USP8 modulates ubiquitination of LRIG1 for Met degradation.

The Met receptor tyrosine kinase is an attractive target for cancer therapy as it promotes invasive tumor growth. SAIT301 is a novel anti-Met antibody, which induces LRIG1-mediated Met degradation and inhibits tumor growth. However, detailed downstream mechanism by which LRIG1 mediates target protein down-regulation is unknown. In the present study, we discovered that SAIT301 induces ubiquitination of LRIG1, which in turn promotes recruitment of Met and LRIG1 complex to the lysosome through its interaction with Hrs, resulting in concomitant degradation of both LRIG1 and Met. We also identified USP8 as a LRIG1-specific deubiquitinating enzyme, reporting the interaction between USP8 and LRIG1 for the first time. SAIT301 triggers degradation of LRIG1 by inhibiting the interaction of LRIG1 and USP8, which regulates ubiquitin modification and stability of LRIG1. In summary, SAIT301 employs ubiquitination of LRIG1 for its highly effective Met degradation. This unique feature of SAIT301 enables it to function as a fully antagonistic antibody without Met activation. We found that USP8 is involved in deubiquitination of LRIG1, influencing the efficiency of Met degradation. The relation of Met, LRIG1 and USP8 strongly supports the potential clinical benefit of a combination treatment of a USP8 inhibitor and a Met inhibitor, such as SAIT301.

Bifunctional chemopreventive effects of Adenocaulon himalaicum through induction of detoxification enzymes and apoptosis.

Phase II detoxification enzymes are known to play essential roles in the detoxification and elimination of activated carcinogens during tumor initiation, while apoptosis is one of the most important chemopreventive targets for inhibiting tumor promotion in cancer. In this study, we investigated the cancer chemopreventive activity of two plant extracts, the ethanolic extract of Adenocaulon himalaicum (AHE) and the butanolic fraction of AHE (AHB). Both, the AHE and AHB induced NQO1 activity and had relatively high chemoprevention indices (CI=12.4). The AHE and AHB were associated with increased NQO1 and HO-1 mRNA levels via Nrf2-ARE pathway activation. In addition, the AHB increased CYP1A1 activity through AhR-XRE pathway activation. We also found that the AHE and AHB induced apoptosis, as evidenced by phosphatidylserine externalization, an increase in the sub-G0/G1 content, chromatin condensation, poly(ADP-ribose) polymerase cleavage, and p53 induction. These data suggest that AHE and AHB act as bifunctional inducers and that their chemopreventive effects result from the biphasic induction of phase II detoxification enzymes and apoptosis. Therefore, these results suggest that A. himalaicum plant extracts have potential for use as chemopreventive agents for the prevention and/or treatment of human cancers.

Nuclear factor-E2 (Nrf2) is regulated through the differential activation of ERK1/2 and PKC α/ßII by Gymnasterkoreayne B.

Phytochemicals are well known to have cancer chemopreventive effects by induction of phase II detoxification enzymes including quinone reductase (NQO-1) and glutathione-S-transferases. These detoxification enzymes are commonly regulated by nuclear factor-E2 (Nrf2), which is a representative antioxidant and cytoprotective factor involved in cancer chemoprevention. As one of the known quinone reductase (QR) inducers and Nrf2 activators, Gymnasterkoreayne B (GKB) isolated from Gymnaster (Aster) koraiensis was used to elucidate the upstream signalling pathway for Nrf2 regulation. In this study, we confirmed that GKB significantly increases expression levels of Nrf2 in HCT116 human colon cancer cells. We found the probable mechanism of upstream signalling pathways to activate Nrf2 by GKB. To reveal the pathway that affects Nrf2 translocation by GKB, we examined changes in various kinases in HCT116 cells treated with GKB. We observed that ERK and PKC pathways are particularly involved in the activation of Nrf2 by GKB, followed by translocation of Nrf2 and induction of NQO-1. These results suggest that GKB induces Nrf2 translocation and expression by differential regulation of ERK and PKC pathways in HCT116 cells.

A new anti-c-Met antibody selected by a mechanism-based dual-screening method: therapeutic potential in cancer.

c-Met, the high affinity receptor for hepatocyte growth factor (HGF), is one of the most frequently activated tyrosine kinases in many human cancers and a target for cancer therapy. However, inhibitory targeting of c-Met with antibodies has proven difficult, because most antibodies have intrinsic agonist activity. Therefore, the strategy for reducing the agonism is critical for successful development of cancer therapies based on anti-c-Met antibodies. Here we developed a mechanism-based assay method for rapid screening of anti-c-Met antibodies, involving the determination of Akt phosphorylation and c-Met degradation for agonism and efficacy, respectively. Using the method, we identified an antibody, F46, that binds to human c-Met with high affinity (Kd = 2.56 nM) and specificity, and induces the degradation of c-Met in multiple cancer cells (including MKN45, a gastric cancer cell line) with minimal activation of c-Met signaling. F46 induced c-Met internalization in both HGF-dependent and HGF-independent cells, suggesting that the degradation of c-Met results from antibody-mediated receptor internalization. Furthermore, F46 competed with HGF for binding to c-Met, resulting in the inhibition of both HGF-mediated invasion and angiogenesis. Consistently, F46 inhibited the proliferation of MKN45 cells, in which c-Met is constitutively activated in an HGF-independent manner. Xenograft analysis revealed that F46 markedly inhibits the growth of subcutaneously implanted gastric and lung tumors. These results indicate that F46, identified by a novel mechanism-based assay, induces c-Met degradation with minimal agonism, implicating a potential role of F46 in therapy of human cancers.

SAR studies of gymnasterkoreayne derivatives with cancer chemopreventive activities.

We synthesized diyne triols based on gymnasterkoreayne and evaluated their cancer chemopreventive activities in terms of the chemopreventive index (CI) to reveal the structure-activity relationship, and discovered more active compounds than natural diynes.

Bi-functional induction of the quinone reductase and cytochrome P450 1A1 by youngiasides via Nrf2-ARE and AhR-XRE pathways.

Many phytochemicals are known to exert cancer chemopreventive activity by eliminating chemical carcinogens or toxic xenobiotics through the action of detoxification enzymes. In this study, we investigated the cancer chemopreventive effects of youngiasides isolated from Crepidiastrum denticulatum. These youngiasides significantly induced quinone reductase (QR) activity in mouse hepatoma Hepa-1c1c7 cells, and showed a relatively high chemoprevention index (CI; divided IC(50) value with CD value). The youngiasides also significantly induced transcriptional activation of QR in Hepa-QR-secreted alkaline phosphatase (SEAP) cells, which is a stable cell line containing the intact promoter region of QR. In order to determine if upregulation of QR by the youngiasides was mediated through a mono-functional or bi-functional mechanism, we examined the nuclear factor-E2 p45-related factor 2(Nrf2)-antioxidant response element (ARE) and aryl hydrocarbon receptor (AhR)-xenobiotic response element (XRE) pathways, which are two major pathways, involved in regulation of Phase I and/or Phase II detoxification enzymes. The youngiasides increased the cytochrome P450 1A1 (CYP1A1) mRNA and protein levels in human colorectal cancer Caco-2 cells and also increased the QR mRNA and protein levels in Caco-2 cells through ARE and XRE activation which resulted from translocation of Nrf2 and AhR into the nucleus. These results suggest that regulation of QR by the youngiasides was due to bi-functional induction through the Nrf2-ARE and AhR-XRE pathways. Thus, these youngiasides as bi-functional inducers of QR have potential as cancer chemopreventive agents.

A polyacetylene from Gymnaster koraiensis exerts hepatoprotective effects in vivo and in vitro.

In the present study, we isolated a polyacetylene, gymnasterkoreayne B (GKB), from Gymnaster koraiensis and investigated the effect of GKB on the protection from oxidative stress-induced cytotoxicity through induction of the expression of cellular defense enzymes. GKB induced mRNA expression and enzyme activity of NAD(P)H:quinone oxidoreductase (NQO1) in vitro and in vivo, and potently increased expression of many cellular defense genes including glutathione-S-transferases, UDP-glucuronosyltransferase, and glutathione reductase (GSR) in normal rat liver. The nuclear factor erythroid 2-related factor 2 (Nrf2) which is known to induce various antioxidant and cytoprotective genes, and the genes containing the antioxidant response element (ARE), including NQO1, hemeoxygenease-1, GSR were induced by GKB in HepG2 human hepatocarcinoma cells. Pre-treatment of the cells with GKB accelerated the production of glutathione and mitigated menadione-induced cytotoxicity in HepG2 cells. Taken together, we found that GKB was a novel inducer of phase II detoxification enzymes and cellular defense enzymes, resulting in protection of the cells from oxidative stress and hepatotoxicity through regulation of detoxifying and antioxidant systems.

Flow cytometric fluorescence pulse width analysis of etoposide-induced nuclear enlargement in HCT116 cells.

Fluorescence pulse width can provide size information on the fluorescence-emitting particle, such as the nuclei of propidium iodide-stained cells. To analyze nuclear size in the present study, rather than perform the simple doublet discrimination approach usually employed in flow cytometric DNA content analyses, we assessed the pulse width of the propidium iodide fluorescence signal. The anti-cancer drug etoposide is reportedly cytostatic, can induce a strong G2/M arrest, and results in nuclear enlargement. Based on these characteristics, we used etoposide-treated HCT116 cells as our experimental model system. The fluorescence pulse widths (FL2-W) of etoposide-treated (10 microM, 48 h) cells were distributed at higher positions than those of vehicle control, so the peak FL2-W value of etoposide-treated cells appeared at 400 while those of vehicle control cells appeared at 200 and 270. These results were consistent with our microscopic observations. This etoposide-induced increase in FL2-W was more apparent in G2/M phase than other cell cycle phases, suggesting that etoposide-induced nuclear enlargement preferentially occurred in G2/M phase cells rather than in G0/G1 or S phase cells.

The chemopreventive effects of Carpesium abrotanoides are mediated by induction of phase II detoxification enzymes and apoptosis in human colorectal cancer cells.

Cancer chemoprevention is thought to occur either by blocking the initiation of or suppressing the promotion of carcinogenesis. Phase II detoxification enzymes are known to play important roles in cancer chemoprevention because they enhance cytoprotection through detoxification and elimination of activated carcinogens at tumor initiation. Apoptosis is one of the most important inhibitory targets for tumor promotion. In this study, we have investigated the cancer chemopreventive activity of the ethanolic extract of Carpesium abrotanoides (CAE). We found that CAE induced quinone reductase [also known as NAD(P)H:quinone oxidoreductase (NQO1)] activity, increased NQO1 mRNA and protein expression, and had a relatively high chemoprevention index (12.04). CAE also significantly activated the antioxidant response element through the nuclear accumulation of NF-E2-related factor 2 in HCT116. Interestingly, we also found that CAE induced apoptosis, as evidenced by the externalization of phosphatidylserine, increased sub-G(0)/G(1) content, chromatin condensation, poly(ADP-ribose) polymerase cleavage, and p53. These data suggest that the chemopreventive effects of C. abrotanoides can result from both the induction of phase II detoxification enzymes and from apoptosis. Thus, CAE could potentially be developed as a cancer chemopreventive agent for prevention or treatment of human cancers.

Induction of the phase II detoxification enzyme NQO1 in hepatocarcinoma cells by lignans from the fruit of Schisandra chinensis through nuclear accumulation of Nrf2.

The upregulation of phase II detoxification genes is believed to play an important role in cancer prevention. The molecular mechanism underlying the changes in gene expression that accompany cancer prevention involves activation of the transcription factor, NF-E2-related factor 2 (Nrf2). In traditional medicine, the fruit of Schisandra chinensis Baill is used as a tonic, an anti-tussive and an anti-aging drug. In the current study, nine lignans were isolated from S. chinensis and tested for their ability to induce quinone reductase (QR) activity in Hepa1c1c7 mouse hepatocarcinoma cells. Tigloylgomisin H (TGH) and angeloylgomisin H (AGH) significantly induced QR activity and exhibited a relatively high chemoprevention index (CI) (10.80 and 4.59, respectively) as compared to control. TGH also induced QR activity in BPrc1 mouse hepatocarcinoma cells as well, which are defective in aryl hydrocarbon nuclear translocator (Arnt). In HepG2 human hepatocarcinoma cells, TGH significantly activated gene expression mediated by the antioxidant response element (ARE), a key regulatory region in the promoters of detoxification enzymes, through the nuclear accumulation of Nrf2. The results of the current study suggest that TGH functions as a novel monofunctional inducer that specifically upregulates phase II enzymes through the Nrf2-ARE pathway. TGH thus represents a potential liver cancer prevention agent.

Tectoridin, a poor ligand of estrogen receptor alpha, exerts its estrogenic effects via an ERK-dependent pathway.

Phytoestrogens are the natural compounds isolated from plants, which are structurally similar to animal estrogen, 17beta-estradiol. Tectoridin, a major isoflavone isolated from the rhizome of Belamcanda chinensis. Tectoridin is known as a phytoestrogen, however, the molecular mechanisms underlying its estrogenic effect are remained unclear. In this study we investigated the estrogenic signaling triggered by tectoridin as compared to a famous phytoestrogen, genistein in MCF-7 human breast cancer cells. Tectoridin scarcely binds to ER alpha as compared to 17beta-estradiol and genistein. Despite poor binding to ER alpha, tectoridin induced potent estrogenic effects, namely recovery of the population of cells in the S-phase after serum starvation, transactivation of the estrogen response element, and induction of MCF-7 cell proliferation. The tectoridin-induced estrogenic effect was severely abrogated by treatment with U0126, a specific MEK1/2 inhibitor. Tectoridin promoted phosphorylation of ERK1/2, but did not affect phosphorylation of ER alpha at Ser(118). It also increased cellular accumulation of cAMP, a hallmark of GPR30-mediated estrogen signaling. These data imply that tectoridin exerts its estrogenic effect mainly via the GPR30 and ERK-mediated rapid nongenomic estrogen signaling pathway. This property of tectoridin sets it aside from genistein where it exerts the estrogenic effects via both an ER-dependent genomic pathway and a GPR30-dependent nongenomic pathway.

The chemopreventive effects of Saussurea salicifolia through induction of apoptosis and phase II detoxification enzyme.

The ethanol extract of the aerial part of the Mongolian medicinal plant Saussurea salicifolia induced a dose-dependent cell growth inhibition in both human gastric adenocarcinoma AGS cells and mouse hepatoma Hepa 1c1c7 cells (IC(50)=30.22 and 116.96 mug/ml), respectively. The extract induced an apoptosis in AGS cells inference from the externalization of the phosphatidylserine, the increase of the sub G0/G1 content (%) and the apoptotic morphological changes including membrane blebbing, the formation of apoptotic bodies and chromatin condensation. In order to identify active substances causing the apoptosis, we further isolated major compounds present in Saussurea salicifolia and 7 compounds were isolated including a sesquiterpene lactone, cynaropicrin, 3 lignans (trachelogenin, matairesinol and arctigenin) and 3 lignan glycosides (tracheloside, matairesinoside and arctiin). In general the lignan aglycones were more cytotoxic than their lignan glycosides in both AGS cells and Hepa 1c1c7 cells. Cynaropicrin not only showed the most potent cytotoxicity among the 7 major compounds but also it induced an apoptosis and a weak G2/M arrest in AGS cells. Arctigenin had the second-best cytotoxicity among 7 major compounds, and induced an apoptosis. In order to evaluate the induction of the phase II detoxification enzyme, we measured the induction of quinone reductase activity of the extract, fractions and compounds in Hepa 1c1c7 cells. The ethyl acetate fraction and arctigenin showed the strongest cancer chemopreventive activity (chemoprevention index=9.88 and 7.57, respectively). These data suggest that the extract as well as the lignan compounds (especially arctigenin) originated from Saussurea salicifolia may be served as potential cancer chemopreventive agents for prevention or treatment of human cancers.

The chemopreventive effect of taxifolin is exerted through ARE-dependent gene regulation.

Phase II detoxification enzymes are responsible for the detoxification and elimination of activated carcinogens, and thus act as important biomarkers for chemoprevention. In this study, we tested the chemopreventive activity of taxifolin, a flavanon compound purified from a mongolian medicinal plant, by measuring quinone reductase (QR) activity in HCT 116 cells. Taxifolin induced significant QR activity, but displayed relatively low cytotoxicity in cells (chemoprevention index=5.75). To identify the target genes regulated by taxifolin, DNA microarray was performed with a 3K human cancer chip containing 3096 human genes associated with carcinogenesis. Significant analysis of microarray (SAM) revealed 428 differentially expressed (DE) genes as statistically significant, with a false discovery rate (FDR) of 57.2% (delta=0.3366). Sixty-five genes, including a few detoxification enzymes (NQO1, GSTM1) and an antioxidant enzyme (TXNRD1), were up-regulated and 363 genes were down-regulated in the presence of 60 microM taxifolin. In view of the finding that selected genes of interest contained antioxidant response element (ARE), we hypothesize that taxifolin modulates chemopreventive genes through activation of the ARE. Transient transfection experiments using the ARE QR-CAT construct demonstrate that taxifolin significantly activates ARE, but not xenobiotic response element (XRE). In conclusion, taxifolin acts as a potential chemopreventive agent by regulating genes via an ARE-dependent mechanism.

The antimicrobial activity of essential oil from Dracocephalum foetidum against pathogenic microorganisms.

A number of essential oils from Mongolian aromatic plants are claimed to have antimicrobial activities. The essential oil of Dracocephalum foetidum, a popular essential oil used in Mongolian traditional medicine, was examined for its antimicrobial activity. Eight human pathogenic microorganisms including B. subtilis, S. aureus, M. lutens, E. hirae, S. mutans, E. coli, C. albicans, and S. cerevisiae were examined. The essential oil of Dracocephalum foetidum exhibited strong antimicrobial activity against most of the pathogenic bacteria and yeast strains that were tested; by both the agar diffusion method and the minimum inhibitory concentration (MIC) assay (MIC range was 26-2592 microg/ml). Interestingly, Dracocephalum foetidum even showed antimicrobial activity against methicillin-resistant Staphylococcus aureus (MRSA) strains. We also analyzed the chemical composition of the oil by GC-MS and identified several major components, including n-Mentha-1,8-dien-10-al, limonene, geranial, and neral.