Nrf2/P–glycoprotein axis is associated with clinicopathological characteristics in colorectal cancer

Three Ru(II) complexes modulate the antioxidant transcription factor Nrf2 to overcome cisplatin resistance

Here, we designed, synthesized and characterized three new cyclometalated Ru(II) complexes, [Ru(phen)2(1-(4-Ph-Ph)-IQ)]+ (phen = 1,10-phenanthroline, IQ = isoquinoline, RuIQ9), [Ru(phen)2(1-(4-Ph-Ph)-7-OCH3-IQ)]+ (RuIQ10), and [Ru(phen)2(1-(4-Ph-Ph)-6,7-(OCH3)2-IQ)]+ (RuIQ11). The cytotoxicity experiments conducted on both 2D and 3D multicellular tumor spheroids (MCTSs) indicated that complexes RuIQ9-11 exhibited notably higher cytotoxicity against A549 and A549/DDP cells when compared to the ligands and precursor compounds as well as clinical cisplatin. Moreover, the Ru(II) complexes displayed low toxicity when tested on normal HBE cells in vitro and exposed to zebrafish embryos in vivo. In addition, complexes RuIQ9-11 could inhibit A549 and A549/DDP cell migration and proliferation by causing cell cycle arrest, mitochondrial dysfunction, and elevating ROS levels to induce apoptosis in these cells. Mechanistic studies revealed that RuIQ9-11 could suppress the expression of Nrf2 and its downstream antioxidant protein HO-1 by inhibiting Nrf2 gene transcription in drug-resistant A549/DDP cells. Simultaneously, they inhibited the expression of efflux proteins MRP1 and p-gp in drug-resistant cells, ensuring the accumulation of the complexes within the cells. This led to an increase in intracellular ROS levels in drug-resistant cells, ultimately causing damage and cell death, thus overcoming cisplatin resistance. More importantly, RuIQ11 could effectively inhibit the migration and proliferation of drug-resistant cells within zebrafish, addressing the issue of cisplatin resistance. Accordingly, the prepared Ru(II) complexes possess significant potential for development as highly effective and low-toxicity lung cancer therapeutic agents to overcome cisplatin resistance.

Prediction and verification of targets for α-hederin/oxaliplatin dual-loaded rHDL modified liposomes: Reversing effector T-cells dysfunction and improving anti-COAD efficiency in vitro and in vivo

This study tried to develop the α-Hederin/Oxaliplatin (OXA) dual-loaded rHDL (α-Hederin-OXA-rHDL) modified liposomes to improve the therapeutic index on colon adenocarcinoma (COAD). The α-Hederin-OXA-rHDL were prepared and evaluated for characterizations, accumulate to tumor tissues, and antitumor activity. A thorough investigation into oxaliplatin resistant and KRAS-mutant related hub keg genes were identified and performed to assess the prognosis role of the genetic signature in COAD. The potential immune signatures and molecular docking for verifing the predicted targets of α-Hederin-OXA-rHDL in tumor-bearing mice. Results suggested that α-Hederin-OXA-rHDL could enhance the sensitivity of oxaliplatin in HCT116/L-OHP cells via the regulation of KEAP1/NRF2 -mediated signaling and HO1 or GPX4 proteins. Furthermore, α-Hederin-OXA-rHDL regulated the predicted targets of PRDM1 interaction with miR-140-5p, efficient activing CD8 T cell to improve therapeutic response in vivo. Collectively, this work provides drug delivery with rHDL dual-loaded α-Hederin and oxaliplatin synergistically targets cancer cells and effectory T cells combating COAD.

The Dual Role of NRF2 in Colorectal Cancer: Targeting NRF2 as a Potential Therapeutic Approach

Colorectal cancer (CRC), as the third most common bisexual cancer worldwide, requires urgent research on its underlying mechanisms and intervention methods. NRF2 is an important transcription factor involved in the regulation of redox homeostasis, protein degradation, DNA repair, and other cancer processes, playing an important role in cancer. In recent years, the complex role of NRF2 in CRC has been continuously revealed: on the one hand, it exhibits a chemopreventive effect on cancer by protecting normal cells from oxidative stress, and on the other hand, it also exhibits a protective effect on malignant cells. Therefore, this article explores the dual role of NRF2 and its related signaling pathways in CRC, including their chemical protective properties and promoting effects in the occurrence, development, metastasis, and chemotherapy resistance of CRC. In addition, this article focuses on exploring the regulation of NRF2 in CRC ferroptosis, as well as NRF2 drug modulators (activators and inhibitors) targeting CRC, including natural products, compounds, and traditional Chinese medicine formulations.

Loss of monopolar spindle-binding protein 3B expression promotes colorectal cancer invasiveness by activation of target of rapamycin kinase/autophagy signaling

BACKGROUND

Monopolar spindle-binding protein 3B (MOB3B) functions as a signal transducer and altered MOB3B expression is associated with the development of human cancers.

AIM

To investigate the role of MOB3B in colorectal cancer (CRC).

METHODS

This study collected 102 CRC tissue samples for immunohistochemical detection of MOB3B expression for association with CRC prognosis. After overexpression and knockdown of MOB3B expression were induced in CRC cell lines, changes in cell viability, migration, invasion, and gene expression were assayed. Tumor cell autophagy was detected using transmission electron microscopy, while nude mouse xenograft experiments were performed to confirm the in-vitro results.

RESULTS

MOB3B expression was reduced in CRC vs normal tissues and loss of MOB3B expression was associated with poor CRC prognosis. Overexpression of MOB3B protein in vitro attenuated the cell viability as well as the migration and invasion capacities of CRC cells, whereas knockdown of MOB3B expression had the opposite effects in CRC cells. At the molecular level, microtubule-associated protein light chain 3 II/I expression was elevated, whereas the expression of matrix metalloproteinase (MMP)2, MMP9, sequestosome 1, and phosphorylated mechanistic target of rapamycin kinase (mTOR) was downregulated in MOB3B-overexpressing RKO cells. In contrast, the opposite results were observed in tumor cells with MOB3B knockdown. The nude mouse data confirmed these in-vitro findings, i.e., MOB3B expression suppressed CRC cell xenograft growth, whereas knockdown of MOB3B expression promoted the growth of CRC cell xenografts.

CONCLUSION

Loss of MOB3B expression promotes CRC development and malignant behaviors, suggesting a potential tumor suppressive role of MOB3B in CRC by inhibition of mTOR/autophagy signaling.

The role of exosomes in cancer biology by shedding light on their lipid contents

Exosomes are extracellular bilayer membrane nanovesicles released by cells after the fusion of multivesicular bodies (MVBs) with the plasma membrane. One of the interesting features of exosomes is their ability to carry and transfer various molecules, including lipids, proteins, nucleic acids, and therapeutic cargoes among cells. As intercellular signaling organelles, exosomes participate in various signaling processes such as tumor growth, metastasis, angiogenesis, epithelial-to-mesenchymal transition (EMT), and cell physiology such as cell-to-cell communication. Moreover, these particles are considered good vehicles to shuttle vaccines and drugs for therapeutic applications regarding cancers and tumor cells. These bioactive vesicles are also rich in various lipid molecules such as cholesterol, sphingomyelin (SM), glycosphingolipids, and phosphatidylserine (PS). These lipids play an important role in the formation, release, and function of the exosomes and interestingly, some lipids are used as biomarkers in cancer diagnosis. This review aimed to focus on exosomes lipid content and their role in cancer biology.

Alkaloids as Natural NRF2 Inhibitors: Chemoprevention and Cytotoxic Action in Cancer

Being a controller of cytoprotective actions, inflammation, and mitochondrial function through participating in the regulation of multiple genes in response to stress-inducing endogenous or exogenous stressors, the transcription factor Nuclear Factor Erythroid 2-Related Factor 2 (NRF2) is considered the main cellular defense mechanism to maintain redox balance at cellular and tissue level. While a transient activation of NRF2 protects normal cells under oxidative stress, the hyperactivation of NRF2 in cancer cells may help them to survive and to adapt under oxidative stress. This can be detrimental and related to cancer progression and chemotherapy resistance. Therefore, inhibition of NRF2 activity may be an effective approach for sensitizing cancer cells to anticancer therapy. In this review, we examine alkaloids as NRF2 inhibitors from natural origin, their effects on cancer therapy, and/or as sensitizers of cancer cells to anticancer chemotherapeutics, and their potential clinical applications. Alkaloids, as inhibitor of the NRF2/KEAP1 signaling pathway, can have direct (berberine, evodiamine, and diterpenic aconitine types of alkaloids) or indirect (trigonelline) therapeutic/preventive effects. The network linking alkaloid action with oxidative stress and NRF2 modulation may result in an increased NRF2 synthesis, nuclear translocation, as well in a downstream impact on the synthesis of endogenous antioxidants, effects strongly presumed to be the mechanism of action of alkaloids in inducing cancer cell death or promoting sensitivity of cancer cells to chemotherapeutic agents. In this regard, the identification of additional alkaloids targeting the NRF2 pathway is desirable and the information arising from clinical trials will reveal the potential of these compounds as a promising target for anticancer therapy.

Chalcones and Gastrointestinal Cancers: Experimental Evidence

Colorectal (CRC) and gastric cancers (GC) are the most common digestive tract cancers with a high incidence rate worldwide. The current treatment including surgery, chemotherapy or radiotherapy has several limitations such as drug toxicity, cancer recurrence or drug resistance and thus it is a great challenge to discover an effective and safe therapy for CRC and GC. In the last decade, numerous phytochemicals and their synthetic analogs have attracted attention due to their anticancer effect and low organ toxicity. Chalcones, plant-derived polyphenols, received marked attention due to their biological activities as well as for relatively easy structural manipulation and synthesis of new chalcone derivatives. In this study, we discuss the mechanisms by which chalcones in both in vitro and in vivo conditions suppress cancer cell proliferation or cancer formation.

FXR1 facilitates axitinib resistance in clear cell renal cell carcinoma via regulating KEAP1/Nrf2 signaling pathway

Axitinib is emerging as a first-line combination treatment drug for metastatic renal cell carcinoma, but the acquired resistance significantly bothers the treatment efficacy. This article is to investigate the impact of fragile X mental retardation autosomal homolog 1 (FXR1) and its mechanistic involvement with Kelch-like epoxy chloropropan-associated protein 1 (KEAP1)/NF-E2-related factor 2 (Nrf2) pathway on cell resistance to axitinib in clear cell renal cell carcinoma (ccRCC). Establishment of axitinib resistance cells (786-O, Caki-1, 786-O/axitinib, or Caki-1/axitinib) was made, and the cells were then transfected with sh-FXR1, or co-transfected with sh-FXR1 and sh-KEAP1. The quantitative real-time PCR (qRT-PCR) and western blotting assays were employed to measure the expression of FXR1, KEAP1, Nrf2, LC3 II/I, Beclin 1, p62, MDR-1, and MRP-1. In addition, the binding between FXR1 and KEAP1 was verified by RNA-immunoprecipitation and RNA pull-down assays, and FXR1-dependent KEAP1 mRNA degradation was determined. Herein, FXR1 was demonstrated to be overexpressed in ccRCC cells, and showed higher expression in 786-O/axitinib and Caki-1/axitinib cells. Mechanistically, FXR1 enriched KEAP1 mRNA, and pulled downed by biotinylated KEAP1 probes. Results of RNA stability assay reveled that KEAP mRNA stability was suppressed by FXR1. Furthermore, knockdown of FXR1 promoted cell apoptosis and showed a restrained feature on cell resistance to axitinib. Of note, KEAP1 knockdown suppressed cell autophagy, oxidative stress, resistance to axitinib, and promoted apoptosis, despite FXR1 was downregulated in ccRCC cells. In conclusion, FXR1 played an encouraging role in ccRCC cell resistance to axitinib by modulating KEAP/Nrf2 pathway.

Targeting critical pathways in ferroptosis and enhancing antitumor therapy of Platinum drugs for colorectal cancer

Colorectal cancer (CRC) can be resistant to platinum drugs, possibly through ferroptosis suppression, albeit the need for further work to completely understand this mechanism. This work aimed to sum up current findings pertaining to oxaliplatin resistance (OR) or resistance to ascertain the potential of ferroptosis to regulate oxaliplatin effects. In this review, tumor development relating to iron homeostasis, which includes levels of iron that ascertain cells' sensitivity to ferroptosis, oxidative stress, or lipid peroxidation in colorectal tumor cells that are connected with ferroptosis initiation, especially the role of c-Myc/NRF2 signaling in regulating iron homeostasis, coupled with NRF2/GPX4-mediated ferroptosis are discussed. Importantly, ferroptosis plays a key role in OR and ferroptotic induction may substantially reverse OR in CRC cells, which in turn could inhibit the imbalance of intracellular redox induced by oxaliplatin and ferroptosis, as well as cause chemotherapeutic resistance in CRC. Furthermore, fundamental research of small molecules, ferroptosis inducers, GPX4 inhibitors, or natural products for OR coupled with their clinical applications in CRC have also been summarized. Also, potential molecular targets and mechanisms of small molecules or drugs are discussed as well. Suggestively, OR of CRC cells could significantly be reversed by ferroptosis induction, wherein this result is discussed in the current review. Prospectively, the existing literature discussed in this review will provide a solid foundation for scientists to research the potential use of combined anticancer drugs which can overcome OR via targeting various mechanisms of ferroptosis. Especially, promising therapeutic strategies, challenges ,and opportunities for CRC therapy will be discussed.

Nrf2/p‑Fyn/ABCB1 axis accompanied by p‑Fyn nuclear accumulation plays pivotal roles in vinorelbine resistance in non‑small cell lung cancer

Adjuvant cisplatin‑vinorelbine is a standard therapy for stage II/III lung cancer. However, a poor survival rate of patients with lung cancer is attributed to vinorelbine resistance arising from ATP‑binding cassette (ABC) sub‑family B member 1 (ABCB1) and phosphorylated Fyn (p‑Fyn) overexpression. However, the underlying mechanisms remain unclear. NF‑E2‑related factor 2 (Nrf2) regulates the ABC family and activates the nuclear transport of Fyn. The present study evaluated the roles of the Nrf2/p‑Fyn/ABCB1 axis in vinorelbine‑resistant (VR) cells and clinical samples. To establish VR cells, H1299 cells were exposed to vinorelbine, and the intracellular reactive oxygen species (ROS) level in the H1299 cells was determined using a DCFH‑DA assay. The total and subcellular expression of Nrf2, ABCB1 and p‑Fyn in VR cells was evaluated. Immunofluorescence was used to detect the subcellular localization of p‑Fyn in VR cells. A cell viability assay was used to examine whether the sensitivity of VR cells to vinorelbine is dependent on Nrf2 activity. Immunohistochemistry was performed on 104 tissue samples from patients with lung cancer who underwent surgery followed by cisplatin‑vinorelbine treatment. The results revealed that persistent exposure to vinorelbine induced intracellular ROS formation in H1299 cells. p‑Fyn was localized in the nucleus, and ABCB1 and Nrf2 were overexpressed in VR cells. ABCB1 expression was dependent on Nrf2 downstream activation. The decreased expression of Nrf2 restored the sensitivity of VR cells to vinorelbine. In the surgical samples, Nrf2 and ABCB1 were associated with disease‑free survival, and p‑Fyn was associated with overall survival (P<0.05). On the whole, the present study demonstrates that Nrf2 upregulates ABCB1 and, accompanied by the nuclear accumulation of p‑Fyn, induces vinorelbine resistance. These findings may facilitate the development of drug resistance prevention strategies or new drug targets against non‑small cell lung cancer.

An update of Nrf2 activators and inhibitors in cancer prevention/promotion

NF-E2-related factor 2 (Nrf2) protein is a basic-region leucine zipper transcription factor that defends against endogenous or exogenous stressors. By inducing several cytoprotective and detoxifying gene expressions, Nrf2 can increase the sensitivity of the cells to oxidants and electrophiles. Transient Nrf2 activation, by its specific activators, has protective roles against carcinogenesis and cancer development. However, permanent activation of Nrf2 promotes various cancer properties, comprising malignant progression, chemo/radio resistance, and poor patient prognosis. Taken together, these findings suggest that reaching an optimal balance between paradoxical functions of Nrf2 in malignancy may render a selective improvement to identify therapeutic strategies in cancer treatment. In this review, we describe lately discovered Nrf2 inducers and inhibitors, and their chemopreventive and/or anticancer activities.

The Nrf2 pathway signifies one of the most significant cell defense procedures against exogenous or endogenous stressors. Certainly, by increasing the expression of several cytoprotective genes, the transcription factor Nrf2 can shelter cells and tissues from multiple sources of damage including electrophilic, xenobiotic, metabolic, and oxidative stress. Notably, the aberrant activation or accumulation of Nrf2, a common event in many tumors, confers a selective advantage to cancer cells and is connected to malignant progression, therapy resistance, and poor prognosis. Therefore, lately, Nrf2 has arisen as a hopeful target in treatment of cancer, and many struggles have been made to detect therapeutic strategies intended at disrupting its pro-oncogenic role. By summarizing the outcomes from past and recent studies, this review provided an overview concerning the Nrf2 pathway and the molecular mechanisms causing Nrf2 hyperactivation in cancer cells. Finally, this paper also described 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.

Dynamic modeling of Nrf2 pathway activation in liver cells after toxicant exposure

Cells are exposed to oxidative stress and reactive metabolites every day. The Nrf2 signaling pathway responds to oxidative stress by upregulation of antioxidants like glutathione (GSH) to compensate the stress insult and re-establish homeostasis. Although mechanisms describing the interaction between the key pathway constituents Nrf2, Keap1 and p62 are widely reviewed and discussed in literature, quantitative dynamic models bringing together these mechanisms with time-resolved data are limited. Here, we present an ordinary differential equation (ODE) based dynamic model to describe the dynamic response of Nrf2, Keap1, Srxn1 and GSH to oxidative stress caused by the soft-electrophile diethyl maleate (DEM). The time-resolved data obtained by single-cell confocal microscopy of green fluorescent protein (GFP) reporters and qPCR of the Nrf2 pathway components complemented with siRNA knock down experiments, is accurately described by the calibrated mathematical model. We show that the quantitative model can describe the activation of the Nrf2 pathway by compounds with a different mechanism of activation, including drugs which are known for their ability to cause drug induced liver-injury (DILI) i.e., diclofenac (DCF) and omeprazole (OMZ). Finally, we show that our model can reveal differences in the processes leading to altered activation dynamics amongst DILI inducing drugs.

In vitro exosomal transfer of Nrf2 led to the oxaliplatin resistance in human colorectal cancer LS174T cells

Chemotherapy resistance is a serious pitfall in the treatment of colon cancers (CCs). Previous studies have found that exosomes (Exo) play a pivotal role in tumor drug resistance via the transfer of proteins and genetic materials to the acceptor cells. To date, the mechanisms orchestrating Exo-derived resistance in cancer cells have been the center of attention. Herein, we aimed to evaluate the role of exosomal nuclear factor erythroid 2-related factor 2 (Nrf2) on oxaliplatin (1-OHP) resistance in human colorectal cancer LS174T cells in vitro. To this end, exosomal-Nrf2-mediated 1-OHP resistance was examined using different assays. Exo was isolated from resistant LS174T cells (LS174T/R) and added to the culture medium of sensitive LS174T cells (LS174T/S). According to our data, LS174T/S cells successfully adsorbed PKH26-Exo driven from LS174T/R cells. Western blotting showed an increased Nrf2 level in Exo isolated from LS174T/R cells compared to LS174T/S cell-derived Exo (p < .05). The incubation of LS174T/S cells with LS174T/R-derived Exo increased half-maximal inhibitory concentration values in response to treatment with 1-OHP (p < .05). Besides this, the apoptotic changes were diminished in LS174T/S cells after incubation with LS174T/R-derived Exo. Of note, the exposure of LS174T/S cells to LS174T/R cell-derived Exo increased the expression of Nrf2 and P-glycoprotein (P-gp) compared to the nontreated LS174T/S cells (p < .05). In line with these changes, lower intracellular Rhodamin 123 content was detected in Exo-treated cells compared to the nontreated LS174T/S cells. Exo increased migration and clonogenic capacity of LS174T/S cells after incubation with Exo-derived from resistant cells. Of note, inhibition of Nrf2 with a specific blocker, brusatol, blunted these effects. Taken together, Exo-mediated transfer of Nrf2 is involved in the development of oxaliplatin resistance in CC cells by upregulating P-gp.

Oxidative Stress and Cancer Heterogeneity Orchestrate NRF2 Roles Relevant for Therapy Response

Oxidative stress and its end-products, such as 4-hydroxynonenal (HNE), initiate activation of the Nuclear Factor Erythroid 2-Related Factor 2 (NRF2)/Kelch Like ECH Associated Protein 1 (KEAP1) signaling pathway that plays a crucial role in the maintenance of cellular redox homeostasis. However, an involvement of 4-HNE and NRF2 in processes associated with the initiation of cancer, its progression, and response to therapy includes numerous, highly complex events. They occur through interactions between cancer and stromal cells. These events are dependent on many cell-type specific features. They start with the extent of NRF2 binding to its cytoplasmic repressor, KEAP1, and extend to the permissiveness of chromatin for transcription of Antioxidant Response Element (ARE)-containing genes that are NRF2 targets. This review will explore epigenetic molecular mechanisms of NRF2 transcription through the specific molecular anatomy of its promoter. It will explain the role of NRF2 in cancer stem cells, with respect to cancer therapy resistance. Additionally, it also discusses NRF2 involvement at the cross-roads of communication between tumor associated inflammatory and stromal cells, which is also an important factor involved in the response to therapy.

Hepatocyte nuclear factor 4 gamma (HNF4G) is correlated with poor prognosis and promotes tumor cell growth by inhibiting caspase-dependent intrinsic apoptosis in colorectal cancer

The hepatocyte nuclear factor 4 gamma (HNF4G), a member of orphan nuclear receptors, is up-regulated and functions as an oncoprotein in a variety of tumors. Recent advances in understanding the biologic function and action mechanism of HNF4G in colorectal cancer (CRC) have not been fully elucidated. In the present study, we observed that HNF4G expression levels were significantly increased in CRC tissues compared with adjacent normal tissues, and HNF4G overexpression correlated with worse prognosis in colorectal cancer. Transfection with a small interference RNA (siRNA) targeting HNF4G in HCT116 and SW480 CRC cell lines significantly inhibited cell proliferation and promoted apoptosis in vitro. In contrast, overexpression of HNF4G increased cell proliferation and decreased the percentage of apoptotic cells. Moreover, we discovered that HNF4G was involved in CRC cell apoptosis via the caspase-dependent intrinsic pathway. Finally, knockdown of HNF4G expression led to attenuated colorectal cancer growth and promoted apoptosis in a xenograft mouse model. Collectively, these results indicate that HNF4G exerts as an oncogenic role in colorectal cancer and provides a potential therapeutic target.

The Impact of Nrf2 Silencing on Nrf2-PD-L1 Axis to Overcome Oxaliplatin Resistance and Migration in Colon Cancer Cells

Background:

Nuclear factor-erythroid 2-related factor 2 (Nrf2) plays a key role in promoting chemoresistance in various cancers. PD-L1 is one of the downstream targets of the Nrf2 signaling pathway. This molecule has some beneficial impacts on tumors growth by inhibition of the immune system. This study aimed to investigate the potential role of the Nrf2-PD-L1 axis in the promotion of oxaliplatin resistance in colon cancer cells.

Methods:

We examined Nrf2, PD- L1, and CD80 expression in the tumor and margin tissue samples from CRC patients. After that role of the Nrf2-PD-L1 axis in promotion of Oxaliplatin resistance was investigated.

Results:

Our data revealed that Nrf2 and PD-L1 mRNA expressions were markedly higher in tumor tissues compared to margin tissues. The PD-L1 mRNA expression level was also increased in the resistant cells. However, Nrf2 expression was decreased in SW480/Res cells and increased in LS174T/Res cells. The inhibition of Nrf2 through siRNA treatment in SW480/Res and LS174T/Res cells has decreased the IC50 values of oxaliplatin. Inhibition of the Nrf2 has significantly increased the oxaliplatin-induced apoptosis, and reduced the migration in SW480/Res cells.

Conclusion:

It is suggested that effective inhibition of Nrf2-PD-L1 signaling pathways can be considered as a novel approach to improve oxaliplatin efficacy in colon cancer patients.

Reactive oxygen species in cancer: Current findings and future directions

Reactive oxygen species (ROS), a class of highly bioactive molecules, have been widely studied in various types of cancers. ROS are considered to be normal byproducts of numerous cellular processes. Typically, cancer cells exhibit higher basal levels of ROS compared with normal cells as a result of an imbalance between oxidants and antioxidants. ROS have a dual role in cell metabolism: At low to moderate levels, ROS act as signal transducers to activate cell proliferation, migration, invasion, and angiogenesis. In contrast, high levels of ROS cause damage to proteins, nucleic acids, lipids, membranes, and organelles, leading to cell death. Extensive studies have revealed that anticancer therapies that manipulate ROS levels, including immunotherapies, show promising in vitro as well as in vivo results. In this review, we summarize molecular mechanisms and oncogenic functions that modulate ROS levels and are useful for the development of cancer therapeutic strategies. This review also provides insights into the future development of effective agents that regulate the redox system for cancer treatment.

hTERT Promotes CRC Proliferation and Migration by Recruiting YBX1 to Increase NRF2 Expression

High human telomerase reverse transcriptase (hTERT) expression is related to severe Colorectal Cancer (CRC) progression and negatively related to CRC patient survival. Previous studies have revealed that hTERT can reduce cancer cellular reactive oxygen species (ROS) levels and accelerate cancer progression; however, the mechanism remains poorly understood. NFE2-related factor 2 (NRF2) is a molecule that plays a significant role in regulating cellular ROS homeostasis, but whether there is a correlation between hTERT and NRF2 remains unclear. Here, we showed that hTERT increases CRC proliferation and migration by inducing NRF2 upregulation. We further found that hTERT increases NRF2 expression at both the mRNA and protein levels. Our data also revealed that hTERT primarily upregulates NRF2 by increasing NRF2 promoter activity rather than by regulating NRF2 mRNA or protein stability. Using DNA pull-down/MS analysis, we found that hTERT can recruit YBX1 to upregulate NRF2 promoter activity. We also found that hTERT/YBX1 may localize to the P2 region of the NRF2 promoter. Taken together, our results demonstrate that hTERT facilitates CRC proliferation and migration by upregulating NRF2 expression through the recruitment of the transcription factor YBX1 to activate the NRF2 promoter. These results provide a new theoretical basis for CRC treatment.

Nrf2 Signaling Pathway in Chemoprotection and Doxorubicin Resistance: Potential Application in Drug Discovery

Doxorubicin (DOX) is extensively applied in cancer therapy due to its efficacy in suppressing cancer progression and inducing apoptosis. After its discovery, this chemotherapeutic agent has been frequently used for cancer therapy, leading to chemoresistance. Due to dose-dependent toxicity, high concentrations of DOX cannot be administered to cancer patients. Therefore, experiments have been directed towards revealing underlying mechanisms responsible for DOX resistance and ameliorating its adverse effects. Nuclear factor erythroid 2-related factor 2 (Nrf2) signaling is activated to increase levels of reactive oxygen species (ROS) in cells to protect them against oxidative stress. It has been reported that Nrf2 activation is associated with drug resistance. In cells exposed to DOX, stimulation of Nrf2 signaling protects cells against cell death. Various upstream mediators regulate Nrf2 in DOX resistance. Strategies, both pharmacological and genetic interventions, have been applied for reversing DOX resistance. However, Nrf2 induction is of importance for alleviating side effects of DOX. Pharmacological agents with naturally occurring compounds as the most common have been used for inducing Nrf2 signaling in DOX amelioration. Furthermore, signaling networks in which Nrf2 is a key player for protection against DOX adverse effects have been revealed and are discussed in the current review.

A multiple-targets alkaloid nuciferine overcomes paclitaxel-induced drug resistance in vitro and in vivo

OBJECTIVE

Multidrug resistance (MDR) is the major barrier to the successful treatment of chemotherapy. Compounds from nature products working as MDR sensitizers provided new treatment strategies for chemo-resistant cancers patients.

METHODS

We investigated the reversal effects of nuciferine (NF), an alkaloid from Nelumbo nucifera and Nymphaea caerulea, on the paclitaxel (PTX) resistance ABCB1-overexpressing cancer in vitro and in vivo, and explored the underlying mechanism by evaluating drug sensitivity, cell cycle perturbations, intracellular accumulation, function and protein expression of efflux transporters as well as molecular signaling involved in governing transporters expression and development of MDR in cancer.

RESULTS

NF overcomes the resistance of chemotherapeutic agents included PTX, doxorubicin (DOX), docetaxel, and daunorubicin to HCT-8/T and A549/T cancer cells. Notably, NF suppressed the colony formation of MDR cells in vitro and the tumor growth in A549/T xenograft mice in vivo, which demonstrated a very strong synergetic cytotoxic effect between NF and PTX as combination index (CI) (CI<0.1) indicated. Furthermore, NF increased the intracellular accumulation of P-gp substrates included DOX and Rho123 in the MDR cells and inhibited verapamil-stimulated ATPase activity. Mechanistically, inhibition of PI3K/AKT/ERK pathways by NF suppressed the activation of Nrf2 and HIF-1α, and further reduced the expression of P-gp and BCRP, contributing to the sensitizing effects of NF against MDR in cancer.

CONCLUSION

This novel finding provides a promising treatment strategy for overcoming MDR and improving the efficiency of chemotherapy by using a multiple-targets MDR sensitizer NF.

High NRF2 Levels Correlate with Poor Prognosis in Colorectal Cancer Patients and with Sensitivity to the Kinase Inhibitor AT9283 In Vitro

Aberrant hyperactivation of nuclear factor erythroid 2 (NF-E2) p45-related factor 2 (NRF2) is a common event in many tumour types and associates with resistance to therapy and poor patient prognosis; however, its relevance in colorectal tumours is not well-established. Measuring the expression of surrogate genes for NRF2 activity in silico, in combination with validation in patients' samples, we show that the NRF2 pathway is upregulated in colorectal tumours and that high levels of nuclear NRF2 correlate with a poor patient prognosis. These results highlight the need to overcome the protection provided by NRF2 and present an opportunity to selectively kill cancer cells with hyperactive NRF2. Exploiting the CRISPR/Cas9 technology, we generated colorectal cancer cell lines with hyperactive NRF2 and used them to perform a drug screen. We identified AT9283, an Aurora kinase inhibitor, for its selectivity towards killing cancer cells with hyperactive NRF2 as a consequence to either genetic or pharmacological activation. Our results show that hyperactivation of NRF2 in colorectal cancer cells might present a vulnerability that could potentially be therapeutically exploited by using the Aurora kinase inhibitor AT9283.

Association of tricellulin expression with poor colorectal cancer prognosis and metastasis

Tricellulin is a tight-junction transmembrane protein that regulates cell-cell interactions. Altered tricellulin expression could promote tumor cell invasions and metastasis in human cancers. The present study assessed tricellulin expression in colorectal cancer tissues for any association with clinicopathological features of colorectal cancer patients and then investigated the underlying molecular events using quantitative proteomic analysis and in vitro experiments. Tissue samples from 98 colorectal cancer patients and 15 volunteers were collected for immunohistochemistry. Colorectal cell lines were used to overexpress or knockdown tricellulin expression in various assays. The data revealed that upregulated tricellulin expression was associated with lymph node and distant metastases and poor prognosis, while tricellulin overexpression promoted colorectal cancer cell migration and invasion in vitro. In contrast, tricellulin knockdown had positive effects on the tumor cells. Furthermore, TMT-LC-MS/MS and bioinformatics analyses revealed that tricellulin was involved in EMT and reduction of apoptosis through the NF-κB signaling pathway. These findings highlight for the first time the significance of tricellulin in colorectal cancer development and progression. Further study may validate tricellulin as a novel biomarker and target for colorectal cancer.

MicroRNAs and colorectal cancer chemoresistance: New solution for old problem

BACKGROUND

Colorectal cancer (CRC) is one of the most common gastrointestinal malignancies with a significant mortality rate. Despite the great advances in cancer treatment in the last few decades, effective treatment of CRC is still under challenge. One of the main problems associated with CRC treatment is the resistance of cancer cells to chemotherapy drugs.

METHODS

Many studies have been carried out to identify CRC chemoresistance mechanisms, and shed light on the role of ATP-binding cassette transporters (ABC transporters), enzymes as thymidylate synthase, some signaling pathways, and cancer stem cells (CSC) in chemoresistance and failed CRC chemotherapies. Other studies have also been recently carried out to find solutions to overcome chemoresistance. Some of these studies have identified the role of miRNAs in chemoresistance of the CRC cells and the effective use of these micro-molecules to CRC treatment.

RESULTS

Considering the results of these studies, more focus on miRNAs likely leads to a proper solution to overcome CRC chemoresistance.

CONCLUSION

The current study has reviewed the related literature while discussing the efficacy of miRNAs as potential clinical tools for overcoming CRC chemoresistance and reviewing the most important chemoresistance mechanisms in CRC cells.

PD-1/PD-L1-dependent immune response in colorectal cancer

Colorectal cancer (CRC) is still considered as the third most frequent cancer in the world. Microsatellite instability (MSI), inflammation, and microRNAs have been demonstrated as the main contributing factors in CRC. Subtype 1 CRC is defined by NK cells infiltration, induction of Th1 lymphocyte and cytotoxic T cell responses as well as upregulation of immune checkpoint proteins including programmed cell death-1 (PD-1). Based on the diverse features of CRC, such as the stage and localization of the tumor, several treatment approaches are available. However, the efficiency of these treatments may be decreased due to the development of diverse resistance mechanisms. It has been proven that monoclonal antibodies (mAbs) can increase the effectiveness of CRC treatments. Nowadays, several mAbs including nivolumab and pembrolizumab have been approved for the treatment of CRC. Immune checkpoint receptors including PD-1 can be inhibited by these antibodies. Combination therapy gives an opportunity for advanced treatment for CRC patients. In this review, an update has been provided on the molecular mechanisms involved in MSI colorectal cancer immune microenvironment by focusing on PD-ligand 1 (PD-L1) and treatment of patients with advanced immunotherapy, which were examined in the different clinical trial phases. Considering induced expression of PD-L1 by conventional chemotherapeutics, we have summarized the role of PD-L1 in CRC, the chemotherapy effects on the PD-1/PD-L1 axis and novel combined approaches to enhance immunotherapy of CRC by focusing on PD-L1.

Elevated expression of AGGF1 predicts poor prognosis and promotes the metastasis of colorectal cancer

Background

Angiogenic factor with G-patch and FHA domains 1 (AGGF1) can promote angiogenesis and increasing evidence has highlighted the important roles of AGGF1 in tumorigenesis. However, the differential expression as well as the biological functions of AGGF1 in colorectal cancer (CRC) remain to be established. The purpose of the present study is therefore to identify the effect of AGGF1 on prognosis and metastasis in CRC patients.

Methods

The expression level of AGGF1 in CRC was examined by qPCR, western blot and immunohistochemistry in a tissue microarray containing 236 CRC specimens and paired normal mucosae. And the effect of AGGF1 on CRC cell malignance was investigated in our established stable AGGF1 upregulated and knockdown CRC cell lines.

Results

The expression level of AGGF1 in CRC tissue was not significantly different to that in adjacent normal mucosa at the mRNA level. However, at the protein level, AGGF1 expression in CRC tissues was significantly higher than in paired normal mucosa, which showed a clear association with TNM stage, AJCC stage, vascular invasion, and differentiation. Further, we revealed an apparent correlation between AGGF1 expression and poorer disease-free survival and overall survival of CRC patients. In addition, we discovered that AGGF1 significantly promoted CRC cell wound healing, migration, and invasion in vitro and distant metastasis in vivo.

Conclusions

Our study demonstrates the aberrant overexpression of AGGF1 in CRC and provides a basis on which to explore the application of AGGF1 as a potential therapeutic target for CRC patients, especially for CRC patients with distant metastasis.

Can Nrf2 Modulate the Development of Intestinal Fibrosis and Cancer in Inflammatory Bowel Disease?

One of the main mechanisms carried out by the cells to counteract several forms of stress is the activation of the nuclear factor erythroid 2-related factor (Nrf2) signaling. Nrf2 signaling controls the expression of many genes through the binding of a specific cis-acting element known as the antioxidant response element (ARE). Activation of Nrf2/ARE signaling can mitigate several pathologic mechanisms associated with an autoimmune response, digestive and metabolic disorders, as well as respiratory, cardiovascular, and neurodegenerative diseases. Indeed, several studies have demonstrated that Nrf2 pathway plays a key role in inflammation and in cancer development in many organs, including the intestine. Nrf2 appears to be involved in inflammatory bowel disease (IBD), an immune-mediated chronic and disabling disease, with a high risk of developing intestinal fibrotic strictures and cancer. Currently, drugs able to increase cytoprotective Nrf2 function are in clinical trials or already being used in clinical practice to reduce the progression of some degenerative conditions. The role of Nrf2 in cancer development and progression is controversial, and drugs able to inhibit abnormal levels of Nrf2 are also under investigation. The goal of this review is to analyze and discuss Nrf2-dependent signals in the initiation and progression of intestinal fibrosis and cancers occurring in IBD.

Transcription factor Nrf2 induces the up-regulation of lncRNA TUG1 to promote progression and adriamycin resistance in urothelial carcinoma of the bladder

Background

Taurine-upregulated gene 1 (TUG1) has been documented to be implicated in carcinogenesis and chemoresistance in solid tumors. Here, we explored the biological role and regulatory mechanism of TUG1 in progression and chemoresistance of urothelial carcinoma of the bladder (UCB).

Methods

Nuclear factor-erythroid 2 (NF-E2)-related factor 2 (Nrf2) mRNA and TUG1 expression was determined by quantitative reverse transcription polymerase chain reaction. Western blot was performed to determine the protein levels of Nrf2, p-glycoprotein (p-gp), Ki-67 (Ki67), matrix metalloproteinase (MMP)-2 and MMP-9 and cleaved caspase-3. The effects of either Nrf2 or TUG1 knockdown on the proliferation, invasion, apoptosis and adriamycin (ADM) resistance of UCB cells were evaluated by CCK-8 assay, transwell invasion assay and flow cytometry analysis. Xenograft tumor assay was carried out to confirm the role of Nrf2 and TUG1 in ADM resistance of UCB cells in vivo.

Results

Nrf2 and TUG1 were upregulated in UCB tissues and cell lines. A positive correlation between Nrf2 and TUG1 expression was discovered in UCB tissues. Moreover, Nrf2 and TUG1 expression levels were higher in ADM-resistant cells compared with those in parental cells. Furthermore, Nrf2 positively regulated the expression of TUG1 in UCB cells. Knockdown of either Nrf2 or TUG1 led to the inhibition of cell proliferation and invasion and promotion of cell apoptosis, accompanying with down-regulation of Ki67, MMP-2 and MMP-9 and up-regulation of cleaved caspase-3. Knockdown of either Nrf2 or TUG1 enhanced the sensitivity of BIU-87/ADM and T24/ADM cells to ADM, as indicated by decreased expression of p-gp. Besides, knockdown of either Nrf2 or TUG1 inhibited tumor growth in the absence or presence of ADM in vivo.

Conclusions

Nrf2 induces the up-regulation of TUG1 to promote progression and ADM resistance in UCB.

Upregulation of nectin-4 is associated with ITGB1 and vasculogenic mimicry and may serve as a predictor of poor prognosis in colorectal cancer

Colorectal cancer (CRC) is one of the most common malignancies worldwide. Unlike endothelium-dependent vasculature, vasculogenic mimicry (VM) is an alternative type of blood supply in tumors that is frequently associated with poor patient outcome. Nectin-4 serves a vital role in the formation and maintenance of adherens junctions; integrin β-1 (ITGB1) promotes tumor invasion, metastasis and VM formation. In the present study, the analysis of nectin-4 mRNA expression in a database of The Cancer Genome Atlas (TCGA) was combined with that of another non-overlapping cohort of 68 patients with CRC. TCGA data were used to examine nectin-4 mRNA expression in CRC and its correlation with the clinicopathological features of patients. Data from the non-overlapping cohort of patients was used to determine nectin-4 and ITGB1 protein expression in CRC by immunohistochemical (IHC) staining. Cluster of differentiation 34/periodic acid-Schiff double staining was performed to validate the presence of VM formation. The association with, and significance of combining nectin-4, ITGB1 protein expression and VM formation for predicting patient prognosis was evaluated. The TCGA dataset demonstrated that nectin-4 mRNA was upregulated in CRC, which was significantly relate to lymph node metastasis (P=0.0017), distant metastasis (P=0.0045), and tumor-node-metastasis (TNM) stage (P=0.0015). Of the 68 patients analyzed by IHC staining, 48 (70.6%) were positive for nectin-4, 46 (67.6%) for ITGB1 and 17 (25%) for VM formation. Nectin-4 protein expression was associated with ITGB1 protein expression (P<0.01) and VM formation (P<0.05). Nectin-4, ITGB1 expression and VM formation were associated with distant metastasis stage (P<0.05) and TNM stage (P<0.05). Based on these findings it was concluded that nectin-4 was upregulated in CRC tissues compared with normal mucosal tissues, and was associated with ITGB1 expression and VM formation. Furthermore, nectin-4 and ITGB1 protein expression, together with VM formation may be used to predict poor prognosis in CRC.

Ginsenoside Rg5 overcomes chemotherapeutic multidrug resistance mediated by ABCB1 transporter: in vitro and in vivo study

Background

Multidrug resistance (MDR) to chemotherapy drugs remains a major challenge in clinical cancer treatment. Here we investigated whether and how ginsenoside Rg5 overcomes the MDR mediated by ABCB1 transporter in vitro and in vivo.

Methods

Cytotoxicity and colon formation as well as the intracellular accumulation of ABCB1 substrates were carried out in MDR cancer cells A2780/T and A549/T for evaluating the reversal effects of Rg5. The expressions of ABCB1 and Nrf2/AKT pathway were determined by Western blotting. An A549/T cell xenograft model was established to investigate the MDR reversal activity of Rg5 in vivo.

Results

Rg5 significantly reversed ABCB1-mediated MDR by increasing the intracellular accumulation of ABCB1 substrates without altering protein expression of ABCB1. Moreover, Rg5 activated ABCB1 ATPase and reduced verapamil-stimulated ATPase activity, suggesting a high affinity of Rg5 to ABCB1 binding site which was further demonstrated by molecular docking analysis. In addition, co-treatment of Rg5 and docetaxel (TXT) suppressed the expression of Nrf2 and phosphorylation of AKT, indicating that sensitizing effect of Rg5 associated with AKT/Nrf2 pathway. In nude mice bearing A549/T tumor, Rg5 and TXT treatment significantly suppressed the growth of drug-resistant tumors without increase in toxicity when compared to TXT given alone at same dose.

Conclusion

Therefore, combination therapy of Rg5 and chemotherapy drugs is a strategy for the adjuvant chemotherapy, which encourages further pharmacokinetic and clinical studies.