Carbonyl reductase 1 as a novel target of (-)-epigallocatechin gallate against hepatocellular carcinoma

The efficacy of polyphenols as an antioxidant agent: An updated review

Global production of the two major poultry products, meat and eggs, has increased quickly. This, in turn, indicates both the relatively low cost and the customers' desire for these secure and high-quality products. Natural feed additives have become increasingly popular to preserve and enhance the health and productivity of poultry and livestock. We consume a lot of polyphenols, which are a kind of micronutrient. These are phytochemicals with positive effects on cardiovascular, cognitive, anti-inflammatory, detoxifying, anti-tumor, anti-pathogen, a catalyst for growth, and immunomodulating functions, among extra health advantages. Furthermore, high quantities of polyphenols have unknown and occasionally unfavorable impacts on the digestive tract health, nutrient assimilation, the activity of digestive enzymes, vitamin and mineral assimilation, the performance of the laying hens, and the quality of the eggs. This review clarifies the numerous sources, categories, biological functions, potential limitations on usage, and effects of polyphenols on poultry performance, egg composition, exterior and interior quality traits.

The potential of epigallocatechin gallate in the chemoprevention and therapy of hepatocellular carcinoma

Hepatocellular carcinoma (HCC), one of the most notorious malignancies globally, has a high fatality and poor prognosis. Though remarkable breakthroughs have been made in the therapeutic strategies recently, the overall survival of HCC remains unsatisfactory. Consequently, the therapy of HCC remains a great challenge. Epigallocatechin gallate (EGCG), a natural polyphenol extracted from the leaves of the tea bush, has been extensively investigated for its antitumor effects. In this review, we summarize the previous literature to elucidate the roles of EGCG in the chemoprophylaxis and therapy of HCC. Accumulating evidence has confirmed EGCG prevents and inhibits the hepatic tumorigenesis and progression through multiple biological mechanisms, mainly involving hepatitis virus infection, oxidative stress, proliferation, invasion, migration, angiogenesis, apoptosis, autophagy, and tumor metabolism. Furthermore, EGCG enhances the efficacy and sensitivity of chemotherapy, radiotherapy, and targeted therapy in HCC. In conclusion, preclinical studies have confirmed the potential of EGCG for chemoprevention and therapy of HCC under multifarious experimental models and conditions. Nevertheless, there is an urgent need to explore the safety and efficacy of EGCG in the clinical practice of HCC.

EGCG adjuvant chemotherapy: Current status and future perspectives

The resistance of cancer cells to chemotherapeutic drugs greatly reduces the therapeutic effect in cancer patients, and the toxic side effects caused by chemotherapy also seriously affect the quality of life of patients. The combination of epigallocatechin-3-gallate (EGCG), the main active ingredient in tea, with cisplatin, 5-FU, doxorubicin and paclitaxel enhances their sensitizing effect on tumors and combats the drug resistance of cancer cells. These effects seem to be mediated by a variety of mechanisms, including combating drug resistance mediated by cancer stem cells, enhancing drug sensitivity, inducing cell cycle arrest and apoptosis, and blocking angiogenesis. In addition, EGCG can suppress a series of adverse effects caused by chemotherapy, such as gastrointestinal disorders, nephrotoxicity and cardiotoxicity, through its anti-inflammatory and antioxidant effects and improve the quality of life of patients. However, the low bioavailability and off-target effects of EGCG and its reactivity with some chemotherapeutic agents limit its clinical application. The nanomodification of EGCG and chemotherapeutic drugs not only enhances the antitumor activity but also prolongs the survival time of tumor-bearing mice, and has the advantage of low toxicity. Therefore, this review aims to discuss the current status and challenges regarding the use of EGCG in combination with chemotherapy drugs in the treatment of cancer. In general, EGCG is a promising adjuvant for chemotherapy.

Development of transgenic mice overexpressing mouse carbonyl reductase 1

BACKGROUND

Carbonyl reductase 1 (CBR1) is a nicotinamide adenine dinucleotide phosphate (NADPH)-dependent reductase with broad substrate specificity. CBR1 catalyzes the reduction of numerous carbonyl compounds, including quinones, prostaglandins, menadione, and multiple xenobiotics, while also participating in various cellular processes, such as carcinogenesis, apoptosis, signal transduction, and drug resistance. In this study, we aimed to generate transgenic mice overexpressing mouse Cbr1 (mCbr1), characterize the mCbr1 expression in different organs, and identify changes in protein expression patterns.

METHODS AND RESULTS

To facilitate a deeper understanding of the functions of CBR1, we generated transgenic mice overexpressing CBR1 throughout the body. These transgenic mice overexpress 3xFLAG-tagged mCbr1 (3xFLAG-mCbr1) under the CAG promoter. Two lines of transgenic mice were generated, one with 3xFLAG-mCbr1 expression in multiple tissues, and the other, with specific expression of 3xFLAG-mCbr1 in the heart. Pathway and network analysis using transgenic mouse hearts identified 73 proteins with levels of expression correlating with mCbr1 overexpression. The expression of voltage-gated anion channels, which may be directly related to calcium ion-related myocardial contraction, was also upregulated.

CONCLUSION

mCbr1 transgenic mice may be useful for further in vivo analyses of the molecular mechanisms regulated by Cbr1; such analyses will provide a better understanding of its effects on carcinogenesis and cardiotoxicity of certain cancer drugs.

Anticarcinogenic potentials of tea catechins

Catechins are a cluster of polyphenolic bioactive components in green tea. Anticarcinogenic effects of tea catechins have been reported since the 1980s, but it has been controversial. The present paper reviews the advances in studies on the anticarcinogenic activities of tea and catechins, including epidemiological evidence and anticarcinogenic mechanism. Tea catechins showed antagonistic effects on many cancers, such as gynecological cancers, digestive tract cancers, incident glioma, liver and gallbladder cancers, lung cancer, etc. The mechanism underlying the anticarcinogenic effects of catechins involves in inhibiting the proliferation and growth of cancer cells, scavenging free radicals, suppressing metastasis of cancer cells, improving immunity, interacting with other anticancer drugs, and regulating signaling pathways. The inconsistent results and their causes are also discussed in this paper.

Impacts of polyphenols on laying hens' productivity and egg quality: A review

There has been a rapid increase in the world's output of main poultry products (meat and eggs). This reflects customer desire for these high-quality and safe products and the comparatively low price. Recently, natural feed additives, plants and products have been increasingly popular in the poultry and livestock industries to maintain and improve their health and production. Polyphenols are a type of micronutrient that is plentiful in our diet. They are phytochemicals that have health benefits, notably cardiovascular, cognitive function, antioxidant, anti-mutagenic, anti-inflammatory, antistress, anti-tumour, anti-pathogen, detoxification, growth-promoting and immunomodulating activities. On the other hand, excessive polyphenol levels have an unclear and sometimes negative impact on gastrointestinal tract health, nutrient digestion, digestive enzyme activity, vitamin, mineral absorption, laying hens performance and egg quality. As a result, this review illuminated polyphenols' various sources, classifications, biological activities, potential usage restrictions and effects on poultry, layer productivity and egg external and internal quality.

Chrysin induces autophagy-dependent ferroptosis to increase chemosensitivity to gemcitabine by targeting CBR1 in pancreatic cancer cells

Recent studies have verified that inducing reactive oxygen species (ROS) is one of the gemcitabine anti-tumor mechanisms of action. Human carbonyl reductase 1 (CBR1) plays an important role in protecting cells against oxidative damage. However, it is unclear whether CBR1 is involved in pancreatic cancer (PC) progression and resistance to gemcitabine. Based on the GEPIA database, we analyzed tumor tissue samples from PC patients using immunohistochemistry (IHC) and revealed that CBR1 was highly expressed in PC tissues and that this was significantly correlated with the clinicopathological features of PC. Genetic inhibition of CBR1 suppressed PC cell proliferation by regulating ROS generation. Furthermore, gemcitabine upregulated CBR1 expression, which could limit the anti-tumor activity of gemcitabine, and attenuation of CBR1 enhanced gemcitabine sensitivity in vitro and in vivo. Additionally, we report that chrysin directly binds to CBR1, which inhibited its enzymatic activity both at the molecular and cellular levels. Inhibition of CBR1 by chrysin increased cellular ROS levels and led to ROS-dependent autophagy, which resulted in the degradation of ferritin heavy polypeptide 1 (FTH1) and an increase in the intracellular free iron level that participates in ferroptosis in PC cells. Finally, our results showed that chrysin enhanced PC sensitivity to gemcitabine by inducing ferroptotic death in vitro and in vivo. Collectively, these findings indicate that CBR1 is a potential therapeutic target for PC treatment. In addition, we elucidated a novel mechanism underlying the anti-tumor effects of chrysin.

Interactions of the antioxidant enzymes NAD(P)H: Quinone oxidoreductase 1 (NQO1) and NRH: Quinone oxidoreductase 2 (NQO2) with pharmacological agents, endogenous biochemicals and environmental contaminants

NAD(P)H

Quinone Oxidoreductase 1 (NQO1) is an antioxidant enzyme that catalyzes the two-electron reduction of several different classes of quinone-like compounds (quinones, quinone imines, nitroaromatics, and azo dyes). One-electron reduction of quinone or quinone-like metabolites is considered to generate semiquinones to initiate redox cycling that is responsible for the generation of reactive oxygen species and oxidative stress and may contribute to the initiation of adverse drug reactions and adverse health effects. On the other hand, the two-electron reduction of quinoid compounds appears important for drug activation (bioreductive activation) via chemical rearrangement or autoxidation. Two-electron reduction decreases quinone levels and opportunities for the generation of reactive species that can deplete intracellular thiol pools. Also, studies have shown that induction or depletion (knockout) of NQO1 were associated with decreased or increased susceptibilities to oxidative stress, respectively. Moreover, another member of the quinone reductase family, NRH: Quinone Oxidoreductase 2 (NQO2), has a significant functional and structural similarity with NQO1. The activity of both antioxidant enzymes, NQO1 and NQO2, becomes critically important when other detoxification pathways are exhausted. Therefore, this article summarizes the interactions of NQO1 and NQO2 with different pharmacological agents, endogenous biochemicals, and environmental contaminants that would be useful in the development of therapeutic approaches to reduce the adverse drug reactions as well as protection against quinone-induced oxidative damage. Also, future directions and areas of further study for NQO1 and NQO2 are discussed.

Carbonyl reductase 1 amplifies glucocorticoid action in adipose tissue and impairs glucose tolerance in lean mice

OBJECTIVE

Carbonyl reductase 1 (Cbr1), a recently discovered contributor to tissue glucocorticoid metabolism converting corticosterone to 20β-dihydrocorticosterone (20β-DHB), is upregulated in adipose tissue of obese humans and mice and may contribute to cardiometabolic complications of obesity. This study tested the hypothesis that Cbr1-mediated glucocorticoid metabolism influences glucocorticoid and mineralocorticoid receptor activation in adipose tissue and impacts glucose homeostasis in lean and obese states.

METHODS

The actions of 20β-DHB on corticosteroid receptors in adipose tissue were investigated first using a combination of in silico, in vitro, and transcriptomic techniques and then in vivo administration in combination with receptor antagonists. Mice lacking one Cbr1 allele and mice overexpressing Cbr1 in their adipose tissue underwent metabolic phenotyping before and after induction of obesity with high-fat feeding.

RESULTS

20β-DHB activated both the glucocorticoid and mineralocorticoid receptor in adipose tissue and systemic administration to wild-type mice induced glucose intolerance, an effect that was ameliorated by both glucocorticoid and mineralocorticoid receptor antagonism. Cbr1 haploinsufficient lean male mice had lower fasting glucose and improved glucose tolerance compared with littermate controls, a difference that was abolished by administration of 20β-DHB and absent in female mice with higher baseline adipose 20β-DHB concentrations than male mice. Conversely, overexpression of Cbr1 in adipose tissue resulted in worsened glucose tolerance and higher fasting glucose in lean male and female mice. However, neither Cbr1 haploinsfficiency nor adipose overexpression affected glucose dyshomeostasis induced by high-fat feeding.

CONCLUSIONS

Carbonyl reductase 1 is a novel regulator of glucocorticoid and mineralocorticoid receptor activation in adipose tissue that influences glucose homeostasis in lean mice.

Metal-phenolic networks for cancer theranostics

Metal-phenolic networks (MPNs) have shown promising potential in biomedical applications since they provide a rapid, simple and robust way to construct multifunctional nanoplatforms. As a novel nanomaterial self-assembled from metal ions and polyphenols, MPNs can be prepared to assist the theranostics of cancer owing to their bio-adhesiveness, good biocompatibility, versatile drug loading, and stimuli-responsive profile. This Critical Review aims to summarize recent progress in MPN-based nanoplatforms for multimodal tumor therapy and imaging. First, the advantages of MPNs as drug carriers are summarized. Then, various tumor therapeutic modalities based on MPNs are introduced. Next, MPN-based theranostic systems are reviewed. In terms of in vivo applications, specific attention is paid to their biosafety, biodistribution, as well as excretion. Finally, some problems and limitations of MPNs are discussed, along with a future perspective on the field.

Carbonyl reduction pathway in hepatic in vitro metabolism of anthracyclines: Impact of structure on biotransformation rate

Carbonyl reduction biotransformation pathway of anthracyclines (doxorubicin, daunorubicin) is a significant process, associated with drug metabolism and elimination. However, it also plays a pivotal role in anthracyclines-induced cardiotoxicity and cancer resistance. Herein, carbonyl reduction of eight anthracyclines, at in vivo relevant concentrations (20 μM), was studied in human liver cytosol, to describe the relationship between their structure and metabolism. Significant differences of intrinsic clearance between anthracyclines, ranging from 0,62-74,9 μL/min/mg were found and associated with data from in silico analyses, considering their binding in active sites of the main anthracyclines-reducing enzymes: carbonyl reductase 1 (CBR1) and aldo-keto reductase 1C3 (AKR1C3). Partial atomic charges of carbonyl oxygen atom were also determined and considered as a factor associated with reaction rate. Structural features, including presence or absence of side-chain hydroxy group, a configuration of sugar chain hydroxy group, and tetracyclic rings substitution, affecting anthracyclines susceptibility for carbonyl reduction were identified.

The epigallocatechin gallate derivative Y6 reduces the cardiotoxicity and enhances the efficacy of daunorubicin against human hepatocellular carcinoma by inhibiting carbonyl reductase 1 expression

ETHNOPHARMACOLOGICAL RELEVANCE

Green tea is the most ancient and popular beverage worldwide and its main constituent epigallocatechin-3-gallate (EGCG) has a potential role in the management of cancer through the modulation of cell signaling pathways. However, EGCG is frangible to oxidation and exhibits low lipid solubility and bioavailability, and we synthesized a derivative of EGCG in an attempt to overcome these limitations.

AIM OF THE STUDY

The anthracycline antibiotic daunorubicin (DNR) is a potent anticancer agent. However, its severe cardiotoxic limits its clinical efficacy. Human carbonyl reductase 1 (CBR1) is one of the most effective human reductases for producing hydroxyl metabolites and thus may be involved in increasing the cardiotoxicity and decreasing the antineoplastic effect of anthracycline antibiotics. Accordingly, in this study, we investigated the co-therapeutic effect of Y6, a novel and potent adjuvant obtained by optimization of the structure of EGCG.

MATERIAL AND METHODS

The cellular concentrations of DNR and its metabolite DNRol were measured by HPLC to determine the effects of EGCG and Y6 on the inhibition of DNRol formation. The cytotoxic effects of EGCG and Y6 were tested by MTT assay in order to identify non-toxic concentrations of them. To understand their antitumor and cardioprotective mechanisms, hypoxia-inducible factor-1α (HIF-1α) and CBR1 protein expression was measured via Western blotting and immunohistochemical staining while gene expression was analyzed using RT-PCR. Moreover, PI3K/AKT and MEK/ERK signaling pathways were analyzed via Western blotting. HepG2 xenograft model was used to detect the effects of EGCG and Y6 on the antitumor activity and cardiotoxicity of DNR in vivo. Finally, to obtain further insight into the interactions of Y6 and EGCG with HIF-1α and CBR1, we performed a molecular modeling.

RESULTS

Y6(10 μg/ml or 55 mg/kg) decreased the expression of HIF-1α and CBR1 at both the mRNA and protein levels during combined drug therapy in vitro as well as in vivo, thereby inhibiting formation of the metabolite DNRol from DNR, with the mechanisms being related to PI3K/AKT and MEK/ERK signaling inhibition. In a human carcinoma xenograft model established with subcutaneous HepG2 cells, Y6(55 mg/kg) enhanced the antitumor effect and reduced the cardiotoxicity of DNR more effectively than EGCG(40 mg/kg).

CONCLUSIONS

Y6 has the ability to inhibit CBR1 expression through the coordinate inhibition of PI3K/AKT and MEK/ERK signaling, then synergistically enhances the antitumor effect and reduces the cardiotoxicity of DNR.

Identification and Analysis of the Tegument Protein and Excretory-Secretory Products of the Carcinogenic Liver Fluke Clonorchis sinensis

Liver fluke proteins, including excretory-secretory products (ESPs) and tegument proteins, are critical for the pathogenesis, nutrient metabolism, etiology and immune response of liver cancer. To understand the functions of various proteins in Clonorchis sinensis physiology and human clonorchiasis, the ESPs and tegument proteins of C. sinensis were identified. Supernatants containing ESPs from adult C. sinensis after culture for 6 h were harvested and concentrated. The tegument was detached using a freeze/thaw method and successively extracted using various extraction buffers. The outer surface proteins of C. sinensis were labeled with biotin, and the biotinylated proteins were purified. The ESP, tegument and labeled outer surface proteins were identified and analyzed by high-resolution LC-MS/MS. The identified proteins were compared with those of other flukes, and the protein functions associated with pathogenesis, carcinogenesis and potential vaccine antigens and drug targets were predicted and analyzed. A total of 175 proteins were identified after the 6-h culture of C. sinensis ESPs. A total of 352 tegument proteins were identified through sequential solubilization of the isolated teguments, and a subset of these proteins were localized to the surface membrane of the tegument by labeling with biotin. Thirty identified proteins, including annexins, actin and tetraspanins, were identified as potential immunomodulators and promising vaccine antigens. Interestingly, among the 352 tegument proteins, as many as 155 were enzymes, and most were oxidoreductases, hydrolases or transferases. A comparison of the outer surface proteins of C. sinensis with those of other flukes indicated that flukes have some common outer surface proteins, such as actin, tetraspanin, glyceraldehyde-3-phosphate dehydrogenase (GAPDH) and annexin. Granulin, thioredoxin peroxiredoxin, carbonyl reductase 1 and cystatin were identified in the C. sinensis proteome and predicted to be related to liver disease and cancer. The analysis of the C. sinensis proteome could contribute to a more in-depth understanding of complex parasite-host relationships, improve the diagnosis of clonorchiasis and benefit research on the pathogenesis and development of novel interventions, drugs and vaccines to control C. sinensis infection.

Impairment of spatial memory accuracy improved by Cbr1 copy number resumption and GABAB receptor-dependent enhancement of synaptic inhibition in Down syndrome model mice

Down syndrome is a complex genetic disorder caused by the presence of three copies of the chromosome 21 in humans. The most common models, carrying extra-copies of overlapping fragments of mouse chromosome 16 that is syntenic to human chromosome 21, are Ts2Cje, Ts1Cje and Ts1Rhr mice. In electrophysiological analyses using hippocampal slices, we found that the later phase of the depolarization during tetanic stimulation, which was regulated by GABA_B receptors, was significantly smaller in Ts1Cje and Ts2Cje mice than that in WT controls but not in Ts1Rhr mice. Furthermore, isolated GABA_B receptor-mediated inhibitory synaptic responses were larger in Ts1Cje mice. To our knowledge, this is the first report that directly shows the enhancement of GABA_B receptor-mediated synaptic currents in Ts1Cje mice. These results suggest that GABA_B receptor-mediated synaptic inhibition was enhanced in Ts1Cje and Ts2Cje mice but not in Ts1Rhr mice. The Cbr1 gene, which is present in three copies in Ts1Cje and Ts2Cje but not in Ts1Rhr, encodes carbonyl reductase that may facilitate GABA_B-receptor activity through a reduction of prostaglandin E2 (PGE2). Interestingly, we found that a reduction of PGE2 and an memory impairment in Ts1Cje mice were alleviated when only Cbr1 was set back to two copies (Ts1Cje;Cbr1^+/+/-). However, the GABA_B receptor-dependent enhancement of synaptic inhibition in Ts1Cje was unaltered in Ts1Cje;Cbr1^+/+/- mice. These results indicate that Cbr1 is one of the genes responsible for DS cognitive impairments and the gene(s) other than Cbr1, which is included in Ts1Cje but not in Ts1Rhr, is responsible for the GABA_B receptor-dependent over-inhibition.

Cinnamic acid derivatives as chemosensitising agents against DOX-treated lung cancer cells - Involvement of carbonyl reductase 1

Doxorubicin (DOX) therapy is limited by both cancer cells resistance and cardiotoxicity. DOX biotransformation to doxorubicinol (DOXol) by reductases enzymes (mainly by CBR1; carbonyl reductase 1) is a key process responsible for DOX adverse effects development. Thus, inhibition of CBR1 can increase the therapeutic effect of DOX. In the present study, we used a group of new synthetized cinnamic acid (CA) derivatives to improve the effectiveness and safety profile of DOX therapy against cancer cells in vitro. The possible mechanism of CBR1 inhibition was simulated by molecular modelling studies. The kinetics of DOX reduction in the presence of active CA derivatives were measured in cytosols. The chemosensitising activity of CA derivatives including proapoptotic, anti-invasiveness activity were investigated in A549 lung cancer cell line. In our research 7 from 16 tested CA derivatives binded to the active site of CBR1 enzyme and improved DOX stability by inhibition of DOXol formation. Co-treatment of A549 cells with active CA derivatives and DOX induced cells apoptosis by activation of caspase cascade. At the same time we observed decrease of invasive properties (cell migration and transmigration assays) and the rearangments of F-actin cytoskeleton in CA derivatves + DOX treated cells. Meanwhile, control, human lung fibroblasts stay realtivelly unvulnerable and viable. New synthetized CA derivatives may inhibit the activity of CBR1 leading to the stabilization of DOX therapeutic levels in cancer cells and to protect the myocardium against DOXol cytotoxic effect. Favourable physicochemical properties supported by a safety profile and multidirectional chemosensitising activity render CA derivatives a promising group for the development of agent useful in combined therapy.

Self-assembled green tea polyphenol-based coordination nanomaterials to improve chemotherapy efficacy by inhibition of carbonyl reductase 1

Nanomedicine has become a promising approach to improve cancer chemotherapy. It remains a major challenge how to enhance anti-drug efficacy and reduce side effects of anti-cancer drugs. Herein, we report a self-assembled nanoplatform (FDEP NPs) by integration of doxorubicin (DOX) and epigallocatechin-3-O-gallate (EGCG) with the help of coordination between Fe3+ ions and polyphenols. The EGCG from FDEP NPs could inhibit the expression of carbonyl reductase 1 (CBR1) protein and thereby inhibit the doxorubicinol (DOXOL) generation from DOX both in vitro and in vivo, thus the efficacy of DOX to cancerous cells is improved significantly. More importantly, the FDEP NPs could reduce cardiac toxicity and the DOX mediated toxicity to blood cells due to the repression of DOXOL production. Moreover, the blood half-life of FDEP NPs is longer than 23 h as determined by positron emission tomography (PET) imaging of biodistribution of radiolabelled NPs and HPLC measurement of plasma level of DOX, ensuring high tumor accumulation of FDEP NPs by enhanced permeability and retention (EPR) effect. The FDEP NPs also exhibited much improved antitumor effect over free drugs. Our work sheds new light on the engineering of nanomaterials for combination chemotherapy and may find unique clinical applications in the near future.

Synergistic anticancer activity of doxorubicin and piperlongumine on DU-145 prostate cancer cells - The involvement of carbonyl reductase 1 inhibition

One of the causes of therapeutic failure of chemotherapy is cancer cell resistance. In the case of anthracyclines, many resistance mechanisms have been described. One of them assumes the role of carbonyl reductase 1 (CBR1), a cytosolic enzyme that is responsible for the biotransformation process of anthracyclines to less active, undesirable metabolites. Therefore, CBR1 inhibitors are considered for use as a chemosensitizing agents. In the present study, piperlongumine (PL), a Piper longum L. alkaloid that has previously been described as a CBR1 inhibitor, was investigated for its chemosensitizing properties in co-treatment with doxorubicin (DOX). The biotransformation process of DOX in the presence of PL was tracked using human cytosol fraction and LC-MS, then a molecular modeling study was conducted to predict the interaction of PL with the active site of the CBR1. The biological interaction between DOX and PL was investigated using DU-145 prostate cancer cells. Cytotoxic and antiproliferative properties of DOX and PL were examined, and the type and potency of interaction was quantified by Combination Index. The mechanism of the cell death induced by the agents was investigated by flow cytometry and the anti-invasive properties of the drugs were determined by monitoring the movement of individual cells. PL showed dose-dependent inhibition of DOX metabolism in cytosol, which resulted in less doxorubicinol (DOXol) metabolite being formed. The possible mechanism of CBR1 inhibition was explained through molecular modeling studies by prediction of PL's binding mode in the active site of the enzyme's crystal structure-based model. DOX and PL showed a synergistic antiproliferative and proapoptotic effect on cancer cells. Significant anti-invasive properties of the combination of DOX and PL were found, but when the drugs were used separately they did not alter the cancer cells' motility. Cell motility inhibition was accompanied by significant changes in cytoskeleton architecture. DOX and PL used in co-treatment showed significant synergistic anticancer properties. Inhibition of DOX metabolism by PL was found to be a mechanism that was likely to be responsible for the observed interaction.

Epigallocatechin-3-gallate in the prevention and treatment of hepatocellular carcinoma: experimental findings and translational perspectives

Hepatocellular carcinoma (HCC), a primary liver malignancy, is one of the deadliest cancers worldwide. Despite orthotopic liver transplantation and hepatic resection representing the principal lines of treatment for this pathology, only a minority of patients can be resected owing to cirrhosis or late diagnosis. Keeping in mind the end goal of conquering these challenges, new alternative approaches have been proposed. Accumulating evidence has demonstrated that epigallocatechin-3-gallate (EGCG), the principal catechin of green tea with multiple biological properties, is able to modulate different molecular mechanisms underlying HCC, mainly through its antioxidant activity. In this article, we revise these findings reported in the literature, in order to highlight the potential roles of EGCG in the treatment of HCC. The CAMARADES criteria were applied for quality assessment of animal studies, and a narrative synthesis performed. New bits of information available for translational perspectives into clinical practice are addressed.

A Review of Resveratrol as a Potent Chemoprotective and Synergistic Agent in Cancer Chemotherapy

Background: Cancer has become a major disease endangering human health around the world. Conventional chemotherapy suffers from many side effects including pain, cardiotoxicity, hepatotoxicity, and renal toxicity. This review aims to describe a natural product of resveratrol as a chemoprotective and synergistic agent in the modulation of cancer chemotherapy.

Methods: The publications were identified by comprehensive searching of SciFinder, PubMed, Web of Science, and our own reference library. Search terms included combinations of “resveratrol,” “cancer,” “natural products,” “chemotherapy,” and “side effects.” Selection of material focused on resveratrol reducing the side effects on cancer chemotherapy.

Results: Thirty one references were referred in this review to outline resveratrol as a potent chemoprotective and synergistic agent in cancer chemotherapy, including 22 papers for describing the chemoprotective effects, and 9 papers for illustrating the synergistic effects.

Conclusion: This study provides a systematic summary of resveratrol serving as a potent chemoprotective and synergistic agent to reduce the associated-side effects and enhance the therapeutic outcomes in cancer chemotherapy. Further studies in terms of resveratrol on a large amount of preclinical tests and clinical trials are highly demanded.

Carbonyl reductase 1 is a new target to improve the effect of radiotherapy on head and neck squamous cell carcinoma

Background

Human carbonyl reductase 1 (CBR1) plays major roles in protecting cells against cellular damage resulting from oxidative stress. Although CBR1-mediated detoxification of oxidative materials increased by stressful conditions including hypoxia, neuronal degenerative disorders, and other circumstances generating reactive oxide is well documented, the role of CBR1 under ionising radiation (IR) is still unclear.

Methods

The formalin-fixed and paraffin-embedded tissues of 85 patients with head and neck squamous cell carcinoma (HNSCC) were used to determine if CBR1 expression effects on survival of patients with treatment of radiotherapy. Subsequently colony formation assays and xenograft tumor mouse model was used to verify the relationship between CBR1 expression and radiosensitivity in HNSCC cells. Publicly-available data from The Cancer Genome Atlas (TCGA) was analysed to determine if CBR1 expression affects the survival of patients with HNSCC. To verify CBR1-mediated molecular signalling pathways, cell survival, DNA damage/repair, reactive oxygen species (ROS), cell cycle distribution and mitotic catastrophe in HNSCC cells with modulated CBR1 expression by knockdown or overexpression were measured using by colony formation assays, flow cytometry, qRT-PCR and western blot analysis.

Results

HNSCC patients with low CBR1 had a significantly higher survival rate than the high CBR1 expression (84.2% vs. 57.8%, p = 0.0167). Furthermore, HNSCC patients with low CBR1 expression showed a good prognosis for IR compared to patients with highly expressed CBR1. Also, we found that IR upregulated CBR1 mRNA via Nrf2 activation in HNSCC cells and patients. In vitro analysis, we found that CBR1-specific siRNA or inhibitor significantly enhanced radiosensitivity after IR, while CBR1 overexpression decreased. CBR1 inhibition by siRNA or inhibitor treatment accumulated cellular ROS leading to aberrant DNA damage repair and an increase of mitotic catastrophe. Moreover, the combination of CBR1 depletion with IR dramatically inhibited primary tumour growth in a xenograft tumor mouse model.

Conclusion

Our findings indicate that CBR1 has a key role in DNA damage response through regulation of IR-mediated ROS generation. Consistently, CBR1 expression is highly correlated with patient survival after and susceptibility to radiation therapy. Therefore, CBR1 inhibition with IR might be a potent therapeutic strategy for HNSCC treatment.

Electronic supplementary material

The online version of this article (10.1186/s13046-018-0942-9) contains supplementary material, which is available to authorized users.

Flavonoids Effects on Hepatocellular Carcinoma in Murine Models: A Systematic Review

The hepatocellular carcinoma (HCC) is the second most common cause of cancer deaths worldwide. It occurs primarily as manifestation of other pathological processes, such as viral hepatitis, cirrhosis, and toxin exposure that affect directly the cellular process. Studies were selected from PubMed and Scopus databases according to the PRISMA statement. The research filters were constructed using three parameters: flavonoids, hepatocellular carcinoma, and animal model. The bias analysis of the 34 selected works was done using the ARRIVE guidelines. The most widely used flavonoid in the studies was epigallocatechin gallate extracted from green tea. In general, the treatment with different flavonoids presented inhibition of tumor growth and antiangiogenic, antimetastatic, antioxidant, and anti-inflammatory activities. The bias analysis evidenced the absence of methodological processes in all studies, such as the age or weight of the animals, the method of flavonoids' extraction, or the experimental designs, analytical methods, and outcome measures. It has been known that flavonoids have a protective effect against HCC. However, the absence or incomplete characterization of the animal models, treatment protocols, and phytochemical and toxicity analyses impaired the internal validity of the individual studies, making it difficult to determine the effectiveness of plant-derived products in the treatment of HCC.

The effect of deprenyl and isatin administration to mice on the proteomic profile of liver isatin-binding proteins

Isatin (indol-2,3-dione) is an endogenous indole found in the brain, peripheral tissues and biological body fluids of humans and animals. Its wide spectrum of biological activity is realized via interaction with numerous isatin-binding proteins; these include proteins playing an important role in the development of neurodegenerative pathology. In the context of the neuroprotective effect, the effect of isatin is comparable to the effects of deprenyl, a pharmacological agent used for treatment of Parkinson's disease. In this study, the effects of the course of deprenyl (1 mg/kg) and isatin (20 mg/kg) administration for 21 days on the profile of the isatin-binding proteins of the liver of mice have been investigated. Proteomic profiling of liver isatin-binding proteins of control mice by means of 5-aminocaproylisatin as an affinity ligand resulted in identification of 105 proteins. Treatment of animals with a low dose of isatin slightly decreased (up to 91), while injections of deprenyl slightly increased (up to 120) the total number of isatin-binding proteins. 75 proteins were common for all three groups; they represented from 62.5% (in deprenyl treated mice) and 71% (in control mice), to 82% (isatin treated mice) of the total number of identified liver isatin-binding proteins. Proteomic analysis of the isatin-binding proteins of mice treated with isatin (20 mg/kg) or deprenyl (1 mg/kg) for 21 days revealed a representative group of proteins (n=30) that were sensitive to the administration of these substances. Taking into account the previously obtained results, it is reasonable to suggest that the change in the profile of isatin-binding proteins may be attributed to accumulation of isatin and deprenyl in the liver and interaction with target proteins prevents their subsequent binding to the affinity sorbent. In this context, the identified isatin-binding liver proteins of control animals that do not bind to the affinity sorbent (immobilized isatin analogue) after treatment of animals with either deprenyl or isatin appear to be specific targets directly interacting with isatin in vivo.

Association between CBR1 polymorphisms and NSCLC in the Chinese population

Carbonyl reductase 1 (CBR1) is theorized to participate in various cellular processes, such as signal transduction, apoptosis, carcinogenesis and drug resistance, and is highly expressed in certain malignancies, including lung tumors. Several studies have provided evidence that gene polymorphisms may affect susceptibility to non-small cell lung cancer (NSCLC). The present study aimed to investigate the association between the CBR1 single-nucleotide polymorphisms (SNPs) rs3787728 and rs2835267, and NSCLC in a Chinese population. The data indicated that the allele frequency in CBR1 rs3787728 was significantly different between patients with NSCLC and the controls [odds ratio (OR)=1.209; 95% confidence interval (CI)=1.013-1.442; P=0.0349], and was significantly different between male patients with NSCLC and the corresponding controls (OR=1.278; 95% CI=1.016-1.607; P=0.0358). The CBR1 rs3787728 thymine (T)/T allele homozygote was associated with an increased risk of NSCLC in all patients (OR=1.382; 95% CI=1.019-1.875; P=0.037), and patients possessing the rs3787728 T/T major allele homozygote exhibited a 1.537-fold greater risk with respect to developing lung squamous-cell carcinoma (SCC) in all patients (95% CI=1.019-2.318; P=0.0395). The CBR1 rs3787728 cytosine (C)/C allele homozygote was associated with a decreased risk of adenocarcinoma (ADC) in male patients (OR=0.633; 95% CI=0.413-0.969; P=0.0348); however, no significant association was observed in CBR1 rs2835267 between SNPs and SCC or ADC-type NSCLC. In conclusion, the results revealed that genetic polymorphisms of CBR1 rs3787728 were associated with susceptibility to NSCLC. Additional studies are required to identify the functional impact of CBR1 expression and activity in NSCLC.

Epigallocatechin-3-gallate enhances ER stress-induced cancer cell apoptosis by directly targeting PARP16 activity

Poly(ADP-ribose) polymerases (PARPs) are ADP-ribosylating enzymes and play important roles in a variety of cellular processes. Most small-molecule PARP inhibitors developed to date have been against PARP1, a poly-ADP-ribose transferase, and suffer from poor selectivity. PARP16, a mono-ADP-ribose transferase, has recently emerged as a potential therapeutic target, but its inhibitor development has trailed behind. Here we newly characterized epigallocatechin-3-gallate (EGCG) as a potential inhibitor of PARP16. We found that EGCG was associated with PARP16 and dramatically inhibited its activity in vitro. Moreover, EGCG suppressed the ER stress-induced phosphorylation of PERK and the transcription of unfolded protein response-related genes, leading to dramatically increase of cancer cells apoptosis under ER stress conditions, which was dependent on PARP16. These findings newly characterized EGCG as a potential inhibitor of PARP16, which can enhance the ER stress-induced cancer cell apoptosis, suggesting that a combination of EGCG and ER stress-induced agents might represent a novel approach for cancer therapy or chemoprevention.

Structure and characterization of a NAD(P)H-dependent carbonyl reductase from Pseudomonas aeruginosa PAO1

To investigate the function of the pa4079 gene from the opportunistic pathogen Pseudomonas aeruginosa PAO1, we determined its crystal structure and confirmed it to be a NAD(P)-dependent short-chain dehydrogenase/reductase. Structural similarity and activity for a broad range of substrates indicate that PA4079 functions as a carbonyl reductase. Comparison of apo- and holo-PA4079 shows that NADP stabilizes the active site specificity loop, and small molecule binding induces rotation of the Tyr183 side chain by approximately 90° out of the active site. Quantitative real-time PCR results show that pa4079 maintains high expression levels during antibiotic exposure. This work provides a starting point for understanding substrate recognition and selectivity by PA4079, as well as its possible reduction of antimicrobial drugs.

DATABASE

Structural data are available in the Protein Data Bank (PDB) under the following accession numbers: apo PA4079 (condition I), 5WQM; apo PA4079 (condition II), 5WQN; PA4079 + NADP (condition I), 5WQO; PA4079 + NADP (condition II), 5WQP.

Metabolic carbonyl reduction of anthracyclines - role in cardiotoxicity and cancer resistance. Reducing enzymes as putative targets for novel cardioprotective and chemosensitizing agents

Anthracycline antibiotics (ANT), such as doxorubicin or daunorubicin, are a class of anticancer drugs that are widely used in oncology. Although highly effective in cancer therapy, their usefulness is greatly limited by their cardiotoxicity. Possible mechanisms of ANT cardiotoxicity include their conversion to secondary alcohol metabolites (i.e. doxorubicinol, daunorubicinol) catalyzed by carbonyl reductases (CBR) and aldo-keto reductases (AKR). These metabolites are suspected to be more cardiotoxic than their parent compounds. Moreover, overexpression of ANT-reducing enzymes (CBR and AKR) are found in many ANT-resistant cancers. The secondary metabolites show decreased cytotoxic properties and are more susceptible to ABC-mediated efflux than their parent compounds; thus, metabolite formation is considered one of the mechanisms of cancer resistance. Inhibitors of CBR and AKR were found to reduce the cardiotoxicity of ANT and the resistance of cancer cells, and therefore are being investigated as prospective cardioprotective and chemosensitizing drug candidates. In this review, the significance of a two-electron reduction of ANT, including daunorubicin, epirubicin, idarubicin, valrubicin, amrubicin, aclarubicin, and especially doxorubicin, is described with respect to toxicity and efficacy of therapy. Additionally, CBR and AKR inhibitors, including monoHER, curcumin, (−)-epigallocatechin gallate, resveratrol, berberine or pixantrone, and their modulating effect on the activity of ANT is characterized and discussed as potential mechanism of action for novel therapeutics in cancer treatment.

Recent Advances in Anticancer Activities and Drug Delivery Systems of Tannins

Tannins, polyphenols in medicinal plants, have been divided into two groups of hydrolysable and condensed tannins, including gallotannins, ellagitannins, and (-)-epigallocatechin-3-gallate (EGCG). Potent anticancer activities have been observed in tannins (especially EGCG) with multiple mechanisms, such as apoptosis, cell cycle arrest, and inhibition of invasion and metastases. Furthermore, the combinational effects of tannins and anticancer drugs have been demonstrated in this review, including chemoprotective, chemosensitive, and antagonizing effects accompanying with anticancer effect. However, the applications of tannins have been hindered due to their poor liposolubility, low bioavailability, off-taste, and shorter half-life time in human body, such as EGCG, gallic acid, and ellagic acid. To tackle these obstacles, novel drug delivery systems have been employed to deliver tannins with the aim of improving their applications, such as gelatin nanoparticles, micelles, nanogold, liposomes, and so on. In this review, the chemical characteristics, anticancer properties, and drug delivery systems of tannins were discussed with an attempt to provide a systemic reference to promote the development of tannins as anticancer agents.

Cancer Preventive Activities of Tea Catechins

Catechins are widely occurring in our diet and beverages. The cancer-preventive activities of catechins have been extensively studied. Of these, (-)-epigallocatechin-3-gallate (EGCG), the principal catechin in green tea, has received the most attention. The inhibitory activities of tea catechins against carcinogenesis and cancer cell growth have been demonstrated in a large number of laboratory studies. Many mechanisms for modulating cancer signaling and metabolic pathways have been proposed based on numerous studies in cell lines with EGCG, the most active tea catechin. Nevertheless, it is not known whether many of these mechanisms indeed contribute to the anti-cancer activities in animals and in humans. Human studies have provided some results for the cancer preventive activities of tea catechins; however, the activities are not strong. This article reviews the cancer preventive activities and mechanisms of action of tea catechins involving their redox activities, biochemical properties and binding to key enzymes or signal transduction proteins. These mechanisms lead to suppression of cell proliferation, increased apoptosis and inhibition of angiogenesis. The relevance of the proposed mechanisms for cancer prevention are assessed in the light of the situation in vivo. The potential and possible problems in the application of tea and tea-derived products for cancer prevention are discussed.

Emerging role of NRF2 in chemoresistance by regulating drug-metabolizing enzymes and efflux transporters

Chemoresistance is a disturbing barrier in cancer therapy, which always results in limited therapeutic options and unfavorable prognosis. Nuclear factor E2-related factor 2 (NRF2) controls the expression of genes encoding cytoprotective enzymes and transporters that protect against oxidative stress and electrophilic injury to maintain intrinsic redox homeostasis. However, recent studies have demonstrated that aberrant activation of NRF2 due to genetic and/or epigenetic mutations in tumor contributes to the high expression of phase I and phase II drug-metabolizing enzymes, phase III transporters, and other cytoprotective proteins, which leads to the decreased therapeutic efficacy of anticancer drugs through biotransformation or extrusion during chemotherapy. Therefore, a better understanding of the role of NRF2 in regulation of these enzymes and transporters in tumors is necessary to find new strategies that improve chemotherapeutic efficacy. In this review, we summarized the recent findings about the chemoresistance-promoting role of NRF2, NRF2-regulated phase I and phase II drug-metabolizing enzymes, phase III drug efflux transporters, and other cytoprotective genes. Most importantly, the potential of NRF2 was proposed to counteract drug resistance in cancer treatment.

(-)-Epigallocatechin-3-gallate (EGCG) attenuates arsenic-induced cardiotoxicity in rats

Chronic arsenic exposure in drinking water is associated with the abnormalities of cardiac tissue. Excessive generation of ROS induced by arsenic has a central role in arsenic-induced cardiotoxicity. (-)-Epigallocatechin-3-gallate (EGCG), the most abundant polyphenol in green tea, possesses a potent antioxidant capacity and exhibits extensive pharmacological activities. This study was aim to evaluate the effect of EGCG on arsenic-induced cardiotoxicity in vivo and in vitro. Treatment with NaAsO2 seriously affected the morphology and ultrastructure of myocardium, and induced cardiac injuries, oxidative stress, intracellular calcium accumulation and apoptosis in rats. In consistent with in vivo study, the injuries, oxidative stress and apoptosis were also observed in NaAsO2-treated H9c2 cells. All of these effects induced by NaAsO2 were attenuated by EGCG. These results suggest EGCG could attenuate NaAsO2-induced cardiotoxicity, and the mechanism may involve its potent antioxidant capacity.

Inhibition of human anthracycline reductases by emodin - A possible remedy for anthracycline resistance

The clinical application of anthracyclines, like daunorubicin and doxorubicin, is limited by two factors: dose-related cardiotoxicity and drug resistance. Both have been linked to reductive metabolism of the parent drug to their metabolites daunorubicinol and doxorubicinol, respectively. These metabolites show significantly less anti-neoplastic properties as their parent drugs and accumulate in cardiac tissue leading to chronic cardiotoxicity. Therefore, we aimed to identify novel and potent natural inhibitors for anthracycline reductases, which enhance the anticancer effect of anthracyclines by preventing the development of anthracycline resistance. Human enzymes responsible for the reductive metabolism of daunorubicin were tested for their sensitivity towards anthrachinones, in particular emodin and anthraflavic acid. Intense inhibition kinetic data for the most effective daunorubicin reductases, including IC50- and Ki-values, the mode of inhibition, as well as molecular docking, were compiled. Subsequently, a cytotoxicity profile and the ability of emodin to reverse daunorubicin resistance were determined using multiresistant A549 lung cancer and HepG2 liver cancer cells. Emodin potently inhibited the four main human daunorubicin reductases in vitro. Further, we could demonstrate that emodin is able to synergistically sensitize human cancer cells towards daunorubicin at clinically relevant concentrations. Therefore, emodin may yield the potential to enhance the therapeutic effectiveness of anthracyclines by preventing anthracycline resistance via inhibition of the anthracycline reductases. In symphony with its known pharmacological properties, emodin might be a compound of particular interest in the management of anthracycline chemotherapy efficacy and their adverse effects.

Green tea polyphenols and their potential role in health and disease

There is a growing body of evidence that plant polyphenols such as resveratrol, anthocyanins, catechins, and terpenes like taxol are effectively used in the treatment of chronic conditions including cancer, Alzheimer, Parkinsonism, diabetes, aging, etc. The link between oxidative stress and inflammation is well accepted. Thus, the mechanism of action of these natural products is partly believed to be through their significant antioxidant properties. The main constituent of green tea, with clinical significance, is epigallocatechin gallate (EGCG). It has been associated with antitumor, anti-Alzheimer, and anti-aging properties, improve redox status at the tissue level possibly preventing system level structural damage. This review focuses on EGCG and its potential therapeutic role in health and disease.

Effects of Tea Catechins on Cancer Signaling Pathways

The inhibitory activities of tea catechins against carcinogenesis and cancer cell growth have been demonstrated in a large number of laboratory studies. Many mechanisms for modulating cancer signaling and metabolic pathways have been proposed based on numerous studies in cell lines with (-)-epigallocatechin-3-gallate, the most abundant and active tea catechin. Nevertheless, the molecular basis for the proposed mechanisms and whether these mechanisms indeed contribute to the anticancer activities in vivo are not clearly known. This chapter reviews the basic redox properties of tea catechins, their binding to key enzymes and signal transduction proteins, and other mechanisms that lead to suppression of cell proliferation, increased apoptosis, and inhibition of angiogenesis. More weight is put on studies in vivo over experiments in vitro. It also discusses key issues involved in extrapolating results from cell line studies to mechanistic insights in vivo.

(-)-Epigallocatechin-3-gallate, a potential inhibitor to human dicarbonyl/L-xylulose reductase

Dicarbonyl/l-xylulose reductase (DCXR), mainly catalysing the reduction of α-dicarbonyl compounds and l-xylulose, belongs to the short-chain dehydrogenase/reductase superfamily. Its enzyme activity can be inhibited by short-chain fatty acids. In this study, a novel DCXR inhibitor named (-)-epigallocatechin-3-gallate (EGCG) was reported. First, we overexpressed recombinant human DCXR in Escherichia coli, purified the enzyme by affinity chromatography and measured its activity. The inhibition effects of EGCG and its analogues on DCXR were determined subsequently, and EGCG showed the strongest inhibition with 50% inhibition concentration value of 78.8 μM. The surface plasmon resonance analysis also indicated that the equilibrium dissociation constant (KD) reached to 7.11 × 10(-8) M, which implied a high affinity between EGCG and DCXR. From enzyme kinetic analysis, EGCG acted as a mixed inhibitor against its forward and reverse substrates and the coenzyme, reduced nicotinamide adenine dinucleotide phosphate (NADPH). However, the inhibition is pH dependent. The molecular docking finally showed that EGCG formed several hydrogen bonds with the Thr190 residue of DCXR, and the model was further verified by site-directed mutagenesis. Therefore, EGCG is a potential inhibitor to human DCXR.

Transport by OATP1B1 and OATP1B3 enhances the cytotoxicity of epigallocatechin 3-O-gallate and several quercetin derivatives

Organic anion transporting polypeptides (OATPs) 1B1 and 1B3 are transporters that are expressed selectively in human hepatocytes under normal conditions. OATP1B3 is also expressed in certain cancers. Flavonoids such as green tea catechins and quercetin glycosides have been shown to modulate the function of some OATPs. In the present study, the extent to which six substituted quercetin derivatives (1-6) affected the function of OATP1B1 and OATP1B3 was investigated. Uptake of the radiolabeled model substrates estradiol 17β-glucuronide, estrone 3-sulfate, and dehydroepiandrosterone sulfate (DHEAS) was determined in the absence and presence of compounds 1-6 using Chinese hamster ovary (CHO) cells stably expressing either OATP1B1 or OATP1B3. Several of compounds 1-6 inhibited OATP-mediated uptake of all three model substrates, suggesting that they could also be potential substrates. Compound 6 stimulated OATP1B3-mediated estradiol 17β-glucuronide uptake by increasing the apparent affinity of OATP1B3 for its substrate. Cytotoxicity assays demonstrated that epigallocatechin 3-O-gallate (EGCG) and most of compounds 1-6 killed preferentially OATP-expressing CHO cells. EGCG, 1, and 3 were the most potent cytotoxic compounds, with EGCG and 3 selectively killing OATP1B3-expressing cells. Given that OATP1B3 is expressed in several cancers, EGCG and some of the quercetin derivatives studied might be promising lead compounds for the development of novel anticancer drugs.

Green tea polyphenol epigallocatechin-3-gallate (EGCG) as adjuvant in cancer therapy

BACKGROUND & AIMS

Green tea catechins, especially epigallocatechin-3-gallate (EGCG), have been associated with cancer prevention and treatment. This has resulted in an increased number of studies evaluating the effects derived from the use of this compound in combination with chemo/radiotherapy. This review aims at compiling latest literature on this subject.

METHODS

Keywords including EGCG, cancer, chemotherapy, radiotherapy and side effects, were searched using PubMed and ScienceDirect databases to identify, analyze, and summarize the research literature on this topic. Most of the studies on this subject up to date are preclinical. Relevance of the findings, impact factor, and date of publication were critical parameters for the studies to be included in the review.

RESULTS

Additive and synergistic effects of EGCG when combined with conventional cancer therapies have been proposed, and its anti-inflammatory and antioxidant activities have been related to amelioration of cancer therapy side effects. However, antagonistic interactions with certain anticancer drugs might limit its clinical use.

CONCLUSIONS

The use of EGCG could enhance the effect of conventional cancer therapies through additive or synergistic effects as well as through amelioration of deleterious side effects. Further research, especially at the clinical level, is needed to ascertain the potential role of EGCG as adjuvant in cancer therapy.

Regulation of human carbonyl reductase 1 (CBR1, SDR21C1) gene by transcription factor Nrf2

Monomeric carbonyl reductase 1 (CBR1, SDR21C1) is a member of the short-chain dehydrogenase/reductase superfamily and is involved in the metabolism of anthracycline anti-cancer drugs, prostaglandins, and isatin, which is an endogenous inhibitor of monoamine oxidases. Additionally, cancer progression may be partly regulated by CBR1. In the present study, we screened more than 10 drugs for the induction of the human CBR1 gene to investigate its regulation. Of the drugs, butylated hydroxyanisole (BHA) was found to be an inducer. BHA induced the mRNA and protein expression of CBR1 in hepatoma HepG2 cells. In a luciferase reporter gene assay, the promoter region between -2062 bp and the transcription start site of CBR1 was also activated by BHA. The transcription factor Nrf2 is known to be activated by BHA. There are 2 anti-oxidant responsive elements (ARE) that are bound by Nrf2 in this region. Mutation analyses revealed that one of the AREs participates in the gene regulation of CBR1 by Nrf2. Electrophoretic mobility shift assay revealed that Nrf2 binds the site. Moreover, to determine whether the functional ARE of CBR1 is conserved with the promoter region of homologues in other species, the nucleotide sequences of the functional AREs of the Chcr1 and Chcr2 genes, which are the Chinese hamster homologues of CBR1, were determined. The region has 2 AREs, and these genes were also induced by the forced expression of Nrf2 (cotransfection of pNrf2) in the luciferase reporter gene assay. In conclusion, Nrf2 is a novel transcriptional regulator of CBR1 genes in humans and the Chinese hamster. Because the regulation of CBR1 appears to be important for diseases, the induction of CBR1 by Nrf2 may be a therapeutic target.