Dendritic cell vaccines in acute leukaemia

Cellular Immunotherapy for Hematologic Malignancies: Beyond Bone Marrow Transplantation

Immunotherapy has changed treatment practices for many hematologic malignancies. Even in the current era of targeted therapy, chemotherapy remains the backbone of treatment for many hematologic malignancies, especially in acute leukemias, where relapse remains the major cause of mortality. Application of novel immunotherapies in hematology attempts to harness the killing power of the immune system against leukemia and lymphoma. Cellular immunotherapy is evolving rapidly for high-risk hematologic disorders. Recent advances include chimeric antigen-receptor T cells, mesenchymal stromal/stem cells, dendritic cell tumor vaccines, cytokine-induced killer cells, and virus-specific T cells. The advantages of nontransplantation cellular immunotherapy include suitability for patients for whom transplantation has failed or is contraindicated, and a potentially less-toxic treatment alternative to transplantation for relapsed/refractory patients. This review examines those emerging cellular immunotherapies that are changing treatment paradigms for patients with hematologic malignancies.

Wilms tumor 1 peptide vaccination after hematopoietic stem cell transplant in leukemia patients

Although the prognosis of leukemia patients after allogeneic hematopoietic stem cell transplantation (HSCT) has greatly improved, relapse is still a major cause of death after HSCT. Cancer vaccines may have the potential to enhance the graft-versus-leukemia (GVL) effect. The post-allogeneic HSCT period provides a unique platform for vaccination, because (I) tumor burden is minimal, (II) lymphopenia allows for rapid expansion of cytotoxic T cells (CTLs), (III) donor-derived CTLs are not exhausted, (IV) inflammation is caused by alloreactions, and (V) the abundance of regulatory T cells is low due to their late recovery. Tumor cell lysates, dendritic cells (DCs), and peptides derived from leukemia-associated antigens (LAAs) have been used as vaccines. Clinical trials with several types of vaccines for post-HSCT patients revealed that the vaccination induced an immunological response and might benefit patients with minimal residual disease; however, the efficacy of this approach must be examined in randomized studies. In addition, it is important to consider the combination of cancer vaccine with checkpoint antibodies, recently shown to be useful in treating leukemia relapse after HSCT.

Effect of thymosin α₁ on the phenotypic and functional maturation of dendritic cells from children with acute lymphoblastic leukemia

To determine the effect of thymosin α1 (Tα1) on the phenotypic and functional maturation of HL‑60 cells, freeze‑thaw antigen‑loaded dendritic cells (DCs) were derived from peripheral blood mononuclear cells (PBMCs) of children with acute lymphoblastic leukemia (ALL). The DCs were generated from the PBMC samples that were collected from the PB of 10 consecutive ALL children. On day 3 of culturing, the cells in the antigen + no Tα1 (AN) and antigen + Tα1 (AT) groups were incubated with 100 µl lysates obtained from freeze‑thaw cycling. After 5 days of incubation, the AT group was administered with 100 ng/ml Tα1. On day 8, the DCs were stained with fluorescein isothiocyanate‑conjugated cluster of differentiation (CD)1a, CD83 and HLA‑DR antibodies and analyzed by flow cytometry. In addition, the killing activity of cytotoxic T lymphocytes (CTLs) from the different groups on wild‑type leukemia cells was measured. The DCs in the AT group exhibited more apparent, characteristic dendritic morphologies than the control and AN group DCs. Furthermore, the lowest expression level of CD1a, and the highest expression of CD83 and HLA‑DR were observed in the AT group when compared with the AN and control groups (P<0.05). The lactate dehydrogenase release assay demonstrated that the killing rate of CTL in the AT group was significantly higher than that in the control and AN groups (P<0.01). Thus, Tα1 may markedly promote the phenotypic and functional maturation of DCs, and may serve as a suitable immunomodulator of DC‑based immunotherapy for treatment of hematological malignancies.

Detection and isolation of dendritic cells using Lewis X-functionalized magnetic nanoparticles

dendritic cell (DC)-specific intracellular adhesion molecule-3 grabbing nonintegrin (DC-SIGN) is a receptor found on DCs that recognizes antigens bearing mannose-rich or fucosylated glycans, including Lewis X (Le(X)). Here, we report the fabrication of magnetic nanoparticles coated with multivalent Le(X) glycans using Cu (I)-catalyzed azide-alkyne cycloaddition. The resulting nanoparticles are selective and biocompatible, serving as a highly efficient tool for DC detection and enrichment.

[Dendritic cell-based therapeutic vaccination for acute myeloid leukemia]

The long-term outlook for adult patients with acute myeloid leukemia (AML) remains dismal. The main reason for this state of affairs lies in the fact that the majority of AML patients will eventually relapse, even after obtaining complete remission following front-line chemotherapy. Relapses are generally attributed to the persistence of a small number of chemotherapy-resistant leukemic (stem) cells, a condition known as minimal residual disease (MRD). The eradication of MRD, with the eventual aim of reducing the risk of relapse, therefore represents a high-priority goal of modern AML therapy. It is now well established that the immune system plays a crucial role in the defense against AML. This knowledge has fuelled the development of immune-based approaches to control MRD and, ultimately, to prevent relapse. One of the promising strategies that have emerged in this regard involves the use of dendritic cells for therapeutic vaccination. This review article aims to introduce the reader into the conceptual and practical aspects of DC-based vaccination for AML. Next, we will review the first clinical results obtained with this immunotherapeutic approach in AML patients. Finally, we will briefly reflect on the potential place of DC vaccination in the future therapy of AML.

Enhancement of specific cellular immune response induced by DNA vaccines encoding PML-RARalpha and hIL-2 genes

A DNA vaccine encoding PML-RAR alpha fusion gene is thought to be a promising approach for acute promyelocytic leukemia patients to enhance immune responses after attaining complete remission. In this study, we sought to enhance cellular immunity by coexpressing human interleukin (hIL)-2 genes. Successfully constructed plasmids PML-RAR alpha-hIL-2-pIRES, PML-RAR alpha-pIRES and hIL-2-pIRES were delivered intramuscularly in BALB/C mice at 14-day intervals for three cycles. The cellular immune responses with respect to the specific cytotoxicity of spleen cells; interferon-gamma secretion in sera, and the T-cell receptor rearrangement excision circles of thymocyte were significantly increased from PML-RARalpha-hIL-2-pIRES immunized mice. Our results indicate that a DNA vaccine with PML fusion gene segment and hIL-2 together might elicit increased cellular immune responses in mice.

Immunotherapy prospects for acute myeloid leukaemia

While chemotherapy is successful at inducing remission of acute myeloid leukaemia (AML), the disease has a high probability of relapse. Strategies to prevent relapse involve consolidation chemotherapy, stem cell transplantation and immunotherapy. Evidence for immunosurveillance of AML and susceptibility of leukaemia cells to both T cell and natural killer (NK) cell attack and justifies the application of immune strategies to control residual AML persisting after remission induction. Immune therapy for AML includes allogeneic stem cell transplantation, adoptive transfer of allogeneic or autologous T cells or NK cells, vaccination with leukaemia cells, dendritic cells, cell lysates, peptides and DNA vaccines and treatment with cytokines, antibodies and immunomodulatory agents. Here we describe what is known about the immunological features of AML at presentation and in remission, the current status of immunotherapy and strategies combining treatment approaches with a view to achieving leukaemia cure.

An examination of chimpanzee use in human cancer research

Advocates of chimpanzee research claim the genetic similarity of humans and chimpanzees make them an indispensable research tool to combat human diseases. Given that cancer is a leading cause of human death worldwide, one might expect that if chimpanzees were needed for, or were productive in, cancer research, then they would have been widely used. This comprehensive literature analysis reveals that chimpanzees have scarcely been used in any form of cancer research, and that chimpanzee tumours are extremely rare and biologically different from human cancers. Often, chimpanzee citations described peripheral use of chimpanzee cells and genetic material in predominantly human genomic studies. Papers describing potential new cancer therapies noted significant concerns regarding the chimpanzee model. Other studies described interventions that have not been pursued clinically. Finally, available evidence indicates that chimpanzees are not essential in the development of therapeutic monoclonal antibodies. It would therefore be unscientific to claim that chimpanzees are vital to cancer research. On the contrary, it is reasonable to conclude that cancer research would not suffer, if the use of chimpanzees for this purpose were prohibited in the US. Genetic differences between humans and chimpanzees, make them an unsuitable model for cancer, as well as other human diseases.

Dendritic cell preparation for immunotherapeutic interventions

Much effort has been made over the last decade to use dendritic cells (DCs) in vaccines to induce specific antitumor immune responses. However, the great hope provided by in vitro and in vivo preclinical investigations was not translated to the clinic in terms of clinical efficacy. Thus, one of the challenges resides in optimizing DC-based therapy to give maximum clinical efficacy while using manufacturing processes that enable quality control and scale-up of consistent products. In this article, we review DC biology and the DC-based clinical trials performed to date and focus on the DC maturation status compatible with the goals of cancer immunotherapy. We also highlight the different approaches used in these clinical studies, such as the DC types or subtypes used and their preparation. Finally, we discuss the immunological and clinical outcomes in treated patients, with emphasis on the strategies that could be used to improve DC-based vaccination.