Downregulation of Nrf2 promotes radiation-induced apoptosis through Nrf2 mediated Notch signaling in non-small cell lung cancer cells

Unveiling Novel Targets in Lung Tumors for Enhanced Radiotherapy Efficacy: A Comprehensive Review

Radiotherapy is a cornerstone of lung cancer management, though its efficacy is frequently undermined by intrinsic and acquired radioresistance. This review examines the complexity of lung tumors, highlighting their potential as a reservoir of novel targets for radiosensitization. Ionizing radiation (IR) primarily exerts its effects through oxidative damage and DNA double-strand breaks (DSBs). Lung cancer cells, however, develop mutations that enhance DNA damage response (DDR) and suppress cell death pathways. Additionally, interactions between tumor cells and tumor microenvironment (TME) components-including immune cells, stromal cells, and molecular mediators such as cytokines, chemokines, and growth factors-contribute to resistance against IR. Understanding these intricate relationships reveals potential targets to improve radiotherapy outcomes. Promising targets include DDR pathways, immunosuppressive cells and molecules, hypoxia, proangiogenic mediators, and other key signaling pathways. This review discusses emerging strategies, such as combining radiotherapy with immunomodulators, hypoxia and proangiogenic inhibitors, DDR-targeting agents, and other innovative approaches. By offering a comprehensive analysis of the lung TME, this review underscores opportunities to enhance radiotherapy effectiveness through targeted radiosensitization strategies.

NRF2 Signaling Pathway in Chemo/Radio/Immuno-Therapy Resistance of Lung Cancer: Looking Beyond the Tip of the Iceberg

Lung cancer is one of the most common causes of cancer death in men and women worldwide. Various combinations of surgery, chemotherapy, radiation therapy and immunotherapy are currently used to treat lung cancer. However, the prognosis remains relatively poor due to the higher frequency of tumor mutational burden (TMB). Nuclear factor E2-related factor 2 (NFE2L2/NRF2) is often considered a primary regulator of the expression of antioxidant enzymes and detoxification proteins and is involved in cytoprotection. On the contrary, NRF2 is even known to induce metastasis and support tumor progression. Kelch-like ECH-associated protein 1 (KEAP1) plays an important role in negatively regulating NRF2 activity via CUL3-mediated ubiquitinylation and successive proteasomal degradation. Extensive research has shown that the genetic alterations of KEAP1/NFE2L2/CUL3 genes lead to increased expression of NRF2 and its target genes in lung cancer. Thus, these studies provide ample evidence for the dual role of NRF2 in lung cancer. In this review, we discussed the mechanistic insights into the role of NRF2 signaling in therapy resistance by focusing on cell lines, mouse models, and translational studies in lung cancer. Finally, we highlighted the potential therapeutic strategies targeting NRF2 inhibition, followed by the discussion of biomarkers related to NRF2 activity in lung cancer. Overall, our article exclusively discusses in detail the NRF2 signaling pathway in resistance to therapy, especially immunotherapy, and its therapeutic avenue in the treatment of lung cancer.

Clobetasol propionate, a Nrf-2 inhibitor, sensitizes human lung cancer cells to radiation-induced killing via mitochondrial ROS-dependent ferroptosis

Combining radiotherapy with Nrf-2 inhibitor holds promise as a potential therapeutic strategy for radioresistant lung cancer. Here, the radiosensitizing efficacy of a synthetic glucocorticoid clobetasol propionate (CP) in A549 human lung cancer cells was evaluated. CP exhibited potent radiosensitization in lung cancer cells via inhibition of Nrf-2 pathway, leading to elevation of oxidative stress. Transcriptomic studies revealed significant modulation of pathways related to ferroptosis, fatty acid and glutathione metabolism. Consistent with these findings, CP treatment followed by radiation exposure showed characteristic features of ferroptosis in terms of mitochondrial swelling, rupture and loss of cristae. Ferroptosis is a form of regulated cell death triggered by iron-dependent ROS accumulation and lipid peroxidation. In combination with radiation, CP showed enhanced iron release, mitochondrial ROS, and lipid peroxidation, indicating ferroptosis induction. Further, iron chelation, inhibition of lipid peroxidation or scavenging mitochondrial ROS prevented CP-mediated radiosensitization. Nrf-2 negatively regulates ferroptosis through upregulation of antioxidant defense and iron homeostasis. Interestingly, Nrf-2 overexpressing A549 cells were refractory to CP-mediated ferroptosis induction and radiosensitization. Thus, this study identified anti-psoriatic drug clobetasol propionate can be repurposed as a promising radiosensitizer for Keap-1 mutant lung cancers.

Critical role of the long non-coding RNAs (lncRNAs) in radiotherapy (RT)-resistance of gastrointestinal (GI) cancer: Is there a way to defeat this resistance?

Radiotherapy (RT) is a frequently used treatment for cervical cancer, effectively decreasing the likelihood of the disease returning in the same area and extending the lifespan of individuals with cervical cancer. Nevertheless, the primary reason for treatment failure in cancer patients is the cancer cells' resistance to radiation therapy (RT). Long non-coding RNAs (LncRNAs) are a subset of RNA molecules that do not code for proteins and are longer than 200 nucleotides. They have a significant impact on the regulation of gastrointestinal (GI) cancers biological processes. Recent research has shown that lncRNAs have a significant impact in controlling the responsiveness of GI cancer to radiation. This review provides a concise overview of the composition and operation of lncRNAs as well as the intricate molecular process behind radiosensitivity in GI cancer. Additionally, it compiles a comprehensive list of lncRNAs that are linked to radiosensitivity in such cancers. Furthermore, it delves into the potential practical implementation of these lncRNAs in modulating radiosensitivity in GI cancer.

Notch signaling and targeted therapy in non-small cell lung cancer

The Notch signaling pathway plays pivotal roles in cell proliferation, stemness and invasion of non-small cell lung cancer (NSCLC). The human Notch family consists of four receptors, namely Notch1, Notch2, Notch3, and Notch4. These receptors are transmembrane proteins that play crucial roles in various cellular processes. Notch1 mostly acts as a pro-carcinogenic factor in NSCLC but sometimes acts as a suppressor. Notch2 has been demonstrated to inhibit the growth and progression of NSCLC, whereas Notch3 facilitates these biological behaviors of NSCLC. The role of Notch4 in NSCLC has not been fully elucidated, but it is evident that Notch4 promotes tumor progression. At present, drugs targeting the Notch pathway are being explored for NSCLC therapy, a majority of which are already in the stage of preclinical research and clinical trials, with bright prospects in the clinical treatment of NSCLC.

Phellodendronoside A Exerts Anticancer Effects Depending on Inducing Apoptosis Through ROS/Nrf2/Notch Pathway and Modulating Metabolite Profiles in Hepatocellular Carcinoma

Purpose

To reveal the potential mechanism of PDA on hepatocellular carcinoma SMMC-7721 cells in vitro.

Methods

The cytotoxic activity, colony formation, cell cycle distribution, apoptosis and their associated protein analysis, intracellular reactive oxygen species (ROS) and Ca²⁺ levels, proteins in Nrf2 and Ntoch pathways and metabolite profiles of PDA against hepatocellular carcinoma were investigated.

Results

PDA with cytotoxic activity inhibited cell proliferation and migration, increased intracellular ROS, Ca²⁺ levels and MCUR1 protein expression in a dose-dependent manner, caused cell cycle arrest in the S phase and induced apoptosis via adjusting the levels of Bcl-2, Bax, and Caspase 3 proteins, and inhibited the activation of Notch1, Jagged, Hes1, Nrf2 and HO-1 proteins. Metabonomics data showed that PDA significantly regulated 144 metabolite levels tend to be normal level, especially carnitine derivatives, bile acid metabolites associated with hepatocellular carcinoma, and mainly enriched in ABC transporter, arginine and proline metabolism, primary bile acid biosynthesis, Notch signaling pathway, etc, and proved that PDA markedly adjusted Notch signaling pathway.

Conclusion

PDA exhibited the proliferation inhibition of SMMC-7721 cells by inhibiting ROS/Nrf2/Notch signaling pathway and significantly affected the metabolic profile, suggesting PDA could be a potential therapeutic agent for patients with hepatocellular carcinoma.

LncRNA UCA1 promoted cisplatin resistance in lung adenocarcinoma with HO1 targets NRF2/HO1 pathway

PURPOSE

Our previous experiments have demonstrated that lncRNA UCA1 (UCA1) promoted cisplatin resistance in lung adenocarcinoma (LUAD). This study aimed to explore the potential downstream target genes regulated by UCA1 and how this downstream gene promotes cisplatin resistance in LUAD.

METHODS

Here, we measured the expression level of Heme oxygenase1 (HO1) in LUAD cell lines by reverse transcription-quantitative polymerase chain reaction (RT-qPCR) based on UCA1 overexpression cell lines and UCA1 knockdown cell lines. HO1 was knocked down in the UCA1 overexpression cell line, and HO1 was overexpressed in the UCA1 knockdown cell line, and the half maximal inhibitory concentration (IC50) trends were observed by adding cisplatin containing a certain concentration gradient. Cell functional assays were performed to observe the changes in the biological behavior of HO1 after overexpression and knockdown, and the tumorigenic assay in nude mice was performed to verify the effect of UCA1 in regulating the growth and cisplatin resistance of HO1 on LUAD cells in vivo.

RESULTS

The results showed that HO1 and UCA1 expression were both upregulated in LUAD tissues and LUAD cisplatin-resistant cell lines, and there was a significant positive correlation between the expression of HO1 and UCA1. In vitro experiments showed that HO1 overexpression could reverse the reduced sensitivity to cisplatin caused by UCA1 knockdown in A549/DDP cells, and HO1 knockdown could reduce cisplatin resistance in A549 UCA1 overexpressing cells. Tumorigenic assays in nude mice further confirmed the role of HO1 in the regulation of UCA1 by activating the NRF2/HO1 pathway against LUAD cisplatin resistance.

CONCLUSION

Our findings suggested that UCA1 regulates HO1 targets the UCA1/NRF2-HO1 pathway to exert cisplatin resistance in LUAD.

The measurement of NRF2 and TP53 in blood expects radiotherapeutic sensitivity in patients with esophageal cancer

OBJECTIVE

This study investigates the relationship between the mRNA expression of nuclear factor erythroid 2-related factor 2 (NRF2) and Tumor protein p53 (TP53) in circulating tumor cells (CTC) and sensitivity to radiotherapy in patients with esophageal cancer. To investigate the relationship between cytokines IL-6, CD8⁺, and NRF2 during patient treatment and their predictive role for treatment.

METHODS

Radiosensitivity was assessed by measuring a morphological or functional change in the tumor in response to ionizing radiation. Fasting venous anticoagulated blood (EDTA anticoagulation) was drawn from patients, and the Trizol-chloroform two-step method was used for RNA extraction. Data were collected from 45 patients admitted with radiotherapy alone from January 2018 to December 2021. The expression levels of NRF2mRNA (Messenger Ribose Nucleic Acid) and TP53mRNA in CTCs were detected by reverse transcription-polymerase chain reaction (RT-PCR). Pre- and post-treatment changes in IL-6 and CD8⁺ were recorded. The correlation between their expression level and the clinical stage, radiotherapy sensitivity, and efficacy of patients was analyzed.

RESULTS

Twenty-six cases were sensitive to radiotherapy, and 19 were resistant, for a radiotherapy sensitivity rate of 58.8%. NRF2mRNA and TP53mRNA values increased in 19 radiotherapy-resistant patients and decreased in 26 radiotherapy-sensitive patients compared with those before radiotherapy (P = 0.001, P＜0.05). The ΔCT values of NRF2mRNA and TP53mRNA before treatment were moderately correlated with prognosis (P < 0.002). Inflammatory cytokine IL-6 was elevated in 22 of 45 patients after radiation, P = 0.04. NRF2 mRNA level was consistently elevated with CD8⁺ in 10 patients, P = 0.02.

CONCLUSIONS

The expression of NRF2mRNA and TP53mRNA in the CTCs found in the peripheral blood of patients with esophageal squamous carcinoma was significantly associated with the sensitivity to radiotherapy. NRF2 mRNA level was consistently elevated with CD8⁺ and IL-6 in patients.

The Molecular and Cellular Strategies of Glioblastoma and Non-Small-Cell Lung Cancer Cells Conferring Radioresistance

Ionizing radiation (IR) has been shown to play a crucial role in the treatment of glioblastoma (GBM; grade IV) and non-small-cell lung cancer (NSCLC). Nevertheless, recent studies have indicated that radiotherapy can offer only palliation owing to the radioresistance of GBM and NSCLC. Therefore, delineating the major radioresistance mechanisms may provide novel therapeutic approaches to sensitize these diseases to IR and improve patient outcomes. This review provides insights into the molecular and cellular mechanisms underlying GBM and NSCLC radioresistance, where it sheds light on the role played by cancer stem cells (CSCs), as well as discusses comprehensively how the cellular dormancy/non-proliferating state and polyploidy impact on their survival and relapse post-IR exposure.

DJ-1 Protein Inhibits Apoptosis in Cerebral Ischemia by Regulating the Notch1 and Nuclear Factor Erythroid2-Related Factor 2 Signaling Pathways

DJ-1 plays a neuroprotective role in cerebral ischemia- reperfusion (I/R) injury and participates in the apoptosis of brain nerve cells, but the underlying mechanism is unclear. We explored the molecular pathways underlying this role using in vivo and in vitro approaches. Middle cerebral artery occlusion- reperfusion (MCAO/R) rat models and oxygen- glucose deprivation- reoxygenation (OGD/R) HAPI cell cultures were used to simulate cerebral ischemia-reperfusion injury. The interaction between DJ-1 and Notch1 was enhanced after MCAO/R in rats. After treatment of rats with DJ-1 siRNA, the expression of Notch1 and Nrf2 was down-regulated, and apoptosis was promoted. In contrast, the DJ-1 based peptide ND-13 upregulated the expression of Notch1 and Nrf2, and prevented apoptosis. In vitro, the Notch1 signaling pathway inhibitor DAPT reversed the neuroprotective effect of ND-13 and promoted apoptosis, weakened the interaction between DJ-1 and Notch1, and decreased the expression of proteins in the Notch1 and Nrf2 pathways. Thus, we found that DJ-1 inhibits apoptosis by regulating the Notch1 signaling pathway and Nrf2 expression in cerebral I/R injury. These results imply that DJ-1 is a potential therapeutic target for cerebral I/R injury.

The effect of Nrf2 deletion on the proteomic signature in a human colorectal cancer cell line

Background

Colorectal cancer is one of the most common cancer and the third leading cause of death worldwide. Increased generation of reactive oxygen species (ROS) is observed in many types of cancer cells. Several studies have reported that an increase in ROS production could affect the expression of proteins involved in ROS-scavenging, detoxification and drug resistance. Nuclear factor erythroid 2 related factor 2 (Nrf₂) is a known transcription factor for cellular response to oxidative stress. Several researches exhibited that Nrf₂ could exert multiple functions and expected to be a promising therapeutic target in many cancers. Here, Nrf₂ was knocked down in colorectal cancer cell line HT29 and changes that occurred in signaling pathways and survival mechanisms were evaluated.

Methods

The influence of chemotherapy drugs (doxorubicin and cisplatin), metastasis and cell viability were investigated. To explore the association between specific pathways and viability in HT29-Nrf₂⁻, proteomic analysis, realtime PCR and western blotting were performed.

Results

In the absence of Nrf₂ (Nrf₂⁻), ROS scavenging and detoxification potential were dramatically faded and the HT29-Nrf₂⁻ cells became more susceptible to drugs. However, a severe decrease in viability was not observed. Bioinformatic analysis of proteomic data revealed that in Nrf₂⁻ cells, proteins involved in detoxification processes, respiratory electron transport chain and mitochondrial-related compartment were down regulated. Furthermore, proteins related to MAPKs, JNK and FOXO pathways were up regulated that possibly helped to overcome the detrimental effect of excessive ROS production.

Conclusions

Our results revealed MAPKs, JNK and FOXO pathways connections in reducing the deleterious effect of Nrf₂ deficiency, which can be considered in cancer therapy.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12885-022-10055-y.

Signaling pathways and their potential therapeutic utility in esophageal squamous cell carcinoma

Esophageal cancer is a complex gastrointestinal malignancy with an extremely poor outcome. Approximately 80% of cases of this malignancy in Asian countries including India are of squamous cell origin, termed Esophageal Squamous Cell Carcinoma (ESCC).The five-year survival rate in ESCC patients is less than 20%. Neo-adjuvant chemo-radiotherapy (NACRT) followed by surgical resection remains the major therapeutic strategy for patients with operable ESCC. However, resistance to NACRT and local recurrence after initial treatment are the leading cause of dismal outcomes in these patients. Therefore, an alternative strategy to promote response to the therapy and reduce the post-operative disease recurrence is highly needed. At the molecular level, wide variations have been observed in tumor characteristics among different populations, nevertheless, several common molecular features have been identified which orchestrate disease progression and clinical outcome in the malignancy. Therefore, determination of candidate molecular pathways for targeted therapy remains the mainstream idea of focus in ESCC research. In this review, we have discussed the key signaling pathways associated with ESCC, i.e., Notch, Wnt, and Nrf2 pathways, and their crosstalk during disease progression. We further discuss the recent developments of novel agents to target these pathways in the context of targeted cancer therapy. In-depth research of the signaling pathways, gene signatures, and a combinatorial approach may help in discovering targeted therapy for ESCC.

Dietary Phytochemicals Targeting Nrf2 to Enhance the Radiosensitivity of Cancer

Nowadays, cancer has become the second leading cause of death worldwide. Radiotherapy (RT) is the mainstay in management of carcinoma; however, overcoming radioresistance remains a great challenge to successfully treat cancer. Nrf2 is a key transcription factor that is responsible for maintaining cellular redox homeostasis. Activation of Nrf2 signaling pathway could upregulate multifarious antioxidant and detoxifying enzymes, further scavenging excessive reactive oxygen species (ROS). Despite its cytoprotective roles in normal cells, it could also alleviate oxidative stress and DNA damage caused by RT in cancer cells, thus promoting cancer cell survival. Accumulating evidence indicates that overactivation of Nrf2 is associated with radioresistance; therefore, targeting Nrf2 is a promising strategy to enhance radiosensitivity. Dietary phytochemicals coming from natural products are characterized by low cost, low toxicity, and general availability. Numerous phytochemicals are reported to regulate Nrf2 and intensify the killing capability of RT through diverse mechanisms, including promoting oxidative stress, proapoptosis, and proautophagy as well as inhibiting Nrf2-mediated cytoprotective genes expression. This review summarizes recent advances in radiosensitizing effects of dietary phytochemicals by targeting Nrf2 and discusses the underlying mechanisms, including N6-methyladenosine (m6A) modification of Nrf2 mediated by phytochemicals in cancer.

ROS-Nrf2 pathway mediates the development of TGF-β1-induced epithelial-mesenchymal transition through the activation of Notch signaling

Epithelial-mesenchymal transition (EMT) is a cellular process by which epithelial cells transform to acquire mesenchymal phenotypes. Accumulating evidence indicate the involvement of EMT in the progression of malignant diseases. Notch signaling mediates TGF-β1-induced EMT through direct transcriptional activation of Snai1. The molecular mechanism how TGF-β1 activates Notch signaling, however, remains unknown. In this study, we show a pivotal role for reactive oxygen species (ROS)-Nrf2 pathway in TGF-β1-induced Notch signaling activation and EMT development. TGF-β1 induces Nrf2 activation through ROS production. Inhibiting Nrf2 activation either by reducing ROS levels by N-acetylcysteine or by knocking down of Nrf2 by small interfering RNA attenuated both Notch signaling activation and EMT development. TGF-β1 induced the transcription of Notch4 via Nrf2-dependent promoter activation. In conclusion, our study indicates the ROS-Nrf2 pathway mediates the development of TGF-β1-induced EMT through the activation of Notch signaling.

SLC7A11 regulated by NRF2 modulates esophageal squamous cell carcinoma radiosensitivity by inhibiting ferroptosis

BACKGROUND

Solute carrier family 7 member 11(SLC7A11) is a component of cysteine/glutamate transporter, which plays a key role in tumor growth; however, its underlying effect on radiosensitivity in esophageal squamous cell carcinoma (ESCC) remains unclear. This study aimed to clarify SLC7A11's expression and correlation with nuclear expression of nuclear factor erythroid-2 (NRF2)-associated radioresistance in ESCC.

METHODS

We included 127 ESCC patients who received radical chemoradiotherapy. Immunohistochemical staining was used to detect SLC7A11 and NRF2 nuclear expression, and the relationship between clinicopathological characteristics and survival rates or therapy response were evaluated. Western blot, dual-reporter assays and Chromatin immunoprecipitation (ChIP)-sequencing were used to analyze their relationship in vitro. Their roles in radioresistance were then investigated through multiple validation steps.

RESULTS

NRF2 nuclear expression and SLC7A11 expression were overexpressed in ESCC tissues and were positively correlated with one another. NRF2 nuclear expression was significantly associated with tumor length, lymph node metastasis, and TNM stage, while SLC7A11 expression was associated with lymph node metastasis. Patients with high NRF2 nuclear expression and SLC7A11 expression had significantly shorter overall and progression-free survival, and poor treatment response. The multivariate model showed that NRF2 nuclear expression and SLC7A11 expression, sex and tumor location are independent prognostic factors. In vitro analysis confirmed that hyperactivation of NRF2 induced SLC7A11 expression by directly binding to its promoter region, promoting radioresistance, reducing radiotherapy-induced lipid peroxidation levels, PTGS2 expression, and radiotherapy-related ferroptosis morphologic features.

CONCLUSION

Our study reveals a connection between high SLC7A11 expression and NRF2 nuclear expression in patients with ESCC that was related to worse survival and poorer therapy outcomes. SLC7A11-mediated ferroptosis inhibition induced NRF2-associated radioresistance, highlighting potential of NRF2/SLC7A11/ferroptosis axis as future therapeutic targets against therapy resistance biomarker.

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.

Radiation Resistance: A Matter of Transcription Factors

Currently, radiation therapy is one of the standard therapies for cancer treatment. Since the first applications, the field of radiotherapy has constantly improved, both in imaging technologies and from a dose-painting point of view. Despite this, the mechanisms of resistance are still a great problem to overcome. Therefore, a more detailed understanding of these molecular mechanisms will allow researchers to develop new therapeutic strategies to eradicate cancer effectively. This review focuses on different transcription factors activated in response to radiotherapy and, unfortunately, involved in cancer cells’ survival. In particular, ionizing radiations trigger the activation of the immune modulators STAT3 and NF-κB, which contribute to the development of radiation resistance through the up-regulation of anti-apoptotic genes, the promotion of proliferation, the alteration of the cell cycle, and the induction of genes responsible for the Epithelial to Mesenchymal Transition (EMT). Moreover, the ROS-dependent damaging effects of radiation therapy are hampered by the induction of antioxidant enzymes by NF-κB, NRF2, and HIF-1. This protective process results in a reduced effectiveness of the treatment, whose mechanism of action relies mainly on the generation of free oxygen radicals. Furthermore, the previously mentioned transcription factors are also involved in the maintenance of stemness in Cancer Stem Cells (CSCs), a subset of tumor cells that are intrinsically resistant to anti-cancer therapies. Therefore, combining standard treatments with new therapeutic strategies targeted against these transcription factors may be a promising opportunity to avoid resistance and thus tumor relapse.

NRF2-mediated signaling is a master regulator of transcription factors in bovine granulosa cells under oxidative stress condition

Transcription factors (TFs) are known to be involved in regulating the expression of several classes of genes during folliculogenesis. However, the regulatory role of TFs during oxidative stress (OS) is not fully understood. The current study was aimed to investigate the regulation of the TFs in bovine granulosa cells (bGCs) during exposure to OS induced by H₂O₂ in vitro. For this, bGCs derived from ovarian follicles were cultured in vitro till their confluency and then treated with H₂O₂ for 40 min. Twenty-four hours later, cells were subjected to various phenotypic and gene expression analyses for genes related to TFs, endoplasmic reticulum stress, apoptosis, cell proliferation, and differentiation markers. The bGCs exhibited higher reactive oxygen species accumulation, DNA fragmentation, and endoplasmic reticulum stress accompanied by reduction of mitochondrial activity after exposure to OS. In addition, higher lipid accumulation and lower cell proliferation were noticed in H₂O₂-challenged cells. The mRNA level of TFs including NRF2, E2F1, KLF6, KLF9, FOS, SREBF1, SREBF2, and NOTCH1 was increased in H₂O₂-treated cells compared with non-treated controls. However, the expression level of KLF4 and its downstream gene, CCNB1, were downregulated in the H₂O₂-challenged group. Moreover, targeted inhibition of NRF2 using small interference RNA resulted in reduced expression of KLF9, FOS, SREBF2, and NOTCH1 genes, while the expression of KLF4 was upregulated. Taken together, bovine granulosa cells exposed to OS exhibited differential expression of various transcription factors, which are mediated by the NRF2 signaling pathway.

The intricacies of NRF2 regulation in cancer

The complex role of NRF2 in the context of cancer continues to evolve. As a transcription factor, NRF2 regulates various genes involved in redox homeostasis, protein degradation, DNA repair, and xenobiotic metabolism. As such, NRF2 is critical in preserving cell function and viability, particularly during stress. Importantly, NRF2 itself is regulated via a variety of mechanisms, and the mode of NRF2 activation often dictates the duration of NRF2 signaling and its role in either preventing cancer initiation or promoting cancer progression. Herein, different modes of NRF2 regulation, including oxidative stress, autophagy dysfunction, protein-protein interactions, and epigenetics, as well as pharmacological modulators targeting this cascade in cancer, are explored. Specifically, how the timing and duration of these different mechanisms of NRF2 induction affect tumor initiation, progression, and metastasis are discussed. Additionally, progress in the discovery and development of NRF2 inhibitors for the treatment of NRF2-addicted cancers is highlighted, including modulators that inhibit specific NRF2 downstream targets. Overall, a better understanding of the intricate nature of NRF2 regulation in specific cancer contexts should facilitate the generation of novel therapeutics designed to not only prevent tumor initiation, but also halt progression and ultimately improve patient wellbeing and survival.

Corilagin induces apoptosis and autophagy in NRF2‑addicted U251 glioma cell line

Corilagin, extracted from the Euphorbiaceae and Phyllanthus plants, inhibits the growth of a number of types of tumors. Compared with temozolomide, the traditional chemotherapy drug, corilagin has demonstrated stronger antitumor activity. However, the pharmaceutical mechanism of corilagin in glioma remains unclear. Nuclear factor erythroid 2 like 2 (NFE2L2 or NRF2) is positively associated with several types of tumor including glioma. In the present study, NRF2 expression was higher in glioma tissues compared with non-glioma specimens. Therefore, it was hypothesized that corilagin targets NRF2 regulation of U251 cell apoptosis. The present study used Hoechst 33258 staining to demonstrate that corilagin induced glioma cell apoptosis and observed that the expression of the apoptosis-related gene Bcl-2 was reduced. In addition, corilagin induced autophagy and promoted the conversion of light chain 3 (LC3) protein from LC3I to LC3II. NRF2 expression was downregulated by corilagin stimulation. Furthermore, the gene expression pattern following knockdown of NRF2 in U251 cells using siRNA was consistent with corilagin stimulation. Therefore, it was preliminarily concluded that corilagin induces apoptosis and autophagy by reducing NRF2 expression.

Effects of neutron radiation on Nrf2-regulated antioxidant defense systems in rat lens

Accumulating evidence suggests that ionizing radiation (IR)-induced cataract may be associated with oxidative stress. Nuclear factor erythroid 2-related factor 2 (Nrf2) serves as a master regulator of the antioxidant defense system against oxidative stress. The present study aimed to investigate the effects of different doses of neutron radiation on the Nrf2-reegulated antioxidant defense system in rat lens and assess the status of oxidative stress. A total of 24 SD rats were randomly divided into the following four groups: i) Control group; iis) 0.4 Sv group; iii) 1.2 Sv group; and iv) 3.6 Sv group. The rats were sacrificed 7 days after radiation and lenses were dissected for histological, biochemical (malondialdehyde, glutathione and superoxide dismutase) and western blot (Nrf2, glutamate-cysteine ligase catalytic subunit and heme oxygenase 1) analyses. The morphological features of the lenses remained intact in the 0.4 Sv, 1.2 Sv and control groups, whilst the lenses in the 3.6 Sv group exhibited injuries. Results from the TUNEL assay demonstrated apparent apoptosis in lens epithelial cells following 3.6 Sv neutron radiation whereas sparse apoptosis was observed following 0.4 Sv and 1.2 Sv radiation. Malondialdehyde levels were reduced in the 0.4 Sv and 1.2 Sv groups but increased in the 3.6 Sv group, compared with those in the control group. Conversely, glutathione expression and the activity of superoxide dismutase were higher in the 0.4 Sv and 1.2 Sv groups, but lower in the 3.6 Sv group, compared with those in the control group. In addition, the total and nuclear protein levels of Nrf2 were increased following neutron radiation compared with those in the control group, though the Nrf2 protein levels decreased in the 3.6 Sv group compared with those in the 1.2 Sv group. The levels of glutamate-cysteine ligase catalytic subunit and heme oxygenase 1, downstream antioxidant enzymes of Nrf2, demonstrated the same profile as that in Nrf2. Taken together, the results of the present study suggest that neutron radiation affects Nrf2-regulated antioxidant systems in a two-stage process. Namely, the induction phase for low-dose radiation and regression phase for high-dose radiation. Therefore, it was hypothesized that activation and enhancement of the Nrf2-regulated antioxidant system may be useful in preventing or delaying IR-induced cataract, which may be extended even for other diseases associated with oxidative stress.

Rosmarinic acid attenuates chromium-induced hepatic and renal oxidative damage and DNA damage in rats

Hexavelant chromium (Cr (V1)) is a widely distributed environmental pollutant inducing damage in different organs of human and animals. The current study was designed to investigate the mechanistic role of rosmarinic acid (RA) to diminish chromium-induced hepatorenal oxidative damage and preneoplastic lesions in rats. Plant material was collected, identified, and extracted. The isolated RA was elucidated relying on the nuclear magnetic resonance spectroscopic data. Twenty-eight male Wistar rats received the following materials daily via oral gavage for 60 days; (Gp1): normal saline, (Gp2) 25 mg/kg.bwt RA, (Gp3) 10 mg/kg.bwt potassium dichromate (K2 Cr2 O7 ), (Gp4) K2 Cr2 O7  + RA. All rats were euthanized at the end of the experiment by cervical dislocation and the liver and kidney were collected. Prolonged continuous exposure of rats to chromium-induced oxidant/antioxidant imbalance manifested by significant elevation of malondialdehyde with reduction in reduced glutathione levels. Remarkable histopathological alterations in the liver and kidney tissue sections were recorded and confirmed by overexpression of the immunohistochemical staining of caspase-3, placental glutathione-S transferase, proliferating cell nuclear antigen together with a significant downregulation of nuclear factor erythroid-2 related factor 2 (Nrf2) gene and upregulation of nibrin gene. Observable improvements in the entire toxicopathological parameters were recorded in group cotreated with RA. Our findings revealed that Cr-induced preneoplastic lesions on the liver and kidney tissues of rats when exposed daily for long period of time, as well as confirmed the ability of RA to alleviate this toxicity through upregulation of Nrf2 pathway and its powerful antioxidant effects.

Allyl isothiocyanate treatment alleviates chronic obstructive pulmonary disease through the Nrf2-Notch1 signaling and upregulation of MRP1

AIMS

Chronic obstructive pulmonary disease (COPD) is a disease with high morbidity and mortality worldwide, which can cause serious social and economic burdens. Allyl isothiocyanate (AITC) is one of the most common natural isothiocyanates and has been shown to have anti-inflammatory and antioxidant biological activities. The purpose of this study was to investigate whether AITC regulated Multidrug resistance-associated protein 1 (MRP1), reactive oxide species (ROS) and reduced glutathione (GSH) levels via Nrf2 and Notch1 signaling pathways to treat COPD and whether there was an interaction between these two pathways.

MAIN METHODS

Lung function indexes and histopathological changes in mice were determined by lung function instrument and HE staining, respectively. The protein expression was analyzed using immunohistochemistry and Western blotting. The mRNA expression was measured by RT-PCR in human bronchial epithelial cell line 16HBE. The contents of ROS, GSH and GSSG were detected by kits in 16HBE cells.

KEY FINDINGS

The protein expression of Notch1, Hes1, MRP1, Nrf2, and HO-1 in lung tissues of WT mice and untransfected cells were significantly down-regulated in COPD, then significantly ameliorated in treatment groups. The protein expression of MRP1, Notch1 and Hes1 in lung tissues of Nrf2^-/- mice were markedly reduced. There was a significant reduction in expression of Nrf2, HO-1 and MRP1 in si-Notch1 transfected cells. Pretreatment with AITC markedly improved oxidative stress and GSH-redox disorder in COPD.

SIGNIFICANCE

Our study demonstrates that there is a potential interaction between Nrf2 and Notch1 signaling pathways during treatment of COPD.

The potential effect of methylseleninic acid (MSA) against γ-irradiation induced testicular damage in rats: Impact on JAK/STAT pathway

This study suggested that methylseleninic acid (MSA) could respond to the inflammatory signaling associated with ionizing radiation-induced testicular damage. Mature male rats were divided into four groups: negative control, whole body γ-irradiated (IRR) (5 Gy), MSA (0.5 mg/kg, daily for nine consecutive days), and MSA+ IRR groups. MSA increased serum testosterone level and testicular glutathione peroxidase (GPx) as well as decreased the percentage of sperm abnormalities. Radiation prompted inflammatory signaling in the testes through increasing phospho-janus kinase1 (p-JAK1), phospho-signal transducers and activators of transcription 3 (p-STAT3) protein expressions. This induced increment in the inflammatory markers including nuclear factor- kappa B (NF-κB) and interleukin-1beta (IL-1β) levels. Also, radiation induced elevation of nitric oxide (NO) and malondialdhyde (MDA) levels with consequent reduction in testicular reduced glutathione level (GSH) and superoxide dismutase (SOD) activity. MSA significantly counteracted the radiation effect on testicular nuclear factor erythroid-2-related factor-2 (Nrf2) and suppressor of cytokine signaling (Socs3) protein expressions. In summary, this investigation proposed that MSA preserved spermatogenesis through increasing testosterone levels and GPx activity. Additionally, it diminished testicular inflammation by increasing of Nrf2 and Socs3 levels leading to reducing of p-JAK1, p-STAT3 and NF-κB levels. Histopathological examination results of testicular tissues showed a coincidence with the biochemical analysis.

Phytochemical profile and protective effect of Ocimum basilicum aqueous extract in doxorubicin/irradiation-induced testicular injury

Objectives

Combined chemotherapy and radiotherapy usually associated with various comorbidities especially on rapidly proliferating cells as testis. This study aimed to characterize main constituents of Ocimum basilicum L. (OB) aqueous extract and examine its protective effect on doxorubicin/irradiation (DOXO/IR)-induced testicular injury in rats.

Methods

Spectrophotometric analysis showed considerable amount of polyphenolic (146.31 µg/mg) and flavonoid contents (28.63 µg/mg); UPLC-ESI-MS/MS analysis revealed that the major flavonoid was apigenin-O-glucoside (7.53%) followed by luteolin (5.94%), while rosmarinic acid was the major polyphenolic (15.76%) followed by caftaric acid (9.39%); rutin and querctin were also present and were quantified using high-performance liquid chromatography. Administration of OB extract (200 mg/kg per day; p.o.) to DOXO/IR rats resulted in marked improvement of associated testicular damage.

Key findings

Ocimum basilicum L. significantly decreased testicular levels of nuclear factor-kappa B and B-cell lymphoma-2 (Bcl2)-associated protein X, along with caspase-3 immunohistochemical staining. In addition, OB elevated testicular total antioxidant capacity, nuclear erythroid-related factor-2, Bcl2 and testosterone contents and Ki-67 immunohistochemical staining. Such changes were also accompanied by restoration of testicular architecture.

Conclusions

The study highlights the protective role of OB aqueous extract in hampering most of the harmful chemotherapy/radiotherapy-induced outcomes via its antioxidant, antiapoptotic and cell regeneration abilities. Such findings may offer an incentive in expanding its use during chemotherapy and radiotherapy.

NRF2 orchestrates the redox regulation induced by radiation therapy, sustaining embryonal and alveolar rhabdomyosarcoma cells radioresistance

PURPOSE

Tumor cells generally exhibit higher levels of reactive oxygen species (ROS), however, when stressed, tumor cells can undergo a process of 'Redox Resetting' to acquire a new redox balance with stronger antioxidant systems that enable cancer cells to become resistant to radiation therapy (RT). Here, we describe how RT affects the oxidant/antioxidant balance in human embryonal (RD) and alveolar (RH30) rhabdomyosarcoma (RMS) cell lines, investigating on the molecular mechanisms involved.

METHODS

Radiations were delivered using an x-6 MV photon linear accelerator and their effects were assessed by vitality and clonogenic assays. The expression of specific antioxidant-enzymes, such as Superoxide Dismutases (SODs), Catalase (CAT) and Glutathione Peroxidases 4 (GPx4), miRNAs (miR-22, -126, -210, -375, -146a, -34a) and the transcription factor NRF2 was analyzed by quantitative polymerase chain reaction (q-PCR) and western blotting. RNA interference experiments were performed to evaluate the role of NRF2.

RESULTS

Doses of RT higher than 2 Gy significantly affected RMS clonogenic ability by increasing ROS production. RMS rapidly and efficiently brought back ROS levels by up-regulating the gene expression of antioxidant enzymes, miRNAs as well as of NRF2. Silencing of NRF2 restrained the RMS ability to counteract RT-induced ROS accumulation, antioxidant enzyme and miRNA expression and was able to increase the abundance of γ-H2AX, a biomarker of DNA damage, in RT-treated cells.

CONCLUSIONS

Taken together, our data suggest the strategic role of oxidant/antioxidant balance in restraining the therapeutic efficiency of RT in RMS treatment and identify NRF2 as a new potential molecular target whose inhibition might represent a novel radiosensitizing therapeutic strategy for RMS clinical management.

Pathological effects of ionizing radiation: endothelial activation and dysfunction

The endothelium, a tissue that forms a single layer of cells lining various organs and cavities of the body, especially the heart and blood as well as lymphatic vessels, plays a complex role in vascular biology. It contributes to key aspects of vascular homeostasis and is also involved in pathophysiological processes, such as thrombosis, inflammation, and hypertension. Epidemiological data show that high doses of ionizing radiation lead to cardiovascular disease over time. The aim of this review is to summarize the current knowledge on endothelial cell activation and dysfunction after ionizing radiation exposure as a central feature preceding the development of cardiovascular diseases.

Targeting the cell signaling pathway Keap1-Nrf2 as a therapeutic strategy for adenocarcinomas of the lung

INTRODUCTION

Kelch-like ECH associated protein 1/Nuclear factor erythroid 2-like factor 2 (Keap1-Nrf2) signaling plays a pivotal role in response to oxidative stress in lung cancer. Mutations in KEAP1/NFE2L2 genes always cause persistent Nrf2 activation in lung cancer cells that confer therapeutic resistance and aggressive tumorigenic activity, dictating either poor prognosis or short duration of response to chemotherapy in clinical observations. Areas covered: We provide a review of the mechanisms underlying the regulation of Keap1-Nrf2 at different stages, including genetic mutations, epigenetic modifications, translational/post-translational alterations, and protein-protein interactions. Based on the current knowledge, we discuss the possibilities of intervening Keap1-Nrf2 in lung adenocarcinoma as a therapeutic target. Expert opinion: It is prevalently conceived that Keap1-Nrf2 signaling plays different roles at diverse stages of cancer. Although various Nrf2 or Keap1 inhibitors have been reported during the last decades, none of these inhibitors are currently under clinical studies or in clinical applications, suggesting that sole inhibition of Nrf2 might not be sufficient to suppress tumor growth. On the basis of current studies, we suggest that the rational combination of Nrf2 suppression with chemical agents which cause enhanced oxidative imbalance or abnormal metabolism would be promising in the treatment of lung adenocarcinoma.

Aberration of Nrf2‑Bach1 pathway in colorectal carcinoma; role in carcinogenesis and tumor progression

Nrf2 and Bach1 are important transcriptional factors that protect against reactive oxygen species (ROS). Although aberration of these molecules was associated with malignant transformation and progression, their aberration pattern in colorectal carcinoma (CRC) is not yet fully studied. In this study, Nrf2 and Bach1 were immunohistochemically examined in 93 formalin-fixed paraffin-embedded blocks of colonic tumors (65 carcinoma with their corresponding surgical margins and 28 adenomas). Nrf2 expression was gradually increased in the apparently normal mucosa (57 ± 41)-adenoma (90 ± 36)-carcinoma (198 ± 78) direction and only showed significant higher mean of expression in CRC with brisk inflammatory peritumoral response. The mean of Bach1 expression was highest in apparently normal colonic mucosa (267 ± 16), lowest in adenoma (53 ± 31) and high in carcinoma tissues (194 ± 93). Significant higher mean of expression was detected in carcinoma with: LN metastasis (p = 0.04), lymphovascular invasion (p = 0.024); perineural invasion (p = 0.03) and advanced pathological stage (p < 0.001). Significant higher mean of expression of Nrf2 and Bach1 was detected in adenoma specimens with high grade dysplasia (p = 0.016 and p = 0.024) respectively. In conclusion, Nfr2 and Bach1 expression are altered in CRC but in different way. Nrf2 is gradually increasing from normal mucosa to adenoma and was highest in carcinoma but was not associated with features of tumor invasiveness. Bach1 was highest in normal mucosa; less in adenoma then increased in carcinoma and was associated with features of tumor invasiveness and metastasis. This may indicate a possible role of Nrf2 in CRC carcinogenesis and a role of Bach1 in CRC progression.

Triptolide enhances chemotherapeutic efficacy of antitumor drugs in non-small-cell lung cancer cells by inhibiting Nrf2-ARE activity

Non-small cell lung cancer (NSCLC) has a high mortality rate worldwide. Various treatments strategies have been used against NSCLC including individualized chemotherapies, but innate or acquired cancer cell drug resistance remains a major obstacle. Recent studies revealed that the Kelch-like ECH associated protein 1/Nuclear factor erythroid 2-related factor 2 (Keap1/Nrf2) pathway is intimately involved in cancer progression and chemoresistance. Thus, antagonizing Nrf2 would seem to be a viable strategy in cancer therapy. In the present study a traditional Chinese medicine, triptolide, was identified that markedly inhibited expression and transcriptional activity of Nrf2 in various cancer cells, including NSCLC and liver cancer cells. Consequently, triptolide made cancer cells more chemosensitivity toward antitumor drugs both in vitro and in a xenograft tumor model system using lung carcinoma cells. These results suggest that triptolide blocks chemoresistance in cancer cells by targeting the Nrf2 pathway. Triptolide should be further investigated in clinical cancer trials.

Metformin reverses the resistance mechanism of lung adenocarcinoma cells that knocks down the Nrf2 gene

The nuclear factor, erythroid 2 like 2 (Nrf2)/antioxidant response element (ARE) pathway has an important role in the drug resistance of adenocarcinoma, and may act via different mechanisms, including the mitogen-activated protein kinase (MAPK) pathway. However, it has remained elusive whether metformin affects Nrf2 and regulates Nrf2/ARE in adenocarcinoma. In the present study, reverse-transcription quantitative polymerase chain reaction, cell transfection, western blot analysis, a Cell Counting kit-8 assay and apoptosis detection were used to investigate the above in the A549 cell line and cisplatin-resistant A549 cells (A549/DDP). The results indicated that Nrf2, glutathione S-transferase α 1 (GSTA1) and ATP-binding cassette subfamily C member 1 (ABCC1) were dose-dependently reduced by metformin, and that the effect in A549 cells was greater than that in A549/DDP cells. Treatment with metformin decreased the proliferation and increased the apoptosis of A549 cells to a greater extent than that of A549/DDP cells, and the effect was dose-dependent. After transfection of A549/DDP cells with Nrf2 short hairpin RNA (shRNA), GSTA1 and ABCC1 were markedly decreased, compared with the shRNA-control group of A549/DDP, and low dose-metformin reduced the proliferation and increased apoptosis of A549/DDP cells. Metformin inhibited the Akt and extracellular signal-regulated kinase (ERK)1/2 pathways in A549 cells and activated the p38 MAPK and c-Jun N-terminal kinase (JNK) pathways. Furthermore, in the presence of metformin, inhibitors of the p38 MAPK and JNK signaling pathway at different concentrations did not affect the levels of Nrf2, but inhibitors of the Akt and ERK1/2 pathway at different doses reduced the expression of Nrf2. In addition, inhibitors of p38 MAPK and JNK did not affect the effect of metformin on Nrf2, while inhibitors of Akt and ERK1/2 dose-dependently enhanced the inhibitory effects of metformin in A549 cells. In conclusion, metformin inhibits the phosphoinositide-3 kinase/Akt and ERK1/2 signaling pathways in A549 cells to reduce the expression of Nrf2, GSTA1 and ABCC1. Metformin also reverses the resistance of A549/DDP cells to platinum drugs, inhibits the proliferation and promotes apoptosis of drug-resistant cells. These results may provide a theoretical basis and therapeutic targets for the clinical treatment of tumors.

Di-(2-ethylhexyl) phthalate (DEHP)-induced testicular toxicity through Nrf2-mediated Notch1 signaling pathway in Sprague-Dawley rats

Di-(2-ethylhexyl) phthalate (DEHP) is an environmental endocrine disruptor widely used in China that is harmful to the male reproductive system. Many studies have shown that DEHP causes testicular toxicity through oxidative stress, but the specific mechanism is unknown. Because the Notch pathway is a key mechanism for regulating cell growth and proliferation, we investigated whether Notch is involved in DEHP-induced testicular toxicity and whether vitamins E and C could rescue testicular impairment in Sprague-Dawley (SD) rats. Compared with the control group, we found that DEHP exposure induced testicular toxicity through oxidative stress injury, and it decreased the testosterone level (P < .01) and upregulated nuclear factor-erythroid 2 related factor (Nrf2) expression (P < .01). Therefore, because oxidative stress might be the initiating factor of DEHP-induced testicular toxicity, treatment with the antioxidant vitamins E and C activated the Notch1 signaling pathway in the testis and in Leydig cells. Treatment with vitamins E and C normalized the oxidative stress state after DEHP exposure and restored testicular development to be similar to the control group. In summary, antioxidant vitamins E and C may be used to treat DEHP-induced testicular toxicity.

Migration and invasion in B16-F10 mouse melanoma cells are regulated by Nrf2 inhibition during treatment with ionizing radiation

Nuclear factor erythroid 2-related factor 2 (Nrf2) serves a critical role in carcinogenesis. The present study examined the effect of Nrf2 on the proliferation and invasion of melanoma cells that were treated with ionizing radiation. B16-F10 mouse melanoma cells were exposed to various doses of ionizing radiation for different time periods. Small interfering (si)RNAs targeting Nrf2 were transfected into B16-F10 cells, and cell proliferation, invasion and apoptosis were detected by Transwell, MTT or western blot assays. The expression of Nrf2 and its downstream heme oxygenase 1 (HO-1) was analyzed by reverse transcription-quantitative polymerase chain reaction (RT-qPCR) and western blotting. HO-1 activity was also examined. Ionizing radiation stimulated Nrf2 expression, increased caspase-3 expression, and reduced the viability, migration and invasion of B16-F10 mouse melanoma cells. Transfection with Nrf2 siRNA was able to inhibit Nrf2 and HO-1 expression in B16-F10 mouse melanoma cells that were treated by ionizing radiation. Inhibition of Nrf2 further reduced cell viability, invasion and migration, and elevated caspase-3 expression in B16-F10 mice melanoma cells that were treated by ionizing radiation. In summary, treatment with ionizing radiation was able to stimulate Nrf2 expression and regulate cell viability, invasion and migration of B16-F10 cells. A combination of Nrf2 knockdown and ionizing radiation treatment exerted a synergistic effect on migration, invasion and apoptosis in B16-F10 murine melanoma cells.

Suppression of radiation-induced migration of non-small cell lung cancer through inhibition of Nrf2-Notch Axis

Nuclear factor E2 related factor 2 (Nrf2) is a transcription factor that is associated with tumor growth and resistance to radiation. The canonical Notch signaling pathway is also crucial for maintaining non-small cell lung cancer (NSCLC). Aberrant Nrf2 and Notch signaling has repeatedly been showed to facilitate metastasis of NSCLC. Here, we show that radiation induce Nrf2 and Notch1 expression in NSCLC. Knockdown of Nrf2 enhanced radiosensitivity of NSCLC and reduced epithelial-to-mesenchymal transition. Importantly, we found that knockdown of Nrf2 dramatically decreased radiation-induced NSCLC invasion and significantly increased E-cadherin, but reduced N-cadherin and matrix metalloproteinase (MMP)-2/9 expression. We found that Notch1 knockdown also upregulated E-cadherin and suppressed N-cadherin expression. Nrf2 contributes to NSCLC cell metastatic properties and this inhibition correlated with reduced Notch1 expression. These results establish that Nrf2 and Notch1 downregulation synergistically inhibit radiation-induced migratory and invasive properties of NSCLC cells.

Coroglaucigenin enhances the radiosensitivity of human lung cancer cells through Nrf2/ROS pathway

Seven cardenolides isolated from the ethanol extract of the stems of Calotropis gigantea were evaluated in vitro against human cancer cells and the structure-activity relationships were discussed. The results demonstrated that a compound, named CGN (coroglaucigenin), had better anti-proliferative activity with the IC50 value less than 6 μM among these compounds. Further, we found that CGN displayed much lower cytotoxicity to normal lung epithelial cells (BEAS-2B) than cancer cells (A549). Especially, our results demonstrated that treatment with CGN (1 μM) combined with X-ray irradiation induced higher radiosensitivity in human lung cancer cells (A549, NCI-H460, NCI-H446) but not in BEAS-2B. The expression levels of nuclear transcription factor Nrf2 and Nrf2-driven antioxidant molecule NQO-1 reduced in A549 cells after combined treatment compared to the radiation only. However, CGN had no toxicity and the levels of antioxidant molecules expression were higher in BEAS-2B cells when given the similar treatment as A549 cells. These results suggest that CGN is a very promising potential sensitizer for cancer radiotherapy, which not only inhibits the proliferation of cancer cells but also enhances the radiosensitivity of cancer cells through suppressing the expression of antioxidant molecules while there is no influence for normal cells.

Cigarette smoke enhances initiation and progression of lung cancer by mutating Notch1/2 and dysregulating downstream signaling molecules

Lung cancer is the primary cause of cancer related deaths in the western world and smoking significantly increases the risk of developing lung cancer. Smoking enhances lung cancer initiation and progression. The effects of cigarette smoke on lung cancer are mediated by the presence of highly mutagenic substances, including nicotine, leading to mutations in oncogenes and tumor suppressor genes. An emerging pathway in cancer is the Notch signaling pathway which is essential for embryonic lung development and tissue homeostasis. The role of Notch signaling in lung cancer remains controversial and no studies have directly linked cigarette exposure to mutations in Notch. Therefore, we investigated the direct effect of Notch signaling pathways on cigarette-induced lung tumors and the correlation between smoking and mutations in Notch leading to altered downstream signaling. Human cell lines, mouse models and clinical lung cancer samples were utilized in this study. Cigarette-induced in vitro human lung cancer models and in vivo mouse models demonstrated strong effects of cigarette exposure on the Notch signaling pathway. Immunohistochemistry (IHC) of 50 clinical samples collected from smokers and non-smokers with and without lung cancer also demonstrated a link between smoking and changes in Notch signaling. Finally, 34 lung cancer samples analyzed through direct sequencing indicated smoking significantly increased small nucleotide polymorphisms (SNPs) in Notch 1 and 2 and specific SNPs significantly modulated expression levels of downstream signaling pathway molecules. Taken together, these results demonstrate a direct effect of smoking on the Notch signaling pathway leading to lung cancer initiation and progression.

Valproic Acid Sensitizes Hepatocellular Carcinoma Cells to Proton Therapy by Suppressing NRF2 Activation

Although efficacy of combined histone deacetylase (HDAC) inhibitors and conventional photon radiotherapy is being tested in clinical trials, their combined effect with proton beam radiotherapy has yet to be determined. Here, we compared combined effect of valproic acid (VPA), a class I and II HDAC inhibitor and antiepileptic drug with proton and photon irradiation in hepatocellular carcinoma (HCC) cells in vitro and in vivo. We found that VPA sensitized more Hep3B cells to proton than to photon irradiation. VPA prolonged proton-induced DNA damage and augmented proton-induced apoptosis. In addition, VPA further increased proton-induced production of intracellular reactive oxygen species and suppressed expression of nuclear factor erythroid-2-related factor 2 (NRF2), a key transcription factor regulating antioxidant response. Downregulation of NRF2 by siRNA transfection increased proton-induced apoptotic cell death, supporting NRF2 as a target of VPA in radiosensitization. In Hep3B tumor xenograft models, VPA significantly enhanced proton-induced tumor growth delay with increased apoptosis and decreased NRF2 expression in vivo. Collectively, our study highlights a proton radiosensitizing effect of VPA in HCC cells. As NRF2 is an emerging prognostic marker contributing to radioresistance in HCC, targeting NRF2 pathway may impact clinical outcome of proton beam radiotherapy.

Nrf2-Knockout Protects from Intestinal Injuries in C57BL/6J Mice Following Abdominal Irradiation with γ Rays

Radiation-induced intestinal injuries (RIII) commonly occur in patients who suffer from pelvic or abdominal cancer. Nuclear factor-erythroid 2-related factor 2 (Nrf2) is a key transcriptional regulator of antioxidant, and the radioprotective role of Nrf2 is found in bone marrow, lung, and intestine, etc. Here, we investigated the effect of Nrf2 knockout on radiation-induced intestinal injuries using Nrf2 knockout (Nrf2^-/-) mice and wild-type (Nrf2^+/+) C57BL/6J mice following 13 Gy abdominal irradiation (ABI). It was found that Nrf2 knockout promoted the survival of irradiated mice, protected the crypt-villus structure of the small intestine, and elevated peripheral blood lymphocyte count and thymus coefficients. The DNA damage of peripheral blood lymphocytes and the apoptosis of intestinal epithelial cells (IECs) of irradiated Nrf2^-/- mice were decreased. Furthermore, compared with that of Nrf2^+/+ mice, Nrf2 knockout increased the number of Lgr5⁺ intestinal stem cells (ISCs) and their daughter cells including Ki67⁺ transient amplifying cells, Villin⁺ enterocytes, and lysozyme⁺ Paneth cells. Nuclear factor-κB (NF-κB) was accumulated in the crypt base nuclei of the small intestine, and the mRNA expression of NF-κB target genes Bcl-2, uPA, and Xiap of the small intestine from irradiated Nrf2^-/- mice were increased. Collectively, Nrf2 knockout has the protective effect on small intestine damage following abdominal irradiation by prompting the proliferation and differentiation of Lgr5⁺ intestinal stem cells and activation of NF-κB.

A novel fine tuning scheme of miR-200c in modulating lung cell redox homeostasis

Oxidative stress induces miR-200c, the predominant microRNA (miRNA) in lung tissues; however, the antioxidant role and biochemistry of such induction have not been clearly defined. Therefore, a lung adenocarcinoma cell line (A549) and a normal lung fibroblast (MRC-5) were used as models to determine the effects of miR-200c expression on lung antioxidant response. Hydrogen peroxide (H₂O₂) upregulated miR-200c, whose overexpression exacerbated the decrease in cell proliferation, retarded the progression of cells in the G2/M-phase, and increased oxidative stress upon H₂O₂ stimulation. The expression of three antioxidant proteins, superoxide dismutase (SOD)-2, haem oxygenase (HO)-1, and sirtuin (SIRT) 1, was reduced upon H₂O₂ stimulation in miR-200c-overexpressed A549 cells. This phenomenon of increased oxidative stress and antioxidant protein downregulation also occurs simultaneously in miR-200c overexpressed MRC-5 cells. Molecular analysis revealed that miR-200c inhibited the gene expression of HO-1 by directly targeting its 3'-untranslated region. The downregulation of SOD2 and SIRT1 by miR-200c was mediated through zinc finger E-box-binding homeobox 2 (ZEB2) and extracellular signal-regulated kinase 5 (ERK5) pathways, respectively, where knockdown of ZEB2 or ERK5 decreased the expression of SOD2 or SIRT1 in A549 cells. LNA anti-miR-200c transfection in A549 cells inhibited the endogenous miR-200c expression, resulting in increased expressions of antioxidant proteins, reduced oxidative stress and recovered cell proliferation upon H₂O₂ stimulation. These findings indicate that miR-200c fine-tuned the antioxidant response of the lung cells to oxidative stress through several pathways, and thus this study provides novel information concerning the role of miR-200c in modulating redox homeostasis of lung.

Silencing of NRF2 Reduces the Expression of ALDH1A1 and ALDH3A1 and Sensitizes to 5-FU in Pancreatic Cancer Cells

Pancreatic cancer remains an intractable cancer with a poor five-year survival rate, which requires new therapeutic modalities based on the biology of pancreatic oncogenesis. Nuclear factor E2 related factor-2 (NRF2), a key cytoprotective nuclear transcription factor, regulates antioxidant production, reduction, detoxification and drug efflux proteins. It also plays an essential role in cell homeostasis, cell proliferation and resistance to chemotherapy. We aimed to evaluate the possibility that modulation of NRF2 expression could be effective in the treatment of pancreatic cancer cells. We investigated whether the depletion of NRF2 by using small interfering RNAs (siRNAs) is effective in the expression of biomarkers of pancreatic cancer stemness such as aldehyde dehydrogenase 1 family, member A1 (ALDH1A1) and aldehyde dehydrogenase 3 family, member A1 (ALDH3A1). NRF2 knockdown markedly reduced the expression of NRF2 and glutamate-cysteine ligase catalytic subunit (GCLC) in cell lines established from pancreatic cancers. NRF2 silencing also decreased the ALDH1A1 and ALDH3A1 expression. Furthermore, this NRF2 depletion enhanced the antiproliferative effects of the chemotherapeutic agent, 5-fluorouracil (5-FU) in pancreatic cancer cells.

Nrf2 and Notch Signaling in Lung Cancer: Near the Crossroad

The transcription factor Nrf2 (NF-E2 related factor 2) is a master regulator of the cell antioxidant response associated with tumor growth and resistance to cytotoxic treatments. In particular, Nrf2 induces upregulation of cytoprotective genes by interacting with the closely situated AREs (Antioxidant Response Elements) in response to endogenous or exogenous stress stimuli and takes part to several oncogenic signaling pathways. Among these, the crosstalk with Notch pathway has been shown to enhance cytoprotection and maintenance of cellular homeostasis, tissue organization by modulating cell proliferation kinetics, and stem cell self-renewal in several organs. The role of Notch and Nrf2 related pathways in tumorigenesis is highly variable and when they are both abnormally activated they can synergistically cause neoplastic proliferation by promoting cell survival, differentiation, invasion, and metastases. NFE2L2, KEAP1, and NOTCH genes family appear in the list of significantly mutated genes in tumors in both combined and individual sets, supporting the crucial role that the aberrant Nrf2-Notch crosstalk might have in cancerogenesis. In this review, we summarize current knowledge about the alterations of Nrf2 and Notch pathways and their reciprocal transcriptional regulation throughout tumorigenesis and progression of lung tumors, supporting the potentiality of putative biomarkers and therapeutic targets.

IL-6 controls resistance to radiation by suppressing oxidative stress via the Nrf2-antioxidant pathway in oral squamous cell carcinoma

Background:

In promoting tumour malignancy IL-6 signalling is considered to have an important role. However, the biological roles of IL-6 on radiosensitivity in oral squamous cell carcinoma (OSCC) remain largely unclear. The objective of this study is to determine the effects and molecular mechanisms of IL-6 on radiosensitivity in OSCC.

Methods:

Two OSCC cell lines, and OSCC tissue samples with radioresistant cells were used. We examined the effects of IL-6, or tocilizumab, a humanised anti-human IL-6 receptor antibody, or both on radiosensitivity and DNA damage after X-ray irradiation in vitro. In addition, we investigated the involvement of the Nrf2-antioxidant pathway in IL-6-mediated radioresistant mechanisms using OSCC cell lines and tissues.

Results:

Increased levels of IL-6 suppressed radiation-induced cell death, and the blockade of IL-6 signalling by tocilizumab sensitised tumour cells to radiation. The radioresistant effect of IL-6 was associated with decreased DNA damage after radiation. We also found that IL-6 promotes the activation of not only the downstream molecule STAT3 but also the Nrf2-antioxidant pathway, leading to a significant decrease in oxidative stress by upregulating Mn-SOD.

Conclusions:

These results indicate that the blockade of IL-6 signalling combined with conventional radiotherapy could augment the treatment response and survival rate in patients with radioresistant OSCC.

p62/SQSTM1-Dr. Jekyll and Mr. Hyde that prevents oxidative stress but promotes liver cancer

p62/SQSTM1 is a multifunctional signaling hub and autophagy adaptor with many binding partners, which allow it to activate mTORC1-dependent nutrient sensing, NF-κB-mediated inflammatory responses, and the NRF2-activated antioxidant defense. p62 recognizes polyubiquitin chains via its C-terminal domain and binds to LC3 via its LIR motif, thereby promoting the autophagic degradation of ubiquitinated cargos. p62 accumulates in many human liver diseases, including nonalcoholic steatohepatitis (NASH) and hepatocellular carcinoma (HCC), where it is a component of Mallory-Denk bodies and intracellular hyaline bodies. Chronic p62 elevation contributes to HCC development by preventing oncogene-induced senescence and death of cancer-initiating cells and enhancing their proliferation. In this review, we discuss p62-mediated signaling pathways and their roles in liver pathophysiology, especially NASH and HCC.

Expression of HIF-1α and P-gp in non-small cell lung cancer and the relationship with HPV infection

The aim of the study was to study the expression of hypoxia-inducible factor-1α (HIF-1α) and P-glycoprotein (P-gp) and analyze its correlation with human papillomavirus (HPV) infection. From January, 2012 to May, 2014, 72 cases of non-small cell lung cancer (NSCLC) pathologic tissue samples were selected from the study group. Fifty-four lung benign lesions were selected to serve as the control group. HIF-1α and P-gp expression levels were detected using immunohistochemistry. PCR was used to detect the expression of HPV genome employing specific primers for HPV 16 and 18 types. The results showed that there was 47.2 and 63.9% positive HIF-1α and P-gp expression in the study group. No P-gp or HIF-1α expression was detected in the control group. The results established a positive correlation between the expression of HIF-1α and P-gp. In the study group, the expression and differentiation degree of HIF-1α was related to lymphatic metastasis. The HIF-1α expression in the well-differentiated samples was lower than that in the moderate or poorly differentiated samples. HIF-1α expression in patients with lymphatic metastasis was higher than in patients without metastasis. The expression rate of P-gp in adenocarcinoma was higher than that in squamous carcinoma. The detection rate of HPV DNA was 45.83 and 3.70% in the study and control groups, respectively. The HPV infection and differentiation degree had relevance to lymphatic metastasis in the study group. The HPV DNA detection rate in the well-differentiated samples was lower than that in the moderate or poorly differentiated samples. The HPV DNA detection rate in patients with lymphatic metastasis was higher than that in patients with no lymphatic metastasis. There was a close link between HIF-1α, P-gp expression and NSCLC occurrence, and the development of multidrug resistance. In conclusion, the detection of HIF-1α and P-gp expression can effectively predict drug resistance during chemotherapy in NSCLC, and these proteins can be used in drug prognosis.

Emerging roles of Nrf2 signal in non-small cell lung cancer

Non-small cell lung cancer (NSCLC) causes considerable mortality in the world. Owing to molecular biological progress, treatments in adenocarcinoma have evolved revolutionarily while those in squamous lung cancer remain unsatisfied. Recent studies revealed high-frequency alteration of Kelch-like ECH-associated protein 1/nuclear factor erythroid 2-like factor 2 (Keap1/Nrf2) pathway within squamous lung cancer, attracting researchers to focus on this particular pathway. In NSCLC patients, deregulated Nrf2 signal is recognized as a common feature at both DNA and protein level. Emerging associations between Nrf2 and other pathways have been elucidated. MicroRNA was also implicated in the regulation of Nrf2. Agents activating or antagonizing Nrf2 showed an effect in preclinical researches, reflecting different effects of Nrf2 during tumor initiation and progression. Prognostic evaluation demonstrated a negative impact of Nrf2 signal on NSCLC patients’ survival. Considering the importance of Nrf2 signal in NSCLC, further studies are required in the future.