A Novel Topoisomerase Inhibitor, Daurinol, Suppresses Growth of HCT116 Cells with Low Hematological Toxicity Compared to Etoposide

Abstract

We report that daurinol, a novel arylnaphthalene lignan, is a promising potential anticancer agent with adverse effects that are less severe than those of etoposide, a clinical anticancer agent. Despite its potent antitumor activity, clinical use of etoposide is limited because of its adverse effects, including myelosuppression and the development of secondary leukemia. Here, we comprehensively compared the mechanistic differences between daurinol and etoposide because they have similar chemical structures. Etoposide, a topoisomerase II poison, is known to attenuate cancer cell proliferation through the inhibition of DNA synthesis. Etoposide treatment induces G(2)/M arrest, severe DNA damage, and the formation of giant nuclei in HCT116 cells. We hypothesized that the induction of DNA damage and nuclear enlargement due to abnormal chromosomal conditions could give rise to genomic instability in both tumor cells and in actively dividing normal cells, resulting in the toxic adverse effects of etoposide. We found that daurinol is a catalytic inhibitor of human topoisomerase IIa, and it induces S-phase arrest through the enhanced expression of cyclins E and A and by activation of the ATM/Chk/Cdc25A pathway in HCT116 cells. However, daurinol treatment did not cause DNA damage or nuclear enlargement in vitro. Finally, we confirmed the in vivo antitumor effects and adverse effects of daurinol and etoposide in nude mice xenograft models. Daurinol displayed potent antitumor effects without any significant loss of body weight or changes in hematological parameters, whereas etoposide treatment led to decreased body weight and white blood cell, red blood cell, and hemoglobin concentration.

Potent cytotoxic arylnaphthalene lignan lactones from Phyllanthus poilanei

“…Some specific diphyllin analogues might exert their cytotoxicity through a mechanism of action different from that of etoposide, 32,33 as supported by additional chemical and biological studies for an arylnaphthalene lignan lactone, daurinol, which did not induce the formation of open circular and linear DNA that originated from the topoisomerase-DNA cleavable intermediate. 31 Apoptosis, or programmed cell death, occurs during normal cellular differentiation and the development of multicellular organisms. 44,45 To remain malignant, cancer cells must evade apoptosis to avoid elimination, and many anticancer agents induce cancer cell apoptosis.…”

“…9,10,16,19,22,24,30,31 For example, justicidin A (a methylated diphyllin derivative) isolated from Justicia ciliata showed cytotoxicity toward several human cancer cell lines with IC 50 values in the range 2−7 ng/mL. 9 Justicidin B, a dehydroxylated diphyllin, was cytotoxic toward SKW-3 chronic lymphoid leukemia cells.…”

“…30 In an in vivo experiment, five-week-old athymic male nude mice (BALB/c Slc-nu) bearing tumor xenografts established by subcutaneous injections of HCT116 cells were treated by intraperitoneal (ip) injection of daurinol (1,5,10, and 20 mg/ kg, 3 times weekly for 2 weeks); this compound displayed antitumor effects at several doses used when compared with the vehicle control. 31 In an effort to develop these agents into new anticancer drugs, several analogues of diphyllin glycosides have been synthesized and evaluated. 32,33 Many of these substances showed potent cytotoxicity toward a number of human cancer cells, with some of them acting as topo II poisons but others showing a lack of this activity.…”

Topoisomerase IIα, rather than IIβ, is a promising target in development of anti-cancer drugs

“…Daurinol (14), a novel arylnaphthalene lignan isolated from the ethnopharmacological plant Haplophyllum dauricum, has potent catalytic inhibition of human TOP2α and induces S phase cell cycle arrest through the enhanced expression of cyclins E and A and by activation of the ATM/Chk/Cdc25A pathway in HCT116 cells (48). Unlike etoposide, daurinol did not cause DNA damage or nuclear enlargement in vitro.…”

“…Nowadays, Biz is a promising TOP2α inhibitor that could be developed into a drug (31,44,45). Natural products are still the main source of TOP2α-targeting agents since more effective novel etoposide-related natural products continue to be isolated (48,58). Podophyllotoxin derivatives might be a safer anticancer drug, but the majority of TOP II-targeting compounds are (semi)synthetic products, so the design and synthesis of podophyllotoxin derivatives may have good prospects.…”