Peroxynitrite in the tumor microenvironment changes the profile of antigens allowing escape from cancer immunotherapy

Macrophages, IL-10, and nitric oxide increase, induced by hyperglycemic conditions, impact the development of murine melanoma B16F10-Nex2

Epidemiological studies show a strong correlation between diabetes and the increased risk of developing different cancers, including melanoma. In the present study, we investigated the impact of a streptozotocin (STZ)-induced hyperglycemic environment on B16F10-Nex2 murine melanoma development. Hyperglycemic male C57Bl/6 mice showed increased subcutaneous tumor development, partially inhibited by metformin. Tumors showed increased infiltrating macrophages, and augmented IL-10 and nitric oxide (NO) concentrations. In vivo neutralization of IL-10, NO synthase inhibition, and depletion of macrophages reduced tumor development. STZ-treated TLR4 KO animals showed delayed tumor development; the transfer of hyperglycemic C57Bl/6 macrophages to TLR4 KO reversed this effect. Increased concentrations of IL-10 present in tumor homogenates of hyperglycemic mice induced a higher number of pre-angiogenic structures in vitro, and B16F10-Nex2 cells incubated with different glucose concentrations in vitro produced increased levels of IL-10. In summary, our findings show that a hyperglycemic environment stimulates murine melanoma B16F10-Nex2 primary tumor growth, and this effect is dependent on tumor cell stimulation, increased numbers of macrophages, and augmented IL-10 and NO concentrations. These findings show the involvement of tumor cells and other components of the tumor microenvironment in the development of subcutaneous melanoma under hyperglycemic conditions, defining novel targets for melanoma control in diabetic patients.

HMGB1 Expression Levels Correlate with Response to Immunotherapy in Non-Small Cell Lung Cancer

Purpose

High-mobility group box 1 protein (HMGB1) is subject to exportin 1 (XPO1)-dependent nuclear export, and it is involved in functions implicated in resistance to immunotherapy. We investigated whether HMGB1 mRNA expression was associated with response to immune checkpoint inhibitors (ICI) in non-small cell lung cancer (NSCLC).

Patients and Methods

RNA was isolated from pretreatment biopsies of patients with advanced NSCLC treated with ICI. Gene expression analysis of several genes, including HMGB1, was conducted using the NanoString Counter analysis system (PanCancer Immune Profiling Panel). Western blotting analysis and cell viability assays in EGFR and KRAS mutant cell lines were carried out. Evaluation of the antitumoral effect of ICI in combination with XPO1 blocker (selinexor) and trametinib was determined in a murine Lewis lung carcinoma model.

Results

HMGB1 mRNA levels in NSCLC patients treated with ICI correlated with progression-free survival (PFS) (median PFS 9.0 versus 18.0 months, P=0.008, hazard ratio=0.30 in high versus low HMGB1). After TNF-α stimulation, HMGB1 accumulates in the cytoplasm of PC9 cells, but this accumulation can be prevented by using selinexor or antiretroviral drugs. Erlotinib or osimertinib with selinexor in EGFR-mutant cells and trametinib plus selinexor in KRAS mutant abolish tumor cell proliferation. Selinexor with a PD-1 inhibitor with or without trametinib abrogates the tumor growth in the murine Lewis lung cancer model.

Conclusion

An in-depth exploration of the functions of HMGB1 mRNA and protein is expected to uncover new potential targets and provide a basis for treating metastatic NSCLC in combination with ICI.

Simultaneous Visualization and Depletion of Peroxynitrite by a Simple Aggregation-Induced Emission Nanoprobe for Preventing Breast Cancer Metastasis after Surgery

Inflammation has been confirmed to be closely related to the development of tumors, while peroxynitrite (ONOO-) is one of the most powerful oxidative pro-inflammatory factors. Although ONOO- can kill bacteria through oxidation, it will activate matrix metalloproteinases (MMPs), accelerate the degradation of the extracellular matrix (ECM), and subsequently lead to the activation and release of other tumor promotion factors existing in the ECM, promoting tumor metastasis and invasion. Herein, we report a simple aggregation-induced emission (AIE) nanoprobe (NP), TPE-4NMB, that can simultaneously visualize and deplete ONOO-. The probe can light up the endogenous and exogenous ONOO- in cells and selectively inhibit the proliferation and migration of 4T1 cells by inducing an intracellular redox homeostasis imbalance through ONOO- depletion. After being modified with DSPE-PEG2000, the TPE-4NMB NPs can be used to image ONOO- induced by various models in vivo; especially, it can monitor the dynamic changes of ONOO- level in the residual tumor after surgery, which can provide evidence for clarifying the association between surgery, ONOO-, and cancer metastasis. Excitingly, inhibited tumor volume growth and decreased counts of lung metastases were observed in the TPE-4NMB NPs group, which can be attributed to the downregulated expression of MMP-9 and transforming growth factor-β (TGF-β), increased cell apoptosis, and inhibited epithelial-mesenchymal transition (EMT) mediated by ONOO-. The results will provide new evidence for clarifying the relationship between surgery, ONOO-, and tumor metastasis and serve as a new intervention strategy for preventing tumor metastasis after tumor resection.

Redox Biomarkers and Matrix Remodeling Molecules in Ovarian Cancer

Ovarian cancer (OC) has emerged as the leading cause of death due to gynecological malignancies among women. Oxidative stress and metalloproteinases (MMPs) have been shown to influence signaling pathways and afflict the progression of carcinogenesis. Therefore, the assessment of matrix-remodeling and oxidative stress intensity can determine the degree of cellular injury and often the severity of redox-mediated chemoresistance. The study group comprised 27 patients with serous OC of which 18% were classified as Federation of Gynecology and Obstetrics (FIGO) stages I/II, while the rest were diagnosed grades III/IV. The control group comprised of 15 ovarian tissue samples. The results were compared with genetic data from The Cancer Genome Atlas. Nitro-oxidative stress, inflammation and apoptosis biomarkers were measured colorimetrically/fluorometrically or via real-time PCR in the primary ovarian tumor and healthy tissue. Stratification of patients according to FIGO stages revealed that high-grade carcinoma exhibited substantial alterations in redox balance, including the accumulation of protein glycoxidation and lipid peroxidation products. TCGA data demonstrated only limited prognostic usefulness of the studied genes. In conclusion, high-grade serous OC is associated with enhanced tissue oxidative/nitrosative stress and macromolecule damage that could not be overridden by the simultaneously augmented measures of antioxidant defense. Therefore, it can be assumed that tumor cells acquire adaptive mechanisms that enable them to withstand the potential toxic effects of elevated reactive oxygen species.

Myeloid-derived suppressor cells in cancer and cancer therapy

Anticancer agents continue to dominate the list of newly approved drugs, approximately half of which are immunotherapies. This trend illustrates the considerable promise of cancer treatments that modulate the immune system. However, the immune system is complex and dynamic, and can have both tumour-suppressive and tumour-promoting effects. Understanding the full range of immune modulation in cancer is crucial to identifying more effective treatment strategies. Myeloid-derived suppressor cells (MDSCs) are a heterogeneous population of myeloid cells that develop in association with chronic inflammation, which is a hallmark of cancer. Indeed, MDSCs accumulate in the tumour microenvironment, where they strongly inhibit anticancer functions of T cells and natural killer cells and exert a variety of other tumour-promoting effects. Emerging evidence indicates that MDSCs also contribute to resistance to cancer treatments, particularly immunotherapies. Conversely, treatment approaches designed to eliminate cancer cells can have important additional effects on MDSC function, which can be either positive or negative. In this Review, we discuss the interplay between MDSCs and various other cell types found in tumours as well as the mechanisms by which MDSCs promote tumour progression. We also discuss the relevance and implications of MDSCs for cancer therapy.

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.

Breaking the mold: Overcoming resistance to immune checkpoint inhibitors

Immune checkpoint blockade-based therapies are effective against a sorts of cancers. However, drug resistance is a problem that cannot be ignored. This review intends to elucidate the mechanisms underlying drug tolerance induced by PD-1/PD-L1 inhibitors, as well as to outline proposed mechanism-based combination therapies and small molecule drugs that target intrinsic immunity and immune checkpoints. According to the differences of patients and types of cancer, the optimization of individualized combination therapy will help to enhance PD-1/PD-L1-mediated immunoregulation, reduce chemotherapy resistance, and provide new ideas for chemotherapy-resistant cancer.

Multiscale imaging of peroxynitrite in gliomas with a blood-brain barrier permeable probe reveals its potential as a biomarker and target for glioma treatment

Cancer development is driven by diverse processes, and metabolic alterations are among the primary characteristics. Multiscale imaging of aberrant metabolites in cancer is critical to understand the pathology and identify new targets for treatment. While peroxynitrite (ONOO^-) is reported being enriched in some tumors and plays important tumorigenic roles, whether it is upregulated in gliomas remains unexplored. To determine the levels and roles of ONOO^- in gliomas, efficient tools especially those with desirable blood-brain barrier (BBB) permeability and can realize the in situ imaging of ONOO^- in multiscale glioma-related samples are indispensable. Herein, we proposed a strategy of physicochemical property-guided probe design, which resulted in the development of a fluorogenic probe NOSTracker for smartly tracking ONOO^-. The probe showed sufficient BBB permeability. ONOO^- triggered oxidation of its arylboronate group was automatically followed by a self-immolative cleavage of a fluorescence-masking group, liberating its fluorescence signal. The probe was not only highly sensitive and selective towards ONOO^-, but its fluorescence favored desirable stability in various complex biological milieus. Guaranteed by these properties, multiscale imaging of ONOO^- was realized in vitro in patient-derived primary glioma cells, ex vivo in clinical glioma slices, and in vivo in the glioma of live mice. The results showed the upregulation of ONOO^- in gliomas. Furthermore, a specific ONOO^- scavenger uric acid (UA) was pharmaceutically used to downregulate ONOO^- in glioma cell lines, and an anti-proliferative effect was observed. These results taken together imply the potential of ONOO^- as a biomarker and target for glioma treatment, and propose NOSTracker as a reliable tool to further explore the role of ONOO^- in glioma development.

Fluorescent Detection of Peroxynitrite Produced by Myeloid-Derived Suppressor Cells in Cancer and Inhibition by Dasatinib

Myeloid-derived suppressor cells (MDSCs) are immature myeloid cells that expand dramatically in many cancer patients. This expansion contributes to immunosuppression in cancer and reduces the efficacy of immune-based cancer therapies. One mechanism of immunosuppression mediated by MDSCs involves production of the reactive nitrogen species peroxynitrite (PNT), where this strong oxidant inactivates immune effector cells through destructive nitration of tyrosine residues in immune signal transduction pathways. As an alternative to analysis of nitrotyrosines indirectly generated by PNT, we used an endoplasmic reticulum (ER)-targeted fluorescent sensor termed PS3 that allows direct detection of PNT produced by MDSCs. When the MDSC-like cell line MSC2 and primary MDSCs from mice and humans were treated with PS3 and antibody-opsonized TentaGel microspheres, phagocytosis of these beads led to production of PNT and generation of a highly fluorescent product. Using this method, we show that splenocytes from a EMT6 mouse model of cancer, but not normal control mice, produce high levels of PNT due to elevated numbers of granulocytic (PMN) MDSCs. Similarly, peripheral blood mononuclear cells (PBMCs) isolated from blood of human melanoma patients produced substantially higher levels of PNT than healthy human volunteers, coincident with higher peripheral MDSC levels. The kinase inhibitor dasatinib was found to potently block the production of PNT both by inhibiting phagocytosis in vitro and by reducing the number of granulocytic MDSCs in mice in vivo, providing a chemical tool to modulate the production of this reactive nitrogen species (RNS) in the tumor microenvironment.

Neoantigens: promising targets for cancer therapy

Recent advances in neoantigen research have accelerated the development and regulatory approval of tumor immunotherapies, including cancer vaccines, adoptive cell therapy and antibody-based therapies, especially for solid tumors. Neoantigens are newly formed antigens generated by tumor cells as a result of various tumor-specific alterations, such as genomic mutation, dysregulated RNA splicing, disordered post-translational modification, and integrated viral open reading frames. Neoantigens are recognized as non-self and trigger an immune response that is not subject to central and peripheral tolerance. The quick identification and prediction of tumor-specific neoantigens have been made possible by the advanced development of next-generation sequencing and bioinformatic technologies. Compared to tumor-associated antigens, the highly immunogenic and tumor-specific neoantigens provide emerging targets for personalized cancer immunotherapies, and serve as prospective predictors for tumor survival prognosis and immune checkpoint blockade responses. The development of cancer therapies will be aided by understanding the mechanism underlying neoantigen-induced anti-tumor immune response and by streamlining the process of neoantigen-based immunotherapies. This review provides an overview on the identification and characterization of neoantigens and outlines the clinical applications of prospective immunotherapeutic strategies based on neoantigens. We also explore their current status, inherent challenges, and clinical translation potential.

Peroxynitrite promotes immune evasion by reducing tumor antigenicity

A study by Tcyganov et al.¹ demonstrates that peroxynitrite, an oxidant abundant in the tumor microenvironment, changes the repertoire of MHC class I peptides presented by tumors and limits immune recognition. Peroxynitrite inhibition in combination with immune checkpoint blockade enhances efficacy preclinically.