Nrf2 pathway regulates multidrug-resistance-associated protein 1 in small cell lung cancer

Recent Advances in the Clinical Translation of Small-Cell Lung Cancer Therapeutics

Small-cell lung cancer (SCLC) is a recalcitrant form of cancer, representing 15% of lung cancer cases globally. SCLC is classified within the range of neuroendocrine pulmonary neoplasms, exhibiting shared morphologic, ultrastructural, immunohistochemical, and molecular genomic features. It is marked by rapid proliferation, a propensity for early metastasis, and an overall poor prognosis. The current conventional therapies involve platinum-etoposide-based chemotherapy in combination with immunotherapy. Nonetheless, the rapid emergence of therapeutic resistance continues to pose substantial difficulties. The genomic profiling of SCLC uncovers significant chromosomal rearrangements along with a considerable mutation burden, typically involving the functional inactivation of the tumor suppressor genes TP53 and RB1. Identifying biomarkers and evaluating new treatments is crucial for enhancing outcomes in patients with SCLC. Targeted therapies such as topoisomerase inhibitors, DLL3 inhibitors, HDAC inhibitors, PARP inhibitors, Chk1 inhibitors, etc., have introduced new therapeutic options for future applications. In this current review, we will attempt to outline the key molecular pathways that play a role in the development and progression of SCLC, together with a comprehensive overview of the most recent advancements in the development of novel targeted treatment strategies, as well as some ongoing clinical trials against SCLC, with the goal of improving patient outcomes.

Silencing Nrf2 in cisplatin resistant non-small cell lung cancer cells augments sensitivity towards EGFR inhibitor

Recently, non-small cell lung cancer (NSCLC) has been the prime concern of cancer clinicians due to its high mortality rate worldwide. Cisplatin, a platinum derivative, has been used as a therapeutic option for treating metastatic NSCLC for several years. However, acquired, or intrinsic drug resistance to Cisplatin is the major obstacle to the successful treatment outcome of patients. Dysregulation of Nrf2 (nuclear factor erythroid 2-related factor 2) and EGFR (epidermal growth factor receptor) signaling have been associated with cellular proliferation, cancer initiation, progression and confer drug resistance to several therapeutic agents including Cisplatin in various cancers. To dissect the molecular mechanism of EGFR activation in resistant cells, we developed Cisplatin-resistant (CisR) human NSCLC cell lines (A549 and NCIH460) with increasing doses of Cisplatin treatment over a 3-month period. CisR cells demonstrated increased proliferative capacity, clonogenic survivability and drug efflux activity compared to the untreated parental (PT) cells. These resistant cells also showed higher levels of Nrf2 and EGFR expression. Here, we found that Nrf2 upregulates both basal and inducible expression of EGFR in these CisR cells at the transcriptional level. Moreover, genetic inhibition of Nrf2 with siRNA in CisR cells showed increased sensitivity towards the EGFR tyrosine kinase inhibitor (TKIs), AG1478. Our study, therefore suggests the use of Nrf2 inhibitors in combinatorial therapy with EGFR TKIs for the treatment of resistant NSCLC.

Characterization of a deazaflavin analog as a potent inhibitor of multidrug resistance-associated protein 1

Selective inhibition of overexpressed ATP binding cassette (ABC) transporters is an attractive approach to enhancing the efficacy of chemotherapeutics in multidrug resistant cancers. Previously, we reported that the cancer sensitizing effect of deazaflavin analogs, an important chemotype for developing combination treatments with topoisomerase II (TOP2) poisons, is associated with increased intracellular drug accumulation. Here we report the characterization of ZW-1226, a deazaflavin analog, as a potent inhibitor of multidrug resistance-associated protein 1 (MRP1). Specifically, ZW-1226 inhibited MRP1 with a 16-fold higher potency than the most widely used positive control MK-571 in vesicular transport assay and displayed excellent selectivity indices exceeding 100 over other major ABC transporters, including P-glycoprotein (P-gp), breast cancer resistance protein (BCRP), MRP2 and MRP3. Mechanistically, we revealed that its MRP1 inhibitory action requires the participation of GSH. In chemo-sensitization test, ZW-1226 fully reversed the MRP1-mediated drug resistance to TOP2 poisons etoposide (ETP) and doxorubicin (DOX) in H69AR cells and conferred CC50s comparable to those in the sensitive parental NCI-H69 cells. The sensitization was associated with boosted intracellular accumulation of ETP and DOX and elevated endogenous GSH. Moreover, ZW-1226 showed potential to occupy the leukotriene C4 binding site in molecular docking with bovine MRP1, presumably with the help of GSH. Lastly, ZW-1226 exhibited high tissue to plasma partitions in mice but did not alter ETP distribution to normal tissues, suggesting it could be a viable lead with desirable pharmacokinetic properties to warrant further investigation.

ABCC1 Is a ΔNp63 Target Gene Overexpressed in Squamous Cell Carcinoma

The transcription factor ΔNp63 plays a pivotal role in maintaining the integrity of stratified epithelial tissues by regulating the expression of distinct target genes involved in lineage specification, cell stemness, cell proliferation and differentiation. Here, we identified the ABC transporter subfamily member ABCC1 as a novel ΔNp63 target gene. We found that in immortalized human keratinocytes and in squamous cell carcinoma (SCC) cells, ∆Np63 induces the expression of ABCC1 by physically occupying a p63-binding site (p63 BS) located in the first intron of the ABCC1 gene locus. In cutaneous SCC and during the activation of the keratinocyte differentiation program, ∆Np63 and ABCC1 levels are positively correlated raising the possibility that ABCC1 might be involved in the regulation of the proliferative/differentiative capabilities of squamous tissue. However, we did not find any gross alteration in the structure and morphology of the epidermis in humanized hABCC1 knock-out mice. Conversely, we found that the genetic ablation of ABCC1 led to a marked reduction in inflammation-mediated proliferation of keratinocytes, suggesting that ABCC1 might be involved in the regulation of keratinocyte proliferation upon inflammatory/proliferative signals. In line with these observations, we found a significant increase in ABCC1 expression in squamous cell carcinomas (SCCs), a tumor type characterized by keratinocyte hyper-proliferation and a pro-inflammatory tumor microenvironment. Collectively, these data uncover ABCC1 as an additional ∆Np63 target gene potentially involved in those skin diseases characterized by dysregulation of proliferation/differentiation balance.

Small Cell Lung Cancer-An Update on Chemotherapy Resistance

OPINION STATEMENT

Compared to other types of lung cancer, small cell lung cancer (SCLC) exhibits aggressive characteristics that promote drug resistance. Despite platinum-etoposide chemotherapy combined with immunotherapy being the current standard treatment, the rapid development of drug resistance has led to unsatisfactory clinical outcomes. This review focuses on the mechanisms contributing to the chemotherapy resistance phenotype in SCLC, such as increased intra-tumoral heterogeneity, alterations in the tumor microenvironment, changes in cellular metabolism, and dysregulation of apoptotic pathways. A comprehensive understanding of these drug resistance mechanisms in SCLC is imperative for ushering in a new era in cancer research, which will promise revolutionary advancements in cancer diagnosis and treatment methodologies.

Amiloride reduces fructosamine-3-kinase expression to restore sunitinib sensitivity in renal cell carcinoma

The kidney is a vital organ responsible for water and sodium metabolism, while the primary function of amiloride is to promote the excretion of water and sodium. We investigated amiloride enhanced the sunitinib sensitivity in RCC. We found both sunitinib and amiloride displayed cytotoxicity and exerted the synergy effect in RCC cells in vivo and in vitro arrays. Protein expression profiles were screened via MS/TMT, revealing that FN3K was upregulated in the sunitinib group, and rescued in amiloride and the combination administration. Exogenous FN3K could promote proliferation, invasion and metastasis and decrease the sensitivity of Caki-1 cells to sunitinib, also, exogenous FN3K up-regulated VEGFR2 expression and activated AKT/mTOR signal pathway. More FN3K and VEGFR2 accumulated in R-Caki-1 cells and rescued by amiloride treatment. Co-IP and IF confirmed the interaction between FN3K and VEGFR2. In conclusion, FN3K depletion mediated VEGFR2 disruption promotes amiloride synergized the anti-RCC activity of sunitinib.

AQP3 and AQP5 Modulation in Response to Prolonged Oxidative Stress in Breast Cancer Cell Lines

Aquaporins are membrane pores regulating the transport of water, glycerol, and other small molecules across membranes. Among 13 human aquaporins, six have been shown to transport H2O2 and are therefore called peroxiporins. Peroxiporins are implicated in cancer development and progression, partly due to their involvement in H2O2 transport. Oxidative stress is linked to breast cancer development but is also a mechanism of action for conventional chemotherapy. The aim of this study is to investigate the effects of prolonged oxidative stress on Aquaporin 3 (AQP3), Aquaporin 5 (AQP5), and signaling pathways in breast cancer cell lines of different malignancies alongside a non-tumorigenic breast cell line. The prolonged oxidative stress caused responses in viability only in the cancer cell lines, while it affected cell migration in the MCF7 cell line. Changes in the localization of NRF2, a transcription factor involved in oxidative stress response, were observed only in the cancer cell lines, and no effects were recorded on its downstream target proteins. Moreover, the prolonged oxidative stress caused changes in AQP3 and AQP5 expression only in the cancer cell lines, in contrast to their non-malignant counterparts. These results suggest peroxiporins are potential therapeutic targets in cancer treatment. However, further research is needed to elucidate their role in the modulation of therapy response, highlighting the importance of research on this topic.

Proteomic study of gamma-oryzanol preventive effect on a diet-induced non-alcoholic fatty liver disease model

Nonalcoholic fatty liver disease (NAFLD) is the most common liver disease associated with obesity and diabetes prevalence. The use of natural compounds has become an attractive approach to prevent NAFLD and its progression. Gamma-oryzanol (Orz) is a natural compound whose beneficial effects on chronic metabolic diseases have been reported. Therefore, we aimed to investigate the preventive effect of Orz on the hepatic proteome in a diet induced NAFLD model. Wistar rats were randomly distributed into three experimental groups (n=6/group) according to the diet received for 30 weeks: Control group, high sugar-fat (HSF) group, and HSF+Orz group. The isolated Orz was added to the chow at the dose of 0.5% (w/w). We evaluated the nutritional profile, characterized the presence of steatosis through histological analysis, triglyceride content in liver tissue and hepatic inflammation. Next, we performed label-free quantitative proteomics of hepatic tissue. Network analysis was performed to describe involved protein pathways. NAFLD induction was characterized by the presence of hepatic steatosis. Orz prevented lipid accumulation. The compound prevented alterations of the hepatic proteome, highlighted by the modulation of lipid metabolism, inflammation, oxidative stress, xenobiotic metabolism, and the sirtuin signaling pathway. It was possible to identify key altered pathways of NAFLD pathophysiology modulated by Orz which may provide insights into NAFLD treatment targets.

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

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

Effects of chemotherapeutic drugs on the antioxidant capacity of human erythroleukemia cells with MDR phenotype

In this work, we identified that different chemotherapeutic drugs may select cells with different antioxidant capacities. For this, we evaluated the sensitivity of two multidrug-resistant (MDR) erythroleukemia cell lines: Lucena (resistant to vincristine, VCR) and FEPS (resistant to daunorubicin, DNR) derived from the same sensitive cell K562 (non-MDR) to hydrogen peroxide. In addition, we evaluated how the cell lines respond to the oxidizing agent in the absence of VCR/DNR. In absence of VCR, Lucena drastically decreases cell viability when exposed to hydrogen peroxide, while FEPS is not affected even without DNR. To analyze whether selection by different chemotherapeutic agents may generate altered energetic demands, we analyzed the production of reactive oxygen species (ROS) and the relative expression of the glucose transporter 1 gene (glut1). We observed that the selection through DNR apparently generates a higher energy demand than VCR. High levels of transcription factors genes expression (nrf2, hif-1α, and oct4) were kept even when the DNR is withdrawn from the FEPS culture for one month. Together, these results indicate that DNR selects cells with greater ability to express the major transcription factors related to the antioxidant defense system and the main extrusion pump (ABCB1) related to the MDR phenotype. Taking into account that the antioxidant capacity of tumor cells is closely related to resistance to multiple drugs, it is evident that endogenous antioxidant molecules may be targets for the development of new anticancer drugs.

High Expression of NRF2 and Low Expression of KEAP1 Predict Worse Survival in Patients With Operable Triple-Negative Breast Cancer

PURPOSE

Triple-negative breast cancer (TNBC) is an aggressive type of breast cancer. Currently, no effective treatment options for this condition exist. Nuclear factor erythroid 2-related factor 2 (NRF2), encoded by nuclear factor erythroid-derived 2-like 2 (NFE2L2) gene and its endogenous inhibitor, Kelch-like ECH-associated protein 1 (KEAP1), both participate in cellular defense mechanisms against oxidative stress and contribute to chemoresistance and tumor progression in numerous types of cancers. This study aimed to evaluate the expression patterns of NRF2 and KEAP1 and their prognostic value in operable TNBC.

METHODS

Tissue microarrays were prepared using tumor tissues collected from 203 patients with TNBC who underwent surgery. Immunohistochemical staining analyses of NRF2 and KEAP1 were performed. The expression of each immunomarker was categorized into two groups (low or high) based on the median H-score. We analyzed the association between the expression of each immunomarker and clinicopathological information to predict survival. A total of 225 TNBC samples from the Molecular Taxonomy of Breast Cancer International Consortium (METABRIC) dataset were used to validate our results.

RESULTS

NRF2 immunoreactivity was detected in the nucleus and was associated with histologic grade and Ki-67 index, whereas KEAP1 immunoreactivity was detected in the cytoplasm and was associated with the Ki-67 index. Survival analyses showed that NRF2 and KEAP1 expressions were independent prognostic factors for overall survival (OS) (hazard ratio [HR], 2.45 and 0.30; p = 0.015 and 0.016, respectively) and disease-free survival (HR, 2.27 and 0.42; p = 0.019 and 0.022, respectively). NFE2L2 mRNA expression was an independent prognostic factor for OS (HR, 0.59; p = 0.009) in the METABRIC dataset.

CONCLUSION

High NRF2 and low KEAP1 expressions independently predicted poor survival in patients with operable TNBC. Further investigations are warranted to examine the possible therapeutic benefits of targeting the KEAP1-NRF2 pathway for TNBC treatment.

A Novel NCI-H69AR Drug-Resistant Small-Cell Lung Cancer Mini-Tumor Model for Anti-Cancer Treatment Screening

Small-cell lung cancer is a fast-growing carcinoma with a poor prognosis and a high level of relapse due to multi-drug resistance (MDR). Genetic mutations that lead to the overexpression of efflux transporter proteins can contribute to MDR. In vitro cancer models play a tremendous role in chemotherapy development and the screening of possible anti-cancer molecules. Low-cost and simple in vitro models are normally used. Traditional two-dimensional (2D) models have numerous shortcomings when considering the physiological resemblance of an in vivo setting. Three-dimensional (3D) models aim to bridge the gap between conventional 2D models and the in vivo setting. Some of the advantages of functional 3D spheroids include better representation of the in vivo physiology and tumor characteristics when compared to traditional 2D cultures. During this study, an NCI-H69AR drug-resistant mini-tumor model (MRP1 hyperexpressive) was developed by making use of a rotating clinostat bioreactor system (ClinoStar®; CelVivo ApS, Odense, Denmark). Spheroid growth and viability were assessed over a 25-day period to determine the ideal experimental period with mature and metabolically stable constructs. The applicability of this model for anti-cancer research was evaluated through treatment with irinotecan, paclitaxel and cisplatin for 96 h, followed by a 96 h recovery period. Parameters measured included planar surface area measurements, estimated glucose consumption, soluble protein content, intracellular adenosine triphosphate levels, extracellular adenylate kinase levels, histology and efflux transporter gene expression. The established functional spheroid model proved viable and stable during the treatment period, with retained relative hyperexpression of the MRP1 efflux transporter gene but increased expression of the P-gp transporter gene compared to the cells cultured in 2D. As expected, treatment with the abovementioned anti-cancer drugs at clinical doses (100 mg/m2 irinotecan, 80 mg/m2 paclitaxel and 75 mg/m2 cisplatin) had minimal impact on the drug-resistant mini-tumors, and the functional spheroid models were able to recover following the removal of treatment.

Extracellular Vesicles and Cancer Multidrug Resistance: Undesirable Intercellular Messengers?

Cancer multidrug resistance (MDR) is one of the main mechanisms contributing to therapy failure and mortality. Overexpression of drug transporters of the ABC family (ATP-binding cassette) is a major cause of MDR. Extracellular vesicles (EVs) are nanoparticles released by most cells of the organism involved in cell-cell communication. Their cargo mainly comprises, proteins, nucleic acids, and lipids, which are transferred from a donor cell to a target cell and lead to phenotypical changes. In this article, we review the scientific evidence addressing the regulation of ABC transporters by EV-mediated cell-cell communication. MDR transfer from drug-resistant to drug-sensitive cells has been identified in several tumor entities. This was attributed, in some cases, to the direct shuttle of transporter molecules or its coding mRNA between cells. Also, EV-mediated transport of regulatory proteins (e.g., transcription factors) and noncoding RNAs have been indicated to induce MDR. Conversely, the transfer of a drug-sensitive phenotype via EVs has also been reported. Additionally, interactions between non-tumor cells and the tumor cells with an impact on MDR are presented. Finally, we highlight uninvestigated aspects and possible approaches to exploiting this knowledge toward the identification of druggable processes and molecules and, ultimately, the development of novel therapeutic strategies.

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

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

ABC Transporter C1 Prevents Dimethyl Fumarate from Targeting Alzheimer's Disease

Alzheimer's disease (AD), the leading cause of dementia, is a growing health issue with very limited treatment options. To meet the need for novel therapeutics, existing drugs with additional preferred pharmacological profiles could be recruited. This strategy is known as 'drug repurposing'. Here, we describe dimethyl fumarate (DMF), a drug approved to treat multiple sclerosis (MS), to be tested as a candidate for other brain diseases. We used an APP-transgenic model (APPtg) of senile β-amyloidosis mice to further investigate the potential of DMF as a novel AD therapeutic. We treated male and female APPtg mice through drinking water at late stages of β-amyloid (Aβ) deposition. We found that DMF treatment did not result in modulating effects on Aβ deposition at this stage. Interestingly, we found that glutathione-modified DMF interacts with the ATP-binding cassette transporter ABCC1, an important gatekeeper at the blood-brain and blood-plexus barriers and a key player for Aβ export from the brain. Our findings suggest that ABCC1 prevents the effects of DMF, which makes DMF unsuitable as a novel therapeutic drug against AD. The discovered effects of ABCC1 also have implications for DMF treatment of multiple sclerosis.

Modulation of NRF2/KEAP1 Signaling in Preeclampsia

Placentation is a key and tightly regulated process that ensures the normal development of the placenta and fetal growth. Preeclampsia (PE) is a hypertensive pregnancy-related disorder involving about 5-8% of all pregnancies and clinically characterized by de novo maternal hypertension and proteinuria. In addition, PE pregnancies are also characterized by increased oxidative stress and inflammation. The NRF2/KEAP1 signaling pathway plays an important role in protecting cells against oxidative damage due to increased reactive oxygen species (ROS) levels. ROS activate NRF2, allowing its binding to the antioxidant response element (ARE) region present in the promoter of several antioxidant genes such as heme oxygenase, catalase, glutathione peroxidase and superoxide dismutase that neutralize ROS, protecting cells against oxidative stress damages. In this review, we analyze the current literature regarding the role of the NRF2/KEAP1 pathway in preeclamptic pregnancies, discussing the main cellular modulators of this pathway. Moreover, we also discuss the main natural and synthetic compounds that can regulate this pathway in in vivo and in vitro models.

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

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

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.

Role of ferroptosis on tumor progression and immunotherapy

Ferroptosis is triggered by intracellular iron leading to accumulation of lipid peroxidation consequent promotion of cell death. Cancer cell exhibits ability to evade ferroptosis by activation of antioxidant signaling pathways such as SLC7A11/GPX4 axis. In addition to transcriptional regulation on ferroptosis by NRF2, SREBP1, YAP, and p53, ferroptosis is modulated by ubiquitination or autophagic degradation. Moreover, zinc or Ca²⁺ could modulate ferroptosis by inducing lipid peroxidation and ferroptosis. Induction of ferroptosis enhances immune cell activity such as T cells or macrophages, which is associated with the release of DAMPs (damage-associated molecular patterns) and IFNγ. Therefore, combined immune checkpoint inhibitors with ferroptosis inducers effectively enhance antitumor immunotherapy, whereas induction of ferroptosis could impair T cell activity or survival, suggesting that rational combined therapy for cancer is essential. In this review, we discussed the regulatory role of ferroptosis on tumor progression and immunotherapy.

Targeted Anti-Mitochondrial Therapy: The Future of Oncology

Like living organisms, cancer cells require energy to survive and interact with their environment. Mitochondria are the main organelles for energy production and cellular metabolism. Recently, investigators demonstrated that cancer cells can hijack mitochondria from immune cells. This behavior sheds light on a pivotal piece in the cancer puzzle, the dependence on the normal cells. This article illustrates the benefits of new functional mitochondria for cancer cells that urge them to hijack mitochondria. It describes how functional mitochondria help cancer cells’ survival in the harsh tumor microenvironment, immune evasion, progression, and treatment resistance. Recent evidence has put forward the pivotal role of mitochondria in the metabolism of cancer stem cells (CSCs), the tumor components responsible for cancer recurrence and metastasis. This theory highlights the mitochondria in cancer biology and explains how targeting mitochondria may improve oncological outcomes.

Identification and validation of a prognostic model for melanoma patients with 9 ferroptosis-related gene signature

Background

Melanoma is a highly heterogeneous and aggressive cutaneous malignancy. Ferroptosis, a new pathway of cell death depending on the intracellar iron, has been shown to be significantly associated with apoptosis of a number of tumors, including melanoma. Nevertheless, the relationship between ferroptosis-related genes (FRGs) and the melanoma patients’ prognosis needs to be explored.

Methods

Download expression profiles of FRGs and clinical data from The Cancer Genome Atlas (TCGA) database. 70% data were randomly selected from the TCGA database and utilized the univariate Cox analysis and the least absolute shrinkage and selection operator (LASSO) regression model to create a prognostic model, and the remaining 30% was used to validate the predictive power of the model. In addition, GSE65904 and GSE22153 date sets as the verification cohort to testify the predictive ability of the signature.

Results

We identified nine FRGs relating with melanoma patients’ overall survival (OS) and established a prognostic model based on their expression. During the research, patients were divided into group of high-risk and low-risk according to the results of LASSO regression analysis. Survival time was significantly longer in the low-risk group than that of in the high-risk group (P < 0.001). Enrichment analysis of different risk groups demonstrated that the reasons for the difference were related to immune-related pathways, and the degree of immune cell infiltration in the low-risk group was significantly higher than that in the high-risk group.

Conclusions

The FRG prognostic model we established can predict the prognosis of melanoma patients and may further guide subsequent treatment.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12864-022-08475-y.

Metformin alleviates chronic obstructive pulmonary disease and cigarette smoke extract-induced glucocorticoid resistance by activating the nuclear factor E2-related factor 2/heme oxygenase-1 signaling pathway

Chronic obstructive pulmonary disease (COPD) is an important healthcare problem worldwide. Often, glucocorticoid (GC) resistance develops during COPD treatment. As a classic hypoglycemic drug, metformin (MET) can be used as a treatment strategy for COPD due to its anti-inflammatory and antioxidant effects, but its specific mechanism of action is not known. We aimed to clarify the role of MET on COPD and cigarette smoke extract (CSE)-induced GC resistance. Through establishment of a COPD model in rats, we found that MET could improve lung function, reduce pathological injury, as well as reduce the level of inflammation and oxidative stress in COPD, and upregulate expression of nuclear factor E2-related factor 2 (Nrf2), heme oxygenase-1 (HO-1), multidrug resistance protein 1 (MRP1), and histone deacetylase 2 (HDAC2). By establishing a model of GC resistance in human bronchial epithelial cells stimulated by CSE, we found that MET reduced secretion of interleukin-8, and could upregulate expression of Nrf2, HO-1, MRP1, and HDAC2. MET could also increase the inhibition of MRP1 efflux by MK571 significantly, and increase expression of HDAC2 mRNA and protein. In conclusion, MET may upregulate MRP1 expression by activating the Nrf2/HO-1 signaling pathway, and then regulate expression of HDAC2 protein to reduce GC resistance.

Targeting multidrug resistance-associated protein 1 (MRP1)-expressing cancers: Beyond pharmacological inhibition

Resistance to chemotherapy remains one of the most significant obstacles to successful cancer treatment. While inhibiting drug efflux mediated by ATP-binding cassette (ABC) transporters is a seemingly attractive and logical approach to combat multidrug resistance (MDR), small molecule inhibition of ABC transporters has so far failed to confer clinical benefit, despite considerable efforts by medicinal chemists, biologists, and clinicians. The long-sought treatment to eradicate cancers displaying ABC transporter overexpression may therefore lie within alternative targeting strategies. When aberrantly expressed, the ABC transporter multidrug resistance-associated protein 1 (MRP1, ABCC1) confers MDR, but can also shift cellular redox balance, leaving the cell vulnerable to select agents. Here, we explore the physiological roles of MRP1, the rational for targeting this transporter in cancer, the development of small molecule MRP1 inhibitors, and the most recent developments in alternative therapeutic approaches for targeting cancers with MRP1 overexpression. We discuss approaches that extend beyond simple MRP1 inhibition by exploiting the collateral sensitivity to glutathione depletion and ferroptosis, the rationale for targeting the shared transcriptional regulators of both MRP1 and glutathione biosynthesis, advances in gene silencing, and new molecules that modulate transporter activity to the detriment of the cancer cell. These strategies illustrate promising new approaches to address multidrug resistant disease that extend beyond the simple reversal of MDR and offer exciting routes for further research.

Treatment Failure in Acute Myeloid Leukemia: Focus on the Role of Extracellular Vesicles

Acute myeloblastic leukemia (AML) is one of the most common types of blood malignancies that results in an AML-associated high mortality rate each year. Several causes have been reported as prognostic factors for AML in children and adults, the most important of which are cytogenetic abnormalities and environmental risk factors. Following the discovery of numerous drugs for AML treatment, leukemic cells sought a way to escape from the cytotoxic effects of chemotherapy drugs, leading to treatment failure. Nowadays, comprehensive studies have looked at the role of extracellular vesicles (EVs) secreted by AML blasts and how the microenvironment of the tumor changes in favor of cancer progression and survival to discover the mechanisms of treatment failure to choose the well-advised treatment. Reports show that malignant cells secrete EVs that transmit messages to adjacent cells and the tumor's microenvironment. By secreting EVs, containing immune-inhibiting cytokines, AML cells inactivate the immune system against malignant cells, thus ensuring their survival. Also, increased secretion of EVs in various malignancies indicates an unfavorable prognostic factor and the possibility of drug resistance. In this study, we briefly reviewed the challenges of treating AML with a glance at the EVs' role in this process. It is hoped that with a deeper understanding of EVs, new therapies will be developed to eliminate the relapse of leukemic cells.

Tumour Microenvironment Stress Promotes the Development of Drug Resistance

Multi-drug resistance (MDR) is a leading cause of cancer-related death, and it continues to be a major barrier to cancer treatment. The tumour microenvironment (TME) has proven to play an essential role in not only cancer progression and metastasis, but also the development of resistance to chemotherapy. Despite the significant advances in the efficacy of anti-cancer therapies, the development of drug resistance remains a major impediment to therapeutic success. This review highlights the interplay between various factors within the TME that collectively initiate or propagate MDR. The key TME-mediated mechanisms of MDR regulation that will be discussed herein include (1) altered metabolic processing and the reactive oxygen species (ROS)-hypoxia inducible factor (HIF) axis; (2) changes in stromal cells; (3) increased cancer cell survival via autophagy and failure of apoptosis; (4) altered drug delivery, uptake, or efflux and (5) the induction of a cancer stem cell (CSC) phenotype. The review also discusses thought-provoking ideas that may assist in overcoming the TME-induced MDR. We conclude that stressors from the TME and exposure to chemotherapeutic agents are strongly linked to the development of MDR in cancer cells. Therefore, there remains a vast area for potential research to further elicit the interplay between factors existing both within and outside the TME. Elucidating the mechanisms within this network is essential for developing new therapeutic strategies that are less prone to failure due to the development of resistance in cancer cells.

Low expression of IL6R predicts poor prognosis for lung adenocarcinoma

Background

Interleukin 6 (IL6) is both a pleiotropic cytokine and an immune-related gene. Interleukin 6 receptor (IL6R) is the receptor for IL6. It may be closely connected to the development of lung cancer. This research aims to explore the prognostic value of IL6R and prevent overtreatment of patients with lung adenocarcinoma (LUAD).

Methods

In this study, the expression of IL6R in tumor tissues and surrounding tissues was first analyzed by immunohistochemistry in the Affiliated Hospital of Nantong University (NTU) cohort. Secondly, we downloaded information from The Cancer Genome Atlas (TCGA) for the TCGA cohort and used this information to explore the messenger RNA (mRNA) level of IL6R. We then used Kaplan-Meier survival analyses, univariate and multivariate Cox analyses, nomogram models, and decision curve analyses to assess the prognostic value of IL6R. In addition, we also analyzed immune cell infiltration and the signaling pathways related to IL6R through Gene Ontology (GO), Kyoto Encyclopedia of Genes and Genomes (KEGG), and Gene Set Enrichment Analysis (GSEA).

Results

Through the data analysis of the NTU cohort and the TCGA cohort, it was found that the expression of IL6R in normal tissues around the tumor was higher than that in tumor tissue, and was positively correlated with the overall survival (OS) of LUAD patients. Additionally, low expression of IL6R was found to be an independent predictor of poor prognosis among the patients in these two research cohorts. Next, using GO, KEGG, and GSEA analyses, we found that partially infiltrated tumor immune cells might be related to earlier staging and better prognosis of patients with LUAD. Finally, the study of the 3-5-year survival rate of LUAD patients through the nomogram showed that the expression of IL6R could improve the accuracy of prediction to prevent the overtreatment of some LUAD patients.

Conclusions

In summary, our study indicated that the low expression of IL6R was associated with poor prognosis among LUAD patients and that low expression of IL6R is a potential independent risk factor that could provide a basis for strengthening postoperative classification management of such patients.

Loss of IL-34 Expression Indicates Poor Prognosis in Patients With Lung Adenocarcinoma

Interleukin 34 (IL-34), an additional ligand of the colony-stimulating factor-1 receptor (CSF-1R), promotes the secretion of pro-inflammatory cytokines and stimulates NF-κB and JNK-related signaling pathways. However, the potential mechanism and prognostic value of IL-34 in lung adenocarcinoma (LUAD) remain obscure. In this study, IL-34 was found to be downregulated in LUAD tissues compared with para-carcinoma tissues, and loss of IL-34 expression was correlated with shorter overall survival (OS), which was validated by bioinformatics\ analysis in TCGA (The Cancer Genome Atlas) cohort and immunohistochemical analysis in the NTU (Nantong University) cohort, respectively. Subsequently, loss of IL-34 promotes negative regulation of the immune system and inhibits the infiltration of immune cells. Moreover, IL-34 deficiency was shown to be an independent adverse prognostic factor for patients with LUAD, and subgroup analysis indicated that IL-34 might contribute to the stratified management of patients with LUAD. IL-34-based nomogram model significantly improved the accuracy of prognostic predictions for OS of patients with LUAD, both in the TCGA cohort and the NTU cohort. Taken together, our data suggested that loss of IL-34 expression is associated with poor prognosis and negative regulation of the immune system of patients with LUAD, contributing to the stratified management of patients with LUAD.

The Potential Role of Sildenafil in Cancer Management through EPR Augmentation

Enhanced permeation retention (EPR) was a significant milestone discovery by Maeda et al. paving the path for the emerging field of nanomedicine to become a powerful tool in the fight against cancer. Sildenafil is a potent inhibitor of phosphodiesterase 5 (PDE-5) used for the treatment of erectile dysfunction (ED) through the relaxation of smooth muscles and the modulation of vascular endothelial permeability. Overexpression of PDE-5 has been reported in lung, colon, metastatic breast cancers, and bladder squamous carcinoma. Moreover, sildenafil has been reported to increase the sensitivity of tumor cells of different origins to the cytotoxic effect of chemotherapeutic agents with augmented apoptosis mediated through inducing the downregulation of Bcl-xL and FAP-1 expression, enhancing reactive oxygen species (ROS) generation, phosphorylating BAD and Bcl-2, upregulating caspase-3,8,9 activities, and blocking cells at G0/G1 cell cycle phase. Sildenafil has also demonstrated inhibitory effects on the efflux activity of ATP-binding cassette (ABC) transporters such as ABCC4, ABCC5, ABCB1, and ABCG2, ultimately reversing multidrug resistance. Accordingly, there has been a growing interest in using sildenafil as monotherapy or chemoadjuvant in EPR augmentation and management of different types of cancer. In this review, we critically examine the basic molecular mechanism of sildenafil related to cancer biology and discuss the overall potential of sildenafil in enhancing EPR-based anticancer drug delivery, pointing to the outcomes of the most important related preclinical and clinical studies.

Targeting NRF2 to treat cancer

NRF2 is a basic leucine zipper (bZip) transcription factor that is the master regulator of redox homeostasis. Under basal conditions, the cellular level of NRF2 is low due to a posttranslational regulation by the ubiquitin proteasome system (UPS). But, when an organism is challenged with oxidative or xenobiotic stress, the NRF2 pathway is activated by inhibition of the E3 ubiquitin ligase complex that normally marks NRF2 for destruction. For several decades, researchers have searched for molecules that can intentionally activate NRF2, as this was shown to be a means to prevent certain diseases, at least in animal models. In the present era, there are many compounds known to activate the NRF2 pathway including natural products and synthetic compounds, covalent and non-covalent compounds, and others. However, it was also revealed that like many protective pathways, the NRF2 pathway has a dark side. Just as NRF2 can protect normal cells from damage, it can protect malignant cells from damage. As cells transform, they are exposed to many stressors and aberrant upregulation of NRF2 can facilitate transformation and it can help cancer cells to grow, to spread, and to resist treatment. For this reason, researchers are also interested in the discovery and development of NRF2 inhibitors. In the present review, we will begin with a general discussion of NRF2 structure and function, we will discuss the latest in NRF2 non-covalent activators, and we will discuss the current state of NRF2 inhibitors.

Friend or Foe: Xenobiotic Activation of Nrf2 in Disease Control and Cardioprotection

Nuclear factor erythroid 2-related factor 2 (Nrf2) is a transcription factor that governs a highly conserved pathway central to the protection of cells against various oxidative stresses. However, the biological impact of xenobiotic intervention of Nrf2 in physiological and pathophysiological conditions remains debatable. Activation of Nrf2 in cancer cells has been shown to elevate drug resistance and increase cell survival and proliferation, while inhibition of Nrf2 sensitizes cancer cells to drug treatment. On the other hand, activation of Nrf2 in normal healthy cells has been explored as a rather successful strategy for cancer chemoprevention. Selective activation of Nrf2 in off-target cells has recently been investigated as an approach for protecting off-target tissues from untoward drug toxicity. Specifically, induction of antioxidant response element genes via Nrf2 activation in cardiac cells is being explored as a means to limit the well-documented cardiotoxicity accompanied by cancer treatment with commonly prescribed anthracycline drugs. In addition to cancers, Nrf2 has been implicated in many other diseases including Alzheimer's and Parkinson's Diseases, diabetes, and cardiovascular disease. In this review, we discuss the roles of Nrf2 and its downstream target genes in the treatment of various diseases, and its recently explored potential for increasing the benefit: risk ratio of commonly utilized cancer treatments.

The Taming of Nuclear Factor Erythroid-2-Related Factor-2 (Nrf2) Deglycation by Fructosamine-3-Kinase (FN3K)-Inhibitors-A Novel Strategy to Combat Cancers

Simple Summary

Aim of this review is to provide an overview on (a) Fructosamine-3-Kinase (FN3K) and its role in regulating Nuclear Factor Erythorid-2-Related Factor-2 (Nrf2); (b) the role of glycation and deglycation mechanisms in modulating the functional properties of proteins, in particular, the Nrf2; (c) the dual role of Nrf2 in the prevention and treatment of cancers. Since controlling the glycation of Nrf2 is one of the key mechanisms determining the fate of a cell; whether to get transformed into a cancerous one or to stay as a normal one, it is important to regulate Nrf2 and deglycating FN3K using pharmacological agents. Inhibitors of FN3K are being explored currently to modulate Nrf2 activity thereby control the cancers.

Abstract

Glycated stress is mediated by the advanced glycation end products (AGE) and the binding of AGEs to the receptors for advanced glycation end products (RAGEs) in cancer cells. RAGEs are involved in mediating tumorigenesis of multiple cancers through the modulation of several downstream signaling cascades. Glycated stress modulates various signaling pathways that include p38 mitogen-activated protein kinase (p38 MAPK), nuclear factor kappa–B (NF-κB), tumor necrosis factor (TNF)-α, etc., which further foster the uncontrolled proliferation, growth, metastasis, angiogenesis, drug resistance, and evasion of apoptosis in several cancers. In this review, a balanced overview on the role of glycation and deglycation in modulating several signaling cascades that are involved in the progression of cancers was discussed. Further, we have highlighted the functional role of deglycating enzyme fructosamine-3-kinase (FN3K) on Nrf2-driven cancers. The activity of FN3K is attributed to its ability to deglycate Nrf2, a master regulator of oxidative stress in cells. FN3K is a unique protein that mediates deglycation by phosphorylating basic amino acids lysine and arginine in various proteins such as Nrf2. Deglycated Nrf2 is stable and binds to small musculoaponeurotic fibrosarcoma (sMAF) proteins, thereby activating cellular antioxidant mechanisms to protect cells from oxidative stress. This cellular protection offered by Nrf2 activation, in one way, prevents the transformation of a normal cell into a cancer cell; however, in the other way, it helps a cancer cell not only to survive under hypoxic conditions but also, to stay protected from various chemo- and radio-therapeutic treatments. Therefore, the activation of Nrf2 is similar to a double-edged sword and, if not controlled properly, can lead to the development of many solid tumors. Hence, there is a need to develop novel small molecule modulators/phytochemicals that can regulate FN3K activity, thereby maintaining Nrf2 in a controlled activation state.

Low oxygen tension differentially regulates the expression of placental solute carriers and ABC transporters

Low oxygen concentration, or hypoxia, is an important physiological regulator of placental function including chemical disposition. Here, we compared the ability of low oxygen tension to alter the expression of solute carriers (SLC) and ABC transporters in two human placental models, namely BeWo cells and term placental explants. We found that exposure to low oxygen concentration differentially regulates transporter expression in BeWo cells, including downregulation of ENT1, OATP4A1, OCTN2, BCRP, and MRP2/3/5, and upregulation of CNT1, OAT4, OATP2B1, SERT, SOAT, and MRP1. Similar upregulation of MRP1 and downregulation of MRP5 and BCRP were observed in explants, whereas uptake transporters were decreased or unchanged. Furthermore, a screening of transcriptional regulators of transporters revealed that hypoxia leads to a decrease in the mRNA levels of aryl hydrocarbon receptor, nuclear factor erythroid 2-related factor 2, and retinoid x receptor alpha in both human placental models. These data suggest that transporter expression is differentially regulated by oxygen concentration across experimental human placental models.

Tobacco Smoke and Inhaled Drugs Alter Expression and Activity of Multidrug Resistance-Associated Protein-1 (MRP1) in Human Distal Lung Epithelial Cells in vitro

Multidrug resistance-associated protein-1 (MRP1/ABCC1) is highly expressed in human lung tissues. Recent studies suggest that it significantly affects the pulmonary disposition of its substrates, both after pulmonary and systemic administration. To better understand the molecular mechanisms involved, we studied the expression, subcellular localization and activity of MRP1 in freshly isolated human alveolar epithelial type 2 (AT2) and type 1-like (AT1-like) cells in primary culture, and in the NCI-H441 cell line. Moreover, the effect of cigarette smoke extract (CSE) and a series of inhaled drugs on MRP1 abundance and activity was investigated in vitro. MRP1 expression levels were measured by q-PCR and immunoblot in AT2 and AT1-like cells from different donors and in several passages of the NCI-H441 cell line. The subcellular localization of the transporter was studied by confocal laser scanning microscopy and cell surface protein biotinylation. MRP1 activity was assessed by bidirectional transport and efflux experiments using the MRP1 substrate, 5(6)-carboxyfluorescein [CF; formed intracellularly from 5(6)-carboxyfluorescein-diacetate (CFDA)] in AT1-like and NCI-H441 cell monolayers. Furthermore, the effect of CSE as well as several bronchodilators and inhaled corticosteroids on MRP1 abundance and CF efflux was investigated. MRP1 protein abundance increased upon differentiation from AT2 to AT1-like phenotype, however, ABCC1 gene levels remained unchanged. MRP1 abundance in NCI-H441 cells were comparable to those found in AT1-like cells. The transporter was detected primarily in basolateral membranes of both cell types which was consistent with net basolateral efflux of CF. Likewise, bidirectional transport studies showed net apical-to-basolateral transport of CF which was sensitive to the MRP1 inhibitor MK-571. Budesonide, beclomethasone dipropionate, salbutamol sulfate, and CSE decreased CF efflux in a concentration-dependent manner. Interestingly, CSE increased MRP1 abundance, whereas budesonide, beclomethasone dipropionate, salbutamol sulfate did not have such effect. CSE and inhaled drugs can reduce MRP1 activity in vitro, which implies the transporter being a potential drug target in the treatment of chronic obstructive pulmonary disease (COPD). Moreover, MRP1 expression level, localization and activity were comparable in human AT1-like and NCI-H441 cells. Therefore, the cell line can be a useful alternative in vitro model to study MRP1 in distal lung epithelium.

Reversal of doxorubicin resistance in lung cancer cells by neferine is explained by nuclear factor erythroid-derived 2-like 2 mediated lung resistance protein down regulation

Aim: Development of multi drug resistance and dose limiting cardiotoxicity are hindering the use of Doxorubicin (Dox) in clinical settings. Augmented dox efflux induced by lung resistance protein (LRP) over expression has been related to multi drug resistance phenotype in various cancers. An alkaloid from lotus, Neferine (Nef) shows both anticancer and cardioprotective effects. Here, we have investigated the interconnection between nuclear factor erythroid-derived 2-like 2 (NRF2) and LRP in Dox resistance and how Nef can overcome Dox resistance in lung cancer cells by altering this signaling. Methods: Anti-proliferative and apoptotic-inducing effects of Nef and Dox combination in Parental and Dox resistant lung cancer cells were determined in monolayers and 3D spheroids. Intracellular Dox was analyzed using flow cytometry, siRNA knockdown and western blot analysis were used to elucidate NRF2-LRP crosstalk mechanism. Results: We observed that the Dox resistant lung cancer cells expressed higher levels of LRP, reduced glutathione (GSH) and NRF2. Combination of Dox and Nef induced apoptosis, leads to reactive oxygen species (ROS) generation, GSH depletion and reduction in LRP levels contributing to higher intracellular and intranuclear Dox accumulation. The use of N-acetylcysteine and knockdown studies confirmed an important role of ROS and NRF2 in LRP down regulation. Presence of NRF2 binding sites in LRP is support of direct interaction between LRP and NRF2. Conclusion: Nef sensitizes lung cancer cells to Dox by increasing intracellular and/or intra nuclear Dox accumulation via LRP down regulation. This is mediated by redox regulating NRF2. This decoded crosstalk mechanism reinforces the role of NRF2 and LRP in Dox resistance and as an important anticancer target.

A Genome-wide Haploid Genetic Screen Identifies Regulators of Glutathione Abundance and Ferroptosis Sensitivity

The tripeptide glutathione suppresses the iron-dependent, non-apoptotic cell death process of ferroptosis. How glutathione abundance is regulated in the cell and how this regulation alters ferroptosis sensitivity is poorly understood. Using genome-wide human haploid genetic screening technology coupled to fluorescence-activated cell sorting (FACS), we directly identify genes that regulate intracellular glutathione abundance and characterize their role in ferroptosis regulation. Disruption of the ATP binding cassette (ABC)-family transporter multidrug resistance protein 1 (MRP1) prevents glutathione efflux from the cell and strongly inhibits ferroptosis. High levels of MRP1 expression decrease sensitivity to certain pro-apoptotic chemotherapeutic drugs, while collaterally sensitizing to all tested pro-ferroptotic agents. By contrast, disruption of KEAP1 and NAA38, leading to the stabilization of the transcription factor NRF2, increases glutathione levels but only weakly protects from ferroptosis. This is due in part to concomitant NRF2-mediated upregulation of MRP1. These results pinpoint glutathione efflux as an unanticipated regulator of ferroptosis sensitivity.

Glutathione suppresses the non-apoptotic cell death process of ferroptosis. Using genome-wide human haploid cell mutagenesis and FACS-based detection, Cao et al. identify negative regulators of intracellular glutathione abundance that affect glutathione efflux and NRF2 protein levels, altering ferroptosis sensitivity.

Identification of Novel Rare ABCC1 Transporter Mutations in Tumor Biopsies of Cancer Patients

The efficiency of chemotherapy drugs can be affected by ATP-binding cassette (ABC) transporter expression or by their mutation status. Multidrug resistance is linked with ABC transporter overexpression. In the present study, we performed rare mutation analyses for 12 ABC transporters related to drug resistance (ABCA2, -A3, -B1, -B2, -B5, -C1, -C2, -C3, -C4, -C5, -C6, -G2) in a dataset of 18 cancer patients. We focused on rare mutations resembling tumor heterogeneity of ABC transporters in small tumor subpopulations. Novel rare mutations were found in ABCC1, but not in the other ABC transporters investigated. Diverse ABCC1 mutations were found, including nonsense mutations causing premature stop codons, and compared with the wild-type protein in terms of their protein structure. Nonsense mutations lead to truncated protein structures. Molecular docking and heat map analyses of ABCC1/MRP1 pointed out that Lys498* appeared in a separate cluster branch due to the large deletion, leading to a massive disruption in the protein conformation. The resulting proteins, which are nonfunctional due to nonsense mutations in tumors, offer a promising chemotherapy strategy since tumors with nonsense mutations may be more sensitive to anticancer drugs than wild-type ABCC1-expressing tumors. This could provide a novel tumor-specific toxicity strategy and a way to overcome drug resistance.

High expression of interleukin-enhancer binding factor 3 predicts poor prognosis in patients with lung adenocarcinoma

Interleukin-enhancer binding factor 3 (ILF3) is a double-stranded RNA-binding protein that has been reported to contribute to the occurrence and progression of various malignant tumors. The aim of the present study was to evaluate the prognostic value of ILF3 and to apply this knowledge to avoid excessive medical treatment in patients with lung adenocarcinoma (LUAD). ILF3 expression in a discovery set consisting of tumor and peri-tumor tissue microarrays was analyzed using immunohistochemical methods. The mRNA level of ILF3 was subsequently analyzed in a validation set downloaded from The Cancer Genome Atlas. The Kaplan-Meier method, univariate and multivariate Cox analyses, decision curve analysis and nomogram models were used to evaluate the prognostic value of ILF3. ILF3 expression was upregulated in tumor tissues compared with peri-tumor tissues and was negatively associated with the overall survival time of patients with LUAD in the discovery and validation sets. Moreover, ILF3 expression was used for risk stratification in patients with tumor-node-metastasis stages II-IV and poor-to-moderate tumor differentiation. ILF3 expression was identified as an independent predictor of adverse prognosis for patients with LUAD in the discovery and validation sets. Finally, nomogram models for the 3- and 5 year survival time of patients with LUAD revealed that ILF3 expression may be used to improve the predictive accuracy of the prognosis and to avoid excessive medical treatment for certain patients with the disease. Overall, the data obtained in the current study revealed that high ILF3 expression was associated with poor prognosis, and demonstrated that ILF3, as a potential independent risk factor, may improve the hierarchical postoperative management of patients with LUAD.

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 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.

PIDD interaction with KEAP1 as a new mutation-independent mechanism to promote NRF2 stabilization and chemoresistance in NSCLC

Chemotherapy resistance is a major problem in non-small cell lung cancer (NSCLC) treatment. A major mechanism of chemoresistance involves stabilization of the NRF2 transcription factor. NRF2 levels are normally tightly regulated through interaction with KEAP1, an adaptor that targets NRF2 to the CUL3 E3 ubiquitin ligase for proteolysis. In NSCLC, aberrant NRF2 stabilization is best understood through mutations in NRF2, KEAP1, or CUL3 that disrupt their interaction. Biochemical studies, however, have revealed that NRF2 can also be stabilized through expression of KEAP1-interacting proteins that competitively sequester KEAP1 away from NRF2. Here, we have identified PIDD, as a novel KEAP1-interactor in NSCLC that regulates NRF2. We show that this interaction allows PIDD to reduce NRF2 ubiquitination and increase its stability. We also demonstrate that PIDD promotes chemoresistance in NSCLC cells both in vitro and in vivo, and that this effect is dependent on NRF2. Finally, we report that NRF2 protein expression in a NSCLC cohort exceeds the typical incidence of combined NRF2, KEAP1, and CUL3 mutations, and that NRF2 expression in this cohort is correlated with PIDD levels. Our data identify PIDD as a new NRF2 regulator, and suggest that variations in PIDD levels contribute to differential chemosensitivities among NSCLC patients.

Effects of Proanthocyanidins on Arsenic Methylation Metabolism and Efflux in Human Hepatocytes L-02

This study investigated the effects of proanthocyanidins (PC) on arsenic methylation metabolism and efflux in human hepatocytes (L-02), as well as the relationships between PC and GSH, MRP1 and other molecules. Cells were randomly divided into blank control group, arsenic trioxide exposure group (ATO, As₂O₃, 25μmol/L), and PC-treated arsenic exposure group (10, 25, 50mg/L). After 24/48h, the contents of different forms of arsenic were determined, and the methylation indexes were calculated. Intracellular S-adenosyl methionine (SAM), arsenic (+3 oxidation state) methyltransferase (AS3MT), multidrug resistance-associated protein 1 (MRP1), and reduced glutathione (GSH) were ascertained. Changing trends were observed and the correlation between arsenic metabolism and efflux related factors and arsenic metabolites was analyzed. We observed that cells showed increased levels of content/constituent ratio of methyl arsenic, primary/secondary methylation index, methylation growth efficiency/rate, and the difference of methyl arsenic content in cells and culture medium (P<0.05, resp.). Compared with ATO exposure group, the intracellular SAM content in PC-treated group decreased, and the contents of GSH, AS3MT, and MRP1 increased (P<0.05, resp.). There was a positive correlation between the content of intracellular GSH/AS3MT and methyl arsenic. The content of MRP1 was positively correlated with the difference of methyl arsenic content in cell and culture medium; conversely, the SAM content was negatively correlated with intracellular methyl arsenic content (P<0.05, resp.). Taken together, these results prove that PC can promote arsenic methylation metabolism and efflux in L-02 cells, which may be related to the upregulation of GSH, MRP1, and AS3MT levels by PC.

MRP1 modulators synergize with buthionine sulfoximine to exploit collateral sensitivity and selectively kill MRP1-expressing cancer cells

Members of the ABC transporter family, particularly P-glycoprotein (P-gp, ABCB1), breast cancer resistance protein (BCRP, ABCG2) and multidrug resistance protein 1 (MRP1, ABCC1) are well characterized mediators of multidrug resistance, however their pharmacological inhibition has so far failed as a clinical strategy. Harnessing collateral sensitivity, a form of synthetic lethality where cells with acquired multidrug resistance exhibit hypersensitivity to unrelated agents, may be an alternative approach to targeting multidrug resistant tumour cells. We characterized a novel small molecule modulator that selectively enhanced MRP1-dependent efflux of reduced glutathione (GSH), an endogenous MRP1 substrate. Using cell lines expressing high levels of endogenous MRP1 from three difficult to treat cancer types-lung cancer, ovarian cancer and high-risk neuroblastoma-we showed that the MRP1 modulator substantially lowered intracellular GSH levels as a single agent. The effect was on-target, as MRP1 knockdown abolished GSH depletion. The MRP1 modulator was synergistic with the GSH synthesis inhibitor buthionine sulfoximine (BSO), with the combination exhausting intracellular GSH, increasing intracellular reactive oxygen species (ROS) and abolishing clonogenic capacity. Clonogenicity was rescued by the ROS scavenger N-acetylcysteine, implicating GSH depletion in the effect. The MRP1 modulator in combination with BSO also strongly sensitized cancer cells to MRP1-substrate chemotherapeutic agents, particularly arsenic trioxide, and was more effective than either the MRP1 modulator or BSO alone. GSH-depleting MRP1 modulators may therefore provide an enhanced therapeutic window to treat chemo-resistant MRP1-overexpressing pediatric and adult cancers.

ABC Transporters: Regulation and Association with Multidrug Resistance in Hepatocellular Carcinoma and Colorectal Carcinoma

For most cancers, the treatment of choice is still chemotherapy despite its severe adverse effects, systemic toxicity and limited efficacy due to the development of multidrug resistance (MDR). MDR leads to chemotherapy failure generally associated with a decrease in drug concentration inside cancer cells, frequently due to the overexpression of ABC transporters such as P-glycoprotein (P-gp/MDR1/ABCB1), multidrug resistance-associated proteins (MRPs/ABCCs), and breast cancer resistance protein (BCRP/ABCG2), which limits the efficacy of chemotherapeutic drugs. The aim of this review is to compile information about transcriptional and post-transcriptional regulation of ABC transporters and discuss their role in mediating MDR in cancer cells. This review also focuses on drug resistance by ABC efflux transporters in cancer cells, particularly hepatocellular carcinoma (HCC) and colorectal carcinoma (CRC) cells. Some aspects of the chemotherapy failure and future directions to overcome this problem are also discussed.

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.

Effect of the Nrf2-ARE signaling pathway on biological characteristics and sensitivity to sunitinib in renal cell carcinoma

The aim of the present study was to examine the effects of the nuclear factor erythroid-2 related factor 2-antioxidant-responsive element (Nrf2-ARE) signaling pathway on the biological characteristics and sensitivity to targeted therapy in human renal cell carcinoma (RCC) cells. RCC tissues and adjacent tissues were collected and assessed by immunohistochemistry to determine the expression of Nrf2, NAD(P)H dehydrogenase [quinone] 1 (NQO1) and heme oxygenase-1 (HO-1) to analyze the clinicopathological features of RCC. A series of in vitro experiments were conducted to analyze the biological characteristics of Nrf2-ARE signaling in RCC. The renal cancer cell line, 786-0 was used, and cells was divided into a mock group, negative control group and small hairpin (sh)RNA-Nrf2 group. A Cell Counting Kit-8 assay was performed alongside flow cytometry to detect cell viability, cell cycle stage and apoptosis following treatment with sunitinib. The results demonstrated that Nrf2, NQO1 and HO-1 were significantly upregulated in RCC tissues compared with adjacent tissues and were associated with tumor node metastasis stage, Fuhrman classification and lymph node metastasis. Following shRNA-Nrf2 transfection, the 786-0 cells demonstrated a significant decrease in viability, cell invasion and scratch healing rate, and the mRNA and protein expression levels of Nrf2, NQO1, HO-1 and glutathione transferase were significantly decreased, which enhanced the sensitivity to sunitinib, arrested cells in the G0/G1 phase and increased apoptosis. In conclusion, Nrf2-ARE signaling is important for RCC progression, and its inhibition may increase sensitivity to targeted drugs to provide novel developments for RCC treatment.

Emerging role of nuclear factor erythroid 2-related factor 2 in the mechanism of action and resistance to anticancer therapies

Nuclear factor E2-related factor 2 (NRF2), a transcription factor, is a master regulator of an array of genes related to oxidative and electrophilic stress that promote and maintain redox homeostasis. NRF2 function is well studied in in vitro, animal and general physiology models. However, emerging data has uncovered novel functionality of this transcription factor in human diseases such as cancer, autism, anxiety disorders and diabetes. A key finding in these emerging roles has been its constitutive upregulation in multiple cancers promoting pro-survival phenotypes. The survivability pathways in these studies were mostly explained by classical NRF2 activation involving KEAP-1 relief and transcriptional induction of reactive oxygen species (ROS) neutralizing and cytoprotective drug-metabolizing enzymes (phase I, II, III and 0). Further, NRF2 status and activation is associated with lowered cancer therapeutic efficacy and the eventual emergence of therapeutic resistance. Interestingly, we and others have provided further evidence of direct NRF2 regulation of anticancer drug targets like receptor tyrosine kinases and DNA damage and repair proteins and kinases with implications for therapy outcome. This novel finding demonstrates a renewed role of NRF2 as a key modulatory factor informing anticancer therapeutic outcomes, which extends beyond its described classical role as a ROS regulator. This review will provide a knowledge base for these emerging roles of NRF2 in anticancer therapies involving feedback and feed forward models and will consolidate and present such findings in a systematic manner. This places NRF2 as a key determinant of action, effectiveness and resistance to anticancer therapy.