Theaflavin-Containing Black Tea Extract: A Potential DNA Methyltransferase Inhibitor in Human Colon Cancer Cells and Ehrlich Ascites Carcinoma-Induced Solid Tumors in Mice

Greasing the Wheels of Pharmacotherapy for Colorectal Cancer: the Role of Natural Polyphenols

PURPOSE OF REVIEW

The main purpose of this review, mainly based on preclinical studies, is to summarize the pharmacological and biochemical evidence regarding natural polyphenols against colorectal cancer and highlight areas that require future research.

RECENT FINDINGS

Typically, colorectal cancer is a potentially preventable and curable cancer arising from benign precancerous polyps found in the colon's inner lining. Colorectal cancer is the third most common cancer, with a lifetime risk of approximately 4 to 5%. Genetic background and environmental factors play major roles in the pathogenesis of colorectal cancer. Theoretically, a multistep process of colorectal carcinogenesis provides enough time for anti-tumor pharmacotherapy of colorectal cancer. Chronic colonic inflammation, oxidative stress, and gut microbiota imbalance have been found to increase the risk for colorectal cancer development by creating genotoxic stress within the intestinal environment to generate genetic mutations and epigenetic modifications. Currently, numerous natural polyphenols have shown anti-tumor properties against colorectal cancer in preclinical research, especially in colorectal cancer cell lines. In this review, the current literature regarding the etiology and epidemiology of colorectal cancer is briefly outlined. We highlight the findings of natural polyphenols in colorectal cancer from in vitro and in vivo studies. The scarcity of human trials data undermines the clinical use of natural polyphenols as anti-colorectal cancer agents, which should be undertaken in the future.

Fresh and Browned Lotus Root Extracts Promote Cholesterol Metabolism in FFA-Induced HepG2 Cells through Different Pathways

Browning of fresh-cut plants is mainly attributed to the enzymatic browning of phenolic compounds induced by polyphenol oxidase (PPO), producing browning products such as anthraquinones, flavanol oxides, and glycosides, which are usually considered to be non-toxic. Could browning bring any benefits on behalf of their bioactivity? Our previous study found that browned lotus root extracts (BLREs) could reduce the cholesterol level in obese mice as fresh lotus root extracts (FLREs) did. This study aimed to compare the mechanisms of FLRE and BLRE on cholesterol metabolism and verify whether the main component's monomer regulates cholesterol metabolism like the extracts do through in vitro experiments. Extracts and monomeric compounds are applied to HepG2 cells induced by free fatty acids (FFA). Extracellular total cholesterol (TC) and triglyceride (TG) levels were also detected. In addition, RT-PCR and Western blot were used to observe cholesterol metabolism-related gene and protein expression. The in vitro results showed that BLRE and FLRE could reduce TC and TG levels in HepG2 cells. In addition, BLRE suppressed the synthesis of cholesterol. Meanwhile, FLRE promoted the synthesis of bile acid (BA) as well as the clearance and efflux of cholesterol. Furthermore, the main monomers of BLRE also decreased cholesterol synthesis, which is the same as BLRE. In addition, the main monomers of FLRE promoted the synthesis of BAs, similar to FLRE. BLRE and FLRE promote cholesterol metabolism by different pathways.

Polyphenols as Potent Epigenetics Agents for Cancer

Human diseases such as cancer can be caused by aberrant epigenetic regulation. Polyphenols play a major role in mammalian epigenome regulation through mechanisms and proteins that remodel chromatin. In fruits, seeds, and vegetables, as well as food supplements, polyphenols are found. Compounds such as these ones are powerful anticancer agents and antioxidants. Gallic acid, kaempferol, curcumin, quercetin, and resveratrol, among others, have potent anti-tumor effects by helping reverse epigenetic changes associated with oncogene activation and tumor suppressor gene inactivation. The role dietary polyphenols plays in restoring epigenetic alterations in cancer cells with a particular focus on DNA methylation and histone modifications was summarized. We also discussed how these natural compounds modulate gene expression at the epigenetic level and described their molecular targets in cancer. It highlights the potential of polyphenols as an alternative therapeutic approach in cancer since they modulate epigenetic activity.

Silymarin inhibits the progression of Ehrlich solid tumor via targeting molecular pathways of cell death, proliferation, angiogenesis, and metastasis in female mice

BACKGROUND

Plant-derived phytochemicals have been reported to exert anticancer activity. This study investigated the antitumor role of silymarin (Silybum marianum) (SMN) and its molecular targets in Ehrlich solid tumor xenografts in vivo.

METHODS AND RESULTS

Female Swiss albino mice were divided into three groups (of five animals each) that were engrafted with Ehrlich tumor (ET) cells with or without SMN treatment. The 3rd groups treated with DMSO only vehicle control group. A significant reduction in animal body mass and tumor volume/weight were observed in xenografted mice treated with SMN. SMN modulated oxidative stress in tumors while enhancing the antioxidant levels in mouse serum. SMN activated both mitochondrial and death receptor-related apoptosis pathways and induced cell cycle arrest, marked by a significant downregulation of cyclin D1 in SMN-treated tumors. Significant decreases in RNA content and protein expression levels of Ki-67 and proliferating cell nuclear antigen were observed in ET cells. Additionally, SMN downregulated vascular endothelial growth factor and nuclear factor-kappa B levels indicating anti-angiogenesis activity of this agent. SMN upregulated the expression of E-cadherin in tumor tissue suggesting, that SMN has potential ability to inhibit metastasis. Tumor tissue from SMN-treated animals showed a remarkable degeneration and reduction in the neoplastic cell density.

CONCLUSIONS

The anticancer effect was associated with apparent apoptosis in neoplastic cells with abundance of multifocal necrotic areas. SMN was found to inhibit ET growth via enhancing apoptosis, inhibition of cell division and reduction in angiogenesis in vivo. Hypothetical scheme of SMN antitumor effects (mechanism of signaling) in solid ET in vivo. SMN anticancer effect may be mediated by molecular mediators that affect proliferation, cell cycle activity, apoptotic pathways, angiogenesis, and metastasis.

Processing, chemical signature and food industry applications of Camellia sinensis teas: An overview

The plant Camellia sinensis is the source of different teas (white, green, yellow, oolong, black, and pu-ehr) consumed worldwide, which are classified by the oxidation degree of their bioactive compounds. The sensory (taste, aroma, and body of the drink) and functional properties of teas are affected by the amount of methylxanthines (caffeine and theobromine), amino acids (l-theanine) and reducing sugars in their composition. Additionally, flavan-3-ols, mainly characterized by epicatechins, catechins, and their derivatives, represent on average, 60% of the bioactive compounds in teas. These secondary metabolites from teas are widely recognized for their antioxidant, anti-cancer, and anti-inflammatory properties. Thus, Camellia sinensis extracts and their isolated compounds have been increasingly used by the food industry. However, bioactive compounds are very susceptible to the oxidation caused by processing and degradation under physiological conditions of gastrointestinal digestion. In this context, new approaches/technologies have been developed for the preservation of these compounds. This review presents the main stages involved in production of Camellia sinensis teas following a description of their main bioactive compounds, biological properties, stability and bioaccessibility. Besides, and updated view of Camellia sinensis teas in the field of food science and technology was provided by focusing on novel findings and innovations published in scientific literature over the last five years.

Anticancer Effects and Molecular Target of Theaflavins from Black Tea Fermentation in Vitro and in Vivo

Black tea is one of the most popular beverages in the world, and numerous epidemiological studies have shown that drinking black tea is good for health. As a natural tea pigment formed during the fermentation of black tea, the content of theaflavins accounts for only 2-6% of the dry weight of black tea, but they have a great impact on the color and taste of black tea soup. Recently, a large number of studies have shown that theaflavins have a significant anticancer effect. In this Perspective, we first state the physical and chemical properties, separation and purification methods, and biological formation pathways of theaflavins and analyze their safety and oral bioavailability and the structure-activity relationship of their antioxidant and anticancer activities; then, we describe in detail their anticancer effect in vitro and in vivo and highlight their various molecular targets involved in cancer inhibition. The anticancer molecular targets of theaflavins are mainly cell-cycle regulatory proteins, apoptosis-related proteins, cell-migration-related proteins, and growth transcription factors. Finally, the possibility of developing new health-care food based on theaflavins is discussed. This Perspective is expected to provide a theoretical basis for the anticancer application of theaflavins in the future.

Mesenchymal Stem Cell-derived Extracellular Vesicles Transmitting MicroRNA-34a-5p Suppress Tumorigenesis of Colorectal Cancer Through c-MYC/DNMT3a/PTEN Axis

Mesenchymal stem cell–derived extracellular vesicles (MSC-EV) can transport microRNAs (miRNAs) into colorectal cancer (CRC) cells, thus to inhibit the malignant phenotype of cancer cells. Whether MSC-EV could deliver miR-34a-5p to suppress CRC development was surveyed through the research. miR-34a-5p, c-MYC, DNA methyltransferase 3a (DNMT3a), and phosphatase and tensin homolog deleted on chromosome 10 (PTEN) expression were measured in CRC tissues and cell lines. miR-34a-5p and c-MYC expression were altered by transfection in HCT-116 cells. MSC-EV were transfected with miR-34a-5p- and c-MYC-related oligonucleotides and co-cultured with HCT-116 cells. HCT-116 cell growth after treatment was observed. Furthermore, the functional roles of miR-34a-5p and c-MYC were explored in vivo. The combined interactions of miR-34a-5p/c-MYC/DNMT3a/PTEN axis were assessed. miR-34a-5p and PTEN were downregulated while c-MYC and DNMT3a were upregulated in CRC. Depletion of miR-34a-5p drove while that of c-MYC restricted CRC cell growth. MSC-EV retarded CRC progression. Moreover, MSC-EV carrying overexpressed miR-34a-5p or depleted c-MYC further disrupted CRC cell progression. miR-34a-5p targeted c-MYC to regulate DNMT3a and PTEN. c-MYC overexpression abrogated EV-derived miR-34a-5p upregulation-induced effects on CRC. Restoring miR-34a-5p or depleting c-MYC in MSC-EV limited CRC tumor formation. MSC-EV-derived miR-34a-5p depresses CRC development through modulating the binding of c-MYC to DNMT3a and epigenetically regulating PTEN.

Remodeling the Epigenetic Landscape of Cancer-Application Potential of Flavonoids in the Prevention and Treatment of Cancer

Epigenetics, including DNA methylation, histone modification, and noncoding RNA regulation, are physiological regulatory changes that affect gene expression without modifying the DNA sequence. Although epigenetic disorders are considered a sign of cell carcinogenesis and malignant events that affect tumor progression and drug resistance, in view of the reversible nature of epigenetic modifications, clinicians believe that associated mechanisms can be a key target for cancer prevention and treatment. In contrast, epidemiological and preclinical studies indicated that the epigenome is constantly reprogrammed by intake of natural organic compounds and the environment, suggesting the possibility of utilizing natural compounds to influence epigenetics in cancer therapy. Flavonoids, although not synthesized in the human body, can be consumed daily and are common in medicinal plants, vegetables, fruits, and tea. Recently, numerous reports provided evidence for the regulation of cancer epigenetics by flavonoids. Considering their origin in natural and food sources, few side effects, and remarkable biological activity, the epigenetic antitumor effects of flavonoids warrant further investigation. In this article, we summarized and analyzed the multi-dimensional epigenetic effects of all 6 subtypes of flavonoids (including flavonols, flavones, isoflavones, flavanones, flavanols, and anthocyanidin) in different cancer types. Additionally, our report also provides new insights and a promising direction for future research and development of flavonoids in tumor prevention and treatment via epigenetic modification, in order to realize their potential as cancer therapeutic agents.

Anti-Proliferative, Pro-Apoptotic, Anti-Migrative and Tumor-Inhibitory Effects and Pleiotropic Mechanism of Theaflavin on B16F10 Melanoma Cells

Purpose

Theaflavin (TF) is a primary pigment of tea, exhibiting anti-proliferative, pro-apoptotic and anti-metastatic activities on cancer cell lines. However, it is unknown whether TF is effective in treating melanoma cells.

Methods

To determine the effects of TF on melanoma cells, we conducted in vitro assays of cell viability, DAPI staining, wound healing, transwell, and flow cytometry as well as in vivo experiments on B16F10-bearing mouse model. Real-time PCR (qPCR) and Western blot (WB) were conducted to explore the molecular actions of TF.

Results

The cell viability assay showed that TF exerted inhibitory effect on B16F10 cells in a dose-dependent manner from 40 to 400 μg/mL, with IC₅₀ values ranging from 223.8±7.1 to 103.7±7.0 μg/mL. Moreover, TF induced early and late apoptosis and inhibited migration/invasion of B16F10 cells in a dose-dependent manner, indicating its pro-apoptotic and anti-migrative effects. In vivo, TF significantly inhibited B16F10 tumor size in mice model from 40 to 120 mg/kg, which exerted higher effect than that of cisplatin. The molecular data showed that TF significantly up-regulated the mRNA expressions of pro-apoptotic genes (Bax, Casp3, Casp8, c-fos, c-Jun, and c-Myc), up-regulated the protein expressions of apoptosis-related p53 and JNK signaling molecules (ASK1, phosphorylated Chk1/2, cleaved caspase 3, phosphorylated JNK, c-JUN, cleaved PARP, and phosphorylated p53), and down-regulated the protein expressions of proliferation-related MEK/ERK and PI3K/AKT signaling molecules (phosphorylated MEK1/2, phosphorylated ERK1/2, phosphorylated PI3K, and phosphorylated AKT) as well as the expressions of MMP2 and MMP9.

Conclusion

It can be concluded that TB exhibited anti-proliferative, pro-apoptotic, anti-migrative, and tumor-inhibitory effects on melanoma cells through pleiotropic actions on the above pathways. This study provides new evidence of anti-melanoma efficacy and mechanism of TF, contributing to the development of TF-derived natural products for melanoma therapy.

Anti-Cancer Properties of Theaflavins

Cancer is a disease characterized by aberrant proliferative and apoptotic signaling pathways, leading to uncontrolled proliferation of cancer cells combined with enhanced survival and evasion of cell death. Current treatment strategies are sometimes ineffective in eradicating more aggressive, metastatic forms of cancer, indicating the need to develop novel therapeutics targeting signaling pathways which are essential for cancer progression. Historically, plant-derived compounds have been utilized in the production of pharmaceuticals and chemotherapeutic compounds for the treatment of cancer, including paclitaxel and docetaxel. Theaflavins, phenolic components present in black tea, have demonstrated anti-cancer potential in cell cultures in vitro and in animal studies in vivo. Theaflavins have been shown to inhibit proliferation, survival, and migration of many cancer cellswhile promoting apoptosis. Treatment with theaflavins has been associated with increased levels of cleaved poly (ADP-ribose) polymerase (PARP) and cleaved caspases-3, -7, -8, and -9, all markers of apoptosis, and increased expression of the proapoptotic marker Bcl-2-associated X protein (Bax) and concomitant reduction in the antiapoptotic marker B-cell lymphoma 2 (Bcl-2). Additionally, theaflavin treatment reduced phosphorylated Akt, phosphorylated mechanistic target of rapamycin (mTOR), phosphatidylinositol 3-kinase (PI3K), and c-Myc levels with increased expression of the tumour suppressor p53. This review summarizes the current in vitro and in vivo evidence available investigating the anti-cancer effects of theaflavins across various cancer cell lines and animal models.