Connective tissue growth factor linked to the E7 tumor antigen generates potent antitumor immune responses mediated by an antiapoptotic mechanism

mTOR Inhibitors Can Enhance the Anti-Tumor Effects of DNA Vaccines through Modulating Dendritic Cell Function in the Tumor Microenvironment

The life span of dendritic cells (DCs) can become short following induced activation, which is associated with metabolic transition due to the regulation of mechanistic target of rapamycin (mTOR). The purpose of this study was to investigate the potential of inhibiting mTOR to modulate DC functions for elevating the anti-tumor effects of DNA vaccines. Therefore, the influences of various inhibitors of mTOR (mTORi) on the expressions of DC maturation markers, the abilities of antigen presenting and processing of BMM-derived DCs and the tumor killing effects of E7-specific CD8⁺ T lymphocytes activated by BMM-derived DCs were in vitro examined. The anti-tumor effects of connective tissue growth factor (CTGF)/E7 DNA vaccine and/or mTORi were also in vivo analyzed. In our study, suppressive effects of mTORi on the DC maturation markers expressed on BMMCs could be reversed. The mTORi-treated mature BMM-derived DCs tended to be non-apoptotic. These mTORi-treated BMM-derived DCs could have better antigen presenting and processing abilities. The E7-specific cytotoxic CD8+ T lymphocytes could have more potent tumoricidal activity following activation of mTORi-treated BMM-derived DCs. For tumor-bearing mice, those treated with CTGF/E7 DNA vaccine and mTORi indeed can have higher percentages of mature DCs in the TME, better disease control and longer survivals. Consequently, application of mTORi can be a pharmacological approach for temporally increasing life span, antigen presenting and antigen processing of DCs to strengthen the therapeutic outcome of cancer immunotherapy.

Immune checkpoint Ab enhances the antigen-specific anti-tumor effects by modulating both dendritic cells and regulatory T lymphocytes

We determined the anti-tumor effects and possible mechanisms of an antigen-specific DNA vaccine combined with PD-1 or CTLA-4 blockade. Using the HPV16 E6/E7⁺ syngeneic mouse tumor model, we investigated whether anti-CTLA-4 antibody (Ab) or anti-PD-1 Ab increases the antigen-specific anti-tumor effects and immune response induced by CTGF/E7 chimeric DNA vaccine and the possible mechanisms. Anti-PD-1 Ab or anti-CTLA-4 Ab combined with E7-specific DNA vaccine generated more potent antigen-specific immunity, including anti-E7 Abs and the number and cytotoxic activity of E7-specific cytotoxic CD8⁺ T lymphocytes, and anti-tumor effects than E7-specific DNA vaccine alone. In addition, the number of systemic and intratumoral Tregs was lower with the anti-PD-1 or anti-CTLA-4 Ab and E7-specific DNA vaccine. Furthermore, anti-PD-1 and anti-CTLA-4 Abs could enhance the maturation and abilities of intratumoral DCs to activate E7-specific cytotoxic CD8⁺ T cells. Immune checkpoint blockade overcomes the immunosuppressive status of the tumor-microenvironment to enhance the antigen-specific immunity and anti-tumor effects generated by an antigen-specific DNA vaccine. Antigen-specific immunotherapy combined with immune checkpoint blockade can be a novel strategy in clinical cancer therapy.

Immuno-modulators enhance antigen-specific immunity and anti-tumor effects of mesothelin-specific chimeric DNA vaccine through promoting DC maturation

As a tumor antigen, mesothelin (MSLN) can be identified in various malignancies. MSLN is potential for antigen-specific cancer vaccines. We generated a novel chimeric DNA vaccine using antigen-specific connective tissue growth factor lined with MSLN (CTGF/MSLN). The anti-tumor effects of the CTGF/MSLN DNA vaccine combined with anti-CD40 Ab and toll-like receptor 3 ligand-poly(I:C) were validated in an MSLN-expressing model. CTGF/MSLN DNA with anti-CD40Ab and poly(I:C) vaccinated mice demonstrated potent anti-tumor effects with longer survival and less tumor volumes. An increase in MSLN-specific CD8⁺ T cells and anti-MSLN Ab titers was also noted in CTGF/MSLN DNA with anti-CD40Ab and poly(I:C) vaccinated mice. The CTGF/MSLN DNA vaccine combined with immuno-modulator EGCG also generated potent anti-tumor effects. Immuno-modulators could enhance the antigen-specific anti-tumor effects of CTGF/MSLN DNA vaccine through promoting the DC maturation. In addition, MSLN-specific cell-based vaccine with AAV-IL-12 and the CTGF/MSLN DNA vaccine with anti-CD40Ab/polyp(I:C) generated more potent anti-tumor effects than the other combinational regimens. The results indicate that an MSLN-specific DNA vaccine combined with immuno-modulators may be an effective immunotherapeutic strategy to control MSLN-expressing tumors including ovarian and pancreastic cancers, and malignant mesothelioma.

Therapeutic DNA Vaccines for Human Papillomavirus and Associated Diseases

Human papillomavirus (HPV) has long been recognized as the causative agent of cervical cancer. High-risk HPV types 16 and 18 alone are responsible for over 70% of all cases of cervical cancers. More recently, HPV has been identified as an etiological factor for several other forms of cancers, including oropharyngeal, anogenital, and skin. Thus, the association of HPV with these malignancies creates an opportunity to control these HPV lesions and HPV-associated malignancies through immunization. Strategies to prevent or to therapeutically treat HPV infections have been developed and are still pushing innovative boundaries. Currently, commercial prophylactic HPV vaccines are widely available, but they are not able to control established infections or lesions. As a result, there is an urgent need for the development of therapeutic HPV vaccines, to treat existing infections, and to prevent the development of HPV-associated cancers. In particular, DNA vaccination has emerged as a promising form of therapeutic HPV vaccine. DNA vaccines have great potential for the treatment of HPV infections and HPV-associated cancers due to their safety, stability, simplicity of manufacturability, and ability to induce antigen-specific immunity. This review focuses on the current state of therapeutic HPV DNA vaccines, including results from recent and ongoing clinical trials, and outlines different strategies that have been employed to improve their potencies. The continued progress and improvements made in therapeutic HPV DNA vaccine development holds great potential for innovative ways to effectively treat HPV infections and HPV-associated diseases.

Irradiation Enhances Abscopal Anti-tumor Effects of Antigen-Specific Immunotherapy through Regulating Tumor Microenvironment

Ionizing radiation therapy is a well-established method of eradicating locally advanced tumors. Here, we examined whether local RT enhanced the potency of an antigen-specific DNA vaccine, and we investigated the possible underlying mechanism. Using the HPV16 E6/E7⁺ syngeneic TC-1 tumor, we evaluated the combination of CTGF/E7 vaccination with local irradiation with regard to synergistic antigen-specific immunity and anti-tumor effects. Tumor-bearing mice treated with local RT (6 Gy twice weekly) and CTGF/E7 DNA vaccination exhibited dramatically increased numbers of E7-specific CD8⁺ cytotoxic T cell precursors, higher titers of anti-E7 Abs, and significantly reduced tumor size. The combination of local RT and CTGF/E7 vaccination also elicited abscopal effects on non-irradiated local subcutaneous and distant pulmonary metastatic tumors. Local irradiation induced the expression of high-mobility group box 1 protein (HMGB-1) in apoptotic tumor cells and stimulated dendritic cell (DC) maturation, consequently inducing antigen-specific immune responses. Additionally, local irradiation eventually increased the effector-to-suppressor cell ratio in the tumor microenvironment. Overall, local irradiation enhanced the antigen-specific immunity and anti-tumor effects on local and distant metastatic tumors generated by an antigen-specific DNA vaccine. These findings suggest that the combination of irradiation with antigen-specific immunotherapy is a promising new clinical strategy for cancer therapy.

Therapeutic Cancer Vaccines

Cancer is one of the major leading death causes of diseases. Prevention and treatment of cancer is an important way to decrease the incidence of tumorigenesis and prolong patients' lives. Subversive achievements on cancer immunotherapy have recently been paid much attention after many failures in basic and clinical researches. Based on deep analysis of genomics and proteomics of tumor antigens, a variety of cancer vaccines targeting tumor antigens have been tested in preclinical and human clinical trials. Many therapeutic cancer vaccines alone or combination with other conventional treatments for cancer obtained spectacular efficacy, indicating the tremendously potential application in clinic. With the illustration of underlying mechanisms of cancer immune regulation, valid, controllable, and persistent cancer vaccines will play important roles in cancer treatment, survival extension and relapse and cancer prevention. This chapter mainly summarizes the recent progresses and developments on cancer vaccine research and clinical application, thus exploring the existing obstacles in cancer vaccine research and promoting the efficacy of cancer vaccine.

Mesothelin-specific cell-based vaccine generates antigen-specific immunity and potent antitumor effects by combining with IL-12 immunomodulator

Ovarian cancer is a gynecologic malignancy with a high mortality rate. In the present study, we developed a novel cell-based vaccine, Meso-VAX, to generate mesothelin antigen-specific immune responses and immunotherapy against ovarian cancer. Mesothelin, a secreted protein anchored at the cell membrane, has recently been identified as a potential new tumor antigen for ovarian cancer. In this study, mice vaccinated with Meso-VAX and adeno-associated virus (AAV)-IL-12 exhibited dramatic increases in the number of mesothelin-specific CD4(+) helper and CD8(+) cytotoxic T-cell precursors, higher titers of anti-mesothelin Abs and in vitro tumor killing activity, and all of these mice were tumor-free after 60 days of tumor challenge. In addition, a significant reduction in peritoneal tumors and longer survival were noted in the mice vaccinated with Meso-VAX combined with AAV-IL-12. CD4(+) helper and CD8(+) cytotoxic T lymphocytes were essential for the antitumor effect generated by Meso-VAX combined with AAV-IL-12. The post-vaccination sera of the mice vaccinated with Meso-VAX and AAV-IL-12 also showed mesothelin-specific complement-dependent cell-mediated cytotoxicity. Our results suggest that a Meso-VAX cell-based vaccine combined with AAV-IL-12 can generate antigen-specific immunological responses and antitumor effects on ovarian cancer.

The role of CCN family genes in haematological malignancies

Haematological malignancies, although a broad range of specific disease types, continue to show considerable overlap in classification, and patients are treated using similar chemotherapy regimes. In this review we look at the role of the CCN family of matricellular proteins and indicate their role in nine haematological malignancies including both myeloid and lymphoid neoplasms. The potential for further haematological neoplasms with CCN family associations is argued by summarising the demonstrated role of CCN family genes in the differentiation of haematopoietic stem cells (HSC) and mesenchymal stem cells. The expanding field of knowledge encompassing CCN family genes and cancers of the HSC-lineage highlights the importance of extracellular matrix-interactions in both normal physiology and tumorigenesis of the blood, bone marrow and lymph nodes.

Fusion protein vaccines targeting two tumor antigens generate synergistic anti-tumor effects

Introduction

Human papillomavirus (HPV) has been consistently implicated in causing several kinds of malignancies, and two HPV oncogenes, E6 and E7, represent two potential target antigens for cancer vaccines. We developed two fusion protein vaccines, PE(ΔIII)/E6 and PE(ΔIII)/E7 by targeting these two tumor antigens to test whether a combination of two fusion proteins can generate more potent anti-tumor effects than a single fusion protein.

Materials and Methods

Invivo antitumor effects including preventive, therapeutic, and antibody depletion experiments were performed. Invitro assays including intracellular cytokine staining and ELISA for Ab responses were also performed.

Results

PE(ΔIII)/E6+PE(ΔIII)/E7 generated both stronger E6 and E7-specific immunity. Only 60% of the tumor protective effect was observed in the PE(ΔIII)/E6 group compared to 100% in the PE(ΔIII)/E7 and PE(ΔIII)/E6+PE(ΔIII)/E7 groups. Mice vaccinated with the PE(ΔIII)/E6+PE(ΔIII)/E7 fusion proteins had a smaller subcutaneous tumor size than those vaccinated with PE(ΔIII)/E6 or PE(ΔIII)/E7 fusion proteins alone.

Conclusion

Fusion protein vaccines targeting both E6 and E7 tumor antigens generated more potent immunotherapeutic effects than E6 or E7 tumor antigens alone. This novel strategy of targeting two tumor antigens together can promote the development of cancer vaccines and immunotherapy in HPV-related malignancies.

Connective tissue growth factor in tumor pathogenesis

Key roles for connective tissue growth factor (CTGF/CCN2) are demonstrated in the wound repair process where it promotes myofibroblast differentiation and angiogenesis. Similar mechanisms are active in tumor-reactive stroma where CTGF is expressed. Other potential roles include prevention of hypoxia-induced apoptosis and promoting epithelial-mesenchymal transistion (EMT). CTGF expression in tumors has been associated to both tumor suppression and progression. For example, CTGF expression in acute lymphoblastic leukemia, breast, pancreas and gastric cancer correlates to worse prognosis whereas the opposite is true for colorectal, lung and ovarian cancer. This discrepancy is not yet understood. High expression of CTGF is a hallmark of ileal carcinoids, which are well-differentiated endocrine carcinomas with serotonin production originating from the small intestine and proximal colon. These tumors maintain a high grade of differentiation and low proliferation. Despite this, they are malignant and most patients have metastatic disease at diagnosis. These tumors demonstrate several phenotypes potentially related to CTGF function namely: cell migration, absent tumor cell apoptosis, as well as, reactive and well vascularised myofibroblast rich stroma and fibrosis development locally and in distal organs. The presence of CTGF in other endocrine tumors indicates a role in the progression of well-differentiated tumors.

Cancer microenvironment and cancer vaccine

The cancer microenvironment is constituted of non-transformed host stromal cells such as endothelial cells, fibroblasts, various immune cells, and a complex extra-cellular matrix secreted by both the normal and neoplastic cells embedded in it. The importance of the microenvironment and its potential in cancer therapy is just being established. Among modalities that target the microenvironment, cancer vaccine is a unique strategy which is aimed to elicit specific immunity against components in the microenvironment. Most, if not all, components can be targeted by the vaccines. The most extensively studied are the endothelial cells, fibroblasts and macrophages as well as ECM. Vaccines are in development for each of them. All the vaccines were proved to be effective at providing protective or therapeutic anti-tumor effects in the pre-clinical models. A few of them have been tested in the clinical trials. The mechanisms of the vaccines were mainly related to the cellular immune response such as CD8+ cytotoxic T cells, and in some instances CD4+ Th cells were involved as well. The present review also discussed the hurdles associated with the microenvironment-based vaccines such as the selection of suitable patients with appropriate biomarkers. With the rapid increase of our knowledge in the cancer microenvironment, the proof-of-concept of microenvironment-based cancer vaccines will surely expand our armamentarium against cancer.

Therapeutic HPV DNA vaccines

It is now well established that most cervical cancers are causally associated with HPV infection. This realization has led to efforts to control HPV-associated malignancy through prevention or treatment of HPV infection. Currently, commercially available HPV vaccines are not designed to control established HPV infection and associated premalignant and malignant lesions. To treat and eradicate pre-existing HPV infections and associated lesions which remain prevalent in the U.S. and worldwide, effective therapeutic HPV vaccines are needed. DNA vaccination has emerged as a particularly promising form of therapeutic HPV vaccines due to its safety, stability and ability to induce antigen-specific immunity. This review focuses on improving the potency of therapeutic HPV vaccines through modification of dendritic cells (DCs) by [1] increasing the number of antigen-expressing/antigen-loaded DCs, [2] improving HPV antigen expression, processing and presentation in DCs, and [3] enhancing DC and T cell interaction. Continued improvement in therapeutic HPV DNA vaccines may ultimately lead to an effective DNA vaccine for the treatment of HPV-associated malignancies.

Immunotherapy for cervical cancer: Research status and clinical potential

The high-risk types of human papillomavirus (HPV) have been found to be associated with most cervical cancers and play an essential role in the pathogenesis of the disease. Despite recent advances in preventive HPV vaccine development, such preventive vaccines are unlikely to reduce the prevalence of HPV infections within the next few years, due to their cost and limited availability in developing countries. Furthermore, preventive HPV vaccines may not be capable of treating established HPV infections and HPV-associated lesions, which account for high morbidity and mortality worldwide. Thus, it is important to develop therapeutic HPV vaccines for the control of existing HPV infection and associated malignancies. Therapeutic vaccines are quite different from preventive vaccines in that they require the generation of cell-mediated immunity, particularly T cell-mediated immunity, instead of the generation of neutralizing antibodies. The HPV-encoded early proteins, the E6 and E7 oncoproteins, form ideal targets for therapeutic HPV vaccines, since they are consistently expressed in HPV-associated cervical cancer and its precursor lesions and thus play crucial roles in the generation and maintenance of HPV-associated disease. Our review covers the various therapeutic HPV vaccines for cervical cancer, including live vector-based, peptide or protein-based, nucleic acid-based, and cell-based vaccines targeting the HPV E6 and/or E7 antigens. Furthermore, we review the studies using therapeutic HPV vaccines in combination with other therapeutic modalities and review the latest clinical trials on therapeutic HPV vaccines.

Metronomic chemotherapy enhances antitumor effects of cancer vaccine by depleting regulatory T lymphocytes and inhibiting tumor angiogenesis

Although cancer vaccines are emerging as innovative methods for cancer treatment, these alone have limited potential for treating measurable tumor burden. Thus, the importance of identifying anticancer strategies with greater potency is necessary. The chimeric DNA vaccine CTGF/E7 (connective tissue growth factor linked to the tumor antigen human papillomavirus 16 E7) generates potent E7-specific immunity and antitumor effects. We tested immune-modulating doses of chemotherapy in combination with the CTGF/E7 DNA vaccine to treat existing tumors in mice. Metronomic low doses of paclitaxel, not the maximal tolerable dose, are synergistic with the antigen-specific DNA vaccine. Paclitaxel, given in metronomic sequence with the CTGF/E7 DNA vaccine enhanced the vaccine's potential to delay tumor growth and decreased metastatic tumors in vivo better than the CTGF/E7 DNA vaccine alone. The two possible mechanisms of metronomic paclitaxel chemotherapy are the depletion of regulatory T cells and the inhibition of tumor angiogenesis rather than direct cancer cell cytolytic effects. Results indicate that combination treatment of metronomic chemotherapy and antigen-specific DNA vaccine can induce more potent antigen-specific immune responses and antitumor effects. This provides an immunologic basis for further testing in cancer patients.

Perspectives for preventive and therapeutic HPV vaccines

Human Papillomavirus (HPV) has been associated with several human cancers, including cervical cancer, vulvar cancer, vaginal and anal cancer, and a subset of head and neck cancers. Thus effective vaccination against HPV provides an opportunity to reduce the morbidity and mortality associated with HPV. The Food and Drug Administration of the United States has approved two preventive vaccines to limit the spread of HPV. However, these are unlikely to impact upon HPV prevalence and cervical cancer rates for many years. Furthermore, preventive vaccines do not exert therapeutic effects on pre-existing HPV infections and HPV-associated lesions. In order to further impact upon the burden of HPV infections worldwide, therapeutic vaccines are being developed. These vaccines aim to generate a cell-mediated immune response to infected cells. This review discusses current preventive and therapeutic HPV vaccines and their future directions.

An HDAC inhibitor enhances the antitumor activity of a CMV promoter-driven DNA vaccine

The cytomegalovirus (CMV) promoter is considered to be one of the strongest promoters for driving the in vivo expression of genes encoded by DNA vaccines. However, the efficacy of DNA vaccines has so far been disappointing (particularly in humans), and this might be explained in part by histone deacetylase (HDAC)-mediated chromatin condensation. Hence, we sought to investigate whether increasing the expression of DNA vaccine antigens with the HDAC inhibitor OSU-HDAC42 would enhance the efficacy of DNA vaccines in vivo. A luciferase assay was used to determine the effects of OSU-HDAC42 on CMV promoter-driven DNA plasmids in vitro and in vivo. Three HDAC inhibitors were able to activate expression from the CMV promoter in NIH3T3 cells and MBT-2 bladder cancer cells. The expression of luciferase was significantly enhanced by co-administration of pCMV-luciferase and OSU-HDAC42 in mice. To explore whether OSU-HDAC42 could enhance the specific antitumor activity of a neu DNA vaccine driven by the CMV promoter, we evaluated therapeutic effects and immune responses in a mouse tumor natively overexpressing HER2/neu. Mice receiving OSU-HDAC42 in combination with the CMV-promoter neu DNA vaccine exhibited stronger antitumor effects than mice given the DNA vaccine only. In addition, a correlation between the antitumor effects and the specific cellular immune responses was observed in the mice receiving the DNA vaccine and OSU-HDAC42.

Recombinant and plasma-derived factor VIII products induce distinct splenic cytokine microenvironments in hemophilia A mice

The use of plasma-derived factor VIII (pdFVIII) concentrates in hemophilia A has been reported to result in reduced anti-FVIII antibody formation. In this study, we have investigated whether the cytokine microenvironment induced by pdFVIII has an influence on reducing anti-FVIII antibody titers in hemophilic mice. Microarray and confirmatory quantitative reverse transcription polymerase chain reaction (RT-PCR) experiments show that pdFVIII infusion causes a different transcriptional profile in dendritic cells than recombinant FVIII (rFVIII). Both treatments caused up-regulation of proinflammatory gene expression, but rFVIII and pdFVIII treatments promote expression of genes that induce Th1 and Th2 responses, respectively. Moreover, administration of rFVIII or pdFVIII concentrates resulted in distinct T-cell splenic cytokine microenvironments. rFVIII induced the release of Th1 cytokines and IL-10, whereas pdFVIII induced the release of Th2 cytokines and transforming growth factor-β. We have also observed high titers of anti–human von Willebrand factor (VWF) antibodies in the pdFVIII-treated mice and propose that this results from antigenic competition. We further investigated the role of this phenomenon using infusions of FVIII and increasing concentrations of recombinant human factor IX (FIX). These studies show an inverse relationship between increasing concentrations of FIX and the production of anti-FVIII antibodies. In summary, these studies report new mechanisms that contribute to reduced anti-FVIII antibody development in hemophilia A after pdFVIII infusions.

Noncarrier naked antigen-specific DNA vaccine generates potent antigen-specific immunologic responses and antitumor effects

Genetic immunization strategies have largely focused on the use of plasmid DNA with a gene gun. However, there remains a clear need to further improve the efficiency, safety, and cost of potential DNA vaccines. The gold particle-coated DNA format delivered through a gene gun is expensive, time and process consuming, and raises aseptic safety concerns. This study aims to determine whether a low-pressured gene gun can deliver noncarrier naked DNA vaccine without any particle coating, and generate similarly strong antigen-specific immunologic responses and potent antitumor effects compared with gold particle-coated DNA vaccine. Our results show that mice vaccinated with noncarrier naked chimeric CRT/E7 DNA lead to dramatic increases in the numbers of E7-specific CD8+ T-cell precursors and markedly raised titers of E7-specific antibodies. Furthermore, noncarrier naked CRT/E7 DNA vaccine generated potent antitumor effects against subcutaneous E7-expressing tumors and pre-established E7-expressing metastatic pulmonary tumors. In addition, mice immunized with noncarrier naked CRT/E7 DNA vaccine had significantly less burning effects on the skin compared with those vaccinated with gold particle-coated CRT/E7 DNA vaccine. We conclude that noncarrier naked CRT/E7 DNA vaccine delivered with a low-pressured gene gun can generate similarly potent immunologic responses and effective antitumor effects has fewer side effects, and is more convenient than conventional gold particle-coated DNA vaccine.