A synthetic NOD2 agonist, muramyl dipeptide (MDP)-Lys (L18) and IFN-β synergistically induce dendritic cell maturation with augmented IL-12 production and suppress melanoma growth

NOD2 reduces the chemoresistance of melanoma by inhibiting the TYMS/PLK1 signaling axis

Nucleotide-binding oligomerization domain 2 (NOD2) is an immune sensor crucial for eliciting the innate immune responses. Nevertheless, discrepancies exist regarding the effect of NOD2 on different types of cancer. This study aimed to investigate these function of NOD2 in melanoma and its underlying mechanisms. We have validated the tumor suppressor effect of NOD2 in melanoma. NOD2 inhibited the proliferation of melanoma cells, hindering their migration and invasion while promoting the onset of apoptosis. Our study showed that NOD2 expression is closely related to pyrimidine and folate metabolism. NOD2 inhibits thymidylate synthase (TYMS) expression by promoting K48-type ubiquitination modification of TYMS, thereby decreasing the resistance of melanoma cells to 5-fluorouracil (5-FU) and capecitabine (CAP). TYMS was identified to form a complex with Polo-like Kinase 1 (PLK1) and activate the PLK1 signaling pathway. Furthermore, we revealed that the combination of the PLK1 inhibitor volasertib (BI6727) with 5-FU or CAP had a synergistic effect repressing the proliferation, migration, and autophagy of melanoma cells. Overall, our research highlights the protective role of NOD2 in melanoma and suggests that targeting NOD2 and the TYMS/PLK1 signaling axis is a high-profile therapy that could be a prospect for melanoma treatment.

"Just right" combinations of adjuvants with nanoscale carriers activate aged dendritic cells without overt inflammation

BACKGROUND

The loss in age-related immunological markers, known as immunosenescence, is caused by a combination of factors, one of which is inflammaging. Inflammaging is associated with the continuous basal generation of proinflammatory cytokines. Studies have demonstrated that inflammaging reduces the effectiveness of vaccines. Strategies aimed at modifying baseline inflammation are being developed to improve vaccination responses in older adults. Dendritic cells have attracted attention as an age-specific target because of their significance in immunization as antigen presenting cells that stimulate T lymphocytes.

RESULTS

In this study, bone marrow derived dendritic cells (BMDCs) were generated from aged mice and used to investigate the effects of combinations of adjuvants, including Toll-like receptor, NOD2, and STING agonists with polyanhydride nanoparticles and pentablock copolymer micelles under in vitro conditions. Cellular stimulation was characterized via expression of costimulatory molecules, T cell-activating cytokines, proinflammatory cytokines, and chemokines. Our results indicate that multiple TLR agonists substantially increase costimulatory molecule expression and cytokines associated with T cell activation and inflammation in culture. In contrast, NOD2 and STING agonists had only a moderate effect on BMDC activation, while nanoparticles and micelles had no effect by themselves. However, when nanoparticles and micelles were combined with a TLR9 agonist, a reduction in the production of proinflammatory cytokines was observed while maintaining increased production of T cell activating cytokines and enhancing cell surface marker expression. Additionally, combining nanoparticles and micelles with a STING agonist resulted in a synergistic impact on the upregulation of costimulatory molecules and an increase in cytokine secretion from BMDCs linked with T cell activation without excessive secretion of proinflammatory cytokines.

CONCLUSIONS

These studies provide new insights into rational adjuvant selection for vaccines for older adults. Combining appropriate adjuvants with nanoparticles and micelles may lead to balanced immune activation characterized by low inflammation, setting the stage for designing next generation vaccines that can induce mucosal immunity in older adults.

The role of tumor-associated macrophages and soluble mediators in pulmonary metastatic melanoma

Skin malignant melanoma is a highly aggressive skin tumor, which is also a major cause of skin cancer-related mortality. It can spread from a relatively small primary tumor and metastasize to multiple locations, including lymph nodes, lungs, liver, bone, and brain. What’s more metastatic melanoma is the main cause of its high mortality. Among all organs, the lung is one of the most common distant metastatic sites of melanoma, and the mortality rate of melanoma lung metastasis is also very high. Elucidating the mechanisms involved in the pulmonary metastasis of cutaneous melanoma will not only help to provide possible explanations for its etiology and progression but may also help to provide potential new therapeutic targets for its treatment. Increasing evidence suggests that tumor-associated macrophages (TAMs) play an important regulatory role in the migration and metastasis of various malignant tumors. Tumor-targeted therapy, targeting tumor-associated macrophages is thus attracting attention, particularly for advanced tumors and metastatic tumors. However, the relevant role of tumor-associated macrophages in cutaneous melanoma lung metastasis is still unclear. This review will present an overview of the origin, classification, polarization, recruitment, regulation and targeting treatment of tumor-associated macrophages, as well as the soluble mediators involved in these processes and a summary of their possible role in lung metastasis from cutaneous malignant melanoma. This review particularly aims to provide insight into mechanisms and potential therapeutic targets to readers, interested in pulmonary metastasis melanoma.

Construction and validation of a novel pyroptosis-related signature to predict prognosis in patients with cutaneous melanoma

Skin cutaneous melanoma (SKCM) is one of the most malignant skin cancers and remains a health concern worldwide. Pyroptosis is a newly recognized form of programmed cell death and plays a vital role in cancer progression. We aim to construct a prognostic model for SKCM patients based on pyroptosis-related genes (PRGs). SKCM patients from The Cancer Genome Atlas (TCGA) were divided into training and validation cohorts. We used GSE65904 downloaded from GEO database as an external validation cohort. We performed Cox regression and the least absolute shrinkage and selection operator (LASSO) regression to identify prognostic genes and built a risk score. Patients were divided into high- and low-risk groups based on the risk score. Differently expressed genes (DEGs), immune cell infiltration and immune-related pathways activation were compared between the two groups. We established a model containing 4 PRGs, i.e., GSDMA, GSDMC, AIM2 and NOD2. The overall survival (OS) time was significantly different between the 2 groups. The risk score was an independent predictor for prognosis in both the uni- and multi-variable Cox regressions. Gene ontology (GO) and Kyoto Encylopedia of Genes and Genomes (KEGG) analyses showed that DEGs were enriched in immune-related pathways. Most types of immune cells were highly expressed in the low risk group. All immune pathways were significantly up-regulated in the low-risk group. In addition, low-risk patients had a better response to immune checkpoint inhibitors. Our novel pyroptosis-related gene signature could predict the prognosis of SKCM patients and their response to immune checkpoint inhibitors.

Strategies for Using Muramyl Peptides - Modulators of Innate Immunity of Bacterial Origin - in Medicine

The spread of infectious diseases is rampant. The emergence of new infections, the irrational use of antibiotics in medicine and their widespread use in agriculture contribute to the emergence of microorganisms that are resistant to antimicrobial drugs. By 2050, mortality from antibiotic-resistant strains of bacteria is projected to increase up to 10 million people per year, which will exceed mortality from cancer. Mutations in bacteria and viruses are occurring faster than new drugs and vaccines are being introduced to the market. In search of effective protection against infections, new strategies and approaches are being developed, one of which is the use of innate immunity activators in combination with etiotropic chemotherapy drugs. Muramyl peptides, which are part of peptidoglycan of cell walls of all known bacteria, regularly formed in the body during the breakdown of microflora and considered to be natural regulators of immunity. Their interaction with intracellular receptors launches a sequence of processes that ultimately leads to the increased expression of genes of MHC molecules, pro-inflammatory mediators, cytokines and their soluble and membrane-associated receptors. As a result, all subpopulations of immunocompetent cells are activated: macrophages and dendritic cells, neutrophils, T-, B- lymphocytes and natural killer cells for an adequate response to foreign or transformed antigens, manifested both in the regulation of the inflammatory response and in providing immunological tolerance. Muramyl peptides take part in the process of hematopoiesis, stimulating production of colony-stimulating factors, which is the basis for their use in the treatment of oncological diseases. In this review we highlight clinical trials of drugs based on muramyl peptides, as well as clinical efficacy of drugs mifamurtide, lycopid, liasten and polimuramil. Such a multifactorial effect of muramyl peptides and a well-known mechanism of activity make them promising drugs in the treatment and preventing of infectious, allergic and oncological diseases, and in the composition of vaccines.

Translation of peptidoglycan metabolites into immunotherapeutics

The discovery of defined peptidoglycan metabolites that activate host immunity and their specific receptors has revealed fundamental insights into host-microbe recognition and afforded new opportunities for therapeutic development against infection and cancer. In this review, we summarise the discovery of two key peptidoglycan metabolites, γ-d-glutamyl-meso-diaminopimelic acid (iE-DAP) and muramyl dipeptide and their respective receptors, Nod1 and Nod2, and review progress towards translating these findings into therapeutic agents. Notably, synthetic derivatives of peptidoglycan metabolites have already yielded approved drugs for chemotherapy-induced leukopenia and paediatric osteosarcoma; however, the broad effects of peptidoglycan metabolites on host immunity suggest additional translational opportunities for new therapeutics towards other cancers, microbial infections and inflammatory diseases.

Molecular determinants as therapeutic targets in cancer chemotherapy: An update

It is well known that cancer cells are heterogeneous in nature and very distinct from their normal counterparts. Commonly these cancer cells possess different and complementary metabolic profile, microenvironment and adopting behaviors to generate more ATPs to fulfill the requirement of high energy that is further utilized in the production of proteins and other essentials required for cell survival, growth, and proliferation. These differences create many challenges in cancer treatments. On the contrary, such situations of metabolic differences between cancer and normal cells may be expected a promising strategy for treatment purpose. In this article, we focus on the molecular determinants of oncogene-specific sub-organelles such as potential metabolites of mitochondria (reactive oxygen species, apoptotic proteins, cytochrome c, caspase 9, caspase 3, etc.), endoplasmic reticulum (unfolded protein response, PKR-like ER kinase, C/EBP homologous protein, etc.), nucleus (nucleolar phosphoprotein, nuclear pore complex, nuclear localization signal), lysosome (microenvironment, etc.) and plasma membrane phospholipids, etc. that might be exploited for the targeted delivery of anti-cancer drugs for therapeutic benefits. This review will help to understand the various targets of subcellular organelles at molecular levels. In the future, this molecular level understanding may be combined with the genomic profile of cancer for the development of the molecularly guided or personalized therapeutics for complete eradication of cancer.

Harnessing the untapped potential of nucleotide-binding oligomerization domain ligands for cancer immunotherapy

In the last decade, cancer immunotherapy has emerged as an effective alternative to traditional therapies such as chemotherapy and radiation. In contrast to the latter, cancer immunotherapy has the potential to distinguish between cancer and healthy cells, and thus to avoid severe and intolerable side‐effects, since the cancer cells are effectively eliminated by stimulated immune cells. The cytosolic nucleotide‐binding oligomerization domains 1 and 2 receptors (NOD1 and NOD2) are important components of the innate immune system and constitute interesting targets in terms of strengthening the immune response against cancer cells. Many NOD ligands have been synthesized, in particular NOD2 agonists that exhibit favorable immunostimulatory and anticancer activity. Among them, mifamurtide has already been approved in Europe by the European Medicine Agency for treating patients with osteosarcoma in combination with chemotherapy after complete surgical removal of the primary tumor. This review is focused on NOD receptors as promising targets in cancer immunotherapy as well as summarizing current knowledge of the various NOD ligands exhibiting antitumor and even antimetastatic activity in vitro and in vivo.

Muramyl Dipeptide, a Shared Structural Motif of Peptidoglycans, Is a Novel Inducer of Bone Formation through Induction of Runx2

Peptidoglycan fragments released from gut microbiota can be delivered to the bone marrow and affect bone metabolism. We investigated the regulation of bone metabolism by muramyl dipeptide (MDP), which is a shared structural unit of peptidoglycans. Increased bone and mineral density by enhanced bone formation were observed in mice administered with MDP. Remarkably, pretreatment or posttreatment with MDP alleviated bone loss in RANKL-induced osteoporosis mouse models. MDP directly augmented osteoblast differentiation and bone-forming gene expression by Runx2 activation. Despite no direct effect, MDP indirectly attenuated osteoclast differentiation through downregulation of the RANKL/osteoprotegerin (OPG) ratio. MDP increased the expression of the MDP receptor, Nod2, and MDP-induced bone formation and osteoblast activation did not occur during Nod2 deficiency. Other Nod2 ligands also increased bone formation through the induction of Runx2, as MDP did. In conclusion, we suggest that MDP is a novel inducer of bone formation that could potentially be a new therapeutic molecule to protect against osteoporosis. © 2017 American Society for Bone and Mineral Research.

Tumor-associated macrophages in skin: How to treat their heterogeneity and plasticity

Immunosuppressive tumor-associated macrophages (TAMs) promote an immunosuppressive environment in the tumor-bearing host, together with regulatory T cells (Tregs). TAMs compose cancer stroma in skin cancers including melanomas and non-melanomas. The majority of tumor-associated macrophages (TAMs) are alternatively activated M2 macrophages that favor tumor development, and they comprise one of the main populations of inflammatory cells in skin cancers. On the other hand, TAMs could be modulated into M1-type macrophages that suppress tumor growth by stimulating and recruiting Th1 and effector cells in the tumor sites. Therefore, TAMs are a target for immunotherapy in various cancers. In this review, we discuss the definition and suppressive mechanisms of TAMs, as well as their biological activities in tumor-bearing hosts to assess potential therapeutic strategies.

Interferon gamma boosts the nucleotide oligomerization domain 2-mediated signaling pathway in human dendritic cells in an X-linked inhibitor of apoptosis protein and mammalian target of rapamycin-dependent manner

The cytoplasmic nucleotide oligomerization domain 2 (NOD2) receptor recognizes the bacterial cell wall component muramyl dipeptide (MDP). NOD2 ligation initiates the nuclear factor kappa B and the mitogen-activated protein kinase cascades. However, administering MDP alone is insufficient to elicit strong cytokine responses in various immune cells, including dendritic cells (DCs). Because the simultaneous presence of various microbial products and cytokines in inflamed tissues modulates DC function, we initiated this study to examine how interferon gamma (IFNγ), a central modulator of inflammation, affects the NOD2-mediated signaling pathway in human conventional DCs (cDCs). Synergistic stimulation of DCs with MDP and IFNγ increased the expression of CD40, CD80, CD83, CD86, and human leukocyte antigen DQ proteins and significantly elevated the production of pro-inflammatory cytokines IL-1β, IL-6, IL-12, and tumour necrosis factor (TNF), as well as anti-inflammatory cytokine IL-10. Furthermore, the simultaneous presence of MDP and IFNγ was necessary to decrease IkBα protein levels. By investigating various mechanisms implicated in MDP- and IFNγ-mediated signaling pathways, we revealed that the increased production of pro-inflammatory cytokines is highly dependent on the X-linked inhibitor of apoptosis protein (XIAP) but not on cellular IAP1 and IAP2. We also found that the NOD2 signaling pathway is regulated by the mammalian target of rapamycin (mTOR) but is not affected by phosphatidylinositol-3 kinase or signal transducer and activator of transcription 1 inhibition. Our results demonstrate, for the first time, that IFNγ positively affects NOD2-mediated signaling in human cDCs, in a manner considerably dependent on XIAP and partially dependent on mTOR.

Immunomodulatory effect of peritumorally administered interferon-beta on melanoma through tumor-associated macrophages

An imbalance of immunosuppressive cells and cytotoxic cells plays an important role in the tumor-bearing host. Together with regulatory T cells (Tregs), tumor-associated macrophages (TAMs) play roles in maintaining the tumor microenvironment. Since interferon beta (IFN-β) has been clinically used for the treatment of malignant melanoma, we investigated the immunomodulatory effect of IFN-β during melanoma growth to elucidate the effects of IFN-β on the tumor microenvironment by using the B16F10 melanoma model. Peritumorally administered IFN-β significantly decreased the mRNA expression and production of Th2-related chemokines, which suppressed the recruitment of Tregs in B16F10 melanoma. Since the administration of IFN-β augments the expression of PD-1 on TILs, the co-administration of anti-PD-1 Ab augmented the therapeutic effect of IFN-β for the treatment of B16F10 melanoma. Moreover, in parallel with the mouse model, in the human system, IFN-β decreased the production of Th2-related chemokines and augmented the production of Th1-related chemokines from monocyte-derived M2 macrophages. Since these immunomodulatory effects of IFN-β on macrophages were also observed in the lesional skin of human in-transit melanoma, our present data suggest one of the possible immunomodulatory effects of IFN-β and support the possibility of IFN-β in combination with anti-PD-1 Ab for the treatment of melanoma.

NOD-Like Receptors: Master Regulators of Inflammation and Cancer

Cytosolic NOD-like receptors (NLRs) have been associated with human diseases including infections, cancer, and autoimmune and inflammatory disorders. These innate immune pattern recognition molecules are essential for controlling inflammatory mechanisms through induction of cytokines, chemokines, and anti-microbial genes. Upon activation, some NLRs form multi-protein complexes called inflammasomes, while others orchestrate caspase-independent nuclear factor kappa B (NF-κB) and mitogen activated protein kinase (MAPK) signaling. Moreover, NLRs and their downstream signaling components engage in an intricate crosstalk with cell death and autophagy pathways, both critical processes for cancer development. Recently, increasing evidence has extended the concept that chronic inflammation caused by abberant NLR signaling is a powerful driver of carcinogenesis, where it abets genetic mutations, tumor growth, and progression. In this review, we explore the rapidly expanding area of research regarding the expression and functions of NLRs in different types of cancers. Furthermore, we particularly focus on how maintaining tissue homeostasis and regulating tissue repair may provide a logical platform for understanding the liaisons between the NLR-driven inflammatory responses and cancer. Finally, we outline novel therapeutic approaches that target NLR signaling and speculate how these could be developed as potential pharmaceutical alternatives for cancer treatment.

Combined p19Arf and interferon-beta gene transfer enhances cell death of B16 melanoma in vitro and in vivo

Approximately 90% of melanomas retain wild-type p53, a characteristic that may help shape the development of novel treatment strategies. Here, we employed an adenoviral vector where transgene expression is controlled by p53 to deliver the p19 alternate reading frame (Arf) and interferon-β (IFNβ) complementary DNAs in the B16 mouse model of melanoma. In vitro, cell death was enhanced by combined gene transfer (63.82±15.30% sub-G0 cells); yet introduction of a single gene resulted in significantly fewer hypoploid cells (37.73±7.3% or 36.96±11.58%, p19Arf or IFNβ, respectively, P<0.05). Annexin V staining and caspase-3 cleavage indicate a cell death mechanism consistent with apoptosis. Using reverse transcriptase quantitative PCR, we show that key transcriptional targets of p53 were upregulated in the presence of p19Arf, although treatment with IFNβ did not alter expression of the genes studied. In situ gene therapy revealed significant inhibition of subcutaneous tumors by IFNβ (571±25 mm3) or the combination of p19Arf and IFNβ (489±124 mm3) as compared with the LacZ control (1875±33 mm3, P<0.001), whereas p19Arf yielded an intermediate result (1053±169 mm3, P<0.01 vs control). However, only the combination was associated with increased cell death and prolonged survival (P<0.01). As shown here, the combined transfer of p19Arf and IFNβ using p53-responsive vectors enhanced cell death both in vitro and in vivo.

Cutaneous squamous cell carcinoma developing from recessive dystrophic epidermolysis bullosa: a case report and an immunohistochemical study

We describe a 49-year-old Japanese woman with cutaneous squamous cell carcinoma (SCC) developing from recessive dystrophic epidermolysis bullosa (RDEB). Interestingly, immunohistochemical staining revealed dense infiltration of CD163⁺ M2 macrophages and numerous Foxp3⁺ regulatory T cells (Tregs) around the tumor. Since the contribution of immunosuppressive factors (e.g. TGFβ) to the carcinogenesis of SCC from RDEB was recently reported, our present findings suggest one of the possible contributions of immunosuppressive cells, such as CD163⁺ M2 macrophages and Tregs, to the carcinogenesis of SCC from RDEB.