Targeting iNOS to increase efficacy of immunotherapies

Pt-Te-Nanorod-Based Photothermal Chemokine Immunotherapy for All Stages of Cancer via Adaptive and Innate Immunity

The chemokine (C-X-C) motif ligand 9 (CXCL9) is one of the lymphocyte-traffic-involved chemokines. Despite the immunotherapeutic potential of CXCL9 for recruiting effector T cells (cluster of differentiation 4+ (CD4+) and CD8+ T cells) and natural killer cells (NK cells) around the tumors, practical applications of CXCL9 have been limited because of its immune toxicity and lack of stability in vivo. To overcome these limitations, we designed and synthesized Pt-Te nanorods (PtTeNRs), which exhibited excellent photothermal conversion efficiency with stable CXCL9 payload characteristics under the physiological conditions of in vivo environments. We developed a CXCL9-based immunotherapy strategy by utilizing the unique physicochemical properties of developed PtTeNRs. The investigation revealed that the PtTeNR-loaded CXCL9 was effectively accumulated in the tumor, subsequently released in a sustained manner, and successfully recruited effector T cells for immunotherapy of the designated tumor tissue. In addition, a synergistic effect was observed between the photothermal (PT) therapy and antiprogrammed cell death protein 1 (aPD-1) antibody. In this study, we demonstrated that PtTeNR-based CXCL9, PT, and aPD-1 antibody trimodal therapy delivers an outstanding tumor suppression effect in all stages of cancer, including phases 1-4 and tumor recurrence.

The transcriptomic expression pattern of immune checkpoints shows heterogeneity between and within cancer types

Transcriptomic expression profiles of immune checkpoint markers are of interest in order to decipher the mechanisms of immunotherapy response and resistance. Overall, 514 patients with various solid tumors were retrospectively analyzed in this study. The RNA expression levels of tumor checkpoint markers (ADORA2A, BTLA, CD276, CTLA4, IDO1, IDO2, LAG3, NOS2, PD-1, PD-L1, PD-L2, PVR, TIGIT, TIM3, VISTA, and VTCN) were ranked from 0-100 percentile based on a reference population. The expression of each checkpoint was correlated with cancer type, microsatellite instability (MSI), tumor mutational burden (TMB), and programmed death-ligand 1 (PD-L1) by immunohistochemistry (IHC). The cohort included 30 different tumor types, with colorectal cancer being the most common (27%). When RNA percentile rank values were categorized as "Low" (0-24), "Intermediate" (25-74), and "High" (75-100), each patient had a distinctive portfolio of the categorical expression of 16 checkpoint markers. Association between some checkpoint markers and cancer types were observed; NOS2 showed significantly higher expression in colorectal and stomach cancer (P < 0.001). Principal component analysis demonstrated no clear association between combined RNA expression patterns of 16 checkpoint markers and cancer types, TMB, MSI or PD-L1 IHC. Immune checkpoint RNA expression varies from patient to patient, both within and between tumor types, though colorectal and stomach cancer showed the highest levels of NOS2, a mediator of inflammation and immunosuppression. There were no specific combined expression patterns correlated with MSI, TMB or PD-L1 IHC. Next generation immunotherapy trials may benefit from individual analysis of patient tumors as selection criteria for specific immunomodulatory approaches.

IL-23 stabilizes an effector Treg cell program in the tumor microenvironment

Interleukin-23 (IL-23) is a proinflammatory cytokine mainly produced by myeloid cells that promotes tumor growth in various preclinical cancer models and correlates with adverse outcomes. However, as to how IL-23 fuels tumor growth is unclear. Here, we found tumor-associated macrophages to be the main source of IL-23 in mouse and human tumor microenvironments. Among IL-23-sensing cells, we identified a subset of tumor-infiltrating regulatory T (Treg) cells that display a highly suppressive phenotype across mouse and human tumors. The use of three preclinical models of solid cancer in combination with genetic ablation of Il23r in Treg cells revealed that they are responsible for the tumor-promoting effect of IL-23. Mechanistically, we found that IL-23 sensing represents a crucial signal driving the maintenance and stabilization of effector Treg cells involving the transcription factor Foxp3. Our data support that targeting the IL-23/IL-23R axis in cancer may represent a means of eliciting antitumor immunity.

High iNOS and IL-1β immunoreactivity are features of colitis-associated colorectal cancer tumors, but fail to predict 5-year survival

Background

Inflammatory bowel disease (IBD; mainly ulcerative colitis and Crohn's disease) is associated with the development of colorectal cancer (CRC) referred to as colitis-associated colorectal cancer (CAC). In inflammatory flares of IBD, the production of luminal nitric oxide (NO) increases due to the increased inducible nitric oxide synthase (iNOS) activity in inflamed tissue. It is believed that iNOS parallels pro-inflammatory interleukin-1β (IL-1β). How these biomarkers relate to CAC pathogenesis or survival is unknown.

Aim

The primary aim of this study was to investigate iNOS and IL-1β immunoreactivity in CAC tumors in comparison with CRC and normal colonic mucosa, and the secondary aim was to determine if immunoreactivity correlates with 5-year survival of CAC.

Methods

Immunohistochemistry was performed on tissue sections as follows: CAC (n = 59); sporadic CRC (sCRC) (n = 12); colonic mucosa >2 cm outside sCRC margin (normal mucosa) (n = 22); paracancerous IBD (pIBD) (n = 12). The expression of iNOS and IL-1β was quantified separately for epithelium and stroma. Data were evaluated using the Mann-Whitney U-test and the log-rank test for 5-year Kaplan-Meier survival curves. Results were compared with online mRNA databases.

Results

Immunoreactivity occurred predominantly in epithelial cells and to lesser extent in stroma. Compared with normal mucosa, immunoreactivity for iNOS (P < 0.01) and IL-1β (P < 0.005) was higher in CAC epithelium. In CAC stroma, iNOS immunoreactivity was lower than normal mucosa (P < 0.001), whereas IL-1β was higher (P < 0.05). Immunoreactivity differences of iNOS or IL-1β among CAC patients failed to correlate with 5-year survival. These findings were supported by online mRNA databases.

Conclusion

Consistent with high NO production in IBD, there is more iNOS in CAC epithelium, albeit not in stroma. This immunoreactivity difference exists for IL-1β in both epithelium and stroma. The intervention of arginine or iNOS activity for CAC chemotherapy is not straightforward.

A metabolic perspective on nitric oxide function in melanoma

Nitric oxide (NO) generated from nitric oxide synthase (NOS) exerts a dichotomous effect in melanoma, suppressing or promoting tumor progression. This dichotomy is thought to depend on the intracellular NO concentration and the cell type in which it is generated. Due to its central role in the metabolism of multiple critical constituents involved in signaling and stress, it is crucial to explore NO's contribution to the metabolic dysfunction of melanoma. This review will discuss many known metabolites linked to NO production in melanoma. We discuss the synthesis of these metabolites, their role in biochemical pathways, and how they alter the biological processes observed in the melanoma tumor microenvironment. The metabolic pathways altered by NO and the corresponding metabolites reinforce its dual role in melanoma and support investigating this effect for potential avenues of therapeutic intervention.

Spatial analysis of NOS2 and COX2 interaction with T-effector cells reveals immunosuppressive landscapes associated with poor outcome in ER- breast cancer patients

Multiple immunosuppressive mechanisms exist in the tumor microenvironment that drive poor outcomes and decrease treatment efficacy. The co-expression of NOS2 and COX2 is a strong predictor of poor prognosis in ER- breast cancer and other malignancies. Together, they generate pro-oncogenic signals that drive metastasis, drug resistance, cancer stemness, and immune suppression. Using an ER- breast cancer patient cohort, we found that the spatial expression patterns of NOS2 and COX2 with CD3+CD8+PD1- T effector (Teff) cells formed a tumor immune landscape that correlated with poor outcome. NOS2 was primarily associated with the tumor-immune interface, whereas COX2 was associated with immune desert regions of the tumor lacking Teff cells. A higher ratio of NOS2 or COX2 to Teff was highly correlated with poor outcomes. Spatial analysis revealed that regional clustering of NOS2 and COX2 was associated with stromal-restricted Teff, while only COX2 was predominant in immune deserts. Examination of other immunosuppressive elements, such as PDL1/PD1, Treg, B7H4, and IDO1, revealed that PDL1/PD1, Treg, and IDO1 were primarily associated with restricted Teff, whereas B7H4 and COX2 were found in tumor immune deserts. Regardless of the survival outcome, other leukocytes, such as CD4 T cells and macrophages, were primarily in stromal lymphoid aggregates. Finally, in a 4T1 model, COX2 inhibition led to a massive cell infiltration, thus validating the hypothesis that COX2 is an essential component of the Teff exclusion process and, thus, tumor evasion. Our study indicates that NOS2/COX2 expression plays a central role in tumor immunosuppression. Our findings indicate that new strategies combining clinically available NOS2/COX2 inhibitors with various forms of immune therapy may open a new avenue for the treatment of aggressive ER-breast cancers.

Targeting TREM1 augments antitumor T cell immunity by inhibiting myeloid-derived suppressor cells and restraining anti-PD-1 resistance

The triggering receptor expressed on myeloid cell 1 (TREM1) plays a critical role in development of chronic inflammatory disorders and the inflamed tumor microenvironment (TME) associated with most solid tumors. We examined whether loss of TREM1 signaling can abrogate the immunosuppressive TME and enhance cancer immunity. To investigate the therapeutic potential of TREM1 in cancer, we used mice deficient in Trem1 and developed a novel small molecule TREM1 inhibitor, VJDT. We demonstrated that genetic or pharmacological TREM1 silencing significantly delayed tumor growth in murine melanoma (B16F10) and fibrosarcoma (MCA205) models. Single-cell RNA-Seq combined with functional assays during TREM1 deficiency revealed decreased immunosuppressive capacity of myeloid-derived suppressor cells (MDSCs) accompanied by expansion in cytotoxic CD8+ T cells and increased PD-1 expression. Furthermore, TREM1 inhibition enhanced the antitumorigenic effect of anti-PD-1 treatment, in part, by limiting MDSC frequency and abrogating T cell exhaustion. In patient-derived melanoma xenograft tumors, treatment with VJDT downregulated key oncogenic signaling pathways involved in cell proliferation, migration, and survival. Our work highlights the role of TREM1 in cancer progression, both intrinsically expressed in cancer cells and extrinsically in the TME. Thus, targeting TREM1 to modify an immunosuppressive TME and improve efficacy of immune checkpoint therapy represents what we believe to be a promising therapeutic approach to cancer.

Crosstalk between arginine, glutamine, and the branched chain amino acid metabolism in the tumor microenvironment

Arginine, glutamine, and the branched chain amino acids (BCAAs) are a focus of increased interest in the field of oncology due to their importance in the metabolic reprogramming of cancer cells. In the tumor microenvironment (TME), these amino acids serve to support the elevated biosynthetic and energy demands of cancer cells, while simultaneously maintaining the growth, homeostasis, and effector function of tumor-infiltrating immune cells. To escape immune destruction, cancer cells utilize a variety of mechanisms to suppress the cytotoxic activity of effector T cells, facilitating T cell exhaustion. One such mechanism is the ability of cancer cells to overexpress metabolic enzymes specializing in the catabolism of arginine, glutamine, and the BCAAs in the TME. The action of such enzymes supplies cancer cells with metabolic intermediates that feed into the TCA cycle, supporting energy generation, or providing precursors for purine, pyrimidine, and polyamine biosynthesis. Armed with substantial metabolic flexibility, cancer cells redirect amino acids from the TME for their own advantage and growth, while leaving the local infiltrating effector T cells deprived of essential nutrients. This review addresses the metabolic pressure that cancer cells exert over immune cells in the TME by up-regulating amino acid metabolism, while discussing opportunities for targeting amino acid metabolism for therapeutic intervention. Special emphasis is given to the crosstalk between arginine, glutamine, and BCAA metabolism in affording cancer cells with metabolic dominance in the TME.

Anti-cancer effect of Rumex obtusifolius in combination with arginase/nitric oxide synthase inhibitors via downregulation of oxidative stress, inflammation, and polyamine synthesis

Cancer continues to be a leading cause of death worldwide, making the development of new treatment methods crucial in the fight against it. With cancer incidence rates increasing worldwide, ongoing research must focus on identifying new and effective ways to prevent and treat the disease. The combination of herbal extracts with chemotherapeutic agents has gained much interest as a novel strategy to combat cancer. Rumex obtusifolius L. is a wild plant known for its medicinal properties and is widely distributed worldwide. Our preclinical evaluations suggested that R. obtusifolius seed extracts possessed cancer-inhibiting properties and we also evaluated the beneficial effects of the arginase inhibitor NG-hydroxy-nor-L-arginine and nitric oxide inhibitor NG-nitro-L-arginine methyl ester in the treatment of breast cancer. The current study aimed to combine these observations and evaluate the antioxidant and antitumor properties of R. obtusifolius extracts alone and in combination with the arginase and nitric oxide synthase inhibitors. Metabolic characterization of the plant extract using a liquid chromatography/high-resolution mass spectrometry advanced system revealed the presence of 240 phenolic compounds many of which possess anticancer properties, according to the literature. In vitro studies revealed a significant cytotoxic effect of the R. obtusifolius extracts on the human colon (HT29) and breast cancer (MCF-7) cell lines. Thus, a new treatment approach of combining R. obtusifolius bioactive phytochemicals with the arginase and nitric oxide synthase inhibitors NG-nitro-L-arginine methyl ester and/or NG-hydroxy-nor-L-arginine, respectively, was proposed and could potentially be an effective way to treat breast cancer. Indeed, these combinations showed immunostimulatory, antiproliferative, antioxidant, anti-inflammatory, and antiangiogenic properties in a rat breast cancer model.

Pathways Affected by Falcarinol-Type Polyacetylenes and Implications for Their Anti-Inflammatory Function and Potential in Cancer Chemoprevention

Polyacetylene phytochemicals are emerging as potentially responsible for the chemoprotective effects of consuming apiaceous vegetables. There is some evidence suggesting that polyacetylenes (PAs) impact carcinogenesis by influencing a wide variety of signalling pathways, which are important in regulating inflammation, apoptosis, cell cycle regulation, etc. Studies have shown a correlation between human dietary intake of PA-rich vegetables with a reduced risk of inflammation and cancer. PA supplementation can influence cell growth, gene expression and immunological responses, and has been shown to reduce the tumour number in rat and mouse models. Cancer chemoprevention by dietary PAs involves several mechanisms, including effects on inflammatory cytokines, the NF-κB pathway, antioxidant response elements, unfolded protein response (UPR) pathway, growth factor signalling, cell cycle progression and apoptosis. This review summarises the published research on falcarinol-type PA compounds and their mechanisms of action regarding cancer chemoprevention and also identifies some gaps in our current understanding of the health benefits of these PAs.

Immunopotentiating Activity of Fucoidans and Relevance to Cancer Immunotherapy

Fucoidans, discovered in 1913, are fucose-rich sulfated polysaccharides extracted mainly from brown seaweed. These versatile and nontoxic marine-origin heteropolysaccharides have a wide range of favorable biological activities, including antitumor, immunomodulatory, antiviral, antithrombotic, anticoagulant, antithrombotic, antioxidant, and lipid-lowering activities. In the early 1980s, fucoidans were first recognized for their role in supporting the immune response and later, in the 1990s, their effects on immune potentiation began to emerge. In recent years, the understanding of the immunomodulatory effects of fucoidan has expanded significantly. The ability of fucoidan(s) to activate CTL-mediated cytotoxicity against cancer cells, strong antitumor property, and robust safety profile make fucoidans desirable for effective cancer immunotherapy. This review focusses on current progress and understanding of the immunopotentiation activity of various fucoidans, emphasizing their relevance to cancer immunotherapy. Here, we will discuss the action of fucoidans in different immune cells and review how fucoidans can be used as adjuvants in conjunction with immunotherapeutic products to improve cancer treatment and clinical outcome. Some key rationales for the possible combination of fucoidans with immunotherapy will be discussed. An update is provided on human clinical studies and available registered cancer clinical trials using fucoidans while highlighting future prospects and challenges.

DNA methyltransferase inhibition promotes recruitment of myeloid-derived suppressor cells to the tumor microenvironment through induction of tumor cell-intrinsic interleukin-1

DNA methyltransferase (DNMT) inhibitors are used for treatment of certain hematological malignancies and exert anti-cancer activity through diverse mechanisms, including reexpression of tumor suppressor genes and anti-viral responses triggered by expression of endogenous retroviruses. Despite advances in the pharmacokinetic properties of DNMT inhibitors, the efficacy of these drugs in solid cancers remains low. Here, we show in cell lines and clinical and experimental tumors across multiple cancer types that DNMT inhibition induces the expression of interleukin-1 (IL-1), a cytokine with proinflammatory and protumorigenic properties. Specifically, this tumor-intrinsic IL-1 expression modulates the chemokine landscape of tumors and leads to the recruitment of monocytic myeloid-derived suppressor cells to the tumor microenvironment, processes that can be blocked by IL-1 antagonists. Molecular analysis demonstrates complex patterns of IL-1 and interferon activation and crosstalk in response to DNMT inhibition, which depend on the integrity of IRF- and NF-κB-mediated antiviral pathways and may determine the outcome of DNMT-inhibitor treatment. Together, our results show that DNMT inhibitors may negatively affect the microenvironment of a large subset of tumors and suggest that co-treatment with IL-1 antagonists may be a favorable combination for these patients.

Systemic Nos2 Depletion and Cox inhibition limits TNBC disease progression and alters lymphoid cell spatial orientation and density

Antitumor immune polarization is a key predictor of clinical outcomes to cancer therapy. An emerging concept influencing clinical outcome involves the spatial location of CD8+ T cells, within the tumor. Our earlier work demonstrated immunosuppressive effects of NOS2 and COX2 tumor expression. Here, we show that NOS2/COX2 levels influence both the polarization and spatial location of lymphoid cells including CD8+ T cells. Importantly, elevated tumor NOS2/COX2 correlated with exclusion of CD8+ T cells from the tumor epithelium. In contrast, tumors expressing low NOS2/COX2 had increased CD8+ T cell penetration into the tumor epithelium. Consistent with a causative relationship between these observations, pharmacological inhibition of COX2 with indomethacin dramatically reduced tumor growth of the 4T1 model of TNBC in both WT and Nos2- mice. This regimen led to complete tumor regression in ∼20-25% of tumor-bearing Nos2- mice, and these animals were resistant to tumor rechallenge. Th1 cytokines were elevated in the blood of treated mice and intratumoral CD4+ and CD8+ T cells were higher in mice that received indomethacin when compared to control untreated mice. Multiplex immunofluorescence imaging confirmed our phenotyping results and demonstrated that targeted Nos2/Cox2 blockade improved CD8+ T cell penetration into the 4T1 tumor core. These findings are consistent with our observations in low NOS2/COX2 expressing breast tumors proving that COX2 activity is responsible for limiting the spatial distribution of effector T cells in TNBC. Together these results suggest that clinically available NSAID's may provide a cost-effective, novel immunotherapeutic approach for treatment of aggressive tumors including triple negative breast cancer.

The Breast Cancer Protooncogenes HER2, BRCA1 and BRCA2 and Their Regulation by the iNOS/NOS2 Axis

The expression of inducible nitric oxide synthase (iNOS; NOS2) and derived NO in various cancers was reported to exert pro- and anti-tumorigenic effects depending on the levels of expression and the tumor types. In humans, the breast cancer level of iNOS was reported to be overexpressed, to exhibit pro-tumorigenic activities, and to be of prognostic significance. Likewise, the expression of the oncogenes HER2, BRCA1, and BRCA2 has been associated with malignancy. The interrelationship between the expression of these protooncogenes and oncogenes and the expression of iNOS is not clear. We have hypothesized that there exist cross-talk signaling pathways between the breast cancer protooncogenes, the iNOS axis, and iNOS-mediated NO mutations of these protooncogenes into oncogenes. We review the molecular regulation of the expression of the protooncogenes in breast cancer and their interrelationships with iNOS expression and activities. In addition, we discuss the roles of iNOS, HER2, BRCA1/2, and NO metabolism in the pathophysiology of cancer stem cells. Bioinformatic analyses have been performed and have found suggested molecular alterations responsible for breast cancer aggressiveness. These include the association of BRCA1/2 mutations and HER2 amplifications with the dysregulation of the NOS pathway. We propose that future studies should be undertaken to investigate the regulatory mechanisms underlying the expression of iNOS and various breast cancer oncogenes, with the aim of identifying new therapeutic targets for the treatment of breast cancers that are refractory to current treatments.

Ethanol Extract of Sargassum siliquastrum Inhibits Lipopolysaccharide-Induced Nitric Oxide Generation by Downregulating the Nuclear Factor-Kappa B Signaling Pathway

Sargassum siliquastrum (SS) is an edible brown seaweed widely consumed in Korea and considered a functional food source. Previous studies have reported various biological activities of SS extracts, including antioxidant and hepatoprotective properties. In the present study, we examined the anti-inflammatory effects of the SS extract and assessed the underlying mechanism of action. The SS extract significantly inhibited lipopolysaccharide (LPS)-induced nitric oxide (NO) production in a dose-dependent manner (% of NO production at 500 μg/mL: 60.1 ± 0.9%), with no obvious toxicity. Furthermore, the SS extract inhibited mRNA and protein expression levels of inducible NO synthase, as well as LPS-induced expression and production of proinflammatory cytokines such as IL-1β, IL-6, or TNF-α (IL-6 production (ng/mL) : LPS−: 0.7 ± 0.3; LPS+: 68.1 ± 2.8; LPS + SS extract: 51.9 ± 1.2; TNF-α production (ng/mL) : LPS−: 0.3 ± 0.1; LPS+: 23.0 ± 0.1; LPS + SS extract: 18.2 ± 10.8). Mechanistically, the SS extract attenuated LPS-induced activation of the nuclear factor kappa-light-chain-enhancer of activated B cells (nuclear factor-kappa B, NF-κB) signaling pathway such as phosphorylation of NF-κB p65 and degradation of IκB-α, thereby blocking LPS-induced activation of NF-κB transcriptional activity. The SS extract also enhanced LPS-induced heme oxygenase-1 expression and attenuated LPS-induced cellular reactive oxygen species production (% of ROS production at 500 μg/mL: 52.2 ± 1.3%). Collectively, these findings suggest that the SS extract elicits anti-inflammatory effects in mouse macrophage cells.

Targeting tumor-associated macrophages for cancer immunotherapy

Tumor-associated macrophages (TAMs) are one of the most abundant immune components in the tumor microenvironment and play a plethora of roles in regulating tumorigenesis. Therefore, the therapeutic targeting of TAMs has emerged as a new paradigm for immunotherapy of cancer. Herein, the review summarizes the origin, polarization, and function of TAMs in the progression of malignant diseases. The understanding of such knowledge leads to several distinct therapeutic strategies to manipulate TAMs to battle cancer, which include those to reduce TAM abundance, such as depleting TAMs or inhibiting their recruitment and differentiation, and those to harness or boost the anti-tumor activities of TAMs such as blocking phagocytosis checkpoints, inducing antibody-dependent cellular phagocytosis, and reprogramming TAM polarization. In addition, modulation of TAMs may reshape the tumor microenvironment and therefore synergize with other cancer therapeutics. Therefore, the rational combination of TAM-targeting therapeutics with conventional therapies including radiotherapy, chemotherapy, and other immunotherapies is also reviewed. Overall, targeting TAMs presents itself as a promising strategy to add to the growing repertoire of treatment approaches in the fight against cancer, and it is hopeful that these approaches currently being pioneered will serve to vastly improve patient outcomes and quality of life.

Nitric oxide favours tumour-promoting inflammation through mitochondria-dependent and -independent actions on macrophages

Production of nitric oxide (NO) has been demonstrated in several malignancies, however its role remains not fully understood, specifically in relation to the metabolic and functional implications that it may have on immune cells participating in tumorigenesis. Here, we show that inducible NO synthase (iNOS) is expressed in cancers of the colon and the prostate, mainly by tumour cells, and NO generation is evidenced by widespread nitrotyrosine (NT) staining in tumour tissue. Furthermore, presence of NT is observed in the majority of tumour-associated macrophages (TAMs), despite low iNOS expression by these cells, suggesting that NO from the tumour microenvironment affects TAMs. Indeed, using a co-culture model, we demonstrate that NO produced by colon and prostate cancer cells is sufficient to induce NT formation in neighbouring macrophages. Moreover, exposure to exogenous NO promotes mitochondria-dependent and -independent changes in macrophages, which orientate their polarity towards an enhanced pro-inflammatory phenotype, whilst decreasing antigen-presenting function and wound healing capacity. Abrogating endogenous NO generation in murine macrophages, on the other hand, decreases their pro-inflammatory phenotype. These results suggest that the presence of NO in cancer may regulate TAM metabolism and function, favouring the persistence of inflammation, impairing healing and subverting adaptive immunity responses.

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Nitric oxide (NO) from the cancer microenvironment acts on tumour-associated macrophages (TAMs).

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NO induces a phenotypic shift in macrophages through mitochondria-dependent and -independent pathways.

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NO favours pro-inflammatory cytokine production whilst decreasing macrophage function as antigen presenting cell.

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NO impairs repair function of macrophages.

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Presence of NO in cancer may regulate TAM metabolism and function, favouring tumour-promoting inflammation.

Influence of the Metabolism on Myeloid Cell Functions in Cancers: Clinical Perspectives

Tumor metabolism plays a crucial role in sustaining tumorigenesis. There have been increasing reports regarding the role of tumor metabolism in the control of immune cell functions, generating a potent immunosuppressive contexture that can lead to immune escape. The metabolic reprogramming of tumor cells and the immune escape are two major hallmarks of cancer, with several instances of crosstalk between them. In this paper, we review the effects of tumor metabolism on immune cells, focusing on myeloid cells due to their important role in tumorigenesis and immunosuppression from the early stages of the disease. We also discuss ways to target this specific crosstalk in cancer patients.

Exhaled Nitric Oxide Level in Pharynx Angioedema

Airway inflammation is related to increased nitric oxide production. It can be assessed noninvasively with exhaled nitric oxide measurement. As airway inflammation was supposed to be present in chronic urticaria and angioedema patients we hypothesized increased exhaled nitric oxide in this group. Twenty-six symptomatic chronic urticaria patients with an acute episode of pharynx angioedema (17 women and 9 men, median age 35) were included in the study group. None of the patients reported a history of asthma, allergic rhinitis or cigarette smoking. The control group consisted of 29 non-smoking healthy subjects (19 women and 10 men, median age 22) without any history of atopy. Exhaled nitric oxide measurement was performed in all subjects. Exhaled nitric oxide levels in the angioedema group did not differ statistically significantly from those detected in healthy subjects (15.5 ppb and 17.0 ppb respectively). Our results indicate the lack of airway inflammation in chronic urticaria patients with pharynx angioedema.

Landscape of Immune-Related Markers and Potential Therapeutic Targets in Soft Tissue Sarcoma

Simple Summary

Despite being a group of rare diseases of mesenchymal origin, soft tissue sarcomas are heterogenous and display varying clinical behavior, and depending on the subtype, intermediate- and high-grade sarcomas have significant metastatic potential, making it difficult to establish a standardized therapy. Our work, as well as studies by others, emphasizes the high potential of immunotherapy for the treatment of sarcoma. The aim of this study was to determine whether specific genomic alterations, as well as the expression of infiltrating cytotoxic and suppressive cell type markers identified by next-generation sequencing (NGS), warrant further consideration of immunotherapy agents for treating certain soft tissue sarcoma subtypes. Altogether, our data provide a better understanding of the immune composition of different sarcoma subtypes to better identify novel therapy targets.

Abstract

Soft tissue sarcomas, depending on the subtype and grade, frequently recur and become metastatic after localized treatment. There is now great interest in applying immunotherapy to sarcomas to immuno-profile the different subtypes and immune monitor for prognosis. Our group previously showed that key immunotherapy target genes are present in sarcomas. Here, we extend our findings by demonstrating that sarcomas with a relatively high mutational load are likely to be more sensitive to immunotherapy compared to sarcomas with a lower mutation load. We also show that sarcomas with a higher mutation load are associated with the expression of key immune-related genes. We found that CD8+ T cells are present in sarcoma subtypes and that PD-L2 is highly expressed. These findings further define potential mechanisms behind the immunotherapy response of specific sarcoma subtypes and can be used to develop more optimal treatments in the future.

Molecular Subtypes of Oral Squamous Cell Carcinoma Based on Immunosuppression Genes Using a Deep Learning Approach

Background: The mechanisms through which immunosuppressed patients bear increased risk and worse survival in oral squamous cell carcinoma (OSCC) are unclear. Here, we used deep learning to investigate the genetic mechanisms underlying immunosuppression in the survival of OSCC patients, especially from the aspect of various survival-related subtypes. Materials and methods: OSCC samples data were obtained from The Cancer Genome Atlas (TCGA), International Cancer Genome Consortium (ICGC), and OSCC-related genetic datasets with survival data in the National Center for Biotechnology Information (NCBI). Immunosuppression genes (ISGs) were obtained from the HisgAtlas and DisGeNET databases. Survival analyses were performed to identify the ISGs with significant prognostic values in OSCC. A deep learning (DL)-based model was established for robustly differentiating the survival subpopulations of OSCC samples. In order to understand the characteristics of the different survival-risk subtypes of OSCC samples, differential expression analysis and functional enrichment analysis were performed. Results: A total of 317 OSCC samples were divided into one inferring cohort (TCGA) and four confirmation cohorts (ICGC set, GSE41613, GSE42743, and GSE75538). Eleven ISGs (i.e., BGLAP, CALCA, CTLA4, CXCL8, FGFR3, HPRT1, IL22, ORMDL3, TLR3, SPHK1, and INHBB) showed prognostic value in OSCC. The DL-based model provided two optimal subgroups of TCGA-OSCC samples with significant differences (p = 4.91E-22) and good model fitness [concordance index (C-index) = 0.77]. The DL model was validated by using four external confirmation cohorts: ICGC cohort (n = 40, C-index = 0.39), GSE41613 dataset (n = 97, C-index = 0.86), GSE42743 dataset (n = 71, C-index = 0.87), and GSE75538 dataset (n = 14, C-index = 0.48). Importantly, subtype Sub1 demonstrated a lower probability of survival and thus a more aggressive nature compared with subtype Sub2. ISGs in subtype Sub1 were enriched in the tumor-infiltrating immune cells-related pathways and cancer progression-related pathways, while those in subtype Sub2 were enriched in the metabolism-related pathways. Conclusion: The two survival subtypes of OSCC identified by deep learning can benefit clinical practitioners to divide immunocompromised patients with oral cancer into two subpopulations and give them target drugs and thus might be helpful for improving the survival of these patients and providing novel therapeutic strategies in the precision medicine area.

Clinical and molecular parameters associated to pneumonitis development in non-small-cell lung cancer patients receiving chemoimmunotherapy from NADIM trial

BACKGROUND

Pneumonitis (Pn) is one of the main immune-related adverse effects, having a special importance in lung cancer, since they share affected tissue. Despite its clinical relevance, Pn development remains an unpredictable treatment adverse effect, whose mechanisms are mainly unknown, being even more obscure when it is associated to chemoimmunotherapy.

METHODS

In order to identify parameters associated to treatment related Pn, we analyzed clinical variables and molecular parameters from 46 patients with potentially resectable stage IIIA non-small-cell lung cancer treated with neoadjuvant chemoimmunotherapy included in the NADIM clinical trial (NCT03081689). Pn was defined as clinical or radiographic evidence of lung inflammation without alternative diagnoses, from treatment initiation to 180 days.

RESULTS

Among 46 patients, 12 developed Pn (26.1%). Sex, age, smoking status, packs-year, histological subtype, clinical or pathological response, progression-free survival, overall survival and number of nivolumab cycles, were not associated to Pn development. Regarding molecular parameters at diagnosis, Pn development was not associated to programmed death ligand 1, TPS, T cell receptor repertoire parameters, or tumor mutational burden. However, patients who developed Pn had statistically significant lower blood median levels of platelet to monocyte ratio (p=0.012) and teratocarcinoma-derived growth factor 1 (p=0.013; area under the curve (AUC) 0.801), but higher median percentages of natural killers (NKs) (p=0.019; AUC 0.786), monocytes (p=0.017; AUC 0.791), MSP (p=0.006; AUC 0.838), PARN (p=0.017; AUC 0.790), and E-Cadherin (p=0.022; AUC 0.788). In addition, the immune scenario of Pn after neoadjuvant treatment involves: high levels of neutrophils and NK cells, but low levels of B and T cells in peripheral blood; increased clonality of intratumoral T cells; and elevated plasma levels of several growth factors (EGF, HGF, VEGF, ANG-1, PDGF, NGF, and NT4) and inflammatory cytokines (MIF, CCL16, neutrophil gelatinase-associated lipocalin, BMP-4, and u-PAR).

CONCLUSIONS

Although statistically underpowered, our results shed light on the possible mechanisms behind Pn development, involving innate and adaptative immunity, and open the possibility to predict patients at high risk. If confirmed, this may allow the personalization of both, the surveillance strategy and the therapeutic approaches to manage Pn in patients receiving chemoimmunotherapy.

Selective Inhibitors of the Inducible Nitric Oxide Synthase as Modulators of Cell Responses in LPS-Stimulated Human Monocytes

Inducible nitric oxide synthase (iNOS) is a crucial enzyme involved in monocyte cell response towards inflammation, and it is responsible for the production of sustained amounts of nitric oxide. This free radical molecule is involved in the defense against pathogens; nevertheless, its continuous and dysregulated production contributes to the development of several pathological conditions, including inflammatory and autoimmune diseases. In the present study, we investigated the effects of two new iNOS inhibitors, i.e., 4-(ethanimidoylamino)-N-(4-fluorophenyl)benzamide hydrobromide (FAB1020) and N-{3-[(ethanimidoylamino)methyl]benzyl}-l-prolinamidedihydrochloride (CM554), on human LPS-stimulated monocytes, using the 1400 W compound as a comparison. Our results show that CM544 and FAB1020 are selective and decrease cytotoxicity, IL-6 secretion and LPS-stimulated monocyte migration. Furthermore, the modulation of iNOS, nitrotyrosine and Nrf2 were analyzed at the protein level. Based on the collected preliminary results, the promising therapeutic value of the investigated compounds emerges, as they appear able to modulate the pro-inflammatory LPS-stimulated response in the low micromolar range in human monocytes.

The Role of Metabolism in Tumor Immune Evasion: Novel Approaches to Improve Immunotherapy

The tumor microenvironment exhibits altered metabolic properties as a consequence of the needs of tumor cells, the natural selection of the most adapted clones, and the selfish relationship with other cell types. Beyond its role in supporting uncontrolled tumor growth, through energy and building materials obtention, metabolism is a key element controlling tumor immune evasion. Immunotherapy has revolutionized the treatment of cancer, being the first line of treatment for multiple types of malignancies. However, many patients either do not benefit from immunotherapy or eventually relapse. In this review we overview the immunoediting process with a focus on the metabolism-related elements that are responsible for increased immune evasion, either through reduced immunogenicity or increased resistance of tumor cells to the apoptotic action of immune cells. Finally, we describe the main molecules to modulate these immune evasion processes through the control of the metabolic microenvironment as well as their clinical developmental status.

Nitric Oxide in Hematological Cancers: Partner or Rival?

Significance: Hematological malignancies represent the fourth most diagnosed cancer. Relapse and acquired resistance to anticancer therapy constitute two actual issues that need to be overcome. Nitric oxide (NO) plays a pivotal role in regulating cancer progression. At present, many studies are attempting to uncover the potentials of modulating NO levels to improve the efficacy of currently available treatments against lymphoma, leukemia, and myeloma. Recent Advances: It is becoming progressively clear that NO modulation may help hematological cancer management, either by targeting directly tumor cells or by driving the immune system to eliminate cancer cells. Critical Issues: NO is a dual molecule that can have a tumor-protecting or stimulating effect, depending on its local concentration. Moreover, NO is able to target a wide range of molecules involved in both cancer genesis and evolution. In this review, an overview of the recent findings regarding the pivotal role played by NO and nitric oxide synthase in cancer progression and anticancer therapy is presented, with particular focus on hematological malignancies. Future Directions: It is critical to establish the cancer-specific function of NO and critically drive its modulation to improve cancer management toward a personalized approach. This has a special importance in hematological tumors, where the urgency of finding eradicative therapies is constant. Antioxid. Redox Signal. 34, 383-401.

Myeloid-Derived Suppressor Cell Differentiation in Cancer: Transcriptional Regulators and Enhanceosome-Mediated Mechanisms

Myeloid-derived Suppressor Cells (MDSCs) are a sub-population of leukocytes that are important for carcinogenesis and cancer immunotherapy. During carcinogenesis or severe infections, inflammatory mediators induce MDSCs via aberrant differentiation of myeloid precursors. Although several transcription factors, including C/EBPβ, STAT3, c-Rel, STAT5, and IRF8, have been reported to regulate MDSC differentiation, none of them are specifically expressed in MDSCs. How these lineage-non-specific transcription factors specify MDSC differentiation in a lineage-specific manner is unclear. The recent discovery of the c-Rel−C/EBPβ enhanceosome in MDSCs may help explain these context-dependent roles. In this review, we examine several transcriptional regulators of MDSC differentiation, and discuss the concept of non-modular regulation of MDSC signature gene expression by transcription factors such as c-Rel and C/EBPß.

Fine-Tuning the Tumour Microenvironment: Current Perspectives on the Mechanisms of Tumour Immunosuppression

Immunotherapy has revolutionised the treatment of cancers by harnessing the power of the immune system to eradicate malignant tissue. However, it is well recognised that some cancers are highly resistant to these therapies, which is in part attributed to the immunosuppressive landscape of the tumour microenvironment (TME). The contexture of the TME is highly heterogeneous and contains a complex architecture of immune, stromal, vascular and tumour cells in addition to acellular components such as the extracellular matrix. While understanding the dynamics of the TME has been instrumental in predicting durable responses to immunotherapy and developing new treatment strategies, recent evidence challenges the fundamental paradigms of how tumours can effectively subvert immunosurveillance. Here, we discuss the various immunosuppressive features of the TME and how fine-tuning these mechanisms, rather than ablating them completely, may result in a more comprehensive and balanced anti-tumour response.

Roles of the Dynamic Tumor Immune Microenvironment in the Individualized Treatment of Advanced Clear Cell Renal Cell Carcinoma

Immune checkpoint inhibitors (ICIs) are currently a first-line treatment option for clear cell renal cell carcinoma (ccRCC). However, recent clinical studies have shown that a large number of patients do not respond to ICIs. Moreover, only a few patients achieve a stable and durable response even with combination therapy based on ICIs. Available studies have concluded that the response to immunotherapy and targeted therapy in patients with ccRCC is affected by the tumor immune microenvironment (TIME), which can be manipulated by targeted therapy and tumor genomic characteristics. Therefore, an in-depth understanding of the dynamic nature of the TIME is important for improving the efficacy of immunotherapy or combination therapy in patients with advanced ccRCC. Here, we explore the possible mechanisms by which the TIME affects the efficacy of immunotherapy and targeted therapy, as well as the factors that drive dynamic changes in the TIME in ccRCC, including the immunomodulatory effect of targeted therapy and genomic changes. We also describe the progress on novel therapeutic modalities for advanced ccRCC based on the TIME. Overall, this review provides valuable information on the optimization of combination therapy and development of individualized therapy for advanced ccRCC.

Cytotoxicity of apigenin toward multiple myeloma cell lines and suppression of iNOS and COX-2 expression in STAT1-transfected HEK293 cells

BACKGROUND

Apigenin is one of the most abundant dietary flavonoids that possesses multiple bio-functions.

PURPOSE

This study was designed to determine the influence of apigenin on gene expressions, cancer cells, as well as STAT1/COX-2/iNOS pathway mediated inflammation and tumorigenesis in HEK293-STAT1 cells. Furthermore, the cytotoxic activity toward multiple myeloma (MM) cell lines was investigated.

METHODS

Bioinformatic analyses were used to predict the sensitivity and resistance of tumor cells toward apigenin and to determine cellular pathways influenced by this compound. The cytotoxic and ferroptotic activity of apigenin was examined by the resazurin reduction assay. Additionally, we evaluated apoptosis, and cell cycle distribution, induction of reactive oxygen species (ROS) and loss of integrity of mitochondrial membrane (MMP) by using the flow cytometry analysis. DAPI staining was used to detect characteristic apoptotic features. Furthermore, we verified its anti-inflammatory and additional mechanism of cell death by western blotting.

RESULTS

COMPARE and hierarchical cluster analyses exhibited that 29 of 55 tumor cell lines were sensitive against apigenin (p < 0.001). The Ingenuity Pathway Analysis data showed that important bio-functions affected by apigenin were: gene expression, cancer, hematological system development and function, inflammatory response, and cell cycle. The STAT1 transcription factor was chosen as target protein on the basis of gene promoter binding motif analyses. Apigenin blocked cell proliferation of wild-type HEK293 and STAT1 reporter cells (HEK293-STAT1), promoted STAT1 suppression and subsequent COX-2 and iNOS inhibition. Apigenin also exhibited synergistic activity in combination with doxorubicin toward HEK293-STAT1 cells. Apigenin exerted excellent growth-inhibitory activity against MM cells in a concentration-dependent manner with the greatest activity toward NCI-H929 (IC₅₀ value: 10.73 ± 3.21 μM). Apigenin induced apoptosis, cell cycle arrest, ferroptosis and autophagy in NCI-H929 cells.

CONCLUSION

Apigenin may be a suitable candidate for MM treatment. The inhibition of the STAT1/COX-2/iNOS signaling pathway by apigenin is an important mechanism not only in the suppression of inflammation but also in induction of apoptosis.

LncRNA HEIH/miR-939-5p interplay modulates triple-negative breast cancer progression through NOS2-induced nitric oxide production

This study aimed to unravel the regulatory role of noncoding RNAs (ncRNA) on the nitric oxide (NO) machinery system in triple-negative breast cancer (TNBC) patients and to further assess the influence of NO-modulating ncRNAs on TNBC progression, immunogenic profile, and the tumor microenvironment (TME). The results revealed miR-939-5p and lncRNA HEIH as novel ncRNAs modulating NO machinery in TNBC. MiR-939-5p, an underexpressed microRNA (miRNA) in BC patients, showed an inhibitory effect on NOS2 and NOS3 transcript levels on TNBC cells. In contrast, HEIH was found to be markedly upregulated in TNBC patients and showed a modulatory role on miR-939-5p/NOS2/NO axis. Functionally, miR-939-5p was characterized as a tumor suppressor miRNA while HEIH was categorized as a novel oncogenic lncRNA in TNBC. Finally, knocking down of HEIH resulted in improvement of immunogenic profile of TNBC cells through inducing MICA/B and suppressing the immune checkpoint inhibitor PDL1. In the same context, knockdown of HEIH resulted in the alleviation of the immune-suppressive TME by repressing interleukin-10 and tumor necrosis factor-α levels. In conclusion, this study identifies miR-939-5p as a tumor suppressor miRNA while HEIH as an oncogenic lncRNA exhibiting its effect through miR-939-5p/NOS2/NO axis. Therefore, repressing BC hallmarks, improving TNBC immunogenic profile, and trimming TME.

Tumor associated macrophages and 'NO'

Nitric oxide (NO) and its pro and anti-tumor activities are dual roles that continue to be debated in cancer biology. The cell situations in the tumor and within the tumor microenvironment also have roles involving NO. In early tumorigenic events, macrophages in the tumor microenvironment promote tumor cell death, and later are reprogramed to support the growth of tumor, through regulatory events involving NO and several stimulatory signals. These two opposing and active phenotypes of tumor associated macrophages known as the M1 or anti-tumorigenic state and M2 or pro-tumorigenic state show differences in metabolic pathways such as glycolysis and arginine utilization, signaling pathways and cytokine induction including iNOS expression, therefore contributing to their function. Polarization of M2 to M1 macrophages, inhibition of M2 state, or reprogramming via NO in combination with other signals may determine or alter tumor kinetics. These strategies and an overview are presented.

Distinct Neutrophil Populations in the Spleen During PICS

While mortality after acute sepsis has decreased, the long-term recovery for survivors is still poor, particularly those developing persistent inflammation, immunosuppression, and catabolism syndrome (PICS). While previously thought that activated neutrophils responding to the acute phase of sepsis migrate to the spleen to undergo cell death and contribute to immunosuppression, our data show a significant accumulation of distinct, yet functional, neutrophil populations in the spleen in a murine model of PICS. The exact role and function of neutrophils in this response is still unclear. The objective of our study was to better define the immune function of splenic neutrophils to determine if this could give insight into the pathogenesis of PICS. Using a murine model of cecal ligation and puncture (CLP), which demonstrates all characteristics of PICS by 8 days, spleens were harvested, and neutrophils were identified by Ly6G and CD11b expression via flow cytometry. Nearly all splenic neutrophils expressed CD54, but there were distinct CD54^hi and CD54^lo cells, with the majority being CD54^lo cells during PICS. The CD54^hi population showed traditional, proinflammatory properties, but a relatively decreased chemotactic response, while CD54^lo cells had significantly higher chemotaxis, yet significantly decreased proinflammatory functions. Using 5-ethynyl-2′-deoxyuridine (EdU) incorporation, we found that the CD54^hi population on day 2 after CLP may be participating in emergency myelopoiesis. However, the vast majority of the CD54^lo population were paused in the G₁ phase at this time point and not proliferating. By day 8 after CLP, most of the CD54^hi cells in the spleen were no longer proliferating, while the CD54^lo cells were, indicating that CD54^lo dominate in extramedullary myelopoiesis at later time points. Almost none of the neutrophils produced arginase or inducible nitric oxide synthase (iNOS), indicating that these are not suppressor cells. Overall, our data demonstrate that neutrophil accumulation in the spleen during PICS is related to extramedullary myelopoiesis, leading to the production of immature neutrophils. While not suppressor cells, the majority have greater chemotactic function but less inflammatory responsiveness, which may contribute to the immunosuppression seen in PICS. Attention to these distinct neutrophil populations after septic or other systemic inflammatory responses is therefore critical to understanding the mechanisms of PICS.

Cancer-educated mesenchymal stem cells promote the survival of cancer cells at primary and distant metastatic sites via the expansion of bone marrow-derived-PMN-MDSCs

Bone marrow mesenchymal stem cells (BMSCs) are multipotent stromal cells that can differentiate into a variety of cell types. BMSCs are chemotactically guided towards the cancer cells and contribute to the formation of a cancer microenvironment. The homing of BMSCs was affected by various factors. Disseminated tumour cells (DTCs) in distant organs, especially in the bone marrow, are the source of cancer metastasis and cancer relapse. DTC survival is also determined by the microenvironment. Here we aim to elucidate how cancer-educated BMSCs promote the survival of cancer cells at primary tumour sites and distant sites. We highlight the dynamic change by identifying different gene expression signatures in intratumoral BMSCs and in BMSCs that move back in the bone marrow. Intratumoral BMSCs acquire high mobility and displayed immunosuppressive effects. Intratumoral BMSCs that ultimately home to the bone marrow exhibit a strong immunosuppressive function. Cancer-educated BMSCs promote the survival of lung cancer cells via expansion of MDSCs in bone marrow, primary tumour sites and metastatic sites. These Ly6G+ MDSCs suppress proliferation of T cells. CXCL5, nitric oxide and GM-CSF produced by cancer-educated BMSCs contribute to the formation of malignant microenvironments. Treatment with CXCL5 antibody, the iNOS inhibitor 1400w and GM-CSF antibody reduced MDSC expansion in the bone marrow, primary tumour sites and metastatic sites, and promoted the efficiency of PD-L1 antibody. Our study reveals that cancer-educated BMSCs are the component of the niche for primary lung cancer cells and DTCs, and that they can be the target for immunotherapy.

Oxidative stress and antioxidants in the pathophysiology of malignant melanoma

The high number of somatic mutations in the melanoma genome associated with cumulative ultra violet (UV) exposure has rendered it one of the most difficult of cancers to treat. With new treatment approaches based on targeted and immune therapies, drug resistance has appeared as a consistent problem. Redox biology, including reactive oxygen and nitrogen species (ROS and RNS), plays a central role in all aspects of melanoma pathophysiology, from initiation to progression and to metastatic cells. The involvement of melanin production and UV radiation in ROS/RNS generation has rendered the melanocytic lineage a unique system for studying redox biology. Overall, an elevated oxidative status has been associated with melanoma, thus much effort has been expended to prevent or treat melanoma using antioxidants which are expected to counteract oxidative stress. The consequence of this redox-rebalance seems to be two-fold: on the one hand, cells may behave less aggressively or even undergo apoptosis; on the other hand, cells may survive better after being disseminated into the circulating system or after drug treatment, thus resulting in metastasis promotion or further drug resistance. In this review we summarize the current understanding of redox signaling in melanoma at cellular and systemic levels and discuss the experimental and potential clinic use of antioxidants and new epigenetic redox modifiers.

Nitric Oxide-Mediated Enhancement and Reversal of Resistance of Anticancer Therapies

In the last decade, immune therapies against human cancers have emerged as a very effective therapeutic strategy in the treatment of various cancers, some of which are resistant to current therapies. Although the clinical responses achieved with many therapeutic strategies were significant in a subset of patients, another subset remained unresponsive initially, or became resistant to further therapies. Hence, there is a need to develop novel approaches to treat those unresponsive patients. Several investigations have been reported to explain the underlying mechanisms of immune resistance, including the anti-proliferative and anti-apoptotic pathways and, in addition, the increased expression of the transcription factor Yin-Yang 1 (YY1) and the programmed death ligand 1 (PD-L1). We have reported that YY1 leads to immune resistance through increasing HIF-1α accumulation and PD-L1 expression. These mechanisms inhibit the ability of the cytotoxic T-lymphocytes to mediate their cytotoxic functions via the inhibitory signal delivered by the PD-L1 on tumor cells to the PD-1 receptor on cytotoxic T-cells. Thus, means to override these resistance mechanisms are needed to sensitize the tumor cells to both cell killing and inhibition of tumor progression. Treatment with nitric oxide (NO) donors has been shown to sensitize many types of tumors to chemotherapy, immunotherapy, and radiotherapy. Treatment of cancer cell lines with NO donors has resulted in the inhibition of cancer cell activities via, in part, the inhibition of YY1 and PD-L1. The NO-mediated inhibition of YY1 was the result of both the inhibition of the upstream NF-κB pathway as well as the S-nitrosylation of YY1, leading to both the downregulation of YY1 expression as well as the inhibition of YY1-DNA binding activity, respectively. Also, treatment with NO donors induced the inhibition of YY1 and resulted in the inhibition of PD-L1 expression. Based on the above findings, we propose that treatment of tumor cells with the combination of NO donors, at optimal noncytotoxic doses, and anti-tumor cytotoxic effector cells or other conventional therapies will result in a synergistic anticancer activity and tumor regression.

Immunomodulatory roles of nitric oxide in cancer: tumor microenvironment says "NO" to antitumor immune response

In recent years, an increasing number of studies have shown that there is an important connection between nitric oxide (NO) and the pathology of malignant diseases, but we are far from a complete comprehension of how this simple diatomic molecule contributes to tumorigenesis. The emerging identification of immune-mediated mechanisms regulated by NO may help to unravel the intricate and complex relationships between NO and cancer. Therefore, this review provides a summary of recent advances in our understanding of the immunomodulatory role of NO in cancer, and in particular the role of this pleiotropic signaling molecule as an immunosuppressive mediator in the tumor microenvironment. We will discuss the participation of NO in the different strategies used by tumors to escape from immune system-mediated recognition, including the acquisition of stem cell like capacities by tumor cells and the metabolic reprogramming of tumor infiltrating immune cells. Finally, we will also discuss different therapeutic strategies directed against NO for abating the immunosuppressive tumor microenvironment and to increase the efficacy of immunotherapy in cancer.

α-GalCer and iNKT Cell-Based Cancer Immunotherapy: Realizing the Therapeutic Potentials

NKT cells are CD1d-restricted innate-like T cells expressing both T cell receptor and NK cell markers. The major group of NKT cells in both human and mice is the invariant NKT (iNKT) cells and the best-known function of iNKT cells is their potent anti-tumor function in mice. Since its discovery 25 years ago, the prototype ligand of iNKT cells, α-galactosylceramide (α-GalCer) has been used in over 30 anti-tumor clinical trials with mostly suboptimal outcomes. To realize its therapeutic potential, numerous preclinical models have been developed to optimize the scheme and strategies for α-GalCer-based cancer immunotherapies. Nevertheless, since there is no standard protocol for α-GalCer delivery, we reviewed the preclinical studies with a focus on B16 melanoma model in the goal of identifying the best treatment schemes for α-GalCer treatment. We then reviewed the current progress in developing more clinically relevant mouse models for these preclinical studies, most notably the generation of new mouse models with a humanized CD1d/iNKT cell system. With ever-emerging novel iNKT cell ligands, invention of novel α-GalCer delivery strategies and significantly improved preclinical models for optimizing these new strategies, one can be hopeful that the full potential of anti-tumor potential for α-GalCer will be realized in the not too distant future.

Prognostic Value of Inducible Nitric Oxide Synthase (iNOS) in Human Cancer: A Systematic Review and Meta-Analysis

Background

Inducible nitric oxide synthase (iNOS) is confirmed to regulate the production of nitric oxide (NO) when cells are exposed to external stimulus. Recent publications revealed that overexpression of iNOS predicted poor clinical outcomes for patients with malignant cancers, e.g., gastric, bladder, and colorectal cancers; however, several studies reported no obvious relationship between iNOS expression and prognosis of solid tumors. The aim of our study was to investigate the pooled effect of the prognostic value of iNOS expression.

Materials and Methods

We performed a systematic search of PubMed, Web of Science, and Embase databases up to January 15, 2019. The concerned outcomes of interest included overall survival (OS), cancer-special survival (CSS), and recurrence-free survival (RFS).

Results

Fourteen studies with 1,758 patients were included in this meta-analysis, and we reached the conclusion that increased iNOS expression was significantly associated with worse OS (HR: 1.89, 95% CI: 1.57 - 2.28, p ≤ 0.001), worse CSS (HR: 3.13, 95% CI: 1.88 - 5.20, p ≤ 0.001), and worse RFS (HR: 2.16, 95% CI: 1.29 - 3.62, p = 0.003) in solid tumors. Furthermore, the subgroup analysis identified the significant relationship of high iNOS expression with poor OS in gastric cancer. No obvious publication bias was detected by Begg's tests.

Conclusion

In summary, the results drawn in our meta-analysis demonstrated that elevated expression of iNOS had a significant association with poor survival in human cancer. iNOS might serve as a promising predictive biomarker of prognosis in cancer patients, and well-designed prospective studies are further needed to substantiate the prognostic value of iNOS.

Upstream signaling events leading to elevated production of pro-survival nitric oxide in photodynamically-challenged glioblastoma cells

Nitric oxide (NO) generated endogenously by inducible nitric oxide synthase (iNOS) promotes growth and migration/invasion of glioblastoma cells and also fosters resistance to chemotherapy and ionizing radiotherapy. Our recent studies revealed that glioblastoma cell iNOS/NO also opposes the cytotoxic effects of non-ionizing photodynamic therapy (PDT), and moreover stimulates growth/migration aggressiveness of surviving cells. These negative responses, which depended on PI3K/Akt/NF-κB activation, were strongly suppressed by blocking iNOS transcription with JQ1, a BET bromodomain inhibitor. In the present study, we sought to identify additional molecular events that precede iNOS transcriptional upregulation. Akt activation, iNOS induction, and viability loss in PDT-challenged glioblastoma U87 cells were all strongly inhibited by added l-histidine, consistent with primary involvement of photogenerated singlet oxygen (¹O₂). Transacetylase p300 not only underwent greater Akt-dependent activation after PDT, but greater interaction with NF-κB subunit p65, which in turn exhibited greater K310 acetylation. In addition, PDT promoted intramolecular disulfide formation and inactivation of tumor suppressor PTEN, thereby favoring Akt and p300 activation leading to iNOS upregulation. Importantly, deacetylase Sirt1 was down-regulated by PDT stress, consistent with the observed increase in p65-acK310 level, which fostered iNOS transcription. This study provides new mechanistic insights into how glioblastoma tumors can exploit iNOS/NO to not only resist PDT, but to attain a more aggressive survival phenotype.

Regulation of iNOS on Immune Cells and Its Role in Diseases

In recent years, there have been many studies on the function of nitric oxide synthase (NOS) in experimental animals and humans. This review analyzes and explores the relationship between inducible nitric oxide synthase (iNOS) and T cells, macrophages, and dendritic cell et al. differentiation using data based on laboratory research, highlighting recent NOS laboratory research. Our insights into research prospects and directions are also presented.

Impact of l-Arginine Metabolism on Immune Response and Anticancer Immunotherapy

The progression from neoplastic initiation to malignancy happens in part because of the failure of immune surveillance. Cancer cells successfully escape immune recognition and elimination and create an immune-suppressive microenvironment. A suppressive metabolic microenvironment may also contribute to ineffective T-cell function. Tumor progression is characterized by a complex network of interactions among different cell types that cooperatively exploit metabolic reprogramming. As we start to recognize that cancer cells use different metabolism processes than normal cells do, a better understanding of the functional mechanisms of the regulation and reprogramming of the metabolic landscape in cancer cells is crucial to successful immunotherapy strategies. However, the exact role of metabolism in T cells and in the tumor microenvironment is not known. One pathway that plays an important role in the regulation of immune cell reactivity is arginine metabolism, which has complex cellular functions. l-arginine and its downstream metabolites (e.g., ornithine and citrulline) could be essential to T-cell activation and thus modulate innate and adaptive immunity to further promote tumor survival and growth. Identifying metabolic targets that mediate immunosuppression and are fundamental to sustaining tumor growth is key to increasing the efficacy of immunotherapies.