Comparative examination of anti-proliferative activities of (-)-epigallocatechin gallate and (--)-epigallocatechin against HCT116 colorectal carcinoma cells

Inhibition and potential treatment of colorectal cancer by natural compounds via various signaling pathways

Colorectal cancer (CRC) is a common type of malignant digestive tract tumor with a high incidence rate worldwide. Currently, the clinical treatment of CRC predominantly include surgical resection, postoperative chemotherapy, and radiotherapy. However, these treatments contain severe limitations such as drug side effects, the risk of recurrence and drug resistance. Some natural compounds found in plants, fungi, marine animals, and bacteria have been shown to inhibit the occurrence and development of CRC. Although the explicit molecular mechanisms underlying the therapeutic effects of these compounds on CRC are not clear, classical signaling transduction pathways such as NF-kB and Wnt/β-catenin are extensively regulated. In this review, we have summarized the specific mechanisms regulating the inhibition and development of CRC by various types of natural compounds through nine signaling pathways, and explored the potential therapeutic values of these natural compounds in the clinical treatment of CRC.

Preclinical Pharmacological Activities of Epigallocatechin-3-gallate in Signaling Pathways: An Update on Cancer

Epigallocatechin gallate (EGCG) is the main bioactive component of catechins predominantly present in svarious types of teas. EGCG is well known for a wide spectrum of biological activity as an anti-oxidative, anti-inflammatory, and anti-tumor agent. The effect of EGCG on cell death mechanisms via the induction of apoptosis, necrosis, and autophagy has been documented. Moreover, its anti-proliferative and chemopreventive action has been demonstrated in many cancer cell lines. It was also involved in the modulation of cyclooxygenase-2, in oxidative stress and inflammation of different cell processes. EGCG has been reported as a promising target for plasma membrane proteins, such as epidermal growth factor receptor (EGFR). In addition, it has been demonstrated a mechanism of action relying on the inhibition of ERK1/2, p38 MAPK, NF-κB, and vascular endothelial growth factor (VEGF). EGCG and its derivatives were used in proteasome inhibition and they were involved in epigenetic mechanisms. In summary, EGCG is the most predominant and bioactive constituent of teas and it has a pivotal role in cancer prevention. Its preclinical pharmacological activities are associated with complex molecular mechanisms that involve numerous signaling pathways.

Antiproliferative and cytotoxic effects of grape pomace and grape seed extracts on colorectal cancer cell lines

Grape pomace is the source of bioactive compounds (anthocyanins, flavonols, flavan-3-ols, and stilbenes) which exhibit antiproliferative actions on cell cultures. We have investigated the antitumoral effects of grape pomace and grape seed extracts on colon cancer cells (Caco-2, HT-29) and fibroblasts. Crude extracts prepared from white and red pomace, and grape seeds, reduced the viability and proliferation of Caco-2. HT-29 cells were resistant to these actions. Purified extracts were then prepared from the same sources and compared with the LDH test; again, all three extracts were active and purified extract from grape seed was the most potent and specific on Caco-2 cells. HT-29 cells were more sensitive to these purified extracts. The biological activity resided almost exclusively in the flavonol and flavan-3-ols subfractions, rather than the anthocyanin subfraction. Preliminary results on the mechanisms involved in these effects revealed downregulation of Myc gene expression in HT-29 and upregulation of Ptg2 in Caco-2 cells.

Antiproliferative and Apoptotic Activity of Chamaecyparis obtusa Leaf Extract against the HCT116 Human Colorectal Cancer Cell Line and Investigation of the Bioactive Compound by Gas Chromatography-Mass Spectrometry-Based Metabolomics

Chamaecyparis obtusa (CO) belongs to the Cupressaceae family, and it is found widely distributed in Japan and Korea. In this study, the anti-proliferative activities of the methanol and water extracts of CO leaves against a human colorectal cancer cell line (HCT116) were investigated. The methanol extract of CO leaves, at a concentration of 1.25 µg/mL, exhibited anti-proliferative activity against HCT116 cells, while displaying no cytotoxicity against Chang liver cells. Comparative global metabolite profiling was performed using gas chromatography-mass spectrometry coupled with multivariate statistical analysis, and it was revealed that anthricin was the major compound contributing to the anti-proliferative activity. The activation of c-Jun N-terminal kinases played a key role in the apoptotic effect of the methanol extract of CO leaves in HCT116 human colon cancer cells. These results suggest that the methanol extract and anthricin derived from CO leaves might be useful in the development of medicines with anti-colorectal cancer activity.

Schedule-Dependent Effect of Epigallocatechin-3-Gallate (EGCG) with Paclitaxel on H460 Cells

Background

Epigallocatechin-3-gallate (EGCG), a major biologically active component of green tea, has anti-cancer activity in human and animal models. We investigated the schedule-dependent effect of EGCG and paclitaxel on growth of NCI-H460 non-small cell lung cancer cells.

Methods

To investigate the combined effect of EGCG (E) and paclitaxel (P), combination indices (CIs) were calculated, and cell cycle analysis was performed. For the effect on cell apoptosis, western blot analysis was also performed.

Results

CI analysis demonstrated that both concurrent and sequential E → P treatments had antagonistic effects (CIs >1.0), but sequential P → E had synergistic effects (CIs <1.0), on the growth inhibition of NCI-H460 cells. In the cell cycle analysis, although paclitaxel induced G₂/M cell cycle arrest and increased the sub-G1 fraction, concurrent EGCG and paclitaxel treatments did not have any additive or synergistic effects compared with the paclitaxel treatment alone. However, western blot analysis demonstrated that sequential P → E treatment decreased the expression of Bcl-2 and procaspase-3 and increased poly(ADP-ribose) polymerase (PARP) cleavage; while minimal effects were seen with concurrent or sequential E → P treatments.

Conclusion

Concurrent or sequential E → P treatment had opposite effects to P → E treatment, where P → E treatment showed a synergistic effect on growth inhibition of NCI-H460 cells by inducing apoptosis. Thus, the efficacy of EGCG and paclitaxel combination treatment seems to be schedule-dependent.

Epicatechin gallate induces cell death via p53 activation and stimulation of p38 and JNK in human colon cancer SW480 cells

The tea flavonoid epicatechin gallate (ECG) exhibits a wide range of biological activities. In this study, the in vitro anticancer effects of ECG on SW480 colon cancer cell line was investigated by analyzing the cell cycle, apoptosis, key proteins involved in cellular survival/proliferation, namely AKT/phosphatidylinositol-3-kinase (PI3K) and mitogen-activated protein kinases (MAPKs), and the role of p53 in these processes. ECG induced cell cycle arrest at the G0/G1-S phase border associated with the stimulation of p21, p-p53, and p53 and the suppression of cyclins D1 and B1. Exposure of SW480 cells to ECG also led to apoptosis as determined by time-dependent changes in caspase-3 activity, MAPKs [extracellular regulated kinase (ERK), p38, and c-jun amino-terminal kinase (JNK)], p21 and p53 activation, and AKT inhibition. The presence of pifithrin, an inhibitor of p53 function, blocked ECG-induced apoptosis as was manifested by restored cell viability and caspase-3 activity to control values and reestablished the balance among Bcl-2 anti- and proapoptotic protein levels. Interestingly, ECG also inhibited p53 protein and RNA degradation, contributing to the stabilization of p53. In addition, JNK and p38 have been identified as necessary for ECG-induced apoptosis, upon activation by p53. The results suggest that the activation of the p53-p38/JNK cascade is required for ECG-induced cell death in SW480 cells.

Epigallocatechin-3-gallate inhibits cell growth, induces apoptosis and causes S phase arrest in hepatocellular carcinoma by suppressing the AKT pathway

Epigallocatechin-3-gallate (EGCG) has been shown to inhibit the growth and induce apoptosis of certain cancer cells. The aim of this study was to determine the role of EGCG in hepatocellular carcinoma (HCC) and the underlying mechanism(s) thereof. MTT assay was used to determine the cell growth inhibition by EGCG. Apoptosis induced by EGCG was investigated by both AO/EB staining and flow cytometry. The cell cycle distribution was analyzed by flow cytometry. The mRNA levels of the AKT pathway were analyzed by quantitative PCR. The expression of AKT and its phosphorylation at Ser473 were detected by western blotting. The IC50 of EGCG at 48 h for HepG2, SMMC7721 and SK-hep1 cells were 74.7, 59.6 and 61.3 µg/ml, respectively. Significantly higher proportion of SMMC7721 cells entered the S phase upon treatment with EGCG for 48 h compared with control cells. EGCG decreased the mRNA levels of PI3K, AKT and NF-κB. The protein levels of AKT decreased and its phosphorylation at Ser473 was downregulated with EGCG treatment. EGCG inhibited growth by affecting the cell cycle and induced apoptosis in different HCC cells by downregulating PI3K/AKT activity. The results suggest the potential of EGCG as an anticancer agent in the prevention or treatment of HCC.

Impact of antioxidants on the ability of phenolic phytochemicals to kill HCT116 colon cancer cells

Certain phenolic phytochemicals can kill cancer cells. Possible interference from antioxidants is a concern, and this issue has not been studied appreciably. Therefore, the effect of ascorbate and N-acetylcysteine on the ability of epigallocatechin gallate (EGCG) and curcumin to kill HCT116 colon cancer cells was examined. EGCG and curcumin each caused DNA damage in the cells. The DNA-damaging ability of EGCG, but not curcumin, was hindered by either ascorbate or NAC, which was also shown in HT29 and SW480 colon cancer cells. Also, iron chelators (deferoxamine and 2,2'-dipyridyl) inhibited the ability of EGCG, but not curcumin, to cause damage to the DNA in HCT116 cells. Interestingly, curcumin, but not EGCG, increased the expression of growth arrest and DNA damage-inducible gene 153 and also heme oxygenase-1, and this stress gene upregulation by curcumin was antioxidant-insensitive. With prolonged incubation of HCT116 cells with either EGCG or curcumin, cell shrinkage, membrane blebbing, apoptotic bodies, and chromatin condensation/fragmentation were observed. These morphological changes were not apparent in EGCG-treated cells that had been pretreated with either ascorbate or NAC. However, the ascorbate and NAC pretreatments did not prevent the occurrence of the morphological changes in curcumin-treated cells. Thus, these findings suggest that ascorbate and NAC interfere with the ability of EGCG, but not curcumin, to kill HCT116 cells. This basic knowledge may help to better plan and optimize strategies for chemoprevention or chemotherapy.

Complexing of Green Tea Catechins with Food Constituents and Degradation of the Complexes by Lactobacillus plantarum

Complexing of green tea catechins with food constituents and their hydrolysis by tannase-producing Lactobacillus plantarum strains, were investigated. Our observations indicated that 1) epigallocatechin gallate (EGCg) and other catechin galloyl esters bound with food ingredients (i.e., proteins) to form a complex that is likely to be unabsorbable through the intestinal wall, whereas most catechins not esterified with gallic acid (GA) remain in free form, not complexing with food ingredients; 2) tannase activity of L. plantarum is strain dependent, possibly grouped into those with high tannase activity hydrolyzing EGCg to epigallocatechin and GA and those with the low activity; and 3) L. plantarum strains with high tannase activity are capable of hydrolyzing not only intact EGCg but also EGCg and other catechin galloyl esters complexed with dietary proteins to free non-galloyl ester catechins and GA. The evidence suggests that L. plantarum with high tannase activity, if it colonizes the human intestine, would release free non-galloyl-ester catechins and GA that are readily absorbed through the human intestinal epithelia from the complexes, thereby ensuring maximum delivery of the bioactive polyphenols of green tea to the host.

(-)-Epigallocatechin-3-gallate, a green tea-derived catechin, synergizes with celecoxib to inhibit IL-1-induced tumorigenic mediators by human pancreatic adenocarcinoma cells Colo357

Despite their toxic side effects prostaglandin H(2) synthase-2 (PGHS-2) inhibitors hold promise for cancer chemoprevention. In order to overcome adverse effects lower doses of PGHS-2 inhibitors could be applied in combination with other agents exhibiting complementary effects. Herein, the effects of the PGHS-2-specific inhibitor celecoxib either alone or in combination with the green tea-derived catechin (-)-epigallocatechin-3-gallate (EGCG) were studied on the expression of interleukin (IL)-1-induced tumorigenic factors in Colo357 human pancreatic adenocarcinoma cells. This approach mimics tumor-associated pancreatic inflammation which is considered as a key player in pancreatic malignancy. We found that co-incubation of Colo357 with celecoxib and EGCG synergistically diminished metabolic activity via apoptosis induction and down-regulated release of pro-angiogenic vascular endothelial growth factor (VEGF) and invasiveness-promoting matrix metalloproteinase (MMP)-2 to a maximum of 30%. Celecoxib and EGCG synergistically reduced IL-1-induced production of pro-inflammatory IL-6 and pro-angiogenic IL-8 to 23-50%. Celecoxib dose-dependently increased PGHS-2 levels. Whereas EGCG was able to compensate for celecoxib-mediated increase of PGHS-2, it failed to potentiate celecoxib-mediated suppression of prostaglandin E(2) (PGE(2)) release. Thus, in Colo357, EGCG synergistically boosts celecoxib-mediated effects and reduces the levels of celecoxib required to elicit beneficial effects on tumorigenic mediators by a factor of ten.

Cytotoxic oleane-type triterpene saponins from Glochidion eriocarpum

The anticancer activity of ten compounds from the aerial parts of Glochidion eriocarpum were evaluated on two human cancer cell lines, HL-60 and HCT-116. Compounds 1-4 displayed highly potent cytotoxic activity on the HCT-116 cancer cell line with IC(50) values ranging of 0.41∼1.16 μM. Compounds 1-4 significantly inhibited the HL-60 cell line with IC(50) values ranging of 4.51∼6.33 μM. These results suggested that the benzoyl group at the C-22 position in oleane-type triterpene saponins was essential for cytotoxicity towards tumor cells. Moreover, compounds 2 and 3 showed more potent cytotoxicity than compounds 1 and 4 against HL-60 and HCT-116 cells. With respect to the mechanism underlying cytotoxicity, compounds 1-4 increased chromatin condensation, a typical apoptotic characteristic in HL-60 and HCT-116 cells. In the mechanism of apoptosis induction, compounds 1-4 reduced Bcl-2 expression, whereas the expression of Bax was increased compared to controls in HCT-116 cells. In addition, compounds 1-4 decreased the level of procaspase-3. The cleavage of poly (ADP-ribose) polymerase (PARP), a vital substrate of effector caspase, was observed in HCT-116 cells. Furthermore, the induction of apoptosis was also accompanied by an activation of extracellular signal-regulated kinase (ERK) and p38 kinase in HCT-116 cells. These findings provide evidence demonstrating that the pro-apoptotic effects of compounds 1-4 are mediated through the activation of ERK and p38 in HCT-116 cells.

Chronic inflammation in cancer development

Chronic inflammatory mediators exert pleiotropic effects in the development of cancer. On the one hand, inflammation favors carcinogenesis, malignant transformation, tumor growth, invasion, and metastatic spread; on the other hand inflammation can stimulate immune effector mechanisms that might limit tumor growth. The link between cancer and inflammation depends on intrinsic and extrinsic pathways. Both pathways result in the activation of transcription factors such as NF-κB, STAT-3, and HIF-1 and in accumulation of tumorigenic factors in tumor and microenvironment. STAT-3 and NF-κB interact at multiple levels and thereby boost tumor-associated inflammation which can suppress anti-tumor immune responses. These factors also promote tumor growth, progression, and metastatic spread. IL-1, IL-6, TNF, and PGHS-2 are key mediators of an inflammatory milieu by modulating the expression of tumor-promoting factors. In this review we concentrate on the crucial role of pro-inflammatory mediators in inflammation-driven carcinogenesis and outline molecular mechanisms of IL-1 signaling in tumors. In addition, we elucidate the dual roles of stress proteins as danger signals in the development of anti-cancer immunity and anti-apoptotic functions.

Antiproliferative and apoptotic effects triggered by Grape Seed Extract (GSE) versus epigallocatechin and procyanidins on colon cancer cell lines

Grape seed extract has been proven to exert anticancer effects on different tumors. These effects are mainly ascribed to catechin and procyanidin content. Analytical studies demonstrated that grape seed extract composition is complex and it is likely other components could exert biological activities. Using cell count and flow cytometry assays, we evaluated the cytostatic and apoptotic effects produced by three different grape seed extracts from Italia, Palieri and Red Globe cultivars, on Caco2 and HCT-8 colon cancer cells. These effects were compared to those induced by epigallocatechin and procyanidins, alone or in association, on the same cell lines. All the extracts induced growth inhibition and apoptosis in Caco2 and HCT-8 cells, along the intrinsic apoptotic pathway. On both cell lines, growth inhibition induced by Italia and Palieri grape seed extracts was significantly higher than that it has been recorded with epigallocatechin, procyanidins and their association. In Caco2 cells, the extract from Red Globe cultivar was less effective in inducing growth inhibition than procyanidins alone and in association with epigallocatechin, whereas, in HCT-8 cells, only the association of epigallocatechin and procyanidins triggers a significant proliferation decrease. On both cell lines, apoptosis induced by Italia, Palieri and Red Globe grape seed extracts was considerably higher than has been recorded with epigallocatechin, procyanidins and their association. These data support the hypothesis by which other compounds, present in the grape seed extracts, are likely to enhance the anticancer effects.

Green tea epigallocatechin gallate exhibits anticancer effect in human pancreatic carcinoma cells via the inhibition of both focal adhesion kinase and insulin-like growth factor-I receptor

The exact molecular mechanism by which epigallocatechin gallate (EGCG) suppresses human pancreatic cancer cell proliferation is unclear. We show here that EGCG-treated pancreatic cancer cells AsPC-1 and BxPC-3 decrease cell adhesion ability on micro-pattern dots, accompanied by dephosphorylations of both focal adhesion kinase (FAK) and insulin-like growth factor-1 receptor (IGF-1R) whereas retained the activations of mitogen-activated protein kinase and mammalian target of rapamycin. The growth of AsPC-1 and BxPC-3 cells can be significantly suppressed by EGCG treatment alone in a dose-dependent manner. At a dose of 100 μM which completely abolishes activations of FAK and IGF-1R, EGCG suppresses more than 50% of cell proliferation without evidence of apoptosis analyzed by PARP cleavage. Finally, the MEK1/2 inhibitor U0126 enhances growth-suppressive effect of EGCG. Our data suggests that blocking FAK and IGF-1R by EGCG could prove valuable for targeted therapy, which can be used in combination with other therapies, for pancreatic cancer.

EGCG, green tea polyphenols and their synthetic analogs and prodrugs for human cancer prevention and treatment

Cancer-preventive effects of tea polyphenols, especially epigallocatechin-3-gallate (EGCG), have been demonstrated by epidemiological, preclinical, and clinical studies. Green tea polyphenols such as EGCG have the potential to affect multiple biological pathways, including gene expression, growth factor-mediated pathways, the mitogen-activated protein kinase-dependent pathway, and the ubiquitin/proteasome degradation pathway. Therefore, identification of the molecular targets of EGCG should greatly facilitate a better understanding of the mechanisms underlying its anticancer and cancer-preventive activities. Performing structure-activity relationship (SAR) studies could also greatly enhance the discovery of novel tea polyphenol analogs as potential anticancer and cancer-preventive agents. In this chapter, we review the relevant literature as it relates to the effects of natural and synthetic green tea polyphenols and EGCG analogs on human cancer cells and their potential molecular targets as well as their antitumor effects. We also discuss the implications of green tea polyphenols in cancer prevention.

Apoptosis-inducing factor and caspase-dependent apoptotic pathways triggered by different grape seed extracts on human colon cancer cell line Caco-2

Consumption of grape seed extract (GSE) is widely marketed as a dietary supplement and is considered safe for human health. Nevertheless, the analytical composition of GSE from different grape cultivars, growing in special agronomic constraints, differs greatly in flavan-3-ols content. The major concern with GSE studies is a lack of availability of uniformly standardised preparations, which raises an important question whether different GSE samples have comparable activity and trigger the same mechanisms of action on a given biological system. Therefore, it is tempting to speculate that GSE, obtained from different cultivars, could exert differentiated anticancer effects. The focus of the present study is to determine the selective biological efficacy of GSE obtained from three different sources on the human colon cancer cell line Caco-2. Irrespective of its source, high doses of GSE induced a significant inhibition on Caco-2 cell growth. Moreover, apoptosis was enhanced through both caspase-dependent and caspase-independent mechanisms, leading to an early apoptosis-inducing factor release and, further, to a dramatic increase in caspase 7 and 3 activity. However, a significant difference in apoptotic rates induced by the three grape sources clearly emerged when treating cancer cells with low and intermediate GSE concentrations (25 and 50 microg/ml).

p53-Dependent p21-mediated growth arrest pre-empts and protects HCT116 cells from PUMA-mediated apoptosis induced by EGCG

The tumor suppressor protein p53 plays a key role in regulation of negative cellular growth in response to EGCG. To further explore the role of p53 signaling and elucidate the molecular mechanism, we employed colon cancer HCT116 cell line and its derivatives in which a specific transcriptional target of p53 is knocked down by homologous recombination. Cells expressing p53 and p21 accumulate in G1 upon treatment with EGCG. In contrast, same cells lacking p21 traverse through the cell cycle and eventually undergo apoptosis as revealed by TUNEL staining. Treatment with EGCG leads to induction of p53, p21 and PUMA in p21 wild-type, and p53 and PUMA in p21(-/-) cells. Ablation of p53 by RNAi protects p21(-/-) cells, thus indicating a p53-dependent apoptosis by EGCG. Furthermore, analysis of cells lacking PUMA or Bax with or without p21 but with p53 reveals that all the cells expressing p53 and p21 survived after EGCG treatment. More interestingly, cells lacking both PUMA and p21 survived ECGC treatment whereas those lacking p21 and Bax did not. Taken together, our results present a novel concept wherein p21-dependent growth arrest pre-empts and protects cells from otherwise, in its absence, apoptosis which is mediated by activation of pro-apoptotic protein PUMA. Furthermore, we find that p53-dependent activation of PUMA in response to EGCG directly leads to apoptosis with out requiring Bax as is the case in response to agents that induce DNA damage. p21, thus can be used as a molecular switch for therapeutic intervention of colon cancer.

Dietary flavonol, flavone and catechin intake and risk of colorectal cancer in the Netherlands Cohort Study

Dietary flavonoids are hypothesized to be protective against colorectal cancer, yet findings have been inconsistent. We examined the association of dietary flavonol, flavone and catechin intake with colorectal cancer endpoints within the Netherlands Cohort Study (NLCS). In addition, we explored whether body mass index (BMI) may be an effect modifier of this association. The NLCS includes 120,852 men and women who were 55-69 years and completed a self-administered questionnaire at baseline in 1986. A case-cohort approach was used for data processing and analysis. After 13.3 years, 1,444 male and 1,041 female colorectal cancer cases were available for estimation of hazard ratios and 95% confidence intervals for quintiles of flavonoid intake. After adjustment for potential confounders, no association of total flavonol and flavone intake and total catechin intake with colorectal cancer endpoints was observed. Analyses stratified for BMI showed significant inverse trends in the association of total catechin intake, (+)-catechin intake and (-)-epicatechin intake with rectal cancer in men with a BMI>or=25 kg/m2 and in the association of total catechin intake and intake of kaempferol, myricetin and all individual catechins with colorectal cancer, in particular colon cancer, in women with a BMI<25 kg/m2. In conclusion, our findings generally do not support an association of dietary flavonol, flavone and catechin intake with colorectal cancer endpoints. Dietary catechin intake may be associated with a decreased rectal cancer risk in overweight men. Dietary flavonol and catechin intake may be associated with a decreased colorectal cancer risk in normal weight women.

Inhibitory effect of (-)-epigallocatechin and (-)-epigallocatechin gallate against heregulin beta1-induced migration/invasion of the MCF-7 breast carcinoma cell line

Migration/invasion is involved in the multiple steps of metastasis, resulting in a poor prognosis of breast cancer. (-)-Epigallocatechin-3-gallate (EGCG) in green tea inhibits the metastasis of some cancer cell lines. Cell migration/invasion assays using Boyden chambers demonstrated that (-)-epigallocatechin (EGC), another green tea catechin, inhibited heregulin-beta1 (HRG)-induced migration/invasion of MCF-7 human breast carcinoma cells to approximately the same extent as EGCG. Assays of cytoskeletal reorganization, Western blotting and immunoprecipitation suggested that EGCG inhibited this migration/invasion by suppressing the HRG-stimulated activation of epidermal growth factor receptor-related protein B2 (ErbB2)/ErbB3/protein kinase B (Akt), whereas EGC did so through pathways including the disruption of the HRG-stimulated activation of ErbB2/ErbB3 but not Akt. EGC, as well as EGCG, could play an important role against the promotion of metastasis of breast cancer cells.