Dendritic cell-based cancer vaccination: quo vadis?

Low molecular weight hyaluronan-pulsed human dendritic cells showed increased migration capacity and induced resistance to tumor chemoattraction

We have shown that ex vivo pre-conditioning of bone marrow-derived dendritic cells (DC) with low molecular weight hyaluronan (LMW HA) induces antitumor immunity against colorectal carcinoma (CRC) in mice. In the present study we investigated the effects of LMW HA priming on human-tumor-pulsed monocytes-derived dendritic cells (DC/TL) obtained from healthy donors and patients with CRC. LMW HA treatment resulted in an improved maturation state of DC/TL and an enhanced mixed leucocyte reaction activity in vivo. Importantly, pre-conditioning of DC/TL with LMW HA increased their ability to migrate and reduced their attraction to human tumor derived supernatants. These effects were associated with increased CCR7 expression levels in DC. Indeed, a significant increase in migratory response toward CCL21 was observed in LMW HA primed tumor-pulsed monocyte-derived dendritic cells (DC/TL/LMW HA) when compared to LWM HA untreated cells (DC/TL). Moreover, LMW HA priming modulated other mechanisms implicated in DC migration toward lymph nodes such as the metalloproteinase activity. Furthermore, it also resulted in a significant reduction in DC migratory capacity toward tumor supernatant and IL8 in vitro. Consistently, LMW HA dramatically enhanced in vivo DC recruitment to tumor-regional lymph nodes and reduced DC migration toward tumor tissue. This study shows that LMW HA--a poorly immunogenic molecule--represents a promising candidate to improve human DC maturation protocols in the context of DC-based vaccines development, due to its ability to enhance their immunogenic properties as well as their migratory capacity toward lymph nodes instead of tumors.

Intravital microscopic research of microembolization with degradable starch microspheres

Treatment efficacy in cancer patients using systemically applied cytostatic drugs is decreased by cytotoxic side effects, which limits the use of efficient dosages. Degradable starch microspheres (DSM) are used to apply drugs into blood vessels which supply the target organ leading to drug accumulation in the target organ by reduction of the blood flow. The present investigations show that DSM is a very effective embolization material leading to effective and enhanced accumulation of 5-FU within the liver tumor tissue of experimental induced liver cancer in rats. By using intravital microscopy, a rapid deceleration of the blood flow into the target organ is observed immediately after application of DSM. The microspheres are stepwise degraded in the direction of the systemic blood flow and are totally dissolved after 25 minutes. These stepwise processes leave the degraded material during the degradation process within the vessels leading to temporally reciprocal blood flow via some of the side-arms of the major blood vessels. By using DMS in transarterial chemoembolization (TACE), severe adverse side effects like postembolization syndrome are rarely observed when compared to other embolization materials. The complete degradation of DSM causes only a short-lasting temporary vascular occlusion, which allows a repeat application of DSM in TACE.

Autologous dendritic cell based adoptive immunotherapy of patients with colorectal cancer-A phase I-II study

Dendritic cell-based active immunotherapies of cancer patients are aimed to provoke the proliferation and differentiation of tumor-specific CD4(+) and CD8(+) T-lymphocytes towards protective effector cells. Isolation and in vitro differentiation of circulating blood monocytes has been established a reasonable platform for adoptively transferred DC-based immunotherapies. In the present study the safety and tolerability of vaccination by autologous tumor cell lysates (oncolysate)- or carcinoembriogenic antigen (CEA)-loaded DCs in patients with colorectal cancer was investigated in a phase I-II trial. The study included 12 patients with histologically confirmed colorectal cancer (Dukes B2-C stages). Six of the patients received oncolysate-pulsed, whereas the other six received recombinant CEA-loaded autologous DCs. The potential of the tumor antigen-loaded DCs to provoke the patient's immune system was studied both in vivo and in vitro. The clinical outcome of the therapy evaluated after 7 years revealed that none of the six patients treated with oncolysate-loaded DCs showed relapse of colorectal cancer, whereas three out of the six patients treated with CEA-loaded DCs died because of tumor relapse. Immunization with both the oncolysate- and the CEA-loaded autologous DCs induced measurable immune responses, which could be detected in vivo by cutaneous reactions and in vitro by lymphocyte proliferation assay. Our results show that vaccination by autologous DCs loaded with autologous oncolysates containing various tumor antigens represents a well tolerated therapeutic modality in patients with colorectal cancer without any detectable adverse effects. Demonstration of the efficacy of such therapy needs further studies with increased number of patients.

A novel and simple method for generation of human dendritic cells from unfractionated peripheral blood mononuclear cells within 2 days: its application for induction of HIV-1-reactive CD4(+) T cells in the hu-PBL SCID mice

Because dendritic cells (DCs) play a critical role in the regulation of adaptive immune responses, they have been ideal candidates for cell-based immunotherapy of cancers and infections in humans. Generally, monocyte-derived DCs (MDDCs) were generated from purified monocytes by multiple steps of time-consuming physical manipulations for an extended period cultivation. In this study, we developed a novel, simple and rapid method for the generation of type-1 helper T cell (Th1)-stimulating human DCs directly from bulk peripheral blood mononuclear cells (PBMCs). PBMCs were cultivated in the presence of 20 ng/ml of granulocyte-macrophage colony-stimulating factor, 20 ng/ml of interleukin-4 (IL-4) and 1,000 U/ml of interferon-β for 24 h followed by 24 h maturation with a cytokine cocktail containing 10 ng/ml of tumor necrosis factor-α (TNF-α), 10 ng/ml of IL-1β and 1 μg/ml of prostaglandin E2. The phenotype and biological activity of these new DCs for induction of allogeneic T cell proliferation and cytokine production were comparable to those of the MDDCs. Importantly, these new DCs pulsed with inactivated HIV-1 could generated HIV-1-reactive CD4⁺ T cell responses in humanized mice reconstituted with autologous PBMCs from HIV-1-negative donors. This simple and quick method for generation of functional DCs will be useful for future studies on DC-mediated immunotherapies.

Dendritic cell targeted liposomes-protamine-DNA complexes mediated by synthetic mannosylated cholesterol as a potential carrier for DNA vaccine

To construct mannosylated liposomes/protamine/DNA (LPD) carriers for DNA vaccine targeting to dendritic cells (DCs), a mannosylated cholesterol derivative (Man-C6-Chol) was synthesized via simple ester linkage and amide bonds. Then, the Man-C6-Chol was applied to LPD formulation as a synthetic ligand. The physicochemical properties of mannosylated LPD (Man-LPD) were first evaluated, including the size and zeta potential, morphology and the ability to protect DNA against DNase I degradation. Man-LPD showed a small size with a stable viral-like structure. In comparison to non-mannose liposomes/LPD (Man-free liposomes/LPD), mannosylated liposomes/LPD (Man-liposomes/Man-LPD) exhibited higher efficiency in both intracellular uptake (2.3-fold) and transfection (4.5-fold) in vitro. Subsequent MTT assays indicated that the LPD carriers had low toxicity on the tested cells. Afterwards, the investigation into the maturation activation on primary bone marrow-derived DCs (BMDCs) showed that both Man-LPD and Man-free LPD induced remarkable up-regulation of CD80, CD86 and CD40 on BMDCs. Inspired by these studies, we can conclude that the synthetic mannosylated LPD targeting to DCs was a potential carrier for DNA vaccine.

Differential effects of monophosphoryl lipid A and cytokine cocktail as maturation stimuli of immunogenic and tolerogenic dendritic cells for immunotherapy

Immunotherapy using monocyte-derived dendritic cells (MDDC) is increasingly being considered as alternative therapeutic approach in cancer, infectious diseases and also in autoimmunity when patients are not responsive to conventional treatments. In general, generation of MDDC from monocytes is induced in the presence of GM-CSF and IL-4, and a maturation stimulus is added to the culture to obtain mature DCs suitable for therapy. For DC maturation, different combinations of pro-inflammatory mediators and Toll-like receptor ligands have been tested, obtaining DCs that differ in their properties and the type of immune response they promote. Therefore, it is necessary to find an optimal cytokine environment for DC maturation to obtain a cellular product suitable for DC-based immunotherapeutic protocols. In this study, we have evaluated in vitro the effects of different maturation stimuli on the viability, phenotype, cytokine profile, stability and functionality of immunogenic and tolerogenic (1α,25-dihydroxyvitamin D(3)-treated) MDDC. Maturation was induced using the clinical grade TLR4-agonist: monophosphoryl lipid A (LA), compared to the traditional cytokine cocktail (CC; clinical grade TNF-α, IL-1β, PGE2) and a combination of both. Our results showed the combination of CC+LA rendered a potent immunogenic DC population that induced the production of IFN-γ and IL-17 in allogeneic co-cultures, suggesting a Th17 polarization. Moreover, these immunogenic DCs showed a high surface expression of CD83, CD86, HLA-DR and secretion of IL-12p70. When aiming to induce tolerance, using LA to generate mature TolDC did not represent a clear advantage, and the stability and the suppressive capability exhibited by CC-matured TolDC may represent the best option. Altogether, these findings demonstrate the relevance of an appropriate maturation stimulus to rationally modulate the therapeutic potential of DCs in immunotherapy.

Low molecular weight hyaluronan preconditioning of tumor-pulsed dendritic cells increases their migratory ability and induces immunity against murine colorectal carcinoma

We have recently shown that systemic administration of low molecular weight hyaluronan (LMW HA) significantly reduces colorectal carcinoma (CRC) growth in vivo. The elicited response is partially mediated by activated dendritic cells (DC). To potentiate the ability of DC loaded with whole tumor lysate (DC/TL) to induce immunity against CRC in mice, we aimed to study the effects of preconditioning DC with LMW HA for therapeutic vaccination. LMW HA improved maturation of ex vivo generated DC, increased IL-12, decreased IL-10 production, and enhanced a MLR activity in vitro. Although TNF-α showed a similar capacity to mature DC, preconditioning of DC/TL with LMW HA increased their ability to migrate in vitro toward CCL19 and CCL-21 in a CD44- and a TLR4-independent manner; this effect was superior to Poly(I:C), LPS, or TNF-α and partially associated with an increase in the expression of CCR7. Importantly, LMW HA dramatically enhanced the in vivo DC recruitment to tumor-regional lymph nodes. When these LMW HA-treated CRC tumor lysate-pulsed DC (DC/TL/LMW HA) were administered to tumor-bearing mice, a potent antitumor response was observed when compared to DC pulsed with tumor lysate alone and matured with TNF-α. Then, we showed that splenocytes isolated from animals treated with DC/TL/LMW HA presented a higher proliferative capacity, increased IFN-γ production, and secreted lower levels of the immunosuppressive IL-10. Besides, increased specific CTL response was observed in DC/TL/LMW HA-treated animals and induced long-term protection against tumor recurrence. Our data show that LMW HA is superior to other agents at inducing DC migration; therefore, LMW HA could be considered a new adjuvant candidate in the preparation of DC-based anticancer vaccines with potent immunostimulatory properties.

Dendritic cell-based vaccination of patients with advanced pancreatic carcinoma: results of a pilot study

BACKGROUND AND AIMS

Dendritic cell (DC)-based vaccination can induce antitumor T cell responses in vivo. This clinical pilot study examined feasibility and outcome of DC-based tumor vaccination for patients with advanced pancreatic adenocarcinoma.

METHODS

Tumor lysate of patients with pancreatic carcinoma was generated by repeated freeze-thaw cycles of surgically obtained tissue specimens. Patients were eligible for DC vaccination after recurrence of pancreatic carcinoma or in a primarily palliative situation. DC were generated from peripheral blood mononuclear cells (PBMC), loaded with autologous tumor lysate, stimulated with TNF-α and PGE(2) and injected intradermally. All patients received concomitant chemotherapy with gemcitabine. Disease response was the primary endpoint. Individual immunological responses to DC vaccination were analyzed by T cell-based immunoassays using pre- and post-vaccination samples of non-adherent PBMC.

RESULTS

Twelve patients received DC vaccination and concomitant chemotherapy. One patient developed a partial remission, and two patients remained in stable disease. Median survival was 10.5 months. No severe side effects were observed. Tumor-reactive T cells could be detected prior to vaccination. DC vaccination increased the frequency of tumor-reactive cells in all patients tested; however, the degree of this increase varied. To quantify the presence of tumor-reactive T cells, stimulatory indices (SI) were calculated as the ratio of proliferation-inducing capacity of lysate-loaded versus -unloaded DC. The patient with longest overall survival of 56 months had a high SI of 6.49, indicating that the presence of a pre-vaccination antitumor T cell response might be associated with prolonged survival. Five patients survived 1 year or more.

CONCLUSION

DC-based vaccination can stimulate an antitumoral T cell response in patients with advanced or recurrent pancreatic carcinoma receiving concomitant gemcitabine treatment.

What's the place of immunotherapy in malignant mesothelioma treatments?

Malignant pleural mesothelioma (MPM) is a rare malignancy of the pleura with a very poor prognosis. Treatments evaluated for malignant mesothelioma, including chemotherapy, radiotherapy and surgery are of limited efficacy. However, the fact that the tumors of some patients with MPM regress spontaneously or respond to immunotherapy suggests that the immune system may respond to MPM under some circumstances. In this respect, animal studies have demonstrated immunoreactivity of MPM to different immunotherapies. In the case of MPM, several clinical studies have demonstrated a correlation between the presence of a lymphocyte infiltrate and a better prognosis and humoral response directed against specific antigens related to tumor. Thus, MPM immunotherapy is undoubtedly a highly promising but also very challenging approach to the treatment of this disease that has slipped through the defense lines of the immune system. This article reviews past and recent developments of the clinical strategies that concern immunotherapy of mesothelioma.

WT1 peptide vaccination in a CML patient: induction of effective cytotoxic T lymphocytes and significance of peptide administration interval

Although antigen-specific immune responses including cytotoxic T cells (CTLs) against antigen peptide could be enhanced after tumor antigen peptide vaccinations, the immune responses do not necessarily result in a decrease or eradication of tumor cells in the vaccination trials. We focused on whether antigen-specific CTLs could be damaged by the repeated stimulation of antigenic peptide and whether regulatory T (Treg) cells would be increased by the administration of WT1 peptide. We administered WT1 peptide 22 times over 18 months in a CML patient who was being treated with imatinib. Although WT1 peptide administration every 2 weeks did not show any beneficial effects on the minimal residual disease (copies of bcr-abl transcripts), the transcripts remarkably decreased to the level of major molecular response after changing the administration interval of WT1 peptide from 2 to 4 weeks. An ex vivo study demonstrated that re-stimulation with WT1 peptide made WT1-specific T cells less reactive to WT1 tetramers and the impaired reactivity of CTLs lasted at least for 1 week. In addition, the cytotoxicity of the T cells was hampered by re-stimulation. Treg cells increased up to more than fivefold at the end of the WT1 administration period. The present findings suggested that the administration of the peptide every 4 weeks is superior to every 2 weeks. In addition, the findings that Treg cells increased gradually in accordance with the duration of WT1 peptide administration revealed the significance of manipulating Treg cells for establishing an efficient tumor antigen peptide vaccination.

Short-term cultured, interleukin-15 differentiated dendritic cells have potent immunostimulatory properties

Background

Optimization of the current dendritic cell (DC) culture protocol in order to promote the therapeutic efficacy of DC-based immunotherapy is warranted. Alternative differentiation of monocyte-derived DCs using granulocyte macrophage colony-stimulating factor (GM-CSF) and interleukin (IL)-15 has been propagated as an attractive strategy in that regard. The applicability of these so-called IL-15 DCs has not yet been firmly established. We therefore developed a novel pre-clinical approach for the generation of IL-15 DCs with potent immunostimulatory properties.

Methods

Human CD14⁺ monocytes were differentiated with GM-CSF and IL-15 into immature DCs. Monocyte-derived DCs, conventionally differentiated in the presence of GM-CSF and IL-4, served as control. Subsequent maturation of IL-15 DCs was induced using two clinical grade maturation protocols: (i) a classic combination of pro-inflammatory cytokines (tumor necrosis factor-α, IL-1β, IL-6, prostaglandin E₂) and (ii) a Toll-like receptor (TLR)7/8 agonist-based cocktail (R-848, interferon-γ, TNF-α and prostaglandin E₂). In addition, both short-term (2-3 days) and long-term (6-7 days) DC culture protocols were compared. The different DC populations were characterized with respect to their phenotypic profile, migratory properties, cytokine production and T cell stimulation capacity.

Results

The use of a TLR7/8 agonist-based cocktail resulted in a more optimal maturation of IL-15 DCs, as reflected by the higher phenotypic expression of CD83 and costimulatory molecules (CD70, CD80, CD86). The functional superiority of TLR7/8-activated IL-15 DCs over conventionally matured IL-15 DCs was evidenced by their (i) higher migratory potential, (ii) advantageous cytokine secretion profile (interferon-γ, IL-12p70) and (iii) superior capacity to stimulate autologous, antigen-specific T cell responses after passive peptide pulsing. Aside from a less pronounced production of bioactive IL-12p70, short-term versus long-term culture of TLR7/8-activated IL-15 DCs resulted in a migratory profile and T cell stimulation capacity that was in favour of short-term DC culture. In addition, we demonstrate that mRNA electroporation serves as an efficient antigen loading strategy of IL-15 DCs.

Conclusions

Here we show that short-term cultured and TLR7/8-activated IL-15 DCs fulfill all pre-clinical prerequisites of immunostimulatory DCs. The results of the present study might pave the way for the implementation of IL-15 DCs in immunotherapy protocols.

Evaluating maturation and genetic modification of human dendritic cells in a new polyolefin cell culture bag system

BACKGROUND

Dendritic cells (DCs) are applied worldwide in several clinical studies of immune therapy of malignancies, autoimmune diseases, and transplantations. Most legislative bodies are demanding high standards for cultivation and transduction of cells. Closed-cell cultivating systems like cell culture bags would simplify and greatly improve the ability to reach these cultivation standards. We investigated if a new polyolefin cell culture bag enables maturation and adenoviral modification of human DCs in a closed system and compare the results with standard polystyrene flasks.

STUDY DESIGN AND METHODS

Mononuclear cells were isolated from HLA-A*0201-positive blood donors by leukapheresis. A commercially available separation system (CliniMACS, Miltenyi Biotec) was used to isolate monocytes by positive selection using CD14-specific immunomagnetic beads. The essentially homogenous starting cell population was cultivated in the presence of granulocyte-macrophage-colony-stimulating factor and interleukin-4 in a closed-bag system in parallel to the standard flask cultivation system. Genetic modification was performed on Day 4. After induction of maturation on Day 5, mature DCs could be harvested and cryopreserved on Day 7. During the cultivation period comparative quality control was performed using flow cytometry, gene expression profiling, and functional assays.

RESULTS

Both flasks and bags generated mature genetically modified DCs in similar yields. Surface membrane markers, expression profiles, and functional testing results were comparable. The use of a closed-bag system facilitated clinical applicability of genetically modified DCs.

CONCLUSIONS

The polyolefin bag-based culture system yields DCs qualitatively and quantitatively comparable to the standard flask preparation. All steps including cryopreservation can be performed in a closed system facilitating standardized, safe, and reproducible preparation of therapeutic cells.