A generic RNA-pulsed dendritic cell vaccine strategy for renal cell carcinoma

RNA modification in mRNA cancer vaccines

RNA modification is manifested as chemically altered nucleotides, widely exists in diverse natural RNAs, and is closely related to RNA structure and function. Currently, mRNA-based vaccines have received great attention and rapid development as novel and mighty fighters against various diseases including cancer. The achievement of RNA vaccines in clinical application is largely attributed to some methodological innovations including the incorporation of modified nucleotides into the synthetic RNA. The selection of optimal RNA modifications aimed at reducing the instability and immunogenicity of RNA molecules is a very critical task to improve the efficacy and safety of mRNA vaccines. This review summarizes the functions of RNA modifications and their application in mRNA vaccines, highlights recent advances of mRNA vaccines in cancer immunotherapy, and provides perspectives for future development of mRNA vaccines in the context of personalized tumor therapy.

Gene-modified dendritic cell vaccines for cancer

Dendritic cell (DC) vaccines are an immunotherapeutic approach to cancer treatment that use the antigen-presentation machinery of DCs to activate an endogenous anti-tumor response. In this treatment strategy, DCs are cultured ex vivo, exposed to tumor antigens and administered to the patient. The ex vivo culturing provides a unique and powerful opportunity to modify and enhance the DCs. As such, a variety of genetic engineering approaches have been employed to optimize DC vaccines, including the introduction of messenger RNA and small interfering RNA, viral gene transduction, and even fusion with whole tumor cells. In general, these modifications aim to improve targeting, enhance immunogenicity, and reduce susceptibility to the immunosuppressive tumor microenvironment. It has been demonstrated that several of these modifications can be employed in tandem, allowing for fine-tuning and optimization of the DC vaccine across multiple metrics. Thus, the application of genetic engineering techniques to the dendritic cell vaccine platform has the potential to greatly enhance its efficacy in the clinic.

Apoptic Renal Carcinoma Cells are Better Inducers of Cross-Presenting Activity than Their Primary Necrotic Counterpart

Vaccination with tumor-loaded dendritic cells (DC) is a promising treatment strategy for patients with renal cell carcinoma (RCC). Cells undergoing cell death proved useful as a source of tumor antigen for DC loading. Both apoptotic and necrotic tumor cells have been shown to efficiently load RCC-tumor antigens on DC. However, no direct comparison of these two kinds of death has been attempted in the same RCC. We compared DC pulsed with apoptotic cells, whole cell lysates or their supernatants of the cell line K1, derived from a patient with clear cell RCC, to determine their ability to activate T cells. Monocyte-derived DCs were pulsed with the different sources of tumor antigen, matured and co-cultured with autologouos peripheral blood lymphocytes. After three weekly re-stimulations with DCs, generation of cytotoxic T lymphocytes CTL was assessed by IFN-γ release in an ELISpot assay in the presence of the sensitizing target. By comparison with lysate, apoptotic tumor cells induced a higher frequency of MHC class I-restricted IFN-γ releasing lymphocytes. A higher CTL response was induced by pulsing DCs with cell lysate supernatant compared with whole cell lysate. These results indicate that, although necrotic death has been regarded as highly permissive when compared to apoptotic death, the immunogenicity of the death treatment may vary from one tumor to another.

Comparison of cytotoxic T lymphocyte responses against pancreatic cancer induced by dendritic cells transfected with total tumor RNA and fusion hybrided with tumor cell

Pancreatic cancer (PC) is a deadly human malignancy. Dendritic cell (DC)-based immunotherapy with whole tumor antigens demonstrates potential efficiency in cancer treatment. Tumor RNA and tumor fusion hybrid cells are sources of whole tumor antigens for preparing DC tumor vaccines. However, the efficacy of these sources in eliciting immune responses against PC has not yet to be directly compared. In the present study, patient-derived PC cells and DCs were fused (DC-tumor hybrids) and primary cultured PC cell-derived total RNA was electroporated into autologous DCs (DC-tumor RNA). The antitumor immune responses induced by DC-tumor hybrids and DC-tumor RNA were compared directly. The results showed that both RNA and hybrid methodologies could induce tumor-specific cytotoxic T lymphocyte (CTL) responses, but pulsing DCs with total tumor RNA could induce a higher frequency of activated CTLs and T-helper cells than fusing DCs with autologous tumor cells. In addition, DC-tumor RNA triggered stronger autologous tumor cell lysis than DC-tumor hybrids. It could be concluded that DCs pulsed with whole tumor RNA are superior to those fused with tumor cells in priming anti-PC CTL responses. Electroporation with total tumor RNA may be more suitable for DC-based PC vaccination.

mRNA-based dendritic cell vaccines

Cancer immunotherapy has been proposed as a powerful treatment modality. Active immunotherapy aspires to stimulate the patient's immune system, particularly T cells. These cells can recognize and kill cancer cells and can form an immunological memory. Dendritic cells (DCs) are the professional antigen-presenting cells of our immune system. They take up and process antigens to present them to T cells. Consequently, DCs have been investigated as a means to stimulate cancer-specific T-cell responses. An efficient strategy to program DCs is the use of mRNA, a well-defined and safe molecule that can be easily generated at high purity. Importantly, vaccines consisting of mRNA-modified DCs showed promising results in clinical trials. Therefore, we will introduce cancer immunotherapy and DCs and give a detailed overview on the application of mRNA to generate cancer-fighting DC vaccines.

Genetically modified dendritic cells in cancer immunotherapy: a better tomorrow?

IMPORTANCE OF THE FIELD

Dendritic cells (DC) are powerful antigen-presenting cells that induce and maintain primary cytotoxic T lymphocyte (CTL) responses directed against tumor antigens. Consequently, there has been much interest in their application as antitumor vaccines.

AREAS COVERED IN THIS REVIEW

A large number of DC-based vaccine trials targeting a variety of cancers have been conducted; however, the rate of reported clinically significant responses remains low. Modification of DC to express tumor antigens or immunostimulatory molecules through the transfer of genes or mRNA transfection offers a logical alternative with potential advantages over peptide- or protein antigen-loaded DC. In this article, we review the current results and future prospects for genetically modified DC vaccines for the treatment of cancer.

WHAT THE READER WILL GAIN

Genetically-modified dendritic cell-based vaccines represent a powerful tool for cancer therapy. Numerous preclinical and clinical studies have demonstrated the potential of dendritic cell vaccines alone or in combination with other therapeutic modalities.

TAKE HOME MESSAGE

Genetically modified DC-based anti-cancer vaccination holds promise, perhaps being best employed in the adjuvant setting with minimal residual disease after primary therapy, or in combination with other antitumor or immune-enhancing therapies.

Update on vaccine development for renal cell cancer

Renal cell carcinoma (RCC) remains a significant health concern that frequently presents as metastatic disease at the time of initial diagnosis. Current first-line therapeutics for the advanced-stage RCC include antiangiogenic drugs that have yielded high rates of objective clinical response; however, these tend to be transient in nature, with many patients becoming refractory to chronic treatment with these agents. Adjuvant immunotherapies remain viable candidates to sustain disease-free and overall patient survival. In particular, vaccines designed to optimize the activation, maintenance, and recruitment of specific immunity within or into the tumor site continue to evolve. Based on the integration of increasingly refined immunomonitoring systems in both translational models and clinical trials, allowing for the improved understanding of treatment mechanism(s) of action, further refined (combinational) vaccine protocols are currently being developed and evaluated. This review provides a brief history of RCC vaccine development, discusses the successes and limitations in such approaches, and provides a rationale for developing combinational vaccine approaches that may provide improved clinical benefits to patients with RCC.

Personalized dendritic cell-based tumor immunotherapy

Advances in the understanding of the immunoregulatory functions of dendritic cells (DCs) in animal models and humans have led to their exploitation as anticancer vaccines. Although DC-based immunotherapy has proven clinically safe and efficient to induce tumor-specific immune responses, only a limited number of objective clinical responses have been reported in cancer patients. These relatively disappointing results have prompted the evaluation of multiple approaches to improve the efficacy of DC vaccines. The topic of this review focuses on personalized DC-based anticancer vaccines, which in theory have the potential to present to the host immune system the entire repertoire of antigens harbored by autologous tumor cells. We also discuss the implementation of these vaccines in cancer therapeutic strategies, their limitations and the future challenges for effective immunotherapy against cancer.

Dendritic cell-Ewing's sarcoma cell hybrids enhance antitumor immunity

Given the effective immunotherapy of DC-based vaccine in other cancers, we hypothesized DC-based vaccines would induce effective immune responses against Ewing's sarcoma. To verify this hypothesis and develop the most effective dendritic cell vaccine against Ewing's sarcoma, we evaluated the antitumor efficacy of dendritic cell-Ewing's sarcoma hybrids and dendritic cells pulsed with other antigen-loading methods, including cell lysates and the characteristic EWS-FLI1 gene of Ewing's sarcoma, using an A673 cell line as a model. The hybrids were generated by electrofusion with fusion efficiency and viability determined by flow cytometry and fluorescent microscopy analyses. By interferon-gamma secretion assay, the capacity of hybrids to stimulate cytotoxic T-lymphocytes (CTLs) is higher than that of other antigen-loading methods showing stronger tumor antigen-specific CTL cytotoxicity to A673. By in vivo experiment in SCID mice, all dendritic cell-based strategies induced specific immune responses to Ewing's sarcoma after mice-human immune system reconstitution by inoculating human peripheral blood mononuclear cells into the peritoneal cavity of SCID mice. However, the hybrids most inhibited the subcutaneous tumor growth in SCID mice compared with dendritic cells pulsed with other loading methods. The data suggest A673 cells respond to dendritic cell-based immunotherapy.

Whole tumor antigen vaccination using dendritic cells: comparison of RNA electroporation and pulsing with UV-irradiated tumor cells

Because of the lack of full characterization of tumor associated antigens for solid tumors, whole antigen use is a convenient approach to tumor vaccination. Tumor RNA and apoptotic tumor cells have been used as a source of whole tumor antigen to prepare dendritic cell (DC) based tumor vaccines, but their efficacy has not been directly compared. Here we compare directly RNA electroporation and pulsing of DCs with whole tumor cells killed by ultraviolet (UV) B radiation using a convenient tumor model expressing human papilloma virus (HPV) E6 and E7 oncogenes. Although both approaches led to DCs presenting tumor antigen, electroporation with tumor cell total RNA induced a significantly higher frequency of tumor-reactive IFN-gamma secreting T cells, and E7-specific CD8+ lymphocytes compared to pulsing with UV-irradiated tumor cells. DCs electroporated with tumor cell RNA induced a larger tumor infiltration by T cells and produced a significantly stronger delay in tumor growth compared to DCs pulsed with UV-irradiated tumor cells. We conclude that electroporation with whole tumor cell RNA and pulsing with UV-irradiated tumor cells are both effective in eliciting antitumor immune response, but RNA electroporation results in more potent tumor vaccination under the examined experimental conditions.

Autologous large multivalent immunogen vaccine in patients with metastatic melanoma and renal cell carcinoma

OBJECTIVE

To evaluate the safety and activity of large multivalent immunogen (LMI), prepared by immobilizing autologous tumor cell plasma membrane on 5-microm diameter silica beads, in patients with melanoma and renal cell carcinoma (RCC).

METHODS

Thirty patients with stage IV metastatic melanoma and 31 patients with stage IV RCC were randomly assigned to 1 of 3 trial arms and received monthly treatment with (1) LMI alone, (2) cyclophosphamide followed 8 days later with LMI, or (3) the same treatment as in arm 2 with IL-2 given for 5 days beginning 1 week after LMI administration.

RESULTS

No grade 4 toxicities were observed. For patients with melanoma, median overall survival time for all 30 patients was 20.4 months [95% confidence interval (CI): 8.0-not assessable], and median progression-free survival was 2.8 months (95% CI: 1.9-6.3). For patients with RCC, median overall survival exceeded 46.2 months (95% CI: 30.3-not assessable), and median progression-free survival was 12.2 months (95% CI: 4.6-not assessable). Two patients had a partial response to LMI treatment.

CONCLUSIONS

Based on our results that demonstrate the safety and tolerability of LMI vaccine, further development of this therapy is warranted to evaluate its clinical efficacy.

Translational mini-review series on vaccines: Dendritic cell-based vaccines in renal cancer

Renal cancer is a relatively uncommon solid tumor, accounting for about 3% of all adult malignancies, however this rate incidence is rising. The most common histological renal cell carcinoma (RCC) subtype is clear cell carcinoma that makes up approximately 70-80% of all renal neoplasms and appears to be the only histological subtype that is responsive to immunotherapeutic approaches with any consistency. Therefore, it has been hypothesized that immune-mediated mechanisms play important roles in limiting tumor growth and that dendritic cells (DC), the most potent APC in the body, and T cells are the dominant effector cells that regulate tumor progression in situ. In this context, the development of clinically effective DC-based vaccines is a major focus for active specific immunotherapy in renal cancer. In the current review we have not focused on the results of recently published RCC clinical trials, as several excellent reviews have already performed this function. Instead, we turned our attention to how the perception and practical application of DC-based vaccinations are evolving.

Dendritic cell vaccine strategies for renal cell carcinoma

Dendritic cell (DC) vaccines are an important experimental immunotherapy for renal cell carcinomas. DC vaccines have proven safe, but only minimal clinical efficacy has been observed to date. DC vaccine strategies reflect the continually evolving understanding of DC biology. The use of mature DCs is particularly important to avoid the induction of regulatory T cells. Better defined sources of immunizing antigens and more efficient antigen-loading will contribute to DC vaccines of better quality. Improved clinical efficacy may also be achieved using DCs that secrete biologically active IL-12, which fosters innate immunity and polarizes T helper type 1 responses that contribute to optimal antitumor immunity. Furthermore, combination therapies that treat systemic immune suppression will be crucial for obtaining improved clinical responses to DC vaccines in patients with advanced disease.

Apoptotic, necrotic, or fused tumor cells: an equivalent source of antigen for dendritic cell loading

The identification of the most efficient strategy for tumor antigen loading of dendritic cells (DCs) remains a challenge in cancer immunotherapy protocols. Autologous dead tumor cells have been demonstrated to constitute an acceptable source of multiple tumor-associated antigens (TAA) to pulse DCs. However the optimal approach for inducing cell death that would lead to effective endocytosis and activation of DCs remains controversial. In this study we have induced and defined 3 distinct mechanisms of tumor cell death (apoptosis, necrosis and fusion-mediated cell death), and investigated their differential effects on DCs. Bone marrow-derived DCs demonstrated comparable uptake of primary apoptotic, necrotic, or fused dead tumor cells. Furthermore, the distinct modes of cancer cell death had analogous potential in activating the transcription factors NF-kappaB and STAT1 and in maturing DCs, resulting in an equally effective stimulation of immune T cells. The current study therefore provides further informations on the use of dead whole tumor cells as antigen sources for effective active anti-cancer immunotherapy.