| TOPO II is ubiquitous nuckear enzymes that govern the topological interconversions of DNA. TOPO II is vital for various nuclear processes, including DNA replication, chromosome segregation, and maintenance of chromosome structure. TOPO II expression is regulated at multiple stages, including transcriptional, phosttranscriptional, and posttranslational levels, by a multitude of signaling factors.The expression of TOPO II in tumor cells is higher than its in normal cells, so TOPO II had been the cellular target for a variety of clinically relevant anti-tumor drugs.XK469 is a synthetic quinoxaline phenoxypropionic acid derivative, recent studies suggested that XK469 is a selective topoisomerase Ilbeta inhibitor. It and his analogue have been found to have selective activity against a broad panel of solid rumors including several drug-resistant cell lines, and XK469 has low toxicity in comparison to other anticancer agents, it has been approved for phase I clinical evaluation, but the molecular mechanism of action of XK469 and its analogue remains unknown.TOPO II inhibitors have two isforms, TOPO II a inhibitor and TOPO IIB inhibitor, both adriamycin and etoposide are TOPO II a inhibitors, the difference between TOPO II a inhibitor and TOPO II B inhibitor remain unclear, and there is argue about their use.The oncogenesis and development of tumor are associated with the unbalance of cyclins - cyclin dependent kinases (CDKs) - cyclin dependent kinase inhibitors (CKIs) system that regulates cell cycle. Cyclin-dependent kinase-1 (CDK1) is one of the most important proteins of cell cycle. And the changes and effects of CDK1 in TOPO II inhibitors-induced growth inhibition in cancer cells are known little.14-3-3σ is a member of a family of proteins that regulate cellular activity by binding and sequestering phosphorylated proteins. Many celltypes treated with DNA-damageing agents arrest in the G2 phase of the cell cycle, then 14-3-3a gene is transcriptionally activated by p53 , and overexpress 14-3-3σ. Timothy A reported that 14-3-3cis required to prevent mitotic catastrophe after DNA damage, the 14-3-3σ-/- cells were unable to maintain cell-cycle arrest and died(mitotic catastrophe) as they entered mitosis, unlike the cells containing 14-3-3σ,though both cells initially attested in the G2 phase of the cell cycle after DNA damage. TOPO II inhibitors may induce 14-3-3c expression in H460 cell, but there is no report.To determine the effects of TOPO II inhibitors on lung cancer cells in vitro, to explore the roles of cdc2, phos-cdc2 and 14-3-3 o played in the signal transduction in TOPO II inhibitors-induced growth inhibition in lung cancer cell, to determine the importance of stuctrue to XK469, to find the difference between TOPO II a inhibitor and TOPO IIP inhibitor, we use these methods: fluorescence microscope was used to observe the morphological changes of cell cycle arrest in H460 cells induced by XK469, XN472, adrimycin and etoposide, the cell growth inhibit and the procession of cell cycle were assayed by MTT assay and FCM, the changes of expressions of cdc2, phos-cdc2 and 14-3-3 o were assayed by Western Blotting analysis.The results showed that XK469 could inhibit H460 cells growth in vitro in dose-dependent manners, after being treated for 24h, the cellular growth inhibitory rate were 65.96%(10ug/ml), 75%(20ug/ml), 81.1%(40ug/ml), 85.64%(80ug/ml), 88.57%(120ug/ml). And when there was 120h passed, the cellular growth inhibitory rate were 9.97%(10ug/ml), 26.4%(20ug/ml), 54.85%(40ug/ml), 59.17%80(ug/ml), 86.97%(120ug/ml). XN472 had a much lower inhibition effect on the H460 cell growth. Both adrimycin and etoposide could inhibit H460 cells growth in vitro too, in dose-dependent and time-dependent manners. After being treated with adrimycin for 24h, the cellular growth inhibitory rate were 11%(0.05ug/ml), 14.49%(0.1ug/ml), 31.19%(0.2ug/ml), 39.15%(0.3ug/ml), 42.19%(0.4ug/ml), and after beingtreated for 120h, the cellular growth inhibitory rate were 48.3%(0.05ug/ml),50.2%(0.1ug/ml), 63.24%(0... |
PDF Full Text Request