Hui Chun Wang

Withanolides-Induced Breast Cancer Cell Death Is Correlated with Their Ability to Inhibit Heat Protein 90

Withanolides are a large group of steroidal lactones found in Solanaceae plants that exhibit potential anticancer activities. We have previously demonstrated that a withanolide, tubocapsenolide A, induced cycle arrest and apoptosis in human breast cancer cells, which was associated with the inhibition of heat shock protein 90 (Hsp90). To investigate whether other withanolides are also capable of inhibiting Hsp90 and to analyze the structure-activity relationships, nine withanolides with different structural properties were tested in human breast cancer cells MDA-MB-231 and MCF-7 in the present study. Our data show that the 2,3-unsaturated double bond-containing withanolides inhibited Hsp90 function, as evidenced by selective depletion of Hsp90 client proteins and induction of Hsp70. The inhibitory effect of the withanolides on Hsp90 chaperone activity was further confirmed using in vivo heat shock luciferase activity recovery assays. Importantly, Hsp90 inhibition by the withanolides was correlated with their ability to induce cancer cell death. In addition, the withanolides reduced constitutive NF-κB activation by depleting IκB kinase complex (IKK) through inhibition of Hsp90. In estrogen receptor (ER)-positive MCF-7 cells, the withanolides also reduced the expression of ER, and this may be partly due to Hsp90 inhibition. Taken together, our results suggest that Hsp90 inhibition is a general feature of cytotoxic withanolides and plays an important role in their anticancer activity.

First total synthesis of antrocamphin A and its analogs as anti-inflammatory and anti-platelet aggregation agents

Naturally occurring antrocamphin A (1) is a potent anti-inflammatory compound from the edible fungus Antrodia camphorata (Taiwanofungus camphoratus), whose wild fruiting body is used as a valuable folk medicine in Taiwan. This study is the first total synthesis of antrocamphin A (1) and its analogs. Their inhibition ability on NO release, superoxide anion generation, elastase release and platelet aggregation are reported herein.

Inhibition of ATR-Dependent Signaling by Protoapigenone and Its Derivative Sensitizes Cancer Cells to Interstrand Cross-link–Generating Agents In Vitro and In Vivo

DNA damage caused during cancer treatment can rapidly activate the ataxia telangiectasia-mutated (ATM) and ATM and Rad3-related (ATR)-dependent phosphorylation of Chk2 and Chk1 kinases, which are hallmarks of the DNA damage response (DDR). Pharmacologic inhibition of ATR causes a synthetic lethal effect on ATM- or p53-defective cancers, suggesting that such inhibition is an effective way to improve the sensitivity of cancers to DNA-damaging agents. Here, both the natural compound protoapigenone (WYC02) and its synthetic derivative WYC0209 exhibited cytotoxic effects on various cancer cell lines. WYC02 causes chromosomal aberration in the mitotic spreads of Chinese hamster ovary cells. Interestingly, cancer cells did not exhibit typical DDR markers upon exposure to WYC02 and WYC0209 (WYCs). Further investigation into the molecular mechanisms of WYCs function revealed that they have a potential ability to inhibit DDR, particularly on activation of Chk1 and Fanconi anemia group D2 protein (FANCD2), but not Chk2. In this way, WYCs inhibited ATR-mediated DNA damage checkpoint and repair. Furthermore, when combined with the DNA cross-linking agent cisplatin, treatment with WYCs resulted in increased tumor sensitivity to interstrand cross-link–generating agents both in vitro and in vivo. Our results therefore especially implicate WYCs in enhancing tumor chemosensitivity when the ATR checkpoint is constitutively active in states of oncogene-driven replicative stress or tolerance to DNA-interfering agents. Mol Cancer Ther; 11(7); 1443–53. ©2012 AACR.

Antioxidant and Tyrosinase Inhibitory Constituents from a Desugared Sugar Cane Extract, a Byproduct of Sugar Production

Recycling agricultural resources has become an important issue worldwide promoting the economical value of agricultural production processes. Desugared sugar cane extract (DSE) from Saccharum officinarum is a byproduct obtained during sugar production. Two new neolignan glucosides, saccharnan A (1) and saccharnan B (2), together with 10 known phenolics (3-12) were isolated from DSE, and their structures were elucidated on the basis of NMR spectral analysis. Compounds 3, 4, 8, and 9 showed good activity against DPPH radical (IC(50) ≤ 51.20 μM) and compounds 3-8 and 12 exhibited strong ABTS(+) free radical scavenging activity (IC(50) ≤ 51.57 μM) compared to those of the positive controls, ascorbic acid and Trolox. Moreover, compounds 7 and 12 acted as potent tyrosinase inhibitors (IC(50) ≤ 42.59 μM) compared to the positive control arbutin. Our results highlighted the economical value of recycling DSE for the future development of natural antioxidants and/or tyrosinase inhibitors.

Using the pER8:GUS reporter system to screen for phytoestrogens from Caesalpinia sappan.

Arabidopsis thaliana pER8:GUS, a low-cost, highly efficient, and convenient transgenic plant system, was used to assay the estrogen-like activity of 30 traditional Chinese medicines. The MeOH extract of Caesalpinia sappan exhibited significant bioactivity in this assay, and subsequent bioactivity-guided fractionation of the extract led to the isolation of one new compound, (S)-3,7-dihydroxychroman-4-one (1), and 10 known compounds. Both the plant pER8:GUS and in vitro estrogen response element reporter assays were used to evaluate the estrogenic activity of the isolated compounds, and these two systems produced comparable results. Compounds 6, 8, and 11 showed significant estrogenic activity comparable to genistein. These active compounds were determined to be nontoxic new sources of phytoestrogens. In addition, compounds 2 and 3 inhibited ERE transcription induced by 17β-estradiol. A docking model revealed that compounds 6, 8, and 11 showed high affinity to the estrogen receptor. The pER8:GUS reporter system was demonstrated to be a useful and effective technique in phytoestrogen discovery.

Direct Semi-Synthesis of the Anticancer Lead-Drug Protoapigenone from Apigenin, and Synthesis of Further New Cytotoxic Protoflavone Derivatives

Protoapigenone, a natural flavonoid possessing an unusual p-quinol moiety on its B-ring, is a novel prospective anticancer agent with low toxicity that is currently in development. The first economical, one-step synthesis of protoapigenone from apigenin is described on up to gram scale. 13 new 1′-O-alkylflavone analogs were also synthesized, either from apigenin or β-naphthoflavone. The in vitro cytotoxic activity of each compound was tested on six human cancer cell lines (HepG2, Hep3B, Ca9-22, A549, MCF-7 and MDA-MB-231). In the case of 1′-O-alkyl-protoapigenone derivatives, structure-activity relationships were found depending on the side-chain, and protoapigenone 1′-O-butyl ether was found to exert significantly stronger activity against three of the cell lines (Hep3B, MCF-7 and MDA-MB-231) than its non-substituted analog, protoapigenone itself. In contrast to this, all β-naphthoflavone derivatives bearing the same pharmacophore on their B-ring showed decreased cytotoxic activities when substituted with an O-alkyl side-chain at position 1′, comparing to that of the non-substituted compound.

Active Constituents from Liriope platyphylla Root against Cancer Growth In Vitro

Liriope spicata is a well-known herb in traditional Chinese medicine, and its root has been clinically demonstrated to be effective in the treatment of metabolic and neural disorders. The constituents isolated from Liriope have also recently been shown to possess anticancer activity, although the mechanism of which remains largely unknown. Here, we illustrate the anticancer activity of LPRP-9, one of the active fractions we fractionated from the Liriope platyphylla root part (LPRP) extract. Treatment with LPRP-9 significantly inhibited proliferation of cancer cell lines MCF-7 and Huh-7 and down-regulated the phosphorylation of AKT. LPRP-9 also activates the stress-activated MPAK, JNK, p38 pathways, the p53 cell-cycle checkpoint pathway, and a series of caspase cascades while downregulating expression of antiapoptotic factors Bcl-2, Bcl-XL, and survivin. Such activities strongly suggest a role for LPRP-9 in apoptosis and autophagy. We further purified and identified the compound (−)-Liriopein B from LPRP-9, which is capable of inhibiting AKT phosphorylation at low concentration. The overall result highlights the anticancer property of LPRP-9, suggests its mechanism for inhibition of proliferation and promotion of cell death for cancer cells via regulation of multitarget pathways, and denotes the importance of purifying components of fraction LPRP-9 to aid cancer therapy.

Lower antioxidative capacity of multidrug-resistant cancer cells confers collateral sensitivity to protoflavone derivatives

AbstractPurposeMultidrug resistance (MDR) may develop due to a series of adaptive responses under a new stress conditions, such as chemotherapy. Novel strategies are urgently needed to fight MDR in cancer, and chemotherapeutics that are selective for MDR cancer cells offer a promising approach. Certain protoflavones were previously found to have potential in this regard.MethodsCytotoxicity of six protoflavones was assessed in different P-glycoprotein overexpressing MDR cancer cell lines and in their non-MDR counterparts. The impacts of compound 5, 6-methylprotoflavone previously published and a new derivative, 6-bromoprotoflavone (compound 6), on the cell cycle distribution were evaluated, and 6 was also studied for its potential to regulate the intracellular antioxidative capacity.Results Protoflavones showed a significant cytotoxicity against all cancer cell lines and selectivity toward MDR cancer cells adapted to conventional chemotherapeutics. Inverse sensitivity versus MDR selectivity pattern was observed. Treatment with H2O2 showed that MDR cancer cells are more vulnerable to oxidative stress. Compounds 5 and 6 significantly decreased the portion of MDR cells in the G1 phase. The levels of reactive oxygen and nitrogen species (ROS/RNS) between MDR and non-MDR cells significantly differed upon exposure to 6, accompanied by changes in the glutathione (GSH) levels and in the expression of manganese superoxide dismutase (MnSOD), glutathione-S-transferase π (GST π) and hypoxia-inducible factor-1α (HIF-1α).ConclusionsOur results suggest that MDR cancer cells can be more vulnerable to the pro-oxidative activity of protoflavones due to an impaired antioxidative defense that might arise during the adaptation processes provoked by chemotherapy.

Cubitanoids and Cembranoids from the Soft Coral Sinularia nanolobata

Two new cubitanoids, nanoculones A and B (1 and 2), and three new cembranoids, nanolobols A–C (3–5), as well as six known compounds, calyculone I (6), sinulariuol A (7), sinulariols C, D, H, and J (8–11), were isolated from the soft coral Sinularia nanolobata, collected off the coast of the eastern region of Taiwan. Their structures were elucidated on the basis of extensive spectroscopic analysis. Cytotoxicity of compounds 1–11 was evaluated. The nitric oxide (NO) inhibitory activity of selected compounds was further measured by assay of lipopolysaccharide (LPS)-stimulated NO production in activated RAW264.7 cells. The results showed that none of 1–11 exhibited cytotoxicity against the tested cancer cell lines, whereas compound 8 was found to significantly reduce NO production.

CLL2-1, a chemical derivative of orchid 1,4-phenanthrenequinones, inhibits human platelet aggregation through thiol modification of calcium-diacylglycerol guanine nucleotide exchange factor-I (CalDAG-GEFI).

CalDAG-GEFI is a guanine nucleotide exchange factor, which actives small GTPase Rap1 and plays an important role in platelet aggregation. Our previous study has shown that CalDAG-GEFI contains redox-sensitive thiols, and its function can be inhibited by thiol modification. In the present study, the effect of CLL2-1, a 1,4-phenanthrenequinone, on CalDAG-GEFI and platelet functions was investigated. In human platelets, CLL2-1 prevented platelet aggregation caused by various stimulators. Flow cytometric analysis revealed that CLL2-1 inhibited GPIIb/IIIa activation and P-selectin secretion. Moreover, CLL2-1 prevented Rap1 activation caused by thrombin, the Ca(2+) ionophore A23187, and the diacylglycerol mimetic phorbol 12-myristate 13-acetate, while only slightly inhibited thrombin-induced increases in [Ca(2+)]i and did not inhibit protein kinase C activation. Western blots after reducing SDS-PAGE showed that treatment of either platelets or platelet lysates with CLL2-1 led to a decrease of monomeric CalDAG-GEFI and appearance of cross-linked oligomers of CalDAG-GEFI, and these effects were inhibited by pretreatment of platelets or lysates with thiol reducing agents prior to the addition of CLL2-1, indicating thiol modification of CalDAG-GEFI by CLL2-1. Furthermore, the thiol reducing agents also prevented the inhibitory effect of CLL2-1 on Rap1 activation, GPIIb/IIIa activation, and platelet aggregation. In CalDAG-GEFI-overexpressing human embryonic kidney 293T cells, CLL2-1 also inhibited CalDAG-GEFI-mediated Rap1 activation. Taken together, our results suggest that the antiplatelet effect of CLL2-1 is due to, at least in part, inhibition of CalDAG-GEFI-mediated Rap1 activation, and provide the basis for development of novel antiplatelet drugs.