Immunotherapy with acute leukemia cells modified into antigen-presenting cells: ex vivo culture and gene transfer methods

Synergistic effect of Toll-like receptor 4 and 7/8 agonists is necessary to generate potent blast-derived dendritic cells in Acute Myeloid Leukemia

Leukemic cells from AML patients can be differentiated to dendritic cells (DCs). Such DCs have potential for immunotherapy of patients. Blasts from 15 AML patients were differentiated into DCs and matured by different TLR agonists. We could generate AML-DCs from 73% of patients mostly with M4 or M5 subtypes. The DC recoveries ranged from 28% to 50%. The results showed that concomitant use of TLR4 and TLR7/8 agonists induced proficient DCs. Therefore, a combination of TLR4 and 7/8 agonists can be considered as an appropriate maturation cocktail for AML-DC production in order to use in the immunotherapy of AML patients.

In vitro-induced response patterns of antileukemic T cells: characterization by spectratyping and immunophenotyping

Myeloid leukemic cells can be induced to differentiate into leukemia-derived dendritic cells (DCleu) regaining the stimulatory capacity of professional DCs while presenting the leukemic antigen repertoire. But so far, the induced antileukemic T-cell responses are variable both in specificity and in efficacy. In an attempt to elucidate the underlying causes of different T-cell response patterns, T-cell receptor (TR) Vβ chain rearrangements were correlated with the T cells corresponding immunophenotypic profile, as well as their proliferative response and cytolytic capacities. In three different settings, donor T cells, either human leukocyte antigen matched or mismatched (haploidentical), or autologous T cells were repeatedly stimulated with myeloid blasts or leukemia-derived DC/DCleus from the corresponding patients diseased from acute myeloid leukemia (AML). Although no significant differences in T-cell proliferation were observed, the T-cell-mediated cytolytic response pattern varied considerably and even caused blast proliferation in two cases. Spectratyping revealed a remarkable restriction (>75% of normal level) of the CD4+ or CD8+-TR repertoire of blast- or DC/DCleu-stimulated T cells. Although in absolute terms, DC/DCleu stimulation induced the highest grade of restriction in the CD8+ T-cell subset, the CD4+ T-cell compartment seemed to be relatively more affected. But most importantly, in vitro stimulation with DC/DCleu resulted into an identical TR restriction pattern (β chain) that could be identified in vivo in a patient sample 3 months after allo-SCT. Thus, in vitro tests combining functional flow cytometry with spectratyping might provide predictive information about T cellular response patterns in vivo.

Elevated frequencies of leukemic myeloid and plasmacytoid dendritic cells in acute myeloid leukemia with the FLT3 internal tandem duplication

Some 30% of acute myeloid leukemia (AML) patients display an internal tandem duplication (ITD) mutation in the FMS-like tyrosine kinase 3 (FLT3) gene. FLT3-ITDs are known to drive hematopoietic stem cells towards FLT3 ligand independent growth, but the effects on dendritic cell (DC) differentiation during leukemogenesis are not clear. We compared the frequency of cells with immunophenotype of myeloid DC (mDC: Lin⁻, HLA-DR⁺, CD11c⁺, CD86⁺) and plasmacytoid DC (pDC: Lin⁻, HLA-DR⁺, CD123⁺, CD86⁺) in diagnostic samples of 47 FLT3-ITD⁻ and 40 FLT3-ITD⁺ AML patients. The majority of ITD⁺ AML samples showed high frequencies of mDCs or pDCs, with significantly decreased HLA-DR expression compared with DCs detectable in ITD⁻ AML samples. Interestingly, mDCs and pDCs sorted out from ITD⁺ AML samples contained the ITD insert revealing their leukemic origin and, upon ex vivo culture with cytokines, they acquired DC morphology. Notably, mDC/pDCs were detectable concurrently with single lineage mDCs and pDCs in all ITD⁺ AML (n = 11) and ITD⁻ AML (n = 12) samples analyzed for mixed lineage DCs (Lin⁻, HLA-DR⁺, CD11c⁺, CD123⁺). ITD⁺ AML mDCs/pDCs could be only partially activated with CD40L and CpG for production of IFN-α, TNF-α, and IL-1α, which may affect the anti-leukemia immune surveillance in the course of disease progression.

In acute myeloid leukemia, B7-H1 (PD-L1) protection of blasts from cytotoxic T cells is induced by TLR ligands and interferon-gamma and can be reversed using MEK inhibitors

B7-H1 (PD-L1) is a B7-related protein that inhibits T-cell responses. B7-H1 participates in the immunoescape of cancer cells and is also involved in the long-term persistence of leukemic cells in a mouse model of leukemia. B7-H1 can be constitutively expressed by cancer cells, but is also induced by various stimuli. Therefore, we examined the constitutive and inducible expression of B7-H1 and the consequences of this expression in human acute myeloid leukemia (AML). We analyzed B7-H1 expression in a cohort of 79 patients with AML. In addition, we studied blast cells after incubation with interferon-gamma or toll-like receptors (TLR) ligands. Finally, we evaluated functionality of cytotoxic T-cell activity against blast cells. Expression of B7-H1 upon diagnosis was high in 18% of patients. Expression of TLR2, 4 and 9 was detected in one-third of AML samples. Expression of TLR2 and TLR4 ligands or IFN-γ induced by B7-H1 was found to protect AML cells from CTL-mediated lysis. Spontaneous B7-H1 expression was also found to be enhanced upon relapse in some patients. MEK inhibitors, including UO126 and AZD6244, reduced B7-H1 expression and restored CTL-mediated lysis of blast cells. In AML, B7-H1 expression by blasts represents a possible immune escape mechanism. The inducibility of B7-H1 expression by IFN-γ or TLR ligands suggests that various stimuli, either produced during the immune response against leukemia cells or released by infectious microorganisms, could protect leukemic cells from T cells. The efficacy of MEK inhibitors against B7-H1-mediated inhibition of CTLs suggests a possible cancer immunotherapy strategy using targeted drugs.

Quality of T-cells after stimulation with leukemia-derived dendritic cells (DC) from patients with acute myeloid leukemia (AML) or myeloid dysplastic syndrome (MDS) is predictive for their leukemia cytotoxic potential

Myeloid leukemic cells can differentiate into leukemia-derived dendritic cells (DC(leu)), presenting known/unknown leukemic-antigens. Induced anti-leukemic T-cell-responses are variable. To further elicit DC/DC(leu)-induced T-cell-response-patterns we performed (functional)flow-cytometry/fluorolysis-assays before/after mixed lymphocyte cultures (MLC) of matched (allogeneic) donor-T-cells (n=6), T-cells prepared at relapse after stem cell transplantation (n=4) or (autologous) patients'-T-cells (n=7) with blast-containing-mononuclear-cells ('MNC') or DC(leu)-containing DC ('DC'). Compared to 'MNC' 'DC' were better mediators of anti-leukaemic T-cell-activity, although not in every case effective. We could define cut-off proportions of mature DC, DC(leu), proliferating, CD4(+), CD8(+) and non-naive T-cells after 'MNC'- or 'DC'-stimulation, that were predictive for an anti-leukemic-activity of stimulated T-cells as well as a response to immunotherapy. Interestingly especially ratios >1 of CD4:CD8 or CD45RO:CD45RA T-cells were predictive for anti-leukemic function after DC-stimulation. In summary the composition and quality of DC and T-cells after a MLC-stimulating-phase is predictive for a successful ex-vivo and in-vivo anti-leukemic response, especially with respect to proportions of proliferating, CD4(+) and CD45RO(+) T-cells. Successful cytotoxicity and the development of a T-cell-memory after 'DC'-stimulation could be predictive for the clinical course of the disease and may pave the way to develop adoptive immunotherapy, especially for patients at relapse after SCT.

Is it important to decipher the heterogeneity of "normal karyotype AML"?

Almost half of adult acute myelogenous leukemia (AML) is normal cytogenetically, and this subgroup shows a remarkable heterogeneity of genetic mutations at the molecular level and an intermediate response to therapy. The finding of recurrent cytogenetic abnormalities has influenced, in a primary way, the understanding and treatment of leukemias. Yet "normal karyotype AML" lacks such obvious abnormalities, but has a variety of prognostically important genetic abnormalities. Thus, the presence of a FLT3-ITD (internal tandem duplication), MLL-PTD (partial tandem duplication), or the increased expression of ERG or EVI1 mRNAs confer a poor prognosis, and an increased risk of relapse. In contrast, the presence of cytoplasmic nucleophosmin or C/EBPA mutations is associated with lower relapse rates and improved survival. Although resistance to treatment is associated with specific mutations, the degree to which the leukemia resembles a stem cell in its functional properties may provide greater protection from the effects of treatment. Although usually all of the circulating leukemia cells are cleared following treatment, a small residual population of leukemic cells in the bone marrow persists, making this disease hard to eradicate. Increased understanding of the biological consequences of at least some of these mutations in "normal karyotype AML" is leading to more targeted approaches to develop more effective treatments for this disease.

Gene transfer of noncleavable cell surface mutants of human CD154 induces the immune response and diminishes systemic inflammatory reactions

CD154 (CD40-ligand) is a critical transmembrane molecule with potent immune-stimulatory properties that is used in clinical applications of gene therapy for leukemia and lymphoma. However, CD154 is cleaved into a soluble form, and high levels of sCD154 contribute to systemic inflammatory and cardiovascular diseases, suggesting a deleterious side effect of CD154 gene therapy. In this study, we engineered noncleavable mutants of human CD154 with point mutations to develop a potentially less toxic molecule in vivo. In contrast to wild-type CD154 (CD154-WT) subsequently released as sCD154, both mutants CD154-M3 and CD154-M4 were resistant to cleavage in tumor cells. Also, CD40-expressing leukemia B cells transfected with CD154-M3 mutant were highly effective stimulators in a mixed lymphocyte-leukemia reaction, indicating that CD154-M3 mutant did not lose biologic activity. In mice transplanted with tumors expressing CD154-WT, we found increased plasma levels of human sCD154 followed by various systemic inflammatory reactions such as glomerulonephritis and an increased number of infiltrating mononuclear cells in the liver. However, CD154-M3 mutant did not induce any systemic inflammatory effects in vivo. As such, the noncleavable mutant of CD154 is fully capable of inducing the immune response with less toxic properties and is a useful tool for CD154 immune gene therapy.

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

BACKGROUND

Mononuclear cells (MNCs) of severely impaired acute myeloid leukemia (AML) patients may be collected by leukapheresis for large-scale generation of dendritic cells (AML-DCs) under good manufacturing practice (GMP) conditions for adoptive immunotherapy.

STUDY DESIGN AND METHODS

In five end-stage AML patients, a leukapheresis procedure was performed with a cell separator (either COBE Spectra [Gambro BCT] or Amicus [Baxter]). For large-scale AML-DC generation, the MNCs of a single leukapheresis concentrate were isolated by density gradient and plated into a cell factory under GMP conditions. The AML-DCs were harvested on Day 8 of culture, and their viability, the mature morphology, and the phenotype were evaluated. The AML-DCs were injected subcutaneously into five AML patients up to four times at a biweekly interval.

RESULTS

All AML patients entered the leukapheresis procedure with a highly pathologic blood count. In a mean separation time of 198 +/- 33 minutes, a mean of 1.3 +/- 0.2-fold the total blood volume was processed with a white blood cell (WBC) yield of 9 x 10(9) to 70 x 10(9) per collection dependent on the precollection WBC count. After density gradient a mean of 2.2 x 10(9) +/- 0.3 x 10(9) MNCs were plated into a cell factory. This resulted in a mean viable and mature DC yield of 0.01 x 10(9) of MNCs.

CONCLUSION

The leukapheresis procedure is a feasible and safe procedure even in patients with hematologic malignancies and highly pathologic blood counts. Sufficient amounts of MNCs can be collected in leukopenic patients and the large-scale generation of AML-DCs in cell factories under GMP conditions yields in an adequate quantity of viable and mature AML-DCs.

Enhancement of the anti-leukemic activity of cytokine induced killer cells with an anti-CD19 chimeric receptor delivering a 4-1BB-ζ activating signal

OBJECTIVE

There is growing interest in the use of cytokine-induced killer (CIK) cells in cancer therapy. In this study, we sought to maximize the antileukemic activity of anti-CD19 receptor-modified CIK cells against B-lineage acute lymphoblastic leukemia (ALL).

MATERIALS AND METHODS

CIK cells were transduced with retroviral vectors carrying different types of anti-CD19 chimeric receptors: anti-CD19-zeta, anti-CD19-DAP10, anti-CD19-4-1BB-zeta, and anti-CD19-CD28-zeta. A truncated form of the receptor was used as a control. Transduced CIK cells were then analyzed for their cytotoxic activity against ALL cells and for their capability to proliferate and to release cytokines after ALL encounter.

RESULTS

CIK cells were efficiently transduced with all the anti-CD19 retroviral vectors. Anti-CD19 receptor expression conferred powerful killing activity against ALL cells. However, there were clear advantages when receptors containing the co-stimulatory molecules 4-1BB or CD28 were transduced. Such cells had significantly more potent cytotoxicity than cells expressing the anti-CD19-zeta or anti-CD19-DAP10. Moreover, the presence of 4-1BB or CD28 in the receptor increased the production of interleukin (IL)-2, tumor necrosis factor (TNF)-alpha, TNF-beta, IL-5, IL-6, and IL-8 elicited by coculture with ALL cells. Notably, anti-CD19-4-1BB-zeta CIK cells secreted particularly low levels of interleukin-10 and proliferated strongly after contact with ALL cells.

CONCLUSIONS

Anti-CD19 chimeric receptors delivering primary and costimulatory signals render CIK cells powerfully cytotoxic against ALL cells and induce secretion of immunostimulatory cytokines and proliferation. These results support the testing of genetically modified CIK cells in clinical trials.

Proinflammatory response of human leukemic cells to dsRNA transfection linked to activation of dendritic cells

Leukemic cells exert immunosuppressive effects that interfere with dendritic cell (DC) function and hamper effective antileukemic immune responses. Here, we sought to enhance the immunogenicity of leukemic cells by loading them with the double-stranded (ds) RNA Toll-like receptor 3 (TLR3) ligand polyriboinosinic polyribocytidylic acid (poly(I:C)), mimicking viral infection of the tumor cells. Given the responsiveness of DC to TLR ligands, we hypothesized that the uptake of poly(I:C)-loaded leukemic cells by immature DC (iDC) would lead to DC activation. Primary acute myeloid leukemia (AML) cells and AML cell lines markedly responded to poly(I:C) electroporation by apoptosis, upregulation of TLR3 expression, enhanced expression of major histocompatibility complex (MHC) and costimulatory molecules and by production of type I interferons (IFN). Upon phagocytosis of poly(I:C)-electroporated AML cells, DC maturation and activation were induced as judged by an increased expression of MHC and costimulatory molecules, production of proinflammatory cytokines and an increase of T helper 1 (T(H)1)-polarizing capacity. These immune effects were suboptimal when AML cells were passively pulsed with poly(I:C), indicating the superiority of poly(I:C) transfection over pulsing. Our results demonstrate that poly(I:C) electroporation is a promising strategy to increase the immunogenicity of AML cells and to convert iDC into activated mature DC following the phagocytosis of AML cells.

Synergistic antileukemia effect of combinational gene therapy using murine b-defensin 2 and IL-18 in L1210 murine leukemia model

Murine beta-defensin 2 (MBD2) is not only chemotactic for immature dendritic cells but also activates them by Toll-like receptor 4. We have previously demonstrated that vaccine with MBD2 elicited potent antileukemia responses in the L1210 murine model. Interleukin-18 (IL-18) is an essential cytokine for the generation of Th1 response and natural killer cells and cytotoxic T lymphocytes (CTL) activation. As MBD2 and IL-18 appear to function on different components required by an effective antitumor immune response including both innate and adaptive immunity, we investigated whether combinatorial delivery of MBD2 and IL-18 transduced L1210 cells could elicit synergistic antileukemia effects. First, we constructed a single plasmid vector carrying both pro-IL-18 and IL-1beta converting enzyme (ICE) genes, and found that transfection of this vector into L1210 cells resulted in efficient secretion of bioactive IL-18. Combinatorial delivery of MBD2 and pro-IL-18-ICE modified L1210 cells conferred a superior inhibition of leukemogenicity over either L1210-MBD2 or L1210-pro-IL-18-ICE alone; moreover, the survived mice developed long-lasting protective immunity as determined by rechallenge experiments. This combined vaccine also elicited the most marked therapeutic effect, CTL activity and interferon-gamma production. These results suggest that the combination of MBD2 and IL-18 induces more effective antileukemia activity and provides a promising strategy for cancer therapy.

T cells stimulated by CD40L positive leukemic blasts-pulsed dendritic cells meet optimal functional requirements for adoptive T-cell therapy

Adoptive T-cell immunotherapy may provide complementary therapy for childhood B-cell precursor acute lymphoblastic leukemia (BCP-ALL). In this study, we have analyzed the functional characteristics of anti-BCP-ALL effector T cells generated by co-culturing T lymphocytes and dendritic cells (DC) from allogeneic human stem cell transplantation (HSCT) donors. After 21-day co-culture with DC pulsed with CD40L+ apoptotic BCP-ALL blasts, T cells presented with both effector and central memory phenotype, and showed high and specific cytotoxic activity against leukemic cells (average lysis = 77%), mostly mediated by CD8+ T cells. Noticeably, growth of CD4 T cells was maintained (45% of total cells), which actively produced Th1 cytokines (IFN-gamma, TNF-alpha, IL-2), but not IL-4, IL-5 and IL-10. Anti-BCP-ALL T cells expressed CD49d and CXCR4 (implicated in the recruitment to bone marrow), and CD62L and CCR7 (involved in the migration to lymphoid organs). In accordance with this profile, T cells significantly migrated in response to the chemokines CXCL12 and CCL19. In conclusion, stimulation of T cells with CD40L+BCP-ALL cells-loaded DC not only elicited the generation of potent and specific anti-leukemic cytotoxic effectors, but also the differentiation of specific and functional Th-1 CD4 lymphocytes. These effectors are fully equipped to reach leukemia-infiltrated tissues and have characteristics to support and orchestrate the anti-tumor immune-response.

Murine model of immune-mediated rejection of the acute lymphoblastic leukemia 70Z/3

70Z/3 is a murine pre-B cell leukemia line derived from BDF(1) mice and has been used in the study of signaling pathways in B cells. 70Z/3 cells were initially found to cause widespread disease upon injections in animals. We have isolated 70Z/3 variants divergent in their capacity to lead to morbidity after injections. One variant, 70Z/3-NL, elicits an immune response protecting the animal from tumor growth. Another variant, 70Z/3-L, does not induce an effective immune response and causes morbidity. We demonstrated that both CD4(+) and CD8(+) T cells are required for the rejection of 70Z/3-NL cells. Interestingly, the immune response generated against 70Z/3-NL cells was found to protect against a challenge with the lethal variant, 70Z/3-L. This indicates that although both lines can be recognized and killed by the immune system, only 70Z/3-NL is capable of inducing a protective response. Further observations, using subclones isolated from 70Z/3-NL, demonstrated that immune recognition of a portion of the cells was sufficient for protection. Depletion of CD4(+) and CD8(+) T cells in animals injected previously with 70Z/3-NL cells showed that T cells, and not Abs, were required for the maintenance of the protection initiated by 70Z/3-NL. We tested the capacity of 70Z/3-NL cells to treat mice challenged with 70Z/3-L. We can delay injections of 70Z/3-NL and still provide protection for the animals. We have a model of immune-mediated rejection which will allow us to dissect the requirements for the initiation of immune responses against an ALL tumor cell line.

Vaccine with beta-defensin 2-transduced leukemic cells activates innate and adaptive immunity to elicit potent antileukemia responses

Murine beta-defensin 2 (MBD2) is a small antimicrobial peptide of the innate immune system. Recent study showed that MBD2 could not only recruit immature dendritic cells but also activate them by Toll-like receptor 4 and thus may provide a critical link between the innate immune system and the adaptive immune response. In this report, we examined the antileukemia activity of MBD2 in a murine model of acute lymphoid leukemia (ALL) L1210. L1210 cells were engineered to secrete biologically functional MBD2. MBD2-modified L1210 (L1210-MBD2) showed significantly reduced leukemogenecity, resulting in a 80% rate of complete leukemia rejection. Inoculation of mice with L1210-MBD2 induced enhanced CTL and natural killer (NK) activity and augmented interleukin-12 and IFN-gamma production. All the recovered mice from the inoculation showed a protective immunity to the following challenge with parental L1210 cells and generate leukemia-specific memory CTL. Vaccines with irradiated L1210-MBD2 cells could cure 50% leukemia-bearing mice. Depletion of CD8+ T cells but not CD4+ T cells completely abrogated the antileukemia activity of MBD2. Interestingly, NK cells were also required for the MBD2-mediated antileukemia response, although ALL generally display a high degree of resistance to NK-mediated lysis. Our results suggest that MBD2 can activate both innate and adaptive immunity to generate potent antileukemia response, and MBD2 immunotherapy warrants further evaluation as a potential treatment for ALL.

Immunotherapy of high-risk acute leukemia with a recipient (autologous) vaccine expressing transgenic human CD40L and IL-2 after chemotherapy and allogeneic stem cell transplantation

CD40L generates immune responses in leukemia-bearing mice, an effect that is potentiated by IL-2. We studied the feasibility, safety, and immunologic efficacy of an IL-2- and CD40L-expressing recipient-derived tumor vaccine consisting of leukemic blasts admixed with skin fibroblasts transduced with adenoviral vectors encoding human IL-2 (hIL-2) and hCD40L. Ten patients (including 7 children) with high-risk acute myeloid (n = 4) or lymphoblastic (n = 6) leukemia in cytologic remission (after allogeneic stem cell transplantation [n = 9] or chemotherapy alone [n = 1]) received up to 6 subcutaneous injections of the IL-2/CD40L vaccine. None of the patients were receiving immunosuppressive drugs. No severe adverse reactions were noted. Immunization produced a 10- to 890-fold increase in the frequencies of major histocompatibility complex (MHC)-restricted T cells reactive against recipient-derived blasts. These leukemia-reactive T cells included both T-cytotoxic/T-helper 1 (Th1) and Th2 subclasses, as determined from their production of granzyme B, interferon-gamma, and interleukin-5. Two patients produced systemic IgG antibodies that bound to their blasts. Eight patients remained disease free for 27 to 62 months after treatment (5-year overall survival, 90%). Thus, even in heavily treated patients, including recipients of allogeneic stem cell transplants, recipient-derived antileukemia vaccines can induce immune responses reactive against leukemic blasts. This approach may be worthy of further study, particularly in patients with a high risk of relapse.

Serum-free generation and quantification of functionally active Leukemia-derived DC is possible from malignant blasts in acute myeloid leukemia and myelodysplastic syndromes

Functional dendritic cells (DC) are professional antigen presenting cells (APC) and can be generated in vitro from leukemic cells from acute myeloid leukemia AML patients, giving rise to APC of leukemic origin presenting leukemic antigens (DC(leu)). We have already shown that DC can be successfully generated from AML and myeloplastic syndromes (MDS) cells in serum-free 'standard' medium (X-vivo + GM-CSF + IL-4 +TNFalpha + FL) in 10-14 days. In this study, we present that DC counts generated from mononuclear cells (MNC) varied between 20% (from 55 MDS samples), 34% (from 100 AML samples) and 25% (from 38 healthy MNC samples) medium. Between 53% and 58% of DC are mature CD83+ DC. DC harvests were highest in monocytoid FAB types (AML-M4/M5, MDS-CMML) and independent from cytogenetic risk groups, demonstrating that DC-based strategies can be applied for patients with all cytogenetic risk groups. Proof of the clonal derivation of DC generated was obtained in five AML and four MDS cases with a combined FISH/immunophenotype analysis (FISH-IPA): The clonal numerical chromosome aberrations of the diseases were regularly codetectable with DC markers; however, not with all clonal cells being convertible to leukemia-derived DC(leu) (on average, 53% of blasts in AML or MDS). To the contrary, not all DC generated carried the clonal aberration (on average, 51% of DC). In 41 AML and 13 MDS cases with a suitable antigen expression, we could confirm FISH-IPA data by Flow cytometry: although DC(leu) are regularly detectable, on average only 57% of blasts in AML and 64% of blasts in MDS were converted to DC(leu). After coculture with DC in mixed lymphocyte reactions (MLR), autologous T cells from AML and MDS patients proliferate and upregulate costimulatory receptors. The specific lysis of leukemic cells by autologous T cells could be demonstrated in three cases with AML in a Fluorolysis assay. In six cases with only few DC(leu) or few vital T cells available after the DC/MLR procedure, no lysis of allogeneic or autologous leukemic cells was seen, pointing to the crucial role of both partners in the lysis process. We conclude: (1) the generation of DC is regularly possible in AML and also in MDS under serum-free conditions. (2) Clonal/leukemia-derived DC(leu) can be regularly generated from MDS and AML-MNC; however, not with all blasts being converted to DC(leu) and not all DC generated carrying leukemic markers. We recommend to select DC(leu) for vaccinations or ex vivo T-cell activations to avoid contaminations with non-converted blasts and non-leukemia-derived DC and to improve the harvest of specific, anti-leukemic T cells. DC and DC-primed T cells could provide a practical strategy for the immunotherapy of AML and MDS.

Leukemia-Derived Dendritic Cells can be Generated from Blood or Bone Marrow Cells from Patients with Acute Myeloid Leukaemia: A Methodological Approach under Serum-Free Culture Conditions

Functional dendritic cells (DC) are professional antigen-presenting cells (APC) and can be generated in vitro from healthy as well as from leukaemic cells from acute myeloid leukemia (AML) patients giving rise to APC of leukaemic origin-presenting leukaemic antigens. We describe the generation and characterization of DC from different mononuclear cell (MNC) fractions from 50 AML patients under different serum-free culture conditions, determine the optimal culture conditions and compare the results with that from 23 healthy donors. In parallel cultures, we compared DC harvests after 7- or 14-day culture, with total or adherent MNC or T-cell depleted MNC or peripheral blood (PB) or bone marrow-MNC (BM-MNC), thawn or fresh MNC, in Xvivo or CellGro serum-free media, +/-10% autologous plasma or +/-FL. In detail, we could show that AML-DC harvests were higher after 10-14 days culture (healthy DC: 7 days); total or adherent PB or BM-MNC fractions yield comparable DC counts, however, from magnetic cell sorting (MACS)-depleted MNC fractions or thawn MNC lower DC counts can be generated. Whereas the addition of FL increases the DC harvest, the addition of autologous plasma in many cases has inhibitory influence on DC maturation. CellGro and Xvivo media yield comparable DC counts. Optimal harvest of vital and mature DC from AML samples was obtained with a granulocyte/macrophage-colony stimulating factor, interleukin-4, FL and tumour necrosis factor-alpha-containing serum-free Xvivo medium after 10-14 days of culture (36/26% DC; 38/64% vital DC; 46/51% mature DC were generated from AML/healthy MNC samples). Surface marker profiles (e.g. costimulatory antigen expressing) of DC obtained from AML samples were comparable with that of healthy DC. The leukaemic derivation of AML-DC was demonstrated by the persistence of the clonal cytogenetic aberration in the DC or by coexpression of leukaemic antigens on DC. Autologous T-cell activation of leukaemia-derived DC was demonstrated in cases with AML. Autologous T cells proliferate and upregulate DC-contact-relevant antigens. We demonstrate that the generation of leukaemia-derived DC is feasable in AML under serum-free culture conditions giving rise to DC with comparable characteristics as healthy DC and offering an anti-leukaemia-directed immunotherapeutical vaccination strategy in AML.

Leukaemia-Derived Dendritic Cells Can Be Generated From Blood or Bone Marrow Cells From Patients With Myelodysplasia: A Methodological Approach Under Serum-Free Culture Conditions

Functional dendritic cells (DC) are professional antigen-presenting cells (APC) and can be generated in vitro from healthy as well as from leukaemic cells from AML patients giving rise to APC of leukaemic origin presenting leukaemic antigens. In a comparative methodological analysis of 50 AML samples, we could already show that leukaemia-derived DC can regularly be generated under serum-free culture conditions. In this study, we describe the generation and characterization of DC from different mononuclear cell (MNC) fractions from 24 myelodysplastic syndrome (MDS) patients under those different serum-free culture conditions, determine the optimal culture conditions and compare the results with that from 23 healthy donors. In parallel cultures, we compared DC harvests after 7- or 14-day culture, with total or adherent MNC or T-cell-depleted MNC or PB or BM-MNC, thawn or fresh MNC, in Xvivo or CellGro serum-free media, +/-10% autologous plasma or +/-FL. In detail, we could show that MDS-DC harvests compared to healthy DC were higher after 10- to 14-day culture; total or adherent PB or BM-MNC fractions yield comparable DC counts; however, from MACS-depleted MNC fractions or thawn MNC lower DC counts can be generated. Whereas the addition of FL increases the DC harvest, the addition of autologous plasma in many cases has inhibitory influence on DC maturation, CellGro and Xvivo media yield comparable DC counts. Optimal harvest of vital and mature DC from MDS samples was obtained with a GM-CSF, IL-4, FL and TNF-alpha containing serum-free Xvivo medium after 10-14 days of culture (18/26% DC; 54/64% vital DC; 59/51% mature DC were generated from MDS/healthy MNC samples). Surface marker profiles (e.g. costimulatory antigen expression) of DC obtained from MDS samples were comparable with that of healthy DC. The leukaemic derivation of MDS-DC was demonstrated by the persistence of the clonal cytogenetic aberration in the DC or by coexpression of leukaemic antigens on DC. Autologous T-cell activation of leukaemia-derived DC was demonstrated in cases with MDS. Autologous T cells proliferate and upregulate DC-contact-relevant antigens. We are the first who demonstrate that the generation of leukaemia-derived DC is feasible not only in AML but also in MDS under serum-free culture conditions giving rise to DC with comparable characteristics as healthy DC and offering an antileukaemia-directed immunotherapeutical vaccination strategy in AML and MDS.

Failure to define window of time for autologous tumor vaccination in patients with newly diagnosed or relapsed acute lymphoblastic leukemia

OBJECTIVES

We and others have shown that B cell precursor acute lymphoblastic leukemia cells (ALL) stimulated with CD40 ligand become efficient antigen-presenting cells (APC) capable of expanding autologous, tumor-specific T cells from patients. Translation of these preclinical findings to a novel treatment strategy required four separate issues to be determined: (1) if a CD40-ALL vaccine could be generated for clinical use; (2) whether clinical translation could be achieved; (3) whether the vaccination was safe; and (4) whether a window of time could be identified that would optimize the efficacy of vaccination.

PATIENTS AND METHODS

Nine patients with relapsed/refractory ALL were enrolled in a phase I trial of vaccination with autologous CD40-ALL. Immunologic reconstitution was measured in a separate cohort of 23 patients with newly diagnosed ALL.

RESULTS

We successfully prepared autologous vaccines for all nine patients in the phase I trial. CD40-ALL were potent APC, capable of stimulating allogeneic and peptide-specific T cells in vitro. Two patients were vaccinated without adverse events. Five patients died or progressed before vaccination, suggesting that rapid disease progression limits vaccination in patients with relapse disease, thus limiting clinical translation. We therefore sought to identify a window of time for vaccination during which this approach might be feasible. To achieve this end, we evaluated immunological reconstitution in newly diagnosed patients with ALL patients. Despite recovery of myelopoiesis, most patients had profound defects in T, B, and natural killer (NK) cell numbers that failed to recover at any point during therapy.

CONCLUSION

Autologous tumor vaccination at a time of ALL relapse is not feasible. Alternative strategies for immunotherapy of ALL may require ex vivo generation of antigen specific T cells and adoptive therapy.

Current strategies in cancer gene therapy

Cancer gene therapy is the most studied application of gene therapy. Many genetic alterations are involved in the transformation of a normal cell into a neoplastic one. The two main gene groups involved in cancer development are oncogenes and tumor suppressor genes. While the latter eliminates cancerous cells via apoptosis, the former enhances cell proliferation. Therefore, apoptotic genes and anti-oncogenes are widely used in cancer gene therapy. In addition to oncogenes and tumor suppressor genes, chemotherapy and gene therapy can be combined through suicide gene strategy. A suicide gene encodes for a non-mammalian enzyme; this enzyme is used to convert a non-toxic prodrug into its active cytotoxic metabolite within the cancerous cells. Tumor suppressor genes, anti-oncogenes and suicide genes target cancer cells on the molecular level. On the other hand, cancer is immunogenic in nature; therefore, it can also be targeted on the immunological level. Boosting the immune response against cancerous cells is usually achieved via genes encoding for cytokines. Interleukin-12 gene, for example, is one of the most studied cytokine genes for cancer gene therapy applications. DNA vaccines are also used after conventional treatments to eliminate remnant malignant cells. All these therapeutic strategies and other strategies namely anti-angiogenesis and drug resistant genes are briefly reviewed and highlighted in this article.

Leukemia-derived immature dendritic cells differentiate into functionally competent mature dendritic cells that efficiently stimulate T cell responses

Primary acute myeloid leukemia cells can be induced to differentiate into dendritic cells (DC). In the presence of GM-CSF, TNF-alpha, and/or IL-4, leukemia-derived DC are obtained that display features of immature DC (i-DC). The aim of this study was to determine whether i-DC of leukemic origin could be further differentiated into mature DC (m-DC) and to evaluate the possibility that leukemic m-DC could be effective in vivo as a tumor vaccine. Using CD40L as maturating agent, we show that leukemic i-DC can differentiate into cells that fulfill the phenotypic criteria of m-DC and, compared with normal counterparts, are functionally competent in vitro in terms of: 1) production of cytokines that support T cell activation and proliferation and drive Th1 polarization; 2) generation of autologous CD8(+) CTLs and CD4(+) T cells that are MHC-restricted and leukemia-specific; 3) migration from tissues to lymph nodes; 4) amplification of Ag presentation by monocyte attraction; 5) attraction of naive/resting and activated T cells. Irradiation of leukemic i-DC after CD40L stimulation did not affect their differentiating and functional capacity. Our data indicate that acute myeloid leukemia cells can fully differentiate into functionally competent m-DC and lay the ground for testing their efficacy as a tumor vaccine.

Potential use of CD40 ligand for immunotherapy of childhood B-cell precursor acute lymphoblastic leukaemia

Around 20% of children affected by B-cell precursor acute lymphoblastic leukaemia (BCP-ALL) still experience a recurrence of the disease after diagnosis, despite a significant improvement in the cure rate (80%). Moreover, standard therapies have high and often unacceptable acute and chronic organ toxicity, with an increased risk for secondary malignancies. Therefore, new strategies are needed to improve overall survival and decrease treatment-associated morbidity. Recent in-vitro and in-vivo studies have demonstrated that CD40 engagement improves tumour immunogenicity and, consequently, generates a strong antitumour immune response. The CD40-CD40 ligand (CD40L) system is of pivotal importance in the immune response via interactions between T cells and antigen-presenting cells. The general aim of this chapter is to review the feasibility of developing cellular strategies to increase childhood BCP-ALL immunogenicity, and the potential use of CD40L as a new strategy to induce an antileukaemia immune response in BCP-ALL.

Adhesion capacity and integrin expression by dendritic-like cells generated from acute myeloid leukemia blasts by calcium ionophore treatment

OBJECTIVE

Dendritic cells (DC) play a key role in initiation of immune responses. In vitro modified acute myeloid leukemia (AML) blasts acquire certain specific features of DC and are suggested as a potential source of anti-leukemia vaccines. AML-DC have been characterized in terms of costimulatory molecule expression and cytokine production. In contrast, migratory capacity of AML-DC, which is a major attribute of DC required for their in vivo function, remains unknown. Here we present data on adhesion properties and profile of integrin expression of AML-DC.

MATERIALS AND METHODS

Blasts from nine patients were used to generate AML-DC by calcium ionophore treatment. Adhesion of AML-DC to the major components of the extracellular matrix and the profile of integrin expression was studied using flow cytometry.

RESULTS

Similar to their normal counterparts, calcium ionophore-induced AML-DC acquired the ability to bind to fibronectin and in 4 of 7 studied cases to bind to denatured collagen. Adhesion to native collagen remained unchanged during DC-type differentiation of AML blasts. AML-DC and DC obtained from monocytes of healthy donors expressed CD49d, CD49e, alphavbeta3, and alphavbeta5. However, AML-DC from 3 of 8 patients down-regulated CD49d, which plays an important role in cell-to-cell and cell-to-matrix interactions and normally is coexpressed with CD83.

CONCLUSION

The results provide further evidence that AML blasts can be induced to display functional properties characteristic for DC and may prove useful for in vivo delivery and presentation of tumor antigens to the immune system. Abnormal CD49d expression and variability in AML-DC adhesion to denatured collagen indicate that motility of AML-DC from individual patients may vary, and a customized approach is essential for evaluating leukemic cell feasibility for vaccine design.

CD40 activation of BCP-ALL cells generates IL-10–producing, IL-12–defective APCs that induce allogeneic T-cell anergy

The use of leukemia cells as antigen-presenting cells (APCs) in immunotherapy is critically dependent on their capacity to initiate and sustain an antitumor-specific immune response. Previous studies suggested that pediatric B-cell precursor acute lymphoblastic leukemia (BCP-ALL) cells could be manipulated in vitro through the CD40-CD40L pathway to increase their immunostimulatory capacity. We extended the APC characterization of CD40L-activated BCP-ALL for their potential use in immunotherapy in a series of 19 patients. Engaging CD40 induced the up-regulation of CCR7 in 7 of 11 patients and then the migration to CCL19 in 2 of 5 patients. As accessory cells, CD40L-activated BCP-ALL induced a strong proliferation response of naive T lymphocytes. Leukemia cells, however, were unable to sustain proliferation over time, and T cells eventually became anergic. After CD40-activation, BCP-ALL cells released substantial amounts of interleukin-10 (IL-10) but were unable to produce bioactive IL-12 or to polarize TH1 effectors. Interestingly, adding exogenous IL-12 induced the generation of interferon-γ (IFN-γ)–secreting TH1 effectors and reverted the anergic profile in a secondary response. Therefore, engaging CD40 on BCP-ALL cells is insufficient for the acquisition of full functional properties of immunostimulatory APCs. These results suggest caution against the potential use of CD40L-activated BCP-ALL cells as agents for immunotherapy unless additional stimuli, such as IL-12, are provided.

Functional transfer of CD40L gene in human B-cell precursor ALL blasts by second-generation SIN lentivectors

Three different second-generation lentiviral self-inactivating vectors containing CMV, EF1alpha and PGK promoter, respectively, and all carrying the exogenous GFP gene, were compared for expression in human B-cell precursor ALL blasts. At a comparable percentage of transduction and vector DNA copy number, CMV clearly showed better efficiency of transcription. Human bone marrow stromal cells were favored compared to the MRC-5 cell line, as support for cell viability during infection. Cells were infected and analyzed after variable culture times ranging from 4 to 12 days, to reduce the possibility of pseudotransduction. In 10/14 samples, we detected more than 20% GFP-positive cells after exposure to high-titer viral supernatants. We then tested a similar vector carrying the human CD40L cDNA and, in similar infection conditions, obtained more than 20% transduction in 6/6 samples. The levels of transduction obtained were sufficient to induce the upregulation of CD83 molecule in cocultured immature dendritic cells.

Long-term outcome after intensive therapy with etoposide, melphalan, total body irradiation and autotransplant for acute myeloid leukemia

Intensive therapy and autologous blood and marrow transplantation (ABMT) is an established post-remission treatment for acute myeloid leukemia (AML), although its exact role remains controversial and few data are available regarding longer-term outcomes. We examined the long-term outcome of patients with AML transplanted at a single center using uniform intensive therapy consisting of etoposide, melphalan and TBI. In all, 145 patients with AML underwent ABMT: 117 in first remission, 21 in second remission and seven beyond second remission. EFS and OS were significantly predicted by remission status (P<0.0001). For transplantation in first remission, 8 year EFS and OS were 55% (95% CI, 44-64%) and 62% (95% CI, 50-72%), respectively. By multivariate analysis, only age (P=0.04) and cytogenetic risk group (P=0.006) influenced OS. For patients transplanted in second remission, 8 year EFS and OS were 30% (95% CI, 9-55%) and 36% (95% CI, 13-60%), respectively. No pre-transplant variables significantly predicted outcome. None of the seven patients who underwent ABMT beyond second remission or in early relapse were long-term survivors. ABMT can provide long-term antileukemic control for patients with AML in first remission. For patients in second remission approximately 30% can achieve cure with ABMT, and this option may be preferable to alternate donor allogeneic stem cell transplantation.

Gene transfer of pro-IL-18 and IL-1β converting enzyme cDNA induces potent antitumor effects in L1210 cells

We report in a murine model of acute lymphoid leukemia L1210 the potent antitumor efficiency of a combinatorial delivery of pro-IL-18 gene modified L1210 (Lp18) and IL-1beta converting enzyme (ICE) gene modified L1210 (LpICE). Live leukemia cells Lp18 or Lp18 plus LpICE showed apparently reduced leukemogenicity with a survival rate of 40 or 50% at 50 days after intraperitoneal (i.p.) inoculation of a lethal dose of cells, respectively. Combination of Lp18 and LpICE was capable of inhibiting accumulation of bloody ascites, synergistically superior to Lp18 or LpICE alone. All surviving mice were rechallenged with parental L1210 cells at day 50, and all survived up to day 80, suggesting that gene-modified cells induced immune protection. Moreover, NK cytotoxicity and CTL activity were both enhanced in mice injected with Lp18, especially Lp18 plus LpICE. Levels of IFN-gamma were not altered significantly by inoculation of Lp18 or Lp18 plus LpICE. Our results demonstrate that IL-18 is a useful candidate gene in gene therapy of lymphoma or lymphoid leukemia, and ex vivo combinatorial delivery of Lp18 plus LpICE either as a single approach or as an adjunct to concomitant radiotherapy or chemotherapy, may be more efficient in a situation of minimal residual disease.

CCL3/MIP-1αIs a Potent Immunostimulator When Coexpressed with Interleukin-2 or Granulocyte-Macrophage Colony-Stimulating Factor in a Leukemia/Lymphoma Vaccine

Chemokines orchestrate trafficking of immune effector cells during inflammation. Here we demonstrate that chemokines also serve to potentiate effector cell-mediated antineoplastic immune responses in vaccination strategies. As a critical mediator of inflammation, macrophage inflammatory protein 1alpha (CCL3/MIP-1alpha) attracts and stimulates both antigen-presenting and cytotoxic cells. In the A20 leukemia/lymphoma vaccine model, we explored the efficacy of MIP-1alpha in combination with interleukin-2 (IL-2) or granulocyte-macrophage colony-stimulating factor (GM-CSF). After subcutaneous injection of the MIP-1alpha + IL-2 or MIP-1alpha + GM-CSF combination vaccine, focal but pronounced infiltrates of CD4+ and CD8+ T cells were observed at the vaccination sites. In mice with preestablished leukemia/lymphoma, survival is significantly improved in animals treated with MIP-1alpha + GM-CSF- and MIP-1alpha + IL-2-secreting vaccines. Protection is superior in the MIP-1alpha + GM-CSF group, with the effects of MIP-1alpha and GM-CSF being synergistic. In contrast, suppression of lymphoblast proliferation by single-immunogen vaccines secreting MIP-1alpha, GM-CSF, or IL-2 alone does not translate to improved survival. The systemic protective effects afforded by the MIP-1alpha + IL-2 or MIP-1alpha + GM-CSF combination are mediated by different effector cell populations. In the MIP-1alpha + IL-2 group, antineoplastic defense is mediated by CD8+ T and NK cells, whereas in the MIP-1alpha + GM-CSF group CD4+ T cells are involved in addition to CD8+ cytotoxic T cells, underscoring that T cell help is critical for long-term protection. Thus combination of MIP-1alpha with different cytokines recruits different sets of effector cells into a potent antineoplastic immune response.

Chemotherapy increases transgene expression in leukemic cells

BACKGROUND

Patients with acute myeloid leukemia (AML) often obtain complete remission with chemotherapy but the majority of patients relapse. Combining chemotherapy and gene therapy appears to be a promising approach; however, the effects of chemotherapy on transgene expression in leukemic cells have not yet been investigated.

METHODS

DA1-3b leukemic cells were transfected with pCDNA3 plasmids carrying GM-CSF or LacZ cDNA. The leukemic K562 cell line and primary cultured AML cells were transduced with an Ad5.CMV-LacZ adenoviral vector. Cells were then incubated with various concentrations of daunorubicin (DNR) and cytosine arabinoside (Ara-C), and expression of the transgene was measured. Murine DA1-3b-pCDNA3/LacZ leukemic cells were also injected into syngeneic C3H/Hej mice.

RESULTS

In the cells carrying pCDNA3, DNR and Ara-C dramatically increased expression of the LacZ and GM-CSF transgenes. Over-expression depended on drug dose and was due to increased transcription. Enhancement was also observed in K562 cells and in some primary cultured AML samples transduced with the Ad5.CMV-LacZ adenovirus. Addition of N-acetyl-L-cysteine inhibited the over-expression, suggesting that reactive oxygen species were involved in activating the CMV promoter. In the A549 lung carcinoma cell line transduced with Ad5.CMV-LacZ, Ara-C had only a minor effect, and DNR had a detrimental effect, suggesting that expression depends on cell type. In vivo experiments in which mice received DA1-3b-pCDNA3/LacZ leukemic cells, and were then treated with Ara-C, also showed increased transgene expression in these leukemic cells.

CONCLUSIONS

In leukemic cells, chemotherapeutic agents can induce over-expression of transgenes. This suggests a promising combined strategy for the treatment of acute leukemia.

Immune responses in cancer

The complex of humoral factors and immune cells comprises two interleaved systems, innate and acquired. Immune cells scan the occurrence of any molecule that it considers to be nonself. Transformed cells acquire antigenicity that is recognized as nonself. A specific immune response is generated that results in the proliferation of antigen-specific lymphocytes. Immunity is acquired when antibodies and T-cell receptors are expressed and up-regulated through the formation and release of lymphokines, chemokines, and cytokines. Both innate and acquired immune systems interact to initiate antigenic responses against carcinomas. A new approach to the treatment of cancer has been immunotherapy, which aims to up-regulate the immune system in order that it may better control carcinogenesis. Currently, several forms of immunotherapy that use natural biological substances to activate the immune system are being explored therapeutically. The various forms of immunotherapy fall into three main categories: monoclonal antibodies, immune response modifiers, and vaccines. While these modalities have individually shown some promise, it is likely that the best strategy to combat cancer may require multiple immunotherapeutic strategies in order to demonstrate benefit in different patient populations. It may be that the best results are obtained with vaccines in combination with a variety of immunotherapy combinations. Another potent strategy may be in combining with more traditional cancer drugs as evidenced from the benefit derived from enhancing the efficacy of chemotherapy with cytokines. Through such concerted efforts, a durable, therapeutic antitumour immune response may be achieved and maintained over the course of a patient's lifespan.

The use of lentiviral vectors in gene therapy of leukemia: combinatorial gene delivery of immunomodulators into leukemia cells by state-of-the-art vectors

Our goal is to develop cell vaccines against leukemia cells, genetically modified to express molecules with potent immune-stimulatory capacities. Pre-clinical evaluation of this approach in murine models has demonstrated efficient anti-leukemic responses with the expression of immunomodulators, in particular GM-CSF and CD80, in irradiated cell vaccines. We have previously shown efficient insertion of GM-CSF and CD80 genes into primary human leukemia cells with the use of second and third generation self-inactivating (SIN) lentiviral vectors (Blood 96 (2000), 1317; Leukemia 16 (2002), 1645). The advantages of lentiviral vectors for development of autologous leukemia cell vaccines include: (1) efficient and consistent gene delivery; (2) high levels of transgene expression; (3) persistent expression of the transduced gene; (4) no viral proteins, as only the transduced gene is expressed; (5) no undesirable cytotoxic effects, and; (6) simplicity of use [leukemia cells are exposed to vector(s) only once]. In this work, we evaluated the insertion of the central polypurine tract and the central termination sequence into a SIN lentiviral vector encoding for GM-CSF and CD80, which significantly enhanced the transduction efficiency of primary leukemia cells and provided higher levels of GM-CSF and CD80 co-expression. We also demonstrate a methodology to deliver simultaneously a combination of immunomodulatory molecules (GM-CSF, CD80, IL-4, and CD40L) to activate different pathways of immune stimulation. Therefore, lentiviral vectors offer a simple, versatile, and reliable approach for engineering leukemic cells for use as cell vaccines.

Recent progress in tumour vaccine development

Immunotherapy offers an exciting opportunity to treat human cancer. Analysis of tumour-associated antigens is progressing. Assisted by animal models, such knowledge can be used to design tumour vaccines. By including adjuvants to increase immunogenicity, several tumours previously thought to be non-immunogenic are now considered targets for tumour vaccines. Newly acquired knowledge regarding dendritic cell physiology is incorporated in newly designed vaccines that are currently in Phase I and II trials. Such assessment provides the overall conclusion that tumour vaccines are safe and deserve a more prominent place in the sequel of treatments for human cancer.