X-shaped DNA potentiates therapeutic efficacy in colitis-associated colon cancer through dual activation of TLR9 and inflammasomes

Microbial sensing in the intestine

The gut microbiota plays a key role in host health and disease, particularly through their interactions with the immune system. Intestinal homeostasis is dependent on the symbiotic relationships between the host and the diverse gut microbiota, which is influenced by the highly co-evolved immune-microbiota interactions. The first step of the interaction between the host and the gut microbiota is the sensing of the gut microbes by the host immune system. In this review, we describe the cells of the host immune system and the proteins that sense the components and metabolites of the gut microbes. We further highlight the essential roles of pattern recognition receptors (PRRs), the G protein-coupled receptors (GPCRs), aryl hydrocarbon receptor (AHR) and the nuclear receptors expressed in the intestinal epithelial cells (IECs) and the intestine-resident immune cells. We also discuss the mechanisms by which the disruption of microbial sensing because of genetic or environmental factors causes human diseases such as the inflammatory bowel disease (IBD).

Center backbone-rigidified DNA polygonal nanostructures and bottom face-templated polyhedral pyramids with structural stability in a complex biological medium

Due to the sequence programmability, good biocompatibility, versatile functionalities and vast sequence space, DNA oligonucleotides are considered to be ideal building blocks for the assembly of diverse nanostructures in one, two and three dimensions that are capable of engineering of multiple functional nucleic acids into a useful tool to implement intended tasks in biological and medical field. However, the construction of wireframe nanostructures consisting of only a few DNA strands remains quite challenging mainly because of the molecular flexibility-based uncontrollability of size and shape. In this contribution, utilizing gel electrophoretic analysis and atomic force microscopy, we demonstrate the modeling assembly technique for the construction of wireframe DNA nanostructures that can be divided into two categories: rigid center backbone-guided modeling (RBM) and bottom face-templated assembly (BTA) that are responsible for the construction of DNA polygons and polyhedral pyramids, respectively. The highest assembly efficiency (AE) is about 100%, while the lowest AE is not less than 50%. Moreover, when adding one edge for polygons or one side face for pyramids, we only need to add one oligonucleotide strand. Especially, the advanced polygons (e.g., pentagon and hexagon) of definite shape are for the first time constructed. Along this line, introduction of cross-linking strands enables the hierarchical assembly of polymer polygons and polymer pyramids. These wireframe DNA nanostructures exhibit the substantially enhanced resistance to nuclease degradation and maintain their structural integrity in fetal bovine serum for several hours even if the vulnerable nicks are not sealed. The proposed modeling assembly technique represents important progress toward the development of DNA nanotechnology and is expected to promote the application of DNA nanostructures in biological and biomedical fields. STATEMENT OF SIGNIFICANCE: DNA oligonucleotides are considered to be ideal building blocks for the assembly of diverse nanostructures. However, the construction of wireframe nanostructures consisting of only a few DNA strands remains quite challenging. In this contribution, we demonstrate the modeling technique for the construction of different wireframe DNA nanostructures: rigid center backbone-guided modeling (RBM) and bottom face-templated assembly (BTA) that are responsible for the assembly of DNA polygons and polyhedral pyramids, respectively. Moreover, cross-linking strands enables the hierarchical assembly of polymer polygons and polymer pyramids. These wireframe DNA nanostructures exhibit the substantially enhanced resistance to nuclease degradation and maintain their structural integrity in fetal bovine serum for several hours, promoting the application of DNA nanostructures in biological and biomedical fields.

Toll-like receptor-targeted anti-tumor therapies: Advances and challenges

Toll-like receptors (TLRs) are pattern recognition receptors, originally discovered to stimulate innate immune reactions against microbial infection. TLRs also play essential roles in bridging the innate and adaptive immune system, playing multiple roles in inflammation, autoimmune diseases, and cancer. Thanks to the immune stimulatory potential of TLRs, TLR-targeted strategies in cancer treatment have proved to be able to regulate the tumor microenvironment towards tumoricidal phenotypes. Quantities of pre-clinical studies and clinical trials using TLR-targeted strategies in treating cancer have been initiated, with some drugs already becoming part of standard care. Here we review the structure, ligand, signaling pathways, and expression of TLRs; we then provide an overview of the pre-clinical studies and an updated clinical trial watch targeting each TLR in cancer treatment; and finally, we discuss the challenges and prospects of TLR-targeted therapy.

Toosendanin activates caspase-1 and induces maturation of IL-1β to inhibit type 2 porcine reproductive and respiratory syndrome virus replication via an IFI16-dependent pathway

Porcine reproductive and respiratory syndrome virus (PRRSV) is a prevalent and endemic swine pathogen which causes significant economic losses in the global swine industry. Multiple vaccines have been developed to prevent PRRSV infection. However, they provide limited protection. Moreover, no effective therapeutic drugs are yet available. Therefore, there is an urgent need to develop novel antiviral strategies to prevent PRRSV infection and transmission. Here we report that Toosendanin (TSN), a tetracyclic triterpene found in the bark or fruits of Melia toosendan Sieb. et Zucc., strongly suppressed type 2 PRRSV replication in vitro in Marc-145 cells and ex vivo in primary porcine alveolar macrophages (PAMs) at sub-micromolar concentrations. The results of transcriptomics revealed that TSN up-regulated the expression of IFI16 in Marc-145 cells. Furthermore, we found that IFI16 silencing enhanced the replication of PRRSV in Marc-145 cells and that the anti-PRRSV activity of TSN was dampened by IFI16 silencing, suggesting that the inhibition of TSN against PRRSV replication is IFI16-dependent. In addition, we showed that TSN activated caspase-1 and induced maturation of IL-1β in an IFI16-dependent pathway. To verify the role of IL-1β in PRRSV infection, we analyzed the effect of exogenous rmIL-1β on PRRSV replication, and the results showed that exogenous IL-1β significantly inhibited PRRSV replication in Marc-145 cells and PAMs in a dose-dependent manner. Altogether, our findings indicate that TSN significantly inhibits PRRSV replication at very low concentrations (EC₅₀: 0.16–0.20 μM) and may provide opportunities for developing novel anti-PRRSV agents.

Oxidized Phospholipids in Tumor Microenvironment Stimulate Tumor Metastasis via Regulation of Autophagy

Oxidized phospholipids are well known to play physiological and pathological roles in regulating cellular homeostasis and disease progression. However, their role in cancer metastasis has not been entirely understood. In this study, effects of oxidized phosphatidylcholines such as 1-palmitoyl-2-(5-oxovaleroyl)-sn-glycero-3-phosphocholine (POVPC) on epithelial-mesenchymal transition (EMT) and autophagy were determined in cancer cells by immunoblotting and confocal analysis. Metastasis was analyzed by a scratch wound assay and a transwell migration/invasion assay. The concentrations of POVPC and 1-palmitoyl-2-glutaroyl-sn-glycero-phosphocholine (PGPC) in tumor tissues obtained from patients were measured by LC-MS/MS analysis. POVPC induced EMT, resulting in increase of migration and invasion of human hepatocellular carcinoma cells (HepG2) and human breast cancer cells (MCF7). POVPC induced autophagic flux through AMPK-mTOR pathway. Pharmacological inhibition or siRNA knockdown of autophagy decreased migration and invasion of POVPC-treated HepG2 and MCF7 cells. POVPC and PGPC levels were greatly increased at stage II of patient-derived intrahepatic cholangiocarcinoma tissues. PGPC levels were higher in malignant breast tumor tissues than in adjacent nontumor tissues. The results show that oxidized phosphatidylcholines increase metastatic potential of cancer cells by promoting EMT, mediated through autophagy. These suggest the positive regulatory role of oxidized phospholipids accumulated in tumor microenvironment in the regulation of tumorigenesis and metastasis.

Renal cancer-derived exosomes induce tumor immune tolerance by MDSCs-mediated antigen-specific immunosuppression

Backgound

Although Myeloid-derived suppressor cells (MDSCs) have a prominent ability to suppress the immune responses of T lymphocytes and propel tumor immune escape, a lack of profound systemic immunesuppression in tumor-bearing mice and tumor patients. The underlying mechanism of these remains unclear.

Methods

For this purpose, renal cancer-derived exosomes (RDEs) were first labeled with PKH67 and been observed the internalization by MDSCs. Flow cytometry analysis showed the proportion and activity change of MDSCs in spleen and bone marrow induced by RDEs. Further, western blot experiments were used to verify triggered mechanism of MDSCs by RDEs. Finally, proliferation and cytotoxicity of cytotoxic T lymphocytes (CTLs) co-cultured with MDSCs in vitro and a series of experiments in vivo were performed to demonstrate the specific inhibitory effect of RDEs-induced MDSCs.

Results

This study suggested that RDEs crucially contributed to presenting antigenic information, activating and driving specific immunosuppressive effect to MDSCs. HSP70, which is highly expressed in RDEs, initiate this process in a toll like receptor 2 (TLR2)-dependent manner. Importantly, RDEs-induced MDSCs could exert an antigen-specific immunosuppression effect on CTL and specific promote renal tumors-growth and immune escape in consequence.

Conclusion

The immunosuppression mediated by MDSCs which is induced by RDEs is antigen-specific. HSP70, which is highly expressed in RDEs, plays a pivotal role in this process. Targeted abrogating the function of MDSCs, or eliminating the expression of HSP70 in exosomes, or blocking the crosstalk between them provides a new direction and theoretical support for future immunotherapy.

Interleukin-1β and Cancer

Within a tumor, IL-1β is produced and secreted by various cell types, such as immune cells, fibroblasts, or cancer cells. The IL1B gene is induced after “priming” of the cells and a second signal is required to allow IL-1β maturation by inflammasome-activated caspase-1. IL-1β is then released and leads to transcription of target genes through its ligation with IL-1R1 on target cells. IL-1β expression and maturation are guided by gene polymorphisms and by the cellular context. In cancer, IL-1β has pleiotropic effects on immune cells, angiogenesis, cancer cell proliferation, migration, and metastasis. Moreover, anti-cancer treatments are able to promote IL-1β production by cancer or immune cells, with opposite effects on cancer progression. This raises the question of whether or not to use IL-1β inhibitors in cancer treatment.

DNA Nanostructure as an Efficient Drug Delivery Platform for Immunotherapy

Immunotherapy has received increasing attention due to its low potential side effects and high specificity. For instance, cancer immunotherapy has achieved great success. CpG is a well-known and commonly used immunotherapeutic and vaccine adjuvant, but it has the disadvantage of being unstable and low in efficacy and needs to be transported through an effective nanocarrier. With perfect structural programmability, permeability, and biocompatibility, DNA nanostructures are one of the most promising candidates to deliver immune components to realize immunotherapy. However, the instability and low capability of the payload of ordinary DNA assemblies limit the relevant applications. Consequently, DNA nanostructure with a firm structure, high drug payloads is highly desirable. In the paper, the latest progress of biostable, high-payload DNA nanoassemblies of various structures, including cage-like DNA nanostructure, DNA particles, DNA polypods, and DNA hydrogel, are reviewed. Cage-like DNA structures hold drug molecules firmly inside the structure and leave a large space within the cavity. These DNA nanostructures use their unique structure to carry abundant CpG, and their biocompatibility and size advantages to enter immune cells to achieve immunotherapy for various diseases. Part of the DNA nanostructures can also achieve more effective treatment in conjunction with other functional components such as aPD1, RNA, TLR ligands.

Hybrid material of structural DNA with inorganic compound: synthesis, applications, and perspective

Owing to its precise manipulation in nanoscale, DNA as a genetic code becomes a promising and generic material in lots of nanotechnological outstanding exploitations. The nanoscale assembly of nucleic acids in aqueous solution has showed very remarkable capability that is not achievable from any other material resources. In the meantime, their striking role played by effective intracellular interactions have been identified, making these more attractive for a variety of biological applications. Lately, a number of interesting attempts have been made to augment their marvelous diagnostic and therapeutic capabilities, as being integrated with inorganic compounds involving gold, iron oxide, quantum dot, upconversion, etc. It was profoundly studied how structural DNA-inorganic hybrid materials have complemented with each other in a synergistic way for better-graded biological performances. Such hybrid materials consisting of both structural DNAs and inorganics are gradually receiving much attention as a practical and future-oriented material substitute. However, any special review articles highlighting the significant and innovative materials have yet to be published. At the first time, we here demonstrate novel hybrid complexes made of structural DNAs and inorganics for some practical applications.

Immunostimulatory activity of Y-shaped DNA nanostructures mediated through the activation of TLR9

Immunostimulatory oligodeoxynucleotides (DNAs) have been widely studied in pharmaceutical and biomedical research fields for applications in cancer immunotherapy and vaccination. Toll-like receptors (TLRs) are critical for the instruction and orchestration of the host immune system composed of innate and adaptive immunity. In particular, TLR9 responds to DNAs with unmethylated deoxycytosine-deoxyguanosine (CpG) motifs, thereby inducing the activation of innate immune cells, such as dendritic cells, and consequently, adaptive immune cells. In this study, we developed two kinds of Y-shaped double-stranded DNA nanostructures (Y-DNAs), including a single unit composed of three DNA strands (Y_S-DNA) and a ligated multiunit complex formed by crosslinking each Y_S-DNA (Y_L-DNA), and investigated whether they have immunostimulatory activity in innate immune cells. Y_S-DNA and Y_L-DNA induced the production of immune cytokines such as IL-12 and TNF-α and the expression of costimulatory molecules such as CD80 and CD86 in primary mouse dendritic cells and macrophage cells (RAW264.7 cells). A Coprecipitation study demonstrated that Y_L-DNA was directly associated with TLR9. The induction of immune cytokines by Y_S-DNA and Y_L-DNA was abolished in TLR9-deficient primary mouse dendritic cells. The results demonstrated that Y-DNAs induced the activation of dendritic cells and macrophages mediated by the activation of TLR9, as shown by the expression of immune cytokines and costimulatory molecules. The results suggest that Y-DNA nanostructures provide a beneficial strategy for immunotherapy by modulating the immune system.

Functional-DNA-Driven Dynamic Nanoconstructs for Biomolecule Capture and Drug Delivery

The discovery of sequence-specific hybridization has allowed the development of DNA nanotechnology, which is divided into two categories: 1) structural DNA nanotechnology, which utilizes DNA as a biopolymer; and 2) dynamic DNA nanotechnology, which focuses on the catalytic reactions or displacement of DNA structures. Recently, numerous attempts have been made to combine DNA nanotechnologies with functional DNAs such as aptamers, DNAzymes, amplified DNA, polymer-conjugated DNA, and DNA loaded on functional nanoparticles for various applications; thus, the new interdisciplinary research field of "functional DNA nanotechnology" is initiated. In particular, a fine-tuned nanostructure composed of functional DNAs has shown immense potential as a programmable nanomachine by controlling DNA dynamics triggered by specific environments. Moreover, the programmability and predictability of functional DNA have enabled the use of DNA nanostructures as nanomedicines for various biomedical applications, such as cargo delivery and molecular drugs via stimuli-mediated dynamic structural changes of functional DNAs. Here, the concepts and recent case studies of functional DNA nanotechnology and nanostructures in nanomedicine are reviewed, and future prospects of functional DNA for nanomedicine are indicated.

Double-stranded phosphodiester cytosine-guanine oligodeoxynucleotide complexed with calcium phosphate as a potent vaccine adjuvant for activating cellular and Th1-type humoral immunities

Conventional class B cytosine-guanine (CpG) (CpG-B) oligodeoxynucleotide (ODNs) consisting of a single-stranded (ss) phosphorothioate (PT) backbone (ss CpG-B-PT) is converted from a proinflammatory cytokine inducer to a type-I interferon (IFN) inducer when complexed with cationic materials. In this study, we designed ss CpG-B and double-stranded (ds) CpG-B ODNs with a phosphodiester (PD) backbone (ss CpG-B-PD and ds CpG-B-PD, respectively) that became type-I IFN inducers upon complexation with Lipofectamine 2000 (Lipo), a cationic liposome. The ds CpG-B-PD complex induced higher IFN-β expression in mouse macrophage-like RAW264 cells than ss CpG-B-PD and ss CpG-B-PT complexes. The fold induction of IFN-β increased with the number of CpG motifs in ds CpG-B-PD, and a complex of ds CpG-B-PD consisting of 72 base pairs with nine CpG motifs (ds CpG-B72-PD) and Lipo showed the highest capacity to induce IFN-β. The materials and method used for complexation influenced the degree of IFN-β induction: ds CpG-B72-PD entrapped by calcium phosphate (CaP) (ds CpG-B72-PD/CaP) showed a higher induction capacity than ds CpG-B72-PD adsorbed onto the CaP surface. Entrapment of ds CpG-B72-PD by CaP also enhanced the induction of the proinflammatory cytokine interleukin-12. Vaccinating mice with ds CpG-B72-PD/CaP in conjunction with ovalbumin (OVA) increased the ratios of OVA-specific CD8⁺ T cells to total CD8⁺ T cells in peripheral blood and of OVA-specific IgG2a associated with helper T (Th)1 cells to OVA-specific IgG1 associated with Th2 cells. These results indicate that ds CpG-B72-PD/CaP is an effective vaccine adjuvant that can activate both cellular and Th1-type humoral immune responses.

Trial watch: Immunogenic cell death induction by anticancer chemotherapeutics

The expression "immunogenic cell death" (ICD) refers to a functionally unique form of cell death that facilitates (instead of suppressing) a T cell-dependent immune response specific for dead cell-derived antigens. ICD critically relies on the activation of adaptive responses in dying cells, culminating with the exposure or secretion of immunostimulatory molecules commonly referred to as "damage-associated molecular patterns". Only a few agents can elicit bona fide ICD, including some clinically established chemotherapeutics such as doxorubicin, epirubicin, idarubicin, mitoxantrone, bleomycin, bortezomib, cyclophosphamide and oxaliplatin. In this Trial Watch, we discuss recent progress on the development of ICD-inducing chemotherapeutic regimens, focusing on studies that evaluate clinical efficacy in conjunction with immunological biomarkers.

CpG oligodeoxynucleotide nanomedicines for the prophylaxis or treatment of cancers, infectious diseases, and allergies

Unmethylated cytosine-guanine dinucleotide-containing oligodeoxynucleotides (CpG ODNs), which are synthetic agonists of Toll-like receptor 9 (TLR9), activate humoral and cellular immunity and are being developed as vaccine adjuvants to prevent or treat cancers, infectious diseases, and allergies. Free CpG ODNs have been used in many clinical trials implemented to verify their effects. However, recent research has reported that self-assembled CpG ODNs, protein/peptide–CpG ODN conjugates, and nanomaterial–CpG ODN complexes demonstrate higher adjuvant effects than free CpG ODNs, owing to their improved uptake efficiency into cells expressing TLR9. Moreover, protein/peptide–CpG ODN conjugates and nanomaterial–CpG ODN complexes are able to deliver CpG ODNs and antigens (or allergens) to the same types of cells, which enables a higher degree of prophylaxis or therapeutic effect. In this review, the author describes recent trends in the research and development of CpG ODN nanomedicines containing self-assembled CpG ODNs, protein/peptide–CpG ODN conjugates, and nanomaterial–CpG ODN complexes, focusing mainly on the results of preclinical and clinical studies.