The role of innate immune signals in antitumor immunity

Recruiting In Vitro Transcribed mRNA against Cancer Immunotherapy: A Contemporary Appraisal of the Current Landscape

Over 100 innovative in vitro transcribed (IVT)-mRNAs are presently undergoing clinical trials, with a projected substantial impact on the pharmaceutical market in the near future. Τhe idea behind this is that after the successful cellular internalization of IVT-mRNAs, they are subsequently translated into proteins with therapeutic or prophylactic relevance. Simultaneously, cancer immunotherapy employs diverse strategies to mobilize the immune system in the battle against cancer. Therefore, in this review, the fundamental principles of IVT-mRNA to its recruitment in cancer immunotherapy, are discussed and analyzed. More specifically, this review paper focuses on the development of mRNA vaccines, the exploitation of neoantigens, as well as Chimeric Antigen Receptor (CAR) T-Cells, showcasing their clinical applications and the ongoing trials for the development of next-generation immunotherapeutics. Furthermore, this study investigates the synergistic potential of combining the CAR immunotherapy and the IVT-mRNAs by introducing our research group novel, patented delivery method that utilizes the Protein Transduction Domain (PTD) technology to transduce the IVT-mRNAs encoding the CAR of interest into the Natural Killer (NK)-92 cells, highlighting the potential for enhancing the CAR NK cell potency, efficiency, and bioenergetics. While IVT-mRNA technology brings exciting progress to cancer immunotherapy, several challenges and limitations must be acknowledged, such as safety, toxicity, and delivery issues. This comprehensive exploration of IVT-mRNA technology, in line with its applications in cancer therapeutics, offers valuable insights into the opportunities and challenges in the evolving landscape of cancer immunotherapy, setting the stage for future advancements in the field.

Innovative breakthroughs facilitated by single-cell multi-omics: manipulating natural killer cell functionality correlates with a novel subcategory of melanoma cells

Background

Melanoma is typically regarded as the most dangerous form of skin cancer. Although surgical removal of in situ lesions can be used to effectively treat metastatic disease, this condition is still difficult to cure. Melanoma cells are removed in great part due to the action of natural killer (NK) and T cells on the immune system. Still, not much is known about how the activity of NK cell-related pathways changes in melanoma tissue. Thus, we performed a single-cell multi-omics analysis on human melanoma cells in this study to explore the modulation of NK cell activity.

Materials and methods

Cells in which mitochondrial genes comprised > 20% of the total number of expressed genes were removed. Gene ontology (GO), gene set enrichment analysis (GSEA), gene set variation analysis (GSVA), and AUCcell analysis of differentially expressed genes (DEGs) in melanoma subtypes were performed. The CellChat package was used to predict cell-cell contact between NK cell and melanoma cell subtypes. Monocle program analyzed the pseudotime trajectories of melanoma cells. In addition, CytoTRACE was used to determine the recommended time order of melanoma cells. InferCNV was utilized to calculate the CNV level of melanoma cell subtypes. Python package pySCENIC was used to assess the enrichment of transcription factors and the activity of regulons in melanoma cell subtypes. Furthermore, the cell function experiment was used to confirm the function of TBX21 in both A375 and WM-115 melanoma cell lines.

Results

Following batch effect correction, 26,161 cells were separated into 28 clusters and designated as melanoma cells, neural cells, fibroblasts, endothelial cells, NK cells, CD4+ T cells, CD8+ T cells, B cells, plasma cells, monocytes and macrophages, and dendritic cells. A total of 10137 melanoma cells were further grouped into seven subtypes, i.e., C0 Melanoma BIRC7, C1 Melanoma CDH19, C2 Melanoma EDNRB, C3 Melanoma BIRC5, C4 Melanoma CORO1A, C5 Melanoma MAGEA4, and C6 Melanoma GJB2. The results of AUCell, GSEA, and GSVA suggested that C4 Melanoma CORO1A may be more sensitive to NK and T cells through positive regulation of NK and T cell-mediated immunity, while other subtypes of melanoma may be more resistant to NK cells. This suggests that the intratumor heterogeneity (ITH) of melanoma-induced activity and the difference in NK cell-mediated cytotoxicity may have caused NK cell defects. Transcription factor enrichment analysis indicated that TBX21 was the most important TF in C4 Melanoma CORO1A and was also associated with M1 modules. In vitro experiments further showed that TBX21 knockdown dramatically decreases melanoma cells' proliferation, invasion, and migration.

Conclusion

The differences in NK and T cell-mediated immunity and cytotoxicity between C4 Melanoma CORO1A and other melanoma cell subtypes may offer a new perspective on the ITH of melanoma-induced metastatic activity. In addition, the protective factors of skin melanoma, STAT1, IRF1, and FLI1, may modulate melanoma cell responses to NK or T cells.

Characterization of a novel polysaccharide from Arca subcrenata and its immunoregulatory activities in vitro and in vivo

Arca subcrenata is an economical edible shellfish. A novel water-soluble α-D-glucan (ASPG-1) with a molecular weight of 2.56 × 10⁶ Da was purified and characterized from A. subcrenata. Its structure was characterized as a repeating unit consisting of α-D-Glcp, (1 → 6)-α-D-Glcp and (1 → 4,6)-α-D-Glcp. ASPG-1 exerted potent immunoregulatory activity by promoting the viability of splenic lymphocytes. Moreover, it enhanced pinocytic capacity, and promoted the secretion of NO and cytokines in RAW264.7 cells. The immunomodulatory mechanism of ASPG-1 involved the activation of the TLR4-MAPK/Akt-NF-κB signaling pathway. ASPG-1 inhibited tumor growth in 4T1 breast cancer mice and its combination with doxorubicin increased antitumor efficacy. The ASPG-1 combination with DOX-treated group (64.8%) showed an improved tumor inhibition rate compared to that of the DOX-treated group (53.3%). The antitumor mechanism of ASPG-1 may involve an enhancement of the immune response of mice to tumors. These results indicated that ASPG-1 could be developed as a potential adjuvant in tumor immunotherapy.

Signal-transducing innate receptors in tumor immunity

The signal‐transducing innate receptors represent classes of pattern recognition receptors (PRRs) that play crucial roles in the first line of the host defense against infections by the recognition of pathogen‐derived molecules. Because of their poorly discriminative nature compared with antigen receptors of the adaptive immune system, they also recognize endogenous molecules and evoke immune responses without infection, resulting in the regulation of tumor immunity. Therefore, PRRs may be promising targets for effective cancer immunotherapy, either by activating or inhibiting them. Here, we summarize our current knowledge of signal‐transducing PRRs in the regulation of tumor immunity.

Harnessing Natural Killer Cells in Cancer Immunotherapy: A Review of Mechanisms and Novel Therapies

Natural killer (NK) cells are lymphocytes that are integral to the body's innate immunity, resulting in a rapid immune response to stressed or infected cells in an antigen-independent manner. The innate immune system plays an important role in the recognition of tumor-derived stress-related factors and is critical to subsequent adaptive immune responses against tumor antigens. The aim of this review is to discuss mechanisms by which tumor cells evade NK cells and to outline strategies that harness NK cells for cancer immunotherapy. We discuss strategies to relieve the exhausted state of NK cells, recent therapies focused on targeting NK-cell-specific activating and inhibitory receptors, the use of cytokines IL-2 and IL-15 to stimulate autologous or allogeneic NK cells, and ongoing trials exploring the use of genetically modified NK cells and chimeric antigen-receptor-modified NK (CAR-NK) cells.

Modifying the Non-muscle Invasive Bladder Cancer Immune Microenvironment for Optimal Therapeutic Response

It is now well-recognized that the tumor microenvironment (TME) is not only a key regulator of cancer progression but also plays a crucial role in cancer treatment responses. Recently, several high-profile publications have demonstrated the importance of particular immune parameters and cell types that dictate responsiveness to immunotherapies. With this increased understanding of TME-mediated therapy, approaches that increase therapeutic efficacy by remodeling the TME are actively being pursued. A classic example of this, in practice by urologists for over 40 years, is the manipulation of the bladder microenvironment for the treatment of non-muscle invasive bladder cancer (NMIBC) by instillation of intravesical bacillus Calmette-Guerin (BCG). The success of BCG treatment is thought to be due to its ability to induce a massive influx of Th1-polarized inflammatory cells, production of Th1 inflammatory cytokines and the generation of tumor-targeted Th1-mediated cytotoxic responses. Whilst BCG immunotherapy is currently the best treatment for NMIBC, ~30% of patients show no response to this treatment. Here we present a review highlighting a variety of promising alternative immunotherapies being developed that remodel the bladder tumor microenvironment. These include (1) the use of oncolytic viruses which selectively replicate within cancer cells whilst also modifying the immunological components of the TME, (2) manipulation of the bladder microbiome to augment the response to BCG or other immunotherapies (3) utilizing Toll-like Receptor agonists as anti-tumor agents due to their potent stimulation of innate and adaptive immunity and (4) the growing recognition that immunotherapeutic strategies that will have the largest impact on patients may require multiple therapeutic approaches combined together. The accumulating knowledge on TME remodeling holds promise for providing an alternative therapy for patients with BCG-unresponsive NMIBC.

P2Y2R-mediated inflammasome activation is involved in tumor progression in breast cancer cells and in radiotherapy-resistant breast cancer

In the tumor microenvironment, extracellular nucleotides are released and accumulate, and can activate the P2Y2 receptor (P2Y2R), which regulates various responses in tumor cells, resulting in tumor progression and metastasis. Moreover, the inflammasome has recently been reported to be associated with tumor progression. However, the role of P2Y2R in inflammasome activation in breast cancer cells is not yet well defined. Therefore, in this study, we investigated the role of P2Y2R in inflammasome-mediated tumor progression in breast cancer using breast cancer cells and radiotherapy-resistant (RT‑R) breast cancer cells. We established RT‑R-breast cancer cells (RT‑R‑MDA‑MB‑231, RT‑R‑MCF‑7, and RT‑R-T47D cells) by repeated irradiation (2 Gy each, 25 times) in a previous study. In this study, we found that the RT‑R breast cancer cells exhibited an increased release of adenosine triphosphate (ATP) and P2Y2R activity. In particular, the RT‑R‑MDA‑MB‑231 cells derived from highly metastatic MDA‑MB‑231 cells, exhibited a markedly increased ATP release, which was potentiated by tumor necrosis factor (TNF)-α. The MDA‑MB‑231 cells exhibited inflammasome activation, as measured by caspase‑1 activity and interleukin (IL)-1β secretion following treatment with TNF‑α and ATP; these effects were enhanced in the RT‑R‑MDA‑MB‑231 cells. However, the increased caspase‑1 activities and IL‑1β secretion levels induced in response to treatment with TNF‑α or ATP were significantly reduced by P2Y2R knockdown or the presence of apyrase in both the MDA‑MB‑231 and RT‑R‑MDA‑MB‑231 cells, suggesting the involvement of ATP-activated P2Y2R in inflammasome activation. In addition, TNF‑α and ATP increased the invasive and colony-forming ability of the MDA‑MB‑231 and RT‑R‑MDA‑MB‑231 cells, and these effects were caspase‑1-dependent. Moreover, matrix metalloproteinase (MMP)-9 activity was modulated by caspase-1, in a P2Y2R-dependent manner in the MDA‑MB‑231 and RT‑R‑MDA‑MB‑231 cells. Finally, nude mice injected with the RT‑R‑MDA‑MB‑231-EV cells (transfected with the empty vector) exhibited increased tumor growth, and higher levels of MMP-9 in their tumors and IL‑1β levels in their serum compared with the mice injected with the RT‑R‑MDA‑MB‑231-P2Y2R shRNA cells (transfected with P2Y2R shRNA). On the whole, the findings of this study suggest that extracellular ATP promotes tumor progression in RT‑R-breast cancer cells and breast cancer cells by modulating invasion and associated molecules through the P2Y2R-inflammasome activation pathway.

Regulation of migration and invasion by Toll-like receptor-9 signaling network in prostate cancer

Toll-like receptors (TLRs) play an important role in tumorigenesis and progress of prostate cancer. However, the function and mechanism of Toll-like receptor-9 (TLR9) in prostate cancer is not totally understood. Here, we found that high expression of TLR9 was associated with a higher probability of lymph node metastasis and poor prognosis. Further in vitro functional study verified that silence of TLR9 inhibited migration and invasion of PC-3 cells, indicating expression of TLR9 involving in the migration and invasion of cancer cells. The data of microarray exhibited silence of TLR9 induced 205 genes with larger than 2-fold changes in expression levels, including 164 genes down-regulated and 41 genes up-regulated. Functional Gene Ontology (GO) processes annotation demonstrated that the top three scores of molecular and cellular functions were regulation of programmed cell death, regulation of locomotion and response to calcium ion. TLR9 signaling network analysis of the migration and invasion related genes identified several genes, like matrix metallopeptidase 2 (MMP2), matrix metallopeptidase 9 (MMP9), chemokine receptor 4 (CXCR4) and interleukin 8 (IL8), formed the core interaction network based on their known biological relationships. A few genes, such as odontogenic ameloblast-associated protein (ODAM), claudin 2 (CLDN2), gap junction protein beta 1 (GJB1) and Rho-associated coiled-coil containing protein kinase 1 pseudogene 1 (ROCK1P1), so far have not been found to interact with the other genes. This study provided the foundation to discover the new molecular mechanism in signaling networks of invasion and metastasis in prostate cancer.

Trial Watch: Toll-like receptor agonists in oncological indications

Toll-like receptors (TLRs) are an evolutionarily conserved group of enzymatically inactive, single membrane-spanning proteins that recognize a wide panel of exogenous and endogenous danger signals. Besides constituting a crucial component of the innate immune response to bacterial and viral pathogens, TLRs appear to play a major role in anticancer immunosurveillance. In line with this notion, several natural and synthetic TLR ligands have been intensively investigated for their ability to boost tumor-targeting immune responses elicited by a variety of immunotherapeutic and chemotherapeutic interventions. Three of these agents are currently approved by the US Food and Drug Administration (FDA) or equivalent regulatory agencies for use in cancer patients: the so-called bacillus Calmette-Guérin, monophosphoryl lipid A, and imiquimod. However, the number of clinical trials testing the therapeutic potential of both FDA-approved and experimental TLR agonists in cancer patients is stably decreasing, suggesting that drug developers and oncologists are refocusing their interest on alternative immunostimulatory agents. Here, we summarize recent findings on the use of TLR agonists in cancer patients and discuss how the clinical evaluation of FDA-approved and experimental TLR ligands has evolved since the publication of our first Trial Watch dealing with this topic.

Antitumor activity of total flavonoids from Tetrastigma hemsleyanum Diels et Gilg is associated with the inhibition of regulatory T cells in mice

Objective

To determine the antitumor activity of Radix tetrastigmae flavonoids and their inhibitory effect on regulatory T cells (Tregs) in mice.

Materials and methods

Total flavonoids were isolated from Radix tetrastigmae, the root of Tetrastigma hemsleyanum Diels et Gilg, and administered to C57BL/6 mice by oral gavage after inoculation with Lewis lung carcinoma (LLC) cells. The effects of total flavonoids on tumor growth in vivo were examined. Flow cytometry was used to study the effects on Tregs, and enzyme-linked immunosorbent assay was used to analyze the changes in the serum levels of transforming growth factor β, prostaglandin E2, and cyclooxygenase 2 after tumor inoculation and flavonoid administration.

Results

Total flavonoids from T. hemsleyanum Diels et Gilg significantly inhibited tumor growth in C57BL/6 mice inoculated with LLCs. These flavonoids dramatically suppressed regulatory T-cell development in tumor-bearing mice. Further studies revealed that total flavonoids significantly decreased the serum levels of transforming growth factor β, prostaglandin E2, and cyclooxygenase 2 in tumor-bearing mice, which may be responsible for the inhibition of Tregs.

Conclusion

The antitumor activity of total flavonoids from T. hemsleyanum Diels et Gilg is associated with the inhibition of Tregs in a mouse tumor model. Total flavonoids from T. hemsleyanum Diels et Gilg may be used as antitumor agents in cancer prevention and treatment.

NOD1, RIP2 and Caspase12 are potentially novel biomarkers for oral squamous cell carcinoma development and progression

Although increasing studies have indicated that Nucleotide-oligomerization domain-containing protein 1 (NOD1) signaling could play an important role in gastrointestinal tumorigenesis, the protein expression and function of NOD1 signaling have not been understood well in oral squamous cell carcinoma (OSCC) progression. The objective of this study is, thus, to examine protein expression of NOD1 signaling immunohistochemically in normal, premalignant and malignant specimens of oral cavity, and to take insights into the association between the protein expression of NOD1 signaling pathway and OSCC precession. In this study immunohistochemical expression of NOD1, Receptor-interacting protein 2 (RIP2), Caspase12, human β Defensin1, 2 and 3 (hBD1, 2, 3) was examined in 15 normal controls, 30 cases of oral leukoplakia (OLK) and 60 cases of OSCC. The immunostaining score was assessed by 2 pathologists, respectively. We found that the expression of NOD1, RIP2, Caspase12, hBD1, 2, and 3 decreased along with the progression of OSCC. NOD1 expression was correlated significantly to tumor differentiation, lymph node metastasis, and tumor size. Our results also showed the correlation of hBD2, 3 to lymph node metastasis of OSCC. These results suggest that the dysfunction of NOD1 signaling pathways could be associated with OSCC development and progression. NOD1, RIP2 and Caspase12 could be used as potentially novel biomarkers for oral carcinogenesis.

The use of anchored agonists of phagocytic receptors for cancer immunotherapy: B16-F10 murine melanoma model

The application of the phagocytic receptor agonists in cancer immunotherapy was studied. Agonists (laminarin, molecules with terminal mannose, N-Formyl-methioninyl-leucyl-phenylalanine) were firmly anchored to the tumor cell surface. When particular agonists of phagocytic receptors were used together with LPS (Toll-like receptor agonist), high synergy causing tumour shrinkage and a temporary or permanent disappearance was observed. Methods of anchoring phagocytic receptor agonists (charge interactions, anchoring based on hydrophobic chains, covalent bonds) and various regimes of phagocytic agonist/LPS mixture applications were tested to achieve maximum therapeutic effect. Combinations of mannan/LPS and f-MLF/LPS (hydrophobic anchors) in appropriate (pulse) regimes resulted in an 80% and 60% recovery for mice, respectively. We propose that substantial synergy between agonists of phagocytic and Toll-like receptors (TLR) is based on two events. The TLR ligand induces early and massive inflammatory infiltration of tumors. The effect of this cell infiltrate is directed towards tumor cells, bearing agonists of phagocytic receptors on their surface. The result of these processes was effective killing of tumor cells. This novel approach represents exploitation of innate immunity mechanisms for treating cancer.

Trial Watch: Toll-like receptor agonists for cancer therapy

Toll-like receptors (TLRs) have long been known for their ability to initiate innate immune responses upon exposure to conserved microbial components such as lipopolysaccharide (LPS) and double-stranded RNA. More recently, this family of pattern recognition receptors has been attributed a critical role in the elicitation of anticancer immune responses, raising interest in the development of immunochemotherapeutic regimens based on natural or synthetic TLR agonists. In spite of such an intense wave of preclinical and clinical investigation, only three TLR agonists are currently licensed by FDA for use in cancer patients: bacillus Calmette–Guérin (BCG), an attenuated strain of Mycobacterium bovis that operates as a mixed TLR2/TLR4 agonist; monophosphoryl lipid A (MPL), a derivative of Salmonella minnesota that functions as a potent agonist of TLR4; and imiquimod, a synthetic imidazoquinoline that activates TLR7. One year ago, in the August and September issues of OncoImmunology, we described the main biological features of TLRs and discussed the progress of clinical studies evaluating the safety and therapeutic potential of TLR agonists in cancer patients. Here, we summarize the latest developments in this exciting area of research, focusing on preclinical studies that have been published during the last 13 mo and clinical trials launched in the same period to investigate the antineoplastic activity of TLR agonists.

Combined blockade of TIM-3 and TIM-4 augments cancer vaccine efficacy against established melanomas

Cancer vaccines have been developed to instruct the endogenous immune responses to autologous tumors and to generate durable clinical responses. However, the therapeutic benefits of cancer vaccines remain insufficient due to the multiple immunosuppressive signals delivered by tumors. Thus, to improve the clinical efficacy of cancer immunotherapy, it is important to develop new modalities to overcome immunosuppressive tumor microenvironments and elicit effective antitumor immune responses. In this study, we show that novel monoclonal antibodies (mAbs) specifically targeting either T cell immunoglobulin mucin protein-3 (TIM-3) or T cell immunoglobulin mucin protein-4 (TIM-4) enhance the therapeutic effects of vaccination against established B16 murine melanomas. This is true for vaccination with irradiated B16 melanoma cells engineered to express the flt3 ligand gene (FVAX). More importantly, combining anti-TIM-3 and anti-TIM-4 mAbs markedly increased vaccine-induced antitumor responses against established B16 melanoma. TIM-3 blockade mainly stimulated antitumor effector activities via natural killer cell-dependent mechanisms, while CD8(+) T cells served as the main effectors induced by anti-TIM-4 mAb. Our findings reveal that therapeutic manipulation of TIM-3 and TIM-4 may provide a novel strategy for improving the clinical efficacy of cancer immunotherapy.

Expression of Toll-like receptor-9 is associated with poor progression-free survival in prostate cancer

Toll-like receptor-9 (TLR9) is a member of the innate immune system and recognizes bacterial and vertebrate DNA in cells. In addition to being expressed in cells of the immune system, it is widely expressed in various types of human cancer, including prostate cancer. We have previously demonstrated that synthetic TLR9 ligands induce invasion in TLR9-expressing prostate cancer cells in vitro. However, the role of TLR9 in the pathophysiology of prostate cancer is unclear. The expression of TLR9 in radical prostatectomy samples (n=186) was studied using immunohistochemistry. TLR9 staining scores were compared with tumor stage, Gleason score and prostate-specific antigen (PSA) concentration prior to treatment and progression-free survival. Results revealed that 124 (66.7%) of the tumors were strongly positive, 59 (31.7%) were weakly positive and 3 (1.6%) were negative, for cytoplasmic TLR9 immunostaining in cancer cells. There was no significant association between cytoplasmic TLR9 expression and distributions of pT-class, prostatectomy sample margin status, Gleason score and preoperative PSA value. Prostate cancer-specific progression-free survival was significantly longer for patients whose tumors were graded as negative for cytoplasmic TLR9 expression, as compared with patients whose tumors were strongly immunopositive for cytoplasmic TLR9 (P=0.009). In the Cox regression analysis, high TLR9 expression was an independent marker of poor prognosis in prostate cancer. Expression of TLR9 is associated with poor progression-free survival in prostate cancer patients who were treated by radical prostatectomy with curative intent.

MFG-E8 regulates the immunogenic potential of dendritic cells primed with necrotic cell-mediated inflammatory signals

Dendritic cells (DC) manipulate tissue homeostasis by recognizing dying cells and controlling immune functions. However, the precise mechanisms by which DC recognize different types of dying cells and devise distinct immunologic consequences remain largely obscure. Herein, we demonstrate that Milk-fat globule-EGF VIII (MFG-E8) is a critical mediator controlling DC immunogenicity in inflammatory microenvironments. MFG-E8 restrains DC-mediated uptake and recognition of necrotic cells. The MFG-E8-mediated suppression of necrotic cell uptake by DC resulted in the decreased proinflammatory cytokines production and activated signal components such as STAT3 and A20, which are critical to maintain tolerogenic properties of DC. Furthermore, the DC-derived MFG-E8 negatively regulates the cross-priming and effector functions of antigen-specific T cells upon recognition of necrotic cells. MFG-E8 deficiency enhances an ability of necrotic cell-primed DC to stimulate antitumor immune responses against established tumors. Our findings define what we believe to a novel mechanism whereby MFG-E8 regulates the immunogenicity of DC by modulating the modes of recognition of dying cells. Manipulating MFG-E8 levels in DC may serve as a useful strategy for controlling inflammatory microenvironments caused by various pathological conditions including cancer and autoimmunity.