Lack of dendritic cell mobilization into the peripheral blood of cancer patients following standard- or high-dose chemotherapy plus granulocyte-colony stimulating factor

Nanomaterials-Based Novel Immune Strategies in Clinical Translation for Cancer Therapy

Immunotherapy shows a lot of promise for addressing the problems with traditional cancer treatments. Researchers and clinicians are working to create innovative immunological techniques for cancer detection and treatment that are more selective and have lower toxicity. An emerging field in cancer therapy, immunomodulation offers patients an alternate approach to treating cancer. These therapies use the host's natural defensive systems to identify and remove malignant cells in a targeted manner. Cancer treatment is now undergoing somewhat of a revolution due to recent developments in nanotechnology. Diverse nanomaterials (NMs) have been employed to overcome the limits of conventional anti-cancer treatments such as cytotoxic, surgery, radiation, and chemotherapy. Aside from that, NMs could interact with live cells and influence immune responses. In contrast, unexpected adverse effects such as necrosis, hypersensitivity, and inflammation might result from the immune system (IS)'s interaction with NMs. Therefore, to ensure the efficacy of immunomodulatory nanomaterials, it is essential to have a comprehensive understanding of the intricate interplay that exists between the IS and NMs. This review intends to present an overview of the current achievements, challenges, and improvements in using immunomodulatory nanomaterials (iNMs) for cancer therapy, with an emphasis on elucidating the mechanisms involved in the interaction between NMs and the immune system of the host.

Nanomaterials-Mediated Immunomodulation for Cancer Therapeutics

Immunotherapy holds great promise in overcoming the limitations of conventional regimens for cancer therapeutics. There is growing interest among researchers and clinicians to develop novel immune-strategies for cancer diagnosis and treatment with better specificity and lesser adversity. Immunomodulation-based cancer therapies are rapidly emerging as an alternative approach that employs the host’s own defense mechanisms to recognize and selectively eliminate cancerous cells. Recent advances in nanotechnology have pioneered a revolution in the field of cancer therapy. Several nanomaterials (NMs) have been utilized to surmount the challenges of conventional anti-cancer treatments like cytotoxic chemotherapy, radiation, and surgery. NMs offer a plethora of exceptional features such as a large surface area to volume ratio, effective loading, and controlled release of active drugs, tunable dimensions, and high stability. Moreover, they also possess the inherent property of interacting with living cells and altering the immune responses. However, the interaction between NMs and the immune system can give rise to unanticipated adverse reactions such as inflammation, necrosis, and hypersensitivity. Therefore, to ensure a successful and safe clinical application of immunomodulatory nanomaterials, it is imperative to acquire in-depth knowledge and a clear understanding of the complex nature of the interactions between NMs and the immune system. This review is aimed at providing an overview of the recent developments, achievements, and challenges in the application of immunomodulatory nanomaterials (iNMs) for cancer therapeutics with a focus on elucidating the mechanisms involved in the interplay between NMs and the host’s immune system.

The Potential of Combining Tubulin-Targeting Anticancer Therapeutics and Immune Therapy

Cancer immune therapy has recently shown tremendous promise to combat many different cancers. The microtubule is a well-defined and very effective cancer therapeutic target. Interestingly, several lines of evidence now suggest that microtubules are intimately connected to the body’s immune responses. This raises the possibility that the combination of microtubule inhibitors and immune therapy can be a highly effective option for cancer treatments. However, our understanding on this potentially important aspect is still very limited, due in part to the multifaceted nature of microtubule functions. Microtubules are not only involved in maintaining cell morphology, but also a variety of cellular processes, including the movement of secretory vesicles and organelles, intracellular macromolecular assembly, signaling pathways, and cell division. Microtubule inhibitors may be subdivided into two classes: Anti-depolymerization agents such as the taxane family, and anti-polymerization agents such as colchicine and vinka alkaloids. These two different classes may have different effects on immune cell subtypes. Anti-depolymerization agents can not only induce NK cells, but also appear to inhibit T regulatory (Treg) cells. However, different inhibitors may have different functions even among the same class. For example, the doxetaxel anti-depolymerization agent up-regulates cytotoxic T cells, while paclitaxel down-regulates them. Certain anti-polymerization agents such as colchicine appear to down-regulate most immune cell types, while inducing dendritic cell maturation and increasing M1 macrophage population. In contrast, the vinblastine anti-polymerization agent activates many of these cell types, albeit down-regulating Treg cells. In this review, we focus on the various effects of tubulin inhibitors on the activities of the body’s immune system, in the hope of paving the way to develop an effective cancer therapy by combining tubulin-targeting anticancer agents and immune therapy.

Effect of administration timing of postchemotherapy granulocyte colony-stimulating factor on host-immune cell recovery and CD8+ T-cell response

Granulocyte colony-stimulating factor (G-CSF), a hematopoietic growth factor, is a standard supportive therapy given during cancer treatment. It induces acceleration in neutrophil recovery through stimulation of mobilization of hematopoietic progenitors. Given that the latter is also induced by chemotherapy itself, the timing of administration of G-CSF postchemotherapy might impact the resultant overall effects. The present study aimed to determine the optimal timing of G-CSF postchemotherapy to exert its optimal effects on the immune cell recovery and its impact on antigen-specific CD8⁺ T-cell response. B6 mice were treated once with cyclophosphamide (4 mg/mouse; CTX) and then daily with G-CSF (5 g/mouse) from Days 1-5, 2-5 or 5-9 post-CTX treatment. The total numbers of various immune cell types were analyzed on Days 7, 9 and 12 post-CTX treatment. To evaluate effects on CD8⁺ T-cell response, a pmel-1 transgenic mouse model was used in combination with prime boost peptide vaccination therapy. The total number of white blood cells (WBC), neutrophils, monocytes, lymphocytes, granulocytes and dendritic cells (DC) were significantly increased after G-CSF treatment in particular when G-CSF was administered from Days 2-5 post-CTX treatment. Application of this timing of G-CSF and CTX treatment after adoptive transfer of T-cells followed by prime-boost vaccination with antigenic peptide did not block the expansion of the donor pmel-1 CD8⁺ T-cells. In conclusion, adjusting the timing of treatment with G-CSF postchemotherapy can optimize its promoting effects on recovery of myeloid cells without altering the associated antigen-specific immunity.

Metronomic cyclophosphamide schedule-dependence of innate immune cell recruitment and tumor regression in an implanted glioma model

Metronomic cyclophosphamide (CPA) treatment activates robust innate anti-tumor immunity and induces major regression of large, implanted brain tumor xenografts when administered on an intermittent, every 6-day schedule, but not on a daily low-dose or a maximum-tolerated dose CPA schedule. Here, we used an implanted GL261 glioma model to compare five intermittent metronomic CPA schedules to elucidate the kinetics and schedule dependence of innate immune cell recruitment and tumor regression. Tumor-recruited natural killer cells induced by two every 6-day treatment cycles were significantly ablated 1 day after a third CPA treatment, but largely recovered several days later. Natural killer and other tumor-infiltrating innate immune cells peaked 12 days after the last CPA treatment on the every 6-day schedule, suggesting that drug-free intervals longer than 6 days may show increased efficacy. Metronomic CPA treatments spaced 9 or 12 days apart, or on an alternating 6 and 9 day schedule, induced extensive tumor regression, similar to the 6-day schedule; however, the tumor-infiltrating natural killer cell responses were not sustained, leading to rapid resumption of tumor growth after day 24, despite ongoing metronomic CPA treatment. Increasing the CPA dose prolonged the period of tumor regression on the every 9-day schedule, but natural killer cell activation was markedly decreased. Thus, while several intermittent metronomic CPA treatment schedules can activate innate immune cell recruitment leading to major tumor regression, sustained immune and anti-tumor responses are only achieved on the 6-day schedule. However, even with this schedule, some tumors eventually relapse, indicating a need for further improvements in this immunogenic metronomic therapy.

Immune-based mechanisms of cytotoxic chemotherapy: implications for the design of novel and rationale-based combined treatments against cancer

Conventional anticancer chemotherapy has been historically thought to act through direct killing of tumor cells. This concept stems from the fact that cytotoxic drugs interfere with DNA synthesis and replication. Accumulating evidence, however, indicates that the antitumor activities of chemotherapy also rely on several off-target effects, especially directed to the host immune system, that cooperate for successful tumor eradication. Chemotherapeutic agents stimulate both the innate and adaptive arms of the immune system through several modalities: (i) by promoting specific rearrangements on dying tumor cells, which render them visible to the immune system; (ii) by influencing the homeostasis of the hematopoietic compartment through transient lymphodepletion followed by rebound replenishment of immune cell pools; (iii) by subverting tumor-induced immunosuppressive mechanisms and (iv) by exerting direct or indirect stimulatory effects on immune effectors. Among the indirect ways of immune cell stimulation, some cytotoxic drugs have been shown to induce an immunogenic type of cell death in tumor cells, resulting in the emission of specific signals that trigger phagocytosis of cell debris and promote the maturation of dendritic cells, ultimately resulting in the induction of potent antitumor responses. Here, we provide an extensive overview of the multiple immune-based mechanisms exploited by the most commonly employed cytotoxic drugs, with the final aim of identifying prerequisites for optimal combination with immunotherapy strategies for the development of more effective treatments against cancer.

Immunomodulatory effects of low dose chemotherapy and perspectives of its combination with immunotherapy

Given that cancer is one of the main causes of death worldwide, many efforts have been directed toward discovering new treatments and approaches to cure or control this group of diseases. Chemotherapy is the main treatment for cancer; however, a conventional schedule based on maximum tolerated dose (MTD) shows several side effects and frequently allows the development of drug resistance. On the other side, low dose chemotherapy involves antiangiogenic and immunomodulatory processes that help host to fight against tumor cells, with lower grade of side effects. In this review, we present evidence that metronomic chemotherapy, based on the frequent administration of low or intermediate doses of chemotherapeutics, can be better than or as efficient as MTD. Finally, we present some data indicating that noncytotoxic concentrations of antineoplastic agents are able to both up-regulate the immune system and increase the susceptibility of tumor cells to cytotoxic T lymphocytes. Taken together, data from the literature provides us with sufficient evidence that low concentrations of selected chemotherapeutic agents, rather than conventional high doses, should be evaluated in combination with immunotherapy.

A randomized study comparing chemotherapy followed by G-CSF alone or in combination with GM-CSF for mobilization of peripheral blood stem cells in patients with non-Hodgkin's lymphomas

OBJECTIVE

Granulocyte colony-stimulating factor (G-CSF) and granulocyte-macrophage colony stimulating factor (GM-CSF) are the two most commonly used cytokines for mobilization of stem cells in patients undergoing high dose chemotherapy with stem cell support. Both cytokines increase the peripheral blood white blood cell count and the stem cell count but there are other differences in the stem cell products mobilized by G-CSF versus those mobilized with GM-CSF. Generally higher numbers of dendritic cells are mobilized with GM-CSF than by G-CSF. The primary objective of this randomized study was to evaluate the safety and efficacy of chemotherapy plus G-CSF versus chemotherapy plus G-CSF and GM-CSF in patients with B-cell non-Hodgkin's lymphoma (NHL) who were undergoing chemo-mobilization. Secondary objectives were to determine the expression of various dendritic cell subsets in the two groups and to determine the incidence of disease progression or relapse at 12 months.

METHODS

We prospectively evaluated 84 patients with relapsed NHL who were candidates for high dose therapy (HDT). All patients underwent chemo-mobilization using ifosfamide, etoposide, and rituximab. All patients were randomized in an adaptive manner to receive either G-CSF or G-CSF plus GM-CSF (G+GM) starting 24 hours after completion of chemotherapy and continuing until completion of apheresis. The stem cell yield/kg, the number of apheresis procedures needed in the two groups, and the toxicity were recorded. We also enumerated dendritic cell subsets, myeloid DCs (mDC) and plasmacytoid DCs (pDC), in apheresis products and in peripheral blood (PB) samples collected pre-chemotherapy. The data were expressed as a percentage of peripheral blood mononuclear cells.

RESULTS

A total of 84 patients were treated. Forty-three patients received G-CSF and 41 received G+GM. Both regimens were well tolerated. The median CD34+ cell dose collected was similar in the two groups. A total of 54 (G-CSF N = 25 and G+GM N = 29) paired samples from baseline and post-apheresis were available for analysis of dendritic cell subsets. There was no significant difference in the percentages of mDC subsets between baseline and post-apheresis collected with G-CSF or G+GM mobilization. However, there was a significant increase in the percentage of pDC subsets in the G-CSF alone when compared to the G+GM arm (P = 0.002). Furthermore, the ratio of mDC and pDC was significantly lower after mobilization with G-CSF versus G+GM (P = 0.029).

CONCLUSION

Addition of GM-CSF to G-CSF to the mobilization regimen resulted in lower percentages of pDC in the apheresis products when compared to those with G-CSF alone. This shifts the mDC/pDC ratio in the apheresis grafts in favor of mDC in the combination arm. However, these differences did not seem to impact the clinical outcomes in the two groups. (ClinicalTrials.gov Identifier: NCT00499343).

Differential effects of Paclitaxel on dendritic cell function

BACKGROUND

The potential utility of dendritic cells (DC) as cancer vaccines has been established in early trials in human cancers. The concomitant administration of cytotoxic agents and DC vaccines has been previously avoided due to potential immune suppression by chemotherapeutics. Recent studies show that common chemotherapy agents positively influence adaptive and innate anti-tumour immune responses.

RESULTS

We investigated the effects of paclitaxel on human DC biology in vitro. DCs appear to sustain a significant level of resistance to paclitaxel and maintain normal viability at concentrations of up to 100 micromol. In some cases this resistance against paclitaxel is significantly better than the level seen in tumour cell lines. Paclitaxel exposure led to a dose dependent increase in HLA class II expression equivalent to exposure to lipopolysaccharide (LPS), and a corresponding increase in proliferation of allogeneic T cells at the clinically relevant doses of paclitaxel. Increase in HLA-Class II expression induced by paclitaxel was not blocked by anti TLR-4 antibody. However, paclitaxel exposure reduced the endocytic capacity of DC but reduced the expression of key pro-inflammatory cytokines such as IL-12 and TNFalpha. Key morphological changes occurred when immature DC were cultured with 100 micromol paclitaxel. They became small rounded cells with stable microtubules, whereas there were little effects on LPS-matured DC.

CONCLUSIONS

The effect of paclitaxel on human monocyte derived DC is complex, but in the clinical context of patients receiving preloaded and matured DC vaccines, its immunostimulatory potential and resistance to direct cytotoxicity by paclitaxel would indicate potential advantages to co-administration with vaccines.

Cyclophosphamide induces dynamic alterations in the host microenvironments resulting in a Flt3 ligand-dependent expansion of dendritic cells

Preconditioning a recipient host with lymphodepletion can markedly augment adoptive T cell therapy. However, the precise mechanisms involved are poorly understood. In a recent study, we observed a significant increase in the circulating levels of dendritic cells (DCs; CD11c(+)CD11b(+)) during the recovery from cyclophosphamide (CTX)-induced lymphodepletion. Herein, we demonstrate that the CTX-induced DC expansion was not altered by adjuvant chemotherapy or tumor burden but was augmented by coadministration of granulocyte-colony stimulating factor. Although the increase in the number of DCs was preceded by a systemic expansion of a population expressing the phenotype of myeloid-derived suppressor cells (Gr-1(+)CD11b(+)), depletion of these Gr-1(+) cells had no effect on the noted expansion. Moreover, when Gr-1(high)CD11b(high) cells were sorted from CTX-treated mice and adoptively transferred into control or CTX-treated recipients, they did not differentiate into DCs. Post-CTX expansion of DCs was associated with proliferation of DCs in bone marrow (BM) during the lymphopenic phase and in the blood and spleen during the recovery phase. Furthermore, adoptive transfer of BM cells from CTX-treated mice produced equal numbers of DCs in the blood of either CTX-treated or untreated recipients. CTX induced a dynamic surge in the expression of growth factors and chemokines in BM, where CCR2 and Flt3 signaling pathways were critical for DC expansion. In sum, our data suggest that CTX induces proliferation of DCs in BM prior to their expansion in the periphery. Targeting DCs at these phases would significantly improve their contribution to the clinical application of lymphodepletion to adoptive immunotherapy.

Comparison of unmobilized and mobilized graft characteristics and the implications of cell subsets on autologous and allogeneic transplantation outcomes

Autologous and allogeneic hematopoietic stem cell transplantation (HSCT) are considered the standard of care for many malignancies, including lymphoma, myeloma, and some leukemias. In many cases, mobilized peripheral blood has become the preferred source of hematopoietic stem cells. The efficacy of different mobilization regimens and transplantation outcomes based on cell doses has been well studied; however, the characteristics of the stem cell graft may be of equal importance with respect to patient outcomes following autologous or allogeneic HSCT. This review summarizes available preclinical and clinical data for bone marrow and mobilized peripheral blood HSCT characteristics, defined as the cell types found in the graft as well as their gene expression profiles. It also explores how graft characteristics can affect bone marrow homing, engraftment, immune reconstitution, and other posttransplantation outcomes in both the allogeneic and autologous HSCT settings.

Improved mobilization of peripheral blood CD34+ cells and dendritic cells by AMD3100 plus granulocyte-colony-stimulating factor in non-Hodgkin's lymphoma patients

AMD3100 is a drug capable of mobilizing peripheral blood stem cells (PBSCs) in donors and in cancer patients as a single agent or in combination with granulocyte-colony-stimulating factor (G-CSF). We initiated a phase II study of 11 refractory or relapsed non-Hodgkin's lymphoma (NHL) patients, receiving 16 microg/kg daily of G-CSF for 4 days followed by 240 microg/kg of AMD3100 given subcutaneously on a new schedule of 9-10 h before apheresis collection on day 5. Our aims were to assess the effect of AMD3100 on the mobilization of CD34+ cells, dendritic cells (DCs) and lymphoma cells. Administration of G-CSF and AMD3100 were continued daily until >or=2 x 10(6) CD34+ cells/kg were collected. Adequate collection of the target of CD34+ cells was achieved in all but 1 patient within 2 days, and 10/11 patients were transplanted within 2 months. All transplanted patients engrafted with a mean of 10 and 12 days for neutrophils and platelets, respectively. Addition of AMD3100 to G-CSF resulted with >2.5-fold increase in CD34+ cells/microl (p = 0.0001) and in a >2-fold increase in pDC1 and pDC2 cells/microl (p = 0.003). Adverse events related to AMD3100 were minimal. AMD3100 was generally safe and improved PBSC and DC cell mobilization with no apparent contamination of lymphoma cells.

Association of IL-12+ DC with High CD3+CD4-DR+ Lymphocyte Counts in Long-term HIV-infected Hemophilia Patients With Clinically Stable Disease

We investigated dendritic cell (DC) subsets as well as cellular and humoral immune parameters in long-term HIV-infected hemophilia patients with clinically stable disease. DC subsets were determined by their function to produce either IL-10 or IL-12. CD11c(+)CD83(+)CD40(+)IL-10(+) and CD11c(+)CD83(+)CD40(+)IL-12(+) DC were studied in freshly obtained blood samples of 28 HIV(+) and 15 HIV(-) patients and 39 healthy controls using four-color flow cytometry, and were analyzed in relation to blood lymphocyte subpopulation counts, proportions of IgG-coated CD4(+) blood lymphocytes, neopterin, and HIV-1 viral load in the plasma, and in vitro responses of patient lymphocytes to mitogens. Proportions and ratios of IL-10(+) DC and IL-12(+) DC were similar in HIV(+) and HIV(-) patients and healthy controls. Whereas IL-12(+) DC in HIV(+) patients were associated with high CD3(+)CD4(-)DR(+) lymphocyte counts, IL-10(+) DC were associated with the proportion of IgG-coated CD4(+) blood lymphocytes. These data suggest that long-term HIV-infected hemophilia patients with clinically stable disease have normal levels of functional IL-10(+) DC and IL-12(+) DC that might be involved in halting the progression of disease.

Dendritic cell-based immunotherapy

Dendritic cells (DCs) play a crucial role in the induction of antigen-specific T-cell responses, and therefore their use for the active immunotherapy of malignancies has been studied with considerable interest. More than a decade has passed since the publication of the first clinical data of DC-based vaccines, and through this and subsequent studies, a number of important developmental insights have been gleaned. These include the ideal source and type of DCs, the discovery of novel antigens and methods of loading DCs, the role of DC maturation, and the most efficient route of immunization. The generation of immune responses against tumor antigens after DC immunization has been demonstrated, and favorable clinical responses have been reported in some patients; however, it is difficult to pool the results as a whole, and thus the body of data remains inconclusive, in part because of varying DC preparation and vaccination protocols, the use of different forms of antigens, and, most importantly, a lack of rigorous criteria for defining clinical responses. As such, the standardization of clinical and immunologic criteria utilized, as well as DC preparations employed, will allow for the comparison of results across multiple clinical studies and is required in order for future trials to measure the true value and role of this treatment modality. In addition, issues regarding the optimal dose and clinical setting for the application of DC vaccines remain to be resolved, and recent clinical studies have been designed to begin to address these questions.

Granulocyte Colony-Stimulating Factor Mobilizes More Dendritic Cell Subsets Than Granulocyte-Macrophage Colony-Stimulating Factor with No Polarization of Dendritic Cell Subsets in Normal Donors

Dendritic cells (DCs) are effective antigen-presenting cells. We hypothesized that increasing the DC populations in donor lymphocyte infusions (DLIs) may augment the graft versus malignancy effect, particularly if granulocyte-macrophage colony-stimulating factor (GM-CSF) mobilization resulted in increased precursor dendritic cell (pDC) 1 cells. Mature DCs, pDC1 cells, pDC2 cells, and CD34(+) cells from the same donor were compared after granulocyte colony-stimulating factor (G-CSF) mobilized peripheral blood stem cell collections and GM-CSF mobilized DLI collections. Mobilization with G-CSF resulted in up to a 10-fold larger number of CD34(+) cells per kg and a 3-5-fold larger number of mature DCs, pDC1 cells, and pDC2 cells within the same donor compared with GM-CSF. The ratio of pDC1 to pDC2 in each donor remained constant with either cytokine. In this small sample of normal donors, it appears that G-CSF mobilizes more CD34(+) cells, mature DCs, pDC1 cells, and pDC2 cells within the same donor than does GM-CSF, with no significant polarization by G-CSF or GM-CSF for either pDC1 or pDC2 cells.

No Polarization of Type 1 or Type 2 Precursor Dendritic Cells in Peripheral Blood Stem Cell Collections of Non-Hodgkin's Lymphoma Patients Mobilized with Cyclophosphamide Plus G-CSF, GM-CSF, or GM-CSF Followed by G-CSF

Dendritic cells (DCs) are the most efficient antigen-presenting cells and play a role in immune reconstitution after autologous transplantation. Recent reports suggest that mobilization with granulocyte colony-stimulating factor (G-CSF) containing regimens polarizes DCs into pDC2, which could potentially result with increased Th2 response and decreased graft-versus-host disease (GVHD) in allogeneic transplantation and with decreased cytotoxic Th1 response and graft versus tumor effect, which in autologous transplantation could translate into increased relapse rate. Previously, we have shown that non-Hodgkin's lymphoma (NHL) patients receiving cyclophosphamide (CTX) plus granulocyte- macrophage (GM)-CSF, G-CSF or GM-CSF followed by G-CSF for stem cell collection, mobilize up to five-fold more mature CD80(+) DCs compared to CTX plus G-CSF mobilized patients. Here, we analyzed samples from the same study for the number of pDC1 and pDC2 subsets in blood and apheresis products obtained from these patients. Samples from 29 patients were collected. Patients mobilized with CTX plus G-CSF collected a mean of 1.2 +/- 0.4 x 10(6) pDC1/kg per day and 2.2 +/- 1 x 10(6) pDC2/kg per day, whereas patients mobilized with CTX plus GM-CSF collected a mean of 1.1 +/- 0.5 x 10(6) pDC1 and 1.5 +/- 0.9 x 10(6) pDC2/kg per day. Patients mobilized with CTX plus GM-CSF followed by G-CSF collected 2.5 +/- 1.1 x 10(6) pDC1 and 2 +/- 0.5 x 106 pDC2/kg per day, with significantly higher levels of pDC1 +/- pDC2 cells. No significant difference was observed in pDC1/pDC2 ratio between the three mobilization arms. Patients mobilized with the GM-CSFcontaining regimen had a higher probability for survival compared to patients receiving G-CSF alone (median of 55 months vs. 15 months; p = 0.02). These results support the hypothesis that higher levels of DCs in the graft might be associated with prolonged survival of autotransplanted NHL patients. Further similar studies are merited in a larger population of NHL patients.

Vaccine strategies to treat lymphoproliferative disorders

Lymphoproliferative disorders, including follicular lymphoma (FL), multiple myeloma (MM) and chronic lymphatic leukaemia (CLL), are slowly progressive malignancies which remain incurable despite advances in therapy. Harnessing the immune system to recognise and destroy tumours is a promising new approach to treating these diseases. Dendritic cells (DC) are unique antigen-presenting cells that play a central role in the initiation and direction of immune responses. DC loaded ex vivo with tumour-associated antigens and administered as a vaccine have already shown promise in early clinical trials for a number of lymphoproliferative disorders, but the need for improvement is widely agreed. Recent advances in the understanding of basic DC biology and lessons from early clinical trials have provided exciting new insights into the generation of anti-tumour immune responses and the design of vaccine strategies. In this review we provide an overview of our current understanding of DC biology and their function in patients with lymphoproliferative disorders. We discuss the current status of clinical trials and new approaches to exploit the antigen presenting capacity of DC to design vaccines of the future.

Effects of dendritic cells from cord blood CD34+ cells on human hepatocarcinoma cell line BEL-7402 in vitro and in SCID mice

AIM: To develop a cancer vaccine of dendritic cells derived from human cord blood CD34+ cells and to investigate its cytotoxicity on human hepatocarcinoma cells in vitro and in sever combined immunodeficiency (SCID) mice.

METHODS: Lymphocytes from cord blood or peripheral blood were primed by DCs, which were derived from cord blood and pulsed with whole tumor cell lysates. Nonradiative neutral red uptake assay was adopted to detect the cytotoxicity of primed lymphocytes on human hepatocarcinoma cell line BEL-7402 in vitro. The anti-tumor effect of primed lymphocytes in vivo was detected in SCID mice, including therapeutic effect and vaccination effect.

RESULTS: The cytotoxicity of DC vaccine primed lymphocytes from cord blood or peripheral blood on human hepatoc-arcinoma cell line BEL-7402 was significantly higher than that of unprimed lymphocytes in vitro (44.09% vs 14.69%, 47.92% vs 19.44%, P<0.01). There was no significant difference between the cytotoxicity of primed lymphocytes from cord blood and peripheral blood (P>0.05). The tumor growth rate and tumor size were smaller in SCID mice treated or vaccinated with primed lymphocytes than those with unprimed lymphocytes. SCID mice vaccinated with primed lymphocytes had a lower tumor incidence (80% vs 100%, P<0.05) and delayed tumor latent period compared with mice vaccinated with unprimed lymphocytes (11 d vs 7 d, P<0.01).

CONCLUSION: Vaccine of cord blood derived-DCs has an inhibitory activity on growth of human hepatocarcinoma cells in vitro and in SCID mice. The results also implicate the potential role of cord blood derived-DC vaccine in clinical tumor immunotherapy.

Impaired function of circulating dendritic cells in patients with pancreatic cancer

PURPOSE AND EXPERIMENTAL DESIGN

Dendritic cells (DCs) are important for immune surveillance and play a central role in protection against infection and malignancy. DCs comprise two subsets: DC1 (myeloid DC) and DC2 (lymphoid DC). The aim of this study is to determine whether the number and/or function of circulating DCs were decreased in patients with pancreatic cancer and to evaluate the effects of these changes in patients with locally advanced pancreatic cancer before and after chemoradiotherapy (CRT). We examined the circulating DC number and function using the peripheral blood from 29 patients with pancreatic cancer and 20 healthy control subjects. In patients who underwent CRT (n = 20), blood samples were taken before and after CRT. DCs were tested for the ability to stimulate allogeneic T lymphocytes in mixed leukocyte reaction (MLR). CD4/8, NK activity, PHA, and TGF-beta1 were also measured.

RESULTS

The number and allostimulatory activity of circulating DC1s in patients were significantly lower than those in controls. In the patients who underwent CRT, the allostimulatory activity of DC1s at post-CRT was significantly increased as compared to those at pre-CRT. The level of TGF-beta1 was also significantly decreased at post-CRT as compared to pre-CRT. There were no changes in CD4/8, NK activity and proliferative response of T lymphocytes at the peri-CRT period.

CONCLUSION

These data indicate that the number and function of circulating DCs were impaired in patients with pancreatic cancer. Chemoradiotherapy, however, improved DC function, which might be related to decreased immunosuppressive cytokine levels.

Dendritic cell-tumor cell hybrid vaccination for metastatic cancer

Dendritic cells are the most potent antigen-presenting cells, and the possibility of their use for cancer vaccination has renewed the interest in this therapeutic modality. Nevertheless, the ideal immunization protocol with these cells has not been described yet. In this paper we describe the preliminary results of a protocol using autologous tumor and allogeneic dendritic hybrid cell vaccination every 6 weeks, for metastatic melanoma and renal cell carcinoma (RCC) patients. Thirty-five patients were enrolled between March 2001 and March 2003. Though all patients included presented with large tumor burdens and progressive diseases, 71% of them experienced stability after vaccination, with durations up to 19 months. Among RCC patients 3/22 (14%) presented objective responses. The median time to progression was 4 months for melanoma and 5.7 months for RCC patients; no significant untoward effects were noted. Furthermore, immune function, as evaluated by cutaneous delayed-type hypersensitivity reactions to recall antigens and by peripheral blood proliferative responses to tumor-specific and nonspecific stimuli, presented a clear tendency to recover in vaccinated patients. These data indicate that dendritic cell-tumor cell hybrid vaccination affects the natural history of advanced cancer and provide support for its study in less advanced patients, who should, more likely, benefit even more from this approach.

Chemotherapy plus G-CSF mobilized peripheral blood stem cell harvests from acute myeloid leukaemia patients contain large amounts of polyclonal myeloid linneg CD11cpos dendritic precursor cells

Dendritic cells (DC) are potent antigen-presenting cells that can induce effective tumour-specific T-cell responses. This study investigated leucapheresis products as source of DC precursors in 48 patients undergoing autologous peripheral blood stem cell (PBSC) transplantation for haematological malignancies. Strikingly, high-dose cytarabine and etoposide plus granulocyte colony stimulating factor (G-CSF) mobilized PBSC harvests from acute myeloid leukaemia (AML) patients containing the highest number of myeloid lin(neg)CD11c(pos) DC (mean: 7.04 x 106/kg, range: 1.46-19.67) which was 18.1-fold higher than in non-AML patients mobilized using chemotherapy (CT) regimens plus G-CSF. Clonality of purified lin(neg)CD11c(pos) DC from CT plus G-CSF mobilized AML patients (n = 8 ) was assessed using the human androgen-receptor locus methylation, disclosing a polyclonal pattern in five female patients. These cells displayed morphological and phenotypic features of myeloid DC precursors with expression of HLA-DR, HLA-ABC, CD86, CCR5 and CD54 molecules but lacking CD80, CD83, CD1a and CD40 antigens. Short-term culture with autologous leukaemic cell lysates plus tumour necrosis factor-alpha yielded maturated myeloid DC capable of triggering interleukin-2 and interferon-gamma production by autologous T-lymphocytes. These findings suggest that the use of post-remission CT and G-CSF as mobilizing regimen in AML patients generates PBSC containing high doses of polyclonal myeloid lin(neg)CD11c(pos) DC precursors, which could be used to design feasible immunotherapy protocols.