2-Ethoxystypandrone, a novel small-molecule STAT3 signaling inhibitor from Polygonum cuspidatum, inhibits cell growth and induces apoptosis of HCC cells and HCC Cancer stem cells.

BACKGROUND: Signal transducer and activator of transcription 3 (STAT3) is an oncogene constitutively activated in hepatocellular carcinoma (HCC) cells and HCC cancer stem cells (CSCs). Constitutively activated STAT3 plays a pivotal role in holding cancer stemness of HCC CSCs, which are essential for hepatoma initiation, relapse, metastasis and drug resistance. Therefore, STAT3 has been validated as a novel anti-cancer drug target and the strategies targeting HCC CSCs may bring new hopes to HCC therapy. This study aimed to isolate and identify small-molecule STAT3 signaling inhibitors targeting CSCs from the ethyl acetate (EtOAc) extract of the roots of Polygonum cuspidatum and to evaluate their in vitro anti-cancer activities. METHODS: The chemical components of the EtOAc extract and the subfractions of P. cuspidatum were isolated by using various column chromatographies on silical gel, Sephadex LH-20, and preparative HPLC. Their chemical structures were then determined on the basis of spectroscopic data including NMR, MS and IR analysis and their physicochemical properties. The inhibitory effects of the isolated compounds against STAT3 signaling were screened by a STAT3-dependent luciferase reporter gene assay. The tyrosine phosphorylation of STAT3 was examined by Western Blot analysis. In vitro anti-cancer effects of the STAT3 pathway inhibitor were further evaluated on cell growth of human HCC cells by a MTT assay, on self-renewal capacity of HCC CSCs by the tumorsphere formation assay, and on cell cycle and apoptosis by flow cytometry analysis, respectively. RESULTS: The EtOAc extract of the roots of P. cuspidatum was investigated and a novel juglone analogue 2-ethoxystypandrone (1) along with seven known compounds (2-8) was isolated. Among the eight isolated compounds 1-8, 2-ethoxystypandrone was a novel and potent STAT3 signaling inhibitor (IC50 = 7.75 ± 0.18 µM), and inhibited the IL-6-induced and constitutive activation of phosphorylation of STAT3 in HCC cells. Moreover, 2-ethoxystypandrone inhibited cell survival of HCC cells (IC50 = 3.69 ± 0.51 µM ~ 20.36 ± 2.90 µM), blocked the tumorspheres formation (IC50 = 2.70 ± 0.28 µM), and induced apoptosis of HCC CSCs in a dose-dependent manner. CONCLUSION: A novel juglone analogue 2-ethoxystypandrone was identified from the EtOAc extract of the roots of P. cuspidatum and was demonstrated to be a potent small-molecule STAT3 signaling inhibitor, which strongly blocked STAT3 activation, inhibited proliferation, and induced cell apoptosis of HCC cells and HCC CSCs. 2-Ethoxystypandrone as a STAT3 signaling inhibitor might be a promising lead compound for further development into an anti-CSCs drug.

2-Methoxystypandrone inhibits signal transducer and activator of transcription 3 and nuclear factor-κB signaling by inhibiting Janus kinase 2 and IκB kinase.

Constitutive activation of the signal transducer and activator of transcription 3 (STAT3) or the nuclear factor-κB (NF-κB) pathway occurs frequently in cancer cells and contributes to oncogenesis. The activation of Janus kinase 2 (JAK2) and IκB kinase (IKK) are key events in STAT3 and NF-κB signaling, respectively. We have identified 2-methoxystypandrone (2-MS) from a traditional Chinese medicinal herb Polygonum cuspidatum as a novel dual inhibitor of JAK2 and IKK. 2-MS inhibits both interleukin-6-induced and constitutively-activated STAT3, as well as tumor necrosis factor-α-induced NF-κB activation. 2-MS specifically inhibits JAK and IKKß kinase activities but has little effect on activities of other kinases tested. The inhibitory effects of 2-MS on STAT3 and NF-κB signaling can be eliminated by DTT or glutathione and can last for 4 h after a pulse treatment. Furthermore, 2-MS inhibits growth and induces death of tumor cells, particularly those with constitutively-activated STAT3 or NF-κB signaling. We propose that the natural compound 2-MS, as a potent dual inhibitor of STAT3 and NF-κB pathways, is a promising anticancer drug candidate.

[GC-MS analysis and cytotoxic activity of the supercritical extracts from roots and stems of Zanthoxylum nitidum].

The volatile components of roots and stems of Zanthoxylum nitidum were investigated by supercritical fluid carbon dioxide extraction (SFE-CO2) and gas chromatography-mass spectrometry(GC-MS). Thirty-one and fifty-one compounds were identified in the supercritical extracts from roots and stems of Z. nitidum, respectively, and total twenty-seven compounds were the common constituents. Among them, the major constituents in root and stem supercritical extracts were spathulenol (18.49 and 26.18%), n-hexadecanoic acid (14.24% and 12.79%), ar-tumerone (6.95% and 8.88%), oleic acid (8.39% and 5.71%) and hexanoic acid (4.39% and 7.78%). The in-vitro MTT assay showed that the volatile components of roots and stems of Z. nitidum did not exhibited any cytotoxic activity against human cancer Huh-7 and normal IEC-6 cells. These results indicated the same nature of the volatile constituents in the root and stem of Z. nitidum. This investigation may provide further evidence for expansion of medicinal parts of Z. nitidum.

Synthesis of Biotinylated 2-methoxystypandrone and Identification of JAK2 and IKK as its Targets.

BACKGROUND: 2-Methoxystypandrone (2-MS), isolated from the roots of Polygonum cuspidatum, is a potent dual inhibitor of the STAT3 and NF-κB pathways. OBJECTIVE: To investigate the molecular targets and mechanisms of 2-MS. METHOD: A biotin-conjugated 2-MS analog, named 2-MS-Biotin, was designed and synthesized. The effects of 2-MS-Biotin on the STAT3 and NF-κB pathways were examined by Western blotting. The cytotoxicity of 2- MS-Biotin was evaluated using real-time cell analysis system. Proteins directly bound to 2-MS-Biotin were pulled down through streptavidin agarose beads and were detected using Western blotting. RESULTS: 2-MS-Biotin retained the inhibition activities of the parent compound 2-MS on the STAT3 and NF-κB pathways as well as on cancer cell growth. Also, JAK2 and IKK proteins can be effectively pulled down by 2- MS-Biotin. CONCLUSION: Using 2-MS-Biotin as a tool, both JAK2 and IKK were identified as the targets of 2-MS.