Riccardin D, a novel macrocyclic bisbibenzyl, induces apoptosis of human leukemia cells by targeting DNA topoisomerase II

• Published in: Investigational new drugs 2012-02, Vol.30 (1), p.212-222
• Main Authors: Xue, Xia, Qu, Xian-Jun, Gao, Zu-Hua, Sun, Cui-Cui, Liu, Hui-Ping, Zhao, Cui-Rong, Cheng, Yan-Na, Lou, Hong-Xiang
• Format: Article
• Language: English
• Subjects: Antineoplastic Agents, Phytogenic - pharmacology; Apoptosis; Apoptosis - drug effects; ATP Binding Cassette Transporter, Sub-Family B; ATP-Binding Cassette, Sub-Family B, Member 1 - metabolism; Caspase 3 - metabolism; Caspase 9 - metabolism; Cell culture; Cell growth; Cell Proliferation - drug effects; Cytochrome; Cytochromes c - metabolism; DNA Fragmentation; DNA Topoisomerases, Type II - metabolism; DNA, Superhelical - metabolism; Dose-Response Relationship, Drug; Drug resistance; Drug Resistance, Multiple; Drug Resistance, Neoplasm; Drugs; Enzymes; Glycerol; Glycoproteins; HL-60 Cells; Humans; Inhibitor drugs; K562 Cells; Laboratories; Leukemia; Leukemia - enzymology; Leukemia - genetics; Leukemia - pathology; Medicine; Medicine & Public Health; Oncology; Pharmacology; Pharmacology/Toxicology; Phenyl Ethers - pharmacology; Phosphatidylserines - metabolism; Poly(ADP-ribose) Polymerases - metabolism; Preclinical Studies; Stilbenes - pharmacology; Studies; Time Factors; Topoisomerase II Inhibitors - pharmacology
• ISSN: 0167-6997; 1573-0646
• DOI: 10.1007/s10637-010-9554-8

Summary We studied the effect of riccardin D, a macrocyclic bisbibenzyl, which was isolated from the Chinese liverwort plant, on human leukemia cells and the underlying molecular mechanism. Riccardin D had a significant antiproliferative effect on human leukemia cell lines HL-60, K562 and its multidrug resistant (MDR) counterpart K562/A02 cells, but showed no effect on the topoisomerase-II-deficient HL-60/MX2 cells, as measured by the 3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyltetrazolium bromide (MTT) assay. The pBR322 DNA relaxation assay revealed that riccardin D selectively inhibited the activity of topoisomerase II (topo II). The suppression of topo II activity by riccardin D was stronger than that of etoposide, a known topo II inhibitor. After treatment with riccardin D, nuclear extracts of leukemia K562 and K562/A02 cells left the majority of pBR322 DNA in a supercoiled form. Further examination showed that riccardin D effectively induced HL-60, K562 and K562/A02 apoptosis as evidenced by externalization of phosphatidylserine and formation of DNA ladder fragments. The activation of cytochrome c, caspase-9, caspase-3 and cleaved poly ADP-ribose polymerase (PARP) was also enhanced, as estimated by Western blot analysis. By contrast, riccardin D was unable to induce apoptosis in the topoisomerase-II-deficient HL-60/MX2 cells, indicating that the induction of apoptosis by riccardin D was due to the inhibition of topo II activity. In addition, riccardin D was able to significantly decrease P-glycoprotein (P-gp) expression in K562/A02 cells. Taken together, our data demonstrate that riccardin D is a novel DNA topo II inhibitor which can induce apoptosis of human leukemia cells and that it has therapeutic potential for both regular and MDR strains of leukemia cells.