title: Gambogic acid inhibits the catalytic activity of human topoisomerase IIalpha by binding to its ATPase domain.
abstract: This study is intended to characterize the cellular target of gambogic acid (GA), a natural product isolated from the gamboge resin of Garcinia hurburyi tree, which possesses potent in vitro and in vivo antitumor activities. The antiproliferative activity of GA was further confirmed here in a panel of human tumor cells and multidrug-resistant cells. We found that GA significantly inhibited the catalytic activity of topoisomerase (Topo) II and, to a comparatively less extent, of Topo I, without trapping and stabilizing covalent topoisomerase-DNA cleavage complexes. Down-regulation of Topo IIalpha but not Topo I and Topo IIbeta, reduced GA-induced apoptosis and the phosphorylation of c-Jun, and restored cell proliferation upon GA treatment. Moreover, GA antagonized etoposide-induced DNA damage and abrogated the antiproliferative activity of etoposide, whereas it did not affect camptothecin-induced DNA damage. By dissecting the actions of GA on the individual steps of Topo IIalpha catalytic cycle, we found that GA inhibited DNA cleavage and ATP hydrolysis. Moreover, GA directly bound to the ATPase domain of Topo IIalpha, and may share common binding sites with ATP. The results reported here show that GA exerts its antiproliferative effect by inhibiting the catalytic activity Topo IIalpha. They also indicate that GA inhibits Topo IIalpha-mediated DNA cleavage and modulate the activity of Topo II poisons, which provide rationale for further clinical evaluation of GA.
authors: Division of Antitumor Pharmacology, State Key Laboratory of Drug Research, Shanghai Institute of Materia Medica, Chinese Academy of Sciences, 555 Zu Chong Zhi Road, Zhangjiang Hi-Tech Park, Shanghai 201203, PR China.
authors: Yuxin
authors: Y
authors: Qin
authors: Linghua
authors: L
authors: Meng
authors: Chaoxin
authors: C
authors: Hu
authors: Wenhu
authors: W
authors: Duan
authors: Zhili
authors: Z
authors: Zuo
authors: Liping
authors: L
authors: Lin
authors: Xiongwen
authors: X
authors: Zhang
authors: Jian
authors: J
authors: Ding
mesh_terms: D000251:Adenosine Triphosphatases / Q000737:chemistry / Q000378:metabolism*; D000255:Adenosine Triphosphate / Q000378:metabolism; D000951:Antigens, Neoplasm / Q000378:metabolism; D000970:Antineoplastic Agents / Q000494:pharmacology; D017209:Apoptosis / Q000187:drug effects; D015153:Blotting, Western; D049109:Cell Proliferation / Q000187:drug effects; D004249:DNA Damage / Q000187:drug effects; D004250:DNA Topoisomerases, Type II / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000037:antagonists & inhibitors* / Q000378:metabolism; D019008:Drug Resistance, Neoplasm; D005047:Etoposide / Q000494:pharmacology; D005434:Flow Cytometry; D019450:Genes, MDR; D006367:HeLa Cells; D006801:Humans; D006868:Hydrolysis; D048031:JNK Mitogen-Activated Protein Kinases / Q000378:metabolism; D009369:Neoplasms / Q000188:drug therapy* / Q000378:metabolism; D010766:Phosphorylation / Q000187:drug effects; D034622:RNA Interference; D020349:Surface Plasmon Resonance; D059005:Topoisomerase II Inhibitors; D014410:Tumor Stem Cell Assay; D044004:Xanthones / Q000494:pharmacology*
chemical_list: D000951:Antigens, Neoplasm; D000970:Antineoplastic Agents; D004268:DNA-Binding Proteins; D059005:Topoisomerase II Inhibitors; D044004:Xanthones; D005047:Etoposide; D000255:Adenosine Triphosphate; C052659:gambogic acid; D048031:JNK Mitogen-Activated Protein Kinases; D000251:Adenosine Triphosphatases; D004250:DNA Topoisomerases, Type II