Effects of Tea Polyphenols and their Polymers on MAPK Signaling Pathways in Cancer Research

Tea Polyphenols as Prospective Natural Attenuators of Brain Aging

No organism can avoid the process of aging, which is often accompanied by chronic disease. The process of biological aging is driven by a series of interrelated mechanisms through different signal pathways, including oxidative stress, inflammatory states, autophagy and others. In addition, the intestinal microbiota play a key role in regulating oxidative stress of microglia, maintaining homeostasis of microglia and alleviating age-related diseases. Tea polyphenols can effectively regulate the composition of the intestinal microbiota. In recent years, the potential anti-aging benefits of tea polyphenols have attracted increasing attention because they can inhibit neuroinflammation and prevent degenerative effects in the brain. The interaction between human neurological function and the gut microbiota suggests that intervention with tea polyphenols is a possible way to alleviate brain-aging. Studies have been undertaken into the possible mechanisms underpinning the preventative effect of tea polyphenols on brain-aging mediated by the intestinal microbiota. Tea polyphenols may be regarded as potential neuroprotective substances which can act with high efficiency and low toxicity.

Natural Polyphenols as Targeted Modulators in Colon Cancer: Molecular Mechanisms and Applications

Colon cancer commonly develops from long-term chronic inflammation in the intestine and seriously threatens human health. Natural polyphenols have been valued as a crucial regulator of nutrient metabolism and metabolic diseases, owing to their anti-inflammatory and antioxidant functions and the ability to maintain a balance between gut microbes and their hosts. Notably, experimental and clinical evidence has shown that natural polyphenols could act as a targeted modulator to play a key role in the prevention or treatment of colon cancer. Thus, in this review, we summarized recent advances in the possible regulatory mechanism and the potential application of natural polyphenols in colon cancer, which might be regarded as a novel platform for the colon cancer management.

Morin Inhibits Proliferation, Migration, and Invasion of Bladder Cancer EJ Cells via Modulation of Signaling Pathways, Cell Cycle Regulators, and Transcription Factor-Mediated MMP-9 Expression

Preclinical Research Previous studies have shown that morin exerts diverse pharmacological activities. In this study, we investigated the inhibitory activity of morin on bladder cancer EJ cells. Morin significantly inhibited EJ cell proliferation, which was related to the G1-phase cell cycle arrest together with the reduced expression of cyclin D1, cyclin E, CDK2, and CDK4 via increased expression of p21WAF1. Morin also increased ERK1/2 phosphorylation and decreased JNK and AKT phosphorylation without altering the p38MAPK phosphorylation levels. Morin treatment suppressed the migration and invasion of EJ cells in wound-healing and transwell cell invasion assays. Zymographic and electrophoretic mobility shift assays showed that morin suppressed the expression of matrix metalloproteinase-9 (MMP-9) via repression of the binding activity of AP-1, Sp-1, and NF-κB. Collectively, these results demonstrate that morin reduced cyclin D1, cyclin E, CDK2 and CDK4 expression via the induction of p21WAF1 expression, increased ERK1/2 phosphorylation and decreased JNK, and AKT phosphorylation, and prevented MMP-9 expression via the inhibition of transcription factors AP-1, Sp-1, and NF-κB, thereby resulting in the inhibition of growth, migration, and invasion of bladder cancer EJ cells. These results provide a novel insight into the use of morin in the prevention of bladder cancer. Drug Dev Res 78 : 81-90, 2017. © 2017 Wiley Periodicals, Inc.

Marsdenia tenacissima extract induces G0/G1 cell cycle arrest in human esophageal carcinoma cells by inhibiting mitogen-activated protein kinase (MAPK) signaling pathway

Marsdenia tenacissima extract (MTE, trade name: Xiao-Ai-Ping injection) is an extract of a single Chinese plant medicine. It has been used for the treatment of cancer in China for decades, especially for esophageal cancer and other cancers in the digestive tract. In the present study, the potential mechanism for MTE's activity in esophageal cancer was explored. The effects of MTE on the proliferation of human esophageal cancer cells (KYSE150 and Eca-109) were investigated by the MTT assay, the BrdU (bromodeoxyuridine) incorporation immunofluorescence assay, and flow cytometric analysis. MTE inhibited cell proliferation through inducing G0/G1 cell cycle arrest in KYSE150 and Eca-109. Western blot analysis was employed to determine protein levels in the MTE treated cells. Compared with the control cells, the expression levels of the cell cycle regulatory proteins cyclin D1/D2/D3, cyclin E1, CDK2/4/6 (CDK: cyclin dependent kinase), and p-Rb were decreased significantly in the cells treated with MTE at 40 mg·mL(-1). In addition, MTE had an inhibitory effect on the MAPK (mitogen-activated protein kinase) signal transduction pathway, including ERK (extracellular signal-regulated kinase), JNK (c-Jun N-terminal kinase), and p38MAPK. Moreover, MTE showed little additional effects on the regulation of cyclin D1/D3, CDK4/6, and p-Rb when the ERK pathway was already inhibited by the specific ERK inhibitor U0126. In conclusion, these data suggest that MTE inhibits human esophageal cancer cell proliferation through regulation of cell cycle regulatory proteins and the MAPK signaling pathways, which is probably mediated by the inhibition of ERK activation.

A synthesized nostocionone derivative potentiates programmed cell death in human T-cell leukemia Jurkat cells through mitochondria via the release of endonuclease G

Nostocionone (Nost), a compound isolated from Nostoc commune, and its synthesized derivatives (NostDs) were evaluated for in vitro cytotoxicity against human T-cell leukemia Jurkat cells. NostD3 [(1E,4E)-1-(3,4-dihydroxyphenyl)-5-(2,6,6-trimethylcyclohex-1-enyl)penta-1,4-dien-3-one] inhibited cell growth more potently than Nost. To elucidate the mechanisms of NostD3-induced cell death, we examined changes in cell morphology, the loss of mitochondrial membrane potential (MMT), and DNA fragmentation. From these results, the cytotoxic effects of NostD3 were found to be mainly due to Type I programmed cell death (PCDI; i.e., apoptosis). Using caspase inhibitors, we further found that NostD-3-induced PCDI occurred through a caspase-independent pathway. Moreover, NostD3 decreased MMT and modulated multiple signaling molecules (MAPKs, Akt, Bcl-2, Bax, and c-Myc) in Jurkat cells, thereby inducing the release of endonuclease G (Endo-G) from mitochondria. The level of intracellular reactive oxygen species (ROS) in cells treated with NostD3 was elevated up to 1 h after the treatment. However, suppression of ROS by N-acetyl-l-cysteine restored Jurkat cell growth. Taken together, our data suggested that ROS production acted as a trigger in NostD3-induced PCDI in Jurkat cells through release of Endo-G from the mitochondria.

HSF1 and Sp1 regulate FUT4 gene expression and cell proliferation in breast cancer cells

Lewis Y (LeY) is a carbohydrate tumor-associated antigen. The majority of cancer cells derived from epithelial tissues express LeY type difucosylated oligosaccharides. Fucosyltransferase IV (FUT4) is an essential enzyme that catalyzes the synthesis of LeY oligosaccharides. In a previous study we reported that FUT4 is associated with cell proliferation; however, despite the important role of FUT4 in cancer proliferation and apoptosis, little is known about the mechanisms underlying the regulation of FUT4 transcription. In the current study we investigated the regulation of FUT4 transcription in human breast cancer. We compared the regulation of human FUT4 gene transcription in human breast cancer cells (MCF-7 and MDA-MB-231) using promoter/luciferase analyses. Using a series of promoter deletion constructs, we identified a potential regulatory site located between 0.8 and 1.6 kb of the FUT4 promoter. As shown by EMSA and ChIP analyses, heat-shock factor 1 (HSF1) and Sp1are required for FUT4 promoter activity. In addition, we explored the role of HSF1 and Sp1 on cell proliferation, and found that the ERK1/2 MAPK and PI3K/Akt signaling pathways regulate the expression of FUT4, which play a role in cell proliferation via HSF1 and Sp1. These results suggest that FUT4 is a target gene for HSF1 and Sp1 that is required for cell cycle progression in breast cancer epithelial cells.

Cellular targets for the beneficial actions of tea polyphenols

Green and black teas contain different biologically active polyphenolic compounds that might offer protection against a variety of human diseases. Although promising experimental and clinical data have shown protective effects, limited information is available on how these beneficial effects of tea polyphenols are mediated at the cellular level. Evidence is accumulating that catechins in green tea as well as theaflavins and thearubigins from black tea are the substances responsible for the physiologic effects of tea in vitro. The green tea catechin epigallocatechin-3-gallate (EGCG) is generally considered to be the biologically most active compound in vitro. The changes in the activities of various protein kinases, growth factors, and transcription factors represent a common mechanism involved in cellular effects of tea polyphenols. In addition to modification of intracellular signaling by activation of cellular receptors, it was shown that, at least for EGCG, tea polyphenols can enter the cells and directly interact with their molecular targets within cells. There, they frequently result in opposite effects in primary compared with tumor cells. Although tea polyphenols were long regarded as antioxidants, research in recent years has uncovered their prooxidant properties. The use of high nonphysiologic concentrations in many cell culture studies raises questions about the biological relevance of the observed effects for the in vivo situation. Efforts to attribute functional effects in vivo to specific molecular targets at the cellular level are still ongoing.

Enhancement of (-)-epigallocatechin-3-gallate and theaflavin-3-3'-digallate induced apoptosis by ascorbic acid in human lung adenocarcinoma SPC-A-1 cells and esophageal carcinoma Eca-109 cells via MAPK pathways

Tea polyphenols (-)-epigallocatechin-3-gallate (EGCG) and theaflavin-3-3'-digallate (TF3) are two prospective compounds in cancer prevention and treatment. Ascorbic acid (Vc) is essential to a healthy diet as well as being a highly effective antioxidant. In this work, the effects of the combination of EGCG or TF3 with Vc on the apoptosis and caspases-3/9 activities in human lung adenocarcinoma SPC-A-1 cells and esophageal carcinoma Eca-109 cells were determined. Furthermore, the role of mitogen-activated protein kinases (MAPK) pathways in the apoptosis induced by TF3 or EGCG together with Vc were studied using three MAPK inhibitors (ERK inhibitor PD98059, JNK inhibitor SP600125 and p38 inhibitor SB203580). Our results showed that Vc could enhance the EGCG and TF3 induced apoptosis in SPC-A-1 and Eca-109 cells, and this effect involved the activation of caspase-3 and 9. EGCG, TF3 and Vc could activate MAPK pathways respectively, and each compound activated different MAPK subfamilies in different cells. This may explain the enhancement of EGCG and TF3 induced apoptosis by Vc in SPC-A-1 and Eca-109 cells, and will ultimately aid the design of more effective anti-cancer treatments.

β-Ionone arrests cell cycle of gastric carcinoma cancer cells by a MAPK pathway

β-Ionone is an end ring analog of β-carotenoid which has been shown to possess potent anti-proliferative activity both in vitro and in vivo. To investigate the possible inhibitory effects of β-ionone, we studied cell growth characteristics, DNA synthesis, cell cycle progression, as well as mitogen-activated protein kinases (MAPKs) pathways in the human gastric adenocarcinoma cancer cell line (SGC-7901). Our results show that cell growth and DNA synthesis were inhibited, and the cell cycle was arrested at the G0/G1 phase in a dose-dependent manner in cells treated with β-ionone (25, 50, 100 and 200 μmol/L) for 24 h. We found that the β-ionone significantly decreased the extracellular signal-regulated kinase protein expression and significantly increased the levels of p38 and Jun-amino-terminal kinase protein expression (P < 0.01). β-Ionone also inhibited cell cycle-related proteins of Cdk4, Cyclin B1, D1 and increased p27 protein expression in SGC-7901 cells. These results suggested that the cell cycle arrest observed may be regulated through a MAPK pathway by transcriptional down-regulation of cell cycle proteins. These results demonstrate potent ability of β-ionone to arrest cell cycle of SGC-7901 cells and decrease proliferation.

A fluorescence-based assay for p38α recruitment site binders: identification of rooperol as a novel p38α kinase inhibitor

A new p38α inhibitor: Using a D-recruitment site (DRS) probe for p38α which exploits covalent interaction with Cys119 and alkyne-azide "click" chemistry to identify small molecules that recognize the p38α DRS, the anti-inflammatory natural product rooperol was identified as a novel p38α inhibitor.