Activation of AKT pathway by Nrf2/PDGFA feedback loop contributes to HCC progression

Advances in Nrf2 Signaling Pathway by Targeted Nanostructured-Based Drug Delivery Systems

Nanotechnology has gained significant interest in various applications, including sensors and therapeutic agents for targeted disease sites. Several pathological consequences, including cancer, Alzheimer's disease, autoimmune diseases, and many others, are mostly driven by inflammation and Nrf2, and its negative regulator, the E3 ligase adaptor Kelch-like ECH-associated protein 1 (Keap1), plays a crucial role in maintaining redox status, the expression of antioxidant genes, and the inflammatory response. Interestingly, tuning the Nrf2/antioxidant response element (ARE) system can affect immune-metabolic mechanisms. Although many phytochemicals and synthetic drugs exhibited potential therapeutic activities, poor aqueous solubility, low bioavailability, poor tissue penetration, and, consequently, poor specific drug targeting, limit their practical use in clinical applications. Also, the therapeutic use of Nrf2 modulators is hampered in clinical applications by the absence of efficient formulation techniques. Therefore, we should explore the engineering of nanotechnology to modulate the inflammatory response via the Nrf2 signaling pathway. This review will initially examine the role of the Nrf2 signaling pathway in inflammation and oxidative stress-related pathologies. Subsequently, we will also review how custom-designed nanoscale materials encapsulating the Nrf2 activators can interact with biological systems and how this interaction can impact the Nrf2 signaling pathway and its potential outcomes, emphasizing inflammation.

Brucein D augments the chemosensitivity of gemcitabine in pancreatic cancer via inhibiting the Nrf2 pathway

Background

Gemcitabine (GEM) is the first-line chemotherapeutic drug used to treat pancreatic ductal adenocarcinoma carcinoma (PDAC), but chemoresistance is often encountered clinically. Nrf2, an oxidative stress responsive transcription factor, is an important contributor to chemoresistance and poor prognosis of PDAC. Brucein D (BD), a naturally occurring quassinoid, has been reported to exert anti-tumor effect in several cancers including PDAC. In this study, we aimed to investigate the efficacy of BD and the role of Nrf2 axes on the chemosensitivity of GEM and elucidate the underlying molecular mechanisms.

Methods

Analyses of clinical samples of PDAC and GEPIA database were first conducted to identify the expression of Nrf2 in PDAC. We then established cell lines with stable deletion of Nrf2 through transfecting lentivirus into PDAC cells. Quantitative real-time PCR (qRT-PCR) and Western blotting were performed to determine the expression of Nrf2 in these cell lines. The effects of BD and Nrf2 axes on PDAC cell proliferation, colony-formation, tumor growth and chemosensitivity were determined both in vitro and in vivo. Orthotopic xenograft and genetically engineered KPC mouse models of PDAC were used to evaluate the anti-pancreatic cancer effects of BD and GEM.

Results

Nrf2 was highly expressed in PDAC in the clinical samples and GEPIA analysis. Gain- and lost-function study demonstrated that Nrf2 affected the chemosensitivity of GEM on PDAC cells both in vitro and in vivo. We further found that BD effectively inhibited PDAC cell proliferation and enhanced the chemosensitivity of GEM. Mechanistic studies revealed that BD sensitized GEM in PDAC cells through the ubiquitin–proteasome-dependent degradation of Nrf2, and downregulating the Nrf2 pathway. Silencing of Nrf2 plus BD treatment resulted in more potent inhibitory effects of GEM. In contrast, Nrf2 activation attenuated the chemosensitivity of GEM, indicating that the action of BD was Nrf2 dependent. Finally, the efficacy of BD alone and in combination with GEM on PDAC was validated on both orthotopic xenograft and genetically engineered KPC mouse models.

Conclusions

BD was able to enhance the chemosensitivity of GEM in PDAC through inhibition of the Nrf2 pathway. Our experimental findings indicate that BD, a potent Nrf2 inhibitor, holds promise for further development into a novel adjuvant therapy for PDAC.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13046-022-02270-z.

Smart Fe3O4@ZnO Core-Shell Nanophotosensitizers Potential for Combined Chemo and Photodynamic Skin Cancer Therapy Controlled by UVA Radiation

Purpose

Photodynamic therapy (PDT) is a non-invasive therapeutic modality that is used for several types of cancer and involves three essential elements (light, photosensitizer (PS), and oxygen). However, clinical PS is limited by the low yield of reactive oxygen species (ROS) and a long retention time. Therefore, developing a low-cost PS that can significantly increase ROS yield in a short time is of utmost importance.

Methods

In this study, brusatol (Bru) was loaded on the surface of ultraviolet A (UVA)-responsive zinc oxide (ZnO)-coated magnetic nanoparticles (Fe₃O₄@ZnO-Bru). The PS was well characterized by transmission electron microscopy (TEM), Fourier Transform infrared spectroscopy (FTIR), a superconducting quantum interference device, and dynamic light scattering (DLS). 3-(4,5-Dimethyl-2-thiazolyl)-2,5-diphenyl-2-H-tetrazolium bromide (MTT) and Hoechst staining were used to determine the inhibitory effect of Fe₃O₄@ZnO-Bru on squamous cell carcinoma cells (SCC) with or without UVA radiation. Intracellular ROS levels and expression of the Nrf2 signaling pathway were also determined.

Results

FTIR showed that Bru was successfully loaded on Fe₃O₄@ZnO. Fe₃O₄@ZnO-Bru was superparamagnetic, and the zeta potential was 8.86 ± 0.77 mV. The Bru release behavior was controlled by UVA. Fe₃O₄@ZnO-Bru with UVA irradiation induced an increase of 48% ROS productivity compared to Fe₃O₄@ZnO-Bru without UVA irradiation, resulting in a strong inhibitory effect on SCC. Furthermore, Fe₃O₄@ZnO-Bru nanocomposites (Fe₃O₄@ZnO-Bru NCs) had nearly no toxic effect on healthy cells without UVA radiation. The released Bru could significantly inhibit the Nrf2 signaling pathway to reduce the activity of scavenging excess ROS in SCC.

Conclusion

In this study, Fe₃O₄@ZnO-Bru was successfully synthesized. PDT was combined with photochemotherapy, which exhibited a higher inhibitory effect on SCC. It can be inferred that Fe₃O₄@ZnO-Bru holds great potential for skin SCC therapy.

Nrf2 Transcriptional Activity Governs Intestine Development

Our recent findings indicate that Nrf2 transcriptional activity is essential in maintaining the proper large intestinal structure in adult mice. Here, we aimed to verify whether Nrf2-related intestine abnormalities stemmed from the early weaning or gestational periods. Therefore, we analyzed 4-day-old pups and embryos devoid of Nrf2 transcriptional activity (tKO) and their wild-type counterparts. We found significant changes in the intestinal structure of 4-day-old Nrf2 tKO pups including a longer colon, altered crypt distribution, and enlargement of the goblet cells with a markedly higher level of mucin 2. Tracing back the origin of these alterations, we observed that they appeared as early as day 14.5 of embryonic development, independently of sex. Importantly, in this period, we observed a significant increase in the Nrf2 level and a distinctive, untimely pattern of expression of the proliferation factor Ki67. At the latest stage of embryonic development, we detected a premature drop in the differentiation factor Notch1. We suspect that intestine abnormalities in mice lacking Nrf2 transcriptional activity stem from sex-independent disturbed intestinal cell proliferation and could be further exacerbated by altered differentiation. Summing up, we identified Nrf2 transcriptional activity as an important regulator of intestinal formation. It influences the hindgut cell proliferation and differentiation at different stages of embryonic development.

The role of polyphenols in overcoming cancer drug resistance: a comprehensive review

Chemotherapeutic drugs are used to treat advanced stages of cancer or following surgery. However, cancers often develop resistance against drugs, leading to failure of treatment and recurrence of the disease. Polyphenols are a family of organic compounds with more than 10,000 members which have a three-membered flavan ring system in common. These natural compounds are known for their beneficial properties, such as free radical scavenging, decreasing oxidative stress, and modulating inflammation. Herein, we discuss the role of polyphenols (mainly curcumin, resveratrol, and epigallocatechin gallate [EGCG]) in different aspects of cancer drug resistance. Increasing drug uptake by tumor cells, decreasing drug metabolism by enzymes (e.g. cytochromes and glutathione-S-transferases), and reducing drug efflux are some of the mechanisms by which polyphenols increase the sensitivity of cancer cells to chemotherapeutic agents. Polyphenols also affect other targets for overcoming chemoresistance in cancer cells, including cell death (i.e. autophagy and apoptosis), EMT, ROS, DNA repair processes, cancer stem cells, and epigenetics (e.g. miRNAs).

Development of targeted therapy of NRF2high esophageal squamous cell carcinoma

Esophageal squamous cell carcinoma (ESCC) is a deadly disease and one of the most aggressive cancers of the gastrointestinal tract. As a master transcription factor regulating the stress response, NRF2 is often mutated and becomes hyperactive, and thus causes chemo-radioresistance and poor survival in human ESCC. There is a great need to develop NRF2 inhibitors for targeted therapy of NRF2high ESCC. In this review, we mainly focus on three aspects, NRF2 inhibitors and their mechanisms of action, screening novel drug targets, and evaluation of NRF2 activity in the esophagus. A research strategy has been proposed to develop NRF2 inhibitors using human ESCC cells and mouse models.

Inhibition of the NRF2/KEAP1 Axis: A Promising Therapeutic Strategy to Alter Redox Balance of Cancer Cells

Significance: The nuclear factor erythroid 2-related factor 2/Kelch-like ECH-associated protein 1 (NRF2/KEAP1) pathway is a crucial and highly conserved defensive system that is required to maintain or restore the intracellular homeostasis in response to oxidative, electrophilic, and other types of stress conditions. The tight control of NRF2 function is maintained by a complex network of biological interactions between positive and negative regulators that ultimately ensure context-specific activation, culminating in the NRF2-driven transcription of cytoprotective genes. Recent Advances: Recent studies indicate that deregulated NRF2 activation is a frequent event in malignant tumors, wherein it is associated with metabolic reprogramming, increased antioxidant capacity, chemoresistance, and poor clinical outcome. On the other hand, the growing interest in the modulation of the cancer cells' redox balance identified NRF2 as an ideal therapeutic target. Critical Issues: For this reason, many efforts have been made to identify potent and selective NRF2 inhibitors that might be used as single agents or adjuvants of anticancer drugs with redox disrupting properties. Despite the lack of specific NRF2 inhibitors still represents a major clinical hurdle, the researchers have exploited alternative strategies to disrupt NRF2 signaling at different levels of its biological activation. Future Directions: Given its dualistic role in tumor initiation and progression, the identification of the appropriate biological context of NRF2 activation and the specific clinicopathological features of patients cohorts wherein its inactivation is expected to have clinical benefits, will represent a major goal in the field of cancer research. In this review, we will briefly describe the structure and function of the NRF2/ KEAP1 system and some of the most promising NRF2 inhibitors, with a particular emphasis on natural compounds and drug repurposing. Antioxid. Redox Signal. 34, 1428-1483.

CCL23 suppresses liver cancer progression through the CCR1/AKT/ESR1 feedback loop

With the ability to activate certain signaling pathways, chemokines and their receptors may facilitate tumor progression at key steps, including proliferation, immunomodulation, and metastasis. Nevertheless, their prognostic value and regulatory mechanism warrant thorough studies in liver cancer. Here, by screening the expression profiles of all known chemokines in independent liver cancer cohorts, we found that CCL23 was frequently downregulated at mRNA and protein levels in liver cancer. Decreased CCL23 correlated with shortened patient survival, enrichment of signatures related to cancer stem cell property, and metastatic potential. In addition to serving as a tumor suppressor through recruiting CD8⁺ T cell infiltration in liver cancer, CCL23 could repress cancer cell proliferation, stemness, and mobility. Mechanistically, the expression of CCL23 was transcriptionally regulated by ESR1. On the other hand, CCL23 could suppress the activation of AKT signaling and thus promote the expression of ESR1, forming a feedback loop in liver cancer cells. Collectively, these findings reveal that loss of CCL23 drives liver cancer progression by coordinating immune evasion and metastasis initiation. Targeting the ESR1/CCL23/CCR1/AKT regulatory axis could be an effective therapeutic strategy.

Elevated O-GlcNAcylation Promotes Malignant Phenotypes of Hypopharyngeal Squamous Cell Carcinoma by Stabilizing Nrf2 through Regulation of the PI3K/Akt Pathway

BACKGROUND AND PURPOSE

O-GlcNAcylation is a significant protein posttranslational modification with O-linked β-N-acetylglucosamine (GlcNAc) for intracellular signaling. Elevated O-GlcNAcylation contributes to cell proliferation, cell migration, cell apoptosis and signal transduction in various cancers. However, the expression level and functional role of O-GlcNAcylation in Hypopharyngeal Squamous Cell Carcinoma (HSCC) is not clearly elucidated. Nuclear factor erythroid-2-related factor 2 (Nrf2) is a master transcriptional factor that has been found to be aberrantly activated in HSCC. Here, we provide a molecular rationale between O-GlcNAcylation and Nrf2 in HSCC patients.

METHODS

The protein levels of O-GlcNAcylation and Nrf2 in HSCC tissues were detected by immunohistochemistry technique and western blot analysis. Then, O-GlcNAcylation knockdown HSCC cells were applied in this study. Cell proliferation was detected by CCK8, colony-forming analysis, and cell cycle assays. Cell migration and invasion ability was evaluated by transwell assays. Cell apoptosis was measured by TUNEL analysis.

RESULTS

O-GlcNAcylation was obviously up-regulated in HSCC tissues, which correlated with tumor size and lymph node metastasis. In addition, the protein level of Nrf2 was found to positively correlate with the expression of O-GlcNAcylation both in vivo and in vitro. Knockdown of O-GlcNAcylation significantly inhibited HSCC cell growth, suppressed cell migration, and promoted cell apoptosis, whereas overexpression of Nrf2 reversed these phenotypes. Mechanismly, the upregulation of O-GlcNAcylation promoted the phosphorylation of Akt, leading to the stabilization of Nrf2; this could be attenuated by inhibition of the PI3K/Akt signaling pathway.

CONCLUSION

Here, we provide a molecular association between O-GlcNAcylation and Nrf2 in HSCC patients, thus providing valuable therapeutic targets for the disease.

Antioxidative Stress: Inhibiting Reactive Oxygen Species Production as a Cause of Radioresistance and Chemoresistance

Radiotherapy and chemotherapy are the most effective nonsurgical treatments for cancer treatment. They usually induce regulated cell death by increasing the level of reactive oxygen species (ROS) in tumour cells. However, as intracellular ROS concentration increases, many antioxidant pathways are concurrently upregulated by cancer cells to inhibit ROS production, ultimately leading to drug resistance. Understanding the mechanism of antioxidant stress in tumour cells provides a new research direction for overcoming therapeutic resistance. In this review, we address (1) how radiotherapy and chemotherapy kill tumour cells by increasing the level of ROS, (2) the mechanism by which ROS activate antioxidant pathways and the subsequent cellular mitigation of ROS in radiotherapy and chemotherapy treatments, and (3) the potential research direction for targeted treatment to overcome therapeutic resistance.

NRF2 as a regulator of cell metabolism and inflammation in cancer

Nuclear factor erythroid 2-related factor 2 (NRF2) is a master transcriptional regulator of genes whose products defend our cells for toxic and oxidative insults. Although NRF2 activation may reduce cancer risk by suppressing oxidative stress and tumor-promoting inflammation, many cancers exhibit elevated NRF2 activity either due to mutations that disrupt the negative control of NRF2 activity or other factors. Importantly, NRF2 activation is associated with poor prognosis and NRF2 has turned out to be a key activator of cancer-supportive anabolic metabolism. In this review, we summarize the diverse roles played by NRF2 in cancer focusing on metabolic reprogramming and tumor-promoting inflammation.

NRF2 preserves genomic integrity by facilitating ATR activation and G2 cell cycle arrest

Nuclear factor erythroid 2-related factor 2 (NRF2) is a well-characterized transcription factor that protects cells against oxidative and electrophilic stresses. Emerging evidence has suggested that NRF2 protects cells against DNA damage by mechanisms other than antioxidation, yet the mechanism remains poorly understood. Here, we demonstrate that knockout of NRF2 in cells results in hypersensitivity to ionizing radiation (IR) in the presence or absence of reactive oxygen species (ROS). Under ROS scavenging conditions, induction of DNA double-strand breaks (DSBs) increases the NRF2 protein level and recruits NRF2 to DNA damage sites where it interacts with ATR, resulting in activation of the ATR-CHK1-CDC2 signaling pathway. In turn, this leads to G2 cell cycle arrest and the promotion of homologous recombination repair of DSBs, thereby preserving genome stability. The inhibition of NRF2 by brusatol increased the radiosensitivity of tumor cells in xenografts by perturbing ATR and CHK1 activation. Collectively, our results reveal a novel function of NRF2 as an ATR activator in the regulation of the cellular response to DSBs. This shift in perspective should help furnish a more complete understanding of the function of NRF2 and the DNA damage response.

Demethylation of the NRF2 Promoter Protects Against Carcinogenesis Induced by Nano-SiO2

Nano silicon dioxide (Nano-SiO₂) has been widely used in industries such as the field of biomedical engineering. Despite the existing evidence that Nano-SiO₂ exposure could induce oxidative stress and inflammatory responses in multiple organ systems, the carcinogenicity of Nano-SiO₂ exposure has rarely been investigated. Thus in this study, two types of human bronchial epithelial cell lines (16HBE and BEAS-2B) were selected as in vitro models to investigate the carcinogenicity of Nano-SiO₂. Our results revealed that Nano-SiO₂ induces a malignant cellular transformation in human bronchial epithelial cells according to the soft agar colony formation assay. The carcinogenesis induced by Nano-SiO₂ was also confirmed in nude mice. By using immunofluorescence assay and high-performance capillary electrophoresis (HPCE), we observed a genome-wide DNA hypomethylation induced by Nano-SiO₂. Besides the reduced enzyme activity of total DNMTs upon Nano-SiO₂ treatment, altered expression of DNMTs and methyl-CpG binding proteins were observed. Besides, we found that the expression of NRF2 was activated by demethylation of CpG islands within the NRF2 promoter region and the overexpression of NRF2 could alleviate the carcinogenesis induced by Nano-SiO₂. Taken together, our results suggested that Nano-SiO₂ induces malignant cellular transformation with a global DNA hypomethylation, and the demethylation of NRF2 promoter activates the expression of NRF2, which plays an important role in protecting against the carcinogenesis induced by Nano-SiO₂.

Long noncoding RNA LEF1-AS1 acts as a microRNA-10a-5p regulator to enhance MSI1 expression and promote chemoresistance in hepatocellular carcinoma cells through activating AKT signaling pathway

Long noncoding RNAs (lncRNAs) contribute to the development of hepatocellular carcinoma (HCC), which could regulate various HCC biological characteristics. Here, the study seeks to investigate the role of lncRNA LEF1-AS1 in HCC cell chemoresistance by regulating microRNA (miR)-10a-5p and Musashi1 (MSI1). The microarray-based analysis was employed to identify the HCC-related lncRNA-miRNA-gene regulatory network. Expression patterns of LEF1-AS1, miR-10a-5p, and MSI1 in the HCC cell lines, tissues were accessed by means of reverse transcription-quantitative polymerase chain reaction. Next, the interaction among LEF1-AS1, miR-10a-5p, and MSI1 in HCC was accessed by bioinformatics and dual-luciferase reporter gene assay. Then, the cell line resistant to cisplatin was established, which was then treated with sh/oe-lncRNA LEF1-AS1, miR-10a-5p-mimic, and oe/sh-MSI1 vectors alone or in combination. Afterward, the effect of LEF1-AS1, miR-10a-5p, and MSI1 on HCC cell chemoresistance, proliferation, and apoptosis was assessed. At last, in vivo experiments confirmed the role of MSI1 in tumor growth and chemoresistance in HCC. LEF1-AS1 might potentially affect the growth and chemoresistance of HCC cells by regulating miR-10a-5p and MSI1. LEF1-AS1 and MSI1 expression patterns were elevated, while miR-10a-5p was repressed in HCC tissues and cell lines. LEF1-AS1 combined to miR-10a-5p and regulated MSI1, thereby activating the protein kinase B (AKT) signaling pathway. Knockdown of LEF1-AS1 and MSI1 or elevation of miR-10a-5p compromised the proliferation of Huh7 cell line resistant to DDP and promoted its chemosensitivity and apoptosis. At last, these in vitro findings were also confirmed in vivo. Our results unraveled LEF1-AS1 acts as a miR-10a-5p modulator to promote chemoresistance of HCC cells by stimulating MSI1 and activating the AKT signaling pathway, which might provide a novel therapeutic target for HCC.

Molecular Mechanisms Underlying Hepatocellular Carcinoma Induction by Aberrant NRF2 Activation-Mediated Transcription Networks: Interaction of NRF2-KEAP1 Controls the Fate of Hepatocarcinogenesis

NF-E2-related factor 2 (NRF2) is a basic leucine zipper transcription factor, a master regulator of redox homeostasis regulating a variety of genes for antioxidant and detoxification enzymes. NRF2 was, therefore, initially thought to protect the liver from oxidative stress. Recent studies, however, have revealed that mutations in NRF2 cause aberrant accumulation of NRF2 in the nucleus and exert the upregulation of NRF2 target genes. Moreover, among all molecular changes in hepatocellular carcinoma (HCC), NRF2 activation has been revealed as a more prominent pathway contributing to the progression of precancerous lesions to malignancy. Nevertheless, how its activation leads to poor prognosis in HCC patients remains unclear. In this review, we provide an overview of how aberrant activation of NRF2 triggers HCC development. We also summarize the emerging roles of other NRF family members in liver cancer development.

Nrf2 Inhibitor, Brusatol in Combination with Trastuzumab Exerts Synergistic Antitumor Activity in HER2-Positive Cancers by Inhibiting Nrf2/HO-1 and HER2-AKT/ERK1/2 Pathways

The HER2-targeting antibody trastuzumab has shown effectiveness in treating HER2-positive breast and gastric cancers; however, its responses are limited. Currently, Nrf2 has been deemed as a key transcription factor in promoting cancer progression and resistance by crosstalk with other proliferative signaling pathways. Brusatol as a novel Nrf2 inhibitor has been deemed as an efficacious and safe drug candidate in cancer therapy. In this study, we firstly reported that brusatol exerted the growth-inhibitory effects on HER2-positive cancer cells by regressing Nrf2/HO-1 and HER2-AKT/ERK1/2 signaling pathways in these cells. More importantly, we found that brusatol synergistically enhanced the antitumor activity of trastuzumab against HER2-positive SK-OV-3 and BT-474 cells, which may be attributed to the inhibition of Nrf2/HO-1 and HER2-AKT/ERK1/2 signaling pathways. Furthermore, the synergistic effects were also observed in BT-474 and SK-OV-3 tumor xenografts. In addition, our results showed that trastuzumab markedly enhanced brusatol-induced ROS accumulation and apoptosis level, which could further explain the synergistic effects. To conclude, the study provided a new insight on exploring Nrf2 inhibition in combination with HER2-targeted trastuzumab as a potential clinical treatment regimen in treating HER2-positive cancers.

Hepatocellular carcinoma cell-derived extracellular vesicles encapsulated microRNA-584-5p facilitates angiogenesis through PCK1-mediated nuclear factor E2-related factor 2 signaling pathway

Hepatocellular carcinoma (HCC) is a fatal disease characterized by poor liver function with increasing morbidity and poor prognosis. Extracellular vesicles, released by different cells, have been associated with HCC development. Nevertheless, the mechanisms beyond extracellular vesicles in HCC remain uncharacterized. Therefore, the current study aimed to clarify the mechanism of pro-angiogenic microRNA-584-5p in hepatocellular carcinoma. Our results showed that miR-584-5p was highly-expressed in both cancer cells (Hep3B) and their extracellular vesicles. Hep3B and extracellular vesicles were then respectively co-cultured with human vascular endothelial cell line (Ea.hy926), and they both accelerated Ea.hy926 proliferation and migration. Ea.hy926 cells could internalize extracellular vesicles carrying microRNA-584-5p. Of note, microRNA-584-5p could bind to phosphoenolpyruvate carboxykinase 1 to promote nuclear factor E2-related factor 2. Moreover, silencing microRNA-584-5p was found to decline microvessel density, vascular endothelial growth factor A, and tumor growth in vivo and in vitro. Taken altogether, our findings demonstrated that extracellular vesicles-derived microRNA-584-5p promotes angiogenesis by inhibiting PCK1 -mediating NRF2 activation, which highlights the theoretical basis for potential treatments for HCC.

NRF2 activates growth factor genes and downstream AKT signaling to induce mouse and human hepatomegaly

BACKGROUND & AIMS

Hepatomegaly can be triggered by insulin and insulin-unrelated etiologies. Insulin acts via AKT, but how other challenges cause hepatomegaly is unknown.

METHODS

Since many hepatomegaly-inducing toxicants and stressors activate NRF2, we examined the effect of NRF2 activation on liver size and metabolism using a conditional allele encoding a constitutively active NRF2 variant to generate Nrf2Act-hep mice in which NRF2 is selectively activated in hepatocytes. We also used adenoviruses encoding variants of the autophagy adaptor p62/SQSTM1, which activates liver NRF2, as well as liver-specific ATG7-deficient mice (Atg7Δhep) and liver specimens from patients with hepatic sinusoidal obstruction syndrome (HSOS) and autoimmune hepatitis (AIH). RNA sequencing and cell signaling analyses were used to determine cellular consequences of NRF2 activation and diverse histological analyses were used to study effects of the different manipulations on liver and systemic pathophysiology.

RESULTS

Hepatocyte-specific NRF2 activation, due to p62 accumulation or inhibition of KEAP1 binding, led to hepatomegaly associated with enhanced glycogenosis, steatosis and G2/M cell cycle arrest, fostering hyperplasia without cell division. Surprisingly, all manipulations that led to NRF2 activation also activated AKT, whose inhibition blocked NRF2-induced hepatomegaly and glycogenosis, but not NRF2-dependent antioxidant gene induction. AKT activation was linked to NRF2-mediated transcriptional induction of PDGF and EGF receptor ligands that signaled through their cognate receptors in an autocrine manner. Insulin and insulin-like growth factors were not involved. The NRF2-AKT signaling axis was also activated in human HSOS- and AIH-related hepatomegaly.

CONCLUSIONS

NRF2, a transcription factor readily activated by xenobiotics, oxidative stress and autophagy disruptors, may be a common mediator of hepatomegaly; its effects on hepatic metabolism can be reversed by AKT/tyrosine kinase inhibitors.

LAY SUMMARY

Hepatomegaly can be triggered by numerous etiological factors, including infections, liver cancer, metabolic disturbances, toxicant exposure, as well as alcohol abuse or drug-induced hepatitis. This study identified the oxidative stress response transcription factor NRF2 as a common mediator of hepatomegaly. NRF2 activation results in elevated expression of several growth factors. These growth factors are made by hepatocytes and activate their receptors in an autocrine fashion to stimulate the accumulation of glycogen and lipids that lead to hepatocyte and liver enlargement. The protein kinase AKT plays a key role in this process and its inhibition leads to reversal of hepatomegaly.

Inhibition of Nrf2 might enhance the anti-tumor effect of temozolomide in glioma cells via inhibition of Ras/Raf/MEK signaling pathway

BACKGROUND

Glioblastoma (GBM) is the most common aggressive primary cancer occurring in the brain tissue. GBM accounts 16% of primary brain tumors and half of gliomas. Additionally, the incidence of GBM is increases with aging, and reaches the peak at the age of 75 to 84 years. The survival of patients with GBM remains at a low level, only less than 5% patients diagnosed with GBM survive for 5 years. Temozolomide (TMZ) is a DNA alkylating agent and is currently a first line chemotherapeutic treatment for GBM. TMZ combined with radiation therapy has been shown to prolong the overall survival (OS) to 14.6 months compared with 12.1 months for radiation therapy alone. NF-E2-related factor 2 (Nrf2) is a transcription factor that contains seven functional domains. The binding of Keap1 to Nrf2 is a central regulator of the cellular defense mechanism against environmental stresses.

METHODS

First, Nrf2 overexpression and inhibition models were constructed in U251 cells using transfection. The percentage of viable cells was detected using the MTT assay. Then, the expression of the HO-1 regulator was detected using qPCR, and the concentrations of oxidative stress related factors were detected using ELISAs. The levels of proteins related to oxidative stress and the Ras/Raf/MEK signaling pathway was detected using western blotting analysis.

RESULTS

We initially established Nrf2 inhibition and activation cell models in U251 cells and found that the inhibition of Nrf2 expression decreased the mRNA and protein levels of the anti-oxidative enzymes, as well as the secretion of these enzymes into the cellular microenvironment. These effects might be mediated by the inhibition of Ras/Raf/MEK signaling pathway, leading to the inhibition of cellular proliferation.

CONCLUSIONS

Inhibition of Nrf2 expression might enhance the effect of TMZ on the treatment of GBM and might be a new therapeutic strategy.

Astaxanthin Treatment Induces Maturation and Functional Change of Myeloid-Derived Suppressor Cells in Tumor-Bearing Mice

Myeloid-derived suppressor cells (MDSCs) are immature myeloid cells which accumulate in stress conditions such as infection and tumor. Astaxanthin (ATX) is a well-known antioxidant agent and has a little toxicity. It has been reported that ATX treatment induces antitumor effects via regulation of cell signaling pathways, including nuclear factor erythroid-derived 2-related factor 2 (Nrf2) signaling. In the present study, we hypothesized that treatment with ATX might induce maturation of MDSCs and modulate their immunosuppressive activity. Both in vivo and in vitro treatment with ATX resulted in up-regulation of surface markers such as CD80, MHC class II, and CD11c on both polymorphonuclear (PMN)-MDSCs and mononuclear (Mo)-MDSCs. Expression levels of functional mediators involved in immune suppression were significantly reduced, whereas mRNA levels of Nrf2 target genes were increased in ATX-treated MDSCs. In addition, ATX was found to have antioxidant activity reducing reactive oxygen species level in MDSCs. Finally, ATX-treated MDSCs were immunogenic enough to induce cytotoxic T lymphocyte response and contributed to the inhibition of tumor growth. This demonstrates the role of ATX as a regulator of the immunosuppressive tumor environment through induction of differentiation and functional conversion of MDSCs.

Overexpression of Nrf2 promotes colon cancer progression via ERK and AKT signaling pathways

PURPOSE

We investigated the expression of Nrf2 in colorectal cancer and its correlation with clinicopathological characteristics as well as mechanisms and roles of Nrf2 expression including cell signaling pathway, survival, proliferation, and migration.

METHODS

Nrf2 expression was measured in 12 and 30 different colorectal cancer (CRC) tissues by western blot (WB) and immunohistochemistry (IHC), respectively. SW480 cells were used for cell proliferation and cell migration tests. The correlation between the expression of Nrf2 and clinicopathologic parameters were evaluated using the chi-square or Fisher exact test. Data are expressed as the mean ± standard deviation for 3 independent experiments. P < 0.05 was considered statistically significant.

RESULTS

Analysis of WB demonstrated that Nrf2 proteins were increased in CRC tissues, and decreased in normal tissues. IHC staining showed that the Nrf2 expression was elevated in CRC tissues, compared to matched normal tissues. When SW480 cells were suppressed with small interfering RNA of Nrf2, cell viability was inhibited, and cell apoptosis was increased. These results were found along with suppression of the phosphorylated form of extracellular signal-regulated kinase 1/2 and AKT.

CONCLUSION

This study suggests that overexpression of Nrf2 may be related to carcinogenesis and progression of CRC.

Potential Applications of NRF2 Modulators in Cancer Therapy

The nuclear factor erythroid 2-related factor 2 (NRF2)-Kelch-like ECH-associated protein 1 (KEAP1) regulatory pathway plays an essential role in protecting cells and tissues from oxidative, electrophilic, and xenobiotic stress. By controlling the transactivation of over 500 cytoprotective genes, the NRF2 transcription factor has been implicated in the physiopathology of several human diseases, including cancer. In this respect, accumulating evidence indicates that NRF2 can act as a double-edged sword, being able to mediate tumor suppressive or pro-oncogenic functions, depending on the specific biological context of its activation. Thus, a better understanding of the mechanisms that control NRF2 functions and the most appropriate context of its activation is a prerequisite for the development of effective therapeutic strategies based on NRF2 modulation. In line of principle, the controlled activation of NRF2 might reduce the risk of cancer initiation and development in normal cells by scavenging reactive-oxygen species (ROS) and by preventing genomic instability through decreased DNA damage. In contrast however, already transformed cells with constitutive or prolonged activation of NRF2 signaling might represent a major clinical hurdle and exhibit an aggressive phenotype characterized by therapy resistance and unfavorable prognosis, requiring the use of NRF2 inhibitors. In this review, we will focus on the dual roles of the NRF2-KEAP1 pathway in cancer promotion and inhibition, describing the mechanisms of its activation and potential therapeutic strategies based on the use of context-specific modulation of NRF2.

Activation of the PDGFRα-Nrf2 pathway mediates impaired adipocyte differentiation in bone marrow mesenchymal stem cells lacking Nck1

BACKGROUND

The limited options to treat obesity and its complications result from an incomplete understanding of the underlying molecular mechanisms regulating white adipose tissue development, including adipocyte hypertrophy (increase in size) and hyperplasia (increase in number through adipogenesis). We recently demonstrated that lack of the adaptor protein Nck1 in mice is associated with reduced adiposity and impaired adipocyte differentiation. In agreement, Nck1 depletion in 3 T3-L1 cells also attenuates adipocyte differentiation by enhancing PDGFRα activation and signaling. This is accompanied by higher expression of PDGF-A, a specific PDGFRα ligand, that may contribute to enhanced activation of PDGFRα signaling in the absence of Nck1 in white adipose tissue. However, whether Nck1 deficiency also impairs adipogenic differentiation in bone marrow still remains to be determined.

METHODS

To address this point, Nck1-deficient derived bone marrow mesenchymal stem/stromal cells (BM-MSCs) and C3H10T1/2 mesenchymal stem cells were differentiated into adipocytes in vitro. Genes and proteins expression in these cellular models were determined using qPCR and western blotting respectively. Pharmacological approaches were used to assess a role for Nrf2 in mediating Nck1 deficiency effect on mesenchymal stem cells adipocyte differentiation.

RESULTS

Nck1 deficiency in both BM-MSCs and C3H10T1/2 results in impaired adipocyte differentiation, accompanied by increased activation of the transcription factor Nrf2, as shown by increased mRNA levels of Nrf2 target genes, including PDGF-A. Using pharmacological activator and inhibitor of Nrf2, we further provide evidence that Nrf2 is an important player in PDGFRα signaling that mediates expression of PDGF-A and impaired adipogenesis in Nck1-deficient BM-MSCs and C3H10T1/2 cells.

CONCLUSION

This study demonstrates that Nck1 deficiency in mesenchymal stem cells impairs adipogenesis through activation of the PDGFRα-Nrf2 anti-adipogenic signaling pathway. Video Abstract.

The Role of Nrf2 Activity in Cancer Development and Progression

Nrf2 is a transcription factor that stimulates the expression of genes which have antioxidant response element-like sequences in their promoter. Nrf2 is a cellular protector, and this principle applies to both normal cells and malignant cells. While healthy cells are protected from DNA damage induced by reactive oxygen species, malignant cells are defended against chemo- or radiotherapy. Through our literature search, we found that Nrf2 activates several oncogenes unrelated to the antioxidant activity, such as Matrix metallopeptidase 9 (MMP-9), B-cell lymphoma 2 (BCL-2), B-cell lymphoma-extra large (BCL-xL), Tumour Necrosis Factor α (TNF-α), and Vascular endothelial growth factor A (VEGF-A). We also did a brief analysis of The Cancer Genome Atlas (TCGA) data of lung adenocarcinoma concerning the effects of radiation therapy and found that the therapy-induced Nrf2 activation is not universal. For instance, in the case of recurrent disease and radiotherapy, we observed that, for the majority of Nrf2-targeted genes, there is no change in expression level. This proves that the universal, axiomatic rationale that Nrf2 is activated as a response to chemo- and radiation therapy is wrong, and that each scenario should be carefully evaluated with the help of Nrf2-targeted genes. Moreover, there were nine genes involved in lipid peroxidation, which showed underexpression in the case of new radiation therapy: ADH1A, ALDH3A1, ALDH3A2, ADH1B, GPX2, ADH1C, ALDH6A1, AKR1C3, and NQO1. This may relate to the fact that, while some studies reported the co-activation of Nrf2 and other oncogenic signaling pathways such as Phosphoinositide 3-kinases (PI3K), mitogen-activated protein kinase (MAPK), and Notch1, other reported the inverse correlation between Nrf2 and the tumor-promoter Transcription Factor (TF), Nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB). Lastly, Nrf2 establishes its activity through interactions at multiple levels with various microRNAs. MiR-155, miR-144, miR-28, miR-365-1, miR-93, miR-153, miR-27a, miR-142, miR-29-b1, miR-340, and miR-34a, either through direct repression of Nrf2 messenger RNA (mRNA) in a Kelch-like ECH-associated protein 1 (Keap1)-independent manner or by enhancing the Keap1 cellular level, inhibit the Nrf2 activity. Keap1–Nrf2 interaction leads to the repression of miR-181c, which is involved in the Nuclear factor kappa light chain enhancer of activated B cells (NF-κB) signaling pathway. Nrf2’s role in cancer prevention, diagnosis, prognosis, and therapy is still in its infancy, and the future strategic planning of Nrf2-based oncological approaches should also consider the complex interaction between Nrf2 and its various activators and inhibitors.

Induction of nuclear protein-1 by thyroid hormone enhances platelet-derived growth factor A mediated angiogenesis in liver cancer

Background & Aims: Hepatocellular carcinoma (HCC) is among the leading causes of cancer deaths worldwide. Many studies indicate that disruption of cellular thyroid hormone signaling promotes HCC progression. However, the mechanisms underlying the regulation of genes downstream of thyroid hormone actions in HCC have remained elusive. In the current study, we identified NUPR1 (nuclear protein-1), a stress-induced protein that overexpresses in various neoplasia, is upregulated by triiodothyronine/thyroid hormone receptor (T₃/TR) signaling and aimed to elucidate its role in angiogenesis in cancer progression.

Methods: Quantitative reverse transcription-PCR, luciferase promoter and chromatin immunoprecipitation assays were performed to identify the NUPR1 regulatory mechanism by T₃/TR. In vitro and In vivo vascular formations were performed to detect the angiogenic function of NUPR1. Human angiogenesis arrays were performed to identify the downstream angiogenic pathway. The sorafenib resistant ability of TR/NUPR1 was further examined in vitro and in vivo. Clinical relevance of TR, NUPR1 and platelet-derived growth factor A (PDGFA) were investigate in HCC samples using qRT-PCR and western blot.

Results: Our experiments disclosed positive regulation of NUPR1 expression by T₃/TR through direct binding to the -2066 to -1910 region of the NUPR1 promoter. Elevated NUPR1 and TR expression link to poor survival in clinical HCC specimens. An analysis of clinicopathological parameters showed that expression of NUPR1 is associated with vascular invasion and pathology stage. Functional studies revealed that NUPR1 induced endothelial cell angiogenesis in vitro and in vivo. Using a human angiogenesis array, we identified PDGFA as a target of NUPR1 in the downstream angiogenic pathway. NUPR1 induced transcription of PDGFA through direct binding to the corresponding promoter region, and inhibition of the PDGFA signaling pathway impaired angiogenesis in human umbilical vein endothelial cells (HUVECs). Notably, the angiogenic effects of NUPR1/PDGFA were mediated by the MEK/ERK signaling pathway. TR/NUPR1 expression increased cell viability and resistance to sorafenib treatment. Moreover NUPR1 expression was positively correlated with TRα, TRβ, and PDGFA expression.

Conclusions: We propose that the T₃/TR/NUPR1/PDGFA/MEK/ERK axis has a vital role in hepatocarcinogenesis and suggest NUPR1 as a potential therapeutic target in HCC.

Potential Applications of NRF2 Inhibitors in Cancer Therapy

The NRF2/KEAP1 pathway represents one of the most important cell defense mechanisms against exogenous or endogenous stressors. Indeed, by increasing the expression of several cytoprotective genes, the transcription factor NRF2 can shelter cells and tissues from multiple sources of damage including xenobiotic, electrophilic, metabolic, and oxidative stress. Importantly, the aberrant activation or accumulation of NRF2, a common event in many tumors, confers a selective advantage to cancer cells and is associated to malignant progression, therapy resistance, and poor prognosis. Hence, in the last years, NRF2 has emerged as a promising target in cancer treatment and many efforts have been made to identify therapeutic strategies aimed at disrupting its prooncogenic role. By summarizing the results from past and recent studies, in this review, we provide an overview concerning the NRF2/KEAP1 pathway, its biological impact in solid and hematologic malignancies, and the molecular mechanisms causing NRF2 hyperactivation in cancer cells. Finally, we also describe some of the most promising therapeutic approaches that have been successfully employed to counteract NRF2 activity in tumors, with a particular emphasis on the development of natural compounds and the adoption of drug repurposing strategies.

Repressing of NHERF1 inhibits liver cancer progression by promoting the production of ROS

NHERF1/EBP50 is a PDZ-scaffold protein initially identified as an organizer and modulator of transporters and channels at the apical side of epithelia via actin-binding ezrin-moesin-radixin proteins. Presently, hepatocellular carcinoma (HCC) is one of the most deadly cancers in the world and has no effective therapeutic strategies. In the present study, we attempted to explore the role of NHERF1 in regulating liver cancer progression. The results indicated that NHERF1 was significantly expressed in liver tumor samples compared to the corresponding adjacent normal tissues. HCC patients with low NHERF1 exhibited better survival rate. Additionally, repressing NHERF1 expression markedly down-regulated the cell proliferation. G0/G1 transition was highly induced by NHERF1 knockdown, accompanied with reduced expressions of Cyclin D1 and cyclin-dependent kinase 4 (CDK4), as well as the enhanced expression of p27, phosphatase and tensin homolog (PTEN) and p53. Moreover, NHERF1 suppression significantly induced apoptosis in liver cancer cells by promoting the activation of Caspase-3 and poly (ADP-ribose) polymerase (PARP). We also observed a remarkable increase of reactive oxygen species (ROS) production in NHERF1-knockdown cells, along with c-Jun-N-terminal kinase (JNK) phosphorylation. Importantly, suppressing ROS production abolished NHERF1 knockdown-induced JNK activation. Moreover, cell cycle-regulatory proteins meditated by NHERF1 knockdown in liver cancer cells were abrogated by the pre-treatment of ROS scavenger. Further, restraining ROS generation also diminished NHERF1 knockdown-induced apoptosis. In vivo, we also found that NHERF1 knockdown markedly reduced the tumor growth. In conclusion, the results suggested that NHERF1 played an essential role in regulating liver cancer progression, and repressing NHERF1 expression exhibited significant anticancer effects via the induction of G0/G1 phase arrest, apoptosis and ROS generation.

Prospect of Circular RNA in Hepatocellular Carcinoma: A Novel Potential Biomarker and Therapeutic Target

CircRNA, a kind of tissue specific and covalently closed circular non-coding RNA is very abundant in eukaryocyte. Generally, circRNA is generated by back-splicing of protein-coding genes' pre-mRNA. Hepatocellular carcinoma (HCC) is one of the most common malignant tumors in the world. Due to the characteristics of poor prognosis and high recurrence, the pathogenesis of HCC is highly concerned by researchers worldwide. Recent studies demonstrated that numerous circRNAs were differentially expressed in HCC tissues and normal liver tissues, which is closely related with the development and prognosis of HCC. However, the mechanism of circRNA in HCC remains unclear. In this review, we summarized the abnormal expressions of circRNAs in HCC, discussed its role, and potential mechanisms, and tried to explore the prospective values of circRNA in the diagnosis, therapy, and prognosis of HCC.

Platelet-to-lymphocyte ratio in the setting of liver transplantation for hepatocellular cancer: A systematic review and meta-analysis

AIM

To perform a systematic review and meta-analysis on platelet-to-lymphocyte ratio (PLR) as a risk factor for post-transplant hepatocellular cancer (HCC) recurrence.

METHODS

A systematic literature search was performed using PubMed. Participants of any age and sex, who underwent liver transplantation for HCC were considered following these criteria: (1) studies comparing pre-transplant low vs high PLR values; (2) studies reporting post-transplant recurrence rates; and (3) if more than one study was reported by the same institute, only the most recent was included. The primary outcome measure was set for HCC recurrence after transplantation.

RESULTS

A total of 5 articles, published between 2014 and 2017, fulfilled the selection criteria. As for the quality of the reported studies, all the investigated articles presented an overall high quality. A total of 899 cases were investigated: 718 cases (80.0%) were males. Three studies coming from European countries and one from Japan presented HCV as the main cause of cirrhosis. On the opposite, one Chinese study presented a greater incidence of HBV-related cirrhotic cases. In all the studies apart one, the PLR cut-off value of 150 was reported. At meta-analysis, high PLR value was associated with a significant increase in recurrence after transplantation (OR = 3.33; 95%CI: 1.78-6.25; P < 0.001). A moderate heterogeneity was observed among the identified studies according to the Higgins I² statistic value.

CONCLUSION

Pre-transplant high PLR values are connected with an increased risk of post-operative recurrence of hepatocellular cancer. More studies are needed for better clarify the biological mechanisms of this results.

Photo-Activatable Akt Probe: A New Tool to Study the Akt-Dependent Physiopathology of Cancer Cells

Akt is commonly overexpressed and activated in cancer cells and plays a pivotal role in cell survival, protection, and chemoresistance. Therefore, Akt is one of the target molecules in understanding characters of cancer cells and developing anticancer drugs. Here we examined whether a newly developed photo-activatable Akt (PA-Akt) probe, based on a light-inducible protein interaction module of plant cryptochrome2 (CRY2) and cryptochrome-interacting basic helix–loop–helix (CIB1), can regulate Akt-associated cell functions. By illuminating blue light to the cells stably transfected with PA-Akt probe, CRY2-Akt (a fusion protein of CRY2 and Akt) underwent a structural change and interacted with Myr-CIBN (myristoylated N-terminal portion of CIB1), anchoring it at the cell membrane. Western blot analysis revealed that S473 and T308 of the Akt of probe-Akt were sequentially phosphorylated by intermittent and continuous light illumination. Endogenous Akt and GSK-3β, one of the main downstream signals of Akt, were also phosphorylated, depending on light intensity. These facts indicate that photo-activation of probe-Akt can activate endogenous Akt and its downstream signals. The photo-activated Akt conferred protection against nutritional deprivation and H₂O₂ stresses to the cells significantly. Using the newly developed PA-Akt probe, endogenous Akt was activated easily, transiently, and repeatedly. This probe will be a unique tool in studying Akt-associated specific cellular functions in cancer cells and developing anticancer drugs.

Spermidine/spermine N1-acetyltransferase regulates cell growth and metastasis via AKT/β-catenin signaling pathways in hepatocellular and colorectal carcinoma cells

Hepatocellular carcinoma (HCC) and colorectal cancer (CRC) are among the most common cancers across the world. Therefore, identifying the potential molecular mechanisms that promote HCC and CRC progression and metastasis are urgently needed. Spermidine/spermine N¹-acetyltransferase (SSAT) is a catabolic enzyme that acetylates the high-order polyamines spermine and spermidine, thus decreasing the cellular content of polyamines. Several publications have suggested that depletion of intracellular polyamines inhibited tumor progression and metastasis in various cancer cells. However, whether and how SSAT regulates cell growth, migration and invasion in hepatocellular and colorectal carcinoma cells remains unclear. In this study, depletion of polyamines mediated by SSAT not only attenuated the tumor cell proliferation but also dramatically inhibited cell migration and invasion in hepatocellular and colorectal carcinoma cells. Subsequent investigations revealed introduction of SSAT into HepG2, SMMC7721 hepatocellular carcinoma cells and HCT116 colorectal carcinoma cells significantly suppressed p-AKT, p-GSK3β expression as well as β-catenin nuclear translocation, while inhibition of GSK3β activity or exogenous polyamines could restore SSAT-induced decreases in the protein expression of p-AKT, p-GSK3β and β-catenin. Conversely, knockdown of SSAT in Bel7402 hepatocellular carcinoma cells and HT-29 colorectal carcinoma cells which expressed high levels of SSAT endogenously significantly promoted the expression of p-AKT, p-GSK3β as well as β-catenin nuclear translocation. Taken together, our results indicated depletion of polyamines by SSAT significantly inhibited cell proliferation, migration and invasion through AKT/GSK3β/β-catenin signaling pathway in hepatocellular carcinoma and colorectal cancer cells.

Nrf2 inhibition affects cell cycle progression during early mouse embryo development

Brusatol, a quassinoid isolated from the fruit of Bruceajavanica, has recently been shown to inhibit nuclear factor erythroid 2-related factor 2 (Nrf2) via Keap1-dependent ubiquitination and proteasomal degradation or protein synthesis. Nrf2 is a transcription factor that regulates the cellular defense response. Most studies have focused on the effects of Nrf2 in tumor development. Here, the critical roles of Nrf2 in mouse early embryonic development were investigated. We found that brusatol treatment at the zygotic stage prevented the early embryo development. Most embryos stayed at the two-cell stage after 5 days of culture (P < 0.05). This effect was associated with the cell cycle arrest, as the mRNA level of CDK1 and cyclin B decreased at the two-cell stage after brusatol treatment. The embryo development potency was partially rescued by the injection of Nrf2 CRISPR activation plasmid. Thus, brusatol inhibited early embryo development by affecting Nrf2-related cell cycle transition from G₂ to M phase that is dependent on cyclin B-CDK1 complex.

Progress and prospects of circular RNAs in Hepatocellular carcinoma: Novel insights into their function

Hepatocellular carcinoma (HCC) is one of the most predominant subjects of liver malignancies, which arouses global concern in the recent years. Advanced studies have found that Circular RNAs (circRNAs) are differentially expressed in HCC, with its regulatory capacity in HCC pathogenesis and metastasis. However, the underlying mechanism remains largely unknown. In this review, we summarized the functions and mechanisms of those aberrantly expressed circRNAs in HCC tissues. We hope to enlighten more comprehensive studies on the detailed mechanisms of circRNAs and explore their potential values in clinic applications. It revealed that hsa_circ_0004018 can be used as a potential biomarker in HCC diagnosis, with its superior sensitivity to alpha-fetoprotein (AFP). Notably, the correlation of circRNA abundance in the proliferation of liver regeneration (LR) has recently been clarified and different circRNA profiles served as candidates for nonalcoholic steatohepatitis (NASH) diagnosis also be discussed. Therefore, the improved understanding of circRNAs in HCC pathogenesis and metastasis proposed a novel basis for the early diagnosis in HCC patients, which provides a useful resource to explore the pathogenesis of HCC.

Diallyl trisulfide suppresses tumor growth through the attenuation of Nrf2/Akt and activation of p38/JNK and potentiates cisplatin efficacy in gastric cancer treatment

Diallyl trisulfide (DATS), a garlic organosulfide, has shown excellent chemopreventive potential. Cisplatin (DDP) is widely used to treat solid malignant tumors, but causing serious side effects. In the current study, we attempted to elucidate the chemopreventive mechanisms of DATS in human gastric cancer BGC-823 cells in vitro, and to investigate whether DATS could enhance the anti-tumor efficacy of DDP and improve quality of life in BGC-823 xenograft mice in vivo. Treatment with DATS (25-400 μmol/L) dose-dependently inhibited the viability of BGC-823 cells in vitro with an IC₅₀ of 115.2±4.3 μmol/L after 24 h drug exposure. DATS (50-200 μmol/L) induced cell cycle arrest at G₂/M phase in BGC-823 cells, which correlated with significant accumulation of cyclin A2 and B1. DATS also induced BGC-823 cell apoptosis, which was accompanied by the modulation of Bcl-2 family members and caspase cascade activation. In BGC-823 xenograft mice, administration of DATS (20-40 mg·kg^-1·d^-1, ip) dose-dependently inhibited tumor growth and markedly reduced the number of Ki-67 positive cells in tumors. Interestingly, combined administration of DATS (30 mg·kg^-1·d^-1, ip) with DDP (5 mg/kg, every 5 d, ip) exhibited enhanced anti-tumor activity with fewer side effects. We showed that treatment of BGC-823 cells with DATS in vitro and in vivo significantly activated kinases such as p38 and JNK/MAPK and attenuated the Nrf2/Akt pathway. This study provides evidence that DATS exerts anticancer effects and enhances the antitumor efficacy of DDP, making it a novel candidate for adjuvant therapy for gastric cancer.

Oxidative stress indicated by elevated expression of Nrf2 and 8-OHdG promotes hepatocellular carcinoma progression

Reactive oxygen species (ROS) is excessively generated in tumors creating an oxidative stress in tumor microenvironment. We investigated hepatic expression of nuclear factor erythroid 2-related factor 2 (Nrf2) and 8-hydroxydeoxyguanosine (8-OHdG) in hepatocellular carcinoma (HCC) patients, and asked if ROS epigenetically upregulated Nrf2 and enhanced aggressiveness in HCC cells. Expression of Nrf2 (n = 100) and 8-OHdG (n = 53) was remarkably increased in HCC tissues compared with the noncancerous hepatic tissues. Elevated expression of 8-OHdG was associated with poor survival in HCC patients. H₂O₂, as ROS representative, provoked oxidative stress in HepG2 cells, indicated by increased protein carbonyl content and decreased total antioxidant capacity. Nrf2 expression and 8-OHdG formation were markedly increased in the H₂O₂-treated cells compared with the untreated control. Co-treatment with antioxidants, tocopheryl acetate (TA) and S-adenosylmethionine (SAM) effectively attenuated expression of Nrf2 and 8-OHdG in H₂O₂-treated cells. HepG2 cells treated with H₂O₂ had significantly higher migration and invasion capabilities than the untreated control cells, and this aggressiveness was significantly inhibited by TA and SAM. Bisulfite sequencing revealed that CpG dinucleotides in Nrf2 promoter were unmethylated in the H₂O₂-treated cells similar to the untreated control. In conclusion, robust histological evidence of increased antioxidative response and oxidative DNA damage in human HCC tissues was demonstrated. Elevated oxidative DNA lesion 8-OHdG was associated with shorter survival. Experimentally, ROS enhanced Nrf2 expression, 8-OHdG formation and tumor progression in HCC cells. These effects were inhibited by antioxidants. Therefore, oxidative stress-reducing regimens might be beneficial to diminish the ROS-induced HCC progression.

Ursolic Acid Ameliorates Early Brain Injury After Experimental Traumatic Brain Injury in Mice by Activating the Nrf2 Pathway

Previous studies have indicated oxidative stress and inflammatory injury as significant contributors to the secondary damage associated with traumatic brain injury (TBI). Ursolic acid (UA) has been demonstrated to exert anti-oxidative and anti-inflammatory effects on cerebral ischemia by activating the nuclear factor-erythroid 2-related factor 2 (Nrf2) pathway. However, the effects of UA on TBI remain unclear. The aim of this study is to evaluate the potential roles of UA in the activation of the Nrf2 pathway using an experimental TBI model and the underlying mechanism. Wild-type (WT) and Nrf2(-/-) mice were divided into eight groups: (1) sham; (2) TBI; (3) TBI + vehicle; (4) TBI + 50 mg/kg UA; (5) TBI + 100 mg/kg UA; (6) TBI + 150 mg/kg UA; (7) TBI + Nrf2(-/-) + vehicle; (8) TBI + Nrf2(-/-) + UA. All mice underwent the TBI with the exception of the sham group. The neurologic outcomes of the mice were evaluated at 24 h after TBI, as well as the expression of Nrf2, NQO1, HO1,SOD, GPx, and MDA. Treatment of UA significantly ameliorated brain edema and the neurological insufficiencies after TBI. In addition, UA treatment markedly strengthened the nuclear translocation of Nrf2 protein and increased the expression of NQO1 and HO1. Moreover, UA significantly increased the expression of AKT, an Nrf2 upstream factor, suggesting that UA play a neuroprotective role through the activation of the Nrf2-ARE signal pathway. On the contrary, UA showed no neuroprotective effect on the Nrf2(-/-) mice. These data indicated that UA increases the activity of antioxidant enzymes and attenuated brain injury via Nrf2 factor.