• 한국발생생물학회지:발생과생식
• /
• 제24권2호
• /
• pp.113-123
• /
• 2020

Metformin has been widely used as an antidiabetic drug, and reported to inhibit cell proliferation in many cancers including non-small cell lung cancer (NSCLC). In NSCLC cells, metformin suppresses PI3K/AKT/mTOR signaling pathway, but effect of metformin on RAS/RAF/MEK/ERK signaling pathway is controversial; several studies showed the inhibition of ERK activity, while others demonstrated the activation of ERK in response to metformin exposure. Metformin-induced activation of ERK is therapeutically important, since metformin could enhance cell proliferation through RAS/RAF/MEK/ERK pathway and lead to impairment of its anticancer activity suppressing PI3K/AKT/mTOR pathway, requiring blockade of both signaling pathways for more efficient antitumor effect. The present study tested the combination therapy of metformin and trametinib by monitoring the alterations of regulatory effector proteins of cell signaling pathways and the effect of the combination on cell viability in NCI-H2087 NSCLC cells with NRAS and BRAF mutations. We show that metformin alone blocks PI3K/AKT/mTOR signaling pathway but induces the activation and phosphorylation of ERK. The combination therapy synergistically decreased cell viability in treatment with low doses of two drugs, while it gave antagonistic effect with high doses. These findings suggest that the efficacy of metformin and trametinib combination therapy may depend on the alteration of ERK activity induced by metformin and specific cellular context of cancer cells.

• IMMUNE NETWORK
• /
• 제5권4호
• /
• pp.237-246
• /
• 2005

Background: Little information is available on the identification and characterization of the upstream regulators of the signal transduction cascades for Mycobacterium tuberculosis (M. tbc)-induced ERK 1/2 activation and chemokine expression. We investigated the signaling mechanisms involved in expression of CCL3 /MIP-1 and CCL4/MIP-1 in human primary monocytes infected with M. tbc. Methods: MAP kinase phosphorylation was determined using western blot analysis with specific primary antibodies (ERK 1/2, and phospho-ERK1/2), and the upstream signaling pathways were further investigated using specific inhibitors. Results: An avirulent strain, M. tbc H37Ra, induced greater and more sustained ERK 1/2 phosphorylation, and higher CCL3 and CCL4 production, than did M. tbc H37Rv. Specific inhibitors for mitogen-activated protein kinase (MAPK) kinase (MEK; U0126 and PD98059) significantly inhibited the expression of CCL3 and CCL4 in human monocytes. Mycobactetia-mediated expression of CCL3 and CCL4 was not inhibited by the Ras inhibitor manumycin A or the Raf-1 inhibitor GW 5074. On the other hand, phospholipase C (PLC) inhibitor (U73122) and protein kinase C (PKC)specific inhibitors ($G\ddot{o}6976$ and Ro31-8220) significantly reduced M. tbc-induced activation of ERK 1/2 and chemokine synthesis. Conclusion: These results are the first to demonstrate that the PLC-PKC-MEK-ERK, not the Ras-Raf-MEK-ERK, pathway is the major signaling pathway inducing M. tbc-mediated CCL3 and CCL4 expression in human primary monocytes.

• BMB Reports
• /
• 제47권12호
• /
• pp.685-690
• /
• 2014

The Ras/Raf/MEK/Erk signaling pathway is important for regulation of cell growth, proliferation, differentiation, survival, and apoptosis in response to a variety of extracellular stimuli. Lack of Erk MAPK activation is observed in several cancer cells despite active activation of Ras. However, little is known about the modulation of Erk1/2 activity by active Ras. Here, we show that overexpression of active H-Ras (H-RasG12R) in NIH3T3 fibroblasts impaired FGF2-induced Erk1/2 phosphorylation, as compared to wild-type cells. Northern blot analysis revealed that prolonged expression of active Ras increased MAP kinase phosphatase 3 (MKP3) mRNA expression, a negative regulator of Erk MAPK. Inhibition of the phosphatidylinositol 3-kinase (PI3K)/Akt pathway abrogated active Ras-induced up-regulation of MKP3 expression, leading to the rescue of Erk1/2 phosphorylation. Our results demonstrated that the Ras/Raf/MEK/Erk signaling cascade is negatively regulated by the PI3K/Aktdependent transcriptional activation of the MKP3 gene.

• BMB Reports
• /
• 제49권7호
• /
• pp.370-375
• /
• 2016

Ras oncoproteins are small molecular weight GTPases known for their involvement in oncogenesis, which operate in a complex signaling network with multiple effectors. Approximately 25% of human tumors possess mutations in a member of this family. The Raf1/MEK/Erk1/2 pathway is one of the most intensively studied signaling mechanisms. Different levels of regulation account for the inactivation of MAP kinases by MAPK phosphatases in a cell type- and stimuli-dependent manner. In the present study, using three inducible Ras-expressing NIH/3T3 cell lines, we demonstrated that MKP3 upregulation requires the activation of the Erk1/2 pathway, which correlates with the shutdown of this pathway. We also demonstrated, by applying pharmacological inhibitors and effector mutants of Ras, that induction of MKP3 at the protein level is positively regulated by the oncogenic Ras/Raf/MEK/Erk1/2 signaling pathway.

• Biomolecules & Therapeutics
• /
• 제22권6호
• /
• pp.503-509
• /
• 2014

Paraquat has been suggested to induce apoptosis by generation of reactive oxygen species (ROS). However, little is known about the mechanism of paraquat-induced apoptosis. Here, we demonstrate that extracellular signal-regulated protein kinase (ERK) is required for paraquat-induced apoptosis in NIH3T3 cells. Paraquat treatment resulted in activation of ERK, and U0126, inhibitors of the MEK/ERK signaling pathway, prevented apoptosis. Moreover, paraquat-induced apoptosis was associated with cytochrome C release, which could be prevented by treatment with the MEK inhibitors. Taken together, our findings suggest that ERK activation plays an active role in mediating paraquat-induced apoptosis of NIH3T3 cells.

• Natural Product Sciences
• /
• 제14권2호
• /
• pp.81-85
• /
• 2008

Isorhamnetin isolated from Oenanthe javanica significantly inhibited proliferation and collagen production in HSC-T6 cells in concentration- and time-dependent manners. Pretreatment of HSC-T6 cells with isorhamnetin significantly inhibited serum-induced ERK phosphorylation, in a similar manner as PD98059, a known MEK inhibitor. These results suggested that isorhamnetin reduced collagen production in HSC-T6 cells, in part, via inhibition of ERK signaling pathway.

• 한국식품영양학회지
• /
• 제28권4호
• /
• pp.579-585
• /
• 2015

Rutin은 메밀에 함유되어 있는 것으로 잘 알려져 있는 flavonoid 물질로서, 최근 연구들에서 rutin의 항염증 및 암예방 활성이 보고되어져 왔다. 그러나, rutin의 암예방 활성과 관련된 분자생물학적 기전에 대한 연구는 아직까지 미비한 실정이다. 따라서, 본 연구에서는 발암 과정 중 하나인 세포의 악성 변형을 EGF로 유도하여 rutin이 이를 억제하는지 여부를 확인하는 실험을 진행하였으며, 그 분자생물학적 기전을 규명하고자 하였다. Soft agar assay 실험 결과, rutin은 EGF로 유도된 세포의 악성 변형을 $25{\mu}M$, $50{\mu}M$, $100{\mu}M$에서 농도별로 감소시켰다. 또한 EGF로 유도된 MEK/ERK 및 MKK4/JNK 신호전달체계의 인산화를 저해하였다. 그러나 이와는 대조적으로 rutin은 EGF로 유도된 MKK3/6/p38 신호전달체계 인산화는 감소시키지 못하는 것으로 확인되었다. 이상의 연구결과들은 rutin이 암화 과정 중 발생되는 세포의 악성변형 과정을 촉진시킨다고 잘 알려져 있는 MEK/ERK 및 MKK4/JNK 신호전달체계의 활성화를 억제함으로써 암예방 활성을 나타낸다는 것을 제시하고 있으며, 이는 메밀의 생리활성 성분인 rutin의 암예방 생리 활성 소재로서의 이용 가능성을 보여주는 중요한 연구 결과라 할 수 있겠다. 또한 위 연구결과는 MEK/ERK 및 MKK4/JNK 신호전달 체계를 표적으로 하는 생리활성 소재 탐색에도 활용 가능할 것으로 생각되어진다.

• 한국발생생물학회지:발생과생식
• /
• 제15권1호
• /
• pp.1-7
• /
• 2011

It is suggested that FGF/Ras/MEK/Erk signaling plays crucial roles in specification and cell division of the mesodermal precursor cells in ascidian embryos. To investigate how the number of cell division in tissue precursor cells is determined, we have characterized Wee1 homolog, Hr-Wee1 of the ascidian Halocynthia roretzi. We found that the Hr-Wee1 mRNA is expressed both maternally and zygotically. Maternal transcript is localized to the cytoplasm in the animal cells, while zygotic expression is seen in cells of the endoderm lineage from 32-cell to 110-cell stages. Zygotic in situ signal is detected in the A-line neural plate cells of neurulae, and in epidermal cells of the head region of tailbud embryos. Embryos treated with MEK signaling inhibitor showed a similar pattern to normal embryos in expression of Hr-Wee1. Therefore, it is likely that MEK signaling does not affect the maternal and zygotic expression of Hr-Wee1.

• Asian Pacific Journal of Cancer Prevention
• /
• 제15권20호
• /
• pp.8539-8548
• /
• 2014

Mitogen-activated protein kinase (MAPK) is an important signaling pathway in living beings in response to extracellular stimuli. There are 5 main subgroups manipulating by a set of sequential actions: ERK(ERK1/ERK2), c-Jun N(JNK/SAPK), p38 MAPK($p38{\alpha}$, $p38{\beta}$, $p38{\gamma}$ and $p38{\delta}$), and ERK3/ERK4/ERK5. When stimulated, factors of upstream or downstream change, and by interacting with each other, these groups have long been recognized to be related to multiple biologic processes such as cell proliferation, differentiation, death, migration, invasion and inflammation. However, once abnormally activated, cancer may occur. Several components of the MAPK network have already been proposed as targets in cancer therapy, such as p38, JNK, ERK, MEK, RAF, RAS, and DUSP1. Among them, alteration of the RAS-RAF-MEK-ERK-MAPK(RAS-MAPK) pathway has frequently been reported in human cancer as a result of abnormal activation of receptor tyrosine kinases or gain-of-function mutations in genes. The reported roles of MAPK signaling in apoptotic cell death are controversial, so that further in-depth investigations are needed to address these controversies. Based on an extensive analysis of published data, the goal of this review is to provide an overview on recent studies about the mechanism of MAP kinases, and how it generates certain tumors, as well as related treatments.

• 한국발생생물학회지:발생과생식
• /
• 제17권4호
• /
• pp.389-397
• /
• 2013

FGF9/16/20 signaling pathway specify the developmental fates of notochord, mesenchyme, and neural cells in ascidian embryos. Although a conserved Ras/MEK/Erk/Ets pathway is known to be involved in this signaling, the detailed mechanisms of regulation of FGF signaling pathway have remained largely elusive. In this study, we have isolated Hr-Erf, an ascidian orthologue of vertebrate Erf, to elucidate interactions of transcription factors involved in FGF signaling of the ascidian embryo. The Hr-Erf cDNA encompassed 3110 nucleotides including sequence encoded a predicted polypeptide of 760 amino acids. The polypeptide had the Ets DNA-binding domain in its N-terminal region. In adult animals, Hr-Erf mRNA was predominantly detected in muscle, and at lower levels in ganglion, gills, gonad, hepatopancreas, and stomach by quantitative real-time PCR (QPCR) method. During embryogenesis, Hr-Erf mRNA was detected from eggs to early developmental stage embryos, whereas the transcript levels were decreased after neurula stage. Similar to the QPCR results, maternal transcripts of Hr-Erf was detected in the fertilized eggs by whole-mount in situ hybridization. Maternal mRNA of Hr-Erf was gradually lost from the neurula stage. Zygotic expression of Hr-Erf started in most blastomeres at the 8-cell stage. At gastrula stage, Hr-Erf was specifically expressed in the precursor cells of brain and mesenchyme. When MEK inhibitor was treated, embryos resulted in loss of Hr-Erf expression in mesenchyme cells, and in excess of Hr-Erf in a-line neural cells. These results suggest that zygotic Hr-Erf products are involved in specification of mesenchyme and neural cells.