Kwang Dong Kim

6-Acetonyl-5,6-dihydrosanguinarine (ADS) from Chelidonium majus L. triggers proinflammatory cytokine production via ROS-JNK/ERK-NFκB signaling pathway.

Chelidonium majus L. is an herbal plant that is commonly used in Western phytotherapy and traditional Chinese medicine for diuretic, antitussive, eye-regenerative, anti-osteoporotic, and radioprotective purposes. In this study, we purified 6-acetonyl-5,6-dihydrosanguinarine (ADS) from C. majus and investigated its immune-stimulatory effect. We found that ADS has the potential to induce the inflammatory cytokines TNF-α, IL-6, and IL-8 in macrophages and dendritic cells (DCs), that NFκB activation is a critical mediator of ADS-induced cytokine production, and that the activation of NFκB was dependent on reactive oxygen species (ROS). ADS induced phosphorylation of ERK and JNK, which was also associated with NFκB activation; phosphorylarion and cytokine production were inhibited by ROS scavenger and by specific MAPK inhibitors. Taken together, the results suggest that ADS from C. majus, as a positive immune modulator, induces inflammatory cytokines that might improve immunity, via the ROS-ERK/JNK-NFκB pathway.

Human telomerase reverse transcriptase (hTERT): a target molecule for the treatment of cisplatin-resistant tumors.

BACKGROUND Human telomerase reverse transcriptase (hTERT) is a catalytic enzyme that is required for telomerase activity (TA) and cancer progression. Telomerase inhibition or inactivation increases cellular sensitivity to UV irradiation, DNA-damaging agents, the tyrosine kinase inhibitor, imatinib, and pharmacological inhibitors, such as BIBR1532. hTERT is associated with apoptosis. Some patients show drug-resistance during anti-cancer drug treatment and the cancer cell acquire anti-apoptotic mechanism. Therefore, we attempted to study correlation between hTERT and drug-resistance. METHODS To study the correlation between protein level and activity of hTERT and drug-resistance, Western blotting and telomerase repeat amplification protocol (TRAP) assays were performed. To investigate whether hTERT contributes to drug resistance in tumor cells, we transiently decreased hTERT levels using small interfering RNA (siRNA) in T24/R2 cells. RESULTS hTERT knockdown increased Bax translocation into the mitochondria and cytochrome C release into the cytosol. Caspase inhibitors, especially Z-VAD-FMK, rescued this phenomenon, suggesting that the stability or expression of hTERT might be regulated by caspase activity. CONCLUSIONS These data suggest that hTERT might be a target molecule for drug-resistant tumor therapy.

NDRG2 and PRA1 interact and synergistically inhibit T-cell factor/β-catenin signaling

NDRG2a and PRA1 colocalize by fluorescence microscopy (View Interaction: 1, 2, 3)

NDRG2 correlated with favorable recurrence-free survival inhibits metastasis of mouse breast cancer cells via attenuation of active TGF-β production

N-myc downstream-regulated gene 2 (NDRG2) has been studied for its inhibitory effects against growth and metastasis of many tumor cell types. In this study, we showed NDRG2 expression was correlated with favorable recurrence-free survival of patients with breast cancer and inhibited metastasis of breast cancer cells (4T1). NDRG2 expression was examined in 189 breast carcinoma tissues and paired normal breast tissues using immunohistochemistry. Histological and clinicopathological data were correlated using Pearsons chi-square test of independence. NDRG2 expression in human breast cancer tissues was inversely associated with lymph node metastasis and pTNM stage. Furthermore, patients with breast cancer with a high level of NDRG2 expression showed favorable recurrence-free survival (P = 0.038). To study the effect of NDRG2 on metastasis in vivo, we established an NDRG2-overexpressing mouse breast cancer cell line (4T1-NDRG2) and measured the metastasis and survival of 4T1-NDRG2 tumor-bearing mice. To test whether transforming growth factor β (TGF-β)- mediated metastasis of 4T1 was inhibited by NDRG2 expression, TGF-Smad-binding element (SBE)-luciferase activity and/or measurement of active TGF-β were performed in cell or tumor tissue level. 4T1-NDRG2 cells grew gradually and showed less metastatic activity in vivo and low invasiveness in vitro. 4T1-NDRG2 cells showed lower SBE-luciferase activity and lower level of active autocrine TGF-β than 4T1-Mock did. Correctly, our data show that NDRG2 significantly suppress tumor metastasis by attenuating active autocrine TGF-β production, and the attenuation might be typically associated with the favorable recurrence-free survival of patients clinically.

Human papillomavirus 16E6 suppresses major histocompatibility complex class I by upregulating lymphotoxin expression in human cervical cancer cells.

Major histocompatibility complex (MHC) class I is a major host defense mechanism against viral infections such as type 16 and type 18 of the human papillomavirus (HPV). Here, we found that the E6 oncogene from HPV16, but not HPV18, suppressed MHC I expression. Ectopic expression of HPV16E6 in HeLa cells, which are infected with HPV18, suppressed MHC I expression, and that knockdown by antisense or siRNA of the HPV16E6 strongly enhanced MHC I expression in Caski cells, which are infected with HPV18, but not HPV16. The expression of HPV16E6 strongly enhanced cellular resistance to cytotoxic T lymphocytes (CTLs)-mediated lytic activity, and knockdown of HPV16E6 by antisense had the opposite effect. The regulation of HPV16E6-mediated MHC I suppression might be through the regulation of lymphotoxin (LT) and its receptor, LTβR. In addition, cells from the spleen and liver of LTα- or LTβR-deficient mice showed increased MHC I expression. Overall, these results demonstrated that the E6 oncogene of HPV16 might play an important role in cell transformation and cancer development through LT-mediated MHC I downregulation in humans.

NDRG2 is one of novel intrinsic factors for regulation of IL-10 production in human myeloid cell

N-myc downstream-regulated gene 2 (NDRG2) implicated in cellular growth and differentiation was previously reported as it is specifically expressed in primary and in vitro-differentiated dendritic cells (DCs) from monocytes and CD34(+) progenitor cells. However, its function has yet to be investigated in DCs. Here, the novel NDRG2 function about modulation of cytokines in DC was observed in this study. The secretion of IL-10 was not found in the monocyte-derived DC cells with high level of NDRG2 expression, but IL-10 was abundantly secreted up to 1ng/ml in the monocyte-derived macrophages with low level of NDRG2 expression, and further confirmed that the expression of IL-10 was dramatically increased in NDRG2-silenced DCs under presence of LPS, and significantly reduced in the NDRG2-overexpressed U937 cells under stimulation of PMA. The secretion of IL-12p70 was significantly reduced in the siNDRG2 introduced DC cells. The intracellular signaling of IL-10 secretion was markedly inhibited by SB203580, inhibitor of p38 MAPK, in the LPS-activated DCs and phosphorylation of p38 MAPK was decreased in the NDRG2 introduced U937 cells under PMA-stimulation. Taken together, NDRG2 might have a pivotal role as one of intrinsic factors for the modulation of p38 MAPK phosphorylation, and subsequently involve in controlling of IL-10 production.

Highly potent tyrosinase inhibitor, neorauflavane from Campylotropis hirtella and inhibitory mechanism with molecular docking.

Tyrosinase inhibition may be a means to alleviate not only skin hyperpigmentation but also neurodegeneration associated with Parkinsons disease. In the course of metabolite analysis from tyrosinase inhibitory methanol extract (80% inhibition at 20 μg/ml) of Campylotropis hirtella, we isolated fourteen phenolic compounds, among which neorauflavane 3 emerged as a lead structure for tyrosinase inhibition. Neorauflavane 3 inhibited tyrosinase monophenolase activity with an IC50 of 30 nM. Thus this compound is 400-fold more active than kojic acid. It also inhibited diphenolase (IC50=500 nM), significantly. Another potent inhibitor 1 (IC50=2.9 μM) was found to be the most abundant metabolite in C. hirtella. In kinetic studies, compounds 3 showed competitive inhibitory behavior against both monophenolase and diphenolase. It manifested simple reversible slow-binding inhibition against monophenolase with the following kinetic parameters: Ki(app)=1.48 nM, k3=0.0033 nM(-1) min(-1) and k4=0.0049 min(-1). Neorauflavane 3 efficiently reduced melanin content in B16 melanoma cells with 12.95 μM of IC50. To develop a pharmacophore model, we explored the binding mode of neuroflavane 3 in the active site of tyrosinase. Docking results show that resorcinol motif of B-ring and methoxy group in A-ring play crucial roles in the binding the enzyme.

Formaldehyde exposure impairs the function and differentiation of NK cells.

We investigated the cytotoxic effects of formaldehyde (FA) on lymphocytes. FA-exposed mice showed a profound reduction not only in the number of natural killer (NK) cells but also in the expression of NK cell-specific receptors, but these mice did not exhibit decreases in the numbers of T or B lymphocytes. FA exposure also induced decreases in NK cytolytic activity and in the expression of NK cell-associated genes, such as IFN-γ, perforin and CD122. To determine the effect of FA on tumorigenicity, C57BL/6 mice were subcutaneously injected with B16F10 melanoma cells after FA exposure. The mass of the B16F10 tumor and the concentration of extravascular polymorphonuclear leukocytes were greater than those in unexposed tumor-bearing control mice. The number and cytolytic activity of NK cells were also reduced in B16F10 tumor-bearing mice exposed to FA. To determine how FA reduces the NK cell number, NK precursor (pNK) cells were treated with FA, and the differentiation status of the NK cells was analyzed. NK cell differentiation was impaired by FA treatment in a concentration-dependent manner. These findings indicate that FA exposure may promote tumor progression by impairing NK cell function and differentiation.

Adenovirally delivered IFN-β exerts antitumor effects through transient T-lymphocyte depletion and Ag-specific T-cell proliferation

Type I interferons (IFNs), including IFN-β, are known to enhance antigen (Ag) presentation and to promote the expansion, survival and effector function of CD8+ cytotoxic lymphocytes (CTL) during viral infections. Furthermore, IFN-β is a potent candidate for antitumor drugs; however, recombinant IFN-β is too unstable for use in tumor therapy in vivo. In this study, we therefore examined the efficacy and mechanism of exogenous IFN-β as a biomolecule for tumor therapy, using adenovirus encoding IFN-β (Ad-IFNβ) as a therapeutic agent in a mouse model. Ag104Ld and 4T1 tumor cells exposed to Ad-IFNβ showed growth retardation and cell death in vitro, and tumor growth as well as tumor metastasis was inhibited in vivo. The Ad-IFNβ-mediated antitumor effect was dependent on CD8+ T cells in vivo, rather than on a direct cytotoxic effect of Ad-IFNβ. Transient T lymphocyte depletion was observed in tumor tissue after intratumoral injection with Ad-IFNβ. Despite the T lymphocyte depletion, the proliferation of Ag-specific CD8+ T cells was increased in Ad-IFNβ-treated mice compared to control virus-treated mice. These results suggest that IFN-β might contribute to the inhibition of tumor growth by depleting Ag-nonspecific T lymphocytes and enhancing proliferation of Ag-specific CD8+ T cells.

Inhibition of protein tyrosine phosphatase (PTP1B) and α-glucosidase by geranylated flavonoids from Paulownia tomentosa

Abstract Protein tyrosine phosphatase 1B (PTP1B) and α-glucosidase are important targets to treat obesity and diabetes, due to their deep correlation with insulin and leptin signalling, and glucose regulation. The methanol extract of Paulownia tomentosa fruits showed potent inhibition against both enzymes. Purification of this extract led to eight geranylated flavonoids (1–8) displaying dual inhibition of PTP1B and α-glucosidase. The isolated compounds were identified as flavanones (1–5) and dihydroflavonols (6–8). Inhibitory potencies of these compounds varied accordingly, but most of the compounds were highly effective against PTP1B (IC50 = 1.9–8.2 μM) than α-glucosidase (IC50 = 2.2–78.9 μM). Mimulone (1) was the most effective against PTP1B with IC50 = 1.9 μM, whereas 6-geranyl-3,3′,5,5′,7-pentahydroxy-4′-methoxyflavane (8) displayed potent inhibition against α-glucosidase (IC50 = 2.2 μM). All inhibitors showed mixed type Ι inhibition toward PTP1B, and were noncompetitive inhibitors of α-glucosidase. This mixed type behavior against PTP1B was fully demonstrated by showing a decrease in Vmax, an increase of Km, and Kik/Kiv ratio ranging between 2.66 and 3.69.