Induction of polyclonal prostate cancer-specific CTL using dendritic cells transfected with amplified tumor RNA

Kallikrein-related peptidases: mechanistic understanding for potential therapeutic targeting in cancer

INTRODUCTION

Human kallikrein-related peptidases (KLKs) represent a subgroup of 15 serine endopeptidases involved in various physiological processes and pathologies, including cancer.

AREAS COVERED

This review aims to provide a comprehensive overview of the KLK family, highlighting their genomic structure, expression profiles and substrate specificity. We explore the role of KLKs in tumorigenesis, emphasizing their potential as biomarkers and therapeutic targets in cancer treatment. The dysregulated activity of KLKs has been linked to various malignancies, making them promising candidates for cancer diagnostics and therapy.

EXPERT OPINION

: Recent advancements in understanding the mechanistic pathways of KLK-related tumorigenesis offer new prospects for developing targeted cancer treatments. Expert opinion suggests that while significant progress has been made, further research is necessary to fully exploit KLKs' potential in clinical applications.

Vaccines as treatments for prostate cancer

Prostate cancer is a leading cause of death in men worldwide. For over 30 years, growing interest has focused on the development of vaccines as treatments for prostate cancer, with the goal of using vaccines to activate immune cells capable of targeting prostate cancer to either eradicate recurrent disease or at least delay disease progression. This interest has been prompted by the prevalence and long natural history of the disease and by the fact that the prostate is an expendable organ. Thus, an immune response elicited by vaccination might not need to target the tumour uniquely but could theoretically target any prostate tissue. To date, different vaccine approaches and targets for prostate cancer have been evaluated in clinical trials. Overall, five approaches have been assessed in randomized phase III trials and sipuleucel-T was approved as a treatment for metastatic castration-resistant prostate cancer, being the only vaccine approved to date by the FDA as a treatment for cancer. Most vaccine approaches showed safety and some evidence of immunological activity but had poor clinical activity when used as monotherapies. However, increased activity has been observed when these vaccines were used in combination with other immune-modulating therapies. This evidence suggests that, in the future, prostate cancer vaccines might be used to activate and expand tumour-specific T cells as part of combination approaches with agents that target tumour-associated immune mechanisms of resistance.

The Quest for mRNA Vaccines

The success of mRNA vaccines against COVID-19 is nothing short of a medical revolution. Given its chemical lability the use of mRNA as a therapeutic has been counterintuitive and met with skepticism. The development of mRNA-based COVID-19 vaccines was the culmination of long and painstaking efforts by many investigators spanning over 30 years and culminating with the seminal studies of Kariko and Weissman. This review will describe one chapter in this saga, studies that have shown that mRNA can function as a therapeutic. It started with our seminal observation that dendritic cells (DCs) transfected with mRNA in vitro administered to mice inhibits tumor growth, and led to first-in-human clinical trials with mRNA vaccines in cancer patients. The clinical development of this patient-specific DCs-mRNA approach and use on a larger scale was hindered by the challenges associated with personalized cell therapies. Confirmed and extended by many investigators, these studies did serve as impetus and motivation that led scientists to persevere, eventually leading to the development of simple, broadly applicable, and highly effective protocols of directly injecting mRNA into patients, culminating in the COVID-19 mRNA vaccines.

Recent Advances in Cancer Vaccines: Challenges, Achievements, and Futuristic Prospects

Cancer is a chronic disease, and it can be lethal due to limited therapeutic options. The conventional treatment options for cancer have numerous challenges, such as a low blood circulation time as well as poor solubility of anticancer drugs. Therapeutic cancer vaccines emerged to try to improve anticancer drugs' efficiency and to deliver them to the target site. Cancer vaccines are considered a viable therapeutic technique for most solid tumors. Vaccines boost antitumor immunity by delivering tumor antigens, nucleic acids, entire cells, and peptides. Cancer vaccines are designed to induce long-term antitumor memory, causing tumor regression, eradicate minimal residual illness, and prevent non-specific or unpleasant effects. These vaccines can assist in the elimination of cancer cells from various organs or organ systems in the body, with minimal risk of tumor recurrence or metastasis. Vaccines and antigens for anticancer therapy are discussed in this review, including current vaccine adjuvants and mechanisms of action for various types of vaccines, such as DNA- or mRNA-based cancer vaccines. Potential applications of these vaccines focusing on their clinical use for better therapeutic efficacy are also discussed along with the latest research available in this field.

Tumor RNA-loaded nanoliposomes increases the anti-tumor immune response in colorectal cancer

Purpose

Tumor RNA vaccines can activate dendritic cells to generate systemic anti-tumor immune response. However, due to easily degraded of RNA, direct RNA vaccine is less effective. In this study, we optimized the method for preparing PEGylated liposom-polycationic DNA complex (LPD) nanoliposomes, increased encapsulate amount of total RNA derived from CT-26 colorectal cancer cells. Tumor RNA LPD nanoliposomes vaccines improved anti-tumor immune response ability of tumor RNA and can effectively promote anti-tumor therapeutic effect of oxaliplatin.

Methods

Total tumor-derived RNA was extracted from colorectal cancer cells (CT-26 cells), and loaded to our optimized the LPD complex, resulting in the LPD nanoliposomes. We evaluated the characteristics (size, zeta potential, and stability), cytotoxicity, transfection ability, and tumor-growth inhibitory efficacy of LPD nanoliposomes.

Results

The improved LPD nanoliposomes exhibited a spherical shape, RNA loading efficiency of 9.07%, the average size of 120.37 ± 2.949 nm and zeta potential was 3.34 ± 0.056 mV. Also, the improved LPD nanoliposomes showed high stability at 4 °C, with a low toxicity and high cell transfection efficacy toward CT-26 colorectal cancer cells. Notably, the improved LPD nanoliposomes showed tumor growth inhibition by activating anti-tumor immune response in CT-26 colorectal cancer bearing mice, with mini side effects toward the normal organs of mice. Furthermore, the effect of the improved LPD nanoliposomes in combination with oxaliplatin can be better than that of oxaliplatin alone.

Conclusion

The improved LPD nanoliposomes may serve as an effective vaccine to induce antitumor immunity, presenting a new treatment option for colorectal cancer.

Recent advances in breast cancer immunotherapy: The promising impact of nanomedicines

Breast cancer (BC) is one of the prevalent cancers among women. Generally, the treatment of BC is mostly based on several prominent strategies, including chemotherapy, surgery, endocrine therapy, molecular targeted therapy, and radiation. Owing to the growing knowledge about the complexity of BC pathobiology, immunotherapy as a promising treatment modality has substantially improved the patients' care in the clinic. Immunotherapy is used to harness the patient's immune system to recognize and battle devious cancer cells. As a novel therapy approach, this emerging strategy targets the key molecular entities of tumor tissue. To achieve maximal therapeutic impacts, the dynamic interplay between cancer and immune cells needs to be fully comprehended. The key molecular machinery of solid tumors can be targeted by nanoscale immunomedicines. While discussing the potential biomarkers involved in the initiation and progression of BC, we aimed to provide comprehensive insights into the immunotherapy and articulate the recent advances in terms of the therapeutic strategies used to control this disease, including immune checkpoint inhibitors, vaccines, chimeric antigen receptor T cells therapy, and nanomedicines.

Advances in identification and selection of personalized neoantigen/T-cell pairs for autologous adoptive T cell therapies

Based on the success of tumor-infiltrating lymphocytes (TIL)-based therapies, personalized adoptive cell therapies (ACT) targeting neoantigens have the potential to become a disruptive technology and lead to highly effective treatments for cancer patients for whom no other options exist. ACT of TIL, peripheral blood or gene-engineered peripheral blood lymphocytes (PBLs) targeting neoantigens is a highly personalized intervention that requires three discrete steps: i) Identification of suitable personal targets (neoantigens), ii) selection of T cells or their T cell receptors (TCRs) that are specific for the identified neoantigens and iii) expansion of the selected T cell population or generation of sufficient number of TCR modified T cells. In this review, we provide an introduction into challenges and approaches to identify neoantigens and to select the Adoptive Cell Therapy, ACT, Neoantigen, T cell, Cancer respective neoantigen-reactive T cells for use in ACT.

RNA-electroporated T cells for cancer immunotherapy

Adoptive T cell therapy has proven effective against hematologic malignancies and demonstrated efficacy against a variety of solid tumors in preclinical studies and clinical trials. Nonetheless, antitumor responses against solid tumors remain modest, highlighting the need to enhance the effectiveness of this therapy. Genetic modification of T cells with RNA has been explored to enhance T-cell antigen specificity, effector function, and migration to tumor sites, thereby potentiating antitumor immunity. This review describes the rationale for RNA-electroporated T cell modifications and provides an overview of their applications in preclinical and clinical investigations for the treatment of hematologic malignancies and solid tumors.

Immune-based therapies for metastatic prostate cancer: an update

Prostate cancer (PC) is a common malignancy among elderly males and is noncurable once it becomes metastatic. In recent years, a number of antigen-delivery systems have emerged as viable and promising immunotherapeutic agents against PC. The approval of sipuleucel-T by the US FDA for the treatment of males with asymptomatic or minimally symptomatic castrate resistant PC was a landmark in cancer immunotherapy, making this the first approved immunotherapeutic. A number of vaccines are under clinical investigation, each having its own set of advantages and disadvantages. Here, we discuss the basic technologies underlying these different delivery modes, we discuss the completed and current human clinical trials, as well as the use of vaccines in combination with immune checkpoint inhibitors.

CAR T-cell bioengineering: Single variable domain of heavy chain antibody targeted CARs

Redirecting the recognition specificity of T lymphocytes to designated tumour cell surface antigens by transferring chimeric antigen receptor (CAR) genes is becoming an effective strategy to combat cancer. Today, CAR T-cell therapy has proven successful in the treatment of haematological malignancies and the first CD19 CAR T-cell products has already entered the market. This success is expanding CAR design for broader malignancies including solid tumours. Nevertheless, CARs such as those built on antigen-specific single chain antibody variable fragment (scFv) may induce some adverse effects. Here, we briefly review CAR T-cell bioengineering and discuss selected important initiatives for improved T-cell reprogramming, function and safety. In this respect, we further elaborate on unconventional CARs structured on single variable domain of heavy chain (VHH) antibodies (single-domain antibodies) as an alternative to scFv, because of their interesting immunological and physicochemical characteristics and unique structure, which shows a high degree of homology with human VH3 gene family.

Prospective Immunophenotyping of CD8+ T Cells and Associated Clinical Outcomes of Patients With Oligometastatic Prostate Cancer Treated With Metastasis-Directed SBRT

PURPOSE

This study examined the effects of metastasis-directed stereotactic body radiation therapy (mdSBRT) on CD8⁺ T-cell subpopulations and correlated post-mdSBRT immunophenotypic responses with clinical outcomes in patients with oligometastatic prostate cancer (OPCa).

METHODS AND MATERIALS

Peripheral blood mononuclear cells were prospectively isolated from 37 patients with OPCa (≤3 metastases) who were treated with mdSBRT. Immunophenotyping identified circulating CD8⁺ T-cell subpopulations, including tumor-reactive (T_TR), effector memory, central memory (T_CM), effector, and naïve T cells from samples collected before and after mdSBRT. Univariate Cox proportional hazards regression was used to assess whether changes in these T-cell subpopulations were potential risk factors for death and/or progression. The Kaplan-Meier method was used for survival. Cumulative incidence for progression and new distant metastasis weas estimated, considering death as a competing risk.

RESULTS

Median follow-up was 39 months (interquartile range, 34-43). Overall survival at 3 years was 78.2%. Cumulative incidence for local progression and new distant metastasis at 3 years was 16.5% and 67.6%, respectively. Between baseline and day 14 after mdSBRT, an increase in the T_CM cell subpopulation was associated with the risk of death (hazard ratio, 1.22 [95% confidence interval, 1.02-1.47]; P = .033), and an increase in the T_TR cell subpopulation was protective against the risk of local progression (hazard ratio, 0.80 [95% confidence interval, 0.65-0.98]; P = .032).

CONCLUSIONS

An increase in the T_TR cell subpopulation was protective against the risk of disease progression, and an increase in the T_CM cell subpopulation was associated with the risk of death in patients with OPCa treated with mdSBRT. Disease control may be further improved by better understanding the CD8⁺ T-cell subpopulations and by enhancing their antitumor effect.

Combination epidermal growth factor receptor variant III peptide-pulsed dendritic cell vaccine with miR-326 results in enhanced killing on EGFRvIII-positive cells

The mutant Type III variant of epidermal growth factor receptor (EGFRvIII) is present in approximately one-third of glioblastoma (GBM) patients. It is never found in normal tissues; therefore, it represents a candidate target for GBM immunotherapy. PEPvIII, a peptide sequence from EGFRvIII, was designed to represent a target of glioma and is presented by MHC I/II complexes. Dendritic cells (DCs) have great potential to sensitize CD4+ T and CD8+ T cells to precisely target and eradicate GBM. Here, we show that PEPvIII could be loaded by DCs and presented to T lymphocytes, especially PEPvIII-specific CTLs, to precisely kill U87-EGFRvIII cells. In addition to inhibiting proliferation and inducing the apoptosis of U87-EGFRvIII cells, miR-326 also reduced the expression of TGF-β1 in the tumour environment, resulting in improved efficacy of T cell activation and killing via suppressing the SMO/Gli2 axis, which at least partially reversed the immunosuppressive environment. Furthermore, combining the EGFRvIII-DC vaccine with miR-326 was more effective in killing U87-EGFRvIII cells compared with the administration of either one alone. This finding suggested that a DC-based vaccine combined with miR-326 may induce more powerful anti-tumour immunity against GBM cells that express a relevant antigen, which provides a promising approach for GBM immunotherapy.

Targeting tumor microenvironment to curb chemoresistance via novel drug delivery strategies

INTRODUCTION

Tumor is a heterogeneous mass of malignant cells co-existing with non-malignant cells. This co-existence evolves from the initial developmental stages of the tumor and is one of the hallmarks of cancer providing a protumorigenic niche known as tumor microenvironment (TME). Proliferation, invasiveness, metastatic potential and maintenance of stemness through cross-talk between tumors and its stroma forms the basis of TME.

AREAS COVERED

The article highlights the developmental phases of a tumor from dysplasia to the formation of clinically detectable tumors. The authors discuss the mechanistic stages involved in the formation of TME and its contribution in tumor outgrowth and chemoresistance. The authors have reviewed various approaches for targeting TME and its hallmarks along with their advantages and pitfalls. The authors also highlight cancer stem cells (CSCs) that are resistant to chemotherapeutics and thus a primary reason for tumor recurrence thereby, posing a challenge for the oncologists.

EXPERT OPINION

Recent understanding of the cellular and molecular mechanisms involved in acquired chemoresistance has enabled scientists to target the tumor niche and TME and modulate and/or disrupt this communication leading to the transformation from a tumor-supportive niche environment to a tumor-non-supporting environment and give synergistic results towards an effective management of cancer.

The Present and Future of Biomarkers in Prostate Cancer: Proteomics, Genomics, and Immunology Advancements

Prostate cancer (PC) is the second most common form of cancer in men worldwide. Biomarkers have emerged as essential tools for treatment and assessment since the variability of disease behavior, the cost and diversity of treatments, and the related impairment of quality of life have given rise to a need for a personalized approach. High-throughput technology platforms in proteomics and genomics have accelerated the development of biomarkers. Furthermore, recent successes of several new agents in PC, including immunotherapy, have stimulated the search for predictors of response and resistance and have improved the understanding of the biological mechanisms at work. This review provides an overview of currently established biomarkers in PC, as well as a selection of the most promising biomarkers within these particular fields of development.

Direct Delivery of Antigens to Dendritic Cells via Antibodies Specific for Endocytic Receptors as a Promising Strategy for Future Therapies

Dendritic cells (DCs) are the most potent professional antigen presenting cells and are therefore indispensable for the control of immunity. The technique of antibody mediated antigen targeting to DC subsets has been the basis of intense research for more than a decade. Many murine studies have utilized this approach of antigen delivery to various kinds of endocytic receptors of DCs both in vitro and in vivo. Today, it is widely accepted that different DC subsets are important for the induction of select immune responses. Nevertheless, many questions still remain to be answered, such as the actual influence of the targeted receptor on the initiation of the immune response to the delivered antigen. Further efforts to better understand the induction of antigen-specific immune responses will support the transfer of this knowledge into novel treatment strategies for human diseases. In this review, we will discuss the state-of-the-art aspects of the basic principles of antibody mediated antigen targeting approaches. A table will also provide a broad overview of the latest studies using antigen targeting including addressed DC subset, targeted receptors, outcome, and applied coupling techniques.

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.

Novel role of hematopoietic stem cells in immunologic rejection of malignant gliomas

Adoptive cellular therapy (ACT) after lymphodepletive conditioning can induce dramatic clinical responses, but this approach has been largely limited to melanoma due to a lack of reliable methods for expanding tumor-specific lymphocytes from the majority of other solid cancers. We have employed tumor RNA-pulsed dendritic cells (DCs) to reliably expand CD4⁺ and CD8⁺ tumor-reactive T lymphocytes for curative ACT in a highly-invasive, chemotherapy- and radiation-resistant malignant glioma model. Curative treatment of established intracranial tumors involved a synergistic interaction between myeloablative (MA) conditioning, adoptively transferred tumor-specific T cells, and tumor RNA-pulsed DC vaccines. Hematopoietic stem cells (HSCs), administered for salvage from MA conditioning, rapidly migrated to areas of intracranial tumor growth and facilitated the recruitment of tumor-specific lymphocytes through HSC-elaborated chemokines and enhanced immunologic rejection of intracranial tumors during ACT. Furthermore, HSC transplant under non-myeloablative (NMA) conditions also enhanced immunologic tumor rejection, indicating a novel role for the use of HSCs in the immunologic treatment of malignant gliomas and possibly other solid tumors.

Dendritic cells transfected with hepatocellular carcinoma (HCC) total RNA induce specific immune responses against HCC in vitro and in vivo

BACKGROUND

Immunotherapy is an effective method for preventing metastasis and recurrence of carcinoma. Hepatocellular carcinoma (HCC) is a common malignancy with a high rate of recurrence, and has not successfully been introduced to immunotherapy.

METHODS

Peripheral blood mononuclear cells were isolated from whole blood of HCC patients and stimulated to transform into dendritic cells (DCs). These DCs were then transfected with RNA extracted from HepG-2 hepatoma cells to induce expression of specific antigens.

RESULTS

The transfected DCs stimulated T lymphocytes to produce cytotoxic T lymphocytes, which specifically attacked HepG-2 cells. Injection of T lymphocytes from HCC patients and transfected DCs into severe combined immunodeficiency mice limited the growth of HepG-2 tumors.

CONCLUSION

A specific immune response against hepatoma can be generated in vivo by administering DCs transfected with RNA from a specific tumor. This method may have therapeutic application in humans to reduce recurrence of HCC.

Generation of CTL responses against pancreatic cancer in vitro using dendritic cells co-transfected with MUC4 and survivin RNA

Pancreatic cancer (PC) is one of the most devastating human malignancies without effective therapies. Tumor vaccine based on RNA-transfected dendritic cells (DCs) has emerged as an alternative therapeutic approach for a variety of human cancers including advanced PC. In the present study we compared the cytotoxic T lymphocyte (CTL) responses against PC cells in vitro, which were induced by DCs co-transfected with two mRNAs of tumor associated-antigens (TAA) MUC4 and survivin, versus DCs transfected with a single mRNA encoding either MUC4 or survivin. DCs co-transfected with two TAA mRNAs were found to induce stronger CTL responses against PC target cells in vitro, compared with the DCs transfected with a single mRNA. Moreover, the antigen-specific CTL responses were MHC class I-restricted. These results provide an experimental foundation for further clinical investigations of DC vaccines encoding multiple TAA epitopes for metastatic PC.

Melanoma immunotherapy using mature DCs expressing the constitutive proteasome

BACKGROUND

Many cancers, including melanoma, exclusively express constitutive proteasomes (cPs) and are unable to express immunoproteasomes (iPs). In contrast, mature DCs used for immunotherapy exclusively express iPs. Since proteasomes generate peptides presented by HLA class I molecules, we hypothesized that mature melanoma antigen-loaded DCs engineered to process antigens through cPs would be superior inducers of antimelanoma immunity in vivo.

METHODS

Subjects with metastatic melanoma were vaccinated with mature DCs transfected with RNAs encoding melanoma antigens MART1, MAGE-3, gp100, and tyrosinase. These DCs were derived from monocytes that were untransfected (Arm A; n = 4), transfected with control siRNA (Arm B; n = 3), or transfected with siRNAs targeting the 3 inducible iP subunits (Arm C; n = 5).

RESULTS

Vaccination stimulated antigen-specific T cell responses in all subjects, which peaked after 3-4 vaccinations, but remained elevated in Arm C subjects. Also in Arm C, circulating melanoma cell levels (as detected by quantitative PCR) fell, and T cell lytic activity against autologous melanoma was induced. In HLA-A2⁺ subjects, CD8⁺ T cells that bound tetramers loaded with cP-derived melanoma antigenic peptides were found in the peripheral blood only in Arm C subjects. Of 2 subjects with active disease (both in Arm C), one had a partial clinical response, while the other, who exhibited diffuse dermal and soft tissue metastases, had a complete response.

CONCLUSION

These results suggest that the efficacy of melanoma DC-based immunotherapy is enhanced when tumor antigen-loaded DCs used for vaccination express cPs.

TRIAL REGISTRATION

Clinicaltrials.gov NCT00672542.

FUNDING

Duke Clinical Research Institute/Duke Translational Medicine Institute, Duke Melanoma Consortium, and Duke University Department of Surgery.

Evaluation of RNA Amplification Methods to Improve DC Immunotherapy Antigen Presentation and Immune Response

Dendritic cells (DCs) transfected with total amplified tumor cell RNA have the potential to induce broad antitumor immune responses. However, analytical methods required for quantitatively assessing the integrity, fidelity, and functionality of the amplified RNA are lacking. We have developed a series of assays including gel electrophoresis, northern blot, capping efficiency, and microarray analysis to determine integrity and fidelity and a model system to assess functionality after transfection into human DCs. We employed these tools to demonstrate that modifications to our previously reported total cellular RNA amplification process including the use of the Fast Start High Fidelity (FSHF) PCR enzyme, T7 Powerswitch primer, post-transcriptional capping and incorporation of a type 1 cap result in amplification of longer transcripts, greater translational competence, and a higher fidelity representation of the starting total RNA population. To study the properties of amplified RNA after transfection into human DCs, we measured protein expression levels of defined antigens coamplified with the starting total RNA populations and measured antigen-specific T cell expansion in autologous DC-T cell co-cultured in vitro. We conclude from these analyses that the improved RNA amplification process results in superior protein expression levels and a greater capacity of the transfected DCs to induce multifunctional antigen-specific memory T cells.Molecular Therapy-Nucleic Acids (2013) 2, e91; doi:10.1038/mtna.2013.18; published online 7 May 2013.

Analysis of survivin-specific T cells in breast cancer patients using human DCs engineered with survivin mRNA

The observation that dendritic cells (DCs) charged with tumor-associated antigens (TAAs) is a potent strategy to elicit protective immunity in tumor-bearings hosts has prompted extensive testing of DCs as cellular adjuvant in cancer vaccines. To improve the clinical development of DC-based cancer vaccines, it may be beneficial to analyze preexistent immunity against TAAs in cancer patients because it may be easier to expand a memory pool of T cells compared to generating new immunity. Recent research shows that engineering DCs to synthesize tumor epitopes endogenously by transfecting DCs with mRNA-encoding TAAs are particular effective in stimulating robust T-responses in vitro and in vivo. In this chapter, we describe the methodology to analyze for survivin-specific T cells in breast cancer patients using human DCs engineered with survivin mRNA.

Genetically engineered T cells bearing chimeric nanoconstructed receptors harboring TAG-72-specific camelid single domain antibodies as targeting agents

Despite the preclinical success of adoptive therapy with T cells bearing chimeric nanoconstructed antigen receptors (CARs), certain limitations of this therapeutic approach such as the immunogenicity of the antigen binding domain, the emergence of tumor cell escape variants and the blocking capacity of soluble antigen still remain. Here, we address these issues using a novel CAR binding moiety based on the oligoclonal camelid single domain antibodies. A unique set of 13 single domain antibodies were selected from an immunized camel phage library based on their target specificity and binding affinity. A combination of these single domain antibodies was used to generate four tumor associated glycoprotein (TAG-72)-specific CARs harboring an identical antigen binding site, but with different signaling and spacer domains. Although all four CARs were functionally active against the TAG-72 expressing tumor cells, the combination of CD3ζ, OX40, CD28 as well as the CH3-CH2-hinge-hinge domains most efficiently triggered T cell activation. Importantly, CAR mediated functions were not blocked by the soluble TAG-72 antigen at a supraphysiological concentration. Our approach may have the potential to reverse multiple tumor immune evasion mechanisms, avoid CAR immunogenicity, and overcome problems in cancer gene therapy with engineered nanoconstructs.

Down regulation of CD24 and HER-2/neu in breast carcinoma cells by activated human dendritic cell. Role of STAT3

Human dendritic cells (DCs) stimulated with cytokines and LPS down regulate the expression of proto-oncogene HER-2/neu and GPI linked protein CD24 in breast cancer cell lines. We demonstrated that naïve DC from human peripheral blood, when stimulated with IFN-γ, IL-15 or LPS reduces the expression of HER-2/neu and CD24, via activation of TNF-α. Pretreatment of tumor cells with STAT3 specific inhibitors or knocking down of STAT3 by SiRNA makes the tumor cell more susceptible to apoptosis and DC mediated inhibition of both CD24 and HER-2/neu. Thus DC could acts as an inhibitory regulator in suppressing oncogene and prevention of metastasis.

Human dendritic cells transfected with amplified MUC1 mRNA stimulate cytotoxic T lymphocyte responses against pancreatic cancer in vitro

BACKGROUND AND AIM

Mucin (MUC) 1 is an epithelial cell glycoprotein that is aberrantly overexpressed in many adenocarcinomas, including pancreatic cancer (PC), providing an ideal tumor-associated antigen and target for immunotherapy. In this study, we investigated whether the cytotoxic T lymphocytes (CTLs) induced by dendritic cells (DCs) transfected with amplified MUC1 mRNA could respond against PC in vitro.

METHODS

Amplified mRNA encoding MUC1 were transfected into DCs using electroporation with an optimized setting and the MUC1 expression were evaluated by quantitative real-time polymerase chain reaction and Western blot. The MUC1 specific CTL responses were measured using the standard chromium 51 (51Cr)-release assays and the interferon-γ release assay.

RESULTS

Dendritic cells could be transfected with amplified MUC1 mRNA efficiently. The transfected DCs were remarkably effective in stimulating MUC1-specific CTL responses in vitro. The function of MUC1 specific CTLs, induced by MUC1 mRNA-transfected DCs, was restricted by major histocompatibility complex (MHC) class I antigen presentation.

CONCLUSION

The CTL responses stimulated by DCs transfected with MUC1 mRNA could only recognize and lyse HLA-A2+/MUC1+ PC and other target cells under restriction by MHC class I-specific antigen presentation, providing a preclinical rationale for using MUC1 as a target structure for immunotherapeutic strategies against PC.

Telomerase as a tumor-associated antigen for cancer immunotherapy

Telomerase reverse transcriptase hTERT is an attractive target for cancer immunotherapy given its broad expression in human tumors and its demonstrated immunogenicity. Human and murine model systems demonstrate that CD8(+) cytotoxic T-lymphocytes (CTL) and CD4(+) helper T-lymphocytes can recognize dominant epitopes derived from TERT. CTL kill TERT-positive tumor cells of multiple histologies, although there is some disagreement regarding the level of processing and presentation of certain TERT peptides within the context of MHC class I molecules. CTL recognizing modified, low-affinity cryptic TERT epitopes have also been generated that protect against tumor challenge in a murine model. Several phase I clinical trials testing hTERT as a cancer vaccine target have shown the induction of T-cell immune responses but minimal toxicities, including bone marrow toxicity, in patients with multiple types of cancer. Several studies report some patients experiencing clinical benefit, including partial tumor regression, providing further encouragement for hTERT as broadly applicable target for cancer immunotherapy.

Enhanced antitumor effects by the coculture of allotumor RNA-pulsed dendritic cells with autologous cytokine-induced killer cells on hormone-refractory prostate cancer

In this study, we evaluated antitumor effects of allotumour RNA-transfected dendritic cells (DCs) cocultured with autologous cytokine-induced killer cells (CIKs) on hormone-refractory prostate cancer. The cocultured cells enhanced prostate cancer cytolysis from 26% (CIKs-induced cytolysis) to 80.8%. They also increased the productions of CD4(+) Th1 (IFN-γ(+)IL-4(-), 55.52%) and CD8(+) T (IFN-γ(+), 69.59%) cells determined by intracellular cytokines IFN-γ /IL-4 staining and reduced the rate of CD4(+) CD25(+) cells from 18.72% (in CIKs) to 9.72%. The cocultured cells significantly inhibited tumor growth in SCID mouse and induced cancer cells necrosis and apoptosis. Our study indicates that tumor RNA-pulsed DCs cocultured with autologous CIKs significantly enhance antitumor immunity, which can be induced by increased CD4(+) Th1 and CD8(+) T cells and decreased CD4(+)CD25(+) regulatory T (T(reg)) cells. This provides a potential immunotherapy strategy for HRPC.

Engineering dendritic cells to enhance cancer immunotherapy

Cancer immunotherapy aims to establish immune-mediated control of tumor growth by priming T-cell responses to target tumor-associated antigens. Three signals are required for T-cell activation: (i) presentation of cognate antigen in self MHC molecules; (ii) costimulation by membrane-bound receptor-ligand pairs; and (iii) soluble factors to direct polarization of the ensuing immune response. The ability of dendritic cells (DCs) to provide all three signals required for T-cell activation makes them an ideal cancer vaccine platform. Several strategies have been developed to enhance and control antigen presentation, costimulation, and cytokine production. In this review, we discuss progress toward developing DC-based cancer vaccines by genetic modification using RNA, DNA, and recombinant viruses. Furthermore, the ability of DC-based vaccines to activate natural killer (NK) and B-cells, and the impact of gene modification strategies on these populations is described. Clinical trials using gene-modified DCs have shown modest results, therefore, further considerations for DC manipulation to enhance their clinical efficacy are also discussed.

Dendritic cell-tumor cell hybrids and immunotherapy: what's next?

Dendritic cells (DC) are professional antigen-presenting cells currently being used as a cellular adjuvant in cancer immunotherapy strategies. Unfortunately, DC-based vaccines have not demonstrated spectacular clinical results. DC loading with tumor antigens and DC differentiation and activation still require optimization. An alternative technique for providing antigens to DC consists of the direct fusion of dendritic cells with tumor cells. These resulting hybrid cells may express both major histocompatibility complex (MHC) class I and II molecules associated with tumor antigens and the appropriate co-stimulatory molecules required for T-cell activation. Initially tested in animal models, this approach has now been evaluated in clinical trials, although with limited success. We summarize and discuss the results from the animal studies and first clinical trials. We also present a new approach to inducing hybrid formation by expression of viral fusogenic membrane glycoproteins.

An autologous dendritic cell canine mammary tumor hybrid-cell fusion vaccine

Mammary cancer is among the most prevalent canine tumors and frequently resulting in death due to metastatic disease that is highly homologous to human breast cancer. Most canine tumors fail to raise effective immune reactions yet, some spontaneous remissions do occur. Hybrid canine dendritic cell-tumor cell fusion vaccines were designed to enhance antigen presentation and tumor immune recognition. Peripheral blood-derived autologous dendritic cell enriched populations were isolated from dogs based on CD11c(+) expression and fused with canine mammary tumor (CMT) cells for vaccination of laboratory Beagles. These hybrid cells were injected into popliteal lymph nodes of normal dogs, guided by ultrasound, and included CpG-oligonucleotide adjuvants. Three rounds of vaccination were delivered. Significant IgG responses were observed in all vaccinated dogs compared to vehicle-injected controls. Canine IgG antibodies recognized shared CMT antigens as was demonstrated by IgG-recognition of three unrelated/independently derived CMT cell lines, and recognition of freshly isolated, unrelated, primary biopsy-derived CMT cells. A bias toward an IgG2 isotype response was observed after two vaccinations in most dogs. Neither significant cytotoxic T cell responses were detected, nor adverse or side-effects due to vaccination or due to the induced immune responses noted. These data provide proof-of-principle for this cancer vaccine strategy and demonstrate the presence of shared CMT antigens that promote immune recognition of mammary cancer.

Induction of cytotoxic T lymphocytes primed with tumor RNA-loaded dendritic cells in esophageal squamous cell carcinoma: preliminary step for DC vaccine design

Background

Dendritic Cells (DC) are potent antigen presenting cells with the ability to prime naïve T cells and convert them to cytotoxic T-lymphocytes (CTL). We evaluated the capability of autologous DCs transfected with total tumor and normal RNA to induce cytotoxic CTL as the preliminary step to design a DC-based vaccine in the esophageal squamous cell carcinoma (ESCC).

Methods

Monocytes-derived DCs were electroporated with either total tumor RNA or normal RNA. T cells were then primed with tumor RNA transfected DCs and lytic effects of the generated CTL were measured with Cytotoxicity assay and IFN-γ Release Elispot assay.

Results

Cytotoxicity was induced against DCs loaded with tumoral RNA (%24.8 ± 5.2 SEM) while in normal RNA-loaded DCs, it was minimal (%6.1 ± 2.4 SEM) and significantly lower (p < 0.05). INF-γ secretion was more than 2-folds higher in tumoral RNA-loaded DCs when compared with normal RNA-loaded DCs (p < 0.05).

Conclusion

Electroporating DCs with tumor RNA generated tumor antigen presenting cells which in turn enhanced cytotoxic effects of the T cells against ESCC. This may be a useful autologous ex vivo screening tool for confirming the lytic effects of primed T cells on tumors and evaluate probable further adverse effects on noncancerous tissues. These data provide crucial preliminary information to establish a total tumor RNA-pulsed DC vaccine therapy of ESCC.

Immunotherapy of cancer with dendritic cells loaded with tumor antigens and activated through mRNA electroporation

Since decades, the main goal of tumor immunologists has been to increase the capacity of the immune system to mediate tumor regression. Considerable progress has been made in enhancing the efficacy of therapeutic anticancer vaccines. First, dendritic cells (DCs) have been identified as the key players in orchestrating primary immune responses. A better understanding of their biology and the development of procedures to generate vast amounts of DCs in vitro have accelerated the development of potent immunotherapeutic strategies for cancer. Second, tumor-associated antigens have been identified which are either selectively or preferentially expressed by tumor cells and can be recognized by the immune system. Finally, several studies have been performed on the genetic modification of DCs with tumor antigens. In this regard, loading the DCs with mRNA, which enables them to produce/process and present the tumor antigens themselves, has emerged as a promising strategy. Here, we will first overview the different aspects that must be taken into account when generating an mRNA-based DC vaccine and the published clinical studies exploiting mRNA-loaded DCs. Second, we will give a detailed description of a novel procedure to generate a vaccine consisting of tumor antigen-expressing dendritic cells with an in vitro superior capacity to induce anti-tumor immune responses. Here, immature DCs are electroporated with mRNAs encoding a tumor antigen, CD40 ligand (CD40L), CD70, and constitutively active (caTLR4) to generate mature antigen-presenting DCs.

Dendritic cell-based cancer immunotherapies

Because of their unique role in linking the innate and adaptive immune systems, dendritic cells (DCs) have been a logical focus for novel immunotherapies. However, strategies employing active immunization with ex vivo generated and antigen-pulsed DCs have shown limited efficacy in clinical trials. These past approaches did not take into account the complex interactions between cells of the innate immune system and DCs during DC maturation, antigen processing, and presentation to naïve T cells. By better understanding the natural sequence of events occurring in vivo during an effective immune response, we can tailor antitumor immunotherapeutic strategies to augment aspects of this response from the activation of innate immune cells to antigen uptake and DC maturation to priming of naïve T cells and, ultimately, to the establishment of antitumor immunity. Current DC vaccination strategies utilize a number of methods to recapitulate the cascade of events that culminate in a protective antitumor immune response.

Strategies for Successful Vaccination against Hepatocellular Carcinoma

Current therapies against hepatocellular carcinoma (HCC) are not curative in the majority of patients. In the past, immunotherapy approaches aimed to non-specifically stimulate immune response were quite ineffective. New treatments based on stimulation of specific anti-tumor immune response are currently proposed and appear more promising. Tumor-specific antigens identified in HCC demonstrated immunogenicity both in preclinical and clinical trials. Effectiveness in animal studies raised interest in the clinical applicability of non-specific adoptive immunotherapy that prevented disease recurrence after tumor resection. Dendritic cell (DC)-based tumor vaccines achieved encouraging results, and cellular vaccines based on DCs have already entered clinical trials. Preventive and therapeutic DNA vaccination have been proposed, all based on tumor-associated antigens (TAAs), either modified or not, an example being alpha-fetoprotein (AFP). The concomitant expression of co-stimulatory molecules and cytokines was used to increase tumor immunogenicity. Syngeneic or nude mice models indicated that immunotherapy for HCC could stimulate an anti-tumor T-cell response leading to clinical benefit devoid of significant toxicity. The use of DNA-based vaccination raises exciting possibilities in preventing HCC in high-risk individuals such as those with cirrhosis. Novel immunotherapy strategies may contribute in the future to prevention and treatment of HCC.

The use of gamma-irradiation and ultraviolet-irradiation in the preparation of human melanoma cells for use in autologous whole-cell vaccines

Background

Human cancer vaccines incorporating autologous tumor cells carry a risk of implantation and subsequent metastasis of viable tumor cells into the patient who is being treated. Despite the fact that the melanoma cell preparations used in a recent vaccine trial (Mel37) were gamma-irradiated (200 Gy), approximately 25% of the preparations failed quality control release criteria which required that the irradiated cells incorporate ³H-thymidine at no more than 5% the level seen in the non-irradiated cells. We have, therefore, investigated ultraviolet (UV)-irradiation as a possible adjunct to, or replacement for gamma-irradiation.

Methods

Melanoma cells were gamma- and/or UV-irradiated. ³H-thymidine uptake was used to assess proliferation of the treated and untreated cells. Caspase-3 activity and DNA fragmentation were measured as indicators of apoptosis. Immunohistochemistry and Western blot analysis was used to assess antigen expression.

Results

UV-irradiation, either alone or in combination with gamma-irradiation, proved to be extremely effective in controlling the proliferation of melanoma cells. In contrast to gamma-irradiation, UV-irradiation was also capable of inducing significant levels of apoptosis. UV-irradiation, but not gamma-irradiation, was associated with the loss of tyrosinase expression. Neither form of radiation affected the expression of gp100, MART-1/MelanA, or S100.

Conclusion

These results indicate that UV-irradiation may increase the safety of autologous melanoma vaccines, although it may do so at the expense of altering the antigenic profile of the irradiated tumor cells.

Induction of T-cell responses against cutaneous T-cell lymphomas ex vivo by autologous dendritic cells transfected with amplified tumor mRNA

Sézary syndrome (SzS), the leukemic variant of cutaneous T-cell lymphomas, is incurable. Dendritic cells (DCs) transfected with tumor mRNA can stimulate antitumor immunity in certain cancer patients. In this study, we determined whether mRNAs from Sézary cells could be used for loading DCs and stimulating antitumor immunity. Autologous DCs were generated from monocytes of the peripheral blood from 10 patients with SzS. Total RNA was extracted from Sézary cells and amplified by T7 in vitro transcription. The induction of antitumor IFN-gamma and granzyme B (GrB)-producing cytotoxic T lymphocytes (CTL) by RNA-transfected DCs was determined by ELISPOT assays. We found that IFN-gamma was required for IL-12p70 production by monocyte-derived DCs from SzS. The oncogenic transcription factor Twist and the tyrosine kinase receptor EphA4 were expressed in total RNA from Sézary cells and the paired amplified mRNAs. RNA-transfected DCs induced antitumor IFN-gamma-producing CTLs in 7 of 10 subjects and GrB-producing CTLs in 6 of 9 subjects. Both CD3+CD8+ T cells and CD4+CD25+ T cells were expanded without induction of regulatory T cells. These data support the concept of using tumor mRNA for a vaccine strategy that requires small amounts of tumor cells without need for specific antigens in patients with SzS.

DNA fusion gene vaccination mobilizes effective anti-leukemic cytotoxic T lymphocytes from a tolerized repertoire

The majority of known human tumor-associated antigens derive from non-mutated self proteins. T cell tolerance, essential to prevent autoimmunity, must therefore be cautiously circumvented to generate cytotoxic T cell responses against these targets. Our strategy uses DNA fusion vaccines to activate high levels of peptide-specific CTL. Key foreign sequences from tetanus toxin activate tolerance-breaking CD4(+) T cell help. Candidate MHC class I-binding tumor peptide sequences are fused to the C terminus for optimal processing and presentation. To model performance against a leukemia-associated antigen in a tolerized setting, we constructed a fusion vaccine encoding an immunodominant CTL epitope derived from Friend murine leukemia virus gag protein (FMuLV(gag)) and vaccinated tolerant FMuLV(gag)-transgenic (gag-Tg) mice. Vaccination with the construct induced epitope-specific IFN-gamma-producing CD8(+) T cells in normal and gag-Tg mice. The frequency and avidity of activated cells were reduced in gag-Tg mice, and no autoimmune injury resulted. However, these CD8(+) T cells did exhibit gag-specific cytotoxicity in vitro and in vivo. Also, epitope-specific CTL killed FBL-3 leukemia cells expressing endogenous FMuLV(gag) antigen and protected against leukemia challenge in vivo. These results demonstrate a simple strategy to engage anti-microbial T cell help to activate epitope-specific polyclonal CD8(+) T cell responses from a residual tolerized repertoire.

High-level antigen expression and sustained antigen presentation in dendritic cells nucleofected with wild-type viral mRNA but not DNA

Dendritic cells (DC) are potent antigen-presenting cells that hold promise as cell-based therapeutic vaccines for infectious diseases and cancer. Ideally, DC would be engineered to express autologous viral or tumor antigens to ensure the presentation of relevant antigens to host T cells in vivo; however, expression of wild-type viral genes in primary cell lines can be problematic. Nucleofection is an effective means of delivering transgenes to primary cell lines, but its use in transfecting DNA or mRNA into DC has not been widely investigated. We show that nucleofection is a superior means of transfecting human and monkey monocyte-derived DC with DNA and mRNA compared to lipofection and conventional electroporation. However, the delivery of DNA and mRNA had significantly different outcomes in transfected DC. DC nucleofected with DNA encoding green fluorescent protein (GFP) had poor antigen expression and viability and were refractory to maturation with CD40 ligand. In contrast, >90% of DC expressed uniform and high levels of GFP from 3 h to 96 h postnucleofection with mRNA while maintaining a normal maturation response to CD40 ligation. Monkey DC nucleofected with wild-type, non-codon-optimized mRNA encoding simian immunodeficiency virus Gag stimulated robust antigen-specific effector T-cell responses at 24 h and 48 h postnucleofection, reflecting sustained antigen presentation in transfected DC, whereas no detectable T-cell response was noted when DC were nucleofected with DNA encoding the same Gag sequence. These data indicate that mRNA nucleofection may be an optimal means of transfecting DC with autologous tumor or viral antigen for DC-based immunotherapy.

Cancer vaccines: accomplishments and challenges

Advancements in knowledge in diverse fields of science, including genetics, cell biology, molecular biology and biochemistry, have shed light on the origins of cancer and cell intrinsic properties that allow it to grow, invade and metastasize. Many therapies currently in use or under development are based on this knowledge. Advances in immunology, on the other hand, have shed light on how the host responds to these malignant properties of cancer. Based on that knowledge, immunotherapy, in particular vaccines directed at improving the host response against cancer, is being developed as an alternative therapeutic approach. In this review, we address main issues that have driven development of cancer vaccines and the challenges that have been met and/or are anticipated.

An allogeneic hybrid-cell fusion vaccine against canine mammary cancer

Mammary cancer is among the most prevalent of canine tumors frequently resulting in death due to metastatic disease. Most tumors fail to raise an effective immune reaction making improving immune recognition a priority. Hybrid-cell fusion strategies have been employed to load dendritic cell populations with tumor cell antigens to stimulate immune recognition; however, recovery, heterogeneity and quality of primary cells from patients present enormous challenges. We employed allogeneic cell lines to develop an improved hybrid-cell fusion strategy and evaluated immune reactions in normal laboratory beagles. Such a strategy relies on enhanced immune recognition of allogeneic tumor cell antigens by antigen presenting cells. Optimized PEG-promoted fusions between uniquely stained canine mammary tumor CMT12 or CMT28 cells and a dendritic cell-like DH82 cell fusion partner resulted in greater than 40% hybrid-cell fusion populations by flow cytometry and fluorescence microscopy. Hybrid-cell fusions were delivered by direct ultrasound guided injection into popliteal lymph nodes of laboratory beagles. Only hybrid-cell fusions provided statistically significant enhancement of cell-mediated immunity ((51)Cr-release assay) compared to innate reactions in naïve vehicle injected dogs while dogs vaccinated with either single cell component alone did not. Vaccination with hybrid-cell fusions enhanced IFN-gamma expression in sorted CD8+ and CD4+ cells but not in CD4-/CD8- cells consistent with a CTL response. Cell-mediated immune assays revealed strong reactions against matched (vaccine component) CMT cells and unmatched CMT cells indicative of an immune response to mammary cancer antigens common to both cell lines. These results provide proof of principle for development of an allogeneic vaccination strategy against canine mammary cancer.