Xanthatin, a natural sesquiterpene lactone, has significant antitumor activity against a variety of cancer cells, yet little is known about its anticancer mechanism. In this study, we demonstrated that xanthatin had obvious dose-/time-dependent cytotoxicity against the human non-small-cell lung cancer (NSCLC) cell line A549. Flow cytometry analysis showed xanthatin induced cell cycle arrest at G2/M phase. Xanthatin also had pro-apoptotic effects on A549 cells as evidenced by Hoechst 33258 staining and annexin V-FITC staining. Mechanistic data revealed that xanthatin downregulated Chk1, Chk2, and phosphorylation of CDC2, which contributed to the cell cycle arrest. Xathatin also increased total p53 protein levels, decreased Bcl-2/Bax ratio and expression of the downstream factors procaspase-9 and procaspase-3, which triggered the intrinsic apoptosis pathway. Furthermore, xanthatin blocked phosphorylation of NF-κB (p65) and IκBα, which might also contribute to its pro-apoptotic effects on A549 cells. Xanthatin also inhibited TNFα induced NF-κB (p65) translocation. We conclude that xanthatin displays significant antitumor effects through cell cycle arrest and apoptosis induction in A549 cells. These effects were associated with intrinsic apoptosis pathway and disrupted NF-κB signaling. These results suggested that xanthatin may have therapeutic potential against NSCLC.

Aim: To investigate whether luteolin, a highly prevalent flavonoid, reverses the effects of epithelial-mesenchymal transition (EMT) in vitro and in vivo and to determine the mechanisms underlying this reversal. Methods: Murine malignant melanoma B16F10 cells were exposed to 1% O 2 for 24 h. Cellular mobility and adhesion were assessed using Boyden chamber transwell assay and cell adhesion assay, respectively. EMT-related proteins, such as E-cadherin and N-cadherin, were examined using Western blotting. Female C57BL/6 mice (6 to 8 weeks old) were injected with B16F10 cells (1×10 6 cells in 0.2 mL per mouse) via the lateral tail vein. The mice were treated with luteolin (10 or 20 mg/kg, ip) daily for 23 d. On the 23rd day after tumor injection, the mice were sacrificed, and the lungs were collected, and metastatic foci in the lung surfaces were photographed. Tissue sections were analyzed with immunohistochemistry and HE staining. Results: Hypoxia changed the morphology of B16F10 cells in vitro from the cobblestone-like to mesenchymal-like strips, which was accompanied by increased cellular adhesion and invasion. Luteolin (5−50 µmol/L) suppressed the hypoxia-induced changes in the cells in a dose-dependent manner. Hypoxia significantly decreased the expression of E-cadherin while increased the expression of N-cadherin in the cells (indicating the occurrence of EMT-like transformation), which was reversed by luteolin (5 μmol/L). In B16F10 cells, luteolin up-regulated E-cadherin at least partly via inhibiting the β3 integrin/FAK signal pathway. In experimental metastasis model mice, treatment with luteolin (10 or 20 mg/kg) reduced metastatic colonization in the lungs by 50%. Furthermore, the treatment increased the expression of E-cadherin while reduced the expression of vimentin and β3 integrin in the tumor tissues. Conclusion: Luteolin inhibits the hypoxia-induced EMT in malignant melanoma cells both in vitro and in vivo via the regulation of β3 integrin, suggesting that luteolin may be applied as a potential anticancer chemopreventative and chemotherapeutic agent.

Xanthatin, a natural bioactive compound of sesquiterpene lactones, was isolated and purified from air-dried aerial part of Xanthium sibiricum Patrin ex Widder. In the present study, we demonstrated the significant antiproliferative and proapoptotic effects of xanthatin on human gastric carcinoma MKN-45 cells. MTS assay showed that xanthatin produced obvious cytotoxicity in MKN-45 cells with IC50 values of 18.6, 9.3, and 3.9 µM for 12, 24, and 48 h, respectively. Results of flow cytometry analysis indicated that the antiproliferative activity induced by xanthatin might be executed via G2/M cell cycle arrest and proapoptosis in MKN-45 cells. Western blot analysis elucidated that: a) xanthatin downregulated expression of Chk1 and Chk2 and phosphorylation of CDC2, which are known as key G2/M transition regulators; b) xanthatin increased p53 activation, decreased the bcl-2/bax ratio and the levels of downstream procaspase-9 and procaspase-3, which are key regulators in the intrinsic apoptosis pathway; c) xanthatin blocked phosphorylation of NF-κB (p65 subunit) and of IκBα, which might contribute to its proapoptotic effects on MKN-45 cells. In conclusion, our results suggest that xanthatin may have therapeutic potential against human gastric carcinoma.

Abstract. Hypoxia-induced epithelial mesenchymal transition (EMT) is an essential step in cancer metastasis. Luteolin, a flavonoid that is widely distributed in plants, is a novel anticancer agent. However, the mechanism underlying its anticancer effects remains undefined. In this study, for the first time, we demonstrate that luteolin inhibits hypoxia-induced EMT in human non-small cell lung cancer cells in culture, which is demonstrated by the fact that hypoxia-induced EMT reduced the expression of E-cadherin and other epithelial markers and increased the expression of N-cadherin, vimentin and other mesenchymal markers; these effects were markedly attenuated by luteolin. In addition, luteolin also inhibited hypoxia-induced proliferation, motility and adhesion in the cells. Furthermore, we reveal that luteolin inhibits the expression of integrin β1 and focal adhesion kinase (FAK).Since integrin β1 and FAK signaling are closely related to EMT formation, these results suggest that luteolin inhibits hypoxia-induced EMT, at least in part, by inhibiting the expression of integrin β1 and FAK.

Caulis Spatholobi, Flos Carthami and Rhizoma Curcumae have potent anti-platelet properties, and their inhibitory actions are mediated via different mechanisms. Caulis Spatholobi inhibited ADP-induced platelet aggregation but not by thrombin, indicating that its mechanism of action might be independent of the thromboxane pathway. The effect of Caulis Spatholobi and Flos Carthami were associated with suppressing the expression of P-selectin.