Heat shock protein 70 / MAGE-1 tumor vaccine can enhance the potency of MAGE-1-specific cellular immune responses in vivo

Plasmid DNA for Therapeutic Applications in Cancer

Recently, the interest in using nucleic acids for therapeutic applications has been increasing. DNA molecules can be manipulated to express a gene of interest for gene therapy applications or vaccine development. Plasmid DNA can be developed to treat different diseases, such as infections and cancer. In most cancers, the immune system is limited or suppressed, allowing cancer cells to grow. DNA vaccination has demonstrated its capacity to stimulate the immune system to fight against cancer cells. Furthermore, plasmids for cancer gene therapy can direct the expression of proteins with different functions, such as enzymes, toxins, and cytotoxic or proapoptotic proteins, to directly kill cancer cells. The progress and promising results reported in animal models in recent years have led to interesting clinical results. These DNA strategies are expected to be approved for cancer treatment in the near future. This review discusses the main strategies, challenges, and future perspectives of using plasmid DNA for cancer treatment.

Preparation of a new combination nanoemulsion-encapsulated MAGE1-MAGE3-MAGEn/HSP70 vaccine and study of its immunotherapeutic effect

BACKGROUND

MAGE family genes have been studied as targets for tumor immunotherapy for a long time. Here, we combined MAGE1-, MAGE3- and MAGEn-derived peptides as a cancer vaccine and tested whether a new combination nanoemulsion-encapsulated vaccine could be used to inhibit the growth of tumor cells in humanized SCID mice.

METHODS

The nanoemulsion-encapsulated complex protein vaccine (MAGE1, MAGE3, and MAGEn/HSP70 fusion protein; M1M3MnH) was prepared using a magnetic ultrasonic technique. After screening, human PBMCs were injected into SCID mice to mimic the human immune system. Then, the humanized SCID mice were challenged with M3-HHCC cells and immunized with nanoemulsion-encapsulated MAGE1-MAGE3-MAGEn/HSP70 [NE(M1M3MnH)] or M1M3MnH. The cellular immune responses were detected by IFN-γ ELISPOT and cytotoxicity assays. Therapeutic and tumor challenge experiments were also performed.

RESULTS

The results showed that the immune responses elicited by NE(M1M3MnH) were apparently stronger than those elicited by M1M3MnH, NE(-) or PBS, suggesting that this novel nanoemulsion carrier induces potent antitumor immunity against the encapsulated antigens. The results of the therapeutic and tumor challenge experiments also indicated that the new vaccine had a definite effect on SCID mice bearing human hepatic cancer.

CONCLUSION

Our study indicated that the combination of several tumor antigen-derived peptides may be a relatively good strategy for peptide-based cancer immunotherapy. These results suggest that the complex nanoemulsion vaccine could have broader applications for both therapy and prevention mediated by antitumor effects in the future.

Gas‑filled ultrasound microbubbles enhance the immunoactivity of the HSP70‑MAGEA1 fusion protein against MAGEA1‑expressing tumours

Advanced malignant melanoma is characterized by rapid development, poor prognosis and insensitivity to chemoradiotherapy. Immunotherapy has become one of the primary clinical treatments for malignant melanomas. In recent decades, identifying specific tumour antigens and the enhanced immunoactivity of tumour vaccines has become critical for engineering successful tumour vaccines. As a widely used vaccine carrier, heat shock protein 70 (HSP70) clearly increases the immunogenicity of tumour antigens, such as melanoma-associated antigen A1 (MAGEA1). Based on previous studies, gas-filled ultrasound microbubbles (MBs) were engineered to carry an HSP70-MAGEA1 fusion protein (FP). Following subcutaneous injection around the lymphatic nodes the FP was directly released into the lymph nodes under ultrasonic imaging. The results indicated that the microbubbles enhanced the immunoactivity of FPs more effectively than HSP70-MAGEA1 fusion alone. Additionally, HSP70-MAGEA1 delivered via microbubbles clearly inhibited and delayed the growth of MAGEA1-expressing B16 melanomas in mice and improved the survival times of these animals compared with the fusion protein alone. The results of the present study demonstrated that controlled MBs enhance the immunoactivity of FPs and also highlights novel, potential vaccine carriers and a new strategy for engineering controllable tumour vaccine designs.

In vivo enhancement of the MAGE-specific cellular immune response by a recombinant MAGE1-MAGE3-TBHSP70 tumor vaccine

Background

Since cytotoxic T cell (CTL) response is the major cellular type in attacking tumor cells, most immunotherapy targets to manipulate the CTL response. Immunotherapies targeting melanoma-specific antigens (MAGEs), a group of tumor-specific shared antigen, have shown to be promising. Our previous study has shown that MAGE1/TBHSP70 and MAGE3/TBHSP70 could induce a robust immune response against B-16 melanoma cells in C57BL/6 mice. In this study, we used an animal model to further demonstrate MAGEs as a potential immunotherapy target for tumorigenesis in vivo.

Methods

In the current study, we developed a MAGE1/MAGE3/TBHSP70 recombinant protein vaccine and evaluated its protective efficacy against tumor development by challenge vaccine-immunized mice with MAGE-expressing human tumor cell lines in a Hu-PBL-SCID mouse model. The cellular immune reactions were monitored by ELISPOT and cytotoxicity assays.

Results

Splenocytes isolated from vaccine-immunized mice presented potent cytokine secretion capacity and CTL-specific cytotoxic. Vaccine-immunized mice had a significant tumor regression and prolonged survival compared with controls (both p < 0.05). In vitro, rMAGE1-MAGE3-TBHSP70 showed a potent tumor-antigen-specific immune response in both hepatocellular carcinoma and pulmonary carcinoma cell lines.

Conclusion

This newly-developed recombinant protein vaccine may serve as a new immunotherapy for cancer.

Fusion of Hsp70 to Mage-a1 enhances the potency of vaccine-specific immune responses

Background

Heat shock proteins (HSPs) are capable of promoting antigen presentation of chaperoned peptides through interactions with receptors on antigen presenting cells. This property of HSPs suggests a potential function as an adjuvant-free carrier to stimulate immune responses against a covalently linked fusion partner. MAGE-A1 is a likely candidate for tumor immunotherapy due to its abundant immunogenic epitopes and strict tumor specificity. To analyze the influence of HSP70 conjugation to MAGE-A1, towards developing a novel effective vaccine against MAGE-expressing tumors, we cloned the murine counterpart of the human HSP70 and MAGE-A1 genes.

Methods

Recombinant proteins expressing Mage-a1 (aa 118–219), Hsp70, and Mage-a1-Hsp70 fusion were purified and used to immunize C57BL/6 mice. The humoral and cellular responses elicited against Mage-a1 were measured by ELISA, IFN-γ ELISPOT assay, and cytotoxicity assay.

Results

Immunization of mice with Mage-a1-Hsp70 fusion protein elicited significantly higher Mage-a1-specific antibody titers than immunization with either Mage-a1 alone or a combination of Mage-a1 + Hsp70. The frequency of IFN-γ-producing cells and the cytotoxic T lymphocyte (CTL) activity was also elevated. Consistent with the elevated immune response, immunization with fusion protein induced potent in vivo antitumor immunity against MAGE-a1-expressing tumors.

Conclusions

These results indicate that the fusion of Hsp70 to Mage-a1 can enhance immune responses and anti-tumor effects against Mage-a1-expressing tumors. Fusion of HSP70 to a tumor antigen may greatly enhance the potency of protein vaccines and can potentially be applied to other cancer systems with known tumor-specific antigens. These findings provide a scientific basis for the development of a novel HSP70 and MAGE fusion protein vaccine against MAGE-expressing tumors.

Nanomaterials in the application of tumor vaccines: advantages and disadvantages

Tumor vaccines are a novel approach to the treatment of malignancy, and are attracting the attention of the medical profession. Nanomaterials have significant advantages in the preparation of a tumor vaccine, including their ability to penetrate and target cancer tissue and their antigenic properties. In this review, we focus on several nanomaterials, ie, carbon nanotubes, nanoemulsions, nanosized aluminum, and nanochitosan. Applications for these nanomaterials in nanovaccines and their biological characteristics, as well as their potential toxicity, are discussed.

Enhancement of immunogenicity of murine lymphocytic leukemia cells by transfection with BCG heat shock protein 70 gene

The effects of BCG heat shock protein 70 (BCG HSP70) gene transfection on tumorigenicity and immunogenicity of murine lymphocytic leukemia cell line (L1210) were studied. After HSP70 gene transfection, the tumor cells became strongly immunogenic and lost their tumorigenicity in syngeneic mice. It mainly exhibited that tumor growth was slow or without the formation of tumor, mean survival time of mice was significantly prolonged and a marked stimulating effect on L1210 specific Th1 cells detected by IFN-γ ELISPOT assay. Tumor-bearing mice treated with the L1210-HSP70 cells showed thorough coagulation necrosis and abundant CD8+ T lymphocyte infiltration. Meanwhile, as the tumor vaccine, the HSP70-transfected tumor cells could induce a protective immune response in vivo. It showed that the tumor growth was significantly inhibited, tumor diameter was markedly reduced and the survival time of tumor-bearing mice was further prolonged. Immunization with it also resulted in regression of the established L1210 tumor and prolonged survival time of mice. These results suggest that gene transfection of BCG HSP70 could effectively improve the immunogenicity of tumor cells and it may be used as a suitable candidate gene-modified cell vaccine for cancer immunotherapy.

The preparation of HL-60 cells vaccine expressing BCG heat shock protein 70 and detection of its immunogenicity in vitro

Gene-modified cell vaccines are the best way to achieve the immunotherapy for all types of acute leukemia. In this study, the recombinant eukaryotic expression vector (pDisplay-HSP70) of heat shock protein 70 (HSP70) of Bacille Calmette-Guérin (BCG) was constructed by amplifying the whole BCG HSP70 gene using polymerase chain reaction (PCR) and sub-cloning into the polyclone endonuclease sites in pDisplay. Then the HL-60 cell vaccine expressing the protein onto the cell surface was prepared by lipofectamine transfection and its anti-tumor effect and mechanism were further studied. Results showed that the fragment of BCG HSP70 was consistent with Mycobacterium tuberculosis HSP70 gene published in GeneBank. DNA sequencing showed that the recombinant vector was correctly constructed and named pDisplay-HSP70. After BCG HSP70 gene transfection, the yellow-green fluorescence on the HL-60 cells surface was observed under a fluorescence microscope. The immunogenicity of HSP70-transfected HL-60 cells exhibited upregulated proliferation of lymphocytes, increased cytokine secretion (IFN-γ) and enhanced killing activity. These results suggested that gene transfection of BCG HSP70 could significantly enhance the immunogenicity of HL-60 cells. It may be used as a suitable candidate gene-modified cell vaccine for cancer immunotherapy.

The preparation of leukemia cell vaccine expressing BCG heat shock protein 70 and anti-leukemia effect in vitro

Gene-modified cell vaccines are the best way to achieve the immunotherapy for all types of acute leukemia. In this study, heat shock protein 70 (HSP70) gene of BCG was transfected into the acute leukemia cells and its anti-leukemia effect was further studied. Results showed that short-term culture of the leukemia cells exhibited increased number and no change in antigen expression. After HSP70 gene transfection, the yellow-green fluorescence on the leukemia cell surface was observed under a fluorescence microscope. The immunogenicity of HSP70-transfected cells exhibited that autologous lymphocytes proliferated significantly and secreted higher amount of IFN-γ, and cytotoxic T lymphocytes induced more beneficial anti-leukemia effects. These results suggested that gene transfection of BCG HSP70 could significantly enhance the immunogenicity of leukemia cells. It may be used as a suitable candidate gene-modified cell vaccine for cancer immunotherapy.

Cancer-germline antigen vaccines and epigenetic enhancers: future strategies for cancer treatment

IMPORTANCE OF THE FIELD

Immunotherapy holds great potential for disseminated cancer, and cancer-germline (CG) antigens are among the most promising tumor targets. They are widely expressed in different cancer types and are essentially tumor-specific, since their expression in normal tissues is largely restricted to immune-privileged sites. Although the therapeutic potential of these antigens may be compromised by their highly heterogeneous expression in many tumors and low frequency in some cancers, recent developments suggest that tumor-cell-selective enhancement of CG antigen gene expression can be achieved using epigenetic modifiers.

AREAS COVERED IN THIS REVIEW

We provide an overview of the potential of CG antigens as targets for cancer immunotherapy, including advantages and disadvantages. We also discuss the current state of development of CG antigen vaccines, and the potential synergistic effect of combining CG antigen immunotherapeutic strategies with epigenetic modifiers.

WHAT THE READER WILL GAIN

The reader will gain an overview of the past, present and future role of CG antigens in cancer immunotherapy.

TAKE HOME MESSAGE

Chemoimmunotherapy using epigenetic drugs and CG antigen vaccines may be a useful approach for treating cancer.

N-terminally fusion of Her2/neu to HSP70 decreases efficiency of Her2/neu DNA vaccine

DNA vaccines consisted of tumor-associated antigen (TAA) are well suited for immunotherapy against tumor. The construct can contain TAA fused to an appropriate molecule (biologic adjuvant) to improve the efficacy of anti-tumor immune response. Heat shock protein 70 (HSP70) has been shown to be an excellent candidate, capable of cross-priming TAA by antigen presenting cells leading to a robust T-cell response. However, the relationship between strong T-cell responses and tumor rejection is not always mutually exclusive, for which TAA loss or activation of suppressive mechanisms may occur. HSP70 fused to downstream of Her2/neu as DNA vaccine has been shown to be efficient against Her2-expressing tumors. In this study, we examined if N-terminally fusion of Her2/neu to HSP70 could also improve efficiency of Her2/neu DNA vaccine. Therefore, mice with an established Her2/neu expressing tumor were immunized with DNA vaccine consisting of extracellular and trans-membrane domain (EC+TM) of rat Her2/neu alone or N-terminally fused to HSP70 and immune response was evaluated. Administration of rat Her2/neu led to partial control of tumor progression. Surprisingly, fusion of HSP70 to N-terminal of rat Her2/neu led to tumor progression. Our result proposes that fusion direction of biologic adjuvant is an important consideration when Her2/neu is used.

The antitumor immune responses induced by nanoemulsion-encapsulated MAGE1-HSP70/SEA complex protein vaccine following peroral administration route

Previous studies have shown that there are profuse lymphatic tissues under the intestinal mucous membrane. Moreover, vaccine administered orally can elicit both mucous membrane and system immune response simultaneously, accordingly induce tumor-specific cytotoxic T lymphocyte. As a result, the oral route is constituted the preferred immune route for vaccine delivery theoretically. However, numerous vaccines especially protein/peptide vaccines remain poorly available when administered by this route. Nanoemulsion has been shown as a useful vehicle can be developed to enhance the antitumor immune response against antigens encapsulated in it and it is good for the different administration routes. Of particular interest is whether the protein vaccine following peroral route using nanoemulsion as delivery carrier can induce the same, so much as stronger antitumor immune response to following conventional ways such as subcutaneous (sc.) or not. Hence, in the present study, we encapsulated the MAGE1-HSP70 and SEA complex protein in nanoemulsion as nanovaccine NE (MHS) using magnetic ultrasound method. We then immuned C57BL/6 mice with NE (MHS), MHS alone or NE (-) via po. or sc. route and detected the cellular immunocompetence by using ELISpot assay and LDH release assay. The therapeutic and tumor challenge assay were examined then. The results showed that compared with vaccination with MHS or NE (-), the cellular immune responses against MAGE-1 could be elicited fiercely by vaccination with NE (MHS) nanoemulsion. Furthermore, encapsulating MHS in nanoemulsion could delay tumor growth and defer tumor occurrence of mice challenged with B16-MAGE-1 tumor cells. Especially, the peroral administration of NE (MHS) could induce approximately similar antitumor immune responses to the sc. administration, but the MHS unencapsulated with nanoemulsion via po. could induce significantly weaker antitumor immune responses than that via sc., suggesting nanoemulsion as a promising carrier can exert potent antitumor immunity against antigen encapsulated in it and make the tumor protein vaccine immunizing via po. route feasible and effective. It may have a broad application in tumor protein vaccine.

Fusion protein of ATPase domain of Hsc70 with TRP2 acting as a tumor vaccine against B16 melanoma

HSP70s are a family of ATP-dependent chaperones of relative molecular masses around 70kDa. Immunization of mice with HSP70 isolated from tumor tissues has been proved to elicit specific protective immunity against the original tumor. Recent researches have demonstrated that the ATPase domain of HSP70 and the tumor antigenic peptide that binds to Hsp70 were the crucial parts eliciting tumor-specific immunity. These findings suggested that a recombinant protein expressed in Escherichia coli, comprising a covalently fused fragment of tumor rejection antigen to ATPase domain of HSP70, could be used as a tumor vaccine. However, high-level expressions of heterologous recombinant proteins in E. coli often lead to the formation of inclusion bodies, resulting in defects in solubility and bioactivity. In the present work, we found an approach to resolve these problems, focusing on a refolding procedure via gel-filtration chromatography for denatured inclusion body proteins. Here, we expressed, purified and refolded a fusion protein comprising murine heat shock cognate protein 70 (Hsc70) N-terminal ATPase domain (Hsc70NTD) and a portion of TRP2 (aa153-417) as a model protein. The refolding effectivities were assessed according to their ATPase activities, the vaccine function was assessed according to immunization effect in inducing antigen-specific CTLs and to in vivo tumor protection. The results showed that the fusion protein refolded via gel-filtration chromatography exhibited ATPase activity, succeeded in eliciting antigen-specific CTL in vivo and delayed tumor growth on tumor-bearing mice.

Generation of anti-tumor immunity using mammalian heat shock protein 70 DNA vaccines for cancer immunotherapy

In this study, we explored the protective anti-tumor potency of mouse (self) Hsp70 or Hsp110-based DNA vaccination approach targeting a tumor-associated antigen, human papilloma virus (HPV) type 16 E7 protein. Linkage of E7 to the N-terminus of the mouse Hsp70 not only elicits an E7-specific cytotoxic T cell (CTL) response, but also protects mice against challenge with E7 expressing tumors. CD8+ T-cells are crucial in both priming and effector phases for the induction of tumor immunity, whereas CD4+ T-cells and NK cells do not appear to play a major role. Furthermore, the ATP-binding domain deletion mutant Hsp70(382-641), when fused to E7, was immunologically effective, suggesting that the peptide-binding region, not the ATPase domain of Hsp70, is required for the vaccine activity of the E7-Hsp70 DNA. This study demonstrates that autologous Hsp70 is highly potent in enhancing antigen-specific immune responses. Functional domain mapping and orientation of the E7 and Hsp70 in the fusion gene may have clinical implications for the design and optimization of Hsp70-based DNA vaccines.

Molecular chaperones and cancer immunotherapy

As one of the most abundant and evolutionally conserved intracellular proteins, heat shock proteins, also known as stress proteins or molecular chaperones, perform critical functions in maintaining cell homeostasis under physiological as well as stress conditions. Certain chaperones in extracellular milieu are also capable of modulating innate and adaptive immunity due to their ability to chaperone polypeptides and to interact with the host's immune system, particularly professional antigen-presenting cells. The immunomodulating properties of chaperones have been exploited for cancer immunotherapy. Clinical trials using chaperone-based vaccines to treat various malignancies are ongoing.

Cancer immunotherapy based on intracellular hyperthermia using magnetite nanoparticles: a novel concept of "heat-controlled necrosis" with heat shock protein expression

Heat shock proteins (HSPs) are highly conserved proteins whose syntheses are induced by a variety of stresses, including heat stress. Since the expression of HSPs, including HSP70, protects cells from heat-induced apoptosis, HSP expression has been considered to be a complicating factor in hyperthermia. On the other hand, recent reports have shown the importance of HSPs, such as HSP70, HSP90 and glucose-regulated protein 96 (gp96), in immune reactions. If HSP expression induced by hyperthermia is involved in tumor immunity, novel cancer immunotherapy based on this novel concept can be developed. In such a strategy, a tumor-specific hyperthermia system, which can heat the local tumor region to the intended temperature without damaging normal tissue, would be highly advantageous. To achieve tumor-specific hyperthermia, we have developed an intracellular hyperthermia system using magnetite nanoparticles. This novel hyperthermia system can induce necrotic cell death via HSP expression, which induces antitumor immunity. In the present article, cancer immunology and immunotherapy based on hyperthermia, and HSP expression are reviewed and discussed.

Heat shock protein 70/MAGE-3 fusion protein vaccine can enhance cellular and humoral immune responses to MAGE-3 in vivo

MAGE-3, a member of melanoma antigen (MAGE) gene family, is recognized as an ideal candidate for tumor vaccine because it is expressed in a significant proportion of tumors of various histological types and can induce antigen-specific immune response in vivo. There is now substantial evidence that heat shock proteins HSPs isolated from cancer cells and virus-infected cells can be used as vaccines to produce cancer-specific or virus-specific immunity. In this research, we investigated whether M. tuberculosis HSP70 can be used as vehicle to elicit immune response to its accompanying MAGE-3 protein. A recombinant protein expression vector was constructed that permitted the production of fusion protein linking amino acids 195-314 of MAGE-3 to the C terminus of HSP70. We found that HSP70-MAGE-3 fusion protein can elicit stronger cellular and humoral immune responses against MAGE-3 expressing murine tumor than those elicited by MAGE-3 protein in vivo, which resulted in potent antitumor immunity against MAGE-3-expressing tumors. Covalent linkage of HSP70 to MAGE-3 was necessary to elicit immune response to MAGE-3. These results indicate that linkage of HSP70 to MAGE-3 enhanced immune responses to MAGE-3 in vivo and HSP70 can be exploited to enhance the cellular and humoral immune responses against any attached tumor-specific antigens.

Screening of cytokines to enhance vaccine effects of heat shock protein 70-rich tumor cell lysate

Heat shock proteins (HSPs) have been recognized as significant participants in immune reactions. We have previously reported that heat-treated cells expressing HSP70 can mediate potent antitumor immune responses. As successful immunotherapy is dependent on the host immune system, the present study evaluated whether systemic administration of immunocyte stimulatory and growth promoting cytokines could enhance heat-treated cell lysate vaccine (HCLV) immunization to further promote the antitumor immunity. After heating mouse melanoma B16 cells (43 degrees C, 30 min) to elicit increased HSP70 expression, cells were lysed by freeze thawing to prepare HCLV. In approaches using a poorly immunogenic melanoma B16, the effects of various cytokines (IL-1beta, -2, -4, -6 and -12, IFN-beta and -gamma, GM-CSF and TNF-alpha) were assessed in combination with HCLV. Syngenic C57BL/6 mice were immunized subcutaneously with HCLV twice, on days -14 and -7, while cytokines were injected intraperitoneally on day -7. Subcutaneous B16 cell challenge was performed on day 0. IL-12 significantly enhanced the efficacy of HCLV, compared to non-heated cell lysate vaccine (CLV) and non-vaccination. Systemic administration of recombinant IL-12 augmented the efficacy of HCLV, inducing protective immunity against tumor challenge and enhancing cytotoxicity assessed in primed splenocytes against B16 cells in treated mice. These results suggest that IL-12 represents an important modulator of antitumor immune responses induced by HCLV, and may facilitate further efforts to develop novel cancer immunotherapies based on HSP70-mediated vaccination.