Daurinol, a catalytic inhibitor of topoisomerase IIα, suppresses SNU-840 ovarian cancer cell proliferation through cell cycle arrest in S phase

Abstract

Abstract. Daurinol, a lignan from the ethnopharmacological plant Haplophyllum dauricum, was recently reported to be a novel topoisomerase II inhibitor and an alternative to the clinical anticancer agent etoposide based on a colorectal cancer model. In the present study, we elucidated the detailed biochemical mechanism underlying the inhibition of human topoisomerase IIα by daurinol based on a molecular docking study and in vitro biochemical experiments. The computational simulation predicted that daurinol binds to the ATP-binding pocket of topoisomerase IIα. In a biochemical assay, daurinol (10-100 µM) inhibited the catalytic activity of topo isomerase IIα in an ATP concentration-dependent manner and suppressed the ATP hydrolysis activity of the enzyme. However, daurinol did not inhibit topoisomerase I activity, most likely because topoisomerase I does not contain an ATP-binding domain. We also evaluated the anti-proliferative activity of daurinol in ovarian, small cell lung and testicular cancer cells, common target cancers treated with etoposide. Daurinol potently inhibited SNU-840 human ovarian cancer cell proliferation through cell cycle arrest in S phase, while etoposide induced G2/M phase arrest. Daurinol induced the increased expression of cyclin E, cyclin A and E2F-1, which are important proteins regulating S phase initiation and progression. Daurinol did not induce abnormal cell and nuclear enlargement in SNU-840 cells, in contrast to etoposide. Based on these data, we suggest that daurinol is a potential anticancer drug candidate for the treatment of human ovarian cancer with few side effects. IntroductionTopoisomerases are essential enzymes in all organisms that are involved in the topological homeostasis of DNA molecules during DNA replication, transcription and chromosomal segregation. Topoisomerases are classified into two classes, topoisomerase I and II, which create single and double-strand breaks, respectively. Because topoisomerases are crucial enzymes in DNA replication, they have served as primary targets for the development of anticancer agents (1,2). Topoisomerase II inhibitors such as etoposide, teniposide and doxorubicin have been extensively used in clinical cancer treatment. However, these agents also have undesirable side effects, including immunosuppression, myelosuppression, gastrointestinal toxicity and the development of secondary leukemia (3). Thus, the discovery of new topoisomerase inhibitors with fewer side effects from natural products has received a great deal of attention (4,5).Daurinol is a natural arylnaphthalene lignan isolated from the traditional medicinal plant Haplophyllum dauricum (6). According to an ethnopharmacological study, this plant has been used to treat tumors in Russia (7). The chemical structure of daurinol is similar to that of the clinical anticancer agent VP-16 (also known as etoposide phosphate). Recently, we suggested that daurinol could be a promising antitumor agent with minimal side effects, compared to etoposide, based on in vitro and in vivo resu...

Toxicological evaluation of the topoisomerase inhibitor, etoposide, in the model animal Caenorhabditis elegans and 3T3‐L1 normal murine cells

“…Recently, our group suggested that the abnormal nuclear enlargement induced by etoposide may correlate with the adverse effects of etoposide. In previous studies, we demonstrated that etoposide induces the formation of giant cell shapes in in vitro human cancer cell lines, but we could not observe these phenomena in cultured normal cells or in vivo animal models. In addition, etoposide by‐products are detected in river and wastewater samples .…”

“…The morphology of the 3T3‐L1 cells treated with etoposide was observed using a phase contrast microscope (CK40, Olympus, Tokyo, Japan). We also evaluated the distribution of FSC‐H values, which correspond to the cell size, using flow cytometry analysis according to the previously described method …”

Proposal of Dual Inhibitor Targeting ATPase Domains of Topoisomerase II and Heat Shock Protein 90

“…Daurinol is a lignan isolated from Haplophyllum dauricum , whose structure is similar to etoposide (Kang et al ., 2014). Etoposide is a well-known cytotoxic anti-cancer drug functioning as a topo II poison.…”

Synthesis and anticancer activity of 4-aza-daurinol derivatives

“…Based on the experimental data, daurinol is thought to be superior to etoposide in terms of side effects but with equipotent anticancer activity. More recently, daurinol has been proved to be active against ovarian, small-cell lung, and testicular cancer cells (Kang et al 2014). It was proposed that daurinol could be part of a novel class of low-toxicity antitumor agents (Kang et al 2011).…”