Large-scale generation of autologous dendritic cells for immunotherapy in patients with acute myeloid leukemia

Quantitative and Functional Assessment of the Influence of Routinely Used Cryopreservation Media on Mononuclear Leukocytes for Medical Research

Quantitative and functional analysis of mononuclear leukocyte populations is an invaluable tool to understand the role of the immune system in the pathogenesis of a disease. Cryopreservation of mononuclear cells (MNCs) is routinely used to guarantee similar experimental conditions. Immune cells react differently to cryopreservation, and populations and functions of immune cells change during the process of freeze–thawing. To allow for a setup that preserves cell number and function optimally, we tested four different cryopreservation media. MNCs from 15 human individuals were analyzed. Before freezing and after thawing, the distribution of leukocytes was quantified by flow cytometry. Cultured cells were stimulated using lipopolysaccharide, and their immune response was quantified by flow cytometry, quantitative polymerase chain reaction (qPCR), and enzyme-linked immunosorbent assay (ELISA). Ultimately, the performance of the cryopreservation media was ranked. Cell recovery and viability were different between the media. Cryopreservation led to changes in the relative number of monocytes, T cells, B cells, and their subsets. The inflammatory response of MNCs was altered by cryopreservation, enhancing the basal production of inflammatory cytokines. Different cryopreservation media induce biases, which needs to be considered when designing a study relying on cryopreservation. Here, we provide an overview of four different cryopreservation media for choosing the optimal medium for a specific task.

Immune Response After Radiofrequency Ablation and Surgical Resection in Nonsmall Cell Lung Cancer

The objective includes radiofrequency ablation (RFA) of a cancerous nodule results in immunogenic cell death. Tumor antigens are presented and the inflammatory environment may help stimulate adaptive and innate antitumor immunity. The objective of this study was to investigate the immune response following RFA and subsequent surgical resection in early stage non-small cell lung cancer (NSCLC). In methods, a single-session approach of computed tomography-guided tumor biopsy with immediate frozen section (and proof of NSCLC) was performed followed by RFA of the tumor in 4 patients with a solitary pulmonary nodule. Blood samples were collected before RFA and 3 days thereafter. All patients underwent radical surgical resection by video-assisted thoracoscopic lobectomy 8 days following RFA. In results, intense infiltrations of CD4⁺ and CD8⁺ lymphocytes were found along the perimeter of the RFA-treated tumor tissue, whereas the central tumor areas remained devoid of lymphocytes. In the peripheral blood, the frequency of proinflammatory, immunostimulatory IFNγ-secreting, and immunostimulatory BDCA-3⁺/B7-H3^- dendritic cells increased after RFA. Furthermore, a significant increase in T-cell proliferation was detected in T-cell assays after RFA and tumor resection. In this article, a local and systemic immune response subsequent to RFA and complete surgical resection in patients with NSCLC was identified for the first time. Treatment of patients with NSCLC with RFA and surgery leads to an activated and highly T-cell-stimulatory phenotype of dendritic cells, which may promote long-term immunity against NSCLC. The data suggest that the RFA-induced necrotic tumor debris can serve as an in situ antigen source to induce an autologous antitumor immune response.

Dendritic cells derived from pluripotent stem cells: Potential of large scale production

Human pluripotent stem cells (hPSCs), including human embryonic stem cells and human induced pluripotent stem cells, are promising sources for hematopoietic cells due to their unlimited growth capacity and the pluripotency. Dendritic cells (DCs), the unique immune cells in the hematopoietic system, can be loaded with tumor specific antigen and used as vaccine for cancer immunotherapy. While autologous DCs from peripheral blood are limited in cell number, hPSC-derived DCs provide a novel alternative cell source which has the potential for large scale production. This review summarizes recent advances in differentiating hPSCs to DCs through the intermediate stage of hematopoietic stem cells. Step-wise growth factor induction has been used to derive DCs from hPSCs either in suspension culture of embryoid bodies (EBs) or in co-culture with stromal cells. To fulfill the clinical potential of the DCs derived from hPSCs, the bioprocess needs to be scaled up to produce a large number of cells economically under tight quality control. This requires the development of novel bioreactor systems combining guided EB-based differentiation with engineered culture environment. Hence, recent progress in using bioreactors for hPSC lineage-specific differentiation is reviewed. In particular, the potential scale up strategies for the multistage DC differentiation and the effect of shear stress on hPSC differentiation in bioreactors are discussed in detail.

The characterization and role of leukemia cell-derived dendritic cells in immunotherapy for leukemic diseases

Usually, an effective anti-leukemia immune response cannot be initiated effectively in patients with leukemia. This is probably related to immunosuppression due to chemotherapy, down-regulation of major histocompatibility complex (MHC) II molecules, and the lack of co-stimulatory molecules on dendritic cells (DC). In light of this problem, some methods had been used to induce leukemia cells to differentiate into mature DCs, causing them to present leukemia-associated antigens and activating naïve T cells. Furthermore, leukemia-derived DCs could be modified with tumor antigens or tumor-associated antigens to provide a new approach to anti-leukemia therapy. Numerous studies have indicated factors related to the induction and functioning of leukemia-derived DCs and the activation of cytotoxic T-lymphocytes (CTLs). These include the amount of purified DCs, cytokine profiles appropriate for inducing leukemia-derived DCs, effective methods of activating CTLs, reasonable approaches to DC vaccines, and the standardization of their clinical use. Determining these factors could lead to more effective leukemia treatment and benefit both mankind and scientific development. What follows in a review of advances in and practices of inducing leukemia-derived DCs and the feasibility of their clinical use.

Activation of autologous leukemia-specific T cells in acute myeloid leukemia: monocyte-derived dendritic cells cocultured with leukemic blasts compared with leukemia-derived dendritic cells

In acute myeloid leukemia (AML) blasts can be differentiated into dendritic cell (DC) like cells (AML-DC). These cells have a mature DC-like phenotype, are strong stimulators in mixed leukocyte reactions and can be used to generate leukemia-specific cytotoxic T cells. However, recent reports about naturally existing leukemic DC with immunoregulatory dysfunctions in peripheral blood of AML patients caused concerns about the use of AML-DC for therapeutic purposes. Systematic intra-individual comparisons between AML-DC and non-leukemic DC derived from monocytes (MoDC) in AML patients are missing. Thus, we investigated the ability to generate MoDC from peripheral blood of 17 AML patients in first remission and their functional integrity to stimulate leukemia-specific T cells by simple coculture with leukemic blasts. Phenotypic analysis of AML-DC and MoDC from the same individual patients revealed that MoDC exhibit a more homogenous mature DC phenotype. Additionally, functional analysis demonstrated the ability of remission MoDC to activate autologous leukemia-specific T cells in 11 of 12 patients, whereas AML-DC led to a specific T cell activation in four of eight patients. The presented findings might have impact on the design of further therapeutic studies using autologous antigen-presenting cells.

Quantitative expression of Toll-like receptor-2, -4, and -9 in dendritic cells generated from blasts of patients with acute myeloid leukemia

BACKGROUND

Dendritic cells (DCs) generated from leukemic blasts constitute a promising tool in immunotherapy for acute myeloid leukemia patients (AML-DCs), because AML-DCs express human leukocyte antigens and costimulatory molecules such as CD40, CD80, and CD86 at a higher level than leukemic blasts. Potentiation of AML-DC vaccine might become feasible by the addition of adjuvants such as lipopolysaccharides (LPS) or CPG-rich oligodeoxyribonucleotides binding to Toll-like receptors (TLR) and inducing a stronger Type 1 T-cell response.

STUDY DESIGN AND METHODS

mRNA and protein expression of TLR-2, -4, and -9 were analyzed with quantitative real-time polymerase chain reaction, Western blot, and flow cytometry for mature monocyte-derived DCs generated from 14 AML patients versus 14 healthy volunteers (HV-DCs), and the response of the AML- and HV-DCs to different microbial TLR ligands was determined by enzyme-linked immunosorbent assay for the proinflammatory cytokines tumor necrosis factor (TNF)-alpha, inducible protein (Ip)-10, and interleukin (IL)-6.

RESULTS

AML-DCs and HV-DCs strongly expressed TLR-2 and TLR-4, while TLR-9 was expressed at a lower level in both groups. There was no significant difference in TLR expression between the two groups of AML-DCs and HV-DCs. In accordance with the TLR expression levels, DCs generated from both AML patients and HVs responded to the known microbial ligands peptidoglycan (PGN) and lipoteichoic acid for TLR-2 and LPS as ligand for TLR-4, by producing TNF-alpha and IL-6. A response to the ODNs 2006 and 2216 binding to TLR-9 was only detected in AML-DCs.

CONCLUSION

Microbial ligands like ODNs and LPS constitute promising adjuvants for enhancing (AML-) DC vaccines.