Endothelial progenitor cells in hematologic malignancies

Stem Cell Responsiveness to Imatinib in Chronic Myeloid Leukemia

Chronic myeloid leukemia (CML) is a clonal myeloproliferative disease characterized by the presence of the BCR-ABL fusion gene, which results from the Philadelphia chromosome. Since the introduction of tyrosine kinase inhibitors (TKI) such as imatinib mesylate (IM), the clinical outcomes for patients with CML have improved significantly. However, IM resistance remains the major clinical challenge for many patients, underlining the need to develop new drugs for the treatment of CML. The basis of CML cell resistance to this drug is unclear, but the appearance of additional genetic alterations in leukemic stem cells (LSCs) is the most common cause of patient relapse. However, several groups have identified a rare subpopulation of CD34+ stem cells in adult patients that is present mainly in the bone marrow and is more immature and pluripotent; these cells are also known as very small embryonic-like stem cells (VSELs). The uncontrolled proliferation and a compromised differentiation possibly initiate their transformation to leukemic VSELs (LVSELs). Their nature and possible involvement in carcinogenesis suggest that they cannot be completely eradicated with IM treatment. In this study, we demonstrated that cells from CML patients with the VSELs phenotype (LVSELs) similarly harbor the fusion protein BCR-ABL and are less sensitive to apoptosis than leukemic HSCs after IM treatment. Thus, IM induces apoptosis and reduces the proliferation and mRNA expression of Ki67 more efficiently in LHSCs than in leukemic LVSELs. Finally, we found that the expression levels of some miRNAs are affected in LVSELs. In addition to the tumor suppressor miR-451, both miR-126 and miR-21, known to be responsible for LSC leukemia-initiating capacity, quiescence, and growth, appear to be involved in IM insensitivity of LVSELs CML cell population. Targeting IM-resistant CML leukemic stem cells by acting via the miRNA pathways may represent a promising therapeutic option.

High Output Heart Failure in Multiple Myeloma: Pathogenetic Considerations

Simple Summary

Multiple myeloma is a plasma cell disorder that accounts for around 10% of all haematological malignancies. This neoplasia is often associated with a significant prevalence of cardiovascular complications resulting from several factors, unrelated and/or related to the disease. Among cardiovascular complications, the high output heart failure is of great importance as it is related to a worse prognosis for patients. It is important to point out that, despite the availability of more and more numerous and effective drugs, myeloma remains an incurable disease, with frequent relapses and several treatment lines, with the need, therefore, for a careful evaluation of patients, especially from a cardiological point of view. For this reason, we are proposing a comprehensive overview of different pathogenetic mechanisms responsible for high output heart failure in multiple myeloma, including artero-venous shunts, enhanced angiogenesis, glutamminolysis, hyperammonemia and hemorheological alterations, with the belief that a multidisciplinary approach, in clinical evaluation is critical for the optimal management of the patient.

Abstract

The high output heart failure is a clinical condition in which the systemic congestion is associated to a high output state, and it can be observed in a non-negligible percentage of hematological diseases, particularly in multiple myeloma, a condition in which the risk of adverse cardiovascular events may increase, with a worse prognosis for patients. For this reason, though an accurate literature search, we provided in this review a complete overview of different pathogenetic mechanisms responsible for high output heart failure in multiple myeloma. Indeed, this clinical finding is present in the 8% of multiple myeloma patients, and it may be caused by artero-venous shunts, enhanced angiogenesis, glutamminolysis, hyperammonemia and hemorheological alterations with increase in plasma viscosity. The high output heart failure in multiple myeloma is associated with significant morbidity and mortality, emphasizing the need for a multidisciplinary approach.

Differences in the reaction of hyperlipidemia on different endothelial progenitor cells based on sex

The sex of a patient can affect the outcomes of several cardiovascular diseases, and men generally tend to experience earlier episodes of cardiovascular diseases compared with women. The progression of atherosclerosis during hyperlipidemia can be induced by reactive oxygen species (ROS) and oxidized-low-density lipoprotein (ox-LDL). By contrast, bone marrow (BM)-derived endothelial progenitor cells (EPCs) have been reported to serve a protective role against atherosclerosis. The aim of the present was to compare the effects of sex under conditions of hyperlipidemia on different populations of EPCs, and to identify the potential underlying mechanisms. EPC numbers and ROS levels in the blood and BM were measured using fluorescence activated cell sorting in male and female LDL receptor knock-out C57BL/6 mice maintained on a high-fat diet for 6 months, and in male and female wild type C57BL/6 mice following ox-LDL injection for 3 days. Female hyperlipidemic mice exhibited lower levels of plasma lipids, atherosclerotic plaque formation, intracellular EPC ROS formation and inflammatory cytokine levels. Furthermore, BM CD34⁺/ fetal liver kinase-1 (Flk-1⁺), CD34⁺/CD133⁺ and stem cell antigen-1⁺/Flk-1⁺, as well as all circulating EPCs, were maintained at higher levels in female hyperlipidemic mice. In addition, similar changes with regards to BM CD34⁺/Flk-1⁺, CD34⁺/CD133⁺, c-Kit⁺/CD31⁺ and circulating CD34⁺/Flk1⁺ and CD34⁺/CD133⁺ EPCs were observed in female mice following ox-LDL treatment. These sustained higher levels of BM and circulating EPCs in female mice with hyperlipidemia may be associated with reduced levels of ox-LDL as a result of reduced intracellular ROS formation in EPCs and decreased inflammatory cytokine production.

Assessment of endothelial progenitor cells, VEGF-A and SDF-1α in Hodgkin's lymphoma

Recently, there is great interest in vasculogenesis, a process of the formation of new blood vessels from progenitor cells or angioblasts, in the pathogenesis of cancer. To the best of our knowledge, the evaluation of endothelial progenitor cells (EPCs) in Hodgkin's lymphoma has not yet been reported. The aim of the present study was to assess the number of EPCs and selected cytokines, such as vascular endothelial growth factor (VEGF-A) and stromal cell-derived factor (SDF-1α) involved in vasculogenesis in Hodgkin's lymphoma patients. The study was conducted in a group of 42 patients with Hodgkin's lymphoma (eight patients with relapsed Hodgkin's lymphoma and 34 patients before the first treatment) and 30 healthy controls. The number of EPCs defined as CD31(+), CD34(+), CD45(-), CD133(+) was analysed on FacsCalibur flow cytometer and the concentration of VEGF-A and SDF-1α was assessed by ELISA. The study showed that there was a significantly higher EPCs number and VEGF-A concentration in the blood of Hodgkin's lymphoma patients compared to healthy individuals (8.20 vs. 0.55 cells/μl; P < 0.000001; 85.10 vs. 25.33 pg/ml, P = 0.000017; respectively). Detailed analysis revealed that there was elevated EPCs number in both study subgroups as compared to the control group. However, there was no difference in VEGF concentration between recurrent Hodgkin's lymphoma patients and the control group. A significant positive correlation was found between the number of EPCs and VEGF-A concentration (R = 0.31, P = 0.047). Significantly higher EPCs number combined with increased VEGF-A concentration, found in Hodgkin's lymphoma patients before the first treatment, suggest stimulation of new blood vessels formation, which may in turn contribute to tumour growth and metastasis in these patients.

Endothelial Progenitors in the Tumor Microenvironment

Tumor vascularization refers to the formation of new blood vessels within a tumor and is considered one of the hallmarks of cancer. Tumor vessels supply the tumor with oxygen and nutrients, required to sustain tumor growth and progression, and provide a gateway for tumor metastasis through the blood or lymphatic vasculature. Blood vessels display an angiocrine capacity of supporting the survival and proliferation of tumor cells through the production of growth factors and cytokines. Although tumor vasculature plays an essential role in sustaining tumor growth, it represents at the same time an essential way to deliver drugs and immune cells to the tumor. However, tumor vasculature exhibits many morphological and functional abnormalities, thus resulting in the formation of hypoxic areas within tumors, believed to represent a mechanism to maintain tumor cells in an invasive state.Tumors are vascularized through a variety of modalities, mainly represented by angiogenesis, where VEGF and other members of the VEGF family play a key role. This has represented the basis for the development of anti-VEGF blocking agents and their use in cancer therapy: however, these agents failed to induce significant therapeutic effects.Much less is known about the cellular origin of vessel network in tumors. Various cell types may contribute to tumor vasculature in different tumors or in the same tumor, such as mature endothelial cells, endothelial progenitor cells (EPCs), or the same tumor cells through a process of transdifferentiation. Early studies have suggested a role for bone marrow-derived EPCs; these cells do not are true EPCs but myeloid progenitors differentiating into monocytic cells, exerting a proangiogenic effect through a paracrine mechanism. More recent studies have shown the existence of tissue-resident endothelial vascular progenitors (EVPs) present at the level of vessel endothelium and their possible involvement as cells of origin of tumor vasculature.

Germline mutations: many roles in leukemogenesis

PURPOSE OF REVIEW

The purpose of this review is to summarize the current understanding of germline mutations as they contribute to leukemia development and progression. We also discuss how these new insights may help improve clinical management of germline mutations associated with leukemia.

RECENT FINDINGS

Germline mutations may represent important initial mutations in the development of leukemia where interaction with somatic mutations provide further hits in leukemic progression. In addition, germline mutations may also contribute to leukemogenesis by impacting bone marrow stem-cell microenvironment and immune cell development and function.

SUMMARY

Leukemia is characterized by the clonal expansion of malignant cells secondary to somatic or germline mutations in a variety of genes. Understanding somatic mutations that drive leukemogenesis has drastically improved our knowledge of leukemia biology and led to novel therapeutic strategies. Advances have also been made in identifying germline mutations that may affect leukemic development and progression. This review will discuss the biological and clinical relationship of germline mutations with clonal hematopoiesis, bone marrow microenvironment, and immunity in the progression of leukemia.

Artemisinin and its derivatives: a potential treatment for leukemia

Artemisinin (ART) and its derivatives are one of the most important classes of antimalarial agents, originally derived from a Chinese medicinal plant called Artemisia annua L. Beyond their outstanding antimalarial and antischistosomal activities, ART and its derivatives also possess both in-vitro and in-vivo activities against various types of cancer. Their anticancer effects range from initiation of apoptotic cell death to inhibition of cancer proliferation, metastasis and angiogenesis, and even modulation of the cell signal transduction pathway. This review provides a comprehensive update on ART and its derivatives, their mechanisms of action, and their synergistic effects with other chemicals in targeting leukemia cells. Combined with limited evidence of drug resistance and low toxicity profile, we conclude that ART and its derivatives, including dimers, trimers, and hybrids, might be a potential therapeutic alternative to current chemotherapies in combating leukemia, although more studies are necessary before they can be applied clinically.

Endothelial Progenitor Cell-Derived Extracellular Vesicles: A Novel Candidate for Regenerative Medicine and Disease Treatment

Extracellular vesicles (EVs) are a heterogeneous group of membranous structures, which can be secreted by most cell types. As a product of paracrine secretion, EVs are considered to be a regulatory mediator for intercellular communication. There are many bioactive cargos in EVs, such as proteins, lipids, and nucleic acids. As the precursor cell of vascular endothelial cells (ECs), endothelial progenitor cells (EPCs) are first discovered in peripheral blood. With the development of studies about the functions of EPCs, an increasing number of researchers focus on EPC-derived EVs (EPC-EVs). EPC-EVs exert key functions for promoting angiogenesis in regenerative medicine and show significant therapeutic effects on a variety of diseases such as circulatory diseases, kidney diseases, diabetes, bone diseases, and tissue/organ damages. This article reviews the current knowledge on the role of EPC-EVs in regenerative medicine and disease treatment, discussing the main challenges and future directions in this field.

Evaluation of bone marrow microenvironment could change how myelodysplastic syndromes are diagnosed and treated

Myelodysplastic syndromes are a heterogeneous group of clonal hematopoietic disorders. However, the therapies used against the hematopoietic stem cells clones have limited efficacy; they slow the evolution toward acute myeloid leukemia rather than stop clonal evolution and eradicate the disease. The progress made in recent years regarding the role of the bone marrow microenvironment in disease evolution may contribute to progress in this area. This review presents the recent updates on the role of the bone marrow microenvironment in myelodysplastic syndromes pathogenesis and tries to find answers regarding how this information could improve myelodysplastic syndromes diagnosis and therapy.

VEGF, ANGPT1, ANGPT2, and MMP-9 expression in the autologous hematopoietic stem cell transplantation and its impact on the time to engraftment

As a site of complicated interactions among cytokines, bone marrow niche has been the subject of many scientific studies, mainly in the context of the proteins influencing damage or recovery of endothelium after allogeneic hematopoietic stem cell transplantation (HSCT). In this study, we aimed at exploring mutual correlations of bone marrow niche cytokines involved in the homing and mobilization of hematopoietic stem cells, as well as in angiogenesis. The aim of our study was to evaluate levels of cytokines: VEGF, angiopoietin-1 (ANGPT1), angiopoietin-2 (ANGPT2), and matrix metalloproteinase 9 (MMP-9) during autologous HSCT and to examine their influence on hematological recovery. Forty-three patients with hematological malignancies (33 multiple myeloma, 10 lymphoma) were enrolled in the study. Plasma samples were taken at five time points: before conditioning treatment (BC), on transplantation day (0) and 7 (+7), 14 (+14), and 21 (+21) days after HSCT. The cytokine levels were evaluated by ELISA method. Our study revealed decreased levels of VEGF, ANGPT1, and MMP-9 in the early post-transplant period as compared to the baseline (BC). ANGPT2 was decreased after conditioning treatment, but tended to increase from day +7. On day +7, positive correlations between ANGPT1 level as well as MMP-9 and the time to engraftment were observed. As opposite to ANGPT1, negative correlation between ANGPT2 level on day +7 after HSCT and the time to hematological recovery was noticed. Our study suggests that investigated cytokines are an important part of bone marrow environment and significantly influence the time to engraftment after HSCT.

The microenvironment in human myeloid malignancies: emerging concepts and therapeutic implications

Similar to their healthy counterpart, malignant hematopoietic stem cells in myeloid malignancies, such as myeloproliferative neoplasms, myelodysplastic syndromes, and acute myeloid leukemia, reside in a highly complex and dynamic cellular microenvironment in the bone marrow. This environment provides key regulatory signals for and tightly controls cardinal features of hematopoietic stem cells (HSCs), including self-renewal, quiescence, differentiation, and migration. These features are essential to maintaining cellular homeostasis and blood regeneration throughout life. A large number of studies have extensively addressed the composition of the bone marrow niche in mouse models, as well as the cellular and molecular communication modalities at play under both normal and pathogenic situations. Although instrumental to interrogating the complex composition of the HSC niche and dissecting the niche remodeling processes that appear to actively contribute to leukemogenesis, these models may not fully recapitulate the human system due to immunophenotypic, architectural, and functional inter-species variability. This review summarizes several aspects related to the human hematopoietic niche: (1) its anatomical structure, composition, and function in normal hematopoiesis; (2) its alteration and functional relevance in the context of chronic and acute myeloid malignancies; (3) age-related niche changes and their suspected impact on hematopoiesis; (4) ongoing efforts to develop new models to study niche-leukemic cell interaction in human myeloid malignancies; and finally, (5) how the knowledge gained into leukemic stem cell (LSC) niche dependencies might be exploited to devise novel therapeutic strategies that aim at disrupting essential niche-LSC interactions or improve the regenerative ability of the disease-associated hematopoietic niche.

Advances in Monitoring Cell-Based Therapies with Magnetic Resonance Imaging: Future Perspectives

Cell-based therapies are currently being developed for applications in both regenerative medicine and in oncology. Preclinical, translational, and clinical research on cell-based therapies will benefit tremendously from novel imaging approaches that enable the effective monitoring of the delivery, survival, migration, biodistribution, and integration of transplanted cells. Magnetic resonance imaging (MRI) offers several advantages over other imaging modalities for elucidating the fate of transplanted cells both preclinically and clinically. These advantages include the ability to image transplanted cells longitudinally at high spatial resolution without exposure to ionizing radiation, and the possibility to co-register anatomical structures with molecular processes and functional changes. However, since cellular MRI is still in its infancy, it currently faces a number of challenges, which provide avenues for future research and development. In this review, we describe the basic principle of cell-tracking with MRI; explain the different approaches currently used to monitor cell-based therapies; describe currently available MRI contrast generation mechanisms and strategies for monitoring transplanted cells; discuss some of the challenges in tracking transplanted cells; and suggest future research directions.