title: The Topoisomerase 1 Inhibitor Austrobailignan-1 Isolated from Koelreuteria henryi Induces a G2/M-Phase Arrest and Cell Death Independently of p53 in Non-Small Cell Lung Cancer Cells.
abstract: Koelreuteria henryi Dummer, an endemic plant of Taiwan, has been used as a folk medicine for the treatment of hepatitis, enteritis, cough, pharyngitis, allergy, hypertension, hyperlipidemia, and cancer. Austrobailignan-1, a natural lignan derivative isolated from Koelreuteria henryi Dummer, has anti-oxidative and anti-cancer properties. However, the effects of austrobailignan-1 on human cancer cells have not been studied yet. Here, we showed that austrobailignan-1 inhibited cell growth of human non-small cell lung cancer A549 and H1299 cell lines in both dose- and time-dependent manners, the IC50 value (48 h) of austrobailignan-1 were 41 and 22 nM, respectively. Data from flow cytometric analysis indicated that treatment with austrobailignan-1 for 24 h retarded the cell cycle at the G2/M phase. The molecular event of austrobailignan-1-mediated G2/M phase arrest was associated with the increase of p21Waf1/Cip1 and p27Kip1 expression, and decrease of Cdc25C expression. Moreover, treatment with 100 nM austrobailignan-1 for 48 h resulted in a pronounced release of cytochrome c followed by the activation of caspase-2, -3, and -9, and consequently induced apoptosis. These events were accompanied by the increase of PUMA and Bax, and the decrease of Mcl-1 and Bcl-2. Furthermore, our study also showed that austrobailignan-1 was a topoisomerase 1 inhibitor, as evidenced by a relaxation assay and induction of a DNA damage response signaling pathway, including ATM, and Chk1, Chk2, γH2AX phosphorylated activation. Overall, our results suggest that austrobailignan-1 is a novel DNA damaging agent and displays a topoisomerase I inhibitory activity, causes DNA strand breaks, and consequently induces DNA damage response signaling for cell cycle G2/M arrest and apoptosis in a p53 independent manner.
authors.affiliation: Institute of Medicine, Chung Shan Medical University, Taichung, Taiwan, ROC; Department of Medical Research, Chung-Shan Medical University Hospital, Taichung, Taiwan, ROC.
authors.forename: Chun-Chi
authors.initials: CC
authors.lastname: Wu
authors.affiliation: Department of Applied Chemistry, Providence University, Taichung, Taiwan, ROC.
authors.forename: Keh-Feng
authors.initials: KF
authors.lastname: Huang
authors.affiliation: Division of Chest Medicine, Department of Internal Medicine, Taichung Veterans General Hospital, Taichung, Taiwan, ROC; Department of Medicine, School of Medicine, National Yang-Ming University, Taipei, Taiwan, ROC.
authors.forename: Tsung-Ying
authors.initials: TY
authors.lastname: Yang
authors.affiliation: Department of Medical Research, Taichung Veterans General Hospital, Taichung, Taiwan, ROC.
authors.forename: Ya-Ling
authors.initials: YL
authors.lastname: Li
authors.affiliation: Taiwan Seed Improvement and Propagation Station, Council of Agriculture, Propagation Technology Section, Taichung, Taiwan, ROC.
authors.forename: Chi-Luan
authors.initials: CL
authors.lastname: Wen
authors.affiliation: Department of Medical Research, Taichung Veterans General Hospital, Taichung, Taiwan, ROC.
authors.forename: Shih-Lan
authors.initials: SL
authors.lastname: Hsu
authors.affiliation: Department of Health and Nutrition, Chia Nan University of Pharmacy & Science, Tainan, Taiwan, ROC.
authors.forename: Tzu-Hsiu
authors.initials: TH
authors.lastname: Chen
mesh_terms: D002289:Carcinoma, Non-Small-Cell Lung / Q000188:drug therapy* / Q000378:metabolism / Q000473:pathology; D016923:Cell Death / Q000187:drug effects; D045744:Cell Line, Tumor; D004264:DNA Topoisomerases, Type I / Q000378:metabolism*; D059565:G2 Phase Cell Cycle Checkpoints / Q000187:drug effects*; D006801:Humans; D017705:Lignans / Q000737:chemistry / Q000494:pharmacology*; D008175:Lung Neoplasms / Q000188:drug therapy* / Q000378:metabolism / Q000473:pathology; D059566:M Phase Cell Cycle Checkpoints / Q000187:drug effects*; D010946:Plants, Medicinal / Q000737:chemistry*; D059004:Topoisomerase I Inhibitors / Q000737:chemistry / Q000494:pharmacology*; D016159:Tumor Suppressor Protein p53 / Q000378:metabolism*
chemical_list: D017705:Lignans; C495901:TP53 protein, human; D059004:Topoisomerase I Inhibitors; D016159:Tumor Suppressor Protein p53; C093023:austrobailignan 1; D004264:DNA Topoisomerases, Type I