Seung-Hee Ryu

TGF-β1-induced epithelial–mesenchymal transition and acetylation of Smad2 and Smad3 are negatively regulated by EGCG in Human A549 lung cancer cells

Transforming growth factor-β1, the key ligand of Smad-dependent signaling pathway, is critical for epithelial-mesenchymal transition during embryo-morphogenesis, fibrotic diseases, and tumor metastasis. In this study, we found that activation of p300/CBP, a histone acetyltransferase, by TGF-β1 mediates Epithelial-mesenchymal transition (EMT) via acetylating Smad2 and Smad3 in TGF-β1 signaling pathway. We demonstrated that treatment with EGCG inhibited p300/CBP activity in human lung cancer cells. Also, we observed that EGCG potently inhibited TGF-β1-induced EMT and reversed the up-regulation of various genes during EMT. Our findings suggest that EGCG inhibits the induction of p300/CBP activity by TGF-β1. Therefore, EGCG inhibits TGF-β1-mediated EMT by suppressing the acetylation of Smad2 and Smad3 in human lung cancer cells.

Recombinant Human Epidermal Growth Factor Accelerates Recovery of Mouse Small Intestinal Mucosa After Radiation Damage

PURPOSE To determine whether systemically administered recombinant human epidermal growth factor (rhEGF) accelerates the recovery of mouse small intestinal mucosa after irradiation. METHODS AND MATERIALS A mouse mucosal damage model was established by administering radiation to male BALB/c mice with a single dose of 15 Gy applied to the abdomen. After irradiation, rhEGF was administered subcutaneously at various doses (0.04, 0.2, 1.0, and 5.0 mg/kg/day) eight times at 2- to 3-day intervals. The evaluation methods included histologic changes of small intestinal mucosa, change in body weight, frequency of diarrhea, and survival rate. RESULTS The recovery of small intestinal mucosa after irradiation was significantly improved in the mice treated with a high dose of rhEGF. In the mice that underwent irradiation without rhEGF treatment, intestinal mucosal ulceration, mucosal layer damage, and severe inflammation occurred. The regeneration of villi was noticeable in mice treated with more than 0.2 mg/kg rhEGF, and the villi recovered fully in mice given more than 1 mg/kg rhEGF. The frequency of diarrhea persisting for more than 3 days was significantly greater in the radiation control group than in the rhEGF-treated groups. CONCLUSIONS Systemic administration of rhEGF accelerates recovery from mucosal damage induced by irradiation. We suggest that rhEGF treatment shows promise for the reduction of small intestinal damage after irradiation.

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.

Intracytoplasmic epidermal growth factor receptor shows poor response to the cetuximab antitumor effect in irradiated non-small cell lung cancer cell lines

PURPOSE The purpose of this study was to evaluate the antitumor effect of a blocking antibody for EGFR in the cytoplasm of a lung cancer cell line. METHODS & MATERIALS The A549 and H1299 cell lines were employed to demonstrate differential responses to cetuximab in combination with radiotherapy. Localization of EGFR was detected using confocal microscopy, and radiosensitivity was measured. RESULTS Treatment with cetuximab inhibited colony formation in a dose-dependent manner in A549, but not H1299 cells. Confocal microscopy revealed EGFR localized in the cytosolic fraction, particularly around the golgi apparatus in H1299, in contrast to cell membrane localization in A549 cell line. After irradiation, nuclear EGFR was detected in the A549 cell line. However, EGFR did not translocate to the nucleus in H1299 cells. While EGFR expression was decreased in both A549 and H1299 cell lines upon treatment with a combination of cetuximab and radiation, radiosensitivity was increased solely in A549 cells. CONCLUSIONS Our findings suggest that localization of EGFR is related to the sensitivity/resistance of cells to a combination of cetuximab and radiotherapy.

Paradoxical induction of growth arrest and apoptosis by EGF via the up-regulation of PTEN by activating Redox factor-1/Egr-1 in human lung cancer cells

Epidermal growth factor (EGF) signaling promotes cell proliferation and survival in several types of cancer. Here, however, we showed that EGF inhibits proliferation and promotes programmed cell death in non-small cell lung cancer (NSCLC) cells. In A549 cells, EGF increased redox factor-1 (Ref-1) expression and the association of Ref-1 with zinc finger-containing transcriptional regulator (EGR1) via activation of p22phox, RAC1, and an NADPH oxidase subunit. EGF increased p22phox and RAC1 expression through activation of purinergic receptors (P2Y). Elevated Ref-1/EGR1 levels increased phosphatase and tensin homolog (PTEN) levels, leading to inhibition of the Akt pathway. EGF-induced PTEN upregulation increased apoptosis and autophagy-induced damage in A549 cells, whereas Ref-1 knockdown blocked EGF-induced PTEN upregulation in an NADPH oxidase p22phox subunit-independent manner. In addition, p22phox knockdown restored EGF-induced effects, implying that changes in P2Y activity caused by EGF, which activates NADPH oxidase via RAC1, influenced Ref-1-mediated redox regulation. Finally, EGF similarly attenuated cell proliferation and promoted autophagy and apoptosis in vivo in a xenograft model using A549 cells. These findings reveal that EGF-induced redox signaling is linked to Ref-1-induced death in NSCLC cells.

Protective effect of α-lipoic acid against radiation-induced fibrosis in mice

Radiation-induced fibrosis (RIF) is one of the most common late complications of radiation therapy. We found that α-lipoic acid (α-LA) effectively prevents RIF. In RIF a mouse model, leg contracture assay was used to test the in vivo efficacy of α-LA. α-LA suppressed the expression of pro-fibrotic genes after irradiation, both in vivo and in vitro, and inhibited the up-regulation of TGF-β1-mediated p300/CBP activity. Thus, α-LA prevents radiation-induced fibrosis (RIF) by inhibiting the transcriptional activity of NF-κB through inhibition of histone acetyltransferase activity. α-LA is a new therapeutic methods that can be used in the prevention-treatment of RIF.

Pinexol inhibits in vitro inflammatory biomarkers by blocking NF-κB signaling pathway and protects mice from lethal endotoxemia

Korean red pine (Pinus densiflora) bark extract is used for the treatment of chronic inflammatory-related ailments through as yet undefined mechanisms. The present study was conducted to explore the anti-inflammatory activities of Korean red pine bark extract (commercially called Pinexol in Korea) in murine RAW 264.7 macrophages and LPS-induced shock in mice. Here, we set out to determine whether the anti-inflammatory effects of Pinexol are mediated to suppress nuclear factor-κB (NF-κB) activation in lipopolysaccharide (LPS)-stimulated RAW 264.7 cells. We found that Pinexol significantly suppressed LPS-stimulated nitric oxide (NO) and IL-6 production without affecting cell viability. Pinexol inhibited the expression of LPS-induced inducible nitric oxide synthase (iNOS) and cyclooxygenase-2 (COX-2) protein and their mRNA expression. As a result, Pinexol inhibited pro-inflammatory cytokines such as IL-6, which is hypothesized as being due to the suppression of LPS-induced NF-κB activation. Moreover, Pinexol improved the survival rate during lethal endotoxemia by inhibiting the production of TNF-α and IL-6 in an animal model and our GC-MS analysis using derivertization showed that four major components of Pinexol were cathechin, epi-catechin, and methylated catechins. Therefore, we demonstrate here the evidence that Korean red pine bark extract potentially inhibits the biomarkers related to inflammation in vitro and in vivo, and might be provided as a potential candidate for treatment of inflammatory diseases.