Enhancing the immune response and tumor suppression effect of antitumor vaccines adjuvanted with non-nucleotide small molecule STING agonist

Discovery of novel amidobenzimidazole derivatives as orally available small molecule modulators of stimulator of interferon genes for cancer immunotherapy

Stimulator of interferon genes (STING) agonists show promise as immunomodulatory agents for cancer therapy. In this study, we report the discovery of a novel orally available STING agonist, SAP-04, that exhibits potent immunomodulatory effects for cancer therapy. By optimizing the amidobenzimidazole core with various pyridine-based heterocyclic substituents, we identified a monomeric variant that displayed more efficient STING agonistic activity than the corresponding dimer. SAP-04 efficiently induced cytokine secretion related to innate immunity by directly binding of the compound to the STING protein, followed by sequential signal transduction for the STING signaling pathway and type I interferon (IFN) responses. Further pharmacological validation in vitro and in vivo demonstrated the potential utility of SAP-04 as an immunomodulatory agent for cancer therapy in vivo. The in vivo anticancer effect was observed in a 4T1 breast tumor syngeneic mouse model through oral administration of the compound. Our findings suggest a possible strategy for developing synthetically accessible monomeric variants as orally available STING agonists.

Computational screening of metalloporphyrin-based drug carriers for antitumor drug 5-fluorouracil

Developing novel nanoscale carriers for drug delivery is of great significance for improving treatment efficiency and reducing side effects of antitumor drugs. In view of the good biocompatibility and special affinity of porphyrin (PP) molecule to cancer cells, it was used to construct a series of metal-doped M@PP (M = Ca ∼ Zn) materials for the delivery of anticancer drug 5-fluorouracil (5-Fu) in this work. Our results reveal that 5-Fu is tightly adsorbed on M@PP (M = Ca ∼ V, Mn ∼ Co, and Zn) by chemisorption, but is physically adsorbed by M@PP (M = Cr, Ni, and Cu). The calculated electronic properties show that all these 5-Fu@[M@PP] (M = Ca ∼ Zn) complexes have both high stability and solubility. Among these 5-Fu@[M@PP] complexes, the chemical bond formed between 5-Fu and Ti@PP has the strongest covalent characteristic, resulting in the largest adsorption energy of -19.93 kcal/mol for 5-Fu@[Ti@PP]. In particular, 5-Fu@[Ti@PP] has the proper recovery time under the near-infrared light at body temperature, which further suggests that Ti@PP is the best drug carrier for 5-Fu. This study not only reveals the interaction strength and nature between 5-Fu and M@PP, but also confirmed the intriguing potential of Ti@PP as nano-carrier for drug delivery. However, further experimental research should be conducted to verify the conclusion obtained in this work.

Glycopolymers With On/Off Anchors: Confinement Effect on Regulating Dendritic Cells

Insufficient activation or over-activation of T cells due to the dendritic cells (DCs) state can cause negative effects on immunotherapy, making it crucial for DCs to maintain different states in different treatments. Polysaccharides are one of the most studied substances to promote DCs maturation. However, in many methods, optimizing the spatial dimension of the interaction between polysaccharides and cells is often overlooked. Therefore, in this study, a new strategy from the perspective of spatial dimension is proposed to regulate the efficacy of polysaccharides in promoting DCs maturation. An anchoring molecule (DMA) is introduced to existing glycopolymers for the confinement effect, and the effect can be turned off by oxidation of DMA. Among the prepared on-confined (PMD2 ), off-confined (PMD2 -O), and norm (PM2 ) glycopolymers, PMD2 and PMD2 -O show the best and worst results, respectively, in terms of the amount of binding to DCs and the effect on promoting DCs maturation. This sufficiently shows that the turn-on and off of confinement effect can regulate the maturation of DCs by polysaccharides. Based on the all-atom molecular dynamics (MD) simulation, the mechanism of difference in the confinement effect is explained. This simple method can also be used to regulate other molecule-cell interactions to guide cell behavior.

Adjuvant physiochemistry and advanced nanotechnology for vaccine development

Vaccines comprising innovative adjuvants are rapidly reaching advanced translational stages, such as the authorized nanotechnology adjuvants in mRNA vaccines against COVID-19 worldwide, offering new strategies to effectively combat diseases threatening human health. Adjuvants are vital ingredients in vaccines, which can augment the degree, extensiveness, and longevity of antigen specific immune response. The advances in the modulation of physicochemical properties of nanoplatforms elevate the capability of adjuvants in initiating the innate immune system and adaptive immunity, offering immense potential for developing vaccines against hard-to-target infectious diseases and cancer. In this review, we provide an essential introduction of the basic principles of prophylactic and therapeutic vaccination, key roles of adjuvants in augmenting and shaping immunity to achieve desired outcomes and effectiveness, and the physiochemical properties and action mechanisms of clinically approved adjuvants for humans. We particularly focus on the preclinical and clinical progress of highly immunogenic emerging nanotechnology adjuvants formulated in vaccines for cancer treatment or infectious disease prevention. We deliberate on how the immune system can sense and respond to the physicochemical cues (e.g., chirality, deformability, solubility, topology, and chemical structures) of nanotechnology adjuvants incorporated in the vaccines. Finally, we propose possible strategies to accelerate the clinical implementation of nanotechnology adjuvanted vaccines, such as in-depth elucidation of nano-immuno interactions, antigen identification and optimization by the deployment of high-dimensional multiomics analysis approaches, encouraging close collaborations among scientists from different scientific disciplines and aggressive exploration of novel nanotechnologies.

Tuning Bacterial Morphology to Enhance Anticancer Vaccination

Morphology tuning is a potent strategy to modulate physiological effects of synthetic biomaterials, but it is rarely explored in microbe-based biochemicals due to the lack of artificial adjustability. Inspired by the interesting phenomenon of microbial transformation, Escherichia coli is rationally adjusted into filamentous morphology-adjusted bacteria (MABac) via chemical stimulation to prepare a bacteria-based vaccine adjuvant/carrier. Inactivated MABac display stronger immunogenicity and special delivery patterns (phagosome escape and cytoplasmic retention) that are sharply distinct from the short rod-shaped bacteria parent (Bac). Transcriptomic study further offers solid evidence for deeply understanding the in vivo activity of MABac-based vaccine, which more effectively motivates multiple cytosolic immune pathways (such as NOD-like receptors and STING) and induces pleiotropic immune responses in comparison with Bac. Harnessing the special functions caused by morphology tuning, the MABac-based adjuvant/carrier significantly improves the immunogenicity and delivery profile of cancer antigens in vivo, thus boosting cancer-specific immunity against the melanoma challenge. This study validates the feasibility of tuning bacterial morphology to improve their biological effects, establishing a facile engineering strategy that upgrades bacterial properties and functions without complex procedures like gene editing.

Nanoparticle-Mediated STING Activation for Cancer Immunotherapy

As the first line of host defense against pathogenic infections, innate immunity plays a key role in antitumor immunotherapy. The cyclic GMP-AMP synthase (cGAS)-stimulator of interferon genes (STING) (cGAS-STING) pathway has attracted much attention because of the secretion of various proinflammatory cytokines and chemokines. Many STING agonists have been identified and applied into preclinical or clinical trials for cancer immunotherapy. However, the fast excretion, low bioavailability, nonspecificity, and adverse effects of the small molecule STING agonists limit their therapeutic efficacy and in vivo application. Nanodelivery systems with appropriate size, charge, and surface modification are capable of addressing these dilemmas. In this review, the mechanism of the cGAS-STING pathway is discussed and the STING agonists, focusing on nanoparticle-mediated STING therapy and combined therapy for cancers, are summarized. Finally, the future direction and challenges of nano-STING therapy are expounded, emphasizing the pivotal scientific problems and technical bottlenecks and hoping to provide general guidance for its clinical application.

Utilizing chemotherapy-induced tumor RNA nanoparticles to improve cancer chemoimmunotherapy

Chemotherapy has become a popular combination strategy to improve the response rate of immunotherapy since certain chemotherapeutic drugs kill tumor cells by an immunogenic cell death (ICD) pathway, which activates antitumor immune responses. Unfortunately, the synergistic effect of chemoimmunotherapy can be impaired due to the toxicities of chemotherapeutic agent-induced lymphatic depletion and immunosuppression. In this study, we present an approach to improve immunotherapy by using tumor RNA nanoparticles (RNA-NPs) where RNA is directly extracted from chemotherapy-treated cancer cells and then condensed by protamine via electrostatic interactions to form complexes. Such RNA-NPs can be effectively taken up by dendritic cells (DCs) in the draining lymph nodes after subcutaneous injection. Compared with noninduced tumor RNA nanoparticles (N-RNA-NPs), chemotherapy-induced tumor RNA nanoparticles (C-RNA-NPs) can significantly promote DC maturation and stimulate a stronger immune response against established CT-26 colon carcinoma. Besides, C-RNA-NPs can improve the efficacy of immune checkpoint blockade (ICB) therapy by facilitating the infiltration of intratumoral T cells and increasing the ratio of CD8⁺ T cells to regulatory T cells (Tregs). More importantly, the synergistic effect of chemoimmunotherapy is also enhanced by treatment with C-RNA-NPs. STATEMENT OF SIGNIFICANCE: Although immune checkpoint blockade therapy has been demonstrated to be effective in some advanced cancers, the low response rate has significantly limited its clinical application. To address this issue, a new strategy for improving cancer immunotherapy using chemotherapy-induced tumor RNA nanoparticles (C-RNA-NPs) is developed in this work. The proposed C-RNA-NPs could be captured by dendritic cells, which were then stimulated to the maturation status to initiate an anticancer immune response. Furthermore, the response rate to immunotherapy was significantly increased by promoting intratumoral T-cell infiltration and elevating the intratumoral ratio of CD8⁺ T cells to regulatory T cells after treatment with C-RNA-NPs. Therefore, C-RNA-NPs have the potential to improve cancer immunotherapy.

Current understanding of the cGAS-STING signaling pathway: Structure, regulatory mechanisms, and related diseases

The innate immune system protects the host from external pathogens and internal damage in various ways. The cGAS-STING signaling pathway, comprised of cyclic GMP-AMP synthase (cGAS), stimulator of interferon genes (STING), and downstream signaling adaptors, plays an essential role in protective immune defense against microbial DNA and internal damaged-associated DNA and is responsible for various immune-related diseases. After binding with DNA, cytosolic cGAS undergoes conformational change and DNA-linked liquid-liquid phase separation to produce 2'3'-cGAMP for the activation of endoplasmic reticulum (ER)-localized STING. However, further studies revealed that cGAS is predominantly expressed in the nucleus and strictly tethered to chromatin to prevent binding with nuclear DNA, and functions differently from cytosolic-localized cGAS. Detailed delineation of this pathway, including its structure, signaling, and regulatory mechanisms, is of great significance to fully understand the diversity of cGAS-STING activation and signaling and will be of benefit for the treatment of inflammatory diseases and cancer. Here, we review recent progress on the above-mentioned perspectives of the cGAS-STING signaling pathway and discuss new avenues for further study.

Detachable Liposomes Combined Immunochemotherapy for Enhanced Triple-Negative Breast Cancer Treatment through Reprogramming of Tumor-Associated Macrophages

Triple-negative breast cancer (TNBC) is an aggressive disease with a high recurrence rate and poor outcomes in clinic. In this study, inspired by the enriched innate immune cell type tumor-associated macrophages (TAMs) in TNBC, we proposed a matrix metalloprotease 2 (MMP2) responsive integrated immunochemotherapeutic strategy to deliver paclitaxel (PTX) and anti-CD47 (aCD47) by detachable immune liposomes (ILips). In the TNBC microenvironment, the "two-in-one" ILips facilitated MMP2-responsive release of aCD47 to efficiently polarize M2 macrophages toward the M1 phenotype to enhance phagocytosis against tumor cells and activate the systemic T cell immune response. Together with the immune effect, the detached PTX-loaded liposomes were internalized in MDA-MB-231 cells to synergistically inhibit tumor cell proliferation and metastasis. In the TNBC-bearing mouse model, PTX-loaded ILips demonstrated superior antitumor efficacy against TNBC and inhibited tumor recurrence. Our integrated strategy represents a promising approach to synchronously enhance immune response and tumor-killing effects, improving the therapeutic efficacy against TNBC.