Nrf2-deficiency creates a responsive microenvironment for metastasis to the lung

Peiminine triggers ferroptosis to inhibit breast cancer growth through triggering Nrf2 signaling

BACKGROUND

Peiminine (PMI) is an active alkaloid sourced from Fritillaria thunbergii, which has been shown to suppress the development of a variety of tumors. Whereas, the roles and precise mechanism of PMI in breast cancer (BC) development remain not been clarified.

METHODS

The cytotoxic effect of PMI on MCF-10A and BC cell lines (MCF-7 and BT-549) were assessed by MTT and LDH release assay. Cell proliferation was evaluated by EdU staining. Levels of Malondialdehyde (MDA), reactive oxygen species (ROS), glutathione (GSH) activity and iron assay were measured by Enzyme linked immunosorbent assay (ELISA) kits, respectively. Transmission Electron Microscope was performed to observe mitochondrial morphological structure. Immunofluorescence, immunohistochemistry, and western blot were conducted to examine protein levels, respectively. Xenograft model was used to confirm cellular findings.

RESULTS

PMI treatment reduced the viability and enhanced LDH level of MCF-7 and BT-549 cells in a time- and concentration-dependent manner, and further suppressed cell proliferation in vitro and tumor growth in vivo. Subsequently, PMI administration resulted in significant increases of ROS, MDA and iron levels, reduction of GSH activity as well as mitochondrial shrinkage and GPX4 reduction, while all these phenomena could be rescued by ferrostatin-1. Mechanistically, PMI treatment led to promoted Nrf2 expression and its nuclear translocation, as well as it's downstream protein HO-1 and NQO1 expressions. Notably, ML-385, a Nrf2 specific inhibitor, greatly reversed the anti-tumor effects and pro-ferroptosis role of PMI in BC cells.

CONCLUSION

Taking these finding together, PMI could stimulate ferroptosis to inhibit BC tumor growth by activating Nrf2-HO-1 signaling pathway.

The pleiotropic functions of reactive oxygen species in cancer

Cellular redox homeostasis is an essential, dynamic process that ensures the balance between reducing and oxidizing reactions within cells and thus has implications across all areas of biology. Changes in levels of reactive oxygen species can disrupt redox homeostasis, leading to oxidative or reductive stress that contributes to the pathogenesis of many malignancies, including cancer. From transformation and tumor initiation to metastatic dissemination, increasing reactive oxygen species in cancer cells can paradoxically promote or suppress the tumorigenic process, depending on the extent of redox stress, its spatiotemporal characteristics and the tumor microenvironment. Here we review how redox regulation influences tumorigenesis, highlighting therapeutic opportunities enabled by redox-related alterations in cancer cells.

Regulation of antioxidants in cancer

Scientists in this field often joke, "If you don't have a mechanism, say it's ROS." Seemingly connected to every biological process ever described, reactive oxygen species (ROS) have numerous pleiotropic roles in physiology and disease. In some contexts, ROS act as secondary messengers, controlling a variety of signaling cascades. In other scenarios, they initiate damage to macromolecules. Finally, in their worst form, ROS are deadly to cells and surrounding tissues. A set of molecules with detoxifying abilities, termed antioxidants, is the direct counterpart to ROS. Notably, antioxidants exist in the public domain, touted as a "cure-all" for diseases. Research has disproved many of these claims and, in some cases, shown the opposite. Of all the diseases, cancer stands out in its paradoxical relationship with antioxidants. Although the field has made numerous strides in understanding the roles of antioxidants in cancer, many questions remain.

Exploring the multifaceted role of NRF2 in brain physiology and cancer: A comprehensive review

Chronic oxidative stress plays a critical role in the development of brain malignancies due to the high rate of brain oxygen utilization and concomitant production of reactive oxygen species. The nuclear factor-erythroid-2-related factor 2 (NRF2), a master regulator of antioxidant signaling, is a key factor in regulating brain physiology and the development of age-related neurodegenerative diseases. Also, NRF2 is known to exert a protective antioxidant effect against the onset of oxidative stress-induced diseases, including cancer, along with its pro-oncogenic activities through regulating various signaling pathways and downstream target genes. In glioblastoma (GB), grade 4 glioma, tumor resistance, and recurrence are caused by the glioblastoma stem cell population constituting a small bulk of the tumor core. The persistence and self-renewal capacity of these cell populations is enhanced by NRF2 expression in GB tissues. This review outlines NRF2's dual involvement in cancer and highlights its regulatory role in human brain physiology and diseases, in addition to the development of primary brain tumors and therapeutic potential, with a focus on GB.

The Involvement of Peroxiporins and Antioxidant Transcription Factors in Breast Cancer Therapy Resistance

Breast cancer is still the leading cause of death in women of all ages. The reason for this is therapy resistance, which leads to the progression of the disease and the formation of metastases. Multidrug resistance (MDR) is a multifactorial process that leads to therapy failure. MDR involves multiple processes and many signaling pathways that support each other, making it difficult to overcome once established. Here, we discuss cellular-oxidative-stress-modulating factors focusing on transcription factors NRF2, FOXO family, and peroxiporins, as well as their possible contribution to MDR. This is significant because oxidative stress is a consequence of radiotherapy, chemotherapy, and immunotherapy, and the activation of detoxification pathways could modulate the cellular response to therapy and could support MDR. These proteins are not directly responsible for MDR, but they support the survival of cancer cells under stress conditions.

Hemorrhage-activated NRF2 in tumor-associated macrophages drives cancer growth, invasion, and immunotherapy resistance

Microscopic hemorrhage is a common aspect of cancers, yet its potential role as an independent factor influencing both cancer progression and therapeutic response is largely ignored. Recognizing the essential function of macrophages in red blood cell disposal, we explored a pathway that connects intratumoral hemorrhage with the formation of cancer-promoting tumor-associated macrophages (TAMs). Using spatial transcriptomics, we found that NRF2-activated myeloid cells possessing characteristics of procancerous TAMs tend to cluster in perinecrotic hemorrhagic tumor regions. These cells resembled antiinflammatory erythrophagocytic macrophages. We identified heme, a red blood cell metabolite, as a pivotal microenvironmental factor steering macrophages toward protumorigenic activities. Single-cell RNA-Seq and functional assays of TAMs in 3D cell culture spheroids revealed how elevated intracellular heme signals via the transcription factor NRF2 to induce cancer-promoting TAMs. These TAMs stabilized epithelial-mesenchymal transition, enhancing cancer invasiveness and metastatic potential. Additionally, NRF2-activated macrophages exhibited resistance to reprogramming by IFN-γ and anti-CD40 antibodies, reducing their tumoricidal capacity. Furthermore, MC38 colon adenocarcinoma-bearing mice with NRF2 constitutively activated in leukocytes were resistant to anti-CD40 immunotherapy. Overall, our findings emphasize hemorrhage-activated NRF2 in TAMs as a driver of cancer progression, suggesting that targeting this pathway could offer new strategies to enhance cancer immunity and overcome therapy resistance.

An Update on Potential Molecular Biomarkers of Dietary Phytochemicals Targeting Lung Cancer Interception and Prevention

Since ancient times, dietary phytochemicals are known for their medicinal properties. They are broadly classified into polyphenols, terpenoids, alkaloids, phytosterols, and organosulfur compounds. Currently, there is considerable interest in their potential health effects against various diseases, including lung cancer. Lung cancer is the leading cause of cancer deaths with an average of five-year survival rate of lung cancer patients limited to just 14%. Identifying potential early molecular biomarkers of pre-malignant lung cancer cells may provide a strong basis to develop early cancer detection and interception methods. In this review, we will discuss molecular changes, including genetic alterations, inflammation, signal transduction pathways, redox imbalance, epigenetic and proteomic signatures associated with initiation and progression of lung carcinoma. We will also highlight molecular targets of phytochemicals during lung cancer development. These targets mainly consist of cellular signaling pathways, epigenetic regulators and metabolic reprogramming. With growing interest in natural products research, translation of these compounds into new cancer prevention approaches to medical care will be urgently needed. In this context, we will also discuss the overall pharmacokinetic challenges of phytochemicals in translating to humans. Lastly, we will discuss clinical trials of phytochemicals in lung cancer patients.

Insight into Nrf2: a bibliometric and visual analysis from 2000 to 2022

Background: Nrf2 plays a pivotal role in governing the antioxidant defense system, triggering the transcription of diverse genes involved in cellular protection. Its role in mitigating oxidative damage and modulating inflammatory processes has made Nrf2 an attractive target for therapeutic interventions. Despite the growing interest in Nrf2 research, a bibliometric analysis is relatively rare. This study aimed to clarify Nrf2's role in multiple diseases, identify emerging trends and hotspots using bibliometric analysis, and provide valuable insights and potential directions for future therapeutic interventions. Methods: The Science Citation Index of Web of Science Core library from 2000 to 2022 was searched on 22 October 2022. Use Microsoft Excel, CiteSpace, Bibliometrix, and VOS viewers for data collection and visualization of research focus and trends. Results: A vast collection of 22,040 research studies on Nrf2 published between 2000 and 2022 were identified. Nrf2 research has seen significant growth globally from 2000 to 2022. China leaded in publication numbers (9,623, 43.66%), while the United States dominated in citation frequency with 261,776 citations. China Medical University was the most productive institutions (459, 2.08%). Masayuki Yamamoto topped in publications (307), while Itoh K. ranked first in citations with 3669. Free Radical Biology and Medicine was the journal with the most studies and citations on Nrf2 (613, 29,687 citations). The analysis of keyword clustering enhanced the categorization of topics and can be summarized as oxidative stress, cancer, disorders in glycolipid metabolism, inflammation, and neurological conditions. Conclusion: China and the United States are the pioneers in Nrf2 research. Recently, there has been a comprehensive exploration of Nrf2 involving both experimental and clinical aspects, as well as mechanisms and therapeutic applications. Investigating novel molecular mechanisms, including NF-κB, Ho1, and Keap1, and developing enhanced, targeted Nrf2 activators or inhibitors to uncover the interplay among cancer, glycolipid metabolic disorder, inflammation, and neurological disorders will be upcoming trends and hotspots.

Function of reactive oxygen species in myeloid-derived suppressor cells

Myeloid-derived suppressor cells (MDSCs) are a heterogeneous myeloid cell population and serve as a vital contributor to the tumor microenvironment. Reactive oxygen species (ROS) are byproducts of aerobic respiration and are involved in regulating normal biological activities and disease progression. MDSCs can produce ROS to fulfill their immunosuppressive activity and eliminate excessive ROS to survive comfily through the redox system. This review focuses on how MDSCs survive and function in high levels of ROS and summarizes immunotherapy targeting ROS in MDSCs. The distinctive role of ROS in MDSCs will inspire us to widely apply the blocked oxidative stress strategy in targeting MDSC therapy to future clinical therapeutics.

The mechanistic insights of the antioxidant Keap1-Nrf2 pathway in oncogenesis: a deadly scenario

The Nuclear factor erythroid 2-related factor 2 (Nrf2) protein has garnered significant interest due to its crucial function in safeguarding cells and tissues. The Nrf2 protein is crucial in preserving tissue integrity by safeguarding cells against metabolic, xenobiotic and oxidative stress. Due to its various functions, Nrf2 is a potential pharmacological target for reducing the incidence of diseases such as cancer. However, mutations in Keap1-Nrf2 are not consistently favored in all types of cancer. Instead, they seem to interact with specific driver mutations of tumors and their respective tissue origins. The Kelch-like ECH-associated protein 1 (Keap1)-Nrf2 pathway mutations are a powerful cancer adaptation that utilizes inherent cytoprotective pathways, encompassing nutrient metabolism and ROS regulation. The augmentation of Nrf2 activity elicits significant alterations in the characteristics of neoplastic cells, such as resistance to radiotherapy and chemotherapy, safeguarding against apoptosis, heightened invasiveness, hindered senescence, impaired autophagy and increased angiogenesis. The altered activity of Nrf2 can arise from diverse genetic and epigenetic modifications that instantly impact Nrf2 regulation. The present study aims to showcase the correlation between the Keap1-Nrf2 pathway and the progression of cancers, emphasizing genetic mutations, metabolic processes, immune regulation, and potential therapeutic strategies. This article delves into the intricacies of Nrf2 pathway anomalies in cancer, the potential ramifications of uncontrolled Nrf2 activity, and therapeutic interventions to modulate the Keap1-Nrf2 pathway.

Distinct Nrf2 Signaling Thresholds Mediate Lung Tumor Initiation and Progression

Mutations in the KEAP1-NRF2 (Kelch-like ECH-associated protein 1-nuclear factor-erythroid 2 p45-related factor 2) pathway occur in up to a third of non-small cell lung cancer (NSCLC) cases and often confer resistance to therapy and poor outcomes. Here, we developed murine alleles of the KEAP1 and NRF2 mutations found in human NSCLC and comprehensively interrogated their impact on tumor initiation and progression. Chronic NRF2 stabilization by Keap1 or Nrf2 mutation was not sufficient to induce tumorigenesis, even in the absence of tumor suppressors, p53 or LKB1. When combined with KrasG12D/+, constitutive NRF2 activation promoted lung tumor initiation and early progression of hyperplasia to low-grade tumors but impaired their progression to advanced-grade tumors, which was reversed by NRF2 deletion. Finally, NRF2 overexpression in KEAP1 mutant human NSCLC cell lines was detrimental to cell proliferation, viability, and anchorage-independent colony formation. Collectively, these results establish the context-dependence and activity threshold for NRF2 during the lung tumorigenic process.

SIGNIFICANCE

Stabilization of the transcription factor NRF2 promotes oncogene-driven tumor initiation but blocks tumor progression, indicating distinct, threshold-dependent effects of the KEAP1/NRF2 pathway in different stages of lung tumorigenesis.

The KEAP1-NRF2 pathway: Targets for therapy and role in cancer

The KEAP1-NRF2 pathway is the key regulator of cellular defense against both extrinsic and intrinsic oxidative and electrophilic stimuli. Since its discovery in the 1990s, its seminal role in various disease pathologies has become well appreciated, motivating research to elucidate the intricacies of NRF2 signaling and its downstream effects to identify novel targets for therapy. In this graphical review, we present an updated overview of the KEAP1-NRF2 signaling, focusing on the progress made within the past ten years. Specifically, we highlight the advances made in understanding the mechanism of activation of NRF2, resulting in novel discoveries in its therapeutic targeting. Furthermore, we will summarize new findings in the rapidly expanding field of NRF2 in cancer, with important implications for its diagnostics and treatment.

Emerging Role of NRF2 Signaling in Cancer Stem Cell Phenotype

Cancer stem cells (CSCs) are a small population of tumor cells characterized by self-renewal and differentiation capacity. CSCs are currently postulated as the driving force that induces intra-tumor heterogeneity leading to tumor initiation, metastasis, and eventually tumor relapse. Notably, CSCs are inherently resistant to environmental stress, chemotherapy, and radiotherapy due to high levels of antioxidant systems and drug efflux transporters. In this context, a therapeutic strategy targeting the CSC-specific pathway holds a promising cure for cancer. NRF2 (nuclear factor erythroid 2-like 2; NFE2L2) is a master transcription factor that regulates an array of genes involved in the detoxification of reactive oxygen species/electrophiles. Accumulating evidence suggests that persistent NRF2 activation, observed in multiple types of cancer, supports tumor growth, aggressive malignancy, and therapy resistance. Herein, we describe the core properties of CSCs, focusing on treatment resistance, and review the evidence that demonstrates the roles of NRF2 signaling in conferring unique properties of CSCs and the associated signaling pathways.

Nrf2 in TIME: The Emerging Role of Nuclear Factor Erythroid 2-Related Factor 2 in the Tumor Immune Microenvironment

Nuclear factor erythroid 2-related factor 2 (Nrf2) mediates the cellular antioxidant response, allowing adaptation and survival under conditions of oxidative, electrophilic and inflammatory stress, and has a role in metabolism, inflammation and immunity. Activation of Nrf2 provides broad and long-lasting cytoprotection, and is often hijacked by cancer cells, allowing their survival under unfavorable conditions. Moreover, Nrf2 activation in established human tumors is associated with resistance to chemo-, radio-, and immunotherapies. In addition to cancer cells, Nrf2 activation can also occur in tumor-associated macrophages (TAMs) and facilitate an anti-inflammatory, immunosuppressive tumor immune microenvironment (TIME). Several cancer cell-derived metabolites, such as itaconate, L-kynurenine, lactic acid and hyaluronic acid, play an important role in modulating the TIME and tumor-TAMs crosstalk, and have been shown to activate Nrf2. The effects of Nrf2 in TIME are context-depended, and involve multiple mechanisms, including suppression of pro-inflammatory cytokines, increased expression of programmed cell death ligand 1 (PD-L1), macrophage colony-stimulating factor (M-CSF) and kynureninase, accelerated catabolism of cytotoxic labile heme, and facilitating the metabolic adaptation of TAMs. This understanding presents both challenges and opportunities for strategic targeting of Nrf2 in cancer.

Molecular Basis of the KEAP1-NRF2 Signaling Pathway

Transcription factor NRF2 (NF-E2-related factor 2) is a master regulator of cellular responses against environmental stresses. NRF2 induces expression of detoxification and antioxidant enzymes and suppresses inductions of pro-inflammatory cytokine genes. KEAP1 (Kelch-like ECH-associated protein 1) is an adaptor subunit of CULLIN 3 (CUL3)-based E3 ubiquitin ligase. KEAP1 regulates the activity of NRF2 and acts as a sensor for oxidative and electrophilic stresses. NRF2 has been found to be activated in many types of cancers with poor prognosis. Therapeutic strategies to control NRF2-overeactivated cancers have been considered not only by targeting cancer cells with NRF2 inhibitors or NRF2 synthetic lethal chemicals, but also by targeting host defense with NRF2 inducers. Understanding precise molecular mechanisms how the KEAP1-NRF2 system senses and regulates the cellular response is critical to overcome intractable NRF2-activated cancers.

Involvement of redox signalling in tumour cell dormancy and metastasis

Decades of research on oncogene-driven carcinogenesis and gene-expression regulatory networks only started to unveil the complexity of tumour cellular and molecular biology. This knowledge has been successfully implemented in the clinical practice to treat primary tumours. In contrast, much less progress has been made in the development of new therapies against metastasis, which are the main cause of cancer-related deaths. More recently, the role of epigenetic and microenviromental factors has been shown to play a key role in tumour progression. Free radicals are known to communicate the intracellular and extracellular compartments, acting as second messengers and exerting a decisive modulatory effect on tumour cell signalling. Depending on the cellular and molecular context, as well as the intracellular concentration of free radicals and the activation status of the antioxidant system of the cell, the signalling equilibrium can be tilted either towards tumour cell survival and progression or cell death. In this regard, recent advances in tumour cell biology and metastasis indicate that redox signalling is at the base of many cell-intrinsic and microenvironmental mechanisms that control disseminated tumour cell fate and metastasis. In this manuscript, we will review the current knowledge about redox signalling along the different phases of the metastatic cascade, including tumour cell dormancy, making emphasis on metabolism and the establishment of supportive microenvironmental connections, from a redox perspective.

The synergistic effects of PRDX5 and Nrf2 on lung cancer progression and drug resistance under oxidative stress in the zebrafish models

Previous studies have shown that PRDX5 and Nrf2 are antioxidant proteins related to abnormal reactive oxidative species (ROS). PRDX5 and Nrf2 play a critical role in the progression of inflammations and tumors. The combination of PRDX5 and Nrf2 was examined by Co-immunoprecipitation, western blotting and Immunohistochemistry. H2O2 was applied to affect the production of ROS and induced multi-resistant protein 1 (MRP1) expression in NSCLC cells. The zebrafish models mainly investigated the synergistic effects of PRDX5 and Nrf2 on lung cancer drug resistance under oxidative stress. We showed that PRDX5 and Nrf2 form a complex and significantly increase the NSCLC tissues compared to adjacent tissues. The oxidative stress improved the combination of PRDX5 and Nrf2. We demonstrated that the synergy between PRDX5 and Nrf2 is positively related to the proliferation and drug resistance of NSCLC cells in the zebrafish models. In conclusion, our data indicated that PRDX5 could bind to Nrf2 and has a synergistic effect with Nrf2. Meanwhile, in the zebrafish models, PRDX5 and Nrf2 have significant regulatory impacts on lung cancer progression and drug resistance activities under oxidative stress.

Role of STAT3 and NRF2 in Tumors: Potential Targets for Antitumor Therapy

Signal transducer and activator of transcription 3 (STAT3) and nuclear factor erythroid-derived 2-like 2 (NRF2, also known as NFE2L2), are two of the most complicated transcription regulators, which participate in a variety of physiological processes. Numerous studies have shown that they are overactivated in multiple types of tumors. Interestingly, STAT3 and NRF2 can also interact with each other to regulate tumor progression. Hence, these two important transcription factors are considered key targets for developing a new class of antitumor drugs. This review summarizes the pivotal roles of the two transcription regulators and their interactions in the tumor microenvironment to identify potential antitumor drug targets and, ultimately, improve patients' health and survival.

Spatial Analysis of NQO1 in Non-Small Cell Lung Cancer Shows Its Expression Is Independent of NRF1 and NRF2 in the Tumor Microenvironment

Nuclear factor erythroid 2-related factor 1 (NFE2L1, NRF1) and nuclear factor erythroid 2-related factor 2 (NFE2L2, NRF2) are distinct oxidative stress response transcription factors, both of which have been shown to perform cytoprotective functions, modulating cell stress response and homeostasis. NAD(P)H:quinone oxidoreductase (NQO1) is a mutual downstream antioxidant gene target that catalyzes the two-electron reduction of an array of substrates, protecting against reactive oxygen species (ROS) generation. NQO1 is upregulated in non-small cell lung cancer (NSCLC) and is proposed as a predictive biomarker and therapeutic target. Antioxidant protein expression of immune cells within the NSCLC tumor microenvironment (TME) remains undetermined and may affect immune cell effector functions and survival outcomes. Multiplex immunofluorescence was performed to examine the co-localization of NQO1, NRF1 and NRF2 within the tumor and TME of 162 chemotherapy-naïve, early-stage NSCLC patients treated by primary surgical resection. This study demonstrates that NQO1 protein expression is high in normal, tumor-adjacent tissue and that NQO1 expression varies depending on the cell type. Inter and intra-patient heterogenous NQO1 expression was observed in lung cancer. Co-expression analysis showed NQO1 is independent of NRF1 and NRF2 in tumors. Density-based co-expression analysis demonstrated NRF1 and NRF2 double-positive expression in cancer cells is associated with improved overall survival.

Signaling pathways and targeted therapies in lung squamous cell carcinoma: mechanisms and clinical trials

Lung cancer is the leading cause of cancer-related death across the world. Unlike lung adenocarcinoma, patients with lung squamous cell carcinoma (LSCC) have not benefitted from targeted therapies. Although immunotherapy has significantly improved cancer patients' outcomes, the relatively low response rate and severe adverse events hinder the clinical application of this promising treatment in LSCC. Therefore, it is of vital importance to have a better understanding of the mechanisms underlying the pathogenesis of LSCC as well as the inner connection among different signaling pathways, which will surely provide opportunities for more effective therapeutic interventions for LSCC. In this review, new insights were given about classical signaling pathways which have been proved in other cancer types but not in LSCC, including PI3K signaling pathway, VEGF/VEGFR signaling, and CDK4/6 pathway. Other signaling pathways which may have therapeutic potentials in LSCC were also discussed, including the FGFR1 pathway, EGFR pathway, and KEAP1/NRF2 pathway. Next, chromosome 3q, which harbors two key squamous differentiation markers SOX2 and TP63 is discussed as well as its related potential therapeutic targets. We also provided some progress of LSCC in epigenetic therapies and immune checkpoints blockade (ICB) therapies. Subsequently, we outlined some combination strategies of ICB therapies and other targeted therapies. Finally, prospects and challenges were given related to the exploration and application of novel therapeutic strategies for LSCC.

An Overview of NRF2-Activating Compounds Bearing α,β-Unsaturated Moiety and Their Antioxidant Effects

The surge of scientific interest in the discovery of Nuclear Factor Erythroid 2 (NFE2)-Related Factor 2 (NRF2)-activating molecules underscores the importance of NRF2 as a therapeutic target especially for oxidative stress. The chemical reactivity and biological activities of several bioactive compounds have been linked to the presence of α,β-unsaturated structural systems. The α,β-unsaturated carbonyl, sulfonyl and sulfinyl functional groups are reportedly the major α,β-unsaturated moieties involved in the activation of the NRF2 signaling pathway. The carbonyl, sulfonyl and sulfinyl groups are generally electron-withdrawing groups, and the presence of the α,β-unsaturated structure qualifies them as suitable electrophiles for Michael addition reaction with nucleophilic thiols of cysteine residues within the proximal negative regulator of NRF2, Kelch-like ECH-associated protein 1 (KEAP1). The physicochemical property such as good lipophilicity of these moieties is also an advantage because it ensures solubility and membrane permeability required for the activation of the cytosolic NRF2/KEAP1 system. This review provides an overview of the reaction mechanism of α,β-unsaturated moiety-bearing compounds with the NRF2/KEAP1 complex, their pharmacological properties, structural activity-relationship and their effect on antioxidant and anti-inflammatory responses. As the first of its kind, this review article offers collective and comprehensive information on NRF2-activators containing α,β-unsaturated moiety with the aim of broadening their therapeutic prospects in a wide range of oxidative stress-related diseases.

The molecular biology and therapeutic potential of Nrf2 in leukemia

NF-E2-related factor 2 (Nrf2) transcription factor has contradictory roles in cancer, which can act as a tumor suppressor or a proto-oncogene in different cell conditions (depending on the cell type and the conditions of the cell environment). Nrf2 pathway regulates several cellular processes, including signaling, energy metabolism, autophagy, inflammation, redox homeostasis, and antioxidant regulation. As a result, it plays a crucial role in cell survival. Conversely, Nrf2 protects cancerous cells from apoptosis and increases proliferation, angiogenesis, and metastasis. It promotes resistance to chemotherapy and radiotherapy in various solid tumors and hematological malignancies, so we want to elucidate the role of Nrf2 in cancer and the positive point of its targeting. Also, in the past few years, many studies have shown that Nrf2 protects cancer cells, especially leukemic cells, from the effects of chemotherapeutic drugs. The present paper summarizes these studies to scrutinize whether targeting Nrf2 combined with chemotherapy would be a therapeutic approach for leukemia treatment. Also, we discussed how Nrf2 and NF-κB work together to control the cellular redox pathway. The role of these two factors in inflammation (antagonistic) and leukemia (synergistic) is also summarized.

Genetic, Metabolic and Immunological Features of Cancers with NRF2 Addiction

Nuclear factor erythroid-derived 2-like 2 (NRF2) is a master transcription factor that coordinately regulates the expression of many cytoprotective genes and plays a central role in defense mechanisms against oxidative and electrophilic insults. Although increased NRF2 activity is principally beneficial for our health, NRF2 activation in cancer cells is detrimental. Many human cancers exhibit persistent NRF2 activation and such cancer cells rely on NRF2 for most of their malignant characteristics, such as therapeutic resistance and aggressive tumorigenesis, and thus fall into NRF2 addiction. The persistent activation of NRF2 confers great advantages on cancer cells, whereas it is not tolerated by normal cells, suggesting that certain requirements are necessary for a cell to exploit NRF2 and evolve into malignant a cancer cell. In this review, recent reports and data on the genetic, metabolic and immunological features of NRF2-activated cancer cells are summarized, and prerequisites for NRF2 addiction in cancer cells and their therapeutic applications are discussed.

Halofuginone micelle nanoparticles eradicate Nrf2-activated lung adenocarcinoma without systemic toxicity

The Keap1-Nrf2 system is the master regulator of the cellular response against oxidative and xenobiotic stresses. Constitutive activation of Nrf2 is frequently observed in various types of cancers. Nrf2 hyperactivation induces metabolic reprogramming in cancer cells, which supports the increased energy demand required for rapid proliferation and confers high-level resistance against anticancer radio/chemotherapy. Hence, Nrf2 inhibition has emerged as an attractive therapeutic strategy to counter such acquired resistance in Nrf2-activated tumors. We previously identified Halofuginone (HF) as a promising Nrf2 inhibitor. In this study, we pursued preclinical characterization of HF and found that while HF markedly reduced the viability of cancer cells, it also caused severe hematopoietic and immune cell suppression in a dose-dependent manner. Hence, to overcome this toxicity, we decided to employ a nanomedicine approach to HF. We found that encapsulation of HF into a polymeric micelle (HF micelle; HFm) largely relieved the systemic toxicity exhibited by free HF while maintaining the tumor-suppressive properties of HF. LC-MS/MS analysis revealed that the reduction in the magnitude of adverse effects was the result of the ability to release HF from the HFm core in a slow and sustained manner. These results thus support the contention that HFm will potentially counteract Nrf2-activated cancers in the clinical settings.

Genomic landscape of chemical-induced lung tumors under Nrf2 different expression levels

The transcription factor Nrf2 plays a crucial role in the anti-oxidative stress response, protection of DNA from injury, and DNA repair mechanisms. Nrf2 activity reduces cancer initiation, but how Nrf2 affects whole-genome alterations upon carcinogenic stimulus remains unexplored. Although recent genome-wide analysis using next-generation sequencing revealed landscapes of nucleotide mutations and copy number alterations in various human cancers, genomic changes in murine cancer models have not been thoroughly examined. We elucidated the relationship between Nrf2 expression levels and whole exon mutation patterns using an ethyl-carbamate (urethane)-induced lung carcinogenesis model employing Nrf2-deficient and Keap1-kd mice, the latter of which express high levels of Nrf2. Exome analysis demonstrated that single nucleotide and trinucleotide mutation patterns and the Kras mutational signature differed significantly and were dependent on the expression level of Nrf2. The Nrf2-deficient tumors exhibited fewer copy number alterations relative to the Nrf2-wt and Keap1-kd tumors. The observed trend in genomic alterations likely prevented the Nrf2-deficient tumors from progressing into malignancy. For the first time, we present whole-exome sequencing results for chemically-induced lung tumors in the Nrf2 gain or loss of function mouse models. Our results demonstrate that different Nrf2 expression levels lead to distinct gene mutation patterns that underly different oncogenic mechanisms in each tumor genotype.

Immunometabolism of Myeloid-Derived Suppressor Cells: Implications for Mycobacterium tuberculosis Infection and Insights from Tumor Biology

The field of immunometabolism seeks to decipher the complex interplay between the immune system and the associated metabolic pathways. The role of small molecules that can target specific metabolic pathways and subsequently alter the immune landscape provides a desirable platform for new therapeutic interventions. Immunotherapeutic targeting of suppressive cell populations, such as myeloid-derived suppressor cells (MDSC), by small molecules has shown promise in pathologies such as cancer and support testing of similar host-directed therapeutic approaches in MDSC-inducing conditions such as tuberculosis (TB). MDSC exhibit a remarkable ability to suppress T-cell responses in those with TB disease. In tumors, MDSC exhibit considerable plasticity and can undergo metabolic reprogramming from glycolysis to fatty acid oxidation (FAO) and oxidative phosphorylation (OXPHOS) to facilitate their immunosuppressive functions. In this review we look at the role of MDSC during M. tb infection and how their metabolic reprogramming aids in the exacerbation of active disease and highlight the possible MDSC-targeted metabolic pathways utilized during M. tb infection, suggesting ways to manipulate these cells in search of novel insights for anti-TB therapies.

Multifaceted Roles of the KEAP1–NRF2 System in Cancer and Inflammatory Disease Milieu

In a multicellular environment, many different types of cells interact with each other. The KEAP1–NRF2 system defends against electrophilic and oxidative stresses in various types of cells. However, the KEAP1–NRF2 system also regulates the expression of genes involved in cell proliferation and inflammation, indicating that the system plays cell type-specific roles. In this review, we introduce the multifarious roles of the KEAP1–NRF2 system in various types of cells, especially focusing on cancer and inflammatory diseases. Cancer cells frequently hijack the KEAP1–NRF2 system, and NRF2 activation confers cancer cells with a proliferative advantage and therapeutic resistance. In contrast, the activation of NRF2 in immune cells, especially in myeloid cells, suppresses tumor development. In chronic inflammatory diseases, such as sickle cell disease, NRF2 activation in myeloid and endothelial cells represses the expression of proinflammatory cytokine and adherent molecule genes, mitigating inflammation and organ damage. Based on these cell-specific roles played by the KEAP1–NRF2 system, NRF2 inducers have been utilized for the treatment of inflammatory diseases. In addition, the use of NRF2 inducers and/or inhibitors with canonical antineoplastic drugs is an emerging approach to cancer treatment.

Recent Advances in Understanding Nrf2 Agonism and Its Potential Clinical Application to Metabolic and Inflammatory Diseases

Oxidative stress is a major component of cell damage and cell fat, and as such, it occupies a central position in the pathogenesis of metabolic disease. Nuclear factor-erythroid-derived 2-related factor 2 (Nrf2), a key transcription factor that coordinates expression of genes encoding antioxidant and detoxifying enzymes, is regulated primarily by Kelch-like ECH-associated protein 1 (Keap1). However, involvement of the Keap1–Nrf2 pathway in tissue and organism homeostasis goes far beyond protection from cellular stress. In this review, we focus on evidence for Nrf2 pathway dysfunction during development of several metabolic/inflammatory disorders, including diabetes and diabetic complications, obesity, inflammatory bowel disease, and autoimmune diseases. We also review the beneficial role of current molecular Nrf2 agonists and summarize their use in ongoing clinical trials. We conclude that Nrf2 is a promising target for regulation of numerous diseases associated with oxidative stress and inflammation. However, more studies are needed to explore the role of Nrf2 in the pathogenesis of metabolic/inflammatory diseases and to review safety implications before therapeutic use in clinical practice.

Machine Learning Identifies Pan-Cancer Landscape of Nrf2 Oxidative Stress Response Pathway-Related Genes

BACKGROUND

Oxidative stress produced a large amount of reactive oxygen species (ROS), which played a pivotal role in balanced ability and determining cell fate. The activated Nrf2 signaling pathway that responds to the excessive ROS regulated the expressions of antiapoptotic proteins, antioxidative enzymes, drug transporters, and detoxifying factors.

METHODS

The Nrf2 signaling pathway-related genes that had a direct relationship with Nrf2, including ATF4, BACH1, CREBBP, CUL3, EIF2AK3, EP300, FOS, FOSL1, GSK3B, JUN, KEAP1, MAF, MAFF, MAFG, MAFK, MAPK1, MAPK3, MAPK7, MAPK8, MAPK9, PIK3CA, PRRT2, and RIT1, were selected to do a systematic pan-cancer analysis. The relationship of Nrf2 signaling pathway-related gene expressions with tumor mutation burden, microsatellite status, clinical characteristics, immune system, cancer stemness index, and drug sensitivity was calculated by the Spearson correlation analysis across 11,057 subjects representing 33 cancer types. The prognosis models in lung squamous carcinoma, breast cancer, and stomach cancer were constructed with the Cox multivariate regression analysis and least absolute shrinkage and selection operator (Lasso) regression.

RESULTS

Many Nrf2 signaling pathway-related genes were differently expressed between tumor and normal tissues. PIK3CA showed high mutation rate in pan-cancer. The expressions of Nrf2 signaling pathway-related genes were significantly related to tumor mutation burden, copy number variant, microsatellite instability score, survival rate, pathological stage, immune phenotype, immune score, immune cell, cancer stemness index, and drug sensitivity. The prognosis models were significantly associated with survival rate in lung squamous carcinoma, breast cancer, and stomach cancer; and the prognosis model-based riskscore was significantly associated with clinicopathological characteristics of each cancer.

CONCLUSIONS

The study provided a comprehensive pan-cancer landscape of Nrf2 pathway-related genes. Based on the same Nrf2 pathway-related genes, the different prognosis models were constructed for different types of cancers.

NRF2: KEAPing Tumors Protected

The Kelch-like ECH-associated protein 1 (KEAP1)/nuclear factor erythroid 2-related factor 2 (NRF2) pathway plays a physiologic protective role against xenobiotics and reactive oxygen species. However, activation of NRF2 provides a powerful selective advantage for tumors by rewiring metabolism to enhance proliferation, suppress various forms of stress, and promote immune evasion. Genetic, epigenetic, and posttranslational alterations that activate the KEAP1/NRF2 pathway are found in multiple solid tumors. Emerging clinical data highlight that alterations in this pathway result in resistance to multiple therapies. Here, we provide an overview of how dysregulation of the KEAP1/NRF2 pathway in cancer contributes to several hallmarks of cancer that promote tumorigenesis and lead to treatment resistance. SIGNIFICANCE: Alterations in the KEAP1/NRF2 pathway are found in multiple cancer types. Activation of NRF2 leads to metabolic rewiring of tumors that promote tumor initiation and progression. Here we present the known alterations that lead to NRF2 activation in cancer, the mechanisms in which NRF2 activation promotes tumors, and the therapeutic implications of NRF2 activation.

The Age-Specific Features and Clinical Significance of NRF2 and MAPK10 Expression in HCC Patients

Background

Nuclear factor (erythroid-derived 2)-like 2 (NRF2) functions decline with age; however, cancer cells can hijack its pathways to ensure survival and aggressiveness. Yet, the role of NRF2 in hepatocellular carcinoma (HCC) is rarely investigated in an age-specific manner. This study investigates the expression of NRF2 and its activator (MAPK10) in different age groups of HCC patients, in addition to the age-specific features of NRF2 and MAPK10 interaction and their clinical significance.

Methods

Tumor and near-tumor tissue samples of 181 HCC patients were used to complete a protein expression analysis of NRF2 and MAPK10. Patients’ survival and clinical data were collected for clinical analysis. Global databases (TCGA, ICGC) were used to collect MAPK10 genetic mutation and mRNA expression data in patients with HCC, colorectal, stomach, and pancreatic cancers.

Results

Our findings revealed an increase in NRF2 protein expression but only in younger HCC patients, along with a decline in MAPK10 ability to activate NRF2 in older patients. We also found an increased MAPK10 genetic mutation rate and decreased mRNA expression in older patients. Low MAPK10 and NRF2 expression levels were associated with shorter survival and poorer prognosis due to positive correlation with microvascular invasion, tumor thrombus, elevated AFP levels, and larger tumor size.

Conclusion

NRF2 expression and oxidative stress mechanism in HCC patients are influenced by age. This magnifies the need to consider patients’ age in treatment strategies and guidelines and re-evaluates the application of studies’ age-standardized findings in older patients who are usually excluded from relevant research.

New Discoveries and Ambiguities of Nrf2 and ATF3 Signaling in Environmental Arsenic-Induced Carcinogenesis

Environment exposure to arsenic had been linked to increased incidents of human cancers. In cellular and animal experimental systems, arsenic has been shown to be highly capable of activating several signaling pathways that play critical roles in cell growth regulation, malignant transformation and the stemness of cancer stem-like cells. Emerging evidence indicates certain oncogenic properties of the Nrf2 transcription factor that can be activated by arsenic and many other environmental hazards. In human bronchial epithelial cells, our most recent data suggested that arsenic-activated Nrf2 signaling fosters metabolic reprogramming of the cells through shifting mitochondrial TCA cycle to cytosolic glycolysis, and some of the metabolites in glycolysis shunt the hexosamine biosynthesis and serine-glycine pathways important for the energy metabolism of the cancer cells. In the current report, we further demonstrated direct regulation of oncogenic signals by arsenic-activated Nrf2 and connection of Nrf2 with ATF3 stress transcription factor. Meanwhile, we also highlighted some unanswered questions on the molecular characteristics of the Nrf2 protein, which warrants further collaborative efforts among scientists for understanding the important role of Nrf2 in human cancers either associated or not to environmental arsenic exposure.

Cancer Chemopreventive Role of Dietary Terpenoids by Modulating Keap1-Nrf2-ARE Signaling System—A Comprehensive Update

ROS, RNS, and carcinogenic metabolites generate excessive oxidative stress, which changes the basal cellular status and leads to epigenetic modification, genomic instability, and initiation of cancer. Epigenetic modification may inhibit tumor-suppressor genes and activate oncogenes, enabling cells to have cancer promoting properties. The nuclear factor erythroid 2-related factor 2 (Nrf2) is a transcription factor that in humans is encoded by the NFE2L2 gene, and is activated in response to cellular stress. It can regulate redox homoeostasis by expressing several cytoprotective enzymes, including NADPH quinine oxidoreductase, heme oxygenase-1, UDP-glucuronosyltransferase, glutathione peroxidase, glutathione-S-transferase, etc. There is accumulating evidence supporting the idea that dietary nutraceuticals derived from commonly used fruits, vegetables, and spices have the ability to produce cancer chemopreventive activity by inducing Nrf2-mediated detoxifying enzymes. In this review, we discuss the importance of these nutraceuticals in cancer chemoprevention and summarize the role of dietary terpenoids in this respect. This approach was taken to accumulate the mechanistic function of these terpenoids to develop a comprehensive understanding of their direct and indirect roles in modulating the Keap1-Nrf2-ARE signaling system.

Myeloid-derived suppressor cells as immunosuppressive regulators and therapeutic targets in cancer

Myeloid-derived suppressor cells (MDSCs) are a heterogenic population of immature myeloid cells with immunosuppressive effects, which undergo massive expansion during tumor progression. These cells not only support immune escape directly but also promote tumor invasion via various non-immunological activities. Besides, this group of cells are proved to impair the efficiency of current antitumor strategies such as chemotherapy, radiotherapy, and immunotherapy. Therefore, MDSCs are considered as potential therapeutic targets for cancer therapy. Treatment strategies targeting MDSCs have shown promising outcomes in both preclinical studies and clinical trials when administrated alone, or in combination with other anticancer therapies. In this review, we shed new light on recent advances in the biological characteristics and immunosuppressive functions of MDSCs. We also hope to propose an overview of current MDSCs-targeting therapies so as to provide new ideas for cancer treatment.

Targeting NRF2 and Its Downstream Processes: Opportunities and Challenges

The transcription factor NRF2 coordinates the expression of a vast array of cytoprotective and metabolic genes in response to various stress inputs to restore cellular homeostasis. Transient activation of NRF2 in healthy tissues has been long recognized as a cellular defense mechanism and is critical to prevent cancer initiation by carcinogens. However, cancer cells frequently hijack the protective capability of NRF2 to sustain the redox balance and meet their metabolic requirements for proliferation. Further, aberrant activation of NRF2 in cancer cells confers resistance to commonly used chemotherapeutic agents and radiotherapy. During the last decade, many research groups have attempted to block NRF2 activity in tumors to counteract the survival and proliferative advantage of cancer cells and reverse resistance to treatment. In this review, we highlight the role of NRF2 in cancer progression and discuss the past and current approaches to disable NRF2 signaling in tumors. Expected final online publication date for the Annual Review of Pharmacology and Toxicology, Volume 62 is January 2022. Please see http://www.annualreviews.org/page/journal/pubdates for revised estimates.

The nexus between redox state and intermediary metabolism

Reactive oxygen species (ROS) are not just a by-product of cellular metabolic processes but act as signalling molecules that regulate both physiological and pathophysiological processes. A close connection exists in cells between redox homeostasis and cellular metabolism. In this review, we describe how intracellular redox state and glycolytic intermediary metabolism are closely coupled. On the one hand, ROS signalling can control glycolytic intermediary metabolism by direct regulation of the activity of key metabolic enzymes and indirect regulation via redox-sensitive transcription factors. On the other hand, metabolic adaptation and reprogramming in response to physiological or pathological stimuli regulate intracellular redox balance, through mechanisms such as the generation of reducing equivalents. We also discuss the impact of these intermediary metabolism-redox circuits in physiological and disease settings across different tissues. A better understanding of the mechanisms regulating these intermediary metabolism-redox circuits will be crucial to the development of novel therapeutic strategies.

Mangiferin mitigates di-(2-ethylhexyl) phthalate-induced testicular injury in rats by modulating oxidative stress-mediated signals, inflammatory cascades, apoptotic pathways, and steroidogenesis

Di-(2-ethylhexyl) phthalate (DEHP) is an endocrine disruptor that causes reproductive defects in male animal models. This study was conducted to explore the plausible modulatory effects of mangiferin (MF) against DEHP-induced testicular injury in rats. Thirty-two adult male albino rats were allocated into four groups. Two groups were given DEHP (2 g/kg/day, p.o) for 14 days. One of these groups was treated with MF (20 mg/kg/day, i.p) for 7 days before and 14 days after DEHP administration. A vehicle-treated control was included, and another group of rats was given MF only. Results revealed that MF treatment suppressed oxidative testicular injury by amplifying the mRNA expression of nuclear factor-erythroid 2 related factor-2 (Nrf2) and increasing hemoxygenase-1 (HO-1), glutathione, and total antioxidant capacity (TAC) levels. This treatment also enhanced superoxide dismutase activity, but it decreased malondialdehyde and nitric oxide levels. MF had an anti-inflammatory characteristic, as demonstrated by the downregulation of the mRNA of the nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB). The content of tumor necrosis factor-alpha also decreased. MF modulated the apoptotic pathway by suppressing the mRNA of cytochrome c (Cyt c), Fas ligand content, Bax IHC expression, caspase-3 activity and cleaved caspase-3 IHC expression. It also upregulated the expression levels of heat-shock protein 70 (HSP70) and B-cell lymphoma 2. Moreover, MF upregulated the mRNA expression levels of HSP70 and c-kit and enriched the content of steroidogenic acute regulatory (StAR) protein, which were reflected in serum testosterone levels. This result indicated that MF played crucial roles in steroidogenesis and spermatogenesis. Besides, the activities of testicular marker enzymes, namely, acid and alkaline phosphatases, and lactate dehydrogenase, significantly increased. Histopathological observations provided evidence supporting the biochemical and molecular measurements. In conclusion, MF provided protective mechanisms against the DEHP-mediated deterioration of testicular functions partially through its antioxidant, anti-inflammatory, and anti-apoptotic properties. It also involved the restoration of steroidogenesis and spermatogenesis through the modulation of Nrf2/HO-1, NF-κB/Cyt c/HSP70, and c-Kit signaling cascades.

Diallyl Disulfide Attenuates Ionizing Radiation-Induced Migration and Invasion by Suppressing Nrf2 Signaling in Non-small-Cell Lung Cancer

Non–small-cell lung cancer (NSCLC) is the leading cause of cancer-associated deaths. Radiotherapy remains the primary treatment method for NSCLC. Despite great advances in radiotherapy techniques and modalities, recurrence and resistance still limit therapeutic success, even low-dose ionizing radiation (IR) can induce the migration and invasion. Diallyl disulfide (DADS), a bioactive component extracted from garlic, exhibits a wide spectrum of biological activities including antitumor effects. However, the effect of DADS on IR-induced migration and invasion remains unclear. The present study reported that IR significantly promoted the migration and invasion of A549 cells. Pretreatment with 40 μM DADS enhanced the radiosensitivity of A549 cells and attenuated IR-induced migration and invasion. In addition, 40 μM DADS inhibited migration-related protein matrix metalloproteinase-2 and 9 (MMP-2/9) expression and suppressed IR-aggravated EMT by the upregulation of the epithelial marker, E-cadherin, and downregulation of the mesenchymal marker, N-cadherin, in A549 cells. Furthermore, DADS was found to inhibit the activation of Nrf2 signaling. Based on our previous results that knockdown of Nrf2 by siRNA suppressed IR-induced migration and invasion in A549 cells, we speculated that DADS attenuated IR-induced migration and invasion by suppressing the activation of Nrf2 signaling in A549 cells.

Role of reactive oxygen species in tumors based on the 'seed and soil' theory: A complex interaction (Review)

Tumor microenvironment (TME) can serve as the 'soil' for the growth and survival of tumor cells and function synergically with tumor cells to mediate tumor progression and therapeutic resistance. Reactive oxygen species (ROS) is somewhat of a double‑edged sword for tumors. Accumulating evidence has reported that regulating ROS levels can serve an anti‑tumor role in the TME, including the promotion of cancer cell apoptosis, inhibition of angiogenesis, preventing immune escape, manipulating tumor metabolic reorganization and improving drug resistance. In the present review, the potential role of ROS in anti‑tumor therapy was summarized, including the possibility of directly or indirectly targeting the TME.

Role of NRF2 in Lung Cancer

The gene expression program induced by NRF2 transcription factor plays a critical role in cell defense responses against a broad variety of cellular stresses, most importantly oxidative stress. NRF2 stability is fine-tuned regulated by KEAP1, which drives its degradation in the absence of oxidative stress. In the context of cancer, NRF2 cytoprotective functions were initially linked to anti-oncogenic properties. However, in the last few decades, growing evidence indicates that NRF2 acts as a tumor driver, inducing metastasis and resistance to chemotherapy. Constitutive activation of NRF2 has been found to be frequent in several tumors, including some lung cancer sub-types and it has been associated to the maintenance of a malignant cell phenotype. This apparently contradictory effect of the NRF2/KEAP1 signaling pathway in cancer (cell protection against cancer versus pro-tumoral properties) has generated a great controversy about its functions in this disease. In this review, we will describe the molecular mechanism regulating this signaling pathway in physiological conditions and summarize the most important findings related to the role of NRF2/KEAP1 in lung cancer. The focus will be placed on NRF2 activation mechanisms, the implication of those in lung cancer progression and current therapeutic strategies directed at blocking NRF2 action.

Myeloid-derived suppressor cells: Important communicators in systemic lupus erythematosus pathogenesis and its potential therapeutic significance

Systemic lupus erythematosus (SLE) is a recognized chronic condition associated with immune system disorders that affect women nine times more commonly than men. SLE is characterized by over-secretion and release of autoantibodies in response to different cellular compartments and self-tolerance breaks to its own antigens. The detailed immunological dysregulation as an associated event that elicits the onset of clinical manifestations of SLE has not been clarified yet. Though, research using several animal models in the last two decades has indicated the role of the immune system in the pathogenesis of this disease. Myeloid-derived suppressor cells (MDSCs) as heterogeneous myeloid cells, are responsible for severe pathological conditions, including infection, autoimmunity, and cancer, by exerting considerable immunosuppressive effects on T-cells responses. It has been reported that these cells are involved in the regulation process of the immune response in several autoimmune diseases, particularly SLE. The function of MDSC is deleterious in infection and cancer diseases, though their role is more complicated in autoimmune diseases. In this review, we summarized the role and function of MDSCs in the pathogenesis and progression of SLE and its possible therapeutic approach.

Regulation of redox signaling in HIF-1-dependent tumor angiogenesis

Angiogenesis is the process of blood vessel growth. The angiogenic switch consists of new blood vessel formation that, in carcinogenesis, can lead to the transition from a harmless cluster of dormant cells to a large tumorigenic mass with metastatic potential. Hypoxia, that is, the scarcity of oxygen, is a hallmark of solid tumors to which they adapt by activating hypoxia-inducible factor-1 (HIF-1), a transcription factor triggering de novo angiogenesis. HIF-1 and the angiogenic molecules that are expressed upon its activation are modulated by redox status. Modulations of the redox environment can influence the angiogenesis signaling at different levels, thereby impinging on the angiogenic switch. This review provides a molecular overview of the redox-sensitive steps in angiogenic signaling, the main molecular players involved, and their crosstalk with the unfolded protein response. New classes of inhibitors of these modulators which might act as antiangiogenic drugs in cancer are also discussed.

Oxidative stress and redox signaling in CRPC progression: therapeutic potential of clinically-tested Nrf2-activators

Androgen deprivation therapy (ADT) is the mainstay regimen in patients with androgen-dependent prostate cancer (PCa). However, the selection of androgen-independent cancer cells leads to castrate resistant prostate cancer (CRPC). The aggressive phenotype of CRPC cells underscores the need to elucidate mechanisms and therapeutic strategies to suppress CRPC outgrowth. Despite ADT, the activation of androgen receptor (AR) transcription factor continues via crosstalk with parallel signaling pathways. Understanding of how these signaling cascades are initiated and amplified post-ADT is lacking. Hormone deprivation can increase oxidative stress and the resultant reactive oxygen species (ROS) may activate both AR and non-AR signaling. Moreover, ROS-induced inflammatory cytokines may further amplify these redox signaling pathways to augment AR function. However, clinical trials using ROS quenching small molecule antioxidants have not suppressed CRPC progression, suggesting that more potent and persistent suppression of redox signaling in CRPC cells will be needed. The transcription factor Nrf2 increases the expression of numerous antioxidant enzymes and downregulates the function of inflammatory transcription factors, e.g., nuclear factor kappa B. We documented that Nrf2 overexpression can suppress AR-mediated transcription in CRPC cell lines. Furthermore, two Nrf2 activating agents, sulforaphane (a phytochemical) and bardoxolone-methyl (a drug in clinical trial) suppress AR levels and sensitize CRPC cells to anti-androgens. These observations implicate the benefits of potent Nrf2-activators to suppress the lethal signaling cascades that lead to CRPC outgrowth. This review article will address the redox signaling networks that augment AR signaling during PCa progression to CRPC, and the possible utility of Nrf2-activating agents as an adjunct to ADT.

How Macrophages Become Transcriptionally Dysregulated: A Hidden Impact of Antitumor Therapy

Tumor-associated macrophages (TAMs) are the essential components of the tumor microenvironment. TAMs originate from blood monocytes and undergo pro- or anti-inflammatory polarization during their life span within the tumor. The balance between macrophage functional populations and the efficacy of their antitumor activities rely on the transcription factors such as STAT1, NF-κB, IRF, and others. These molecular tools are of primary importance, as they contribute to the tumor adaptations and resistance to radio- and chemotherapy and can become important biomarkers for theranostics. Herein, we describe the major transcriptional mechanisms specific for TAM, as well as how radio- and chemotherapy can impact gene transcription and functionality of macrophages, and what are the consequences of the TAM-tumor cooperation.

Proteomic characteristics and identification of PM2.5-induced differentially expressed proteins in hepatocytes and c-Myc silenced hepatocytes

Proteomics and bioinformatics were applied to explore PM_2.5-induced differentially expressed proteins (DEPs) in hepatocytes (L02 cells) and c-Myc-silenced hepatocytes. L02 cells and c-Myc-silenced hepatocytes were treated with PM_2.5 for 24 h. Fifty-two DEPs were screened in L02 hepatocytes, of which 28 were upregulated and 24 were downregulated. Forty-one DEPs were screened in the c-Myc-silenced hepatocytes, of which 31 were upregulated and 10 were downregulated. GO analysis showed that DEPs in L02 cells were mainly concentrated in the cytosol and were involved in biological processes such as the response to metal ions. DEPs in c-Myc-silenced cells were mainly enriched in the extracellular space and were involved in lipoprotein metabolism. KEGG analysis showed that DEPs in L02 cells were mainly involved in arachidonic acid metabolism and mineral absorption. DEPs in c-Myc-silenced cells were mainly enriched in pathways involving nerve absorption, complement and coagulation cascades, and other pathways. Twenty key proteins, including Metallothionein-2A (MT2A), Metallothionein-1X (MT1X), zinc transporter ZIP10 (SLC39A10) and Serine protease 23 (PRSS23) were screened in two groups through analysis of protein-protein interactions. Based on the identification of the selected DEPs, PRSS23 and SLC39A10 might be the potential biomarker of PM_2.5-induced carcinogenesis, which provide the scientific basis for further research into the carcinogenic mechanisms of PM_2.5.

Cellular Nrf2 Levels Determine Cell Fate during Chemical Carcinogenesis in Esophageal Epithelium

Nrf2 is essential for cytoprotection against carcinogens, and through systemic Nrf2 knockout mice, Nrf2-deficient cells were shown to be susceptible to chemical carcinogens and prone to developing cancers. However, the oncogenic potential of Nrf2-deficient epithelial cells surrounded by normal cells in the esophagus could not be assessed by previous models, and the fate of Nrf2-deficient cells in such situations remains elusive. In this study, therefore, we generated mice that harbor almost equal levels of cells with Nrf2 deleted and those with Nrf2 intact in the basal layer of the esophageal epithelium, utilizing inducible Cre-mediated recombination of Nrf2 alleles in adults through moderate use of tamoxifen. In this mouse model, epithelial cells with Nrf2 deleted were maintained with no obvious decrease or phenotypic changes for 12 weeks under unstressed conditions. Upon exposure to the carcinogen 4-nitroquinoline-1-oxide (4NQO), the cells with Nrf2 deleted accumulated DNA damage and selectively disappeared from the epithelium, so almost all 4NQO-induced tumors originated from cells with Nrf2 intact and not from those with Nrf2 deleted. We propose that cells with Nrf2 deleted do not undergo carcinogenesis due to selective elimination upon exposure to 4NQO, indicating that cellular Nrf2 abundance and the epithelial environment determine the cell fate or oncogenic potential of esophageal epithelial cells in 4NQO-induced carcinogenesis.

Regulation of ROS in myeloid-derived suppressor cells through targeting fatty acid transport protein 2 enhanced anti-PD-L1 tumor immunotherapy

Despite the remarkable success and efficacy of immune checkpoint blockade (ICB) therapy against the PD-1/PD-L1 axis, it induces sustained responses in a sizeable minority of cancer patients due to the activation of immunosuppressive factors such as myeloid-derived suppressor cells (MDSCs). Inhibiting the immunosuppressive function of MDSCs is critical for successful cancer ICB therapy. Interestingly, lipid metabolism is a crucial factor in modulating MDSCs function. Fatty acid transport protein 2 (FATP2) conferred the function of PMN-MDSCs in cancer via the upregulation of arachidonic acid metabolism. However, whether regulating lipid accumulation in MDSCs by targeting FATP2 could block MDSCs reactive oxygen species (ROS) production and enhance PD-L1 blockade-mediated tumor immunotherapy remains unexplored. Here we report that FATP2 regulated lipid accumulation, ROS, and immunosuppressive function of MDSCs in tumor-bearing mice. Tumor cells-derived granulocyte macrophage-colony stimulating factor (GM-CSF) induced FATP2 expression in MDSCs by activation of STAT3 signaling pathway. Pharmaceutical blockade of FATP2 expression in MDSCs by lipofermata decreased lipid accumulation, reduced ROS, blocked immunosuppressive activity, and consequently inhibited tumor growth. More importantly, lipofermata inhibition of FATP2 in MDSCs enhanced anti-PD-L1 tumor immunotherapy via the upregulation of CD107a and reduced PD-L1 expression on tumor-infiltrating CD8⁺T-cells. Furthermore, the combination therapy blocked MDSC's suppressive role on T- cells thereby enhanced T-cell's ability for the production of IFN-γ. These findings indicate that FATP2 plays a key role in modulating lipid accumulation-induced ROS in MDSCs and targeting FATP2 in MDSCs provides a novel therapeutic approach to enhance anti-PD-L1 cancer immunotherapy.

Puerarin induces apoptosis in prostate cancer cells via inactivation of the Keap1/Nrf2/ARE signaling pathway

In this study, we examined the antitumor effects of Puerarin (PEU) on androgen-independent (DU145 and PC-3) and androgen-dependent (LNCaP) prostate cancer cells, and explored its potential mechanisms. Supplement with PEU (2.5 μM, 5 μM, and 10 μM) exhibited a marked inhibitory effect against the growth of DU145 and PC-3 cells, especially beyond 24 h, whereas there is only slight growth inhibitory effect on LNCaP cells at the high concentration of 10 μM at 72 h. This loss of cell viability in DU145 and PC-3 cells by PEU was mediated by the induction of apoptosis via up-regulation of Bax and cleaved-caspase-3, but downregulation of Bcl-2. Moreover, more intracellular ROS and LDH production were observed in DU145 and PC-3 cells upon PEU treatment. Meanwhile, the amount of pro-inflammatory cytokines (IL-1β and IL-6) was increased, but the content of anti-inflammatory cytokines IL-10 was attenuated. Additionally, PEU pretreatment resulted in an increase of Keap1 protein expression, and a decline of Nrf2, HO-1 and NQO1 protein expression in DU145 and PC3 cells. The present findings indicated that PEU exerted its antitumor activities toward androgen-independent prostate cancer cells via inactivation of Keap1/NrF2/ARE signaling pathway.