Biomedical subjects

Hansoo Lee

Publications and source records attributed to Hansoo Lee.

15 recordsLinked to original sources

PubMed2006

Temporal cDNA microarray analysis of gene expression in human hepatocellular carcinoma upon radiation exposure.

Radiotherapy is not commonly used for the treatment of human hepatocellular carcinoma, due to its poor response rate and poor tolerance of normal liver to ionizing radiation. Recently developed microarray technology makes it possible to verify genes responsive to anticancer therapy of human cancers by simultaneous analysis of gene expression profiles. In the present study, the expression profile of radiation-responsive genes in human hepatocellular carcinoma was evaluated through time-dependent cDNA microarray analysis of expressional variation, following exposure to ionizing radiation. Upon exposure to radiation, more than 13% of genes in both radiation-resistant and -sensitive cells responded to radiation. Time-dependent analysis of radiation-responsive genes revealed that, irrespective of radiation sensitivity, greatly different subsets of genes sequentially participated in cellular response to radiation at their specific activation or deactivation time points. The majority of radiation-responsive genes were differentially but not commonly expressed between radiation-resistant and -sensitive cells. When these differentially regulated genes were classified according to their physiological and functional characteristics and radiation sensitivity, it was prominently obvious that DNA repair-promoting genes were up-regulated in radio-resistant cells and down-regulated or unchanged in radiation-sensitive cells. The present findings indicate that different subsets of genes are sequentially working and DNA repair capacity may control the radiation sensitivity of human hepatocellular carcinoma cells more than any other physiological factor.

Carcinoma, Hepatocellular↗

PubMed2005

Prostaglandin E2 stimulates angiogenesis by activating the nitric oxide/cGMP pathway in human umbilical vein endothelial cells.

Prostaglandin E2 (PGE2), a major product of cyclooxygenase, has been implicated in modulating angiogenesis, vascular function, and inflammatory processes, but the underlying mechanism is not clearly elucidated. We here investigated the molecular mechanism by which PGE2 regulates angiogenesis. Treatment of human umbilical vein endothelial cells (HUVEC) with PGE2 increased angiogenesis. PGE2 increased phosphorylation of Akt and endothelial nitric oxide synthase (eNOS), eNOS activity, and nitric oxide (NO) production by the activation of cAMP-dependent protein kinase (PKA) and phosphatidylinositol 3-kinase (PI3K). Dibutyryl cAMP (DB-cAMP) mimicked the role of PGE2 in angiogenesis and the signaling pathway, suggesting that cAMP is a down-stream mediator of PGE2. Furthermore, PGE2 increased endothelial cell sprouting from normal murine aortic segments, but not from eNOS-deficient ones, on Matrigel. The angiogenic effects of PGE2 were inhibited by the inhibitors of PKA, PI3K, eNOS, and soluble guanylate cyclase, but not by phospholipase C inhibitor. These results clearly show that PGE2 increased angiogenesis by activating the NO/cGMP signaling pathway through PKA/PI3K/Akt-dependent increase in eNOS activity.

Animals↗

PubMed2005

beta-Carotene inhibits inflammatory gene expression in lipopolysaccharide-stimulated macrophages by suppressing redox-based NF-kappaB activation.

beta-Carotene has shown antioxidant and anti-inflammatory activities; however, its molecular mechanism has not been clearly defined. We examined in vitro and in vivo regulatory function of beta-carotene on the production of nitric oxide (NO) and PGE(2) as well as expression of inducible NO synthase (iNOS), cyclooxygenase-2, TNF-alpha, and IL-1beta. beta-Carotene inhibited the expression and production of these inflammatory mediators in both LPS-stimulated RAW264.7 cells and primary macrophages in a dose-dependent fashion as well as in LPS-administrated mice. Furthermore, this compound suppressed NF-kappaB activation and iNOS promoter activity in RAW264.7 cells stimulated with LPS. beta-Carotene blocked nuclear translocation of NF-kappaB p65 subunit, which correlated with its inhibitory effect on IkappaBalpha phosphorylation and degradation. This compound directly blocked the intracellular accumulation of reactive oxygen species in RAW264.7 cells stimulated with LPS as both the NADPH oxidase inhibitor diphenylene iodonium and antioxidant pyrrolidine dithiocarbamate did. The inhibition of NADPH oxidase also inhibited NO production, iNOS expression, and iNOS promoter activity. These results suggest that beta-carotene possesses anti-inflammatory activity by functioning as a potential inhibitor for redox-based NF-kappaB activation, probably due to its antioxidant activity.

Animals↗

PubMed2005

Tetraspanin CD9 induces MMP-2 expression by activating p38 MAPK, JNK and c-Jun pathways in human melanoma cells.

Expression of matrix metalloproteinase-2 and -9 (MMP-2 and MMP-9), which correlates with tumor invasion and metastasis, has been known to be regulated by several intracellular signaling pathways. Since the CD9 membrane protein has been implicated in signal transduction and malignant progression of cancer cells, we examined the functional involvement of CD9 in the regulation of MMP-2 and MMP-9 expression by using stable CD9 transfectant clones of MelJuso human melanoma cells. The CD9 cDNA-transfected cells with elevated CD9 expression displayed increased MMP-2 and decreased MMP-9 expression when compared with the mock transfectant cells. Among several signal pathway inhibitors tested, SB203580 and SP600125, which inhibit p38 MAPK and JNK respectively, completely blocked the CD9-stimulated MMP-2 expression. Phosphorylation levels of p38 MAPK and c-Jun in MelJuso cells were also significantly increased by CD9 transfection. In addition, the down-regulation of p38 MAPK and JNK by siRNA transfection resulted in a decrease in MMP-2 expression by MelJuso cells. Promoter analysis and gel shift assay showed that the CD9-induced MMP-2 expression is mediated by a functional AP-1 site through interactions with AP-1 transcription factors including c-Jun. These results suggest that CD9 induces MMP-2 expression by activating c- Jun through p38 MAPK and JNK signaling pathways in human melanoma cells.

Antigens, CD↗

PubMed2005

Amiloride potentiates TRAIL-induced tumor cell apoptosis by intracellular acidification-dependent Akt inactivation.

Tumor necrosis factor-related apoptosis-inducing ligand (TRAIL), a member of the tumor necrosis factor gene family, is considered as one of the most promising cancer therapeutic agents due to its ability to selectively induce tumor cell apoptosis. In this study, we investigated whether the Na(+)/H(+) exchanger inhibitor, amiloride, promotes TRAIL-induced apoptotic death both in sensitive and resistant tumor cells, HeLa and LNCaP cells, respectively, and its underlying molecular mechanism. Amiloride enhanced TRAIL-induced apoptosis and activation of caspase-3 and -8 in both cells. This compound increased TRAIL-induced mitochondrial cytochrome c release and poly(ADP-ribose) polymerase cleavage. Moreover, amiloride-induced intracellular acidification, and inhibited the phosphorylated activation of the serine/threonine kinase Akt, which is known to promote cell survival, in both tumor cells. These data suggest that amiloride sensitizes both tumor cells to TRAIL-induced apoptosis by promoting Akt dephosphorylation and caspase-8 activation via the intracellular acidification and that Na(+)/H(+) exchanger inhibitors may play an important role in the anti-cancer activity of TRAIL, especially, in TRAIL-resistant tumors with highly active and expressed Akt.

Amiloride↗

PubMed2005

Tritium levels in Chinese cabbage and radish plants acutely exposed to HTO vapor at different growth stages.

To simulate an acute exposure of Chinese cabbage and radish plants to airborne HTO, the potted plants were exposed to HTO vapor under semi-outdoor conditions for 1h at different times from the early to late growth stages. The plants were grown outdoors and the plant tritium was measured at the end of an exposure (h(0)) and at harvest. The leaf tissue free water tritium (TFWT) concentrations at h(0) were considerably lower than estimated equilibrium concentrations. In the leaves of Chinese cabbage, the exposure at the earlier growth stage generally ended with a higher TFWT concentration. Such a tendency was not apparent either in the leaves or roots of radish. On the other hand, the earlier stage exposure gave rise to lower TFWT concentrations at the harvest of both crops. For the OBT (organically bound tritium), however, the same occurred only in the Chinese cabbage leaves. During the period between the exposure and harvest, the TFWT concentrations reduced by factors of up to 1.1 x 10(6) for the Chinese cabbage leaves and 1.3 x 10(4) for the radish roots. Based on the activity ratios of OBT to TFWT at harvest, it is estimated that OBT mostly contributes much more to the ingestion dose than TFWT does.

Air Pollutants↗

PubMed2004

Nitric oxide inhibition of homocysteine-induced human endothelial cell apoptosis by down-regulation of p53-dependent Noxa expression through the formation of S-nitrosohomocysteine.

Hyperhomocysteinemia is believed to induce endothelial dysfunction and promote atherosclerosis; however, the pathogenic mechanism has not been clearly elucidated. In this study, we examined the molecular mechanism by which homocysteine (HCy) causes endothelial cell apoptosis and by which nitric oxide (NO) affects HCy-induced apoptosis. Our data demonstrated that HCy caused caspase-dependent apoptosis in cultured human umbilical vein endothelial cells, as determined by cell viability, nuclear condensation, and caspase-3 activation and activity. These apoptotic characteristics were correlated with reactive oxygen species (ROS) production, lipid peroxidation, p53 and Noxa expression, and mitochondrial cytochrome c release following HCy treatment. HCy also induced p53 and Noxa expression and apoptosis in endothelial cells from wild type mice but not in the p53-deficient cells. The NO donor S-nitroso-N-acetylpenicillamine, adenoviral transfer of inducible NO synthase gene, and antioxidants (alpha-tocopherol and superoxide dismutase plus catalase) but not oxidized SNAP, 8-Br-cGMP, nitrite, and nitrate, suppressed ROS production, p53-dependent Noxa expression, and apoptosis induced by HCy. The cytotoxic effect of HCy was decreased by small interfering RNA-mediated suppression of Noxa expression, indicating that Noxa up-regulation plays an important role in HCy-induced endothelial cell apoptosis. Overexpression of inducible NO synthase increased the formation of S-nitroso-HCy, which was inhibited by the NO synthase inhibitor N-monomethyl-l-arginine. Moreover, S-nitroso-HCy did not increase ROS generation, p53-dependent Noxa expression, and apoptosis. These results suggest that up-regulation of p53-dependent Noxa expression may play an important role in the pathogenesis of atherosclerosis induced by HCy and that an increase in vascular NO production may prevent HCy-induced endothelial dysfunction by S-nitrosylation.

Antioxidants↗

PubMed2004

Inhibition of farnesyltransferase prevents collagen-induced arthritis by down-regulation of inflammatory gene expression through suppression of p21(ras)-dependent NF-kappaB activation.

Farnesylation of p21(ras) is an important step in the intracellular signaling pathway of growth factors, hormones, and immune stimulants. We synthesized a potent and selective farnesyltransferase inhibitor (LB42708) with IC(50) values of 0.8 nM in vitro and 8 nM in cultured cells against p21(ras) farnesylation and examined the effects of this inhibitor in the settings of inflammation and arthritis. LB42708 suppressed NF-kappaB activation and iNOS promoter activity by suppressing the I-kappaB kinase activity and I-kappaBalpha degradation. The inhibitor suppressed the expression of inducible NO synthase, cyclooxygenase-2, TNF-alpha, and IL-1beta and the production of NO and PGE(2) in immune-activated macrophages and osteoblasts as well as LPS-administrated mice. Furthermore, in vivo administration of LB42708 significantly decreased the incidence and severity of arthritis as well as mRNA expression of inducible NO synthase, cyclooxygenase-2, TNF-alpha, and IL-1beta in the paws of collagen-induced arthritic mice compared with controls. These observations indicate that the anti-inflammatory and antiarthritic effects of the farnesyltransferase inhibitor may be ascribed to the inhibition of I-kappaB kinase activity and subsequent suppression of NF-kappaB-dependent inflammatory gene expression through the suppression of p21(ras) farnesylation. Together, these findings reveal that the inhibitory effect of LB42708 on p21(ras)-dependent NF-kappaB activation may have potential therapeutic value for arthritis and other inflammatory diseases.

Alkyl and Aryl Transferases↗

PubMed2004

Identification of autoantibody against poly (ADP-ribose) polymerase (PARP) fragment as a serological marker in systemic lupus erythematosus.

OBJECTIVES: By utilizing serological analysis of a recombinant cDNA expression library (SEREX), we previously found that autoantibodies to poly (ADP-ribose) polymerase (PARP) are specifically present in the sera of patients with SLE. In this study, recombinant proteins of various domains of PARP were used to determine the PARP domain that is associated with SLE. METHODS: We produced four recombinant PARP proteins, which contained various PARP domains, and then carried out enzyme linked immunosorbent assay (ELISA) using these recombinant proteins to identify domains useful for SLE diagnosis. The recombinant proteins used in this analysis were; ADPNF (amino acids 1-234), ET-L2 (amino acids 339-680), ET-L3 (amino acids 681-1014), and ADPCF (amino acids 300-1014). RESULT: ELISA with ADPNF or ET-L2 showed low sensitivity in the sera of patients with SLE (14.3% and 17.0% respectively), whereas ELISA with ET-L3 or ADPCF showed high sensitivity in the sera of patients with SLE (34.0% and 49.1%, respectively). Autoantibodies to ADPCF were not found in the sera of patients with rheumatoid arthritis (0/30), systemic sclerosis (0/30) or healthy donors (0/54) and were rarely found in polymyositis/dermatomyositis (1/30) and Sjogren syndrome (1/14). Autoantibodies to ADPCF were closely associated with the presence of an oral ulcer in SLE (P=0.03, by the chi-square test). CONCLUSION: The high sensitivity and specificity shown by autoantibodies to ADPCF protein could be used as a valuable serologic maker for the diagnosis of SLE.

Adult↗

PubMed2003

A decrease in the expression of CD63 tetraspanin protein elevates invasive potential of human melanoma cells.

CD63, which belongs to the tetraspanin membrane proteins, has been proposed to play an important role in inhibiting melanoma metastasis. To determine whether reduction of CD63 expression, which frequently occurs in the malignant progression of human melanoma, is responsible for metastasis promotion, we transfected the antisense CD63 cDNA into MelJuso melanoma cells having endogenous CD63 expression. The antisense CD63 transfectant clones showing decreased CD63 expression displayed increased cell motility, matrix- degrading activity, and invasiveness in vitro when compared with the control transfectant cells. The antisense CD63 cDNA-transfected cells also exhibited altered adhesiveness to extracellular matrix. The results suggest that reduced CD63 expression contributes to the invasive and metastatic ability of human melanoma cells.

Antigens, CD↗

PubMed2003

Point mutations affecting the oligomeric structure of Nm23-H1 abrogates its inhibitory activity on colonization and invasion of prostate cancer cells.

In order to identify Nm23-H1's structural motifs influencing its metastasis-inhibitory activity, we transfected DU 145 human prostate carcinoma cells with the expression vector encoding the Nm23-H1 protein with mutations at the following amino acids: serine-44, a phosphorylation site; proline-96, a site corresponding to the k-pn mutation that causes developmental defects in Drosophila; and serine-120, a site of mutation in human neuroblastoma and phosphorylation. Significant decrease in colonization in soft agar and invasiveness of DU 145 cells was observed in the wild type nm23-H1 transfectants, and also in the serine-44 and serine-120 to alanine mutant nm23-H1-transfected cell lines. However, the k-pn type proline-96 to serine (P96S) and neuroblastoma type serine-120 to glycine (S120G) mutations of Nm23-H1 abrogated its inhibitory activity on colonization and invasion. Meanwhile, all of the recombinant mutant Nm23-H1 proteins produced in Escherichia coli exhibited NDP kinase activity levels at the wild type protein, although the P96S and S120G mutant proteins exhibited decreased histidine protein kinase activity and autophosphorylation level, respectively. Interestingly, only two of the mutant recombinant Nm23-H1 proteins examined, P96S and S120G, exhibited reduced hexameric and increased dimeric oligomerization relative to the wild type. These correlative data suggest that the metastasis-suppressing activity of Nm23-H1 may depend on its oligomeric structure, but not on its NDP kinase activity.

Animals↗

PubMed2003

Promoter hypomethylation of a novel cancer/testis antigen gene CAGE is correlated with its aberrant expression and is seen in premalignant stage of gastric carcinoma.

Previously, we reported the identification and characterization of a novel cancer/testis antigen gene, CAGE(4), that was expressed in various histological types of tumors, but not in normal tissues, with the exception of the testis. To date, molecular mechanisms for the expression of CAGE have never been studied. In our expression analysis, we found that some cancer cell lines did not express CAGE. The expression of CAGE could be restored in these cell lines by treatment with 5(')-aza-2(')-deoxycytidine, suggesting that the expression of CAGE is mainly suppressed by hypermethylation. Bisulfite sequencing analysis of the 16 CpG sites of the CAGE promoter in various cancer cell lines and tissues revealed a close relationship between the methylation status of the CAGE promoter and the expression of CAGE. The transient transfection experiments displayed that the methylation of CpG sites inhibited the CAGE promoter activity in luciferase reporter assays. The methylation of the CpG sites inhibited the binding of transcription factors, shown by a mobility shift assay. A methylation-specific PCR analysis revealed that hypomethylation of the CAGE promoter was present at frequencies of more than 60% in breast, gastric, and lung cancers, and hepatocellular carcinomas, and at frequencies of less than 40% in prostate, uterine cervical, and laryngeal cancers. Promoter hypomethylation was found in chronic gastritis (19/55, 34.5%) and liver cirrhosis (13/22, 59%), but not in normal prostate, normal colon, or chronic hepatitis. These results suggest that the methylation status of the CpG sites of CAGE determines its expression, that the hypomethylation of CAGE precedes the development of gastric cancer and hepatocellular carcinoma, and that the high frequencies of hypomethylation of CAGE, in various cancers would be valuable as a cancer diagnostic marker.

Antigens, Nuclear↗

PubMed2003

Metastasis-suppressor KAI1/CD82 induces homotypic aggregation of human prostate cancer cells through Src-dependent pathway.

To investigate the functional role of KAI1/CD82, a metastasis suppressor for human prostate cancer, in the regulation of homotypic cell adhesion, we transfected KAI1 cDNA into DU 145 human prostate cancer cells and established stable transfectant clones with high KAI1/CD82 expression. The KAI1 transfectant cells exhibited significantly increased homotypic cell aggregation in comparison with the control transfectant cells. This aggregation of the KAI1 transfectants was further enhanced upon exposure to anti-CD82 antibody, suggesting that KAI1/CD82 may be involved in the intracellular signaling for the cell adhesion. Among several signal pathway inhibitors tested, PP1, an inhibitor of Src family kinases, significantly suppressed homotypic aggregation of the KAI1 transfectant cells. Ligation of KAI1/CD82 with anti-CD82 antibody increased endogenous Src kinase activity of the KAI1 transfectant cells. When different types of src expression constructs were retransfected into the KAI1-transfected DU 145 cells, kinase-negative mutant src transfectant cells exhibited much lower homotypic aggregation than the mock cells transfected with an empty vector. Moreover, homotypic aggregation of the mutant src transfectant cells was not enhanced by KAI1/CD82 ligation with anti- CD82 antibody. These results suggest that Src mediates the intracellular signaling pathway of KAI1/CD82 for the induction of homotypic adhesion of human prostate cancer cells.

Adenocarcinoma↗

PubMed2002

Functional involvement of src and focal adhesion kinase in a CD99 splice variant-induced motility of human breast cancer cells.

Earlier report showed that expression of a splice variant of CD99 transmembrane protein increases invasive ability of human breast cancer cells. Cell motility was also significantly enhanced by the CD99 splice variant expression. In an effort to identify the cellular components that mediate a signal transduction pathway triggered by the CD99 splice variant, known signal path inhibitors were examined for their effects on the motility of the CD99 splice variant-transfected MDA-MB-231 breast cancer cells. Phenylarsine oxide, an inhibitor of phosphatase specific for focal adhesion kinase, and PP1, an inhibitor of src kinase family, significantly suppressed motility of the cells. Among different types of src transfectant clones generated, kinase-negative mutant src transfectant cells were 80% less motile than the mock cells transfected with an empty-vector, while v-src and c-src transfectants exhibited cell motility levels at or slightly above the mock transfectant. These results suggest that src and focal adhesion kinase mediate the intracellular signaling pathway of a CD99 splice variant for the induction of motility of human breast cancer cells.

12E7 Antigen↗

PubMed2002

Immunoreactivity of CD99 in stomach cancer.

CD99 is characteristically expressed in Ewing's sarcoma/primitive neuroectodermal tumor. Recently its immunoreactivity has also been reported in other tumors. However, the significance of CD99 isoforms expressed in these tumors has not been elucidated. In this study, we evaluated the expression of CD99 isoforms and its relationship with histopathologic parameters in gastric adenocarcinomas. Paraffin sections of 46 gastric adenocarcinomas were stained with an anti-CD99 monoclonal antibody, YG32. Twelve (26.1%) cases of 46 gastric adenocarcinomas showed immunoreactivity to YG32. The CD99 expression was also seen both in non-neoplastic foveolar epithelial cells and infiltrating lymphocytes. In addition, Western blot and RT-PCR analyses revealed that the type I is the predominant isoform of CD99 in non-neoplastic and neoplastic gastric tissues. The CD99 expression was usually seen in the intestinal type adenocarcinoma, while rarely in the diffuse type. The CD99 immunoreactivity decreased in MMP-2-overexpressing adenocarcinomas (p=0.028). Our results suggest that the type I is the major isoform of CD99 expressed in non-neoplastic gastric mucosa and gastric adenocarcinomas and its downregulation in gastric adenocarcinoma may be associated with cellular dedifferentiation and/or MMP-2 overexpression.

12E7 Antigen↗