Antitumor immunity induced by dendritic cell-based vaccination is dependent on interferon-γ and interleukin-12

The Role of miR-155 in Antitumor Immunity

MicroRNAs belong to a group of short non-coding RNA molecules that are involved in the regulation of gene expression at multiple levels. Their function was described two decades ago, and, since then, microRNAs have become a rapidly developing field of research. Their participation in the regulation of cellular processes, such as proliferation, apoptosis, cell growth, and migration, made microRNAs attractive for cancer research. Moreover, as a single microRNA can simultaneously target multiple molecules, microRNAs offer a unique advantage in regulating multiple cellular processes in different cell types. Many of these cell types are tumor cells and the cells of the immune system. One of the most studied microRNAs in the context of cancer and the immune system is miR-155. MiR-155 plays a role in modulating innate and adaptive immune mechanisms in distinct immune cell types. As such, miR-155 can be part of the communication between the tumor and immune cells and thus impact the process of tumor immunoediting. Several studies have already revealed its effect on antitumor immune responses, and the targeting of this molecule is increasingly implemented in cancer immunotherapy. In this review, we discuss the current knowledge of miR-155 in the regulation of antitumor immunity and the shaping of the tumor microenvironment, and the plausible implementation of miR-155 targeting in cancer therapy.

Anti-tumor immunity elicited by direct intratumoral administration of a recombinant adenovirus expressing either IL-28A/IFN-λ2 or IL-29/IFN-λ1

Interleukin (IL)-28A/interferon (IFN)-λ2 and IL-29/IFN-λ1 have been demonstrated to elicit direct and indirect anti-tumor actions. In this study, we constructed an adenovirus vector expressing either IL-28A/IFN-λ2 (AdIL-28A) or IL-29/IFN-λ1 (AdIL-29) to evaluate the therapeutic properties of intratumoral injection of recombinant adenovirus to apply for the clinical implementation of cancer gene therapy. Despite the lack of an anti-proliferative effect on MCA205 and B16-F10 cells, a retarded growth of established subcutaneous tumors was observed following multiple injections of either AdIL-28A or AdIL-29 when compared with AdNull. In vivo cell depletion experiments displayed that both NK cells and CD8(+) T cells have a major role in AdIL-28A-mediated tumor growth suppression. A significant increase in the number of infiltrating CD8(+) T cells into the tumors treated with either AdIL-28A or AdIL-29 was observed. Moreover, specific anti-tumor cytotoxic T lymphocyte reactivity was detected in spleen cells from animals treated with either AdIL-28A or AdIL-29. In IFN-γ-deficient mice, anti-tumor activities of AdIL-28A were completely impaired, indicating that IFN-γ is critically involved in the tumor growth inhibition triggered by AdIL-28A. IL-12 provided a synergistic anti-tumor effect when combined with AdIL-28A. These results indicate that AdIL-28A and AdIL-29 could be successfully utilized as an alternative cancer immunogene therapy.

Dendritic cell activation by combined exposure to anti-CD40 plus interleukin (IL)-12 and IL-18 efficiently stimulates anti-tumor immunity

Despite as yet limited clinical effectiveness, dendritic cell (DC)-based immunotherapy remains a promising approach for the treatment of cancer, but requires further improvement in its immunostimulatory effectiveness. Potent anti-tumor immunity often depends on the induction of type 1 (T(H)1) immune responses. Therefore, we combined different DC maturation stimuli that are known to induce T(H)1 immunity [anti-CD40, interleukin (IL)-12, IL-18], with the aim to trigger a T(H)1 driven anti-tumor CTL response. When compared with untreated DC or DC treated with anti-CD40 alone, DC matured with anti-CD40 plus IL-12 and IL-18 expressed significantly more IFN-gamma and IL-12, induced enhanced CD8(+) T-cell proliferation, prolonged synaptic interaction with T cells and increased CD8(+) T-cell-mediated cytotoxicity. To analyse if these DC are able to induce efficient anti-tumor immunity, mice carrying a B16-OVA tumor were treated with tumor antigen (TA)-loaded DC that had been exposed to anti-CD40 or to anti-CD40 plus IL-12 and IL-18. Our data show that anti-CD40 plus IL-12 and IL-18 matured DC are superior to controls in retarding tumor growth. These data indicate that maturation of DC with anti-CD40 plus IL-12 and IL-18 potently stimulates the generation of an anti-tumor immune response and may lead to improved immunotherapeutic capacity of DC vaccination.

A Novel Dendritic Cell-Based Cancer Vaccine Produces Promising Results in a Syngenic CC-36 Murine Colon Adenocarcinoma Model

BACKGROUND

This study was conducted to test the efficacy of a new cancer vaccine, composed of dendritic cells (DCs) pulsed with an interleukin-2 gene-encoded vaccinia virus tumor oncolysate (DC-IL-2VCO) in a CC-36 murine colon adenocarcinoma model.

MATERIALS AND METHODS

CC-36 tumor cells were injected subcutaneously into the left flank of four- to six-week old male BALB/c mice. The mice were divided into three groups, each of which received one of the following treatments: (1) DCs pulsed with the IL-2 gene-encoded vaccinia oncolysate (DC-IL-2VCO), (2) DCs pulsed with the tumor oncolysate alone (DC-CO), or (3) no treatment (control). Tumor incidence was measured, and survival rates were compared using a paired Student's t-test. Cytolytic T cell activity was measured in peripheral blood lymphocytes (PBL) and splenic lymphocytes using a (51)Cr-release assay. Lastly, mice were depleted of either CD4+ or CD8+ lymphocytes prior to receiving the vaccine to test the mechanism of tumor immunity in these mice.

RESULTS

Mice treated with DC-IL-2VCO demonstrated decreased tumor burden, increased survival, and greater cytolytic activity compared with control mice and mice receiving DC-CO. In addition, mice depleted of CD8+ T cells prior to immunization with IL-2VV + DC-IL-2VCO had a significant increase in the incidence of tumor, similar to the untreated control mice.

CONCLUSIONS

DCs pulsed with an IL-2 gene-encoded vaccinia virus tumor oncolysate (DC-IL-2VCO) produced safe and effective immune responses in a murine CC-36 colon adenocarcinoma model. This vaccine (DC-MelVac; Patent no. 11221/5) has the potential to treat humans with cancer, and has received FDA approval for use in Phase I clinical trials.

Liposomal vaccines--targeting the delivery of antigen

Vaccines that can prime the adaptive immune system for a quick and effective response against a pathogen or tumor cells, require the generation of antigen (Ag)-specific memory T and B cells. The unique ability of dendritic cells (DCs) to activate naïve T cells, implies a key role for DCs in this process. The generation of tumor-specific CD8(+) cytotoxic T cells (CTLs) is dependent on both T cell stimulation with Ag (peptide-MHC-complexes) and costimulation. Interestingly, tumor cells that lack expression of T cell costimulatory molecules become highly immunogenic when transfected to express such molecules on their surface. Adoptive immunotherapy with Ag-pulsed DCs also is a strategy showing promise as a treatment for cancer. The use of such cell-based vaccines, however, is cumbersome and expensive to use clinically, and/or may carry risks due to genetic manipulations. Liposomes are particulate vesicular lipid structures that can incorporate Ag, immunomodulatory factors and targeting molecules, and hence can serve as potent vaccines. Similarly, Ag-containing plasma membrane vesicles (PMV) derived from tumor cells can be modified to incorporate a T cell costimulatory molecule to provide both TCR stimulation, and costimulation. PMVs also can be modified to contain IFN-gamma and molecules for targeting DCs, permitting delivery of both Ag and a DC maturation signal for initiating an effective immune response. Our results show that use of such agents as vaccines can induce potent anti-tumor immune responses and immunotherapeutic effects in tumor models, and provide a strategy for the development of effective vaccines and immunotherapies for cancer and infectious diseases.

Eliciting specific antitumor immunity against hepatocellular carcinoma in vitro by fusions of HCC patient-derived dendritic cells with HCC cells

AIM: To investigate the ability of fusions of HCC patient-derived dendritic cells (DC) with HCC cells to induce autologous T lymphocytes to elicit specific immunity against HCC in vitro.

METHODS: Dendritic cells isolated from HCC patient peripheral blood were cultured and proliferated in vitro for one wk by using recombinant human granulocyte/macrophage-colony stimulating factor (rhGM-CSF) and interleukin-4 (rhIL-4). Expression of DC surface markers was assessed by flow cytometry. Fusions of DC with HepG2 cells (HepG2/DC) were achieved by polythyleneglycol (PEG). The ability of HepG2/DC to stimulate proliferation and differentiation of autologous T lymphocytes was assessed by MTT method, and the specific killing efficacy of HepG2/DC-induced cytotoxic T lymphocytes (CTL) to HepG2 was evaluated.

RESULTS: Following one wk culture, DC presented a high-level expression of CD1a, HLA-DR, CD54, CD80 and CD86. Fusions had remarkably greater ability to stimulate proliferation of autologous T lymphocytes in comparison with HepG2, HepG2+DC, DC and PBS, with an A value of 0.816±0.019 vs 0.541±0.020, 0.632±0.018, 0.564±0.018, 0.345±0.013, respectively (P<0.05). The HepG2/DC-activated CTLs showed a potent specific killing efficacy to HepG2.

CONCLUSION: Fusions of HCC patient-derived DC with HCC cells can effectively stimulate autologous T lymphocytes to elicit specific antitumor immunity against HCC, and may represent as a promising approach of immunotherapy for HCC.