Article pubs.acs.org/jnp
Cite This: J. Nat. Prod. 2018, 81, 298−306
ent-Jungermannenone C Triggers Reactive Oxygen SpeciesDependent Cell Differentiation in Leukemia Cells Zongwei Yue,‡,# Xinhua Xiao,§,# Jinbao Wu,†,# Xiaozhou Zhou,† Weilong Liu,† Yaxi Liu,† Houhua Li,⊥ Guoqiang Chen,§ Yingli Wu,*,§ and Xiaoguang Lei*,† †
Beijing National Laboratory for Molecular Sciences, State Key Laboratory of Natural and Biomimetic Drugs, Key Laboratory of Bioorganic Chemistry and Molecular Engineering of Ministry of Education, Department of Chemical Biology, College of Chemistry and Molecular Engineering, Synthetic and Functional Biomolecules Center, and Peking-Tsinghua Center for Life Sciences, Peking University, Beijing 100871, People’s Republic of China ‡ School of Life Sciences, Peking University, Beijing 100871, People’s Republic of China § Hongqiao International Institute of Medicine, Shanghai Tongren Hospital/Faculty of Basic Medicine, Chemical Biology Division of Shanghai Universities E-Institutes, Key Laboratory of Cell Differentiation and Apoptosis of the Chinese Ministry of Education, Shanghai Jiao Tong University School of Medicine, Shanghai 200025, People’s Republic of China ⊥ Department of Chemical Biology, Max Planck Institute of Molecular Physiology, 44227 Dortmund, Germany S Supporting Information *
ABSTRACT: Acute myeloid leukemia (AML) is a hematologic malignancy that is characterized by clonal proliferation of myeloid blasts. Despite the progress that has been made in the treatment of various malignant hematopoietic diseases, the effective treatment of AML remains very challenging. Differentiation therapy has emerged as a promising approach for leukemia treatment, and new and effective chemical agents to trigger the differentiation of AML cells, especially drug-resistant cells, are urgently required. Herein, the natural product jungermannenone C, a tetracyclic diterpenoid isolated from liverworts, is reported to induce cell differentiation in AML cells. Interestingly, the unnatural enantiomer of jungermannenone C (1) was found to be more potent than jungermannenone C in inducing cell differentiation. Furthermore, compound 1 targets peroxiredoxins I and II by selectively binding to the conserved cysteine residues and leads to cellular reactive oxygen species accumulation. Accordingly, ent-jungermannenone C (1) shows potential for further investigation as an effective differentiation therapy against AML.
A
have been obtained for more elderly patients. Therefore, new chemotherapeutic strategies with better efficacy and safety need to be developed. Differentiation therapy is a new approach in cancer treatment that aims to impair the proliferative capacity of cancer cells and induce terminal differentiation or apoptosis.5,6 Compared with traditional chemotherapy, differentiation therapy is less toxic. Currently, all-trans-retinoic acid (ATRA)-induced differentiation therapy is being used successfully in the treatment of acute promyelocytic leukemia (APL), a subtype of AML.7 This treatment has dramatically improved the prognosis of APL patients, reaching a cure rate of greater than 96%. However, differentiation therapy is still limited to APL, as other non-APL leukemias are resistant to ATRA-induced cell differentiation. A deeper understanding of the molecular mechanism of leukemia cell differentiation might reveal novel targets and strategies to induce AML differentiation. In this respect, one promising
cute myeloid leukemia (AML), the most common acute leukemia affecting adults, is characterized by the rapid growth of clonal precursor myeloid cells with a reduced capacity for differentiation in the bone marrow as well as peripheral blood.1 As a malignant tumor, AML progresses rapidly and may be life-threatening within weeks or months without treatment. Currently, the main strategy for the treatment of AML is chemotherapy. Midostaurin, a smallmolecule kinase inhibitor with activity against the receptor tyrosine kinase FLT3, was recently approved by the U.S. Food and Drug Administration for the treatment of FLT3 mutant AML, which is a great step forward in AML theraupeutics.2 However, the potential of cytotoxic chemotherapies to treat AML might have reached a limit. The majority of patients with AML are greater than 60 years old, and in this segment of the population, high-dose chemotherapy is associated with high rates of morbidity and mortality. The cure rate is approximately 35−40% for patients under 60 years old, but only 5−15% for patients over 60 years old.3,4 Although the outcomes of younger patients have been steadily improving, fewer improvements © 2018 American Chemical Society and American Society of Pharmacognosy
Received: August 22, 2017 Published: February 2, 2018 298
DOI: 10.1021/acs.jnatprod.7b00722 J. Nat. Prod. 2018, 81, 298−306
Journal of Natural Products
Article
Figure 1. Cytotoxicity of jungermannenone C and ent-jungermannenone C (1). (a) Chemical structure of jungermannenone C. (b) Various tumor cell lines were treated with different concentrations of racemic (rac)-jungermannenone C for 24 h, and IC50 values were calculated to assess cytotoxic activity. White bars, lymphoma cells; hatched, leukemia cells; gray, solid tumor cells. (c) Peripheral blood mononuclear cells were exposed to different concentrations of rac-jungermannenone C for 24 h, and the percent cell viability was determined using a trypan blue exclusion assay. (d) The differences in the IC50 values of jungermannenone C and ent-jungermannenone C (1) reflect the higher cytotoxicity of the latter compound.
strategy to reveal molecular mechanisms is a chemical biology approach using small-molecule probes. For example, using natural products such as adenanthin and vibsanine A as chemical probes, through target identification and validation, researchers have revealed that peroxiredoxin and protein kinase C, respectively, are involved in inducing AML cell differentiation.8−10 These studies have prompted further research to identify and develop novel small molecules that induce AML cell differentiation. Tetracyclic diterpenoids isolated from plants have been reported to exhibit various and promising anti-inflammatory, antimicrobial, and antitumor properties.11,12 Liverworts, which grow widely around the world, contain high amounts of terpenoids as well as aromatic compounds.13,14 A small library of ent-kaurane diterpenoids isolated from this organism has been evaluated for potential antitumor activities, among which jungermannenones A−D have been shown to induce cancer cell apoptosis.15,16 However, the mode of action for these natural products is still not well-defined. Enabled by the ability to perform total synthesis of jungermannenones B and C, which was previously reported,17 a program to define their mode of action was initiated. Herein, it was found that jungermannenone C inhibits the proliferation of lymphoma/ leukemia cell lines and triggers AML cell differentiation. Recently, a second-generation route for the enantioselective total synthesis of jungermannenone C was developed (unpublished data), which made it possible to evaluate the biological activities of both its enantiomers. Interestingly, the enantiomer of natural jungermannenone C (ent-jungermannenone C) (1) was found to show better potential antitumor activity than jungermannenone C. Through chemical biology studies, it was found in the present investigation that ent-
jungermannenone C (1) targets peroxiredoxin I and II (Prx I and Prx II) and selectively binds to conserved cysteine residues of these two target proteins, leading to cellular reactive oxygen species (ROS) accumulation. Thus, ent-jungermannenone C (1) has been revealed as effective in inducing the differentiation of various AML cells and hence shows potential for further investigation as a differentiation therapy against AML.
■
RESULTS AND DISCUSSION Jungermannenone C Inhibits Cancer Cell Proliferation and Growth. The potential antitumor activities of the racemic form of jungermannenone C (rac-jungermannenone C) were evaluated by testing its ability to inhibit cell proliferation and growth in different cancer cell lines, including HeLa, MCF-7, HEPG2, SGC-7901, A549, and HT-29 cells and lymphoma/leukemia cell lines inclusive of Ramos, HL-60, SUDHL-2, SU-DHL-4, OCI-ly8, OCI-ly10, NB4-LR2, Raji, Jurkat, and K562 cells. These cell lines were treated with increasing concentrations of rac-jungermannenone C for 24 h, and cell viability was measured with a CellTiter-Glo Assay, which reflects celluar ATP levels. At high concentrations, racjungermannenone C treatment was cytotoxic to most cell lines tested. Compared with solid tumor cell lines, racjungermannenone C was more toxic to lymphoma/leukemia cells, with a half-maximal inhibitory dose (IC50) of
