Expression of angiogenic factors in chronic myeloid leukaemia: role of the bcr/abl oncogene, biochemical mechanisms, and potential clinical implications

Ophthalmologic manifestations as the initial presentation of chronic myeloid leukemia: A review

The presentation of chronic myeloid leukemia (CML) can be variable and related to the phase of the disease. It can manifest a wide range of symptoms and signs; ocular involvement is reported in patients with leukemia at the time of diagnosis. We describe ophthalmic manifestations as an initial presentation in patients with CML. We identified 38 publications between 1971 and 2020 describing ocular manifestations in CML. Ophthalmic problems occur either from direct or indirect infiltration of neoplastic cells or from secondary causes. Although nearly all ocular structures may be affected, leukemic retinopathy is the most frequent clinical manifestation. Others include iris infiltration, anterior uveitis, hypopyon, exudative/serous retinal detachment, and optic nerve infiltration.

[The basophil: From control of immunity to control of leukemias]

The basophils, first described by Paul Ehlrich in 1879, are rare circulating cells, representing approximately 0.01 to 0.3% of the blood leukocytes. Until recently, these cells have been neglected because of their minority status among immune cells and because they show some similarities to mast cells residing in tissues. However, basophils and mast cells are now recognized as distinct cell lines and it appears that basophils have important and non-redundant functions, distinct from those of mast cells. On the one hand, basophils have beneficial contribution to protective immunity, in particular against parasitic infections. On the other hand, basophils are involved in the development of various benign and malignant pathologies, ranging from allergy to certain leukemias. Basophils interact with other immune cells or neoplastic cells through direct contacts or soluble mediators, such as cytokines and proteases, thus contributing to the regulation of the immune system but also to allergic responses, and probably to the process of neoplastic transformation. In this review, we will develop recent knowledge on the involvement of basophils in the modulation of innate and adaptive immunity. We will then describe the benign or malignant circumstances in which an elevation of circulating basophils can be observed. Finally, we will discuss the role played by these cells in the pathophysiology of certain leukemias, particularly during chronic myeloid leukemia.

Chronic myeloid leukaemia accelerates proliferative retinopathy in patients with co-existent diabetes: A risk factor not to be ignored

OBJECTIVE

To describe the retinal imaging characteristics, retinopathy management strategies and visual outcomes in cases of diabetes with chronic myeloid leukaemia.

DESIGN

Retrospective observational study.

PARTICIPANTS

Patients with diabetes and chronic myeloid leukaemia managed at our tertiary eye care centre from January 2015 to December 2017.

METHODS

Detailed ophthalmic and systemic evaluation, treatment and follow-up records were reviewed. The main measures studied were visual acuity, intra-ocular pressure, retinopathy severity, and surgical indications and techniques.

RESULTS

Of the six patients studied, three had diabetes and chronic myeloid leukaemia at presentation, while in three cases chronic myeloid leukaemia was diagnosed following evaluation for proliferative retinopathy. The visual acuity ranged from 20/20 to perception of light. All eyes had marked proliferative retinopathy out of proportion to the exudation. None of the eyes had significant macular oedema. Pan-retinal photocoagulation (10/12, 83.33%), intravitreal anti-vascular endothelial growth factor injection (8/12, 66.67%), vitrectomy (2/12, 16.67%), cataract surgery (2/12, 16.67%) and trabeculectomy followed by cryoablation (2/12, 16.67%) was performed for management of the ocular disease as indicated. Median follow-up was 16.5 months (range: 6-24 months). Final visual acuity ranged from PL to 20/20 with acuity ⩾ 20/100 in eight eyes. Four eyes had advanced optic neuropathy from neovascular glaucoma.

CONCLUSION

Accelerated proliferative retinopathy can be seen in cases of diabetes with chronic myeloid leukaemia at the very initial ophthalmic evaluation. Thus, there is a need to alter screening guidelines for retinopathy in cases of diabetes with chronic myeloid leukaemia. Early detection and aggressive management may help preserve visual acuity in such cases.

Anti-leukemic and anti-angiogenic effects of d-Limonene on K562-implanted C57BL/6 mice and the chick chorioallantoic membrane model

BACKGROUND

d-Limonene, a monoterpene from citrus fruit has been found to have chemopreventive and chemotherapeutic activities in various types of cancers. In this study, we evaluated the in vivo effect of d-Limonene on a K562-induced model of chronic myeloid leukemia (CML) in C57BL/6 mice.

METHOD

The tail vein injection model of K562 cells in immunocompromised C57BL/6 mice was developed and evaluated for characteristics of the disease. The mice were treated with d-Limonene and evaluated for haematological parameters. We also evaluated the effect of d-Limonene on angiogenesis using the chick chorioallantoic membrane (CAM) assay.

RESULTS

In a complete blood count, a significant dose-dependent reduction in white blood cell, neutrophil and lymphocyte counts, but an elevation in red blood cell count and haemoglobin content was observed with d-Limonene treatment compared to the disease control or untreated group. In the CAM assay, d-Limonene produced a significant dose-dependent reduction in number of blood vessels in treatment groups compared to the vehicle-treated group.

CONCLUSION

These studies suggest promising anti-leukemic and anti-angiogenic effects of d-Limonene in the treatment of CML.

The underestimated role of basophils in Ph+ chronic myeloid leukaemia

Chronic myeloid leukaemia (CML) is a hematopoietic neoplasm defined by the chromosome translocation t(9;22) and the related oncogene, BCR-ABL1. In most patients, leukaemic cells can be kept under control using BCR-ABL1-targeting drugs. However, many patients relapse which remains a clinical challenge. In particular, patients with advanced (accelerated or blast phase) CML have a poor prognosis. So far, little is known about molecular and cellular interactions and features that contribute to disease progression and drug resistance in CML. One key prognostic factor at diagnosis is marked basophilia. However, although basophils are well-known multifunctional effector cells, their impact in CML remains uncertain. In this article, we discuss the potential role of basophils as active contributors to disease evolution and progression in CML. In particular, basophils serve as a unique source of inflammatory, angiogenic and fibrogenic molecules, such as vascular endothelial growth factor or hepatocyte growth factor. In addition, basophils provide vasoactive substances, like histamine as well as the cytokine-degrading enzyme dipeptidyl-peptidase IV which may promote stem cell mobilization and the extramedullary spread of stem and progenitor cells. Finally, basophils may produce autocrine growth factors for myeloid cells. Understanding the role of basophils in CML evolution and progression may support the development of more effective treatment concepts.

Association of Vascular Endothelial Growth Factor A (VEGFA) and its Receptor (VEGFR2) Gene Polymorphisms with Risk of Chronic Myeloid Leukemia and Influence on Clinical Outcome

INTRODUCTION

Vascular endothelial growth factor A (VEGFA) and its kinase insert domain receptor (VEGFR2/KDR) were reported to be upregulated in chronic myeloid leukemia (CML); however, the influence of polymorphisms in VEGFA and VEGFR2 in CML pathogenesis and therapeutic response, have not yet been elucidated.

METHODS

We aimed to analyze these polymorphisms in 212 CML patients and 212 healthy controls by the polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) approach.

RESULTS

The VEGFA+936C>T polymorphism did not differ significantly between the CML patients and controls. The frequency of CT genotype was higher in CML patients than in controls (25 vs. 18%), higher in males than in females (29 vs. 18%), was more prevalent in the patients with splenomegaly (p = 0.03), and was negatively associated with lactate dehydrogenase (LDH) levels (p = 0.01). The frequency of VEGFR2 mutant T-allele was higher in CML patients than controls (p < 0.0001). In the dominant model, patients having the combined AT and TT genotypes were associated with 2.6-fold higher risk of CML [odds ratio (OR) = 2.6, 95% confidence interval (CI) = 1.71–3.97, p < 0.0001]. VEGFR2 AT genotype was significantly associated with high blast count (p = 0.006), minor hematological response (p = 0.03) and poor cytogenetic response (p = 0.003), indicating its role in therapeutic resistance. In contrast, poor molecular response was observed in patients with TT genotype (p = 0.02). VEGFA+936C>T polymorphism was found to have synergistic interaction with VEGFR2+1416A>T in inflating the risk for CML further (P(interaction) = 0.0002).

CONCLUSION

Our results indicate that VEGFR2+1416A>T polymorphism may be a useful marker in assessing the disease progression in CML patients. In addition, VEGFA+936C>T was observed to have additive effect in inflating the risk further.

A case of leukemic retinopathy mimicking common ischemic retinopathies

Reported case of leukemic retinopathy mimicking common ischemic retinopathies in a young adult where ophthalmic visit was the first step to the diagnosis of chronic myeloid leukemia. It highlights the importance of routine eye exams and that clinicians should suspect leukemia in an otherwise healthy patient presenting with ischemic retinopathy.

Leucapheresis for management of retinopathy in chronic myeloid leukaemia

Chronic myeloid leukaemia is a myeloproliferative neoplasm characterised by granulocytic hyperplasia in the bone marrow and the presence of a specific cytogenetic abnormality known as Philadelphia chromosome with fusion of breakpoint cluster region (BCR) and ableson (ABL) genes. Retinopathy is a rare sight-threatening complication of chronic myeloid leukaemia, which occurs due to leucostasis in retinal blood vessels. We report a case of a patient who presented with visual impairment due to leucostasis, who was successfully managed by leucapheresis along with BCR-ABL tyrosine kinase inhibitor.

Cytokine Regulation of Microenvironmental Cells in Myeloproliferative Neoplasms

The term myeloproliferative neoplasms (MPN) refers to a heterogeneous group of diseases including not only polycythemia vera (PV), essential thrombocythemia (ET), and primary myelofibrosis (PMF), but also chronic myeloid leukemia (CML), and systemic mastocytosis (SM). Despite the clinical and biological differences between these diseases, common pathophysiological mechanisms have been identified in MPN. First, aberrant tyrosine kinase signaling due to somatic mutations in certain driver genes is common to these MPN. Second, alterations of the bone marrow microenvironment are found in all MPN types and have been implicated in the pathogenesis of the diseases. Finally, elevated levels of proinflammatory and microenvironment-regulating cytokines are commonly found in all MPN-variants. In this paper, we review the effects of MPN-related oncogenes on cytokine expression and release and describe common as well as distinct pathogenetic mechanisms underlying microenvironmental changes in various MPN. Furthermore, targeting of the microenvironment in MPN is discussed. Such novel therapies may enhance the efficacy and may overcome resistance to established tyrosine kinase inhibitor treatment in these patients. Nevertheless, additional basic studies on the complex interplay of neoplastic and stromal cells are required in order to optimize targeting strategies and to translate these concepts into clinical application.

Chronic myeloid leukemia diagnosed in a patient with uncontrolled proliferative diabetic retinopathy

PURPOSE

To report a case of uncontrolled proliferative diabetic retinopathy as an initial manifestation of chronic myeloid leukemia.

METHODS

Case report.

PATIENTS

A 55-year-old man with moderate nonproliferative diabetic retinopathy who rapidly developed proliferative retinopathy and bilateral neovascular glaucoma despite good glycemic control.

CONCLUSION

Other pathologies should be excluded in diabetic patients with a rapid and severe progression in their retinopathy despite adequate metabolic control. These patients should be treated promptly and aggressively until systemic disease is stable.

Exosome-mediated crosstalk between chronic myelogenous leukemia cells and human bone marrow stromal cells triggers an interleukin 8-dependent survival of leukemia cells

Chronic myelogenous leukemia (CML) is a myeloproliferative disorder characterized by the Bcr-Abl oncoprotein with constitutive tyrosine kinase activity. Exosomes are nanovesicles released by cancer cells that are involved in cell-to-cell communication thus potentially affecting cancer progression. It is well known that bone marrow stromal microenvironment contributes to disease progression through the establishment of a bi-directional crosstalk with cancer cells. Our hypothesis is that exosomes could have a functional role in this crosstalk. Interleukin-8 (IL 8) is a proinflammatory chemokine that activates multiple signalling pathways downstream of two receptors (CXCR1 and CXCR2). We demonstrated that exosomes released from CML cells stimulate bone marrow stromal cells to produce IL 8 that, in turn, is able to modulate both in vitro and in vivo the leukemia cell malignant phenotype.

Bilateral proliferative retinopathy as the initial presentation of chronic myeloid leukemia

The authors report a rare case of a 48-year-old male with chronic myeloid leukemia (CML) who initially presented with a bilateral proliferative retinopathy. The patient complained of recent visual loss and floaters in both eyes (BE). Ophthalmologic evaluation revealed a best corrected visual acuity (BCVA) of 20/50 in the right eye and 20/200 in the left eye (LE). Fundoscopy showed the presence of bilateral peripheral capillary dropout with multiple retinal sea fan neovascularisations, which were confirmed on fluorescein angiography. Full blood count revealed hyperleukocytosis, thrombocytosis, anemia, and hyperuricemia. Bone marrow aspiration and biopsy showed the reciprocal chromosomal translocation t (9;22), diagnostic of CML. The patient was started on hydroxyurea, allopurinol and imatinib mesylate. He received bilateral panretinal laser photocoagulation and a vitrectomy was performed in the LE. The patient has been in complete hematologic, cytogenetic, and major molecular remission while on imatinib and his BCVA is 20/25 in BE.

Serum levels of angiopoietin-2 are associated with the growth of multiple myeloma

Angiopoietins and their receptor, Tie-2, have crucial role in angiogenesis. We measured serum levels of angiopoietin-2 (Ang-2), soluble Tie-2, and factors of burden and prognosis in myeloma (LDH, CRP, beta-2 microglobulin, and interleukin-6) in 55 newly diagnosed patients, with 30 of them in plateau phase, in order to note correlations among them. Levels of Ang-2 were higher in patients in advanced stage of disease, decreased in plateau phase, and correlated with all other factors. Circulating Ang-2 in myeloma patients significantly correlated to factors of disease burden and prognosis, and therefore measuring its levels may be important for the valuation of the disease.

Identification of basophils as a major source of hepatocyte growth factor in chronic myeloid leukemia: a novel mechanism of BCR-ABL1-independent disease progression

Chronic myeloid leukemia (CML) is a hematopoietic neoplasm characterized by the Philadelphia chromosome and the related BCR-ABL1 oncoprotein. Acceleration of CML is usually accompanied by basophilia. Several proangiogenic molecules have been implicated in disease acceleration, including the hepatocyte growth factor (HGF). However, little is known so far about the cellular distribution and function of HGF in CML. We here report that HGF is expressed abundantly in purified CML basophils and in the basophil-committed CML line KU812, whereas all other cell types examined expressed only trace amounts of HGF or no HGF. Interleukin 3, a major regulator of human basophils, was found to promote HGF expression in CML basophils. By contrast, BCR-ABL1 failed to induce HGF synthesis in CML cells, and imatinib failed to inhibit expression of HGF in these cells. Recombinant HGF as well as basophil-derived HGF induced endothelial cell migration in a scratch wound assay, and these effects of HGF were reverted by an anti-HGF antibody as well as by pharmacologic c-Met inhibitors. In addition, anti-HGF and c-Met inhibitors were found to suppress the spontaneous growth of KU812 cells, suggesting autocrine growth regulation. Together, HGF is a BCR-ABL1-independent angiogenic and autocrine growth regulator in CML. Basophils are a unique source of HGF in these patients and may play a more active role in disease-associated angiogenesis and disease progression than has so far been assumed. Our data also suggest that HGF and c-Met are potential therapeutic targets in CML.

Downregulation of miR-31, miR-155, and miR-564 in chronic myeloid leukemia cells

Background/Aims

MicroRNAs (miRNAs) are short non-coding regulatory RNAs that control gene expression and play an important role in cancer development and progression. However, little is known about the role of miRNAs in chronic myeloid leukemia (CML). Our objective is to decipher a miRNA expression signature associated with CML and to determine potential target genes and signaling pathways affected by these signature miRNAs.

Results

Using miRNA microarrays and miRNA real-time PCR we characterized the miRNAs expression profile of CML cell lines and patients in reference to non-CML cell lines and healthy blood. Of all miRNAs tested, miR-31, miR-155, and miR-564 were down-regulated in CML cells. Down-regulation of these miRNAs was dependent on BCR-ABL activity. We next analyzed predicted targets and affected pathways of the deregulated miRNAs. As expected, in K562 cells, the expression of several of these targets was inverted to that of the miRNA putatively regulating them. Reassuringly, the analysis identified CML as the main disease associated with these miRNAs. MAPK, ErbB, mammalian target of rapamycin (mTOR) and vascular endothelial growth factor (VEGF) were the main molecular pathways related with these expression patterns. Utilizing Venn diagrams we found appreciable overlap between the CML-related miRNAs and the signaling pathways-related miRNAs.

Conclusions

The miRNAs identified in this study might offer a pivotal role in CML. Nevertheless, while these data point to a central disease, the precise molecular pathway/s targeted by these miRNAs is variable implying a high level of complexity of miRNA target selection and regulation. These deregulated miRNAs highlight new candidate gene targets allowing for a better understanding of the molecular mechanism underlying the development of CML, and propose possible new avenues for therapeutic treatment.

Role of exosomes released by chronic myelogenous leukemia cells in angiogenesis

Our study is designed to assess if exosomes released from chronic myelogenous leukemia (CML) cells may modulate angiogenesis. We have isolated and characterized the exosomes generated from LAMA84 CML cells and demonstrated that addition of exosomes to human vascular endothelial cells (HUVEC) induces an increase of both ICAM-1 and VCAM-1 cell adhesion molecules and interleukin-8 expression. The stimulation of cell-cell adhesion molecules was paralleled by a dose-dependent increase of adhesion of CML cells to a HUVEC monolayer. We further showed that the treatment with exosomes from CML cells caused an increase in endothelial cell motility accompanied by a loss of VE-cadherin and β-catenin from the endothelial cell surface. Functional characterization of exosomes isolated from CML patients confirmed the data obtained with exosomes derived from CML cell line. CML exosomes caused reorganization into tubes of HUVEC cells cultured on Matrigel. When added to Matrigel plugs in vivo, exosomes induced ingrowth of murine endothelial cells and vascularization of the Matrigel plugs. Our results suggest for the first time that exosomes released from CML cells directly affect endothelial cells modulating the process of neovascularization.

Elevated plasma levels of vascular endothelial growth factor is associated with marked splenomegaly in chronic myeloid leukemia

Recent investigations support the idea that angiogenesis is involved in the pathophysiology of hematologic malignancies, including chronic myeloid leukemia (CML). The aim of the present study was to evaluate plasma levels of VEGF and bFGF in a cohort of 51 chronic-phase CML patients at the time of diagnosis, as well as to investigate the effect of imatinib therapy on VEGF amounts in CML patients. Plasma VEGF levels were significantly higher in patients studied as compared with the 20 healthy subjects (p<0.001), the median plasma VEGF level detected in patients analysed and healthy controls was 433.4 pg mL(-1) (range 65.2-2,452.7 pg mL(-1)) and 81.6 pg mL(-1) (range 44.2-338.7 pg mL(-1)), respectively. On the other hand, no difference in bFGF plasma levels could be found between chronic-phase CML patients and the control group. There were significant associations between plasma VEGF levels and some characteristics of patients evaluated, with trends for higher VEGF values in patients with enlarged spleens (p = 0.02) and those with higher platelet count (p<0.001). Of the patients, 11 received imatinib treatment. The initial VEGF levels markedly decreased after 6 months of imatinib therapy in each patient (p<0.001). These data support the important pathophysiological role of VEGF in CML. Further studies aiming to explore the detailed angiogenic profile of CML may help in developing new therapeutic strategies for this myeloproliferative disorder.

Immunohistochemical detection of vascular endothelial growth factor (VEGF) in the bone marrow in patients with myelodysplastic syndromes: correlation between VEGF expression and the FAB category

Recent data suggest that vascular endothelial growth factor (VEGF) is produced in neoplastic cells in various myeloid neoplasms and plays a key role as an autocrine regulator and mediator of angiogenesis. We examined the expression of VEGF in paraffin-embedded bone marrow sections obtained from normal donors (n = 5) and 46 patients with myelodysplastic syndromes [MDS, French-American-British (FAB)-type refractory anemia (RA), n = 10; refractory anemia with ringed sideroblasts (RARS), n = 10; refractory anemia with excess blasts (RAEB), n = 10; RAEB in transformation (RAEB-T), n = 8; chronic myelomonocytic leukemia (CMML), n = 8] by immunohistochemistry using an anti-VEGF antibody. In normal bone marrow, the anti-VEGF antibody was found to react with myeloid progenitor cells, immature monocytic cells, plasma cells and megakaryocytes, but not with erythroid cells or mature granulocytic cells. Higher levels of VEGF were found in patients with MDS, subtypes RAEB, RAEB-T and CMML, compared to patients with RA or RARS, or the normal bone marrow. These differences were found to result from expression of VEGF in immature myeloid cells in RAEB, RAEB-T and CMML. The microvessel density was also higher in patients with RAEB-T and CMML compared to RA and RARS or the normal bone marrow. Expression of VEGF mRNA was demonstrable in isolated neoplastic cells by reverse transcriptase-polymerase chain reaction in all patients examined. In aggregate, these data show that VEGF is expressed in bone marrow cells in patients with MDS. The amount of expressed VEGF is related to the percentage of immature myeloid cells (blasts and monocytic progenitors) and correlates with the FAB category.

Differential levels of soluble angiopoietin-2 and Tie-2 in patients with haematological malignancies

The system involving angiopoietin-2 (Ang-2) and its receptor, Tie-2, appears to play an important role not only in tumor angiogenesis, but also in the biology of haematological and non-haematological malignancies. In the present study we evaluated the serum levels of soluble Ang-2 (sAng-2) and soluble Tie-2 (sTie-2) in patients with haematological malignancies. Measurements were carried out in 15 patients with chronic myeloid leukaemia (CML), 25 with essential thrombocythemia (ET), 24 with multiple myeloma (MM) and six with monoclonal gammopathy of undetermined significance (MGUS). In addition, we correlated the levels of angiopoietins with known prognostic factors. sAng-2 and sTie-2 were quantified with enzyme-linked immunosorbent assay (ELISA). In patients with CML and MM the levels of sAng-2 were significantly higher (1686.53 +/- 936.41 pg/mL and 1917.82 +/- 1427 pg/mL, respectively) than in controls (n = 15; 996.096 +/- 414.65 pg/mL) (P < 0.01). In patients with MM sAng-2 levels were significantly increased with increasing stage of disease, from stage I to stage III (P < 0.03) and presented a trend of correlation with Beta2-microglobulin levels (r = 0.317) and grade of bone involvement. Furthermore, the levels of sAng-2 determined after 6 months of chemotherapy in CML patients were significantly lower than at diagnosis in the patients who achieved haematological remission. Circulating sTie-2 levels were increased in patients with ET (17.5 +/- 9.2 vs 9 +/- 3.5 ng/mL; P < 0.01) and in those with CML (16.29 +/- 8.7 ng/mL; P < 0.04). In conclusion, abnormal levels of sAng-2 and sTie-2 are present in some haematological malignancies. These markers may play a role in the pathophysiology of these conditions and their progression.