Increase of in vivo antitumoral activity by CD40L (CD154) gene transfer into pancreatic tumor cell-dendritic cell hybrids

Cellular immunotherapies for cancer

Cancer is a major burden on the healthcare system, and new therapies are needed. Recently, the development of immunotherapies, which aim to boost or use the immune system, or its constituents, as a tool to fight malignant cells, has provided a major new tool in the arsenal of clinicians and has revolutionized the treatment of many cancers.Cellular immunotherapies are based on the administration of living cells to patients and have developed hugely, especially since 2010 when Sipuleucel-T (Provenge), a DC vaccine, was the first cellular immunotherapy to be approved by the FDA. The ensuing years have seen two further cellular immunotherapies gain FDA approval: tisagenlecleucel (Kymriah) and axicabtagene ciloleucel (Yescarta).This review will give an overview of the principles of immunotherapies before focusing on the major forms of cellular immunotherapies individually, T cell-based, natural killer (NK) cell-based and dendritic cell (DC)-based, as well as detailing some of the clinical trials relevant to each therapy.

Dendritic cells in pancreatic cancer immunotherapy: Vaccines and combination immunotherapies

Despite significant advances over the past decades of research, pancreatic cancer (PC) continues to have the worst 5-year survival of any malignancy. Dendritic cells (DCs) are the most potent professional antigen-presenting cells and are involved in the induction and regulation of antitumor immune responses. DC-based immunotherapy has been used in clinical trials for PC. Although safety, efficacy, and immune activation were reported in patients with PC, DC vaccines have not yet fulfilled their promise. Additional strategies for combinatorial approaches aimed to augment and sustain the antitumor specific immune response elicited by DC vaccines are currently being investigated. Here, we will discuss DC vaccination immunotherapies that are currently under preclinical and clinical investigation and potential combination approaches for treating and improving the survival of PC patients.

Targeting dendritic cells in pancreatic ductal adenocarcinoma

Dendritic cells (DC) are an integral part of the tumor microenvironment. Pancreatic cancer is characterized by reduced number and function of DCs, which impacts antigen presentation and contributes to immune tolerance. Recent data suggest that exosomes can mediate communication between pancreatic cancer cells and DCs. Furthermore, levels of DCs may serve as prognostic factors. There is also growing evidence for the effectiveness of vaccination with DCs pulsed with tumor antigens to initiate adaptive cytolytic immune responses via T cells. Most experience with DC-based vaccination has been gathered for MUC1 and WT1 antigens, where clinical studies in advanced pancreatic cancer have provided encouraging results. In this review, we highlight the role of DC in the course, prognosis and treatment of pancreatic cancer.

Dendritic cell-based cancer immunotherapy for pancreatic cancer

Pancreatic cancer (PC) is a lethal disease and remains one of the most resistant cancers to traditional therapies. New therapeutic modalities are urgently needed, particularly immunotherapy, which has shown promise in numerous animal model studies. Dendritic cell (DC)-based immunotherapy has been used in clinical trials for various cancers, including PC, because DCs are the most potent antigen-presenting cell (APC), which are capable of priming naive T cells and stimulating memory T cells to generate antigen-specific responses. In this paper, we review the preclinical and clinical efforts towards the application of DCs for PC.

Dendritic cells fused with different pancreatic carcinoma cells induce different T-cell responses

Background

It is unclear whether there are any differences in the induction of cytotoxic T lymphocytes (CTL) and CD4⁺CD25^high regulatory T-cells (Tregs) among dendritic cells (DCs) fused with different pancreatic carcinomas. The aim of this study was to compare the ability to induce cytotoxicity by human DCs fused with different human pancreatic carcinoma cell lines and to elucidate the causes of variable cytotoxicity among cell lines.

Methods

Monocyte-derived DCs, which were generated from peripheral blood mononuclear cells (PBMCs), were fused with carcinoma cells such as Panc-1, KP-1NL, QGP-1, and KP-3L. The induction of CTL and Tregs, and cytokine profile of PBMCs stimulated by fused DCs were evaluated.

Results

The cytotoxicity against tumor targets induced by PBMCs cocultured with DCs fused with QGP-1 (DC/QGP-1) was very low, even though PBMCs cocultured with DCs fused with other cell lines induced significant cytotoxicity against the respective tumor target. The factors causing this low cytotoxicity were subsequently investigated. DC/QGP-1 induced a significant expansion of Tregs in cocultured PBMCs compared with DC/KP-3L. The level of interleukin-10 secreted in the supernatants of PBMCs cocultured with DC/QGP-1 was increased significantly compared with that in DC/KP-3L. Downregulation of major histocompatibility complex class I expression and increased secretion of vascular endothelial growth factor were observed with QGP-1, as well as in the other cell lines.

Conclusion

The present study demonstrated that the cytotoxicity induced by DCs fused with pancreatic cancer cell lines was different between each cell line, and that the reduced cytotoxicity of DC/QGP-1 might be related to the increased secretion of interleukin-10 and the extensive induction of Tregs.

Novel immunocompetent murine models representing advanced local and metastatic pancreatic cancer

BACKGROUND

The development of novel therapeutics for pancreatic cancer has been hindered by a lack of relevant preclinical models. The purpose of this study was to evaluate the clinical relevancy of two pancreatic cancer models using standard-of-care therapeutic agent gemcitabine.

MATERIALS AND METHODS

Murine Panc02 cells were injected directly into the spleen or pancreas of C57BL/6 mice to respectively create models of metastatic and locally advanced pancreatic cancer. Beginning 7 d post-Panc02 injection, treated mice received 20 mg/kg gemcitabine i.p. every 3 d. Animals were sacrificed when the untreated mice became moribund and tumor/liver weight used to assess tumor burden.

RESULTS

Untreated mice became moribund 22 d after pancreatic Panc02 injection. Gross analysis revealed localized pancreatic tumors weighing 1.063 g. Intrasplenic Panc02 injection produced extensive liver metastasis by d 15 when the untreated mice first became moribund. Liver weights at this time averaged 3.6 g compared with the average non-tumor-bearing weight of 1.23 g. Gemcitabine therapy resulted in a 54% decrease in localized pancreatic tumor weight and 62.5% decrease in metastatic liver weight. Additionally, gemcitabine therapy extended animal survival to 20.5 d compared with 18.0 d average for the untreated mice.

CONCLUSIONS

We describe two models depicting both locally advanced and metastatic pancreatic cancer in immunocompetent mice. In efforts to establish baseline therapeutic efficacy, we determined that gemcitabine reduces tumor burden in both models and enhances survival in the metastatic model. These clinically relevant models provide valuable tools to evaluate novel therapeutics in pancreatic cancer.

The presence of IGHG1 in human pancreatic carcinomas is associated with immune evasion mechanisms

OBJECTIVES

To investigate the expression of Igγ-1 chain C region (IGHG1) in human pancreatic carcinomas and determine the biological function of IGHG1 expression in immune evasion mechanisms.

METHODS

Comparative proteomic analysis was used to detect the differential expression of IGHG1 in human pancreatic cancer tissues versus adjacent noncancerous tissues, followed by confirmatory tests including quantitative real-time reverse transcription-polymerase chain reaction, Western blot analysis, immunohistochemistry, and immunofluorescence. A murine pancreatic tumor model was established by transplantation of IGHG1-overexpressing Panc02 cells. The cytotoxic responses of natural killer (NK) cells were assessed with a lactate dehydrogenase release assay.

RESULTS

Igγ-1 chain C region was found to be present in human pancreatic cancer tissues but nearly absent or expressed lower in adjacent noncancerous tissues. In the murine pancreatic tumor model, the tumor growth was significantly accelerated from day 12 to 20 after tumor injection, and the survival time of animals was decreased. Blockage of IGHG1 led to retarded tumor growth and improved survival. The cytotoxicity assay revealed that IGHG1 downregulated the cytotoxic activity of NK cells through inhibition of antibody-dependent cellular cytotoxicity function.

CONCLUSIONS

The presence of IGHG1 in pancreatic cancer cells might constitute an important element responsible for tumor cell proliferation and immune evasion mechanisms.

Immunologic monitoring of cellular responses by dendritic/tumor cell fusion vaccines

Although dendritic cell (DC)- based cancer vaccines induce effective antitumor activities in murine models, only limited therapeutic results have been obtained in clinical trials. As cancer vaccines induce antitumor activities by eliciting or modifying immune responses in patients with cancer, the Response Evaluation Criteria in Solid Tumors (RECIST) and WHO criteria, designed to detect early effects of cytotoxic chemotherapy in solid tumors, may not provide a complete assessment of cancer vaccines. The problem may, in part, be resolved by carrying out immunologic cellular monitoring, which is one prerequisite for rational development of cancer vaccines. In this review, we will discuss immunologic monitoring of cellular responses for the evaluation of cancer vaccines including fusions of DC and whole tumor cell.

CTLA4 is expressed on mature dendritic cells derived from human monocytes and influences their maturation and antigen presentation

Background

Dendritic cells (DCs) initiate immune responses through their direct interaction with effector cells. However, the mechanism by which DC activity is regulated is not well defined. Previous studies have shown that CTLA4 on T cells regulates DCs function by "cross-talk". We investigated whether there is an intrinsic regulatory mechanism in DCs, with CTLA4 as a candidate regulator.

Results

We confirmed via RT-PCR and flow cytometry the natural expression of CTLA4 on mature DCs derived from human monocytes. Approximately 8% CD1a-positive cells express CTLA4 both on surface and intracellular, whereas 10% CD1a-negative cells express CTLA4 intracellularly, but little expression was observed on the cell surface. The cross-linking of CTLA4 inhibits DCs maturation and antigen presentation in vitro, but does not inhibit endocytosis.

Conclusions

CTLA4 is expressed by DCs and plays an inhibitory role. CTLA4-expressing DCs may represent a group of regulatory DCs. Because of its wide distribution on different cell types, CTLA4 may play a general role in regulating immune responses.

Regulation of tumor immunity by tumor/dendritic cell fusions

The goal of cancer vaccines is to induce antitumor immunity that ultimately will reduce tumor burden in tumor environment. Several strategies involving dendritic cells- (DCs)- based vaccine incorporating different tumor-associated antigens to induce antitumor immune responses against tumors have been tested in clinical trials worldwide. Although DCs-based vaccine such as fusions of whole tumor cells and DCs has been proven to be clinically safe and is efficient to enhance antitumor immune responses for inducing effective immune response and for breaking T-cell tolerance to tumor-associated antigens (TAAs), only a limited success has occurred in clinical trials. This paper reviews tumor immune escape and current strategies employed in the field of tumor/DC fusions vaccine aimed at enhancing activation of TAAs-specific cytotoxic T cells in tumor microenvironment.

1-MT enhances potency of tumor cell lysate-pulsed dendritic cells against pancreatic adenocarcinoma by downregulating the percentage of Tregs

This study examined whether 1-methyl-tryptophan [1-MT, an indoleamine 2, 3-dioxygenase (IDO) inhibitor] could reduce CD4+CD25+ regulatory T cells (Tregs) proliferation and improve the anti-tumor efficacy of dendritic cells (DCs) pulsed with tumor cell lysate in the mice bearing pancreatic adenocarcinoma. The models of pancreatic adenocarcinoma were established in C57BL/6 mice by subcutaneous injection of Pan02 cells. Eight mice which were subcutaneously injected with PBS served as control. The expression of IDO was determined in tumor draining lymph nodes (TDLNs) and spleens of the murine pancreatic adenocarcinoma models. The prevalence of Tregs was measured in the TDLNs and spleens before and after 1-MT administration. The dendritic cells were pulsed with tumor cell lysate for preparing DC vaccine. The DC vaccine, as a single agent or in combination with 1-MT, was administered to pancreatic adenocarcinoma mice. The anti-tumor efficacy was determined after different treatments by regular observation of tumor size. The results showed that the levels of IDO mRNA and protein in tumor-bearing mice were significantly higher than those in the normal control mice. The percentage of Tregs in the spleen and TDLNs was also higer in tumor-bearing mice than in normal control mice (P<0.05). Foxp3 expression was significantly lower in the TDLNs and spleens of tumor-bearing mice administrated with 1-MT than that in normal control mice. Furthemore, in the mice that were administered 1-MT plus DC vaccine, the tumor was increased more slowly than in mice treated with DC vaccine or 1-MT alone, or PBS on day 36 (P<0.01). Our results indicated that 1-MT may enhance anti-tumor efficacy of dendritic cells pulsed with tumor cell lysate by downregulating the percentage of Tregs.