Jeong-Hyeon Ko

Ginkgolic Acid Inhibits Invasion and Migration and TGF-β-Induced EMT of Lung Cancer Cells Through PI3K/Akt/mTOR Inactivation

Epithelial‐to‐mesenchymal transition (EMT) is a critical cellular phenomenon regulating tumor metastases. In the present study, we investigated whether ginkgolic acid can affect EMT in lung cancer cells and the related underlying mechanism(s) of its actions. We found that ginkgolic acid C15:1 (GA C15:1) inhibited cell proliferation, invasion, and migration in both A549 and H1299 lung cancer cells. GA C15:1 also suppressed the expression of EMT related genes (Fibronectin, Vimentin, N‐cadherin, MMP‐9, MMP‐2, Twist and Snail) and suppressed TGF‐β‐induced EMT as assessed by reduced expression of mesenchymal markers (Fibronectin, Vimentin, N‐cadherin), MMP‐9, MMP‐2, Twist and Snail. However, GA C15:1 did not affect the expression of various epithelial marker proteins (Occludin and E‐cadherin) in both A549 and H1299 cells. TGF‐β‐induced morphologic changes from epithelial to mesenchymal cells and induction of invasion and migration were reversed by GA C15:1. Finally, GA C15:1 not only abrogated basal PI3K/Akt/mTOR signaling cascade, but also reduced TGF‐β‐induced phosphorylation of PI3K/Akt/mTOR pathway in lung cancer cells. Overall, these findings suggest that GA C15:1 suppresses lung cancer invasion and migration through the inhibition of PI3K/Akt/mTOR signaling pathway and provide a source of potential therapeutic compounds to control the metastatic dissemination of tumor cells. J. Cell. Physiol. 232: 346–354, 2017.

Resveratrol inhibits STAT3 signaling pathway through the induction of SOCS-1: Role in apoptosis induction and radiosensitization in head and neck tumor cells.

BACKGROUND Signal transducer and activator of transcription 3 (STAT3) is persistently activated in squamous cell carcinoma of the head and neck (SCCHN) and can cause uncontrolled cellular proliferation and division. HYPOTHESIS Thus, its targeted abrogation could be an effective strategy to reduce the risk of SCCHN. Resveratrol is known for its anti-cancer efficacy in a variety of cancer models. STUDY DESIGN The effect resveratrol on STAT3 activation, associated protein kinases, phosphatases, cellular proliferation and apoptosis was investigated. METHODS We evaluated the effect of resveratrol on STAT3 signaling cascade and its regulated functional responses in SCCHN cells. RESULTS We found that HN3 and FaDu cells expressed strongly phosphorylated STAT3 on both tyrosine 705 and serine 727 residues as compared to other SCCHN cells. The phosphorylation was completely suppressed by resveratrol in FaDu cells, but not substantially in HN3 cells. STAT3 suppression was mediated through the inhibition of activation of upstream JAK2, but not of JAK1 and Src kinases. Treatment with the protein tyrosine phosphatase (PTP) inhibitor pervanadate reversed the resveratrol-induced down-regulation of STAT3, thereby indicating a critical role for a PTP. We also found that resveratrol induced the expression of the SOCS-1 protein and mRNA. Further, deletion of SOCS-1 gene by siRNA suppressed the induction of SOCS-1, and reversed the inhibition of STAT3 activation. Resveratrol down-regulated various STAT3-regulated gene products, inhibited proliferation, invasion, as well as induced the cell accumulation in the sub-G1 phase and caused apoptosis. Beside, this phytoalexin also exhibited the enhancement of apoptosis when combined with ionizing radiation treatment. CONCLUSION Our results suggest that resveratrol blocks STAT3 signaling pathway through induction of SOCS-1, thus attenuating STAT3 phosphorylation and proliferation in SCCHN cells.

Ginkgolic Acid C 17:1, Derived from Ginkgo biloba Leaves, Suppresses Constitutive and Inducible STAT3 Activation through Induction of PTEN and SHP-1 Tyrosine Phosphatase

Ginkgolic acid C 17:1 (GAC 17:1) extracted from Ginkgo biloba leaves, has been previously reported to exhibit diverse antitumor effect(s) through modulation of several molecular targets in tumor cells, however the detailed mechanism(s) of its actions still remains to be elucidated. Signal transducer and activator of transcription 3 (STAT3) is an oncogenic transcription factor that regulates various critical functions involved in progression of diverse hematological malignancies, including multiple myeloma, therefore attenuating STAT3 activation may have a potential in cancer therapy. We determined the anti-tumor mechanism of GAC 17:1 with respect to its effect on STAT3 signaling pathway in multiple myeloma cell lines. We found that GAC 17:1 can inhibit constitutive activation of STAT3 through the abrogation of upstream JAK2, Src but not of JAK1 kinases in U266 cells and also found that GAC can suppress IL-6-induced STAT3 phosphorylation in MM.1S cells. Treatment of protein tyrosine phosphatase (PTP) inhibitor blocked suppression of STAT3 phosphorylation by GAC 17:1, thereby indicating a critical role for a PTP. We also demonstrate that GAC 17:1 can induce the substantial expression of PTEN and SHP-1 at both protein and mRNA level. Further, deletion of PTEN and SHP-1 genes by siRNA can repress the induction of PTEN and SHP-1, as well as abolished the inhibitory effect of drug on STAT3 phosphorylation. GAC 17:1 down-regulated the expression of STAT3 regulated gene products and induced apoptosis of tumor cells. Overall, GAC 17:1 was found to abrogate STAT3 signaling pathway and thus exert its anticancer effects against multiple myeloma cells.

The Role of Resveratrol in Cancer Therapy

Natural product compounds have recently attracted significant attention from the scientific community for their potent effects against inflammation-driven diseases, including cancer. A significant amount of research, including preclinical, clinical, and epidemiological studies, has indicated that dietary consumption of polyphenols, found at high levels in cereals, pulses, vegetables, and fruits, may prevent the evolution of an array of diseases, including cancer. Cancer development is a carefully orchestrated progression where normal cells acquires mutations in their genetic makeup, which cause the cells to continuously grow, colonize, and metastasize to other organs such as the liver, lungs, colon, and brain. Compounds that modulate these oncogenic processes can be considered as potential anti-cancer agents that may ultimately make it to clinical application. Resveratrol, a natural stilbene and a non-flavonoid polyphenol, is a phytoestrogen that possesses anti-oxidant, anti-inflammatory, cardioprotective, and anti-cancer properties. It has been reported that resveratrol can reverse multidrug resistance in cancer cells, and, when used in combination with clinically used drugs, it can sensitize cancer cells to standard chemotherapeutic agents. Several novel analogs of resveratrol have been developed with improved anti-cancer activity, bioavailability, and pharmacokinetic profile. The current focus of this review is resveratrol’s in vivo and in vitro effects in a variety of cancers, and intracellular molecular targets modulated by this polyphenol. This is also accompanied by a comprehensive update of the various clinical trials that have demonstrated it to be a promising therapeutic and chemopreventive agent.

Capsazepine inhibits JAK/STAT3 signaling, tumor growth, and cell survival in prostate cancer

Persistent STAT3 activation is seen in many tumor cells and promotes malignant transformation. Here, we investigated whether capsazepine (Capz), a synthetic analogue of capsaicin, exerts anticancer effects by inhibiting STAT3 activation in prostate cancer cells. Capz inhibited both constitutive and induced STAT3 activation in human prostate carcinoma cells. Capz also inhibited activation of the upstream kinases JAK1/2 and c-Src. The phosphatase inhibitor pervanadate reversed Capz-induced STAT3 inhibition, indicating that the effect of Capz depends on a protein tyrosine phosphatase. Capz treatment increased PTPε protein and mRNA levels. Moreover, siRNA-mediated knockdown of PTPε reversed the Capz-induced induction of PTPε and inhibition of STAT3 activation, indicating that PTPε is crucial for Capz-dependent STAT3 dephosphorylation. Capz also decreased levels of the protein products of various oncogenes, which in turn inhibited proliferation and invasion and induced apoptosis. Finally, intraperitoneal Capz administration decreased tumor growth in a xenograft mouse prostate cancer model and reduced p-STAT3 and Ki-67 expression. These data suggest that Capz is a novel pharmacological inhibitor of STAT3 activation with several anticancer effects in prostate cancer cells.

Embelin Inhibits Invasion and Migration of MDA-MB-231 Breast Cancer Cells by Suppression of CXC Chemokine Receptor 4, Matrix Metalloproteinases-9/2, and Epithelial-Mesenchymal Transition.

Embelin (EB) is a benzoquinone derivative isolated from Embelia ribes Burm plant. Recent scientific evidence shows that EB induces apoptosis and inhibits migration and invasion in highly metastatic human breast cancer cells. However, the exact mechanisms of EB in tumor metastasis and invasion have not been fully elucidated. Here, we investigated the underlying mechanisms of antimetastatic activities of EB in breast cancer cells. The EB downregulated the chemokine receptor 4 (CXCR4) as well as matrix metalloproteinase (MMP)‐9/2 expression and upregulated the tissue inhibitor of metalloproteinase 1 expression in MDA‐MB‐231 cells under noncytotoxic concentrations but not in MCF‐7 cells. Additionally, EB inhibited the CXC motif chemokine ligand 12 induced invasion and migration activities of MDA‐MB‐231 cells. A detailed study of underlying mechanisms revealed that the regulation of the downregulation of CXCR4 was at the transcriptional level, as indicated by the downregulation of mRNA expression and suppression of nuclear factor‐kappa B (NF‐κB) activation. It further reduced the binding of NF‐κB to the CXCR4 promoter. Besides, EB downregulated mesenchymal marker proteins (neural cadherin and vimentin) and concurrently upregulated epithelial markers (epithelial cadherin and occludin). Overall, these findings suggest that EB can abrogate breast cancer cell invasion and metastasis by suppression of CXCR4, MMP‐9/2 expressions, and inhibition of epithelial–mesenchymal transition and thus may have a great potential to suppress metastasis of breast cancer. Copyright

Ginkgetin Blocks Constitutive STAT3 Activation and Induces Apoptosis through Induction of SHP-1 and PTEN Tyrosine Phosphatases.

Ginkgetin, a biflavone from Ginkgo biloba leaves, is known to exhibit antiinflammatory, antifungal, neuroprotective, and antitumor activities, but its precise mechanism of action has not been fully elucidated. Because the aberrant activation of STAT3 has been linked with regulation of inflammation, proliferation, invasion, and metastasis of tumors, we hypothesized that ginkgetin modulates the activation of STAT3 in tumor cells. We found that ginkgetin clearly suppressed constitutive phosphorylation of STAT3 through inhibition of the activation of upstream JAK1 and c‐Src kinases and nuclear translocation of STAT3 on both A549 and FaDu cells. Treatment with sodium pervanadate reversed the ginkgetin‐induced down‐modulation of STAT3, thereby indicating a critical role for a PTP. We also found that ginkgetin strongly induced the expression of the SHP‐1 and PTEN proteins and its mRNAs. Further, deletion of SHP‐1 and PTEN genes by siRNA suppressed the induction of SHP‐1 and PTEN, and reversed the inhibition of STAT3 activation. Ginkgetin induced apoptosis as characterized by an increased accumulation of cells in subG1 phase, positive Annexin V binding, loss of mitochondrial membrane potential, down‐regulation of STAT3‐regulated gene products, and cleavage of PARP. Overall, ginkgetin abrogates STAT3 signaling pathway through induction of SHP‐1 and PTEN proteins, thus attenuating STAT3 phosphorylation and tumorigenesis. Copyright

Isorhynchophylline, a Potent Plant Alkaloid, Induces Apoptotic and Anti-Metastatic Effects in Human Hepatocellular Carcinoma Cells through the Modulation of Diverse Cell Signaling Cascades

Isorhynchophylline (Rhy) is an active pharmacological component of Uncaria rhynchophylla that has been reported previously to exert significant antihypertensive and neuroprotective effects. However, very little is known about its potential anti-cancer activities. This study was carried out to evaluate the anticancer effects of Rhy against various human carcinoma cell lines. We found that Rhy exhibited substantial cytotoxic effect against human hepatocellular carcinoma HepG2 cells when compared with other human carcinoma cell lines including those of lung, pancreas, prostate, head and neck, breast, multiple myeloma, brain and renal cell carcinoma. Rhy induced apoptosis as characterized by accumulation of cells in sub G1 phase; positive Annexin V binding; activation of caspase-8, -9, and -3; and cleavage of PARP (poly-ADP ribose polymerase). This effect of Rhy correlated with the down-regulation of various proteins that mediated cell proliferation, cell survival, metastasis, and angiogenesis. Moreover, cell proliferation, migration, and constitutive CXCR4 (C-X-C chemokine receptor type 4), MMP-9 (Matrix metallopeptidase-9), and MMP-2 expression were inhibited upon Rhy treatment. We further investigated the effect of Rhy on the oncogenic cell signaling cascades through phospho-kinase array profiling assay. Rhy was found to abrogate phospho-p38, ERK, JNK, CREB, c-Jun, Akt, and STAT3 signals, but interestingly enhanced phospho-p53 signal. Overall, our results indicate, for the first time, that Rhy could exert anticancer and anti-metastatic effects through regulation of multiple signaling cascades in hepatocellular carcinoma cells.

The Application of Embelin for Cancer Prevention and Therapy

Embelin is a naturally-occurring benzoquinone compound that has been shown to possess many biological properties relevant to human cancer prevention and treatment, and increasing evidence indicates that embelin may modulate various characteristic hallmarks of tumor cells. This review summarizes the information related to the various oncogenic pathways that mediate embelin-induced cell death in multiple cancer cells. The mechanisms of the action of embelin are numerous, and most of them induce apoptotic cell death that may be intrinsic or extrinsic, and modulate the NF-κB, p53, PI3K/AKT, and STAT3 signaling pathways. Embelin also induces autophagy in cancer cells; however, these autophagic cell-death mechanisms of embelin have been less reported than the apoptotic ones. Recently, several autophagy-inducing agents have been used in the treatment of different human cancers, although they require further exploration before being transferred from the bench to the clinic. Therefore, embelin could be used as a potential agent for cancer therapy.

Korean Red Ginseng Extract Enhances the Anticancer Effects of Sorafenib through Abrogation of CREB and c-Jun Activation in Renal Cell Carcinoma

Although application of sorafenib in the treatment of human renal cell carcinoma (RCC) remains one of the best examples of successful targeted therapy, majority of RCC patients suffer from its side effects as well as develop resistance to this targeted therapy. Thus, there is a need to promote novel alternative therapies for the treatment of RCC. In this study, we investigated whether Korean red ginseng extract (KRGE) could inhibit the proliferation and induce chemosensitization in human renal cancer cells. Also, we used a human phospho‐antibody array containing 46 antibodies against signaling molecules to examine a subset of phosphorylation events after KRGE and sorafenib combination treatment. Korean red ginseng extract suppressed the proliferation of two RCC cell lines; activated caspase‐3; caused poly(ADP‐ribose) polymerase cleavage; abrogated the expression of B‐cell lymphoma 2, B‐cell lymphoma extra large, survivin, inhibitors of apoptosis proteins‐1/2, cyclooxygenase‐2, cyclin D1, matrix metallopeptidase‐9, and vascular endothelial growth factor; and upregulated pro‐apoptotic gene products. Interestingly, KRGE enhanced the cytotoxic and apoptotic effects of sorafenib in RCC cells. The combination treatment of KRGE and sorafenib more clearly suppressed cyclic adenosine monophosphate response element‐binding protein and c‐Jun phosphorylation and induced phosphorylation of p53 than did the individual treatment regimen. Our results clearly demonstrate that KRGE can enhance the anticancer activity of sorafenib and may have a substantial potential in the treatment of RCC. Copyright