Juan Cheng Yang

Selective targeting of breast cancer cells through ROS-mediated mechanisms potentiates the lethality of paclitaxel by a novel diterpene, gelomulide K

Defects in apoptotic pathways confer resistance to tubulin-binding agents via downregulation of caspases or overexpression of antiapoptotic factors, urging the need for novel agents acting on an alternative pathway. The purpose of this study was to investigate whether induction of ROS can induce caspase-independent cell death in breast cancer cells and thereby enhance the activity of paclitaxel. Here, we report that gelomulide K acts as a caspase-independent cell death-inducing agent that synergizes with paclitaxel in breast cancer cells and has low toxicity in normal cells. Treatment with gelomulide K induced PARP-1 hyperactivation, AIF nuclear translocation, and cytoprotective autophagy. These effects were associated with increased ROS production and a decrease in cellular GSH levels in cancer cells. Furthermore, pretreatment with NAC, a precursor of intracellular GSH, effectively abrogated gelomulide K-induced caspase-independent cell death and autophagy, suggesting that ROS-mediated downstream signaling is essential to the anticancer effects of gelomulide K. Additionally, in a xenograft model, gelomulide K induced PARP-1 activation and reduced tumor growth. In terms of structure-activity relationships, analysis not only showed a correlation between ROS levels and drug activity but also highlighted the importance of the 8,14-epoxy group. Taken together, our results show that enhancement of paclitaxel activity can be achieved with gelomulide K and that the structurally relevant pharmacophore provides important insight into the development of new caspase-independent cell death-inducing agents.

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.

Anti-Inflammatory Spirostanol and Furostanol Saponins from Solanum macaonense.

Eight new spirostanol saponins, macaosides A-H (1-8), and 10 new furostanol saponins, macaosides I-R (9-18), together with six known spirostanol compounds (19-24) were isolated from Solanum macaonense. The structures of the new compounds were determined from their spectroscopic data, and the compounds were tested for in vitro antineutrophilic inflammatory activity. It was found that both immediate inflammation responses including superoxide anion generation and elastase release were significantly inhibited by treatment with compounds 20, 21, and 24 (superoxide anion generation: IC50 7.0, 7.6, 4.0 μM; elastase release: IC50 3.7, 4.4, 1.0 μM, respectively). However, compounds 1 and 4 exhibited effects on the inhibition of elastase release only, with IC50 values of 3.2 and 4.2 μM, respectively, while 19 was active against superoxide anion generation only, with an IC50 value of 6.1 μM. Accordingly, spirostanols may be promising lead compounds for further neutrophilic inflammatory disease studies.

ATR-Chk1 signaling inhibition as a therapeutic strategy to enhance cisplatin chemosensitivity in urothelial bladder cancer.

DNA damage responses contribute to cisplatin resistance; however, therapeutic strategies to overcome cisplatin resistance have not yet been established. Here, we demonstrate that inhibition of ATR-Chk1 pathway with the potent inhibitor WYC0209 sensitizes bladder cancer cells to cisplatin. In the clinical microarray profile, high ATR expression is associated with poor prognosis in bladder cancer patients who receive chemotherapy. We show that pharmacological and genetic suppressing of ATR sensitized cells to cisplatin. Treatment with WYC0209 or siATR increased levels of cisplatin-DNA adducts, concomitant with decreased levels of p-glycoprotein expression. Additionally, Combinations of cisplatin and WYC0209 show synergistic activity against bladder cancer. Ultimately, WYC0209 enhanced the anti-tumor effects of cisplatin and suppressed p-glycoprotein expression in bladder cancer xenografts. These results indicate that inhibiting ATR-Chk1 activation with WYC0209 suppresses p-glycoprotein expression and increases cisplatin activity in bladder cancer. Our findings collectively suggest that ATR-Chk1 is a target for improving the efficacy of cisplatin in bladder cancer.

Tackling the cytotoxic effect of a marine polycyclic quinone-type metabolite: Halenaquinone Induces molt 4 cells apoptosis via oxidative stress combined with the inhibition of HDAC and topoisomerase activities

A marine polycyclic quinone-type metabolite, halenaquinone (HQ), was found to inhibit the proliferation of Molt 4, K562, MDA-MB-231 and DLD-1 cancer cell lines, with IC50 of 0.48, 0.18, 8.0 and 6.76 μg/mL, respectively. It exhibited the most potent activity against leukemia Molt 4 cells. Accumulating evidence showed that HQ may act as a potent protein kinase inhibitor in cancer therapy. To fully understand the mechanism of HQ, we further explored the precise molecular targets in leukemia Molt 4 cells. We found that the use of HQ increased apoptosis by 26.23%–70.27% and caused disruption of mitochondrial membrane potential (MMP) by 17.15%–53.25% in a dose-dependent manner, as demonstrated by Annexin-V/PI and JC-1 staining assays, respectively. Moreover, our findings indicated that the pretreatment of Molt 4 cells with N-acetyl-l-cysteine (NAC), a reactive oxygen species (ROS) scavenger, diminished MMP disruption and apoptosis induced by HQ, suggesting that ROS overproduction plays a crucial rule in the cytotoxic activity of HQ. The results of a cell-free system assay indicated that HQ could act as an HDAC and topoisomerase catalytic inhibitor through the inhibition of pan-HDAC and topoisomerase IIα expression, respectively. On the protein level, the expression of the anti-apoptotic proteins p-Akt, NFκB, HDAC and Bcl-2, as well as hexokinase II was inhibited by the use of HQ. On the other hand, the expression of the pro-apoptotic protein Bax, PARP cleavage, caspase activation and cytochrome c release were increased after HQ treatment. Taken together, our results suggested that the antileukemic effect of HQ is ROS-mediated mitochondrial apoptosis combined with the inhibitory effect on HDAC and topoisomerase activities.