Hesperetin Induces the Apoptosis of Gastric Cancer Cells via Activating Mitochondrial Pathway by Increasing Reactive Oxygen Species

Plant bioactive compounds driven microRNAs (miRNAs): A potential source and novel strategy targeting gene and cancer therapeutics

Irrespective of medical technology improvements, cancer ranks among the leading causes of mortality worldwide. Although numerous cures and treatments exist, creating alternative cancer therapies with fewer adverse side effects is vital. Since ancient times, plant bioactive compounds have already been used as a remedy to heal cancer. These plant bioactive compounds and their anticancer activity can also deregulate the microRNAs (miRNAs) in the cancerous cells. Therefore, the deregulation of miRNAs in cancer cells by plant bioactive compounds and the usage of the related miRNA could be a promising approach for cancer cure, mainly to prevent cancer and overcome chemotherapeutic side effect problems. Hence, this review highlights the function of plant bioactive compounds as an anticancer agent through the underlying mechanism that alters the miRNA expression in cancer cells, ultimately leading to apoptosis. Moreover, this review provides insight into using plant bioactive compounds -driven miRNAs as an anticancer agent to develop miRNA-based cancer gene therapy. They can be the potential resource for gene therapy and novel strategies targeting cancer therapeutics.

The flavonoids from the fruits of Psoralea corylifolia and their potential in inhibiting metastasis of human non-small cell lung cancers

Nineteen flavonoids were isolated from the fruits of Psoralea corylifolia L., including a novel flavanol (3) and three novel isoflavones (12-14). Their chemical structures were unequivocally determined through comprehensive spectral data analysis. The anti-proliferative effect of the isolated flavonoids was assessed in vitro using the MTT assay. Molecular docking and ELISA were employed to determine the inhibitory effects of the active compounds on ALK5. Isobavachalcone was found to inhibit TGF-β1 induced EMT in A549 cells by Wound healing assay and Transwell chamber assay. Immunofluorescence assay and Western blot assay showed that IBC could inhibit cytoskeleton rearrangement, reduce the phosphorylation of ALK5, ERK, and Smad, down-regulate Snail expression, and up-regulate E-cadherin expression in TGF-β1 induced A549 cells, thereby exerting the potential inhibitory effects on epithelial-mesenchymal transition (EMT) process in A549 cells. The findings presented herein establish a fundamental basis for investigating the anti-proliferative and anti-metastatic properties of psoralen flavonoids in human non-small cell lung cancer.

A mixed-apoptotic effect of Jurinea mesopotamica extract on prostate cancer cells: a promising source for natural chemotherapeutics

This research investigates the potential use of Jurinea mesopotamica Hand.-Mazz. (Asteraceae) in cancer treatment. In this study, a plant extract was prepared using all parts of J. mesopotamica, and its effect on the proliferation of cancer and normal cells was tested using the MTT method. It was found to have a selective cytotoxic effect on prostate cancer cells, with the lowest IC50 (half-maximal inhibitory concentration) of 10μg/mL found in the butanol extract (JMBE). The extract suppressed the proliferation of prostate cancer cells (67 %), disrupted organelle integrity (49 %), increased reactive oxidative stress (66 %), and triggered cell death (51 %). In addition, apoptotic gene expressions and protein levels increased, and the profile of amino acids related to energy metabolism was elevated. Based on LC-MS/MS results, the plant contained higher levels of flavonoids, including isoquercitrin, cosmosiin, astragalin, nicotiflorin, luteolin, and apigenin. These results suggest that J. mesopotamica has a selective effect on prostate cancer due to its high flavonoid content and might be a promising natural alternative for cancer treatment.

Evaluation of the toxicity of Caralluma europaea (C.E) extracts and their effects on apoptosis and chemoresistance in pancreatic cancer cells

Pancreatic adenocarcinoma is a disease with no effective treatment. Chemo-resistance contributes to the dismal prognosis for patients diagnosed with the disease. This study aims to evaluate the toxicity and the effect of Caralluma europaea (C.E) extracts on cancer cell survival, apoptosis, chemo-resistance, and pro-cancer pathways, in pancreatic cancer. The acute and subacute toxicities of C.E extracts were evaluated. The cytotoxic effect on pancreatic cancer cell survival and apoptosis was determined by MTT assay and DNA fragmentation. The expression of cancer stemness markers was measured using Western blot. A molecular docking was used to test the possible effects of C.E compounds in inhibiting the Hedgehog and activating caspase-3. The hydroethanolic extract's DL50 was over 5000 mg/kg. During the subacute toxicity, only saponins extract showed some hepatic toxicity signs. Cells treated with C.E extracts combined with gemcitabine revealed an additive anti-survival activity. C.E extracts sensitized resistant MIA-PaCa-2 to gemcitabine treatment. Most of the C.E extracts downregulated the expression of cancer stemness-associated genes. Luteolin-7-O-glucoside presented the highest docking Gscore on human Smoothened. Isorhamnetin-3-O-rutinoside induced apoptosis via activation of caspase-3. C.E extracts can be considered safe in inhibiting pancreatic cancer cell survival, inducing apoptosis, and sensitizing cells to chemotherapy via Hedgehog inhibition and caspase-3 activation.Communicated by Ramaswamy H. Sarma.

The Involvement of Natural Polyphenols in Molecular Mechanisms Inducing Apoptosis in Tumor Cells: A Promising Adjuvant in Cancer Therapy

Various literature data show how a diet rich in vegetables could reduce the incidence of several cancers due to the contribution of the natural polyphenols contained in them. Polyphenols are attributed multiple pharmacological actions such as anti-inflammatory, anti-oxidant, antibiotic, antiseptic, anti-allergic, cardioprotective and even anti-tumor properties. The multiple mechanisms involved in their anti-tumor action include signaling pathways modulation associated with cell proliferation, differentiation, migration, angiogenesis, metastasis and cell death. Since the dysregulation of death processes is involved in cancer etiopathology, the natural compounds able to kill cancer cells could be used as new anticancer agents. Apoptosis, a programmed form of cell death, is the most potent defense against cancer and the main mechanism used by both chemotherapy agents and polyphenols. The aim of this review is to provide an update of literature data on the apoptotic molecular mechanisms induced by some representative polyphenol family members in cancer cells. This aspect is particularly important because it may be useful in the design of new therapeutic strategies against cancer involving the polyphenols as adjuvants.

Anticancer applications of phytochemicals in gastric cancer: Effects and molecular mechanism

Gastric cancer (GC) is the fourth most common malignant cancer and is a life-threatening disease worldwide. Phytochemicals have been shown to be a rational, safe, non-toxic, and very promising approach to the prevention and treatment of cancer. It has been found that phytochemicals have protective effects against GC through inhibiting cell proliferation, inducing apoptosis and autophagy, suppressing cell invasion and migration, anti-angiogenesis, inhibit Helicobacter pylori infection, regulating the microenvironment. In recent years, the role of phytochemicals in the occurrence, development, drug resistance and prognosis of GC has attracted more and more attention. In order to better understand the relationship between phytochemicals and gastric cancer, we briefly summarize the roles and functions of phytochemicals in GC tumorigenesis, development and prognosis. This review will probably help guide the public to prevent the occurrence and development of GC through phytochemicals, and develop functional foods or drugs for the prevention and treatment of gastric cancer.

Recent Progress in the Hesperetin Delivery Regimes: Significance of Pleiotropic Actions and Synergistic Anticancer Efficacy

BACKGROUND

In the plant kingdom, flavonoids are widely distributed with multifunctional immunomodulatory actions. Hesperetin (HST) remains one of the well-studied compounds in this domain, initially perceived in citrus plants as an aglycone derivative of hesperidin (HDN).

OBSERVATIONS

Natural origin, low in vivo toxicity, and pleiotropic functional essence are the foremost fascinations for HST use as an anticancer drug. However, low aqueous solubility accompanied with a prompt degradation by intestinal and hepatocellular enzymes impairs HST physiological absorption.

MOTIVATION

Remedies attempted herein comprise the synthesis of derivatives and nanocarrier (NC)-mediated delivery. As the derivative synthesis aggravates the structural complexity, NC-driven HST delivery has emerged as a sustainable approach for its sustained release. Recent interest in HST has been due to its significant anticancer potential, characterized via inhibited cell division (proliferation), new blood vessel formation (angiogenesis), forceful occupation of neighboring cell's space (invasion), migration to erstwhile physiological locations (metastasis) and apoptotic induction. The sensitization of chemotherapeutic drugs (CDs) by HST is driven via stoichiometrically regulated synergistic actions. Purpose and Conclusion: This article sheds light on HST structure-function correlation and pleiotropic anticancer mechanisms, in unaided and NC-administered delivery in singular and with CDs synergy. The discussion could streamline the HST usefulness and long-term anticancer efficacy.

Hesperidin Reversed Long-Term N-methyl-N-nitro-N-Nitroguanidine Exposure Induced EMT and Cell Proliferation by Activating Autophagy in Gastric Tissues of Rats

Gastric cancer is a common malignant tumor worldwide. N-methyl-N-nitro-N-nitroguanidine (MNNG) is one of the most important inducing factors of gastric cancer. Autophagy can affect the occurrence and development of gastric cancer, but the mechanism is not clear. Chemoprevention has been shown to be a rational and very promising approach to the prevention of gastric cancer. Hesperidin is a citrus flavone, an abundant polyphenol in citrus fruits and traditional Chinese medicine. It has an excellent phytochemistry that plays an intervention role in gastric cancer. However, it is unclear whether long-term exposure to MNNG will affect the occurrence of gastric cancer by regulating autophagy and whether hesperidin can play an intervention role in this process. In the present study, we demonstrated that long-term MNNG exposure inhibits autophagy in stomach tissues of rats, promotes the epithelial-mesenchymal transition (EMT) process and cell proliferation and suppresses the activity of the PI3K/AKT pathway. We further found that after rapamycin-activated autophagy, long-term MNNG exposure promoted cell proliferation and EMT were inhibited. In addition, hesperidin promotes autophagy and the activity of the PI3K/AKT pathway, as well as the suppression of proliferation and EMT in the stomach tissues of rats. Our findings indicate that hesperidin reverses MNNG-induced gastric cancer by activating autophagy and the PI3K/AKT pathway, which may provide a new basis for the early prevention and treatment of MNNG-induced gastric cancer.

Flavonoids' Dual Benefits in Gastrointestinal Cancer and Diabetes: A Potential Treatment on the Horizon?

Diabetes and gastrointestinal cancers (GI) are global health conditions with a massive burden on patients' lives worldwide. The development of both conditions is influenced by several factors, such as diet, genetics, environment, and infection, which shows a potential link between them. Flavonoids are naturally occurring phenolic compounds present in fruits and vegetables. Once ingested, unabsorbed flavonoids reaching the colon undergo enzymatic modification by the gut microbiome to facilitate absorption and produce ring fission products. The metabolized flavonoids exert antidiabetic and anti-GI cancer properties, targeting major impaired pathways such as apoptosis and cellular proliferation in both conditions, suggesting the potentially dual effects of flavonoids on diabetes and GI cancers. This review summarizes the current knowledge on the impact of flavonoids on diabetes and GI cancers in four significant pathways. It also addresses the synergistic effects of selected flavonoids on both conditions. While this is an intriguing approach, more studies are required to better understand the mechanism of how flavonoids can influence the same impaired pathways with different outcomes depending on the disease.

Hesperidin inhibits tobacco smoke-induced pulmonary cell proliferation and EMT in mouse lung tissues via the p38 signaling pathway

Tobacco smoke (TS) is the major cause of lung cancer. The abnormal proliferation and epithelial-mesenchymal transition (EMT) of lung cells promote occurrence and development of lung cancer. The p38 pathway intervenes in this cancer development. Hesperidin also serves a role in human health and disease prevention. The roles of p38 in TS-mediated abnormal cell proliferation and EMT, and the hesperidin intervention thereof are not yet understood. In the present study, it was demonstrated that TS upregulated proliferating cell nuclear antigen, vimentin and N-cadherin expression, whereas it downregulated E-cadherin expression, as assessed using western blotting and reverse transcription-quantitative PCR. Furthermore, it was observed that inhibition of the p38 pathway inhibit TS-induced proliferation and EMT. Hesperidin treatment prevented the TS-induced activation of the p38 pathway, EMT and cell proliferation in mouse lungs. The findings of the present study may provide insights into the pathogenesis of TS-related lung cancer.

"True" Helicobacter pylori infection and non-cardia gastric cancer: A pooled analysis within the Stomach Cancer Pooling (StoP) Project

BACKGROUND

Helicobacter pylori is the most important risk factor for non-cardia gastric cancer (NCGC); however, the magnitude of the association varies across epidemiological studies. This study aimed to quantify the association between H. pylori infection and NCGC, using different criteria to define infection status.

METHODS

A pooled analysis of individual-level H. pylori serology data from eight international studies (1325 NCGC and 3121 controls) from the Stomach Cancer Pooling (StoP) Consortium was performed. Cases and controls with a negative H. pylori infection status were reclassified as positive considering the presence of anti-Cag A antibodies, gastric atrophy, or advanced stage at diagnosis, as available and applicable. A two-stage approach was used to pool study-specific adjusted odds ratios (OR), and 95% confidence intervals (95% CI). A meta-analysis of published prospective studies assessing H. pylori seropositivity in NCGCs was conducted.

RESULTS

The OR for the association between serology-defined H. pylori and NCGC was 1.45 (95% CI: 0.87-2.42), which increased to 4.79 (95% CI: 2.39-9.60) following the reclassification of negative H. pylori infection. The results were consistent across strata of sociodemographic characteristics, clinical features and lifestyle factors, though significant differences were observed according to geographic region-a stronger association in Asian studies. The pooled risk estimates from the literature were 3.01 (95% CI: 2.22-4.07) for ELISA or EIA and 9.22 (95% CI: 3.12-27.21) for immunoblot or multiplex serology.

CONCLUSION

The NCGC risk estimate from StoP based on the reclassification of H. pylori seronegative individuals is consistent with the risk estimates obtained from the literature. Our classification algorithm may be useful for future studies.

Chemical Structure, Sources and Role of Bioactive Flavonoids in Cancer Prevention: A Review

There has been a major shift in the collective mindset around the world in recent decades, both in terms of food and in terms of the treatment of chronic diseases. Increasing numbers of people are choosing to prevent rather than treat, which is why many consumers are choosing plant-based diets, mainly due to their bioactive compounds. A significant case of bioactive compound is flavonoids-a wide subclass of an even wider class of phytochemicals: polyphenols. Flavonoids are a broad topic of study for researchers due to their potential in the prevention and treatment of a broad range of cancers. The aim of this review is to inform/update the reader on the diversity, accessibility and importance of flavonoids as biomolecules that are essential for optimal health, focusing on the potential of these compounds in the prevention of various types of cancer. Along with conventional sources, this review presents some of the possible methods for obtaining significant amounts of flavonoids based on a slightly different approach, genetic manipulation.

Therapeutic potential of flavonoids in cancer: ROS-mediated mechanisms

Cancer is a leading cause of morbidity and mortality around the globe. Reactive oxygen species (ROS) play contradicting roles in cancer incidence and progression. Antioxidants have attracted attention as emerging therapeutic agents. Among these are flavonoids, which are natural polyphenols with established anticancer and antioxidant capacities. Increasing evidence shows that flavonoids can inhibit carcinogenesis via suppressing ROS levels. Surprisingly, flavonoids can also trigger excessive oxidative stress, but this can also induce death of malignant cells. In this review, we explore the inherent characteristics that contribute to the antioxidant capacity of flavonoids, and we dissect the scenarios in which they play the contrasting role as pro-oxidants. Furthermore, we elaborate on the pathways that link flavonoid-mediated modulation of ROS to the prevention and treatment of cancer. Special attention is given to the ROS-mediated anticancer functions that (-)-epigallocatechin gallate (EGCG), hesperetin, naringenin, quercetin, luteolin, and apigenin evoke in various cancers. We also delve into the structure-function relations that make flavonoids potent antioxidants. This review provides a detailed perspective that can be utilized in future experiments or trials that aim at utilizing flavonoids or verifying their efficacy for developing new pharmacologic agents. We support the argument that flavonoids are attractive candidates for cancer therapy.

Chemotherapeutic potential of hesperetin for cancer treatment, with mechanistic insights: A comprehensive review

BACKGROUND

Cancer has become a significant concern in the medical sector with increasing disease complexity. Although some available conventional treatments are still a blessing for cancer patients, short-and long-term adverse effects and poor efficiency make it more difficult to treat cancer patients, demonstrating the need for new potent and selective anticancer drugs. In search of potent anticancer agents, naturally occurring compounds have always been admired due to their structural diversity, where Hesperetin (HSP) may be one of the potent candidates.

PURPOSE

We aimed to summarize all sources, pharmacological properties, anticancer activities of HSP against numerous cancers types through targeting multiple pathological processes, mechanism of HSP on sensitizing the current anti-cancer agents and other phytochemicals, overcoming resistance pattern and determining absorption, distribution, metabolism, excretion, and toxicity (ADME/Tox).

METHODS

Information was retrieved from PubMed, Science Direct, and Google Scholar based on some key points like Hesperetin, cancer name, anticancer resistance, nanoformulation, and ADME/Tox was determined by in silico approaches.

RESULT

HSP is a phytoestrogen present in citrus fruits in a high concentration (several hundred mg/kg) and exhibited anti-cancer activities through interfering at several pathways. HSP can suppress tumor formation by targeting several cellular proteins such as cell cycle regulatory, apoptosis, metastatic, tyrosine kinase, growth factor receptor, estrogen metabolism, and antioxidant-related protein.HSP has shown remarkable synergistic properties in combination therapy and has been reported to overcome multidrug cancer resistance drugs, leading to an improved defensive mechanism. These anticancer activities of HSP may be due to proper structural chemistry.

CONCLUSION

Overall, HSP showed potential anticancer activities against all cancer and possess better pharmacokinetic properties. So this phytochemical alone or combination with other agents can be an effective alternative drug for cancer treatment.

Apigenin Induces Autophagy and Cell Death by Targeting EZH2 under Hypoxia Conditions in Gastric Cancer Cells

Hypoxia is a major obstacle to gastric cancer (GC) therapy and leads to chemoresistance as GC cells are frequently exposed to the hypoxia environment. Apigenin, a flavonoid found in traditional medicine, fruits, and vegetables and an HDAC inhibitor, is a powerful anti-cancer agent against various cancer cell lines. However, detailed mechanisms involved in the treatment of GC using APG are not fully understood. In this study, we investigated the biological activity of and molecular mechanisms involved in APG-mediated treatment of GC under hypoxia. APG promoted autophagic cell death by increasing ATG5, LC3-II, and phosphorylation of AMPK and ULK1 and down-regulating p-mTOR and p62 in GC. Furthermore, our results show that APG induces autophagic cell death via the activation of the PERK signaling, indicating an endoplasmic reticulum (ER) stress response. The inhibition of ER stress suppressed APG-induced autophagy and conferred prolonged cell survival, indicating autophagic cell death. We further show that APG induces ER stress- and autophagy-related cell death through the inhibition of HIF-1α and Ezh2 under normoxia and hypoxia. Taken together, our findings indicate that APG activates autophagic cell death by inhibiting HIF-1α and Ezh2 under hypoxia conditions in GC cells.

8-Formylophiopogonanone B induces ROS-mediated apoptosis in nasopharyngeal carcinoma CNE-1 cells

Cancer is one of the leading causes of death in the world. It is very important to find drugs with high efficiency, low toxicity, and low side effects for the treatment of cancer. Flavonoids and their derivatives with broad biological functions have been recognized as anti-tumor chemicals. 8-Formylophiopogonanone B (8-FOB), a naturally existed homoisoflavonoids with rarely known biological functions, needs pharmacological evaluation. In order to explore the possible anti-tumor action of 8-FOB, we used six types of tumor cells to evaluate in vitro effects of this agent on cell viability and tested the effects on clone formation ability, scratching wound-healing, and apoptosis. In an attempt to elucidate the mechanism of pharmacological action, we examined 8-FOB-induced intracellular oxidative stress and -disrupted mitochondrial function. Results suggested that 8-FOB could suppress tumor cell viability, inhibit cell migration and invasion, induce apoptosis, and elicit intracellular ROS production. Among these six types of tumor cells, the nasopharyngeal carcinoma CNE-1 cells were the most sensitive cancer cells to 8-FOB treatment. Intracellular ROS production played a pivotal role in the anti-tumor action of 8-FOB. Our present study is the first to document that 8-FOB has anti-tumor activity in vitro and increases intracellular ROS production, which might be responsible for its anti-tumor action. The anti-tumor pharmacological effect of 8-FOB is worthy of further investigation.

Repurposing Natural Dietary Flavonoids in the Modulation of Cancer Tumorigenesis: Decrypting the Molecular Targets of Naringenin, Hesperetin and Myricetin

In the past few years flavonoids have been gaining more attention regarding their (still un) exploited anticancer properties. Flavonoids are natural compounds present in fruits, vegetables, and seeds, meaning that they are already present in the daily life of every person, with a described broad-spectrum of pharmacological activities, including anticancer, anti-inflammatory and antioxidant. In the present review we discuss the anticancer activity of three important flavonoids - myricetin (MYR) (flavanol group), hesperetin (HESP) and naringenin (NAR) (flavanone group). Although some mechanisms underlying their activities remain still unclear, they can act as potential inhibitors of key tumorigenic signaling pathways, such as PI3K/Akt/mTOR, p38 MAPK and NF-κB. Simultaneously, they can reset the levels of pro-apoptotic proteins that belong to the Bcl-2 and caspase family and decrease the intracellular levels of ROS and pro-inflammatory cytokines, such as TNF-α, IL-1β and IL-6. Together with their synergetic effect they have the potential to become key elements in the prevention and/or treatment of several types of cancer, with the major improvement to the patient life quality, due to their non-existent toxicity.

Bcl-2 Modulation in p53 Signaling Pathway by Flavonoids: A Potential Strategy towards the Treatment of Cancer

Cancer is a major cause of death, affecting human life in both developed and developing countries. Numerous antitumor agents exist but their toxicity and low efficacy limits their utility. Furthermore, the complex pathophysiological mechanisms of cancer, serious side effects and poor prognosis restrict the administration of available cancer therapies. Thus, developing novel therapeutic agents are required towards a simultaneous targeting of major dysregulated signaling mediators in cancer etiology, while possessing lower side effects. In this line, the plant kingdom is introduced as a rich source of active phytochemicals. The secondary metabolites produced by plants could potentially regulate several dysregulated pathways in cancer. Among the secondary metabolites, flavonoids are hopeful phytochemicals with established biological activities and minimal side effects. Flavonoids inhibit B-cell lymphoma 2 (Bcl-2) via the p53 signaling pathway, which is a significant apoptotic target in many cancer types, hence suppressing a major dysregulated pathway in cancer. To date, there have been no studies reported which extensively highlight the role of flavonoids and especially the different classes of flavonoids in the modulation of Bcl-2 in the P53 signaling pathway. Herein, we discuss the modulation of Bcl-2 in the p53 signaling pathway by different classes of flavonoids and highlight different mechanisms through which this modulation can occur. This study will provide a rationale for the use of flavonoids against different cancers paving a new mechanistic-based approach to cancer therapy.

Flavonoids as Molecules With Anti-Zika virus Activity

Zika virus (ZIKV) is an arthropod-born virus that is mainly transmitted to humans by mosquitoes of the genus Aedes spp. Since its first isolation in 1947, only a few human cases had been described until large outbreaks occurred on Yap Island (2007), French Polynesia (2013), and Brazil (2015). Most ZIKV-infected individuals are asymptomatic or present with a self-limiting disease and nonspecific symptoms such as fever, myalgia, and headache. However, in French Polynesia and Brazil, ZIKV outbreaks led to the diagnosis of congenital malformations and microcephaly in newborns and Guillain-Barré syndrome (GBS) in adults. These new clinical presentations raised concern from public health authorities and highlighted the need for anti-Zika treatments and vaccines to control the neurological damage caused by the virus. Despite many efforts in the search for an effective treatment, neither vaccines nor antiviral drugs have become available to control ZIKV infection and/or replication. Flavonoids, a class of natural compounds that are well-known for possessing several biological properties, have shown activity against different viruses. Additionally, the use of flavonoids in some countries as food supplements indicates that these molecules are nontoxic to humans. Thus, here, we summarize knowledge on the use of flavonoids as a source of anti-ZIKV molecules and discuss the gaps and challenges in this area before these compounds can be considered for further preclinical and clinical trials.

Enzymatic Metabolism of Flavonoids by Gut Microbiota and Its Impact on Gastrointestinal Cancer

Gastrointestinal (GI) cancer is a prevalent global health disease with a massive burden on health care providers. Internal and external factors such as obesity, smoking, diet (red meat), low socioeconomic status and infection with Helicobacter pylori are the critical risk factors of GI cancers. Flavonoids are natural phenolic compounds found abundantly in fruits and vegetables. Upon ingestion, 90% of flavonoids consumed require further enzymatic metabolism by the gut microbiome to enhance their bioavailability and absorption. Several epidemiological studies reported that consumption of flavonoids and their enzymatic conversion by gut microbes is strongly associated with the reduced risk of GI cancer development. This review summarizes the current knowledge on the enzymatic conversion of flavonoids by the human gut microbiome. It also addresses the underlying anti-GI cancer effects on metabolic pathways such as apoptosis and cellular proliferation. Overall, metabolites produced from flavonoid's enzymatic conversion illustrate anti-GI cancer effects, but the mechanisms of action need further clarification.

Hesperetin promotes DOT1L degradation and reduces histone H3K79 methylation to inhibit gastric cancer metastasis

BACKGROUND

There have been many researches on the effects of flavonoids on tumor treatment or adjuvant therapy, but there are few studies revealing their epigenetic effect on tumors. Hesperetin is a common citrus flavanone widely distributed among citrus fruits. The role of hesperetin in gastric cancer metastasis is unclear.

PURPOSE

To investigate the effect of hesperetin on gastric cancer metastasis and its underlying mechanism.

METHODS

We used cancer cell lines cultured in medium and nude mice implantation as in vitro and in vivo models to investigate the impact of hesperetin treatment on the migration and invasion of gastric cancer cells. The molecular biological experiments such as transwell assay, western blotting, qPCR, ChIP-qPCR, immunostaining and transfection were conducted to explore the molecular mechanisms.

RESULTS

We found that hesperetin obviously reduced the protein abundance of DOT1L and the methylation of histone H3K79 in a variety of cells. In gastric cancer cells, the treatment of hesperetin decreased cell migration and invasion and the expression of genes closely related to the metastatic capability. Mechanistically, hesperetin affected the stability of DOT1L protein by regulating the activity of CBP.

CONCLUSION

These findings highlight the epigenetic effect of hesperetin and provide a new perspective to understand the tumor suppressive effect of flavonoids.

Anticancer activity of flavonoids accompanied by redox state modulation and the potential for a chemotherapeutic strategy

Since researchers began studying the mechanism of flavonoids' anticancer activity, little attention has been focused on the modulation of redox state in cells as a potential chemotherapeutic strategy. However, recent studies have begun identifying that the anticancer effect of flavonoids occurs both in their antioxidative activity which scavenges ROS and their prooxidative activity which generates ROS. Against this backdrop, this study attempts to achieve a comprehensive analysis of the individual and separate study findings regarding flavonoids' modulation of redox state in cancer cells. It focuses on the mechanism behind the anticancer effect, and mostly on the modulation of redox potential by flavonoids such as quercetin, hesperetin, apigenin, genistein, epigallocatechin-3-gallate (EGCG), luteolin and kaempferol in both in vitro and animal models. In addition, the clinical applications of and bioavailability of flavonoids were reviewed to help build a treatment strategy based on flavonoids' prooxidative potential.

Hesperetin's health potential: moving from preclinical to clinical evidence and bioavailability issues, to upcoming strategies to overcome current limitations

Flavonoids are common in the plant kingdom and many of them have shown a wide spectrum of bioactive properties. Hesperetin (Hst), the aglycone form of hesperidin, is a great example, and is the most abundant flavonoid found in Citrus plants. This review aims to provide an overview on the in vitro, in vivo and clinical studies reporting the Hst pharmacological effects and to discuss the bioavailability-related issues. Preclinical studies have shown promising effects on cancer, cardiovascular diseases, carbohydrate dysregulation, bone health, and other pathologies. Clinical studies have supported the Hst promissory effects as cardioprotective and neuroprotective agent. However, further well-designed clinical trials are needed to address the other Hst effects observed in preclinical trials, as well as to a more in-depth understanding of its safety profile.

Fruits and vegetables intake and gastric cancer risk: A pooled analysis within the Stomach cancer Pooling Project

A low intake of fruits and vegetables is a risk factor for gastric cancer, although there is uncertainty regarding the magnitude of the associations. In our study, the relationship between fruits and vegetables intake and gastric cancer was assessed, complementing a previous work on the association betweenconsumption of citrus fruits and gastric cancer. Data from 25 studies (8456 cases and 21 133 controls) with information on fruits and/or vegetables intake were used. A two-stage approach based on random-effects models was used to pool study-specific adjusted (sex, age and the main known risk factors for gastric cancer) odds ratios (ORs) and the corresponding 95% confidence intervals (CIs). Exposure-response relations, including linear and nonlinear associations, were modeled using one- and two-order fractional polynomials. Gastric cancer risk was lower for a higher intake of fruits (OR: 0.76, 95% CI: 0.64-0.90), noncitrus fruits (OR: 0.86, 95% CI: 0.73-1.02), vegetables (OR: 0.68, 95% CI: 0.56-0.84), and fruits and vegetables (OR: 0.61, 95% CI: 0.49-0.75); results were consistent across sociodemographic and lifestyles categories, as well as study characteristics. Exposure-response analyses showed an increasingly protective effect of portions/day of fruits (OR: 0.64, 95% CI: 0.57-0.73 for six portions), noncitrus fruits (OR: 0.71, 95% CI: 0.61-0.83 for six portions) and vegetables (OR: 0.51, 95% CI: 0.43-0.60 for 10 portions). A protective effect of all fruits, noncitrus fruits and vegetables was confirmed, supporting further dietary recommendations to decrease the burden of gastric cancer.

Flavonoids Regulate Inflammation and Oxidative Stress in Cancer

Cancer is the second leading cause of death globally. Millions of persons die due to cancer each year. In the last two decades, the anticancer effects of natural flavonoids have become a hot topic in many laboratories. Meanwhile, flavonoids, of which over 8000 molecules are known to date, are potential candidates for the discovery of anticancer drugs. The current review summarizes the major flavonoid classes of anticancer efficacy and discusses the potential anti-cancer mechanisms through inflammation and oxidative stress action, which were based on database and clinical studies within the past years. The results showed that flavonoids could regulate the inflammatory response and oxidative stress of tumor through some anti-inflammatory mechanisms such as NF-κB, so as to realize the anti-tumor effect.

Medicinal Chemistry Targeting Mitochondria: From New Vehicles and Pharmacophore Groups to Old Drugs with Mitochondrial Activity

Interest in tumor cell mitochondria as a pharmacological target has been rekindled in recent years. This attention is due in part to new publications documenting heterogenous characteristics of solid tumors, including anoxic and hypoxic zones that foster cellular populations with differentiating metabolic characteristics. These populations include tumor-initiating or cancer stem cells, which have a strong capacity to adapt to reduced oxygen availability, switching rapidly between glycolysis and oxidative phosphorylation as sources of energy and metabolites. Additionally, this cell subpopulation shows high chemo- and radioresistance and a high capacity for tumor repopulation. Interestingly, it has been shown that inhibiting mitochondrial function in tumor cells affects glycolysis pathways, cell bioenergy, and cell viability. Therefore, mitochondrial inhibition may be a viable strategy for eradicating cancer stem cells. In this context, medicinal chemistry research over the last decade has synthesized and characterized "vehicles" capable of transporting novel or existing pharmacophores to mitochondrial tumor cells, based on mechanisms that exploit the physicochemical properties of the vehicles and the inherent properties of the mitochondria. The pharmacophores, some of which have been isolated from plants and others, which were synthesized in the lab, are diverse in chemical nature. Some of these molecules are active, while others are prodrugs that have been evaluated alone or linked to mitochondria-targeted agents. Finally, researchers have recently described drugs with well-proven safety and efficacy that may exert a mitochondria-specific inhibitory effect in tumor cells through noncanonical mechanisms. The effectiveness of these molecules may be improved by linking them to mitochondrial carrier molecules. These promising pharmacological agents should be evaluated alone and in combination with classic chemotherapeutic drugs in clinical studies.

Apigenin and Hesperidin Downregulate DNA Repair Genes in MCF-7 Breast Cancer Cells and Augment Doxorubicin Toxicity

A number of studies have confirmed anti-tumor activity of flavonoids and their ability to enhance the effectiveness of classical anticancer drugs. The mechanism of this phenomenon is difficult to explain because of the ambivalent nature of these compounds. Many therapeutic properties of these compounds are attributed to their antioxidant activity; however, it is known that they can act as oxidants. The aim of this study was to assess the influence of apigenin and hesperidin on MCF-7 breast cancer cells with doxorubicin. The cytotoxic effect was determined using an MTT test and cell cycle analysis. To evaluate the possible interaction mechanism, reduced glutathione levels, as well as the DNA oxidative damage and the double strand breaks, were evaluated. Additionally, mRNA expression of genes related to DNA repair was assessed. It was demonstrated that flavonoids intensified the cytotoxic effect of doxorubicin despite flavonoids reduced oxidative damage caused by the drug. At the same time, the number of double strand breaks significantly increased and expression of tested genes was downregulated. In conclusion, both apigenin and hesperidin enhance the cytotoxic effects of doxorubicin on breast cancer cells, and this phenomenon occurs regardless of oxidative stress but is accompanied by disorders of DNA damage response mechanisms.

Thymoquinone inhibits the proliferation and invasion of esophageal cancer cells by disrupting the AKT/GSK-3β/Wnt signaling pathway via PTEN upregulation

Although thymoquinone (TQ) has been reported to exert antitumor activity against various types of human cancers without evident toxicity, limited studies have reported the effects of TQ on esophageal cancer. Here, we showed that TQ induced cell cycle arrest in the G2/M phase and significantly inhibited cell proliferation and invasion. Further investigation of the potential mechanism revealed that TQ increased the levels of p53 and p21 but significantly reduced the expression of Cyclin B1, Cyclin A, and Cyclin E. Moreover, TQ led to a decrease in Bcl-2 and an increase in cleaved caspase-3, cleaved caspase-7, cleaved caspase-9, and Bax, indicating that TQ induced apoptosis by activating the intrinsic mitochondrial apoptosis pathway. Western blotting showed that TQ disrupted the PI3K/AKT pathway by upregulating PTEN, thus modulating GSK-3β activity, increasing β-catenin degradation, and decreasing decreased MMP-2 and MMP-9 levels in Eca109 cells. However, these changes were attenuated by disrupting PTEN function (using a potent inhibitor) or downregulating PTEN expression. In addition, in vivo results showed that the efficacy of TQ as an antitumor agent in a mouse xenograft tumor model. In conclusion, TQ suppressed human esophageal cancer cells proliferation and invasion both in vitro and in vivo and could provide a novel therapeutic approach for esophageal cancer.

Hesperetin Promotes Cisplatin-Induced Apoptosis of Gastric Cancer In Vitro and In Vivo by Upregulating PTEN Expression

As one of the most common malignant gastrointestinal tumors, gastric cancer (GC) has a high incidence and poor prognosis. Cisplatin (DDP) is often used as chemotherapy for advanced GC; however, the high incidence of drug resistance remains a problem. The use of several anti-tumor drugs as combined chemotherapy is an effective strategy. Hesperetin has anti-tumor ability via its pro-apoptotic effect on various human cancers, both in vitro and in vivo, with no significant toxicity. However, a combination of DDP and hesperetin in GC has not been reported. The present study aimed to investigate the in vitro and in vivo chemosensitization effect and mechanism of hesperetin-augmented DDP-induced apoptosis of GC. The proliferation of GC ty -60cells was inhibited significantly in a time and dose-dependent manner by combined treatment of DDP with hesperetin. Hesperetin markedly increased DDP-induced apoptosis of GC cell lines. In a xenograft tumor mouse model, markedly better tumor suppression was observed after treatment with DDP plus hesperetin compared with that of either agent alone. Additionally, the combination of DDP and hesperetin remarkably increased the expression levels of phosphatase and tensin homolog (PTEN) and Cytochrome C (Cyt C), and significantly decreased the levels of phosphorylated protein kinase B (p-AKT) and CyclinD1. DDP and hesperetin also induced significant increases in apoptosis inducing factor (AIF), BCL2 associated X, apoptosis regulator (BAX), cleaved caspase-9, and cleaved caspase-3, and decreased B-cell lymphoma 2 (BCL2), caspase-9, and caspase-3 levels. Thus, we demonstrated that hesperetin could inhibit the phosphatidylinositol-4,5-bisphosphate 3-kinase (PI3K)/AKT signaling pathway and induce the mitochondrial pathway via upregulating PTEN expression, thereby significantly enhancing DDP’s anti-tumor effect on GC. Hesperetin is a potential chemotherapeutic agent for GC and merits further clinical investigation.

Therapeutic potential of hesperidin and its aglycone hesperetin: Cell cycle regulation and apoptosis induction in cancer models

BACKGROUND

The ability of cancer cells to divide without restriction and to escape programmed cell death is a feature of the proliferative state. Citrus flavanones are flavonoids with potential multiple anticancer actions, from antioxidant and chemopreventive, to anti-inflammatory, anti-angiogenic, cytostatic and cytotoxic in different cancer models.

PURPOSE

This review aims to summarize the current knowledge on the antiproliferative actions of the citrus flavanones hesperidin (HSD) and hesperetin (HST), with emphasis on cell cycle arrest and apoptosis.

METHODS

Cochrane Library, Scopus, Pubmed and Web of Science collection databases were queried for publications reporting antiproliferative effects of HSD and HST in cancer models.

RESULTS

HSD and HST have been proven to delay cell proliferation in several cancer models. Depending on the compound, dose and cell line studied, different effects have been reported. Cell cycle arrest associated with cytostatic effects has been reported in cells with increased levels of p53 and also cyclin-dependent kinase inhibitors, as well as decreased levels of specific cyclins and cyclin-dependent kinases. Moreover, apoptotic effects have been found to be associated with altered ratios of pro-/antiapoptotic proteins, caspase activation, c-Jun N-terminal kinase (JNK) pathway activation and caspase-independent pathways.

CONCLUSION

Available scientific literature data indicate complex effects, dependent on cell lines and exposure conditions, suggesting that HSD and HST doses need to be optimized according to the cellular and organismal context. The establishment of the main antiproliferative mechanisms is of utmost importance for a possible therapeutic benefit of citrus flavanones in the context of cancer.

Citrus Peel Flavonoids as Potential Cancer Prevention Agents

Citrus fruit and in particular flavonoid compounds from citrus peel have been identified as agents with utility in the treatment of cancer. This review provides a background and overview regarding the compounds found within citrus peel with putative anticancer potential as well as the associated in vitro and in vivo studies. Historical studies have identified a number of cellular processes that can be modulated by citrus peel flavonoids including cell proliferation, cell cycle regulation, apoptosis, metastasis, and angiogenesis. More recently, molecular studies have started to elucidate the underlying cell signaling pathways that are responsible for the flavonoids' mechanism of action. These growing data support further research into the chemopreventative potential of citrus peel extracts, and purified flavonoids in particular. This critical review highlights new research in the field and synthesizes the pathways modulated by flavonoids and other polyphenolic compounds into a generalized schema.

Bioinformatics and In Vitro Studies Reveal the Importance of p53, PPARG and Notch Signaling Pathway in Inhibition of Breast Cancer Stem Cells by Hesperetin

Purpose: The failure of chemotherapy in breast cancer is caused by breast cancer stem cells (BCSCs), a minor population of cells in bulk mammary tumors. Previously, hesperetin, a citrus flavonoid, showed cytotoxicity in several cancer cells and increased cytotoxicity of doxorubicin and cisplatin. Hesperetin also inhibited osteogenic and adipocyte differentiation, however, a study of the effect of hesperetin on BCSCs has not yet been performed.

Methods: In this study, we combined bioinformatics and in vitro works. A bioinformatic approach was performed to identify molecular targets, key proteins, and molecular mechanisms of hesperetin targeted at BCSCs, and genetic alterations among key genes. In addition, an in vitro study was carried out to measure the effects of hesperetin on BCSCs using the spheroids model of MCF-7 breast cancer cells (mammospheres).

Results: Using a bioinformatics approach, we identified P53, PPARG, and Notch signaling as potential targets of hesperetin in inhibition of BCSCs. The in vitro study showed that hesperetin exhibits cytotoxicity on mammospheres, inhibits mammosphere and colony formation, and inhibits migration. Hesperetin modulates the cell cycle and induces apoptosis in mammospheres. Moreover, hesperetin treatment modulates the expression of p53, PPARG, and NOTCH1.

Conclusion: Taken together, hesperetin has potential for the treatment of BCSC by targeting p53, PPARG and Notch signaling. Further investigation of the molecular mechanisms involved is required for the development of hesperetin as a BCSC-targeted drug.

Molecular mechanisms of action of hesperidin in cancer: Recent trends and advancements

Hesperidin belongs to flavanones class of flavonoids and is known to possess broad-spectrum applicability to prevent dreadful diseases such as cardiovascular disease, neurodegeneration, and cancer. The reported anticancer effects of hesperidin have been found to be associated with its anti-oxidant and anti-inflammatory activities. Hesperidin interacts with numerous recognized cellular targets and inhibits cancer cell proliferation by inducing apoptosis and cell cycle arrest. In addition, evidence has suggested its promising role in inhibiting tumor cell metastasis, angiogenesis, and chemoresistance. The present mini-review highlights the ongoing development to identify hesperidin targets in cancer. Furthermore, the potential of nano technology-based hesperidin combinations and delivery systems will also be discussed. Overall, this review highlights all the possible molecular targets affected by hesperidin in tumor cells on a single platform.

Impact statement

Experimental findings from numerous studies have demonstrated the anticancer effects of hesperidin (Hesp) to be associated with anti-oxidant and anti-inflammatory activities along with its potential role in inhibiting the tumor cell metastasis and angiogenesis. Additionally, Hesp can also reverse drug resistance of cancer cells, which make it a promising candidate to be used in combination with existing anti-cancer drugs. This review will be helpful for upcoming researchers and scientific community to find out complete capsular package about cancer drug targets of Hesp and its role in modulating various important hallmarks of cancer.

Flavonoids as Anticancer Agents

Flavonoids are polyphenolic compounds subdivided into 6 groups: isoflavonoids, flavanones, flavanols, flavonols, flavones and anthocyanidins found in a variety of plants. Fruits, vegetables, plant-derived beverages such as green tea, wine and cocoa-based products are the main dietary sources of flavonoids. Flavonoids have been shown to possess a wide variety of anticancer effects: they modulate reactive oxygen species (ROS)-scavenging enzyme activities, participate in arresting the cell cycle, induce apoptosis, autophagy, and suppress cancer cell proliferation and invasiveness. Flavonoids have dual action regarding ROS homeostasis—they act as antioxidants under normal conditions and are potent pro-oxidants in cancer cells triggering the apoptotic pathways and downregulating pro-inflammatory signaling pathways. This article reviews the biochemical properties and bioavailability of flavonoids, their anticancer activity and its mechanisms of action.

Hesperetin ameliorates DSS-induced colitis by maintaining the epithelial barrier via blocking RIPK3/MLKL necroptosis signaling

Hesperetin, a flavonoid from citrus fruits, possess various pharmacological properties, including anti-inflammatory, anti-oxidative, anti-tumor potentials. However, the role and its mechanism in ulcerative colitis (UC) remains unclear. This study aimed to investigate the protective effects and mechanisms of hesperetin on dextran sodium sulfate (DSS) -induced colitis. Our results showed that hesperetin significantly relieved the symptoms of DSS -induced colitis and increased the expressions of zonula occludens-1 (ZO-1), occludin and mucin2 (MUC-2) as well as the decrease of tumor necrosis factor-α (TNF-α), interleukin (IL)-1β, IL-18, HMGB1 and IL-6. Of note, results from immunohistochemistry (IHC) and western blotting indicated that hesperetin inhibited the expressions of receptor-interacting protein kinase 3 (RIPK3) and mixed lineage kinase domain-like (MLKL), the two key proteins of necroptosis pathway, and inactivated RIPK3/MLKL necroptosis signalling. Meanwhile, in the cell-coculture system between Caco-2 and RAW264.7 cells, hesperetin treatment significantly ameliorated the decrease of trans epithelial electric resistance (TEER) value while HS-173 (necroptosis inducer) could obviously influence the effect of hesperetin. In addition, hesperetin attenuated the LPS-induced increasing in 4-kDa fluorescein isothiocyanate-dextran (FD4) permeability while HS-173 could weaken the protective effect of hesperetin. Meanwhile, HS-173 reduced the changes in the expressions of phosphorylated RIPK3, phosphorylated MLKL, ZO-1, occludin and MUC-2 as well as TNF-α, IL-1β. These findings demonstrated hesperetin ameliorated DSS-induced colitis by maintaining the epithelial barrier via blocking the intestinal epithelial necroptosis.

The Role of Polyphenol (Flavonoids) Compounds in the Treatment of Cancer Cells

Cancer remains a second leading cause of deaths and major public health problem. It occurs due to extensive DNA damage caused by ultraviolet radiations, ionizing radiations, environmental agents, therapeutic agents, etc. Among all cancers, the most frequently diagnosed cancers are lung (12.7%), breast (10.9%), colorectal (9.7%), and gastric cancer (7.81%). Natural compounds are most favorable against cancer on the count of their anti-cancerous ability, easy to avail and efficient. Among natural compounds, polyphenols (flavonoids, catechin, hesperetin, flavones, quercetin, phenolic acids, ellagic acid, lignans, stilbenes, etc.) represent a large and diverse group used in the prevention and treatment of cancer. Natural flavonoids are derived from different plant sources and from various medicinal plants including Petroselinum crispum, Apium graveolens, Flemingia vestita, Phyllanthus emblica, etc. Natural flavonoids possess antioxidant, anti-inflammation, as well as anti-cancerous activities through multiple pathways, they induce apoptosis in breast, colorectal, and prostate cancers, lower the nucleoside diphosphate kinase-B activity in lung, bladder and colon cancers, inhibit cell-proliferation and cell cycle arrest by suppressing the NF-kB pathway in various cancers, etc. The current review summarized the anticancer activities of natural polyphenols and their mechanisms of action.

Combinatorial Epigenetics Impact of Polyphenols and Phytochemicals in Cancer Prevention and Therapy

Polyphenols are potent micronutrients that can be found in large quantities in various food sources and spices. These compounds, also known as phenolics due to their phenolic structure, play a vital nutrient-based role in the prevention of various diseases such as diabetes, cardiovascular diseases, neurodegenerative diseases, liver disease, and cancers. However, the function of polyphenols in disease prevention and therapy depends on their dietary consumption and biological properties. According to American Cancer Society statistics, there will be an expected rise of 23.6 million new cancer cases by 2030. Due to the severity of the increased risk, it is important to evaluate various preventive measures associated with cancer. Relatively recently, numerous studies have indicated that various dietary polyphenols and phytochemicals possess properties of modifying epigenetic mechanisms that modulate gene expression resulting in regulation of cancer. These polyphenols and phytochemicals, when administrated in a dose-dependent and combinatorial-based manner, can have an enhanced effect on epigenetic changes, which play a crucial role in cancer prevention and therapy. Hence, this review will focus on the mechanisms of combined polyphenols and phytochemicals that can impact various epigenetic modifications such as DNA methylation and histone modifications as well as regulation of non-coding miRNAs expression for treatment and prevention of various types of cancer.

Flavonoids and the Risk of Gastric Cancer: An Exploratory Case-Control Study in the MCC-Spain Study

Several epidemiological studies have investigated the association between the dietary flavonoid intake and gastric cancer (GC) risk; however, the results remain inconclusive. Investigating the relationship between the different classes of flavonoids and the histological types and origin of GC can be of interest to the research community. We used data from a population-based multi-case control study (MCC-Spain) obtained from 12 different regions of Spain. 2700 controls and 329 GC cases were included in this study. Odds ratios (ORs) were calculated using the mixed effects logistic regression considering quartiles of flavonoid intakes and log2. Flavonoid intake was associated with a lower GC risk (ORlog2 = 0.76; 95% CI = 0.65-0.89; ORq4vsq1 = 0.60; 95%CI = 0.40-0.89; ptrend = 0.007). Inverse and statistically significant associations were observed with anthocyanidins, chalcones, dihydroflavonols and flavan-3-ols. The isoflavanoid intake was positively associated with higher cancer risk, but without reaching a statistical significance. In general, no differences were observed in the GC risk according to the location and histological type. The flavonoid intake seems to be a protective factor against GC within the MCC-study. This effect may vary depending on the flavonoid class but not by the histological type and location of the tumor. Broader studies with larger sample size and greater geographical variability are necessary.

Flavonoids in Cancer and Apoptosis

Cancer is the second leading cause of death globally. Although, there are many different approaches to cancer treatment, they are often painful due to adverse side effects and are sometimes ineffective due to increasing resistance to classical anti-cancer drugs or radiation therapy. Targeting delayed/inhibited apoptosis is a major approach in cancer treatment and a highly active area of research. Plant derived natural compounds are of major interest due to their high bioavailability, safety, minimal side effects and, most importantly, cost effectiveness. Flavonoids have gained importance as anti-cancer agents and have shown great potential as cytotoxic anti-cancer agents promoting apoptosis in cancer cells. In this review, a summary of flavonoids and their effectiveness in cancer treatment targeting apoptosis has been discussed.

Hesperetin inhibits Eca-109 cell proliferation and invasion by suppressing the PI3K/AKT signaling pathway and synergistically enhances the anti-tumor effect of 5-fluorouracil on esophageal cancer in vitro and in vivo

Previously, we reported that hesperetin exhibited pro-apoptotic activity against esophageal cancer in vitro and in vivo. Here, we examined whether hesperetin inhibits cell proliferation and invasion and synergistically enhances the anti-tumor effect of 5-fluorouracil (5-FU) in esophageal cancer. Flow cytometry, EdU staining, and transwell invasion assays using Eca-109 cells showed that hesperetin induced cell cycle arrest at the G0/G1 phase and inhibited cell proliferation and invasion significantly. Moreover, hesperetin suppressed the expression of phosphorylated PI3K/AKT, cyclin D1, MMP-2, and MMP-9 and increased phosphorylated PTEN and p21 in Eca-109 cells. Hesperetin combined with 5-FU inhibited cell growth more effectively than did either drug alone in Eca-109 cells and in a xenograft mouse model. Hoechst 33258, Annexin V-PE/7-ADD double staining and TUNEL assay showed more apoptotic cells in the combination treatment group than in either individual treatment group. The combination down-regulated protein levels of Bcl-2 and up-regulated those of Bax, cleaved caspase-3, and cleaved caspase-9 more effectively than did either drug alone. These data suggest that hesperetin inhibited esophageal cancer cell proliferation and invasion by suppressing the PI3K/AKT signaling pathway. In conclusion, 5-FU and hesperetin exerted synergistic antitumor effects in vivo and in vitro and could constitute a novel therapeutic approach for esophageal cancer.

Effects of hesperetin on the proliferation and invasion of esophageal cancer cells and its synergistic anti-cancer effect with 5-FU.

The Effect of Sodium Fluoride on Cell Apoptosis and the Mechanism of Human Lung BEAS-2B Cells In Vitro

Sodium fluoride (NaF) is a source of fluoride ions used in many applications. Previous studies found that NaF suppressed the proliferation of osteoblast MC3T3 E1 cells and induced the apoptosis of chondrocytes. However, little is known about the effects of NaF on human lung BEAS-2B cells. Therefore, we investigated the mode of cell death induced by NaF and its underlying molecular mechanisms. BEAS-2B cells were treated with NaF at concentrations of 0, 0.25, 0.5, 1.0, 2.0, and 4.0 mmol/L. Cell viability decreased and apoptotic cells significantly increased as concentrations of NaF increased over specific periods of time. The IC₅₀ of NaF was 1.9 and 0.9 mM after 24 and 48 h, respectively. The rates of apoptosis increased from 4.8 to 37.7% after NaF exposure. HE staining, electron microscopy, and single cell gel electrophoresis revealed that morphological changes of apoptosis increased with exposure concentrations. RT-PCR and Western blotting were used to detect the apoptotic pathways. The expressions of bax, caspase-3, caspase-9, p53, and the cytoplasmic CytC of the NaF groups increased, while bcl-2 and mitochondrial CytC decreased compared with that of the control group (P < 0.05). Further, the fluorescence intensities of ROS in the NaF groups were higher than those in the control group, and the membrane potential of mitochondria in the NaF group was significantly lower than that of the control group (P < 0.05). These findings suggested that NaF induced apoptosis in the BEAS-2B cells through mitochondria-mediated signal pathways. Our study provides the theoretical foundation and experimental basis for exploring the mechanisms of human lung epithelial cell damage and cytotoxicity induced by fluorine.

Downregulation of TIGAR sensitizes the antitumor effect of physapubenolide through increasing intracellular ROS levels to trigger apoptosis and autophagosome formation in human breast carcinoma cells

Physapubenolide (PB) is a cytotoxic withanolide isolated from Physalis angulata that was used as a traditional Chinese medicine. In this study, we investigated the role of TIGAR and ROS in PB-induced apoptosis and autophagosome formation in human breast carcinoma MDA-MB-231 and MCF-7 cells. PB induced apoptosis by decreasing mitochondrial membrane potential and elevating the Bax/Bcl-2 protein expression ratio in MDA-MB-231 and MCF-7 cells. Caspase inhibitor Z-VAD-FMK treatment partly blocked PB induced cytotoxicity, suggesting that apoptosis serves as an important role in the anti-proliferative effect of PB. Meanwhile, PB induced autophagosome formation, as characterized by increased acridine orange-stained positive cells, accumulation of punctate LC3B fluorescence and a greater number of autophagic vacuoles under electron microscopy. Furthermore, PB inhibited autophagic flux as reflected by the overlapping of mCherry and GFP fluorescence when MDA-MB-231 cells were transfected with GFP-mCherry-LC3 plasmid. Depletion of LC3B, ATG5 or ATG7 reduced PB-induced cytotoxicity, indicating that autophagosome associated cell death participated in the anti-cancer effect of PB. Moreover, PB-induced apoptosis and autophagosome formation were linked to the generation of intracellular ROS, and pre-treatment with the antioxidant NAC obviously mitigated the effects. Interestingly, PB treatment slightly increased TIGAR expression at low concentrations but decreased TIGAR expression drastically at high concentrations. Downregulation of TIGAR by small interfering RNA augmented low concentrations of PB-induced apoptosis and autophagosome formation, which contributed to the observed anti-cancer effect of PB and were reversed by NAC pre-treatment. Consistently, in MDA-MB-231 or MCF-7 xenograft mouse model, PB suppressed tumor growth through ROS induced apoptosis and autophagosome associated cell death accompanied with the downregulation of TIGAR. Taken together, these results indicate that downregulation of TIGAR increased PB-induced apoptosis and autophagosomes associated cell death through promoting ROS generation in MDA-MB-231 and MCF-7 cells.

Polyphenolic Phytochemicals in Cancer Prevention and Therapy: Bioavailability versus Bioefficacy

Natural polyphenols are organic chemicals which contain phenol units in their structures. They show antitumor properties. However, a key problem is their short half-life and low bioavailability under in vivo conditions. Still, definitively demonstrating the human benefits of isolated polyphenolic compounds (alone or in combination) using modern scientific methodology has proved challenging. The most common discrepancy between experimental and clinical observations is the use of nonphysiologically relevant concentrations of polyphenols in mechanistic studies. Thus, it remains highly controversial how applicable underlying mechanisms are with bioavailable concentrations and biological half-life. The present Perspective analyses proposed antitumor mechanisms, in vivo reported antitumor effects, and possible mechanisms that may explain discrepancies between bioavailability and bioefficacy. Polyphenol metabolism and possible toxic side effects are also considered. Our main conclusion emphasizes that these natural molecules (and their chemical derivatives) indeed can be very useful, not only as cancer chemopreventive agents but also in oncotherapy.

Natural Polyphenols for Prevention and Treatment of Cancer

There is much epidemiological evidence that a diet rich in fruits and vegetables could lower the risk of certain cancers. The effect has been attributed, in part, to natural polyphenols. Besides, numerous studies have demonstrated that natural polyphenols could be used for the prevention and treatment of cancer. Potential mechanisms included antioxidant, anti-inflammation as well as the modulation of multiple molecular events involved in carcinogenesis. The current review summarized the anticancer efficacy of major polyphenol classes (flavonoids, phenolic acids, lignans and stilbenes) and discussed the potential mechanisms of action, which were based on epidemiological, in vitro, in vivo and clinical studies within the past five years.