xanthatin and Liver-Neoplasms

Hepatocellular carcinoma (HCC) has high incidence and mortality in patients with chronic liver diseases worldwide. However, there are limited chemotherapeutic agents for HCC in clinic. Xanthatin, a natural sesquiterpene lactone, has significant antitumor activity against a variety of cancers, but little is known about its effects on HCC and the underlying mechanism. Here, we evaluated the antitumor effects of xanthatin on human hepatoma cells. We found that xanthatin caused morphological changes and reduced cell viability in three HCC cell lines in concentration- and time-dependent manners. Xanthatin at 10 μM significantly arrested cell cycle at the G2/M checkpoint, and at 40 μM significantly arrested cell cycle at the S phase in hepatoma cells. Additionally, xanthatin induced apoptosis associated with activation of caspase-3 in hepatoma cells, but did not apparently induce apoptosis in human normal LO2 hepatocytes. We also demonstrated that the three primary signaling pathways of unfolded protein response (UPR) were activated by xanthatin to different extents. Notably, the PERK/eIF-2α/ATF4 axis was most significantly activated by xanthatin. More importantly, both xanthatin and tunicamycin, an endoplasmic reticulum stress (ERS) inducing compound, increased the levels of CHOP and cleaved-caspase-3 in HepG2 cells, but their effects were significantly abolished by siRNA-mediated knockdown of CHOP. Further experiments validated that xanthatin more potently activated ATF4 by promoting its nuclear translocation in hepatoma cells. Taken together, we discovered that xanthatin induced apoptosis in human hepatoma cells by activating ERS. Our current data revealed a novel mechanism for xanthatin as a promising anti-tumor candidate for HCC therapy.

Topics: Activating Transcription Factor 4; Antineoplastic Agents; Apoptosis; Carcinoma, Hepatocellular; Cell Line; eIF-2 Kinase; Endoplasmic Reticulum Stress; Eukaryotic Initiation Factor-2; Furans; Hepatocytes; Humans; Liver Neoplasms; Transcription Factor CHOP

Aberrant activation of the signal transducer and activator of transcription 3 (STAT3) and the nuclear factor-κB (NF-κB) signalling pathways is associated with the development of cancer and inflammatory diseases. JAKs and IKKs are the key regulators in the STAT3 and NF-κB signalling respectively. Therefore, the two families of kinases have been the major targets for developing drugs to regulate the two signalling pathways. Here, we report a natural compound xanthatin from the traditional Chinese medicinal herb Xanthium L. as a potent inhibitor of both STAT3 and NF-κB signalling pathways. Our data demonstrated that xanthatin was a covalent inhibitor and its activities depended on its α-methylene-γ-butyrolactone group. It preferentially interacted with the Cys243 of JAK2 and the Cys412 and Cys464 of IKKβ to inactivate their activities. In doing so, xanthatin preferentially inhibited the growth of cancer cell lines that have constitutively activated STAT3 and p65. These data suggest that xanthatin may be a promising anticancer and anti-inflammation drug candidate.

Topics: Carcinoma, Hepatocellular; Furans; Humans; I-kappa B Kinase; Inflammation; Janus Kinases; Liver Neoplasms; NF-kappa B; Phosphorylation; Signal Transduction; STAT3 Transcription Factor; Tumor Cells, Cultured

1β-hydroxyl-5α-chloro-8-epi-xanthatin (XTT), a sesquiterpene lactone isolated from Xanthium sibiricum, possessed potent cytotoxicity on cancer cells in vitro. The objective of this study was to investigate the anti-tumor effect and underlying mechanisms of XTT on human hepatocellular carcinoma (HCC). Firstly, XTT inhibited the cell growth and induced apoptosis in human HCC cells, which was associated with the induction of Bax and cleaved-caspase-3, inhibition of Bcl-2 and survivin expression. Importantly, XTT induced the generation of reactive oxygen species (ROS) and malondialdehyde (MDA), and depletion of glutathione (GSH) in HCC cells through covalently modification of GSH. Furthermore, XTT caused obvious activation of extracellular regulated protein kinase (ERK) and p38 mitogen-activated protein kinase (p38 MAPK) and inactivation of Janus kinase 2/signal transducer and activator of transcription 3 (JAK2/STAT3) in HCC cells. ROS scavenger N-acetyl cysteine abrogated the effects of XTT on ERK/p38 MAPK activation and JAK2/STAT3 inhibition, and rescued HCC cells from XTT-induced apoptosis. Additionally, inhibitors of ERK/p38 MAPKs or activator of JAK2/STAT3 partially abolished XTT-mediated effect. In summary, XTT inhibited cell growth and induced apoptosis in HCC cells through ROS-mediated ERK/p38 MAPK activation and JAK2/STAT3 inhibition by GSH depletion. These findings also show the therapeutic potential of XTT in HCC.

Topics: Acetylcysteine; Apoptosis; Carcinoma, Hepatocellular; Cell Line, Tumor; Cell Proliferation; Enzyme Activation; Extracellular Signal-Regulated MAP Kinases; Furans; Glutathione; Humans; Janus Kinase 2; Liver Neoplasms; Malondialdehyde; Oxidative Stress; p38 Mitogen-Activated Protein Kinases; Protein Kinase Inhibitors; Reactive Oxygen Species; STAT3 Transcription Factor