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

Abstract

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.

Inhibitory effect of riccardin D on growth of human non-small cell lung cancer: In vitro and in vivo studies

“…Topo II-mediated supercoiled pBR322 DNA relaxation assay DNA topo II activity was estimated by the supercoiled pBR322 DNA relaxation assay as described previously [9,24]. The .…”

“…Riccardin D was found to have an anticancer activity on human leukemia cell lines HL-60, K562 and its MDR counterpart K562/A02. Riccardin D might induce leukemia cell apoptosis through the inhibition of DNA topo II [9]. Another study suggested that riccardin D might hold the activity of antiangiogenesis as demonstrated in human umbilical vein vascular endothelial cells (HUVEC) and lung carcinoma H460 xenografts in mice [10].…”

Therapeutic potential of bryophytes and derived compounds against cancer

“…Riccardin D, isolated from a Chinese liverwort was found to possess pronounced antiproliferative effect on human leukemia cell lines HL-60, K562 and MDR K562/A02 cells. No induction of apoptosis in topoisomerase-II-deficient HL-60/MX2 cells indicates the mode of action of riccardin D is DNA topoisomerase-II dependent [132] .…”

Reversal of the multidrug resistance of human ileocecal adenocarcinoma cells by acetyl-11-keto-β-boswellic acid <i>via</i> downregulation of P-glycoprotein signals

“…RNA quality was determined based on the ratio of A260/ A280 (1.8-2). The concentration of total RNA was measured by detecting absorbance at 260 nm (A260) (18). Then, reverse transcription (RT) was performed with 2 μg of extracted RNA using the First Strand cDNA Synthesis Kit (Toyobo, Osaka, Japan) according to the supplied protocol.…”