Dietary phytochemicals targeting Nrf2 for chemoprevention in breast cancer

Chemopreventive effects of atractylenolide-III on mammary tumorigenesis via activation of the Nrf2/ARE pathway through autophagic degradation of Keap1

The incidence of breast cancer is increasing annually, making it a major health threat for women. Chemoprevention using natural, dietary, or synthetic products has emerged as a promising approach to address this growing burden. Atractylenolide-III (AT-III), a sesquiterpenoid present in various medicinal herbs, has demonstrated potential therapeutic effects against several diseases, including tumors, nonalcoholic fatty liver disease, and cerebral ischemic injury. However, its impact on breast cancer chemoprevention remains unexplored. In this study, we used an N-methyl-N-nitrosourea (NMU)-induced rat breast cancer model and 17β-estradiol (E2)-treated MCF-10A cells to evaluate the chemopreventive potential of AT-III on mammary tumorigenesis. AT-III inhibited mammary tumor progression, evidenced by reduced tumor volume and multiplicity, prolonged tumor latency, and the reversal of NMU-induced weight loss. Furthermore, AT-III suppressed NMU-induced inflammation and oxidative stress through the Nrf2/ARE pathway in breast cancer tissues. In vitro, AT-III effectively suppressed E2-induced anchorage-independent growth and cell migration in MCF-10A cells. Nrf2 knockdown attenuated the protective effects of AT-III, highlighting the pivotal role of Nrf2 in AT-III-mediated suppression of tumorigenesis. The mechanism involves the induction of Nrf2 expression by AT-III through the autophagic degradation of Kelch-like ECH-associated protein 1 (Keap1). Overall, the results of this study indicate that AT-III is a promising candidate for breast cancer chemoprevention and provide valuable insights into its molecular interactions and signaling pathways.

Modulation of carcinogenesis with selected GRAS nutraceuticals via Keap1-Nrf2 signaling pathway

Keap1-Nrf2 is a fundamental signaling cascade known to promote or prevent carcinogenesis. Extensive studies identify the key target of modulatory aspects of Keap1-Nrf2 signaling against cancer. Nutraceuticals are those dietary agents with many health benefits that have immense potential for cancer chemoprevention. The nutritional supplements known as nutraceuticals are found to be one of the most promising chemoprevention agents. Upon investigating the dual nature of Nrf2, it became clear that, in addition to shielding normal cells from numerous stresses, Nrf2 may also promote the growth of tumors. In the present review, we performed a systematic analysis of the role of 12 different nutraceuticals like curcumin, sulforaphane, resveratrol, polyunsaturated fatty acids (PUFA) from fish oil, lycopene, soybean, kaempferol, allicin, thymoquinone, quercetin, gingerol, and piperine in modulating the Nrf2/Keap1 signaling mechanism. Among these, 12 Generally Recognized As Safe (GRAS) certified nutraceuticals, sulforaphane is the most extensively studied compound in modulating Keap1-Nrf signaling. Even though there is much evidence at preclinical levels, further high-quality research is still required to validate the potential role of these nutraceuticals in Keap1-Nrf2 modulation.

Deciphering the roles of aryl hydrocarbon receptor (AHR) in regulating carcinogenesis

Aryl hydrocarbon receptor (AHR) is a ligand-dependent receptor that belongs to the superfamily of basic helix-loop-helix (bHLH) transcription factors. The activation of the canonical AHR signaling pathway is known to induce the expression of cytochrome P450 enzymes, facilitating the detoxification metabolism in the human body. Additionally, AHR could interact with various signaling pathways such as epidermal growth factor receptor (EGFR), signal transducer and activator of transcription 3 (STAT3), hypoxia-inducible factor-1α (HIF-1α), nuclear factor ekappa B (NF-κβ), estrogen receptor (ER), and androgen receptor (AR) signaling pathways. Over the past 30 years, several studies have reported that various chemical, physical, or biological agents, such as tobacco, hydrocarbon compounds, industrial and agricultural chemical wastes, drugs, UV, viruses, and other toxins, could affect AHR expression or activity, promoting cancer development. Thus, it is valuable to overview how these factors regulate AHR-mediated carcinogenesis. Current findings have reported that many compounds could act as AHR ligands to drive the expressions of AHR-target genes, such as CYP1A1, CYP1B1, MMPs, and AXL, and other targets that exert a pro-proliferation or anti-apoptotic effect, like XIAP. Furthermore, some other physical and chemical agents, such as UV and 3-methylcholanthrene, could promote AHR signaling activities, increasing the signaling activities of a few oncogenic pathways, such as the phosphatidylinositol 3-kinase/protein kinase B (PI3K/AKT) and mitogen-activated protein kinase/extracellular signal-regulated kinase (MAPK/ERK) pathways. Understanding how various factors regulate AHR-mediated carcinogenesis processes helps clinicians and scientists plan personalized therapeutic strategies to improve anti-cancer treatment efficacy. As many studies that have reported the roles of AHR in regulating carcinogenesis are preclinical or observational clinical studies that did not explore the detailed mechanisms of how different chemical, physical, or biological agents promote AHR-mediated carcinogenesis processes, future studies should focus on conducting large-scale and functional studies to unravel the underlying mechanism of how AHR interacts with different factors in regulating carcinogenesis processes.

Hypoxia inducible factor-1α (HIF-1α) in breast cancer: The crosstalk with oncogenic and onco-suppressor factors in regulation of cancer hallmarks

Low oxygen level at tumor microenvironment leads to a condition, known as hypoxia that is implicated in cancer progression. Upon hypoxia, HIF-1α undergoes activation and due to its oncogenic function and interaction with other molecular pathways, promotes tumor progression. The HIF-1α role in regulating breast cancer progression is described, Overall, HIF-1α has upregulation in breast tumor and due to its tumor-promoting function, its upregulation is in favor of breast tumor progression. HIF-1α overexpression prevents apoptosis in breast tumor and it promotes cell cycle progression. Silencing HIF-1α triggers cycle arrest and decreases growth. Migration of breast tumor enhances by HIF-1α signaling and it mainly induces EMT in providing metastasis. HIF-1α upregulation stimulates drug resistance and radio-resistance in breast tumor. Furthermore, HIF-1α signaling induces immune evasion of breast cancer. Berberine and pharmacological intervention suppress HIF-1α signaling in breast tumor and regulation of HIF-1α by non-coding RNAs occurs. Furthermore, HIF-1α is a biomarker in clinic.

The Role of Nrf2/sMAF Signalling in Retina Ageing and Retinal Diseases

Age-related diseases, such as Parkinson's disease, Alzheimer's disease, cardiovascular diseases, cancers, and age-related macular disease, have become increasingly prominent as the population ages. Oxygen is essential for living organisms, but it may also cause disease when it is transformed into reactive oxygen species via biological processes in cells. Most of the production of ROS occurs in mitochondrial complexes I and III. The accumulation of ROS in cells causes oxidative stress, which plays a crucial role in human ageing and many diseases. Nuclear factor-erythroid 2-related factor 2 (Nrf2) is a key antioxidant transcription factor that plays a central role in many diseases and ageing in general. It regulates many downstream antioxidative enzymes when cells are exposed to oxidative stress. A basic-region leucine zipper (bZIP) transcription factor, MAF, specifically the small MAF subfamily (sMAFs), forms heterodimers with Nrf2, which bind with Maf-recognition elements (MAREs) in response to oxidative stress. The role of this complex in the human retina remains unclear. This review summarises the current knowledge about Nrf2 and its downstream signalling, especially its cofactor-MAF, in ageing and diseases, with a focus on the retina. Since Nrf2 is the master regulator of redox homeostasis in cells, we hypothesise that targeting Nrf2 is a promising therapeutic approach for many age-related diseases.

Activation of Nrf2 pathway as a protective mechanism against oxidative stress-induced diseases: Potential of astaxanthin

Astaxanthin, a red-orange liposoluble carotenoid, has been the centre of considerable attention in recent years for its numerous biological activities, notably its potent antioxidant activity. It is reported that astaxanthin elicits these biological activities via a number of cellular pathways. The Nrf2/Keap1 pathway is a major regulator of the antioxidant defence system of cells; it modulates the expression of a plethora of genes related to redox homeostasis as well as cellular detoxification. The pathway has received lots of attention as a prospective therapeutic target for diseases related to oxidative stress and aging. Several reports have shown that the pathway is inducible by many natural compounds. This present work reviews the Nrf2/Keap1 pathway, its regulation and involvement in diseases, provides a brief overview of naturally occurring compounds as activators of the pathway as well as discusses the effect of astaxanthin on the pathway.

The Multi-Faceted Consequences of NRF2 Activation throughout Carcinogenesis

The oxidative balance of a cell is maintained by the Kelch-like ECH-associated protein 1 (KEAP1)/nuclear factor erythroid 2-related factor 2 (NRF2) pathway. This cytoprotective pathway detoxifies reactive oxygen species and xenobiotics. The role of the KEAP1/NRF2 pathway as pro-tumorigenic or anti-tumorigenic throughout stages of carcinogenesis (including initiation, promotion, progression, and metastasis) is complex. This mini review focuses on key studies describing how the KEAP1/NRF2 pathway affects cancer at different phases. The data compiled suggest that the roles of KEAP1/NRF2 in cancer are highly dependent on context; specifically, the model used (carcinogen-induced vs genetic), the tumor type, and the stage of cancer. Moreover, emerging data suggests that KEAP1/NRF2 is also important for regulating the tumor microenvironment and how its effects are amplified either by epigenetics or in response to co-occurring mutations. Further elucidation of the complexity of this pathway is needed in order to develop novel pharmacological tools and drugs to improve patient outcomes.

Mitigating Effect of Dietary Dioclea reflexa (Hook F) Seed Inclusion in Experimental Colon Carcinogenesis

Rats exposed to 72-hour intrarectal instillations of N-methyl-N-nitrosourea (MNU) were fed with Dioclea reflexa seed-included diets (0, 2.5, 5.0, and 10%). Following sacrifice, organs and blood were collected and analyzed for indices of oxidative stress and carcinogenesis using spectrophotometric, ELISA, histological, and immunohistochemical techniques. Dioclea reflexa seed-included diets significantly ( $p<0.05$ ) prevented MNU-induced elevation of carcinoembryonic antigen (CEA), malondialdehyde, and neutrophil-to-lymphocyte ratio (NLR) and boosted the activities of glutathione s-transferase, superoxide dismutase, and catalase. It also prevented MNU-induced colonic mucosal ulceration/interglandular inflammations and protected the mismatch repair gene, Mutl homolog1, against MNU-induced damage. There was a strong negative relationship between CEA, NLR, and the antioxidant enzyme activities, as well as total polyphenols, total flavonoids, and crude fiber, while CEA correlated positively with malondialdehyde levels. These results suggest that Dioclea reflexa seed is endowed with constituents possessing a potent capacity to mitigate oxidative stress, as well as the initiation and promotion of chemically induced colon carcinogenesis.

The Regulatory Effect of Phytochemicals on Chronic Diseases by Targeting Nrf2-ARE Signaling Pathway

Redox balance is essential to maintain the body's normal metabolism. Once disrupted, it may lead to various chronic diseases, such as diabetes, neurodegenerative diseases, cardiovascular diseases, inflammatory diseases, cancer, aging, etc. Oxidative stress can cause or aggravate a series of pathological processes. Inhibition of oxidative stress and related pathological processes can help to ameliorate these chronic diseases, which have been found to be associated with Nrf2 activation. Nrf2 activation can not only regulate the expression of a series of antioxidant genes that reduce oxidative stress and its damage, but also directly regulate genes related to the above-mentioned pathological processes to counter the corresponding changes. Therefore, targeting Nrf2 has great potential for the prevention or treatment of chronic diseases, and many natural phytochemicals have been reported as Nrf2 activators although the defined mechanisms remain to be elucidated. This review article focuses on the possible mechanism of Nrf2 activation by natural phytochemicals in the prevention or treatment of chronic diseases and the regulation of oxidative stress. Moreover, the current clinical trials of phytochemical-originated drug discovery by targeting the Nrf2-ARE pathway were also summarized; the outcomes or the relationship between phytochemicals and chronic diseases prevention are finally analyzed to propose the future research strategies and prospective.

Contribution of Non-Coding RNAs to Anticancer Effects of Dietary Polyphenols: Chlorogenic Acid, Curcumin, Epigallocatechin-3-Gallate, Genistein, Quercetin and Resveratrol

Growing evidence has been accumulated to show the anticancer effects of daily consumption of polyphenols. These dietary polyphenols include chlorogenic acid, curcumin, epigallocatechin-3-O-gallate, genistein, quercetin, and resveratrol. These polyphenols have similar chemical and biological properties in that they can act as antioxidants and exert the anticancer effects via cell signaling pathways involving their reactive oxygen species (ROS)-scavenging activity. These polyphenols may also act as pro-oxidants under certain conditions, especially at high concentrations. Epigenetic modifications, including dysregulation of noncoding RNAs (ncRNAs) such as microRNAs, long noncoding RNAs, and circular RNAs are now known to be involved in the anticancer effects of polyphenols. These polyphenols can modulate the expression/activity of the component molecules in ROS-scavenger-triggered anticancer pathways (RSTAPs) by increasing the expression of tumor-suppressive ncRNAs and decreasing the expression of oncogenic ncRNAs in general. Multiple ncRNAs are similarly modulated by multiple polyphenols. Many of the targets of ncRNAs affected by these polyphenols are components of RSTAPs. Therefore, ncRNA modulation may enhance the anticancer effects of polyphenols via RSTAPs in an additive or synergistic manner, although other mechanisms may be operating as well.

Nrf2 and Oxidative Stress: A General Overview of Mechanisms and Implications in Human Disease

Organisms are continually exposed to exogenous and endogenous sources of reactive oxygen species (ROS) and other oxidants that have both beneficial and deleterious effects on the cell. ROS have important roles in a wide range of physiological processes; however, high ROS levels are associated with oxidative stress and disease progression. Oxidative stress has been implicated in nearly all major human diseases, from neurogenerative diseases and neuropsychiatric disorders to cardiovascular disease, diabetes, and cancer. Antioxidant defence systems have evolved as a means of protection against oxidative stress, with the transcription factor Nrf2 as the key regulator. Nrf2 is responsible for regulating an extensive panel of antioxidant enzymes involved in the detoxification and elimination of oxidative stress and has been extensively studied in the disease contexts. This review aims to provide the reader with a general overview of oxidative stress and Nrf2, including basic mechanisms of Nrf2 activation and regulation, and implications in various major human diseases.