Analysis method of cellular stress caused by intermediate dose-rate irradiation using a cell lysate array technique.

Ionizing radiation damages DNA and may lead to the development of cancer. Irradiation also generates reactive oxygen species (ROS) which cause damage to various biological molecules. Relatively low dose-rate irradiation causes less damage. However, the damage and its effects on cell fate are difficult to evaluate. To develop a method to analyze the damage and accompanying changes in physiology in cells irradiated by γ-rays at a relatively low dose-rate, we used the protein array technique to quantify marker proteins involved in the stress response and the regulation of cell growth and death. This method enabled efficient analyses of many replicates of experimental data on cell lysate samples. We detected relatively small changes in the levels of these proteins in the irradiated cells. Changes in protein levels suggested ROS production and DNA damage as well as cell cycle retardation and the progression of cellular senescence. Thus, our approach shows promise for analyzing the biological effects of relatively low dose-rate irradiation.

4-O-Methylascochlorin-Mediated BNIP-3 Expression Controls the Balance of Apoptosis and Autophagy in Cervical Carcinoma Cells.

4-O-methylascochlorin (MAC) is a 4-fourth carbon-substituted derivative of ascochlorin, a compound extracted from a phytopathogenic fungus Ascochyta viciae. MAC induces apoptosis and autophagy in various cancer cells, but the effects of MAC on apoptosis and autophagy in cervical cancer cells, as well as how the interaction between apoptosis and autophagy mediates the cellular anticancer effects are not known. Here, we investigated that MAC induced apoptotic cell death of cervical cancer cells without regulating the cell cycle and promoted autophagy by inhibiting the phosphorylation of serine-threonine kinase B (Akt), mammalian target of rapamycin (mTOR), and 70-kDa ribosomal protein S6 kinase (p70S6K). Additional investigations suggested that Bcl-2/adenovirus E1B 19 kDa protein-interacting protein 3 (BNIP-3), but not Hypoxia-inducible factor 1 alpha (HIF-1α), is a key regulator of MAC-induced apoptosis and autophagy. BNIP-3 siRNA suppressed MAC-induced increases in cleaved- poly (ADP-ribose) polymerase (PARP) and LC3II expression. The pan-caspase inhibitor Z-VAD-FMK suppressed MAC-induced cell death and enhanced MAC-induced autophagy. The autophagy inhibitor chloroquine (CQ) enhanced MAC-mediated cell death by increasing BNIP-3 expression. These results indicate that MAC induces apoptosis to promote cell death and stimulates autophagy to promote cell survival by increasing BNIP-3 expression. This study also showed that co-treatment of cells with MAC and CQ further enhanced the death of cervical cancer cells.

4-O-methylascochlorin-stimulated HIF-1α expression induces the epithelial mesenchymal transition and cell survival in breast cancer cells.

4-O-Methyl-ascochlorin (MAC), a derivative of the prenyl-phenol antibiotic ascochlorin, promotes accumulation of HIF-1α. In this study, we investigated the molecular mechanisms of the effect of MAC on cell migration and mesenchymal epithelial transition (EMT) processes in breast cancer cells. MAC upregulated cell motility and migration regardless of cell viability, and promoted EMT features by regulating EMT-related proteins and transcription. In addition, the MAC-induced increase in the EMT was closely related to activation of HIF-1α expression. However, the MAC-induced EMT was not associated with AMPK phosphorylation or intracellular ROS, which stimulate HIF-1α expression. Similarly, HIF-1α-mediated autophagy induced by MAC was not related to EMT-related proteins. Inhibition of HIF-1α activity inhibited MAC-stimulated cell migration and increased MAC-induced cell death, indicating that HIF-1α activation is important for MAC-mediated cell migration and survival in breast cancer cells. Together, these results suggest that MAC can be used to investigate the link between HIF-1α activation and other oncogenes or tumor suppressors in breast cancer cells.

4-O-methylascochlorin attenuates inflammatory responses induced by lipopolysaccharide in RAW 264.7 macrophages.

Inflammation is implicated in various diseases, such as inflammatory bowel disease and cancer. Ascochlorin (ASC) and its derivatives have been shown to modulate inflammatory responses in many previous studies. However, the effects of 4-O-methylascochlorin (MAC), one of the ASC derivatives, on inflammatory responses have yet to be reported. In addition, the consequences of chemical modification of ASC on protein signaling and immunity have yet to be fully understood. The fourth carbon in MAC is methylated, which may result in modulation of immune response differently compared with ASC. Hence, we have investigated the role of MAC in inflammatory response induced by lipopolysaccharide in murine macrophage cells. Here, we found that MAC treatment decreased the inflammatory response by murine macrophages. When murine macrophages were treated with MAC, the transcription and translation of various pro-inflammatory indicators such as iNOS and COX-2 decreased. In addition, the ELISA results showed that the expression of TNF-α, IL-6, and IL-1ß, which are pro-inflammatory cytokines, was successfully decreased by MAC. Such effects of MAC appear to be mediated via downregulation of MAPK signaling and the transactivational activity of NF-κB. Lipopolysaccharide upregulates MAPK protein phosphorylation and NF-κB translocation, which in turn enhances the transactivation of genes related to NF-κB. Such results of lipopolysaccharide were attenuated by MAC. Collectively, our results indicate that MAC alleviated the inflammatory responses induced by lipopolysaccharide in murine macrophages successfully by modulating MAPK signaling pathway and NF-κB-related genes. This study shows that MAC, similar to other ASC derivatives, can potentially be used therapeutically to reduce the harmful damage induced by prolonged inflammation. In addition, the structural differences between ASC and its derivatives as well as their effect on intracellular signaling will also be discussed.

Ascofuranone suppresses invasion and F-actin cytoskeleton organization in cancer cells by inhibiting the mTOR complex 1 signaling pathway.

PURPOSE: Ascofuranone is an antiviral antibiotic that is known to exert multiple anti-tumor effects, including cell cycle arrest, inhibition of mitochondrial respiration, and inhibition of angiogenesis. In this study, we investigated the molecular mechanisms underlying the anti-metastatic effects of ascofuranone in insulin-like growth factor-I (IGF-1)-responsive cancer cells. METHODS: The inhibitory effect of ascofuranone on cancer cell migration and invasion was assessed using scratch wound healing and Matrigel invasion assays, respectively. F-actin cytoskeleton organization was assessed using FITC conjugated phalloidin staining. Target gene expression was evaluated using Western blotting and gene silencing was performed using siRNA transfections. Finally, the anti-metastatic effect of ascofuranone was investigated in vivo. RESULTS: We found that ascofuranone suppressed IGF-1-induced cell migration, invasion and motility in multiple cancer cell lines. The effects of ascofuranone on actin cytoskeleton organization were found to be mediated by suppression of the mTOR/p70S6K/4EBP1 pathway. Ascofuranone inhibited IGF-1-induced mTOR phosphorylation and actin cytoskeleton organization via upregulation of AMPK and downregulation of Akt phosphorylation. It also selectively suppressed the IGF-1-induced mTOR complex (mTORC)1 by phosphorylation of Raptor, but did not affect mTORC2. Furthermore, we found that focal adhesion kinase (FAK) activation decreased in response to ascofuranone, rapamycin, compound C and wortmannin treatment. Finally, we found that ascofuranone suppressed phosphorylation of FAK and mTOR and dephosphorylation of Raptor in cancerous metastatic lung tissues in vivo. CONCLUSIONS: Our data indicate that ascofuranone suppresses IGF-1-induced cancer cell migration and invasion by blocking actin cytoskeleton organization and FAK activation through inhibition of the mTORC1 pathway, and reveal a novel anti-metastatic function of this compound.

4-O-methylascochlorin activates autophagy by activating AMPK and suppressing c-Myc in glioblastoma.

A prior study identified that 4-O-methylascochlorin (MAC), a methylated derivative of ascochlorin (ASC) from the fungus Ascochyta viciae, activates autophagy in leukemia cells by suppressing c-Myc phosphorylation. However, the effects of MAC on autophagy in other cancer cells remain unknown. In the present study, we demonstrated that MAC activated autophagy in human glioblastoma. MAC increased expression of autophagy-related proteins, such as LC3-II and Beclin-1. Moreover, MAC stimulated AMP-activated protein kinase (AMPK) phosphorylation and suppressed phosphorylation of the mTOR, p70S6K, and 4EBP1. The well-known AMPK activator metformin increased LC3-II levels, which were augmented by MAC cotreatment. AMPK knockdown decreased LC3-II levels and inhibited MAC activation of autophagy. Furthermore, MAC suppression of c-Myc expression activated autophagy. Treatment with the c-MYC inhibitor, 10058-FA, induced autophagy, as did c-Myc small interfering RNA knockdown. These effects were augmented by MAC cotreatment. Taken together, these findings indicated that MAC induces autophagy in human glioblastoma by activating AMPK signaling and inhibiting c-Myc protein expression in human glioblastoma.

Ascofuranone inhibits epidermal growth factor-induced cell migration by blocking epithelial-mesenchymal transition in lung cancer cells.

Ascofuranone, an isoprenoid antibiotic initially purified from a culture broth of Ascochyta viciae, has multiple anticancer effects. However, the impacts of ascofuranone on the epithelial-mesenchymal transition (EMT) and epidermal growth factor (EGF)-induced effects on human lung cancer cell lines have not been previously reported. Here, we show that ascofuranone exerts its anticancer effects by inhibiting the EGF-induced EMT and cell migration in human lung cancer cell lines. Ascofuranone significantly inhibited EGF-induced migration and invasion by lung cancer cells, and suppressed EGF-induced morphologic changes by regulating the expression of EMT-associated proteins. In addition, ascofuranone upregulated E-cadherin, and downregulated fibronectin, vimentin, Slug, Snail, and Twist. Inhibition of ERK/AKT/mTOR promoted EGF-induced E-cadherin downregulation and inhibited EGF-induced vimentin upregulation in response to ascofuranone, implying that inhibition of the EGF-induced EMT by ascofuranone was mediated by the ERK and AKT/mTOR pathways. Inhibition of c-Myc suppressed EGF-induced vimentin upregulation, suggesting the involvement of c-Myc. Collectively, these findings suggest that ascofuranone inhibits tumor growth by blocking the EGF-induced EMT through a regulatory mechanism involving ERK, AKT/mTOR, and c-Myc in lung cancer cells.

4-O-methylascochlorin stabilizes hypoxia-inducible factor-1 in a manner different from hydroxylase inhibition by iron chelating or substrate competition.

Hypoxia-inducible factor-1 (HIF-1) is a transcription factor that plays essential roles in human diseases including cancer. The synthetic ascochlorin derivative 4-O-methylascochlorin stabilizes HIF-1α protein, and activates its transcriptional activity, resulting to induce gene expression of its downstream targets such as VEGF and GLUT-1. Here, we quantified protein level of HIF-1α in human osteosarcoma U2OS cells treated with ascochlorin-related compounds and typical HIF-1α stabilizers to characterize properties of HIF-1α stabilization by 4-O-methylascochlorin. Structure-activity relationship studies suggested that the aromatic moiety and hydrophobic substitution of the 4'-hydroxyl group are important for HIF-1α stabilization by ascochlorin-related compounds. 4-O-Methylascochlorin-induced HIF-1α stabilization was suppressed by ascorbic acid and compound C, but not by Fe(II), whereas ascorbic acid only suppressed HIF-1α stabilization by dimethyloxaloylglycine, an analog of the HIF-1 hydroxylase substrate. Fe(II) completely suppressed iron chelator-induced stabilization. These results suggest that ascochlorin-related compounds stabilize HIF-1α in a manner distinct from iron chelating or substrate competition.

Ascochlorin induces caspase-independent necroptosis in LPS-stimulated RAW 264.7 macrophages.

ETHNOPHARMACOLOGICAL RELEVANCE: Plant-specific fungus of natural compound of Ascochyta viciae has traditionally been used in the treatment of sleeping sickness and tumors. The anti-tumor activities of the compounds obtained from Pisum sativum L were evaluated in this study. AIM OF THE STUDY: In this study, during the prolonged incubation, treatment of the LPS-stimulated tumor-like macrophage RAW 264.7 cells with ASC exhibited the shift of anti-inflammatory behavior to a type of necroptotic cell death named necroptosis. MATERIALS AND METHODS: Ascochlorin (ASC) purified from plant-specific fungus Ascochyta viciae is a natural compound with the trimethyl oxocyclohexyl structure and an anti-cancer and antibiotic agent. The fungus contributes to the Ascochyta blight disease complex of pea (Pisum sativum L). RAW 264.7 cells have been stimulated with LPS and treated with ASC. Cell viability of the LPS-treated RAW 264.7 cells and bone marrow-derived macrophage (BMDM) cells were examined. Flow cytometry analysis with 7AAD and Annexin V was examined for the apoptotic or necroptosis/late-apoptosis. Cleaved caspase-3, -7 and -8 as well as cleaved PARP were assessed with a caspase inhibitor, z-VAD-fmk. LPS-responsible human leukemic U937 and colon cancer SW480 and HT-29 cells were also examined for the cell viabilities. RESULTS: Flow cytometry analysis after Annexin V and 7AAD double staining showed that ASC alone induces apoptosis in RAW 264.7 cells, while it induces necroptosis/late-apoptosis in LPS-treated RAW 264.7 cells. 7AAD and Annexin V positive populations were increased in the LPS-treated cells with ASC. Although viability of LPS-treated cells with ASC was decreased, the amounts of cleaved caspase-3, -7 and -8 as well as cleaved PARP were reduced when compared with ASC-treated cells. Upon ASC treatment, the cleaved caspase-8 level was not changed, however, cleaved caspase-3, -7, and PARP were reduced in LPS-stimulated RAW 264.7 cells treated with ASC, claiming a caspase-8 independent necroptosis of ASC. Furthermore, ASC and LPS-cotreated cells which a caspase inhibitor, z-VAD-fmk, was pretreated, showed the decreased cell viability compared with control cells without the inhibitor. Cell viability of RAW 264.7 cells co-treated with ASC and LPS when treated with z-VAD was decreased. In the LPS-responsible human leukemic U937 and colon cancer SW480 and HT-29 cells, cell viabilities were decreased by 10 µM ASC. CONCLUSION: Prolonged stimulation of ASC with LPS induces the necroptosis in RAW cells. Activated immune cells may share the susceptibility of antitumor agents with the cancer cells.

[Vinorelbine, a Microtubule Toxin, Induces Apoptosis and Polyploidy in MX-1, a Human Triple-Negative Breast Cancer Cell Line].

Compared to other types of breast cancers, triple-negative breast cancer(TNBC)has poor prognosis. However, much work has been done towards establishing an effective therapeutic strategy. Vinorelbine(VNB)is an effective therapeutic agent for TNBC, however, the mechanism for its efficacy remains to be elucidated. We found that MX-1, a TNBC cell line, exhibits apoptosis and polyploidy upon VNB treatment. Neither apoptosis nor polyploidy were observed in other types of breast cancer cells upon VNB treatment. Furthermore, inhibitors of respiration, protein synthesis, and DNA synthesis suppressed apoptosis and polyploidy induced by VNB in MX-1 cells. Among microtubule toxins, clinically effective paclitaxel(PTX)and VNB had a greater effect than colchicine and nocodazole on polyploidy induction in MX-1 cells. These results suggest that VNB induces apoptosis in some types of TNBCs through the induction of polyploidy, which is, at least in part, the likely mechanism of its clinical efficacy.

4-O-Methylascochlorin inhibits the prolyl hydroxylation of hypoxia-inducible factor-1α, which is attenuated by ascorbate.

4-O-Methylascochlorin (MAC), a methylated derivative of ascochlorin, was previously shown to promote the accumulation of hypoxia-inducible factor (HIF)-1α in human breast adenocarcinoma MCF-7 cells. In the present study, we further investigated the effects of MAC on the expression and function of HIF-1α in human fibrosarcoma HT-1080 cells. MAC promoted the accumulation of the HIF-1α protein without affecting its constitutive mRNA expression and augmented the transcriptional activation of HIF target genes. Ascorbate, but not N-acetylcysteine, attenuated MAC-mediated HIF-1α accumulation. MAC-induced increases in HIF-1α transcriptional activity were also attenuated by ascorbate. MAC inhibited the hydroxylation of HIF-1α at the proline 564 residue, while it was reversed by ascorbate. MAC slightly decreased the intracellular concentration of ascorbate. The present results demonstrated that MAC promoted the accumulation of HIF-1α by preventing prolyl hydroxylation, and ascorbate attenuated the MAC-mediated inhibition of HIF-1α prolyl hydroxylation.

Upregulation of AMPK by 4-O-methylascochlorin promotes autophagy via the HIF-1α expression.

4-O-methylascochlorin (MAC) is a derivative of ascochlorin, a prenyl-phenol compound antibiotic isolated from the fungus Ascochyta viciae. MAC induces caspase/poly (ADP-ribose) polymerase-mediated apoptosis in leukemia cells. However, the effects of MAC on autophagy in cancer cells and the underlying molecular mechanisms remain unknown. Here, we show that MAC induces autophagy in lung cancer cells. MAC significantly induced the expression of autophagy marker proteins including LC3-II, Beclin1, and ATG7. MAC promoted AMP-activated protein kinase (AMPK) phosphorylation and inhibited the phosphorylation of mammalian target of rapamycin (mTOR) and its downstream signalling proteins P70S6K and 4EBP1. The AMPK activator AICAR upregulated LC3-II expression through the AMPK/mTOR pathway similar to the effects of MAC. MAC-induced LC3-II protein expression was slightly reduced in AMPK siRNA transfected cells. MAC upregulated hypoxia-inducible factor-1α (HIF-1α) and BNIP3, which are HIF-1α-dependent autophagic proteins. Treatment with CoCl2 , which mimics hypoxia, induced autophagy similar to the effect of MAC. The HIF-1α inhibitor YC-1 and HIF-1α siRNA inhibited the MAC-induced upregulation of LC3-II and BNIP3. These results suggest that MAC induces autophagy via the AMPK/mTOR signalling pathway and by upregulating HIF-1α and BNIP3 protein expression in lung cancer cells.

Suppression of c-Myc enhances p21WAF1/CIP1 -mediated G1 cell cycle arrest through the modulation of ERK phosphorylation by ascochlorin.

Numerous anti-cancer agents inhibit cell cycle progression via a p53-dependent mechanism; however, other genes such as the proto-oncogene c-Myc are promising targets for anticancer therapy. In the present study, we provide evidence that ascochlorin, an isoprenoid antibiotic, is a non-toxic anti-cancer agent that induces G1 cell cycle arrest and p21WAF1/CIP1 expression by downregulating of c-Myc protein expression. Ascochlorin promoted the G1 arrest, upregulated p53 and p21WAF1/CIP1 , and downregulated c-Myc in HCT116 cells. In p53-deficient cells, ascochlorin enhanced the expression of G1 arrest-related genes except p53. Small interfering RNA (siRNA) mediated c-Myc silencing indicated that the transcriptional repression of c-Myc was related to ascochlorin-mediated modulation of p21WAF1/CIP1 expression. Ascochlorin suppressed the stabilization of the c-Myc protein by inhibiting ERK and P70S6K/4EBP1 phosphorylation, whereas it had no effect on c-Myc degradation mediated by PI3K/Akt/GSK3ß. The ERK inhibitor PD98059 and siRNA-mediated ERK silencing induced G1 arrest and p21WAF1/CIP1 expression by downregulating c-Myc in p53-deficient cells. These results indicated that ascochlorin-induced G1 arrest is associated with the repression of ERK phosphorylation and c-Myc expression. Thus, we reveal a role for ascochlorin in inhibiting tumor growth via G1 arrest, and identify a novel regulatory mechanism for ERK/c-Myc.

Delayed Growth Suppression and Radioresistance Induced by Long-Term Continuous Gamma Irradiation.

Biological response to ionizing radiation depends not only on the type of radiation and dose, but also on the duration and dose rate of treatment. For a given radiation dose, the biological response may differ based on duration and dose rate. We studied the properties of two human cell lines, M059K glioma and U2OS osteosarcoma, continuously exposed to γ rays for long time periods of more than five months. Growth inhibition in both cell lines was dependent on total dose when exposed to acute radiation over several minutes, whereas prolonged growth inhibition was dependent on dose rate after continuous irradiation over several months. The minimum dose rate for growth inhibition was 53.6 mGy/h. Cell cycle analysis showed G1 phase accumulation in cell populations continuously exposed to γ rays, and G2 phase accumulation in cells acutely exposed to high-dose-rate γ rays. Cells continuously exposed to γ rays continued to exhibit delayed growth suppression even after one month in an environment of background radiation, and maintained a high-level expression of c-Jun and its phosphorylation forms, as well as resistance to apoptosis induced by staurosporine and chemotherapeutic agents. These delayed effects were not observed in cells acutely exposed to 5 Gy of radiation. These results suggest that optimization of the irradiation schedule is crucial for risk estimation, protection and therapeutic utilization of ionizing radiation.

Molecular Targets of Ascochlorin and Its Derivatives for Cancer Therapy.

Cancer is an extremely complex disease comprising of a multitude of characteristic hallmarks that continue to evolve with time. At the genomic level, random mutations leading to deregulation of diverse oncogenic signal transduction cascades and polymorphisms coupled with environmental as well as life style-related factors are major causative agent contributing to chemoresistance and the failure of conventional therapies as well as molecular targeted agents. Hence, there is an urgent need to identify novel alternative therapies based on alternative medicines to combat this dreaded disease. Ascochlorin (ASC), an isoprenoid antibiotic isolated initially from the fermented broth of Ascochyta viciae, and its synthetic derivatives have recently demonstrated substantial antineoplastic effects in a variety of tumor cell lines and mouse models. The major focus of this review article is to briefly analyze the chemopreventive as well as therapeutic properties of ASC and its derivatives and to identify the multiple molecular targets modulated by this novel class of anticancer agent.

Ascofuranone inhibits lipopolysaccharide-induced inflammatory response via NF-kappaB and AP-1, p-ERK, TNF-α, IL-6 and IL-1ß in RAW 264.7 macrophages.

The natural fungal compound ascofuranone (5-chloro-3-[(2E,6E)-7-[(2S)-5,5-dimethyl-4-oxo-tetrahydrofuran-2-yl]-3-methyl-octa-2,6-dienyl]-2,4-dihydroxy-6-methyl-benzaldehyde, MW 420.93) (AF) isolated from Ascochyta viciae has been known to promote cell cycle arrest and inhibit invasion of tumor cells. We have previously studied a structurally similar compound ascochlorin (ASC; MW 404.93) with regard to its anti-inflammatory activity in LPS- stimulated RAW 264.7 macrophages. In order to examine the relationship between the anti-inflammatory activities and the molecular differences between AF and ASC, the activity of AF is herein studied, because ASC has a unique trimethyl oxocyclohexyl structure, while AF has a unique dimethyl-oxo-tetrahydrofuran structure. AF dose-dependently inhibited the production of NO and iNOS and the COX-2 mRNA and protein levels in RAW 264.7 cells. In addition, AF suppressed mRNA expression levels of inflammatory cytokines such as TNF-α, IL-6, and IL-1ß, as assessed by RT-PCR. AF (30-50 µg/ml) treatment clearly inhibited the nuclear translocation of NF-κB, AP-1 (p-c-Jun) from the cytosolic space. Phosphorylation of IκB, which functions to maintain the activity of NF-κB, was decreased by AF treatment. Moreover, AF suppressed the binding of NF-κB (p65). Inhibition of IkBa phosphorylation and degradation inhibits nuclear translocation of p65. Immunofluorescence confocal microscopy analysis also revealed that translocation of NF-κB and AP-1 (p-c-Jun) was decreased upon AF treatment. AF specifically decreased the expression level of p-ERK, but not the expression level of p-p38 or p-JNK. Given these results, we suggest that AF suppresses the inflammatory response by targeting p-ERK. This indicates that AF is a negative regulator of LPS-stimulated nuclear translocation of NF-κB and AP-1 (p-c-Jun) in RAW 264.7 macrophages, and specifically it targets p-ERK. Therefore, AF and ASC exert their effects in different ways, most probably because their structural differences allow for specific recognition and inhibition of their target MAPKs. Our results further suggest that AF could be a natural bioactive compound useful for treating inflammation-mediated pathological diseases.

Ascochlorin Enhances the Sensitivity of Doxorubicin Leading to the Reversal of Epithelial-to-Mesenchymal Transition in Hepatocellular Carcinoma.

Increasing evidence has indicated that epithelial-to-mesenchymal transition (EMT) at the advanced stage of liver cancer not only has the ability to self-renew and progress cancer, but also enables greater resistance to conventional chemo- and radiotherapies. Here, we report that ascochlorin (ASC), an isoprenoid antibiotic, could potentiate the cytotoxic effect of doxorubicin on HCCLM3, SNU387, SNU49, and SK-Hep-1 hepatocellular carcinoma cells, which had a predominantly mesenchymal signature with low expression of E-cadherin but high expression of N-cadherin. Co-administration of ASC reduced doxorubicin-induced invasion/migration and modulated EMT characteristics in mesenchymal cells. This process was probably mediated by the E-cadherin repressors Snail and Slug. In addition, ASC increased sensitivity to doxorubicin treatment by directly inhibiting STAT3 binding to the Snail promoter. We also observed that ASC significantly enhanced the effect of doxorubicin against tumor growth and inhibited metastasis in an HCCLM3_Luc orthotopic mouse model. Collectively, our data demonstrate that ASC can increase sensitivity to doxorubicin therapy and reverse the EMT phenotype via the downregulation of STAT3-Snail expression, which could form the basis of a novel therapeutic approach against hepatocellular carcinoma. Mol Cancer Ther; 15(12); 2966-76. ©2016 AACR.

Suppression of c-Myc induces apoptosis via an AMPK/mTOR-dependent pathway by 4-O-methyl-ascochlorin in leukemia cells.

4-O-Methyl-ascochlorin (MAC) is a methylated derivative of the prenyl-phenol antibiotic ascochlorin, which was isolated from an incomplete fungus, Ascochyta viciae. Although the effects of MAC on apoptosis have been reported, the underlying mechanisms remain unknown. Here, we show that MAC promoted apoptotic cell death and downregulated c-Myc expression in K562 human leukemia cells. The effect of MAC on apoptosis was similar to that of 10058-F4 (a c-Myc inhibitor) or c-Myc siRNA, suggesting that the downregulation of c-Myc expression plays a role in the apoptotic effect of MAC. Further investigation showed that MAC downregulated c-Myc by inhibiting protein synthesis. MAC promoted the phosphorylation of AMP-activated protein kinase (AMPK) and inhibited the phosphorylation of mammalian target of rapamycin (mTOR) and its target proteins, including p70S6 K and 4E-BP-1. Treatment of cells with AICAR (an AMPK activator), rapamycin (an mTOR inhibitor), or mTOR siRNA downregulated c-Myc expression and induced apoptosis to a similar extent to that of MAC. These results suggest that the effect of MAC on apoptosis induction in human leukemia cells is mediated by the suppression of c-Myc protein synthesis via an AMPK/mTOR-dependent mechanism.

Anti-Inflammatory Effect of Ascochlorin in LPS-Stimulated RAW 264.7 Macrophage Cells Is Accompanied With the Down-Regulation of iNOS, COX-2 and Proinflammatory Cytokines Through NF-κB, ERK1/2, and p38 Signaling Pathway.

A natural compound C23 H32 O4 Cl, ascochlorin (ASC) isolated from an incomplete fungus, Ascochyta viciae has been known to have several biological activities as an antibiotic, antifungal, anti-cancer, anti-hypolipidemic, and anti-hypertension agent. In this study, anti-inflammatory activity has been investigated in lipopolysaccharide (LPS)-induced murine macrophage RAW 264.7 cells, since ASC has not been observed on the inflammatory events. The present study has clearly shown that ASC (1-50 µM) significantly suppressed the production of nitric oxide (NO) and prostaglandin E2 (PGE2 ) and decreased the gene expression of inducible NO synthase (iNOS) and cyclooxygenase-2 (COX-2) in a dose-dependent manner. Moreover, ASC inhibited the mRNA expression and the protein secretion of interleukin (IL)-1ß and IL-6 but not tumor necrosis factor (TNF)-α in LPS-stimulated RAW 264.7 macrophage cells. In addition, ASC suppressed nuclear translocation and DNA binding affinity of nuclear factor-κB (NF-κB). Furthermore, ASC down-regulated phospho-extracellular signal-regulated kinase 1/2 (p-ERK1/2) and p-p38. These results demonstrate that ASC exhibits anti-inflammatory effects in RAW 264.7 macrophage cells.