Leukemic cell products down-regulate human dendritic cell differentiation

Modulation of cytokine production by monocytes and developing-dendritic cells under the influence of leukemia and lymphoma cell products

Cytokines and other soluble factors released by tumor cells play an important role in modulating immune cells to favor tumor development. Monocyte differentiation into macrophages or dendritic cells (DCs) with specific phenotypes is deeply affected by tumor signals and understanding this context is paramount to prevent and propose new therapeutic possibilities. Hence, we developed a study to better describe the modulatory effects of leukemia and lymphoma cell products on human monocytes and monocyte-derived DCs secretion of cytokines such as interleukin (IL)-1β, tumor necrosis factor-α (TNF-α), IL-6, and IL-12. Except with the promyelocytic leukemia cell supernatants (HL-60), the other two tumor supernatants (chronic myeloid leukemia, K562 and Burkitt lymphoma, DAUDI) increased both TNF-α and IL-1β production by monocytes and monocytes undergoing differentiation. This effect was neither explained by alterations of cell number in culture nor by the high amount of vascular endothelial growth factor (VEGF) present in the tumor supernatants. Moreover, all supernatants used were able to induce drastic reduction of IL-12 secretion by cells induced to activation, suggesting a negative interference with Th1 antitumoral responses that should be a huge advantage for tumor progression.

Soluble factors derived from neuroblastoma cell lines suppress dendritic cell differentiation and activation

Dendritic cells (DC) play a key role in the initiation of both antitumor immunity and immunological tolerance. It has been demonstrated that exposure to soluble factors produced by tumor cells modulates DC functions and induces tolerogenic DC differentiation. In this study, we investigated the effects of neuroblastoma cell line-derived soluble factors on DC differentiation. Monocytes isolated from healthy volunteers were incubated with interleukin (IL)-4 and granulocyte-macrophage colony-stimulating factor in the presence of culture supernatants from neuroblastoma cell lines. The culture supernatants from neuroblastoma cell lines, such as NLF and GOTO, partially blocked both downregulation of CD14 and upregulation of CD1a, and dramatically decreased IL-12 and tumor necrosis factor (TNF)-α production from mature DC, while no effect of SH-SY5Y cell supernatant was noted. In addition, IL-6 and IL-10 production from monocytes was increased by the supernatants of NLF and GOTO cells at 24 hours after incubation. Furthermore, we evaluated DC functions through stimulation of invariant natural killer T (iNKT) cells. α-Galactosylceramide-pulsed DC co-cultured with supernatants of NLF cells were unable to sufficiently stimulate iNKT cells. The decreased ability of iNKT cells to produce interferon (IFN)-γ after stimulation with neuroblastoma cell line supernatant-cultured DC was reversed by addition of IL-12. CD40 expression and IL-12 production in NLF-sup-treated DC were increased by addition of exogenous IFN-γ. These results indicate that tolerogenic DC are induced in the neuroblastoma tumor microenvironment and attenuate the antitumor effects of iNKT cells. Interactions between iNKT cells and αGalCer-pulsed DC have the potential to restore the immunosuppression of tolerogenic DC through IFN-γ production.

Sensitivity of Dendritic Cells to Microenvironment Signals

Dendritic cells are antigen-presenting cells capable of either activating the immune response or inducing and maintaining immune tolerance. They do this by integrating stimuli from the environment and changing their functional status as a result of plasticity. The modifications suffered by these cells have consequences in the way the organism may respond. In the present work two opposing situations known to affect dendritic cells are analyzed: tumor growth, leading to a microenvironment that favors the induction of a tolerogenic profile, and organ transplantation, which leads to a proinflammatory profile. Lessons learned from these situations may help to understand the mechanisms of modulation resulting not only from the above circumstances, but also from other pathologies.

The influence of Ouabain on human dendritic cells maturation

Although known as a Na,K-ATPase inhibitor, several other cellular and systemic actions have been ascribed to the steroid Ouabain (Oua). Particularly in the immune system, our group showed that Ouabain acts on decreasing lymphocyte proliferation, synergizing with glucocorticoids in spontaneous thymocyte apoptosis, and also lessening CD14 expression and blocking CD16 upregulation on human monocytes. However, Ouabain effects on dendritic cells (DCs) were not explored so far. Considering the peculiar plasticity and the importance of DCs in immune responses, the aim of our study was to investigate DC maturation under Ouabain influence. To generate immature DCs, human monocytes were cultured with IL-4 and GM-CSF (5 days). To investigate Ouabain role on DC activation, DCs were stimulated with TNF-α for 48 h in the presence or absence of Ouabain. TNF-induced CD83 expression and IL-12 production were abolished in DCs incubated with 100 nM Ouabain, though DC functional capacity concerning lymphocyte activation remained unaltered. Nevertheless, TNF-α-induced antigen capture downregulation, another maturation marker, occurred even in the presence of Ouabain. Besides, Ouabain increased HLA-DR and CD86 expression, whereas CD80 expression was maintained. Collectively, our results suggest that DCs respond to Ouabain maturating into a distinct category, possibly contributing to the balance between immunity and tolerance.

Vaccination with autologous dendritic cells loaded with autologous tumor lysate or homogenate combined with immunomodulating radiotherapy and/or preleukapheresis IFN-α in patients with metastatic melanoma: a randomised "proof-of-principle" phase II study

BACKGROUND

Vaccination with dendritic cells (DC) loaded with tumor antigens elicits tumor-specific immune responses capable of killing cancer cells without inducing meaningful side-effects. Patients with advanced melanoma enrolled onto our phase II clinical studies have been treated with autologous DC loaded with autologous tumor lysate/homogenate matured with a cytokine cocktail, showing a clinical benefit (PR + SD) in 55.5% of evaluable cases to date. The beneficial effects of the vaccine were mainly restricted to patients who developed vaccine-specific immune response after treatment. However, immunological responses were only induced in about two-thirds of patients, and treatments aimed at improving immunological responsiveness to the vaccine are needed.

METHODS/DESIGN

This is a phase II, "proof-of-principle", randomized, open-label trial of vaccination with autologous DC loaded with tumor lysate or homogenate in metastatic melanoma patients combined with immunomodulating RT and/or preleukapheresis IFN-α. All patients will receive four bi-weekly doses of the vaccine during the induction phase and monthly doses thereafter for up to a maximum of 14 vaccinations or until confirmed progression. Patients will be randomized to receive:(1.) three daily doses of 8 Gy up to 12 Gy radiotherapy delivered to one non-index metastatic field between vaccine doses 1 and 2 and, optionally, between doses 7 and 8, using IMRT-IMAT techniques;(2.) daily 3 MU subcutaneous IFN-α for 7 days before leukapheresis;(3.) both 1 and 2;(4.) neither 1 nor 2.At least six patients eligible for treatment will be enrolled per arm. Daily 3 MU IL-2 will be administered subcutaneously for 5 days starting from the second day after each vaccine dose. Serial DTH testing and blood sampling to evaluate treatment-induced immune response will be performed. Objective response will be evaluated according to immune-related response criteria (irRC).

DISCUSSION

Based upon the emerging role of radiotherapy as an immunologic modifier, we designed a randomized phase II trial adding radiotherapy and/or preleukapheresis IFN-α to our DC vaccine in metastatic melanoma patients. Our aim was to find the best combination of complementary interventions to enhance anti-tumor response induced by DC vaccination, which could ultimately lead to better survival and milder toxicity.

Induction of suppressive phenotype in monocyte-derived dendritic cells by leukemic cell products and IL-1β

Professional antigen-presenting cells, dendritic cells (DCs) play an important role in controlling tumors. It is known that solid tumor cell products inhibit DC differentiation. Recently a similar effect produced by leukemic cell products has been demonstrated. In this case, leukemic cell products induced the secretion of IL-1β by monocytes undergoing differentiation. The aim of the present work was to characterize and to compare the development of monocyte-derived DCs under the influence of leukemic cell products (K562 supernatant) or exogenous IL-1β. It became clear that leukemic cell products and IL-1β differentially modulate some of the parameters studied on monocytes stimulated to differentiate into DCs. In the presence of K562 supernatant, the expression of the macrophage markers CD16 and CD68 were higher than in immature DCs control. Contrasting with IL-1β, leukemic cell products possibly favor the development of cells with macrophage markers. In addition, CD80 and CD83 expressions were also higher in the presence of tumor supernatant whereas HLA-DR was lower. In the presence of IL-1β, only CD80 was increased. Furthermore, it was observed that when monocytes were induced to differentiate into DCs in the presence of tumor supernatant and then activated, they expressed less CD80 and CD83 than activated DCs control. A reduced expression of CD83 following activation was also seen in cells differentiated with IL-1β. TGF-β and VEGF were found in the tumor supernatants. Moreover, the exposure to tumor supernatant or IL-1β stimulated IL-10 production while decreased IL-12 production by activated DCs. Finally, these results suggest that the addition of products released by leukemic cells or, more discreetly, the addition of IL-1β affects DC differentiation, inducing a suppressive phenotype.

Monitoring dendritic cell and cytokine biomarkers during remission prior to relapse in patients with FLT3-ITD acute myeloid leukemia

Relapse occurs frequently after treatment of acute myeloid leukemia (AML) patients with the FMS-like tyrosine kinase 3-internal tandem duplication (ITD) mutation. The availability of immunologic biomarkers to predict patients at high risk could allow clinicians to accelerate alternative treatments such as stem cell transplantation, immunotherapy, or novel drugs. We have previously reported that first diagnostic (FD) ITD(+) AML showed immunophenotypic and functional characteristics of arrested dendritic cell (DC) precursors. In this study, we show that the high frequency of precursor DCs in 16 FD ITD(+) AML samples (Lin(-)/HLA-DR(+)/CD11c(+)/CD123(+)) was associated with a lack of terminal DCs (myeloid DCs: BDCA-1(+) or BDCA-3(+); plasmacytoid DC: BDCA-2(+)). We further evaluated prospectively the peripheral blood complete remission (CR) samples obtained from 11 ITD(+) AML patients after chemotherapy regarding the frequency of DCs and their pattern of cytokine production. Whereas the aberrant frequencies of precursor and terminal plasmacytoid DCs resolved during remission, the myeloid DC compartment did not fully recover. For an available cohort of patients (n = 4) who could be monitored over a period of >15 months after FD, we identified IL-10, TNF-α, IL-6, and IL-1β as cytokines produced by the CR samples at high levels a few months prior to relapse. Cell-free supernatant of an FD ITD(+) AML sample stimulated monocytes obtained from two healthy donors to secrete IL-10, TNF-α, IL-6, and IL-1β. Thus, we hypothesize that ITD(+) AML minimal residual disease can act directly as dysfunctional antigen-presenting cells or indirectly by production of factors that convert monocytes into myeloid-derived suppressor cells secreting cytokines that promote immune evasion. Monitoring these immunologic biomarkers could improve prediction of relapse.

HTLV-I-infected breast milk macrophages inhibit monocyte differentiation to dendritic cells

Human T-cell leukemia virus type I (HTLV-I), a causative agent of adult T-cell leukemia (ATL), is transmitted from mother to child, predominantly by breastfeeding. Oral HTLV-I infection and infection early in life are associated with a subsequent risk of ATL. Although the pathogenic mechanisms of ATL remain largely unknown, the host immune system seems to play an important role in HTLV-I pathogenesis. Previous studies have shown that monocytes from ATL patients had reduced capacity for dendritic cell (DC) differentiation. Therefore, we performed the present study to clarify the mechanisms responsible for the impairment of DC differentiation using HTLV-I-infected breast milk macrophages (HTLV-BrMMø). We found that when CD14⁺ monocytes were cultured with GM-CSF and IL-4 in the presence of HTLV-BrMMø, they altered the surface phenotype of immature DCs and the stimulatory capacity of T-cell proliferation. The presence of HTLV-BrMMø significantly blocked the increased expression of CD1a, CD1b, CD11b, DC-SIGN, and HLA-DR; however, increased expression of CD1d and CD86 was observed. These effects could be partially replicated by incubation with culture supernatants from HTLV-BrMMø. The impairment of monocyte differentiation might be not due to HTLV-I infection of monocytes, but might be due to unknown soluble factors. Since other HTLV-I-infected cells exhibited similar inhibitory effects on monocyte differentiation to DCs, we speculated that HTLV-I infection might cause the production of some inhibitory cytokines in infected cells. Identifying the factors responsible for the impairment of monocyte differentiation to DCs may be helpful to understand HTLV-I pathogenesis.

Generation of functional monocyte-derived fast dendritic cells suitable for clinical application in the absence of interleukin-6

To develop dendritic cells (DCs)-based immunotherapy for cancer patients, it is necessary to have a standardized, reproducible, fast, and easy to use protocol for in vitro generation of fully functional DCs. Recently, a new strategy was described for differentiation and maturation of human monocyte (Mo)-derived fast-DCs with full T cell stimulatory capacity within only 48-72 h of in vitro culture. Interleukin (IL)-6 plus tumour necrosis factor (TNF)-α, IL-1β, and prostaglandin (PG)-E(2) were used in this strategy to induce maturation of the generated DCs. The present study further modifies this strategy by excluding IL-6 from the cytokines cocktail used for DCs maturation. The results showed that maturation of fast-DCs without IL-6 did not significantly alter the morphology, phenotype and the yield of mature DCs (P > 0.05, compared with those generated with IL-6). Moreover, fast-DCs generated without IL-6 are functional antigen presenting cells, have the ability to induce tetanus toxoid-specific autologous T cell proliferation, and are suitable for gene delivery through adenoviral vector transduction as those generated with IL-6 (P > 0.05). In conclusion, the present study proves that fully mature and functional Mo-derived fast-DCs can be generated in vitro without adding IL-6, which not only reduces the number of required recombinant cytokines, but may also resemble DCs development in vivo more closely.

Chronic myeloid leukemia lysate-loaded dendritic cells induce T-cell responses towards leukemia progenitor cells

Treatment of chronic myeloid leukemia with tyrosine kinase inhibitors, such as imatinib mesylate, dasatinib and nilotinib, results in high rates of cytogenetic and molecular responses. However, in many patients, minimal residual disease is detected by molecular techniques. Since chronic myeloid leukemia cells are particularly good targets for immune surveillance mechanisms, we explored active specific immunotherapy using leukemia lysate-loaded dendritic cells in vitro. Our data show the potency of dendritic cell-based vaccination strategies for the induction of T cell-mediated responses to eradicate minimal residual disease.

Exogenous control of the expression of Group I CD1 molecules competent for presentation of microbial nonpeptide antigens to human T lymphocytes

Group I CD1 (CD1a, CD1b, and CD1c) glycoproteins expressed on immature and mature dendritic cells present nonpeptide antigens (i.e., lipid or glycolipid molecules mainly of microbial origin) to T cells. Cytotoxic CD1-restricted T lymphocytes recognizing mycobacterial lipid antigens were found in tuberculosis patients. However, thanks to a complex interplay between mycobacteria and CD1 system, M. tuberculosis possesses a successful tactic based, at least in part, on CD1 downregulation to evade CD1-dependent immunity. On the ground of these findings, it is reasonable to hypothesize that modulation of CD1 protein expression by chemical, biological, or infectious agents could influence host's immune reactivity against M. tuberculosis-associated lipids, possibly affecting antitubercular resistance. This scenario prompted us to perform a detailed analysis of the literature concerning the effect of external agents on Group I CD1 expression in order to obtain valuable information on the possible strategies to be adopted for driving properly CD1-dependent immune functions in human pathology and in particular, in human tuberculosis.