CpG DNA and cancer immunotherapy: orchestrating the antitumor immune response

CpG DNA-triggered upregulation of TLR9 expression affects apoptosis and immune responses in human plasmacytoid dendritic cells isolated from chronic hepatitis B patients

Plasmacytoid dendritic cells (pDCs) were treated with cytosine-phosphate-guanine (CpG) DNA, and cell apoptosis, signals and immune responses were measured to investigate the effects and mechanism of CpG DNA in pDCs from chronic hepatitis B patients. CpG DNA-stimulated pDCs secreted more IFN-α than the control pDCs. CpG DNA activated Toll-like receptor 9 (TLR9), thereby resulting in the upregulated expression of myeloid differentiation primary response gene 88 (MyD88), interferon regulatory factor 7 (IRF7) and nuclear factor kappa B (NF-κB). Furthermore, CpG DNA down-regulated apoptosis and promoted the expression of IFN-α, interleukin-12 (IL-12), IL-21, IL-26 and tumour necrosis factor-α (TNF-α) in pDCs. Following treatment with NF-κB inhibitor, pyrollidine dithiocarbamate (PDTC), the influence of CpG DNA on pDCs was inhibited. Our results suggest that CpG DNA may directly interfere with the function of pDCs through TLR9-mediated upregulation of MyD88, IRF7 and NF-κB expression, which can partially explain the activation of pDCs in chronic hepatitis B patients.

Intratumoural administration and tumour tissue targeting of cancer immunotherapies

Immune-checkpoint inhibitors and chimeric antigen receptor (CAR) T cells are revolutionizing oncology and haematology practice. With these and other immunotherapies, however, systemic biodistribution raises safety issues, potentially requiring the use of suboptimal doses or even precluding their clinical development. Delivering or attracting immune cells or immunomodulatory factors directly to the tumour and/or draining lymph nodes might overcome these problems. Hence, intratumoural delivery and tumour tissue-targeted compounds are attractive options to increase the in situ bioavailability and, thus, the efficacy of immunotherapies. In mouse models, intratumoural administration of immunostimulatory monoclonal antibodies, pattern recognition receptor agonists, genetically engineered viruses, bacteria, cytokines or immune cells can exert powerful effects not only against the injected tumours but also often against uninjected lesions (abscopal or anenestic effects). Alternatively, or additionally, biotechnology strategies are being used to achieve higher functional concentrations of immune mediators in tumour tissues, either by targeting locally overexpressed moieties or engineering 'unmaskable' agents to be activated by elements enriched within tumour tissues. Clinical trials evaluating these strategies are ongoing, but their development faces issues relating to the administration methodology, pharmacokinetic parameters, pharmacodynamic end points, and immunobiological and clinical response assessments. Herein, we discuss these approaches in the context of their historical development and describe the current landscape of intratumoural or tumour tissue-targeted immunotherapies.

CpG-Based Nanovaccines for Cancer Immunotherapy

Cancer has been a serious health hazard to the people all over the world with its high incidence and horrible mortality. In recent years, tumor vaccines in immunotherapy have become a hotspot in cancer therapy due to their many practical advantages and good therapeutic potentials. Among the various vaccines, nanovaccine utilized nanoparticles (NPs) as the carrier and/or adjuvant has presented significant therapeutic effect in cancer treatment. For tumor nanovaccines, unmethylated cytosine-phosphate-guanine oligodeoxynucleotide (CpG ODN) is a commonly used adjuvant. It has been reported that CpG ODN was the most effective immune stimulant among the currently known adjuvants. It could be recognized by toll-like receptor 9 (TLR9) to activate humoral and cellular immunity for preventing or treating cancer. In this review, the topic of CpG-based nanovaccines for cancer immunotherapy will be focused. The types and properties of different CpG will be introduced in detail first, and then some representative tumor nanovaccines will be reviewed according to the diverse loading modes of CpG, such as electrostatic adsorption, covalent bonding, hydrophilic and hydrophobic interaction, and DNA self-assembly, for summarizing the current progress of CpG-based tumor nanovaccines. Finally, the challenges and future perspectives will be discussed. It is hoped that this review will provide valuable references for the development of nanovaccines in cancer immunotherapy.

In vivo cancer vaccination: Which dendritic cells to target and how?

The field of cancer immunotherapy has been revolutionized with the use of immune checkpoint blockade antibodies such as anti-programmed cell death 1 protein (PD-1) and chimeric antigen receptor T cells. Significant clinical benefits are observed in different cancer types with these treatments. While considerable efforts are made in augmenting tumor-specific T cell responses with these therapies, other immunotherapies that actively stimulate endogenous anti-tumor T cells and generating long-term memory have received less attention. Given the high cost of cancer immunotherapies especially with chimeric antigen receptor T cells, not many patients will have access to such treatments. The next-generation of cancer immunotherapy could entail in vivo cancer vaccination to activate both the innate and adaptive anti-tumor responses. This could potentially be achieved via in vivo targeting of dendritic cells which are an indispensable link between the innate and adaptive immunities. Dendritic cells highly expressed toll-like receptors for recognizing and eliminating pathogens. Synthetic toll-like receptors agonists could be synthesized at a low cost and have shown promise in preclinical and clinical trials. As different subsets of human dendritic cells exist in the immune system, activation with different toll-like receptor agonists could exert profound effects on the quality and magnitude of anti-tumor T cell responses. Here, we reviewed the different subsets of human dendritic cells. Using published preclinical and clinical cancers studies available on PubMed, we discussed the use of clinically approved and emerging toll-like receptor agonists to activate dendritic cells in vivo for cancer immunotherapy. Finally, we searched www.clinicaltrials.gov and summarized the active cancer trials evaluating toll-like receptor agonists as an adjuvant.

DNA-Based Bulk Hydrogel Materials and Biomedical Application

Being a natural polymer, DNA attracts extensive attention and possesses great potential to open a new way for researches of biomedical or material science. In the past few decades, approaches have been developed to bring DNA into the realm of bulk materials. In this review, we discussed the progresses achieved for fabrication of novel materials with a large physical dimension from the DNA polymer.

Functional nucleic acid-based hydrogels for bioanalytical and biomedical applications

Hydrogels are crosslinked hydrophilic polymers that can absorb a large amount of water. By their hydrophilic, biocompatible and highly tunable nature, hydrogels can be tailored for applications in bioanalysis and biomedicine. Of particular interest are DNA-based hydrogels owing to the unique features of nucleic acids. Since the discovery of the DNA double helical structure, interest in DNA has expanded beyond its genetic role to applications in nanotechnology and materials science. In particular, DNA-based hydrogels present such remarkable features as stability, flexibility, precise programmability, stimuli-responsive DNA conformations, facile synthesis and modification. Moreover, functional nucleic acids (FNAs) have allowed the construction of hydrogels based on aptamers, DNAzymes, i-motif nanostructures, siRNAs and CpG oligodeoxynucleotides to provide additional molecular recognition, catalytic activities and therapeutic potential, making them key players in biological analysis and biomedical applications. To date, a variety of applications have been demonstrated with FNA-based hydrogels, including biosensing, environmental analysis, controlled drug release, cell adhesion and targeted cancer therapy. In this review, we focus on advances in the development of FNA-based hydrogels, which have fully incorporated both the unique features of FNAs and DNA-based hydrogels. We first introduce different strategies for constructing DNA-based hydrogels. Subsequently, various types of FNAs and the most recent developments of FNA-based hydrogels for bioanalytical and biomedical applications are described with some selected examples. Finally, the review provides an insight into the remaining challenges and future perspectives of FNA-based hydrogels.

In Vivo Silencing of A20 via TLR9-Mediated Targeted SiRNA Delivery Potentiates Antitumor Immune Response

A20 is an ubiquitin-editing enzyme that ensures the transient nature of inflammatory signaling pathways induced by cytokines like TNF-α and IL-1 or pathogens via Toll-like receptor (TLR) pathways. It has been identified as a negative regulator of dendritic cell (DC) maturation and attenuator of their immunostimulatory properties. Ex vivo A20-depleted dendritic cells showed enhanced expression of pro-inflammatory cytokines and costimulatory molecules, which resulted in hyperactivation of tumor-infiltrating T lymphocytes and inhibition of regulatory T cells. In the present study, we demonstrate that a synthetic molecule consisting of a CpG oligonucleotide TLR9 agonist linked to A20-specific siRNAs silences its expression in TLR9⁺ mouse dendritic cells in vitro and in vivo. In the B16 mouse melanoma tumor model, silencing of A20 enhances the CpG-triggered induction of NFκB activity followed by elevated expression of IL-6, TNF-α and IL-12. This leads to potentiated antitumor immune responses manifested by increased numbers of tumor-specific cytotoxic T cells, high levels of tumor cell apoptosis and delayed tumor growth. Our findings confirm the central role of A20 in controlling the immunostimulatory potency of DCs and provide a strategy for simultaneous A20 silencing and TLR activation in vivo.

Immunotherapeutic potential of CpG oligodeoxynucleotides in veterinary species

Innate immunity plays a critical role in host defense against infectious diseases by discriminating between self and infectious non-self. The recognition of infectious non-self involves germ-line encoded pattern recognition receptors (PRRs) that recognize pathogen-associated molecular patterns (PAMPs). The PAMPs are the components of pathogenic microbes which include not only the cell wall constituents but also the unmethylated 2'-deoxy-ribo-cytosine-phosphate-guanosine (CpG) motifs. These CpG motifs present within bacterial and viral DNA are recognized by toll-like receptor 9 (TLR9), and signaling by this receptor triggers a proinflammatory cytokine response which, in turn, influences both innate and adaptive immune responses. The activation of TLR9 with synthetic CpG oligodeoxynucleotides (ODNs) induces powerful Th1-like immune responses. It has been shown to provide protection against infectious diseases, allergy and cancer in laboratory animal models and some domestic animal species. With better understanding of the basic biology and immune mechanisms, it would be possible to exploit the potential of CpG motifs for animal welfare. The research developments in the area of CpG and TLR9 and the potential applications in animal health have been reviewed in this article.

CpG oligodeoxynucleotide induces apoptosis and cell cycle arrest in A20 lymphoma cells via TLR9-mediated pathways

Recent studies have suggested that the anti-cancer activity of CpG-oligodeoxynucleotides (CpG-ODNs) is owing to their immunomodulatory effects in tumor-bearing host. The purpose of this study is to investigate the directly cytotoxic activity of KSK-CpG, a novel CpG-ODN with an alternative CpG motif, against A20 and EL4 lymphoma cells in comparison with previously used murine CpG motif (1826-CpG). To evaluate the potential cytotoxic effects of KSK-CpG on lymphoma cells, cell viability assay, confocal microscopy, flow cytometry, DNA fragmentation, Western blotting, and reverse transcription-polymerase chain reaction (RT-PCR) analysis were used. We found that KSK-CpG induced direct cytotoxicity in A20 lymphoma cells, but not in EL4 lymphoma cells, at least in part via TLR9-mediated pathways. Apoptotic cell death was demonstrated to play an important role in CpG-ODNs-induced cytotoxicity. In addition, both mitochondrial membrane potential decrease and G1-phase arrest were involved in KSK-CpG-induced apoptosis in A20 cells. The activities of apoptotic molecules such as caspase-3, PARP, and Bax were increased, but the activation of p27 Kip1 and ERK were decreased in KSK-CpG-treated A20 cells. Furthermore, autocrine IFN-γ partially contributed to apoptotic cell death in KSK-CpG-treated A20 cells. Collectively, our findings suggest that KSK-CpG induces apoptotic cell death in A20 lymphoma cells at least in part by inducing G1-phase arrest and autocrine IFN-γ via increasing TLR9 expression, without the need for immune system of tumor-bearing host. This new understanding supports the development of TLR9-targeted therapy with CpG-ODN as a direct therapeutic agent for treating B lymphoma.

CpG oligonucleotides suppress HepG2 cells-induced Jurkat cell apoptosis via the Fas-FasL-mediated pathway

Objective

To explore the potential role of CpG motif-containing oligonucleotides (CpG-ODN) in modulating the expression of FasL in HepG2 and Fas in Jurkat cells in vitro, and to examine the effect of CpG-ODN treatment on the HepG2 cells-mediated Jurkat cell apoptosis in vitro.

Methods

The expressions of FasL in HepG2 and Fas in Jurkat cells were examined by real time PCR and flow cytometry (FCM). HepG2 and Jurkat cells were co-cultured, and the frequency of apoptotic Jurkat cells and levels of activated caspase-3 were determined by FCM.

Results

Treatment with CpG-ODN down-regulated the expression of FasL in HepG2 cells in a dose- and time-dependent manner. In addition, treatment with CpG-ODN down-regulated the Fas mRNA transcription and protein expression in Jurkat cells. Treatment of HepG2 cells or Jurkat cells with FasL-neutralizing antibody NOK-2 remarkably inhibited the HepG2-medaited Jurkat cell apoptosis. Pre-treatment of HepG2 or Jurkat cells with CpG-ODN significantly reduced the frequency of HepG2-mediated apoptotic Jurkat cells and inhibited the activation of caspase-3 in Jurkat cells in vitro.

Conclusions

Our data indicated that treatment with CpG-ODN inhibited the HepG2 cells-mediated Jurkat cell apoptosis by modulating the Fas/FasL pathway. Apparently, CpG-ODN treatment may be a potential therapeutic reagent for HCC.

Toll-like receptor agonists in cancer therapy

Toll-like receptors (TLRs) are pattern-recognition receptors related to the Drosophila Toll protein. TLR activation alerts the immune system to microbial products and initiates innate and adaptive immune responses. The naturally powerful immunostimulatory property of TLR agonists can be exploited for active immunotherapy against cancer. Antitumor activity has been demonstrated in several cancers, and TLR agonists are now undergoing extensive clinical investigation. This review discusses recent advances in the field and highlights potential opportunities for the clinical development of TLR agonists as single agent immunomodulators, vaccine adjuvants and in combination with conventional cancer therapies.

Current perspectives in prostate cancer vaccines

The use of vaccines as a potential therapeutic modality for the treatment of cancer has been extensively studied. Recent advances include identification and characterization of tumor-associated antigens, novel vaccine delivery systems, and the combination of vaccines with immune stimulants and other therapeutic modalities. Immunotherapy as a modality for treatment of prostate cancer has received significant attention. There are several characteristics of prostate cancer that make it an ideal target for immunotherapy. Prostate cancer's relative indolence allows sufficient time to generate immune responses, which may take weeks or months to mount. In addition, prostate cancer-associated antigens direct the immune response to prostate cancer cells, thus sparing normal vital tissue. This review focuses on promising new vaccines and novel perspectives in the treatment of prostate cancer.

TLR9 signaling promotes tumor progression of human lung cancer cell in vivo

Toll like receptor 9 (TLR9) was identified mainly in cells of the immune system, and CpG oligonucleotides (CpG ODN), which induces signaling through TLR9, are currently under investigation as adjuvants in clinical therapies against cancer. However, accumulating data suggested that functional TLR9 was also expressed in tumor cells and the effects of TLR9 signaling on the progression of tumor cells remain undefined. Our previous study demonstrated that the TLR9 signaling could significantly enhance the metastatic potential of human lung cancer cells in vitro. Here we carefully evaluated the direct effect of TLR9 signaling on tumor progression of human lung cancer cells in vitro and in vivo. We observed that TLR9 agonist CpG ODN could robustly enhance the tumor progression of 95D cells which expressed high level of TLR9 in nude mice. Furthermore, the CpG ODN could effectively induce the proliferation and IL-10 secretion of 95D cells in vitro. Finally, we demonstrated that CpG ODN could significantly elevate the tumor progression of TLR9 modifying 95C cells in vitro and in vivo, which could be dramatically abrogated by the inhibitory CpG ODN. Our findings indicated that the TLR9 signaling could promote the tumor progression of human tumor cells, which might provide novel insight into the implications for CpG based anti-tumor therapies.

Promising novel immunotherapies and combinations for prostate cancer

The field of therapeutic cancer vaccines is currently in a state of active preclinical and clinical investigation, and certain novel therapies involving tumor immunotherapy have recently come to the forefront of prostate cancer research. While no therapeutic cancer vaccine has yet been approved by the US FDA, recent findings have demonstrated that new paradigms of combination therapies involving vaccines, employed in clinical trials with appropriate design and end points, may ultimately lead to cancer vaccines being used to treat various malignancies. Several characteristics of prostate cancer make it an ideal target for immunotherapy. Its relative indolence allows sufficient time to generate immune responses, which usually take weeks or months to mount. In addition, prostate cancer-associated antigens direct the immune response to prostate cancer cells, thus sparing normal tissue. This review focuses on the future of promising new vaccines and novel perspectives in the treatment of prostate cancer.

Toll-like receptor 9 (TLR9) agonists in the treatment of cancer

Although still early in clinical development, agonists of Toll-like receptor 9 (TLR9) have demonstrated potential for the treatment of cancer. TLR9 agonists directly induce activation and maturation of plasmacytoid dendritic cells and enhance differentiation of B cells into antibody-secreting plasma cells. Preclinical and early clinical data support the use of TLR9 agonists in patients with solid tumors and hematologic malignancies. In preclinical studies, TLR9 agonists have shown activity not only as monotherapy, but also in combination with multiple other therapies, including vaccines, antibodies, cellular therapies, other immunotherapies, antiangiogenic agents, radiotherapy, cryotherapy and some chemotherapies. Phase I and II clinical trials have indicated that these agents have antitumor activity as single agents and enhance the development of antitumor T-cell responses when used as therapeutic vaccine adjuvants. The activity and safety of these novel anticancer agents are being explored in a wide range of tumor types as part of a variety of therapeutic strategies with the goal of harnessing the immune response to fight cancer.

Phase I trial of toll-like receptor 9 agonist PF-3512676 with and following rituximab in patients with recurrent indolent and aggressive non Hodgkin's lymphoma

PURPOSE

PF-3512676 (formerly CpG 7909) is a novel Toll-like receptor 9-activating oligonucleotide with single-agent antitumor activity that augments preclinical rituximab efficacy. This Phase I trial was designed to investigate the safety, tolerability, and preliminary antitumor activity of PF-3512676 in combination with rituximab.

EXPERIMENTAL DESIGN

Patients with relapsed/refractory CD20+ B cell non-Hodgkin's lymphoma received i.v. rituximab (375 mg/m2/week for 4 weeks) and PF-3512676 weekly for 4 weeks either i.v. (0.04, 0.16, 0.32, or 0.48 mg/kg) or s.c. (0.01, 0.04, 0.08, or 0.16 mg/kg). An additional extended-treatment cohort received 4 weeks of 0.24 mg/kg s.c. PF-3512676 in combination with rituximab followed by s.c. PF-3512676 alone weekly for 20 weeks.

RESULTS

Patients (N = 50) had received a median of three prior therapies (range, 1-11) including rituximab in 80% of patients. Treatment-related adverse events occurred in 11 of 19 (58%) i.v. patients, 15 of 19 (79%) s.c. patients, and all 12 patients in the extended-treatment cohort. Most common adverse events were mild to moderate systemic flu-like symptoms and injection-site reactions (s.c. cohorts only). Grade 3/4 neutropenia occurred in four patients. Objective responses occurred in 12 of 50 (24%) patients overall and in 6 of 12 (50%) patients in the extended-treatment cohort, including 2 patients with rituximab-refractory disease.

CONCLUSION

Brief or extended-duration PF-3512676 can be safely administered in combination with rituximab in patients with relapsed/refractory non-Hodgkin's lymphoma.

Toll like receptor-9 agonists stimulate prostate cancer invasion in vitro

BACKGROUND

Toll-like receptor 9 (TLR9) recognizes microbial DNA. In addition to immune cells, TLR9 expression has been detected in various cancer cells. We showed recently that TLR9 agonistic CpG-oligonucleotides (CpG-ODNs) induce matrix metalloproteinase-13 (MMP-13)-mediated invasion in TLR9-expressing (TLR9(+)) breast cancer cells. We investigated here TLR9 expression and function in human prostate cancer (CaP) cells.

METHODS

TLR9 expression was detected with Western blotting and immunohistochemistry. Invasion was studied with Matrigel-assays. MMP-13 was assayed with ELISA.

RESULTS

Human CaP cell lines and clinical samples exhibit various levels of TLR9 expression. Treatment of TLR9(+), but not TLR9(-) CaP cells with CpG-ODNs or bacterial DNA increased their invasion, which was inhibited with chloroquine. CpG-ODN-treatment also increased MMP-13 activity and neutralizing anti-MMP-13 antibody prevented CpG-ODN-induced invasion in TLR9(+) CaP cells. Estradiol up-regulated TLR9 expression in LnCaP cells.

CONCLUSIONS

TLR9-mediated invasion may represent a novel mechanism through which infections promote prostate cancer.

IFN-gamma negatively regulates CpG-induced IL-10 in bone marrow-derived dendritic cells

Dendritic cells (DCs) are important players in the regulation of Th1- and Th2-dominated immune responses. In these studies we showed that IFN-gamma, the key mediator of Th1 immunity, actively suppressed the production of IL-10 in murine DCs when activated with LPS or CpG. Our analysis revealed that both LPS and CpG induced IL-10 and IL-12 production but that the presence of IFN-gamma, in a dose-dependent manner, suppressed the production of IL-10 while enhancing that of IL-12. The observed inhibition of IL-10 production was independent of IL-12. Experiments performed with STAT-1 knockout mice demonstrated that the primary production of IL-12 induced by CpG was STAT-1 dependent, whereas the production of IL-10 was not. This finding was confirmed by the observation that CpG-induced IL-12 production could be inhibited by anti-IFN-beta Abs, whereas CpG-induced IL-10 production could not be inhibited. These data also demonstrated that the inhibitory effect of IFN-gamma on IL-10 expression was STAT-1 dependent and transcriptionally regulated. Thus, DCs respond to CpG by producing proinflammatory and anti-inflammatory cytokines such as IL-12 and IL-10, respectively, and IFN-gamma acts to not only enhance IL-12 but also to inhibit IL-10 production. The current data demonstrate a novel pathway for IFN-gamma-mediated immunoregulation and suggest that IFN-gamma-dependent suppression of IL-10 production by DCs may be involved in the antagonism between Th1 and Th2 patterns of immune reactivity.

Immunomodulatory oligonucleotides as novel therapy for breast cancer: pharmacokinetics, in vitro and in vivo anticancer activity, and potentiation of antibody therapy

Oligonucleotides containing CpG motifs and immunomodulatory oligonucleotides (IMO) containing a synthetic immunostimulatory dinucleotide and a novel DNA structure have been suggested to have potential for the treatment of various human diseases. In the present study, a newly designed IMO was evaluated in several models of human (MCF-7 and BT474 xenograft) and murine (4T1 syngeneic) breast cancer. Pharmacokinetics studies of the IMO administered by s.c., i.v., p.o., or i.p. routes were also accomplished. The IMO was widely distributed to various tissues by all four routes, with s.c. administration yielding the highest concentration in tumor tissue. The IMO inhibited the growth of tumors in all three models of breast cancer, with the lowest dose of the IMO inhibiting MCF-7 xenograft tumor growth by >40%. Combining the IMO with the anticancer antibody, Herceptin, led to potent antitumor effects, resulting in >96% inhibition of tumor growth. The IMO also exerted in vitro antitumor activity, as measured by cell growth, apoptosis, and proliferation assays in the presence of Lipofectin. This is the first report of the pharmacokinetics of this agent in normal and tumor-bearing mice. Based on the present results, we believe that the IMO is a good candidate for clinical development for breast cancer therapy used either alone or in combination with conventional cancer therapeutic agents.

Toll-like receptor agonists in the treatment of chronic lymphocytic leukemia

Advances in our understanding of the Toll-like receptors (TLRs) have led to the identification of several agonists that are suitable for clinical development. Chronic lymphocytic leukemia (CLL) may be especially amenable to TLR agonists because it is an immunologically susceptible tumor with strong expression of several TLRs, particularly TLR-7 and TLR-9. TLR agonists may indirectly clear CLL cells by enhancing the activity of natural killer and tumor-reactive T cells, or by altering the tumor microenvironment and inhibiting angiogenesis. However, signaling pathways can be activated directly in CLL cells by TLR-7 and TLR-9 agonists, leading to the production of cytokines and costimulatory molecules in a manner that is dependent on the underlying cytogenetic abnormalities, but rendering the tumor cells more sensitive to killing by cytotoxic T cells, immunotoxins and some chemotherapeutic drugs. Imidazoquinolines are TLR-7 agonists with strong local activity against CLL, and phase I trials of systemically administered imidazoquinolines (and also cytosine-phosphate-guanosine oligonucleotides that are TLR-9 agonists) are currently ongoing at different centers. The potential importance of these TLR agonists in the treatment of CLL is suggested by their ability to sensitize tumor cells to cytotoxic agents, and their future probably lies in combination with radiotherapies, chemotherapies, monoclonal antibodies and cancer vaccines.

Enzyme-catalysed assembly of DNA hydrogel

DNA is a remarkable polymer that can be manipulated by a large number of molecular tools including enzymes. A variety of geometric objects, periodic arrays and nanoscale devices have been constructed. Previously we synthesized dendrimer-like DNA and DNA nanobarcodes from branched DNA via ligases. Here we report the construction of a hydrogel entirely from branched DNA that are three-dimensional and can be crosslinked in nature. These DNA hydrogels were biocompatible, biodegradable, inexpensive to fabricate and easily moulded into desired shapes and sizes. The distinct difference of the DNA hydrogel to other bio-inspired hydrogels (including peptide-based, alginate-based and DNA (linear)-polyacrylamide hydrogels) is that the crosslinking is realized via efficient, ligase-mediated reactions. The advantage is that the gelling processes are achieved under physiological conditions and the encapsulations are accomplished in situ-drugs including proteins and even live mammalian cells can be encapsulated in the liquid phase eliminating the drug-loading step and also avoiding denaturing conditions. Fine tuning of these hydrogels is easily accomplished by adjusting the initial concentrations and types of branched DNA monomers, thus allowing the hydrogels to be tailored for specific applications such as controlled drug delivery, tissue engineering, 3D cell culture, cell transplant therapy and other biomedical applications.

Cancer vaccines: preclinical studies and novel strategies

The development of cancer vaccines, aimed to enhance the immune response against a tumor, is a promising area of research. A better understanding of both the molecular mechanisms that govern the generation of an effective immune response and the biology of a tumor has contributed to substantial progress in the field. Areas of intense investigation in cancer immunotherapy will be discussed here, including: (1) the discovery and characterization of novel tumor antigens to be used as targets for vaccination; (2) the investigation of different vaccine-delivery modalities such as cellular-based vaccines, protein- and peptide-based vaccines, and vector-based vaccines; (3) the characterization of biological adjuvants to further improve the immunogenicity of a vaccine; and (4) the investigation of multimodal therapies where vaccines are being combined with other oncological treatments such as radiation and chemotherapy. A compilation of data from preclinical studies conducted in vitro as well as in animal models is presented here. The results from these studies would certainly support the development of new vaccination strategies toward cancer vaccines with enhanced clinical efficacy.

Toll-like receptor 2-mediated human B cell differentiation

Human B cells likely have a major role in the adjuvant activity of Toll-like receptor (TLR) 9 agonists by enhancing innate and adaptive immune responses. As several TLR2 ligands are promising vaccine adjuvant candidates, our aim was to characterize the effects of TLR2 stimulation on human B cell activation and differentiation using cells derived from healthy peripheral blood (PB), spleen, and diseased tonsils. We found a subset of partially differentiated TLR2+ PB and splenic B cells which responds to TLR2 agonists by mediating events involved in germinal center formation, such as upregulating CD77 and secreting chemokines. Furthermore, we show that TLR2-activated monocytes induce B cells to secrete significant quantities of IgM. Finally, activated TLR2+ B cells from tonsils are induced to secrete IgM directly by TLR2 ligands. Thus, TLR2 is likely involved in specific B cell-mediated functions and may be a viable vaccine adjuvant target in humans.

Toll-like receptor 9 agonists promote cellular invasion by increasing matrix metalloproteinase activity

Toll-like receptor 9 (TLR9) recognizes microbial DNA. We show here that TLR9 protein is expressed in human breast cancer cells and clinical breast cancer samples. Stimulation of TLR9-expressing breast cancer cells with the TLR9 agonistic CpG oligonucleotides (1-10 mumol/L) dramatically increased their in vitro invasion in both Matrigel assays and three-dimensional collagen cultures. Similar effects on invasion were seen in TLR9-expressing astrocytoma and glioblastoma cells and in the immortalized human breast epithelial cell line MCF-10A. This effect was not, however, dependent on the CpG content of the TLR9 ligands because the non-CpG oligonucleotides induced invasion of TLR9-expressing cells. CpG or non-CpG oligonucleotide-induced invasion in MDA-MB-231 cells was blunted by chloroquine and they did not induce invasion of TLR9(-) breast cancer cells. Treatment of MDA-MB-231 cells with CpG or non-CpG oligonucleotides induced the formation of approximately 50-kDa gelatinolytic band in zymograms. This band and the increased invasion were abolished by a matrix metalloproteinase (MMP) inhibitor GM6001 but not by a serine proteinase inhibitor aprotinin. Furthermore, CpG oligonucleotide treatment decreased tissue inhibitor of metalloproteinase-3 expression and increased levels of active MMP-13 in TLR9-expressing but not TLR9(-) breast cancer cells without affecting MMP-8. Neutralizing anti-MMP-13 antibodies inhibited the CpG oligonucleotide-induced invasion. These findings suggest that infections may promote cancer progression through a novel TLR9-mediated mechanism. They also propose a new molecular target for cancer therapy, because TLR9 has not been associated with cancer invasiveness previously.

Antisense-based cancer therapeutics: are we there yet?

Despite significant advances that have been made in recent years, there is still an urgent need for novel, more effective and less toxic therapeutics for human cancer. Among many new molecular therapeutics being explored for cancer therapy, antisense oligonucleotides are a promising nucleic acid-based approach, with numerous antisense agents being evaluated in preclinical studies and several anticancer antisense drugs in clinical trials. Although there are still a few problems facing the development of antisense strategies for cancer therapy, with progress made in chemical modifications, target selection and drug delivery systems, antisense oligonucleotides are emerging as a novel approach to cancer therapy used alone or in combination with conventional treatments such as chemotherapy and radiation therapy.

MG7 mimotope-based DNA vaccination for gastric cancer

Gastric cancer is still one of the leading causes of cancer-related death worldwide. Prevention and treatment of gastric cancer through vaccination has been difficult owing to lack of a specific target and poor immunity. A number of vaccination strategies have been used to augment immune responses against gastric cancer and some progress has been made. In a series of studies, the authors have focused on gastric cancer vaccination approaches based on MG7 mimotopes, which are mimicry epitopes selected from phage-displayed oligopeptide libraries with a gastric cancer cell-specific monoclonal antibody, MG7-Ab. Strategies employed in these studies include viral or plasmid vectors in combination with carrier sequence or unmethylated CpG with synthetic peptides in nanoemulsion. The results demonstrated that MG7 mimotopes could effectively and specifically induce both cellular and humoral immune reactions and in vivo antitumor responses. In particular, a four-MG7 mimotope DNA vaccine was found to elicit much stronger antitumor immune responses in mice compared with its single-mimotope counterpart. These encouraging findings might pave the way for the development of novel MG7 antigen-based vaccination approaches for human gastric cancer. The review also discusses other immune-enhancing vaccination strategies for gastric cancer.

Toll-like receptors—novel targets in allergic airway disease (probiotics, friends and relatives)

Experimental and epidemiological studies enabled to hypothesize that stimulation of the immune system by selected microbial products may prevent or treat allergic diseases. According to recent advances in molecular immunology, this stimulation acts via group of conserved receptors present on antigen presenting cells, known as toll-like receptors (TLRs). These receptors play an essential role in antigen presentation and latter development of immune response into pro-allergic (Th2), cellular (Th1) or regulatory (Tr1) responses. Since toll-like receptors govern decisive points in immune regulation, an extensive research focuses on agents interfering with their immunomodulatory activities. In this report, we review information on the potential use of microbial products in allergy prevention and therapy, which are believed to target toll-like receptor network. Current toll-like receptor-based approaches, as well as potential use of lipopolysaccharide (and derivates), oligonucleotides, mycobacteria, bacterial extracts, and probiotics are discussed herein.

Progress in the development of nucleic acid therapeutics

Abnormal gene expression is a hallmark of many diseases. Gene-specific downregulation of aberrant genes could be useful therapeutically and potentially less toxic than conventional therapies due its specificity. Over the years, many strategies have been proposed for silencing gene expression in a gene-specific manner. Three major approaches are antisense oligonucleotides (AS-ONs), ribozymes/DNAzymes, and RNA interference (RNAi). In this brief review, we will discuss the successes and shortcomings of these three gene-silencing methods, and the approaches being taken to improve the effectiveness of antisense molecules. We will also provide an overview of some of the clinical applications of antisense therapy.

Bovine toll-like receptor 9: a comparative analysis of molecular structure, function and expression

Non-methylated CpG motifs, present in viral and bacterial DNA, are one of many pathogen-associated molecular patterns (PAMP) recognized by the mammalian innate immune system. Recognition of this PAMP occurs through a specific interaction with toll-like receptor 9 (TLR9) and this interaction can induce cytokine responses that influence both innate and adaptive immune responses. Previous investigations determined that both the flanking sequences in synthetic CpG oligodeoxynucleotides (CpG ODN) and the cellular pattern of TLR9 expression can influence species-specific responses to CpG ODN. Therefore, the structure, function and cellular distribution of bovine TLR9 were compared with what is known for mice and human. Analysis of the bovine TLR9 gene revealed greater sequence homology between cattle and humans than cattle and mice Similar CpG motifs induced optimal activation of both human and bovine leukocytes and these motifs were distinct from those which activated mouse leukocytes. Functional analyses with CpG ODN stimulated bovine blood leukocytes revealed that class A CpG ODN were more potent inducers of interferon-alpha (IFN-alpha) than class B CpG ODN. Furthermore, magnetic activated cell sorting of bovine blood leukocyte subpopulations implicated dendritic cells but not monocytes in the regulation of CpG ODN-induced IFN secretion. Thus, the cellular pattern of CpG ODN-induced responses in cattle shared many similarities with human leukocytes. Collectively, these analyses revealed substantial conservation of TLR9 structure and TLR9 function in blood leukocytes of humans, cattle and other domestic species.

The role of natural killer cells in tumor control—effectors and regulators of adaptive immunity

Natural killer (NK) cells are the primary effector cells of the innate immune system and have a well-established role in tumor rejection in a variety of spontaneous and induced cancer models. NK cell function is regulated by a complex balance of inhibitory and activating signals that allow them to selectively target and kill cells that display an abnormal pattern of cell surface molecules, while leaving normal healthy cells unharmed. In this review we discuss NK cell function, the role of NK cells in cancer therapies, the emerging concept of bi-directional cross-talk between NK cells and dendritic cells, and the implications of these interactions for tumor immunotherapy.

Human lung cancer cells express functionally active Toll-like receptor 9

BACKGROUND

CpG-oligonucleotides (CpG-ODN), which induce signaling through Toll-like receptor 9 (TLR9), are currently under investigation as adjuvants in therapy against infections and cancer. CpG-ODN function as Th-1 adjuvants and are able to activate dendritic cells. In humans TLR9 has been described to be strongly expressed in B-lymphocytes, monocytes, plasmacytoid dendritic cells and at low levels in human respiratory cells. We determined whether a direct interaction of bacterial DNA with the tumor cells themselves is possible and investigated the expression and function of TLR9 in human malignant solid tumors and cell lines. TLR9 expression by malignant tumor cells, would affect treatment approaches using CpG-ODN on the one hand, and, on the other hand, provide additional novel information about the role of tumor cells in tumor-immunology.

METHODS

The expression of TLR9 in HOPE-fixed non-small lung cancer, non-malignant tissue and tumor cell lines was assessed using immunohistochemistry, confocal microscopy, in situ hybridization, RT-PCR and DNA-sequencing. Apoptosis and chemokine expression was detected by FACS analysis and the Bio-Plex system.

RESULTS

We found high TLR9 signal intensities in the cytoplasm of tumor cells in the majority of lung cancer specimens as well as in all tested tumor cell lines. In contrast to this non-malignant lung tissues showed only sporadically weak expression. Stimulation of HeLa and A549 cells with CpG-ODN induced secretion of monocyte chemoattractant protein-1 and reduction of spontaneous and tumor necrosis factor-alpha induced apoptosis.

CONCLUSIONS

Here we show that TLR9 is expressed in a selection of human lung cancer tissues and various tumor cell lines. The expression of functionally active TLR9 in human malignant tumors might affect treatment approaches using CpG-ODN and shows that malignant cells can be regarded as active players in tumor-immunology.

Vaccination strategies for the treatment and prevention of cervical cancer

PURPOSE OF REVIEW

Immunotherapy of HPV-induced premalignant anogenital lesions and cervical cancer has made impressive progress. HPV as causative agent is targeted by prophylactic and therapeutic vaccination strategies. Preclinical and clinical studies have shown induction of natural and/or vaccine-induced immune responses. This review will summarize the status of vaccine development and clinical testing published since March 2003.

RECENT FINDINGS

For prophylactic vaccines there is first clinical evidence of effectivity (ie, 100% protection from HPV infection and dysplasia by virus-like particle (VLP) vaccine-induced neutralizing antibodies). Also, therapeutic vaccines have entered clinical evaluation. While prophylactic VLP vaccines are immunogenic per se, therapeutic vaccines will need further adjuvants to guide T cell differentiation, expansion, survival, and homing to tumor sites. To enhance clinical outcome of successful T cell induction in patients, the susceptibility of the tumor cells for lysis must be addressed in the future, since tumor immune evasion is a severe problem in cervical cancer.

SUMMARY

While successful prophylactic HPV vaccines have entered large clinical trials, therapeutic HPV vaccines, in spite of T cell induction, lack clinical responses due to the problem of tumor immune evasion. Adjuvants for systemic and local immune modulation will be mandatory for effective therapy.

Construction, stability, and activity of multivalent circular anticoagulant aptamers

Here we describe the design and construction of multivalent circular DNA aptamers. Four aptameric binding motifs directed at blood-borne targets are used as a model set from which larger, multidomain aptamers are constructed in a straightforward manner. Intra- or intermolecular ligation of precursor oligonucleotides provides a stabilizing mechanism against degradation by the predominant exonuclease activity of blood products without the need for post-selection chemical modification. In many cases, circular DNA aptamer half-lives are extended beyond 10 h in serum and plasma, making such constructs viable for therapeutic and diagnostic applications. Duplexes and three-way junctions are used as scaffold architectures around which two, three, or four aptameric motifs can be arranged in a structurally defined manner, giving rise to improved binding characteristics through stability and avidity gains. Circular aptamers targeted against thrombin display improved anticoagulant potency with EC50 values 2-3-fold better than those of the canonical GS-522 thrombin DNA aptamer. Intrinsic duplex regions provide an opportunity to incorporate additional transcription factor binding motifs, whereas ancillary loops can be used to provide further functionality. These anticoagulant aptamers provide a starting point for merging the principles of DNA nanotechnology with aptameric functions.