Chamaecypanone C, a novel skeleton microtubule inhibitor, with anticancer activity by trigger caspase 8-Fas/FasL dependent apoptotic pathway in human cancer cells
Graphical abstract
Introduction
Chemotherapy for the treatment of cancer was introduced into the clinic more than fifty years ago. Most chemotherapeutic anticancer drugs used in the clinic today include agents that target the cell cycle in order to inhibit the hyperproliferation state of tumor cells and – subsequently – to induce apoptosis, which is the desired outcome of chemotherapy [1]. Otherwise, the primary hurdle for effective cancer chemotherapy has been the intrinsic or acquired resistance of cancer cells to a variety of anticancer agents with distinct chemical structures or mechanism of action, a phenomenon known as multidrug resistance (MDR). The classical form of MDR involves the overexpression of drug efflux transporters such as P-glycoprotien (P-gp170/MDR) and multidrug resistance-associated proteins (MRPs) in the cell membrane, which pump anticancer drugs out of the cells, resulting in low intracellular drug concentrations [2], [3]. Therefore, there is necessary to discover the novel chemotherapeutic agents which could overcome MDR.
Historically, plants were a traditional source of medicinal agents. As modern medicine has evolved, numerous useful drugs were developed from lead compounds discovered from plants [4]. For examples, many current chemotherapeutic drugs, including bleomycin, doxorubicin, mitomycin, vinblastine, vincristine, etoposide (VP16), topotecan, irinotecan, paclitaxel and combretastatins, are natural products or their derivatives [5]. Thus, pharmacologically active compounds from plants represent an important pool for new investigative drugs [6], [7], [8], [9], [10].
Chamaecyparis obtusa var. formosana Rehd. (Taiwan hinoki; Cupressaceae) is a type of timber which is highly available in Taiwan. We have previously investigated the chemical components of the heartwood of this plant and found various monoterpenes, sesquiterpenes, diterpenes and lignans [11], [12], [13], [14]. Other than those phytochemicals, a novel skeleton compound, chamaecypanone C (Fig. 1), had been elucidated as a dimeric of monoterpene and norlignan with tricycle[5.2.2.02.6]undecane, also isolated from the heartwood of this plant [12]. Notably, this novel compound exhibited better growth inhibition properties with IC50 values ranging from 190 to 520 nM in three different human cancer cell lines, as compare to the clinically available anticancer drug VP16 [12]. However, the detailed molecular functions of this compound have not been dissected previously. In the present study, we investigated the mechanism of action of chamaecypanone C. We further determine the anticancer efficacy of this compound in various human cancer cells with multidrug resistant properties.
Section snippets
Purification of Chamaecypanone C
The compound was isolated at the College of pharmacy, China Medical University (Taichung, Taiwan) with use of the method described by Chien et al. [12]. In brief, the air-dried slices of heartwood of C. obtusa var. formosana were extracted with acetone at room temperature. After evaporation of acetone, the extract was partitioned with an ethyl acetate–water mixture to give an ethyl acetate-soluble fraction and an aqueous phase. The ethyl acetate-soluble fraction was repeatedly chromatographed
Chamaecypanone C induced growth inhibition in human cancer cell lines
Initial experiments were conducted for evaluation of growth inhibition by Chamaecypanone C against various types of human cancers in vitro. The results showed that Chamaecypanone C inhibited the growth of several human cancer cell lines including KB, which was originally derived from an epidermal carcinoma of the mouth but has now been shown to have HeLa characteristics, HONE-1 (nasopharyngeal carcinoma), TSGH (gastric carcinoma), CL1-0 and CL1-5 (lung adenocarcinoma) cells, with IC50 values
Discussion
In the past three decades, microtubules continue to be one of the most successful cancer chemotherapeutic targets [18], [19], [20], [21], [22]. Taxenes and Vinca alkaloids are well-characterized anti-mitotic compounds which are widely used in clinical situations. However, the development of multidrug resistance limited the potency of these anti-mitotic compounds [23]. Therefore, there has been a great interest in identifying novel microtubule inhibitors that can overcome various modes of
Acknowledgements
This work was supported in part by grants from National Health Research Institutes, Taipei, Taiwan (NHRI intramural grant CA-098-PP-02), the National Science Council, Taipei, Taiwan (NSC98-2323-B-400-004), and China Medical University, Taichung, Taiwan (CMU98-CT-01).
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