FLT-1-overexpressing cells accumulate in the BM epiphysis of nonobese diabetic-severe combined immunodeficient (NOD-SCID) recipients and are detected in circulation 2 weeks after inoculation. In turn, FLT-1 neutralization affects leukemia localization (now in the BM diaphysis), increases leukemia apoptosis, and impedes the exit of ALL cells, prolonging the survival of inoculated mice. We demonstrate further that FLT-1-induced cell migration involves actin polymerization and lipid raft formation. Taken together, we show that FLT-1 regulates the BM localization of ALL cells, determining their survival and exit into the circulation and ultimately the survival of inoculated recipients. FLT-1 targeting on subsets of acute leukemias may delay the onset of extramedullary disease, which may be advantageous in combinatorial therapeutic settings.

Hyperforin inhibits MMP-9 secretion by B-CLL cells and microtubule formation by endothelial cells

We previously reported that hyperforin (HF), a natural phloroglucinol purified from Saint John's wort, can induce the apoptosis of leukemic cells from patients with B-cell lymphocytic leukemia (B-CLL) ex vivo. We show here that treatment of cultured B-CLL patients' cells with HF results in a marked inhibition of their capacity to secrete matrix metalloproteinase-9, an essential component in neo-angiogenesis through degradation of the extracellular matrix process. The phloroglucinol acts by decreasing the production of the latent 92 kDa pro-enzyme. The inhibitory effect of HF is associated with a decrease in VEGF release by the leukemic cells. Moreover, HF is found to prevent the formation of microtubules by human bone marrow endothelial cells cultured on Matrigel, evidencing its capacity to inhibit vessel formation. Our results show the antiangiogenesis activity of HF and strengthen its potential interest in the therapy of B-CLL.

Expression and cellular localization of vascular endothelial growth factor A and its receptors in acute and chronic leukemias: An immunohistochemical study

We aimed to study the expression of phosphorylated vascular endothelial growth factor receptor 2 (pVEGFR-2), a membrane-bound tyrosine kinase receptor to vascular endothelial growth factor, in 76 cases of leukemia and nonneoplastic myeloproliferative disease and in 8 reactive bone marrows. The microvessel density (MVD) and the expression of both pVEGFR-2 and its ligand, VEGFA, were evaluated in these cases. We used archival cases and immunohistochemistry with a monoclonal antibody generated by us to the autophosphorylation sites in the cytoplasmic tail of VEGFR-2 and von Willebrand factor antibody to evaluate MVD. Our results demonstrate increased expression of this phosphorylated receptor in the neoplastic cells in acute myeloid and lymphoblastic leukemias. This correlated with increased MVD and VEGFA expression by the neoplastic cells. Interestingly, there was nuclear relocation of this receptor in these diseases. This raises the possibility that pVEGFR-2 may be involved in the transcriptional regulation of these leukemias. Small molecule inhibitors to this receptor may therefore be a useful adjunct in the therapy for these diseases.

Angiogenesis in lymphoproliferative disorders: a therapeutic target?

PURPOSE OF REVIEW

Several recent studies have focused on the role of angiogenesis in hematologic malignancies. This review specifically discusses angiogenesis in lymphoproliferative disorders, with a special emphasis on the most recent publications. The novel therapeutic strategies arising from advances in this field are reviewed, and the potential pitfalls of these therapies are also discussed.

RECENT FINDINGS

Recent publications confirm that angiogenesis and angiogenic factors are increased in lymphoproliferative disorders. In addition, several studies have demonstrated that angiogenesis is directly involved in the pathogenesis of these disorders.

SUMMARY

Knowledge of angiogenesis in lymphoproliferative disorders has increased substantially in the past few years. Angiogenic factors such as vascular endothelial growth factor have been shown to be important in the progression or maintenance of lymphoproliferative disorders. Targeting of these factors is therefore a promising new therapeutic approach. Hematopoietic angiogenesis is a nascent field, however, and its concepts are still evolving. A systematic approach to understanding and characterizing the angiogenic phenotype is required for the design of efficacious antiangiogenic therapeutic regimens.

Angiogenesis in Hodgkin's lymphoma: a morphometric approach in 286 patients with prognostic implications

The significance of angiogenesis in Hodgkin's lymphoma (HL) is not well defined. The aim of this study was to evaluate various morphometric characteristics of microvessels in lymph node sections of 286 patients with HL at diagnosis and investigate their relationship with clinicopathologic parameters and prognosis. Microvessel density (MVD), total vascular area (TVA) and several size- and shape-related microvascular parameters were quantitated--after anti-CD34 immunohistochemical staining--in the region of most intense vascularization, using image analysis. An increase in microvessel caliber parameters (area, perimeter, major and minor axis length) and a decrease in MVD were noted with increasing stage. An inverse relationship was recorded between MVD and the number of involved sites (NIS) and LDH. In univariate analysis, overall disease-specific survival was adversely affected by MVD and TVA, whereas inferior failure-free survival (FFS) was associated with the presence of more flattened vessel sections. Multivariate analysis disclosed that the extent of angiogenesis (MVD/TVA), age and the NIS independently affected overall survival. Accordingly, FFS was independently linked to the shape of microvessels and albumin levels or the NIS. In conclusion, our data support the view that angiogenesis in HL provides independent prognostic information, requiring the concomitant evaluation of quantitative and qualitative aspects of microvascular network.

Mammalian target of rapamycin (mTOR) inhibition in chronic lymphocytic B-cell leukemia: a new therapeutic option

Chronic lymphocytic B-cell leukemia (B-CLL) is an incurable disease characterized by the accumulation of monoclonal mature B cells, although disease progression relies upon cycling B-CLL cells in proliferation centers in central lymph organs. Rapamycin and its analogs are immunosuppressant drugs that exert their activity by specific inhibition of the mammalian target of rapamycin (mTOR). mTOR inhibition induces cell cycle arrest not only in normal lymphocytes but also in malignant cells. Therefore, rapamycins have recently entered the field of cancer treatment. In the present review we discuss how progression through the cell cycle is regulated in B-CLL cells and how rapamycin and its analogs can be used as target therapies against proliferating B-CLL cells. We also focus on additional effects of rapamycin, such as targeting the interaction between malignant B cells and the microenvironment.

Autocrine VEGF mediates the antiapoptotic effect of CD154 on CLL cells

CD154 is an important regulator of chronic lymphocytic leukaemia (CLL)-cell survival. In CLL, high serum levels of VEGF are a feature of advanced disease, and we and others have previously shown that CLL cells produce and secrete this growth factor. Since CD154 stimulates VEGF production in other cell types, and VEGF is known to promote cell survival, we examined whether the cytoprotection of CLL cells by CD154 involves VEGF. We report for the first time that treatment of CLL cells with CD154 results in increased VEGF production and demonstrate involvement of NF-kappaB in this process. Moreover, we show that CD154-induced CLL-cell survival is reduced by anti-VEGF-neutralising antibody and by inhibiting VEGF receptor (VEGFR) signalling with SU5416. However, addition of exogenous VEGF alone or blocking secreted autocrine VEGF had little or no effect on CLL-cell survival. We therefore conclude that CLL-cell cytoprotection in the presence of CD154 requires combined signalling by both CD40 and VEGFR. This combined signalling and resulting cytoprotection were shown to involve NF-kappaB activation and increased survivin production. In conclusion, our findings identify autocrine VEGF as an important mediator of the antiapoptotic effect of CD40 ligation, and thus provide new insights into CLL-cell rescue by CD154 in lymphoreticular tissues.

The expression and cellular localization of phosphorylated VEGFR2 in lymphoma and non-neoplastic lymphadenopathy: an immunohistochemical study

AIMS

To study the expression of phosphorylated vascular endothelial growth factor receptor 2 (VEGFR2), a membrane-bound tyrosine kinase receptor to vascular endothelial growth factor, in lymphoma and non-neoplastic lymphadenopathy.

METHODS AND RESULTS

Archival cases (89 cases of lymphoma and 17 cases of non-neoplastic lymphadenopathy) were studied immunohistochemically with three monoclonal antibodies to the different autophosphorylation sites in the cytoplasmic tail of the receptor. There was increased expression of this receptor in lymphoma and particularly in all cases of peripheral T-cell lymphoma. In this category, there was nuclear re-location of this receptor.

CONCLUSIONS

This very interesting finding raises the possibility that VEGFR2 may be involved in the transcriptional regulation of this disease. Small molecule inhibitors to this receptor may therefore be a useful adjunct in the therapy of this disease.