TGF-beta Suppresses COX-2 Expression by Tristetraprolin-Mediated RNA Destabilization in A549 Human Lung Cancer Cells / Journal of the Korean Cancer Association, 대한암학회지

PURPOSE: Overexpression of cyclooxygenase 2 (COX-2) is thought to promote survival of transformed cells. Transforming growth factor beta (TGF-beta) exerts anti-proliferative effects on a broad range of epithelial cells. In the current study, we investigated whether TGF-beta can regulate COX-2 expression in A549 human lung adenocarcinoma cells, which are TGF-beta-responsive and overexpress COX-2. MATERIALS AND METHODS: Western blotting, Northern blotting, and mRNA stability assays were performed to demonstrate that COX-2 protein and mRNA expression were suppressed by TGF-beta. We also evaluated the effects of tristetraprolin (TTP) on COX-2 mRNA using RNA interference. RESULTS: We demonstrated that COX-2 mRNA and protein expression were both significantly suppressed by TGF-beta. An actinomycin D chase experiment demonstrated that COX-2 mRNA was more rapidly degraded in the presence of TGF-beta, suggesting that TGF-beta-induced inhibition of COX-2 expression is achieved via decreased mRNA stability. We also found that TGF-beta rapidly and transiently induced the expression of TTP, a well-known mRNA destabilizing factor, before suppression of COX-2 mRNA expression was observed. Using RNA interference, we confirmed that increased TTP levels play a pivotal role in the destabilization of COX-2 mRNA by TGF-beta. Furthermore, we showed that Smad3 is essential to TTP-dependent down-regulation of COX-2 expression in response to TGF-beta. CONCLUSION: The results of this study show that TGF-beta down-regulated COX-2 expression via mRNA destabilization mediated by Smad3/TTP in A549 cells.

Transcriptional induction of DLC-1 gene through Sp1 sites by histone deacetylase inhibitors in gastric cancer cells

We previously reported that trichostatin A (TSA), a histone deacetylase (HDAC) inhibitor, induced DLC-1 mRNA expression and accumulated acetylated histones H3 and H4 associated with the DLC-1 promoter in DLC-1 non-expressing gastric cancer cells. In this study, we demonstrated the molecular mechanisms by which TSA induced the DLC-1 gene expression. Treatment of the gastric cancer cells with TSA activates the DLC-1 promoter activity through Sp1 sites located at -219 and -174 relative to the transcription start site. Electrophoretic mobility-shift assay (EMSA) revealed that Sp1 and Sp3 specifically interact with these Sp1 sites and showed that TSA did not change their binding activities. The ectopic expression of Sp1, but not Sp3, enhances the DLC-1 promoter responsiveness by TSA. Furthermore, the TSA-induced DLC-1 promoter activity was increased by p300 expression and reduced by knockdown of p300. These results demonstrated the requirement of specific Sp1 sites and dependence of Sp1 and p300 for TSA-mediated activation of DLC-1 promoter.

The Synergism between Belotecan and Cisplatin in Gastric Cancer / Journal of the Korean Cancer Association, 대한암학회지

PURPOSE: We wanted to demonstrate the anti-cancer effect and interaction between belotecan and cisplatin on gastric cancer cell line and we evaluated the mechanisms of this synergistic effect in vitro. MATERIALS AND METHODS: The growth inhibitory effect of belotocan and cisplatin against several gastric cancer cell lines (SNU-5, SNU-16 and SNU-601) was estimated by tetrazolium dye assay. The effect of a combination treatment was evaluated by the isobologram method. The biochemical mechanisms for the interaction between the drugs were analyzed by measuring the formation of DNA interstrand cross-links (ICLs) and DNA topo-I activity. RESULTS: Belotecan showed synergism with cisplatin for growth inhibitory effect on the gastric cancer cell lines SNU-5, and SNU-16, but this was subadditive on the SNU-601 cell line. The formation of DNA ICLs in SNU-16 cells by cisplatin was increased by combination with belotecan, but this was not affected in SNU-601 cells. The topo-I inhibition by belotecan was enhanced at high concentrations of cisplatin in SNU-16, but not in SNU-601 cells. CONCLUSION: Belotecan and cisplatin show various combination effect against gastric cancer cells. The synergism between cisplatin and belotecan could be the result of one of the following mechanisms: the modulating effect of belotecan on the repair of cisplatin-induced DNA adducts and the enhancing effect of cisplatin on the belotecan-induced topo-I inhibitory effect.

An Outbreak of Vivax Malaria in Republic of Korea in 1999 / 감염

BACKGROUND: Annual occurrence of vivax malaria in Republic of Korea (ROK) has exceeded 1,000 cases since 1997. Military system is thought to be a important source of the current outbreak. We collected the information on malaria cases of ROK army, veterans and civilians which occurred in 1999, and analyzed the characteristics of the current outbreak. METHODS: Informations on malaria cases of ROK army, including name, age, sex, rank, force, day of onset, region, etc., were collected through the Office of Surgeon General at Headquarters of ROK army and then analyzed. Informations about malaria cases of veterans and civilians, including age, sex, day of onset, region, etc., were collected through the National Institute of Health and then analyzed. RESULTS:Among a total of 3,628 cases in 1999, 1,085 (29.91%) occurred in the military, 996 (27.45%) occurred in veterans, and 1,547 (42.64%) occurred in civilians. Monthly occurrence reached its peak level at July and had maintained to August. Yeoncheon, Cheolwon and Paju were the highest prevalence region. CONCLUSION: Case occurrence in ROK decreased in 1999 and it was contributed by chemoprophylaxis which has been done since 1997 in the military. It is thought that more attention must be given to protect the further spread of malaria infection.

Isolation and Identification of the Antigen Recognized by Human Cytomegalovirus Specific Monoclonal Antibody SCMVM 34

Human cytomegalovirus (HCMV)-specific monoclonal antibody, SCMVM 34, recognizes early antigen confined to the nucleus of HCMV-infected cells. This study was performed to identify the antigen reactive to SCMVM 34 with purification and amino acid sequencing. The nuclear and cytoskeletal fraction of HCMV-infected cells was subjected to 0.4 M NaCl extraction, DEAE-Sephacel ion exchange chromatography, DNA-cellulose chromatography and SDS-PAGE. The molecular weight of the reactive proteins was 52 kD, 40 kD and 34 kD. The modified or blocked amino termini of 52 kD and 40 kD showed resistance to Edman degradation. The internal peptide fragments were isolated by tryptic digeytion and reverse-phase HPLC. The internal amino acid sequence analysis of the peptides from HPLC profile revealed that the antigens recognized by SCMVM 34 was ppUIA4.