[Show abstract][Hide abstract] ABSTRACT: Activation of the Wnt pathway is known to promote tumorigenesis and tumor metastasis, and targeting Wnt pathway inhibition has emerged as an attractive approach for controlling tumor invasion and metastasis. The major pathway for inhibiting Wnt is through the degradation of beta-catenin by the GSK3-beta/CK1/Axin/APC complex. It was found that Hep3B hepato-carcinoma cells respond to anthocyanins through GSK3-beta-induced suppression of beta-catenin; however, they cannot dephosphorylate GSK3-beta without AMPK activation.
We tested the effects of anthocyanins on proliferation and apoptosis by MTT and Annexin V-PI staining in vitro. Mouse xenograft models of hepato-carcinomas were established by inoculation with Hep3B cells, and mice were injected with 50 mg/kg/ml of anthocyanins. In addition, protein levels of p-GSK3-beta, beta-catenin, p-AMPK, MMP-9, VEGF, and Ang-1 were also analyzed using western blot.
Anthocyanins decrease phospho-GSK3-beta and beta-catenin expression in an in vivo tumor xenograft model, increase AMPK activity in this model, and inhibit cell migration and invasion, possibly by inhibiting MMP-2 (in vitro) and the panendothelial marker, CD31 (in vivo). To elucidate the role of the GSK3-beta/beta-catenin pathway in cancer control, we conditionally inactivated this pathway, using activated AMPK for inhibition. Further, we showed that AMPK siRNA treatment abrogated the ability of anthocyanins to control cell proliferation and metastatic potential, and Compound C, an AMPK inhibitor, could not restore GSK3-beta regulation, as exhibited by anthocyanins in Hep3B cells.
These observations imply that the AMPK-mediated GSK3-beta/beta-catenin circuit plays crucial roles in inhibiting cancer cell proliferation and metastasis in anthocyanin-treated hepato-carcinoma cells of Meoru origin.
BMC Complementary and Alternative Medicine 03/2014; 14(1):109. DOI:10.1186/1472-6882-14-109 · 2.02 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: The present study investigated the regulatory mechanisms by which epigallocatechin-3-gallate (EGCG) exerts vascular endothelial growth factor (VEGF)-, p53- and AMP-activated protein kinase (AMPK)-associated pro-apoptotic and migration-suppressing effects on colon cancer cells. EGCG decreased the expression levels of VEGF and matrix metalloproteinase (MMP)-9. EGCG treatment induced apoptosis in the presence of wild-type and mutant p53, indicating that a p53-independent pathway may contribute to EGCG-induced apoptosis in these cells. EGCG showed migration-suppressing effects, suggesting that this activity may also have p53-dependent and -independent components. The interaction between p53 and VEGF in the EGCG-treated cells was investigated using pifithrin-α. Notably, the suppression of p53 activity blocked the ability of EGCG to inhibit VEGF and MMP-9 in the cells expressing wild-type p53, but not mutant p53, indicating that the effects of EGCG on VEGF may be p53-dependent or -independent. Finally, although AMPK and VEGF did not appear to co-localize, the results indicated that AMPK controls VEGF in EGCG-treated cells regardless of the p53 status.
[Show abstract][Hide abstract] ABSTRACT: Curcumin, the major phytochemical in turmeric, exerts anti‑proliferative, anticancer and anti‑inflammatory activities in various types of cancer cells. Curcumin has been demonstrated to induce apoptosis through multiple signaling pathways; however, its association with survival pathways, including the Wnt signaling pathway, is not fully understood. The Wnt signaling pathway is involved in diverse functions, including cell development, growth and proliferation. This pathway is important for cancer cell survival and metastasis. β‑catenin and GSK3β play a key role in the Wnt signaling pathway and therefore, various members of the Wnt signaling pathway have been hypothesized to represent potential targets for anticancer therapy. In the present study, the effect of curcumin on the suppression of migration and proliferation of Hep3B hepatocarcinoma cells was investigated via suppression of Wnt signaling in vitro and in vivo. 12‑O‑tetradecanoylphorbol‑13‑acetate (TPA)‑induced cell migration was observed to be suppressed by curcumin treatment. In addition, curcumin suppressed TPA‑induced activation of Wnt signaling. These results indicate that curcumin induces anti‑migratory activity, which functions via the Wnt signaling pathway.
Molecular Medicine Reports 05/2013; 8(1). DOI:10.3892/mmr.2013.1497 · 1.55 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Suppressing the mammalian target of rapamycin (mTOR) pathway has emerged as an attractive method for controlling cancer growth and preventing cancers. Epigallocatechin-3-gallate (EGCG) is a well-known chemopreventive polyphenol, and its effects on AMP-activated protein kinase (AMPK) activation were previously reported. In this study the regulatory mechanisms of EGCG on mTOR and Akt, 2 cancer survival signals, and the interrelationships among mTORC1, Akt, and AMPK were examined. It was found that the suppression of mTORC1 by EGCG requires signals from AMPK, however, the inhibition of Akt with EGCG seems to be AMPK independent. Further, there was no clear indication of Akt as an upstream regulator of mTOR in EGCG treated HT-29 colon cancer cells.
[Show abstract][Hide abstract] ABSTRACT: Oxidative stress has been reported to be associated with cellular injury. Here, we investigated the antioxidant ability of a novel peptide mixture purified from black soybean (Rhynchosia volubilis) that exhibited significant antioxidant ability (IC 50 = 119.8 ± 1.2 µg/ml) under in vitro ABTS assay conditions. To confirm this result, we next examined the antioxidant ability of the peptide mixture using cell culture systems. Black soybean peptide (BSP) significantly reduced the H 2 O 2 -induced cell death in C2C12 myocyte. Moreover, extracellular signal-regulated kinase (ERK) signaling was activated by BSP treatment. Under the same conditions, inhibition of the ERK signaling pathway with PD98059 significantly reduced the antioxidant ability of BSP in C2C12 cells. Finally, we also assessed the antithrombotic ability of BSP using a rat model; we found that the BSP also exerted antithrombotic effects in rat blood. Collectively, these results indicate that BSP purified from black soybean exerts an inhibitory effect on both oxidative stress and thrombosis.
Journal of medicinal plant research 12/2011; 5(29). DOI:10.5897/JMPR11.178 · 0.88 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: The endoplasmic reticulum (ER) is a central organelle in eukaryotic cells that functions in protein synthesis and maturation, and also functions as a calcium storage organelle. Perturbation of ER functions leads to ER stress, which has been previously associated with a broad variety of diseases. ER stress is generally regarded as compensatory, but prolonged ER stress can activate apoptotic pathways in damaged cells. For this reason, pharmacological interventions that effectively enhance tumor death through ER stress have been the subject of a great deal of attention for anti-cancer therapy. Cryptotanshinone, the major active constituent isolated from the root of Salvia miltiorrhiza Bunge, has been recently evaluated for its anti-cancer activity, but the molecular mechanisms underlying these activities remain poorly understood. In particular, it remains completely unknown as to whether or not cryptotanshinone can induce ER stress. Herein, we identify cryptotanshinone as a potent stimulator of ER stress, leading to apoptosis in many cancer cell lines, including HepG2 hepatoma and MCF7 breast carcinoma, and also demonstrate that mitogen-activated protein kinases function as mediators in this process. Reactive oxygen species generated by cryptotanshinone have been shown to play a critical role in ER stress-induced apoptosis. Cryptotanshinone also evidenced sensitizing effects to a broad range of anti-cancer agents including Fas/Apo-1, TNF-α, cisplatin, etoposide or 5-FU through inducing ER stress, highlighting the therapeutic potential in the treatment of human hepatoma and breast cancer.
[Show abstract][Hide abstract] ABSTRACT: Cyclooxygenase-2 (COX-2), the key enzyme of the conversion of arachidonic acid to prostaglandins is an important regulator of inflammation and perhaps apoptosis. Genistein is an active component of legumes and other related food associated with prevention of degenerative diseases possibly through modulating certain signaling pathways. It was investigated whether the induction of apoptosis with genistein was carried out via COX-2 suppression through the regulation of NF-κB. The cox-2 positive and negative cells were used to compare the effect of genistein on the modulation of NF-κB in COX-2 expressed or non-expressed genotypic systems. Suppression of COX-2 as well as decreasing NF-κB DNA binding activity was accompanied with the induction of apoptosis in genistein-treated COX-2 expressed cells. However, in cox-2 negative cells, apoptosis occurred without any involvement of NF-κB with genistein treatement. Genistein induced apoptosis through the generation of reactive oxygen species (ROS) both of cox-2 positive and negative cells. These results suggested that genistein is capable of exihibiting NF-κB-dependent and NF-κB-independent apoptotic control via ROS generation depending on genetic cell types.
Experimental and toxicologic pathology: official journal of the Gesellschaft fur Toxikologische Pathologie 07/2011; 65(1-2). DOI:10.1016/j.etp.2011.05.001 · 1.86 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Luteolin, a plant-derived flavonoid, is thought to inhibit tumor growth. However, the precise molecular mechanisms by which luteolin inhibits cancer cell growth remain unclear. In the present study, we evaluated the role of AMP-activated protein kinase (AMPK) in the inhibition of cancer cell growth by luteolin in HepG2 hepatocarcinoma cells. AMPK is a metabolic sensor and may prevent carcinogenesis via modulation of signaling networks. We found that luteolin strongly induced cell death in HepG2 cells and dramatically reduced the tumor volume in a tumor xenograft model; both effects were accompanied by AMPK activation by luteolin. Luteolin also had a strong inhibitory effect on nuclear factor (NF)-κB. To determine the relationship between AMPK and NF-κB signaling, we used Compound C, a pharmacological AMPK inhibitor, and a dominant-negative form of AMPK. Our results indicated that inhibition of AMPK activity restored luteolin-inhibited NF-κB DNA-binding activity. These results suggest that AMPK activity is critical for the inhibition of cancer cell growth, possibly via modulation of NF-κB activity. We also showed that luteolin treatment causes the release of reactive oxygen species (ROS) and that these intracellular ROS in turn mediate AMPK-NF-κB signaling in HepG2 hepatocarcinoma cells. In conclusion, we propose that AMPK is a novel regulator of NF-κB in luteolin-induced cancer cell death. Furthermore, our results suggest that AMPK is an attractive target for cancer prevention by flavonoids.
International Journal of Molecular Medicine 04/2011; 28(1):25-31. DOI:10.3892/ijmm.2011.667 · 2.09 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Quercetin has been reported to possess therapeutic effects in the treatment of cancers. In this study, the molecular action
of quercetin, with emphasis on its ability to control the intracellular signaling cascades of hypoxia inducible factor-1α
(HIF-1α), mammalian target of rapamycin (mTOR), and AMP-activated protein kinase (AMPK), responsible for survival or induction
of apoptosis in hypoxic MCF-7 cells, was investigated. The effects of quercetin on apoptosis in relation to its ability to
prevent HIF-1α induction were investigated. The involvement of HIF-1α reduction in quercetin-based cancer control was clearly
shown in conditions of mTOR inhibition by rapamycin, an mTOR inhibitor. Surprisingly, quercetin induced an AMPK-suppressed
state in a CoCl2-induced hypoxic condition. It is speculated that quercetin is capable of inhibiting AMPK to decrease HIF-1α, which is a critical
survival factor in hypoxia. A complex control of HIF-1α, mTOR, and AMPK is necessary in inducing apoptosis of MCF-7 breast
cancer cells under hypoxia.
[Show abstract][Hide abstract] ABSTRACT: In lieu of elucidating bidirectional connecting mechanism between AMP-activated protein kinase (AMPK) and survival signal Akt we applied MCF-7 breast cancer cells to determine whether AMPK modulation alters Akt signals and vice versa. Suppression of Akt activities with a synthetic Akt inhibitor alleviated AMPK activities suggesting that Akt is capable of inhibiting AMPK. Also the activation of AMPK with quercetin strongly abrogated Akt activities. Treating cancer cells with AMPK siRNA or Compound C resulted in marked increment of Akt dephosphorylation indicating that AMPK has antagonistic activities towards Akt. However, quercetin exerted Akt inhibitory activities in the absence of AMPK activation. Quercetin induced partial co-localization of phospho-Akt and phospho-AMPK in the nucleus even though their interaction seems to be indirect since the immunoprecipitation data indicate there was no direct binding between total Akt and AMPK. These results suggest there is a mutual suppressive interaction between AMPK and Akt. The investigation of mutual suppression between Akt and AMPK by chemo-preventive agents such as quercetin may provide a mechanistic rational for controlling breast tumor cell growth.
[Show abstract][Hide abstract] ABSTRACT: It has been well known that resveratrol inhibits the proliferation of various cancer cells. AMP-activated protein kinase (AMPK),
a sensor of cellular energy status, has emerged as a potent target for cancer prevention and/or treatment. It has been found
that the activation of AMPK by resveratrol was crucial for the inhibition of HT-29 colon cancer cells. Resveratrol strongly
inhibited phosphorylation of Akt. The possibility whether AMPK activation was essential to the inhibition of p-Akt was investigated
in resveratrol-treated cancer cells. The inhibitory effect of resveratrol on Akt was not observed when AMPK activities were
blocked by the treatment with AMPK siRNA at a relatively lower level of resveratrol. However, the higher concentrations of
resveratrol inhibited Akt without the activation of AMPK. Therefore, it was concluded that resveratrol could modulate Akt
AMPK-dependently or AMPK-independently. The inhibition of Akt along with the activation of AMPK may contribute to the unraveling
anti-cancer mechanism of resveratrol.
KeywordsAkt–AMP-activated kinase–LY294002–resveratrol–HT-29 colon cancer cell
[Show abstract][Hide abstract] ABSTRACT: Fas/APO-1/CD95, a member of the tumor necrosis factor (TNF) receptor superfamily, is a potential anti-cancer factor as it can induce apoptosis in tumor cells. However, despite the fact that many cancer cells express Fas on the membrane, some tumors such as prostate cancer display resistance to Fas-induced apoptosis. In these cases, combination therapy using chemotherapeutic agents and Fas may be more suitable than therapy using Fas alone. In the present study, we demonstrate that the apoptosis inhibitory protein, Bcl-2, was highly expressed in response to Fas in DU145 prostate cancer cells, thereby conferring resistance to apoptosis. We have screened a number of naturally occurring products that may overcome this resistance. Here we report that cryptotanshinone, the major tanshinone isolated from Salvia miltiorrhiza Bunge, can suppress Bcl-2 expression and augment Fas sensitivity in DU145 cells. We further show that JNK and p38 MAPK act upstream of Bcl-2 expression in Fas-treated DU145 cells, and that cryptotanshinone significantly blocked activation of these kinases. Moreover, cryptotanshinone sensitized several tumor cells to a broad range of anti-cancer agents. Collectively, our data suggest that cryptotanshinone has therapeutic potential in the treatment of human prostate cancer.
Cancer letters 12/2010; 298(1):88-98. DOI:10.1016/j.canlet.2010.06.006 · 5.62 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: In this study, the potential of cherry silver berry (Elaeagnus multiflora) as a cancer preventive agent through regulating inflammatory signals including cyclooxygenase-2 (COX-2) and Akt was examined.
Cherry silver berry has reported to exert anti-oxidative, anti-inflammatory, and anti-proliferative effects. The extracts
from seed and flesh of cherry silver berry were obtained, and analyzed COX-2 and Akt activities in cherry silver berry extract
treated HT-29 colon cancer cells. The results showed that the treatment of seed extracts reduced cell viability at the concentrations
above 1,600 mg/mL, effectively reduced COX-2 and p-Akt expression. In addition, the anti-inflammatory effects seemed to be
related to cancer cell death. Both of seed and flesh extracts inhibited cell growth and induced apoptosis in HT-29 cells.
These results suggest that extracts of cherry silver berry may contribute to suppressing cancer growth through its anti-inflammatory
and anti-proliferative effects, and natural products used as oriental medicine have the possibility to control tumor cell
[Show abstract][Hide abstract] ABSTRACT: AMP-activated protein kinase (AMPK) has emerged as a therapeutic target of cancer. AMPK functions as an upstream regulator of proliferative signals such as mammalian target of rapamycin (mTOR), tuberous sclerosis complex (TSC), p70S6 and elongation factor-2, indicating that AMPK can be applied for the inhibition of cancer cell proliferation via modulating the proliferative signaling network. The Akt/mTOR signaling pathway is activated in colon cancer. The well known mTOR inhibitor rapamycin has a disadvantage of feedback stimulation of Akt. Anthocyanins are naturally-occurring mTOR inhibitor possessing Akt inhibitory activities. We have investigated the mTOR inhibitory effect of anthocyanins through the activation of AMPK. In this study, anthocyanins were applied to colon cancer cells and tumor-bearing xenograft models to investigate their anti-proliferative and pro-apoptotic effects, and elucidate the mechanisms that link AMP-activated protein kinase (AMPK) α1 activation to the survival signal of mTOR. Our results indicated that anthocyanins significantly decreased phospho-mTOR comparable to rapamycin, a synthetic mTOR inhibitor, and this inhibitory effect of anthocyanins on mTOR was completely abrogated by inactivating AMPKα1. Furthermore, suppression of cell growth with anthocyanins was also alleviated in the absence of noticeable AMPKα1 activities. For the first time we have found anthocyanins as novel AMPKα1 activators, and in conditions of AMPKα1 inactivation, anthocyanins lost their ability to inhibit mTOR in HT-29 colon cancer cells. The activation of AMPKα1, and the deactivation of mTOR and Akt were observed in anthocyanins-treated tumor-bearing xenograft models. The results from this study suggest that there is a complex interaction between AMPKα1 and mTOR signaling, and anthocyanins are powerful AMPKα1 activators that inhibit cancer cell growth by inhibiting mTOR phosphorylation.
[Show abstract][Hide abstract] ABSTRACT: Effective strategies for cancer prevention and treatment can be identified by understanding the mechanism of apoptotic pathways. In this study, we investigated the regulatory mechanism of quercetin-induced apoptosis through apoptosis signal-regulating kinase (ASK)-1 and mitogen-activated protein kinase pathways. Our results showed that quercetin increased apoptotic cell death through reactive oxygen species (ROS) generation and was responsible for ASK1 activation. Increasing ASK1 activity was accompanied by p38 activation. Interestingly, AMP-activated protein kinase (AMPK) seemed to be a critical controller of quercetin-regulated ASK1/p38 activation. Blocking AMPKalpha1 activity using Compound C, a synthetic inhibitor or siRNA showed that quercetin-activated ASK1 could not stimulate p38 activity. Thus, we suggested that quercetin-exerted apoptotic effects involve ROS/AMPKalpha1/ASK1/p38 signaling pathway, and AMPKalpha1 is a necessary element for apoptotic event induced by ASK1.
Cancer letters 06/2010; 292(2):228-36. DOI:10.1016/j.canlet.2009.12.005 · 5.62 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: We isolated anthocyanins from fruits of Vitis coignetiae Pulliat, characterized the anthocyanin profile, and investigated the anti-invasive effects of the anthocyanins on human colon cancer cells. The anthocyanins inhibited cell invasion in a dose-dependent manner, as measured by Matrigel invasion assays, by suppression of matrix metalloproteinase (MMP)-2 and MMP-9 expression. The anti-invasive activity of the anthocyanins was associated with modulation of constitutive nuclear factor kappaB (NF-kappaB) activation. The activation of NF-kappaB triggered by tumor necrosis factor-alpha was also inhibited by the anthocyanins through suppression IkappaBalpha phosphorylation. AIMs inhibited the expression of NF-kappaB-regulated proteins. In conclusion, this study suggested that the anthocyanins isolated from fruits of V. coignetiae Pulliat should have anti-invasive activities on human colon cancer cells and the activities should be related to the inhibition of NF-kappaB-regulated proteins such as MMP-2 and MMP-9 expression through the inhibition of NF-kappaB activation.
Food and chemical toxicology: an international journal published for the British Industrial Biological Research Association 03/2010; 48(3):903-9. DOI:10.1016/j.fct.2009.12.031 · 2.90 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: In this study, we investigated the molecular basis of Korean kidney bean husk extract, with emphasis on its ability to control intracellular signaling cascades of AMP-activated protein kinase (AMPK) responsible for inducing antitumor activities in colon cancer cells. Recently, the evolutionarily conserved serine/threonine kinase, AMPK, has emerged as a possible target molecule of tumor control. We investigated the effects of Korean kidney bean husk extract on apoptosis regulation and the activation of AMPK. Korean kidney bean husk extract exhibited a series of antitumor effects such as cell death and apoptotic body appearance. These antitumor potentials were accompanied by the increase in p-AMPK and p-Acc as well as antitumor proteins p53 and p21. The stimulation of AMPK by this extract was blocked with the synthetic AMPK inhibitor Compound C at 10 micromol/L, and the combined treatment of Compound C and the AMPK activator AICAR (5-aminoimiazole-4-carboxamide-1-beta-D-ribofuranoside) showed that Compound C could inhibit the activation of AMPK at the concentration of 20 micromol/L. In conclusion, the ability of carcinogenesis control by Korean kidney bean husk extract with high potency suggests its value as an antitumor agent in colon cancer therapy.
Annals of the New York Academy of Sciences 09/2009; 1171(1):484-8. DOI:10.1111/j.1749-6632.2009.04697.x · 4.38 Impact Factor