Medical costs of treatment and survival of patients with acute myeloid leukemia in Belgium

The advent of new cell-based immunotherapies for leukemia offers treatment possibilities for certain leukemia subgroups. The wider acceptability of these new technologies in clinical practice will depend on its impact on survival and costs. Due to the small patient groups who have received it, these aspects have remained understudied. This non-randomized single-center study evaluated medical costs and survival for acute myeloid leukemia between 2005 and 2010 in 50 patients: patients treated with induction and consolidation chemotherapy (ICT) alone; patients treated with ICT plus allogeneic hematopoietic stem cell transplantation (HCT), which is the current preferred post-remission therapy in patients with intermediate- and poor-risk AML with few co-morbidities, and patients treated with ICT plus immunotherapy using autologous dendritic cells (DC) engineered to express the Wilms' tumor protein (WT1). Total costs including post- consolidation costs on medical care at the hematology ward and outpatient clinic, pharmaceutical prescriptions, intensive care ward, laboratory tests and medical imaging were analyzed. Survival was markedly better in HCT and DC. HCT and DC were more costly than ICT. The median total costs for HCT and DC were similar. These results need to be confirmed to enable more thorough cost-effectiveness analyses, based on observations from multicenter, randomized clinical trials and preferably using quality-adjusted life-years as an outcome measure.

Highly efficient gene delivery by mRNA electroporation in human hematopoietic cells: superiority to lipofection and passive pulsing of mRNA and to electroporation of plasmid cDNA for tumor antigen loading of dendritic cells

Designing effective strategies to load human dendritic cells (DCs) with tumor antigens is a challenging approach for DC-based tumor vaccines. Here, a cytoplasmic expression system based on mRNA electroporation to efficiently introduce tumor antigens into DCs is described. Preliminary experiments in K562 cells using an enhanced green fluorescent protein (EGFP) reporter gene revealed that mRNA electroporation as compared with plasmid DNA electroporation showed a markedly improved transfection efficiency (89% versus 40% EGFP(+) cells, respectively) and induced a strikingly lower cell toxicity (15% death rate with mRNA versus 51% with plasmid DNA). Next, mRNA electroporation was applied for nonviral transfection of different types of human DCs, including monocyte-derived DCs (Mo-DCs), CD34(+) progenitor-derived DCs (34-DCs) and Langerhans cells (34-LCs). High-level transgene expression by mRNA electroporation was obtained in more than 50% of all DC types. mRNA-electroporated DCs retained their phenotype and maturational potential. Importantly, DCs electroporated with mRNA-encoding Melan-A strongly activated a Melan-A-specific cytotoxic T lymphocyte (CTL) clone in an HLA-restricted manner and were superior to mRNA-lipofected or -pulsed DCs. Optimal stimulation of the CTL occurred when Mo-DCs underwent maturation following mRNA transfection. Strikingly, a nonspecific stimulation of CTL was observed when DCs were transfected with plasmid DNA. The data clearly demonstrate that Mo-DCs electroporated with mRNA efficiently present functional antigenic peptides to cytotoxic T cells. Therefore, electroporation of mRNA-encoding tumor antigens is a powerful technique to charge human dendritic cells with tumor antigens and could serve applications in future DC-based tumor vaccines.

Gene therapy: principles and applications to hematopoietic cells

Ever since the development of technology allowing the transfer of new genes into eukaryotic cells, the hematopoietic system has been an obvious and desirable target for gene therapy. The last 10 years have witnessed an explosion of interest in this approach to treat human disease, both inherited and acquired, with the initiation of multiple clinical protocols. All gene therapy strategies have two essential technical requirements. These are: (1) the efficient introduction of the relevant genetic material into the target cell and (2) the expression of the transgene at therapeutic levels. Conceptual and technical hurdles involved with these requirements are still the objects of active research. To date, the most widely used and best understood vectors for gene transfer in hematopoietic cells are derived from retroviruses, although they suffer from several limitations. However, as gene transfer mechanisms become more efficient and long-term gene expression is enhanced, the variety of diseases that can be tackled by gene therapy will continue to expand. However, until the problem of delivery and subsequent expression is adequately resolved, gene therapy will not realize its full potential. The first part of this review gives an overview of the gene delivery technology available at present to transfer genetic sequences in human somatic cells. The relevance of the hematopoietic system to the development of gene therapy strategies as well as hematopoietic cell-based gene therapy is discussed in the second part.

Gene-based cancer vaccines: an ex vivo approach

The application of gene transfer techniques to immunotherapy has animated the field of gene-based cancer vaccine research. Gene transfer strategies were developed to bring about active immunization against tumor-associated antigens (TAA) through gene transfer technology. A wide variety of viral and nonviral gene transfer methods have been investigated for immunotherapeutic purposes. Ex vivo strategies include gene delivery into tumor cells and into cellular components of the immune system, including cytotoxic T cells and dendritic cells (DC). The nature of the transferred genetic material as well as the gene transfer method has varied widely depending on the application. Several of these approaches have already been translated into clinical gene therapy trials. In this review, we will focus on the rationale and types of ex vivo gene-based immunotherapy of cancer. Critical areas for future development of gene-based cancer vaccines are addressed, with particular emphasis on use of DC and on the danger-tolerance hypothesis. Finally, the use of gene-modified DC for tumor vaccination and its prospects are discussed.

Efficient generation of stably electrotransfected human hematopoietic cell lines without drug selection by consecutive FACsorting

BACKGROUND

Current methods to establish stably transfected cell lines by nonviral techniques involve coselection for a drug selection marker. However, this approach suffers from several drawbacks. We developed a fluorescence-activated cell sorting (FACS)-based protocol for the selection and isolation of stable hematopoietic electrotransfectants without the need for selective growth conditions.

METHODS

Leukemic K562 cells were electroporated with the enhanced green fluorescent protein (EGFP) reporter gene and FACsorted to obtain stably EGFP-expressing cells. Stable EGFP(+) clones were established by single-cell sorting.

RESULTS

Efficiency of stable EGFP gene expression increased steadily in function of number of consecutive FACsorts. Stable transfectants (>99% EGFP(+)) were obtained after four FACsorts. Furthermore, several single-cell derived clones with variable levels of stable EGFP expression were isolated and cultured without the use of selective growth media.

CONCLUSIONS

EGFP is an effective selection marker for the generation and isolation of stably transfected hematopoietic cell clones without the need for selection in toxic media that could create a potentially undesirable stress environment for stably transfected cells.

High-level transgene expression in primary human T lymphocytes and adult bone marrow CD34+ cells via electroporation-mediated gene delivery

The design of effective gene delivery systems for gene transfer in primary human blood cells is important both for fundamental hematopoiesis research and for cancer gene therapy strategies. Here, we evaluated electroporation as a nonviral means for transfection of activated human T lymphocytes and adult bone marrow (BM) CD34+ cells. We describe optimal culture and electroporation parameters for efficient gene delivery in prestimulated T lymphocytes (16.3 +/-1.3%), as well as 2-day cultured adult BM CD34+ cells (29.6+/-4.6%). PHA-stimulated T cells were most receptive for transfection after 48h of in vitro culture, while T cells stimulated by CD3 cross-linking and interleukin (IL)-2 achieved maximum transfection levels after 72 h of prestimulation. Kinetic analysis of EGFP expression revealed that activated T lymphocytes maintained transgene expression at high levels for a prolonged period. In addition, fresh unstimulated BM CD34+ cells were consistently transfected (5.2+/-0.4%) with minimal cytotoxicity (<5%), even without preliminary CD34+ cell purification. Both T cells and CD34+ cells retained their phenotype and functional capacity after electroporation. These results demonstrate that electroporation is a suitable nonviral transfection technique that may serve applications in gene therapy protocols using T lymphocytes or CD34+ cells.

Nonviral transfection of distinct types of human dendritic cells: high-efficiency gene transfer by electroporation into hematopoietic progenitor- but not monocyte-derived dendritic cells

Human dendritic cells (DC) are highly professional antigen presenting cells for the priming of naive cytotoxic T cells. Gene transfer in DC would be a useful strategy to load DC with relevant de novo synthesized antigens for immunotherapeutical purposes. As a first step towards a DC-based gene therapy, we examined the efficiency of nonviral transfection in different types of cultured human dendritic cells with a humanized red-shifted green fluorescent protein reporter gene. Plasmid DNA transfection by electroporation or lipofection was used to transfect CD34+ progenitor cell-derived DC (PC-DC) and Langerhans' cells (PC-LC), as well as monocyte-derived DC (Mo-DC). While lipofection was unsuccessful in all types of DC, we obtained high-efficiency gene transfer by electroporation in PC-LC (16%) and PC-DC (12%). In contrast, electroporation was strikingly less efficient in Mo-DC (< or = 2%). The potent allostimulatory capacity of DC was still retained in electroporated PC-DC and PC-LC. In conclusion, electroporation of antigen expressing plasmid DNA is an efficient tool for nonviral gene transfer in PC-DC and PC-LC, but not in Mo-DC and could be useful for the development of DC-based tumor immunotherapy.

Generation of dendritic cells from bone marrow progenitors using GM-CSF, TNF-alpha, and additional cytokines: antagonistic effects of IL-4 and IFN-gamma and selective involvement of TNF-alpha receptor-1

We report the generation of dendritic cells (DC) starting from CD34+ bone marrow (BM) progenitor cells, using a two-stage culture system in which, besides granulocyte-macrophage colony-stimulating factor (GM-CSF) and tumour necrosis factor-alpha (TNF-alpha), stem-cell factor (SCF) was added during the first 5 days, while interleukin-4 (IL-4) and/or interferon-gamma (IFN-gamma) were added during the secondary culture period of 9 days. Addition of IL-4 favoured the outgrowth of CD1a+, HLA-DR+, CD4+, CD40+, CD80+ but CD14- cells with dendritic morphology and strong antigen-presenting capacity. Addition of IFN-gamma selectively induced HLA-DR and CD86 but did not up-regulate CD1a expression or antigen-presenting capacity of the differentiated cells. An antagonism between IL-4 and IFN-gamma could further be confirmed in that, as compared with IL-4 alone, the simultaneous addition of IL-4 and IFN-gamma to GM-CSF plus TNF-alpha during maturation reduced both the phenotypical (CD1a, CD4, CD40) and functional characteristics of DC. Using receptor-specific TNF-alpha mutants, we investigated the relative involvement of TNF-alpha receptors R1 and R2 in the generation of DC. The induction of CD1a and HLA-DR, as well as the increase in allostimulatory capacity were dependent on TNF-R1 triggering, whereas triggering through TNF-R2 had no measurable effect. We conclude first, that the expansion of DC from BM progenitors could most effectively be enhanced in a two-stage culture assay using SCF, GM-CSF, TNF-alpha and IL-4; second, that the effect of TNF-alpha in DC generation involves signalling via the TNF-R1 receptor; and third, that IFN-gamma counteracts some of the effects of IL-4 in DC generation.