Zigang Dong

University of Minnesota Duluth, Duluth, Minnesota, United States

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Publications (274)1583.25 Total impact

  • [Show abstract] [Hide abstract]
    ABSTRACT: The aim of this study was to investigate anti-inflammatory and anti-cancer effects of honokiol (HK) in two oral squamous cancer cell carcinoma (OSCC) cell lines, HN22 and HSC4, through the regulation of inducible nitric oxide synthase (iNOS) and endoplasmic reticulum resident protein 44 (ERp44). Griess assay, zymography, and quantitative PCR were performed to study iNOS expression and subsequent nitric oxide (NO) production in OSCC cell lines. Liquid chromatography-tandem mass spectrometry (LC-MS/MS)-based proteomic analysis was used to elucidate the proteins associated with ER stress and cellular cytotoxic response induced by HK. Pull-down assay and molecular modeling were performed to better understand how HK interacts with ERp44. In vitro and in vivo experiments in which ERp44 expression was knocked down were performed to better understand the effects of ERp44 on a cellular level and anti-cancer effects of HK. Expression levels of iNOS and subsequent NO secretion were reduced in OSCC cell lines treated with HK. ERp44 was significantly decreased in OSCC cell lines by HK treatment. HK directly bound to ERp44, and ERp44 knock-down significantly inhibited oral cancer cell proliferation and colony formation. Moreover, HK treatment effectively inhibited tumor growth and ERp44 levels in BALB/c nude mice bearing HN22 cell xenografts. Our findings suggest that HK inhibited inflammation and induced apoptosis by suppressing both iNOS/NO and ERp44 expression in HN22 and HSC4 cells and xenograft tumors, and thus could be a potent anti-inflammatory and anti-cancer drug candidate for human oral cancer treatment.
    Biomaterials 06/2015; 53. DOI:10.1016/j.biomaterials.2015.02.091 · 8.31 Impact Factor
  • Ann M. Bode, Zigang Dong
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    ABSTRACT: Cancer is still a major health issue worldwide and identifying novel but safe compounds for prevention and treatment is a high priority. Licorice (Glycyrrhiza) is a perennial plant that is cultivated in many countries and has been reported to exert antioxidant, anti-inflammatory and anticancer effects. However, some components of licorice exert unwanted side effects and therefore identifying safer licorice components would be ideal. The anticancer activities of many of the licorice components appear to include cycle arrest, apoptosis induction, and general antioxidant effects. Commonly reported indirect protein targets important in tumorigenesis include many cell cycle-related proteins, apoptosis-associated proteins, MMP proteins, COX-2, GSK-β, Akt, NF-κB, and MAP kinases. Importantly, several licorice components were reported to directly bind to and inhibit the activities of PI3-K, MKK4, MKK7, JNK1, mTOR, and Cdk2, resulting in decreased carcinogenesis in several cell and mouse models with no obvious toxicity. This review focuses on specific components of licorice for which a direct protein target has been identified.
    02/2015; 1(1):60-71. DOI:10.1007/s40495-014-0015-5
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    ABSTRACT: Colorectal cancer (CRC) represents the third leading cause of cancer-related death in the United States. Lack of reliable biomarkers remains a critical issue for early detection of CRC. In this study, we investigated the potential predictive values of circulating prostaglandin (PG) biosynthesis in CRC risk. Profiles of circulating PG biosynthesis and platelet counts were determined in healthy subjects (n = 16), familial adenomatous polyposis (FAP) patients who were classified as regular aspirin users (n = 14) or nonusers (n = 24), and CRC patients with (n = 18) or without FAP history (n = 20). Immunohistochemistry staining was performed on biopsy samples. Analysis of circulating PG biosynthesis unexpectedly revealed that CRC progression is accompanied by a pronounced elevation of circulating thromboxane A2 (TXA2) levels. When a circulating TXA2 level of 1000 pg/mL was selected as a practical cutoff point, 95% of CRC patients were successfully identified. Further study suggested that the TXA2 pathway is constitutively activated during colorectal tumorigenesis and required for anchorage-independent growth of colon cancer cells. This study established the importance of the TXA2 pathway in CRC pathophysiology, and laid the groundwork for introducing a TXA2-targeting strategy to CRC prevention, early detection and management.
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    ABSTRACT: LMP1, which is encoded by the Epstein-Barr virus, is proposed to be one of the major oncogenic factors involved in nasopharyngeal carcinoma (NPC). Previous studies demonstrated that down-regulation of LMP1 by LMP1-targeted DNAzyme (DZ1) increases the radiosensitivity of NPC. However, the mechanism by which DZ1 contributes to this radiosensitivity remains unclear. In this study, we determined whether a DZ1 blockade of LMP1 expression has an overall positive effect on the radiotherapy of NPCs by repressing HIF-1/VEGF activity and to investigate the mechanisms underlying LMP1-induced HIF-1 activation in NPC cells. The results showed that DZ1 inhibited the microtubule-forming ability of HUVECs co-cultured with NPC cells, which occurs with the down-regulation of VEGF expression and secretion. Moreover, LMP1 increases phosphorylated JNKs/c-Jun signaling, which is involved in the regulation of HIF-1/VEGF activity. After silencing LMP1 and decreasing phosphorylation of JNKs, NPC cells exhibited an enhanced radiosensitivity. Furthermore, in vivo experiments revealed a significant inhibition of tumor growth and a marked reduction of the Ktrans parameter, which reflects the condition of tumor micro-vascular permeability. Taken together, our data suggested that VEGF expression is increased by LMP1 through the JNKs/c-Jun signaling pathway and indicated that DZ1 enhances the radiosensitivity of NPC cells by inhibiting HIF-1/VEGF activity.
    Oncotarget 01/2015; · 6.63 Impact Factor
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    ABSTRACT: Necroptosis/regulated necrosis is a caspase-independent, but receptor interacting protein kinase (RIPK)-dependent form of cell death. In previous studies, neoalbaconol (NA), a constituent extracted from Albatrellus confluens, was demonstrated to induce necroptosis in some cancer cell lines. The molecular mechanism of NA-induced necroptosis is described in this research study. We determined that NA-induced cell death is partly dependent on tumor necrosis factor α (TNFα) feed-forward signaling. More importantly, NA abolished the ubiquitination of RIPK1 by down-regulating E3 ubiquitin ligases, cellular inhibitors of apoptosis protein 1/2 (cIAP1/2) and TNFα receptor-associated factors (TRAFs). The suppression of RIPK1 ubiquitination induced the activation of the non-canonical nuclear factor-κB (NF-κB) pathway and stimulated the transcription of TNFα. Moreover, we also found that NA caused RIPK3-mediated reactive oxygen species (ROS) production and contribution to cell death. Taken together, these results suggested that two distinct mechanisms are involved in NA-induced necroptosis and include RIPK1/NF-κB-dependent expression of TNFα and RIPK3-dependent generation of ROS.
    Oncotarget 12/2014; · 6.63 Impact Factor
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    ABSTRACT: Non-small-cell lung cancer (NSCLC) is associated with diverse genetic alterations including mutation of epidermal growth factor receptor (EGFR). Isoliquiritigenin (ILQ), a chalcone derivative, possesses anticancer activities. In the present study, we investigated the effects of ILQ on the growth of tyrosine kinase inhibitor (TKI)-sensitive and -resistant NSCLC cells and elucidated its underlying mechanisms. Treatment with ILQ inhibited growth and induced apoptosis in both TKI-sensitive and -resistant NSCLC cells. ILQ-induced apoptosis was associated with the cleavage of caspase-3 and poly-(ADP ribose)-polymerase, increased expression of Bim and reduced expression of Bcl-2. In vitro kinase assay results revealed that ILQ inhibited the catalytic activity of both wildtype and double mutant (L858R/T790M) EGFR. Treatment with ILQ inhibited the anchorage-independent growth of NIH3T3 cells stably transfected with either wildtype or double-mutant EGFR with or without EGF stimulation. ILQ also reduced the phosphorylation of Akt and ERK1/2 in both TKI-sensitive and -resistant NSCLC cells, and attenuated the kinase activity of Akt1 and ERK2 in vitro. ILQ directly interacted with both wildtype and double-mutant EGFR in an ATP-competitive manner. A docking model study showed that ILQ formed two hydrogen bonds (Glu762 and Met793) with wildtype EGFR and three hydrogen bonds (Lys745, Met793 and Asp855) with mutant EGFR. ILQ attenuated the xenograft tumor growth of H1975 cells, which was associated with decreased expression of Ki-67 and diminished phosphorylation of Akt and ERK1/2. Taken together, ILQ suppresses NSCLC cell growth by directly targeting wildtype or mutant EGFR.
    Journal of Biological Chemistry 11/2014; 289(52). DOI:10.1074/jbc.M114.585513 · 4.60 Impact Factor
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    ABSTRACT: Soy isoflavone is an attractive source of functional cosmetic materials with anti-wrinkle, whitening and skin hydration effects. After consumption, the majority of soy isoflavones are converted to their metabolites in the human gastrointestinal tract. To understand the physiological impact of soy isoflavone on the human body, it is necessary to evaluate and address the biological function of its metabolites. In this study, we investigated the effect of 6,7,4'-trihydroxyisoflavone (6,7,4'-THIF), a major metabolite of daidzein, against solar UV (sUV)-induced matrix metalloproteinases (MMPs) in normal human dermal fibroblasts. MMPs play a critical role in the degradation of collagen in skin, thereby accelerating the aging process of skin. The mitogen-activated protein/extracellular signal-regulated kinase (MEK)/extracellular signal-regulated kinase (ERK), mitogen-activated protein kinase (MKK)3/6/p38 and MKK4/c-Jun N-terminal kinases (JNK) signaling pathways are known to modulate MMP-1 function, and their activation by sUV was significantly reduced by 6,7,4'-THIF pretreatment. Our results also indicated that the enzyme activity of protein kinase C (PKC)α, an upstream regulator of MKKs signaling, is suppressed by 6,7,4'-THIF using the in vitro kinase assay. Furthermore, the direct interaction between 6,7,4'-THIF and endogenous PKCα was confirmed using the pull-down assay. Not only sUV-induced MMP-1 expression, but also sUV-induced signaling pathway activation were decreased in PKCα knockdown cells. Overall, we elucidated the inhibitory effect of 6,7,4'-THIF on sUV-induced MMPs and suggest PKCα as its direct molecular target.
    International Journal of Molecular Sciences 11/2014; 15(11):21419-32. DOI:10.3390/ijms151121419 · 2.46 Impact Factor
  • Ann M Bode, Zigang Dong
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    ABSTRACT: Consuming plants for their presumed health benefits has occurred since early civilizations. Phytochemicals are found in various plants that are frequently included in the human diet and are generally thought to be safe for consumption because they are produced naturally. However, this is not always the case and in fact many natural compounds found in several commonly consumed plants are potential carcinogens or tumor promoters and should be avoided.
    Cancer Prevention Research 10/2014; 8(1). DOI:10.1158/1940-6207.CAPR-14-0160 · 5.27 Impact Factor
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    ABSTRACT: 9-cis-UAB30 (UAB30) and Targretin are well-known retinoid X receptor (RXR) agonists. They were highly effective in decreasing the incidence of methylnitrosourea (MNU)-induced mammary cancers. However, whether the anti-mammary cancer effects of UAB30 or Targretin originate from the activation of RXR is unclear. In the present study, we hypothesized that UAB30 and Targretin not only affect RXR, but likely influence one or more off-target proteins. Virtual screening results suggest that Src is a potential target for UAB30 and Targretin that regulates extracellular matrix (ECM) molecules and cell motility and invasiveness. In vitro kinase assay data revealed that UAB30 or Targretin interacted with Src and attenuated its kinase activity. We found that UAB30 or Targretin substantially inhibited invasiveness and migration of MCF-7 and SK-BR-3 human breast cancer cells. We examined the effects of UAB30 and Targretin on the expression of matrix metalloproteinases (MMP)-9, which are known to play an essential role in tumor invasion. We show that activity and expression of MMP-9 were decreased by UAB30 or Targretin. Western blot data showed that UAB30 or Targretin decreased AKT and its substrate molecule p70s6k, which are downstream of Src in MCF-7 and SK-BR-3 cells. Moreover, knocking down the expression of Src effectively reduced the sensitivity of SK-BR-3 cells to the inhibitory effects of UAB30 and Targretin on invasiveness. Taken together, our results demonstrate that UAB30 and Targretin each inhibit invasion and migration by targeting Src in human breast cancer cells. © 2014 Wiley Periodicals, Inc.
    Molecular Carcinogenesis 10/2014; DOI:10.1002/mc.22232 · 4.27 Impact Factor
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    ABSTRACT: Although specific compounds found in some East Asian traditional medicines have been shown to exhibit bioactive properties, their molecular mechanisms of action remain elusive. The bark of the Alnus species has been used for the treatment of various pathological conditions including hemorrhage, alcoholism, fever, diarrhea, skin diseases, inflammation, and cancer in East Asia for centuries. In this study, we show that hirsutenone, a bioactive compound in Alnus japonica, exhibits anti-cancer effects against prostate cancer through a direct physical inhibition of Akt1/2. Hirsutenone suppressed anchorage-dependent and independent cell growth of PC3 and LNCaP human prostate cancer cells. Annexin V and Propidium iodide (PI) staining results demonstrated that hirsutenone strongly induces apoptotic cell death in both PC3 and LNCaP cells. Furthermore, treatment of hirsutenone attenuated phosphorylation of mammalian target of rapamycin (mTOR), a downstream substrate of Akt, without affecting Akt phosphorylation. Kinase and pull-down assay results clearly show that hirsutenone inhibits Akt1 and 2 by direct binding in an adenosine triphosphate (ATP)-noncompetitive manner in vitro and ex vivo. Our results show that hirsutenone suppresses human prostate cancer by targeting Akt1 and 2 as a key component to explain for anti-cancer activity of Alnus species. © 2014 Wiley Periodicals, Inc.
    Molecular Carcinogenesis 09/2014; DOI:10.1002/mc.22211 · 4.27 Impact Factor
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    ABSTRACT: Studies have shown that a major metabolite of the red ginseng ginsenoside Rb1, called 20-O-β-D-glucopyranosyl-20(S)-protopanaxadiol (GPD), exhibits anticancer properties. However, the chemotherapeutic effects and molecular mechanisms behind GPD action in human melanoma have not been previously investigated. Here we report the anticancer activity of GPD and its mechanism of action in melanoma cells. GPD, but not its parent compound Rb1, inhibited melanoma cell proliferation in a dose-dependent manner. Further investigation revealed that GPD treatment achieved this inhibition through the induction of autophagy and apoptosis, while Rb1 failed to show significant effect at the same concentrations. The inhibitory effect of GPD appears to be mediated through the induction of AMPK and the subsequent attenuation of mTOR phosphorylation. In addition, GPD activated c-Jun by inducing JNK phosphorylation. Our findings suggest that GPD suppresses melanoma growth by inducing autophagic cell death and apoptosis via AMPK/JNK pathway activation. GPD therefore has the potential to be developed as a chemotherapeutic agent for the treatment of human melanoma.
    PLoS ONE 08/2014; 9(8):e104305. DOI:10.1371/journal.pone.0104305 · 3.53 Impact Factor
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    ABSTRACT: Non-small cell lung cancer (NSCLC) is the most lethal cancer causing more than 150,000 deaths in the United States in 2013. The receptor tyrosine kinase inhibitors (TKIs), such as gefitinib, are not perfect clinical therapeutic agents for NSCLC treatment due to primary or acquired TKI resistance. Herein, 3,6,2',4',5'- pentahydroxyflavone (36245-PHF) was identified as a multiple kinase inhibitor for NSCLC treatment based on the computational screening of a natural products database. 36245-PHF was shown to inhibit PI3-K, Aurora A and B kinases and overcome gefitinib-resistant NSCLC growth. Our data clearly showed that 36245-PHF markedly inhibited anchorage-independent growth of gefitinib-resistant NSCLC cell lines, and exerted a substantial chemotherapeutic effect following oral administration in a gefitinib-resistant NSCLC xenograft model. The evidence from 3 different subsequent methodological approaches, in vitro, ex vivo and in vivo, all confirmed that 36245-PHF as a multiple protein kinase inhibitor. Overall, we identified 36245-PHF as a multiple protein kinase inhibitor and as a novel therapeutic agent to overcome gefitinib-resistant NSCLC growth, which could provide a new option for clinical NSCLC oral treatment.
    Journal of Biological Chemistry 08/2014; 289(41). DOI:10.1074/jbc.M114.593475 · 4.60 Impact Factor
  • Yan Li, Xiang Li, Weiya Ma, Zigang Dong
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    ABSTRACT: The epidermal growth factor receptor (EGFR) is aberrantly activated in various cancer cells and an important target for cancer treatment. Deep understanding of EGFR conformational changes between the active and inactive states is of pharmaceutical interest. Here we present a strategy combining multiply targeted molecular dynamics simulations, unbiased molecular dynamics simulations, and Bayesian clustering to investigate transition pathways during the activation/inactivation process of EGFR kinase domain. Two distinct pathways between the active and inactive forms are designed, explored, and compared. Based on Bayesian clustering and rough two-dimensional free energy surfaces, the energy-favorable pathway is recognized, though DFG-flip happens in both pathways. In addition, another pathway with different intermediate states appears in our simulations. Comparison of distinct pathways also indicates that disruption of the Lys745-Glu762 interaction is critically important in DFG-flip while movement of the A-loop significantly facilitates the conformational change. Our simulations yield new insights into EGFR conformational transitions. Moreover, our results verify that this approach is valid and efficient in sampling of protein conformational changes and comparison of distinct pathways.
    Journal of Chemical Theory and Computation 08/2014; 10(8):3503-3511. DOI:10.1021/ct500162b · 5.31 Impact Factor
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    ABSTRACT: Caffeic acid (3,4-dihydroxycinnamic acid) is a well-known phenolic phytochemical present in coffee and reportedly has anticancer activities. However, the underlying molecular mechanisms and targeted proteins involved in the suppression of carcinogenesis by caffeic acid are not fully understood. In this study, we report that caffeic acid significantly inhibits colony formation of human skin cancer cells and EGF-induced neoplastic transformation of HaCaT cells dose-dependently. Caffeic acid topically applied to dorsal mouse skin significantly suppressed tumor incidence and volume in a solar UV-induced skin carcinogenesis mouse model. A substantial reduction of phosphorylation in mitogen-activated protein kinase signaling was observed in mice treated with caffeic acid either before or after solar UV exposure. Caffeic acid directly interacted with ERK1/2 and inhibited ERK1/2 activities in vitro. Importantly, we resolved the co-crystal structure of ERK2 complexed with caffeic acid. Caffeic acid interacted directly with ERK2 at amino acid residues Q105, D106 and M108. Moreover, A431 cells expressing knockdown of ERK2 lost sensitivity to caffeic acid in a skin cancer xenograft mouse model. Taken together, our results suggest that caffeic acid exerts chemopreventive activity against solar UV-induced skin carcinogenesis by targeting ERK1 and 2.
    Cancer Prevention Research 08/2014; 7(10). DOI:10.1158/1940-6207.CAPR-14-0141 · 5.27 Impact Factor
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    ABSTRACT: Solar ultraviolet (SUV) irradiation is a major factor in skin carcinogenesis, the most common form of cancer in the USA. The mitogen-activated protein (MAP) kinase cascades are activated by SUV irradiation. The 90 kDa ribosomal S6 kinase (RSK) and mitogen and stress activated protein kinase (MSK) proteins constitute a family of protein kinases that mediate signal transduction downstream of the MAP kinase cascades. In this study, phosphorylation of RSK and MSK1 was up-regulated in human squamous cell carcinoma (SCC) and solar UV-treated mouse skin. Kaempferol, a natural flavonol, found in tea, broccoli, grapes, apples and other plant sources, is known to have anticancer activity, but its mechanisms and direct target(s) in cancer chemoprevention are unclear. Kinase array results revealed that kaempferol inhibited RSK2 and MSK1. Pull-down assay results, ATP competition and in vitro kinase assay data revealed that kaempferol interacts with RSK2 and MSK1 at the ATP-binding pocket and inhibits their respective kinase activities. Mechanistic investigations showed that kaempferol suppresses RSK2 and MSK1 kinase activities to attenuate solar UV-induced phosphorylation of CREB and histone H3 in mouse skin cells. Kaempferol was a potent inhibitor of solar UV-induced mouse skin carcinogenesis. Further analysis showed that skin from the kaempferol-treated group exhibited a substantial reduction in solar UV-induced phosphorylation of cAMP response element-binding protein (CREB), c-Fos and histone H3. Overall, our results identify kaempferol as a safe and novel chemopreventive agent against solar UV-induced skin carcinogenesis that acts by targeting RSK2 and MSK1.
    Cancer Prevention Research 07/2014; 7(9). DOI:10.1158/1940-6207.CAPR-14-0126 · 5.27 Impact Factor
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    ABSTRACT: Lung cancer is a leading cause of death worldwide and MET amplification is a major therapeutic limitation in acquired-resistance lung cancer. We hypothesized that butein, a phytochemical, can overcome gefitinib-induced resistance by targeting both EGFR and MET in non-small cell lung cancer (NSCLC). To investigate the ability of butein to target EGFR and MET, we used in silico docking, a library of natural compounds and kinase assays. The effects of butein on growth, induction of apoptosis and expression of EGFR/MET signaling targets were examined in HCC827 (gefitinib-sensitive) and HCC827GR (gefitinib-resistant) NSCLC cells. Results were confirmed in vivo by a HCC827 or HCC827GR cell xenograft mouse model, each treated with vehicle, butein or gefitinib. Butein inhibited phosphorylation and kinase activity of EGFR and MET as well as soft agar colony formation and decreased viability of HCC827 and HCC827GR cells. Butein increased apoptosis-related protein expression in these cells. Results were confirmed by co-treatment with inhibitors of EGFR/MET or double knock-down. Finally, xenograft study results showed that butein strongly suppressed HCC827 and HCC827GR tumor growth. Immunohistochemical data suggest that butein inhibited Ki-67 expression. These results indicate that butein has potent anticancer activity and targets both EGFR and MET in acquired-resistance NSCLC. © 2014 Wiley Periodicals, Inc.
    Molecular Carcinogenesis 06/2014; 54(4). DOI:10.1002/mc.22191 · 4.77 Impact Factor
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    ABSTRACT: Nearly a hundred years of scientific research has revealed a notable preference of cancer cells to utilize aerobic glycolysis rather than mitochondrial oxidative phosphorylation for glucose-dependent ATP production, which is thought to be the root of tumor formation and growth. Glycolysis is a complex biochemical process that is mediated by multiple glycolytic genes. Besides regulating glucose metabolism, these genes are also suggested to possess various other functions related to cancer, including roles in cancer development and promotion, inhibition of apoptosis, cell cycle progression, and tumor metastasis. This article highlights the biological functions of glycolytic genes beyond their role in regulation of glycolysis and discusses their clinical implications, especially in regard to the use of glycolytic genes as biomarkers for early detection of cancer or as targets for novel anticancer treatments.
    Journal of Molecular Medicine 06/2014; 92(8). DOI:10.1007/s00109-014-1174-x · 4.74 Impact Factor
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    ABSTRACT: For decades, skin cancer incidence has increased, mainly due to oncogenic signaling pathways activated by solar ultraviolet (UV) irradiation (i.e., sun exposure). Solar UV induces multiple signaling pathways that are critical in the development of skin cancer, and therefore the development of compounds capable of targeting multiple molecules for chemoprevention of skin carcinogenesis is urgently needed. Herein, we examined the chemopreventive effects and the molecular mechanism of HOEC, [(+)-2-(1-hydroxyl-4-oxocyclohexyl) ethyl caffeate], isolated from Incarvillea mairei var. grandiflora (Wehrhahn) Grierson. HOEC strongly inhibited neoplastic transformation of JB6 C14l cells without toxicity. PI3-K, ERK1/2 and p38 kinase activities were suppressed by direct binding with HOEC in vitro. Our in silico docking data showed that HOEC binds at the ATP-binding site of each kinase. The inhibition of solar UV-induced PI3-K, ERK1/2 and p38 kinase activities resulted in suppression of their downstream signaling pathways and AP-1 and NF-κB transactivation in JB6 cells. Furthermore, topical application of HOEC reduced skin cancer incidence and tumor volume in SKH-1 hairless mice chronically exposed to solar UV. In summary, our results show that HOEC exerts inhibitory effects on multiple kinase targets and their downstream pathways activated by solar UV in vitro and in vivo. These findings suggest that HOEC is as a potent chemopreventive compound against skin carcinogenesis caused by solar UV exposure.
    Cancer Prevention Research 05/2014; 7(8). DOI:10.1158/1940-6207.CAPR-13-0286 · 5.27 Impact Factor
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    ABSTRACT: Various health effects have been attributed to the ginsenoside metabolite 20-O-β-D-glucopyranosyl-20(S)-protopanaxadiol (GPD); however, its effect on ultraviolet (UV)-induced matrix metalloproteinase (MMP)-1 expression and the mechanism underlying this effect are unknown. We examined the inhibitory effect of GPD on UV-induced MMP-1 expression and its mechanisms in human dermal fibroblasts (HDFs). GPD attenuated UV-induced MMP-1 expression in HDFs and suppressed the UV-induced phosphorylation of mammalian target of rapamycin (mTOR) and p70S6K without inhibiting the activity of phosphatidylinositol 3-kinase and Akt, which are well-known upstream kinases of mTOR. GPD augmented the phosphorylation of liver kinase B1 (LKB1) and adenosine monophosphate-activated protein kinase (AMPK), which are inhibitors of mTOR, to a greater extent than UV treatment alone. Similar to GPD, 5-aminoimidazole-4-carboxamide-1-β-d-ribofuranosyl 5′-monophosphate (AICAR), an activator of AMPK, augmented UV-induced AMPK phosphorylation to a greater extent than UV treatment alone, resulting in the inhibition of MMP-1 expression. AICAR also decreased the phosphorylation of mTOR and p70S6K. However, compound C, an antagonist of AMPK, increased MMP-1 expression. In HDF cells with AMPK knock-down using shRNA, MMP-1 expression was increased. These results indicate that AMPK activation plays a key role in MMP-1 suppression. Additionally, the cAMP-dependent protein kinase (PKA) inhibitor, H-89, antagonized GPD-mediated MMP-1 suppression via the inhibition of LKB1. Our results suggest that the suppressive activity of GPD on UV-induced MMP-1 expression is due to the activation of AMPK as a downstream of the PKA-LKB1 pathway. J. Cell. Biochem. © 2014 Wiley Periodicals, Inc.
    Journal of Cellular Biochemistry 05/2014; 115(10). DOI:10.1002/jcb.24833 · 3.37 Impact Factor
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    ABSTRACT: Nanog regulates human and mouse embryonic stem (ES) cell self-renewal activity. Activation of ERKs signaling negatively regulates ES cell self-renewal and induces differentiation, but the mechanisms are not understood. We found that ERK1 binds and phosphorylates Nanog. Activation of MEK/ERKs signaling and phosphorylation of Nanog inhibit Nanog transactivation, inducing ES cell differentiation. Conversely, suppression of MEK/ERKs signaling enhances Nanog transactivation to inhibit ES cell differentiation. We observed that phosphorylation of Nanog by ERK1 decreases Nanog stability through ubiquitination-mediated protein degradation. Further, we found that this phosphorylation induces binding of FBXW8 with Nanog to reduce Nanog protein stability. Overall, our results demonstrated that ERKs-mediated Nanog phosphorylation plays an important role in self-renewal of ES cells through FBXW8-mediated Nanog protein stability.
    Stem Cell Research 04/2014; 13(1):1-11. DOI:10.1016/j.scr.2014.04.001 · 4.47 Impact Factor

Publication Stats

8k Citations
1,583.25 Total Impact Points


  • 1998–2015
    • University of Minnesota Duluth
      • College of Pharmacy
      Duluth, Minnesota, United States
  • 2012–2013
    • The Advanced Institutes of Convergence Technology
      Yeoncheon Gun, South Korea
    • Catholic University of Korea
      Sŏul, Seoul, South Korea
    • Korea Research Institute of Bioscience and Biotechnology KRIBB
      • Chemical Biology Research Center
      Anzan, Gyeonggi Province, South Korea
  • 2008–2013
    • Seoul National University
      • Department of Agricultural Biotechnology
      Sŏul, Seoul, South Korea
    • Russian Academy of Sciences
      • G.B. Elyakov Pacific Institute of Bioorganic Chemistry
      Moskva, Moscow, Russia
    • Arizona Research Center
      Phoenix, Arizona, United States
  • 2006–2013
    • Central South University
      • Cancer Research Institute
      Changsha, Hunan, China
    • Pacific Institute of Bioorganic Chemistry
      Wladiwostok, Primorskiy, Russia
  • 2011–2012
    • Guangdong Medical College
      • Department of Biochemistry
      Tung-kuan, Guangdong, China
    • The University of Arizona
      • Department of Pharmacology
      Tucson, Arizona, United States
  • 2010–2011
    • Konkuk University
      • Department of Bioscience and Technology
      Seoul, Seoul, South Korea
  • 2009
    • Molecular and Cellular Biology Program
      • Department of Molecular and Cellular Biology
      Seattle, Washington, United States
  • 2005
    • Hunan University
      Ch’ang-sha-shih, Hunan, China
  • 2003
    • Aichi Cancer Center
      Ōsaka, Ōsaka, Japan
    • Kanazawa University
      • Department of Hospital Pharmacy
      Kanazawa, Ishikawa, Japan
  • 1993–1997
    • National Cancer Institute (USA)
      • Laboratory of Human Carcinogenesis
      Maryland, United States