Chloroquine enhances the cytotoxicity of topotecan by inhibiting autophagy in lung cancer cells / 癌症

Although the anti-malaria drug chloroquine (CQ) has been shown to enhance chemotherapy and radiation sensitivity in clinical trials, the potential mechanisms underlying this enhancement are still unclear. Here, we examined the relevant mechanisms by which the multipotent CQ enhanced the cytotoxicity of topotecan (TPT). The lung cancer cell line A549 was treated with TPT alone or TPT combined with CQ at non-cytotoxic concentrations. Cell viability was assessed using the MTT assay. The percentage of apoptotic cells and the presence of a side population of cells were both determined by flow cytometry. Autophagy and the expression of Bcl-2 family proteins were examined by Western blotting. The accumulation of YFP-LC3 dots and the formation of acidic vesicular organelles were examined by confocal microscopy. CQ sensitized A549 cells to TPT and enhanced TPT-induced apoptosis in a Bcl-2 family protein-independent fashion. CQ inhibited TPT-induced autophagy, which modified the cytotoxicity of TPT. However, CQ failed to modify the transfer of TPT across the cytoplasmic membrane and did not increase lysosomal permeability. This study showed that CQ at non-cytotoxic concentrations potentiated the cytotoxicity of TPT by interfering with autophagy, implying that CQ has significant potential as a chemotherapeutic enhancer.

A novel sesquiterpene Hirsutanol A induces autophagical cell death in human hepatocellular carcinoma cells by increasing reactive oxygen species / 癌症

<p><b>BACKGROUND AND OBJECTIVE</b>Hirsutanol A is a novel sesquiterpene compound purified from fungus chondrostereum sp in Sarcophyton tortuosum. Its pharmacologic effect has not been reported yet. This study aimed to investigate cytotoxic effect of Hirsutanol A on hepatocellular carcinoma (HCC) cells and its mechanism.</p><p><b>METHODS</b>Hep3B cells were treated with different concentrations of Hirsutanol A. Cell proliferation was detected by MTT assay. The protein expression of LC3 was determined by Western blot. The generation of reactive oxygen species (ROS) was monitored by flow cytometry.</p><p><b>RESULTS</b>Hirsutanol A significantly inhibited proliferation of Hep3B cells with 50% inhibition concentrations (IC50) of 14.54, 6.71, and 3.59 micromol/L when exposed to Hirsutanol A for 24, 48, and 72 h, respectively. Incubation of Hep3B cells with Hirsutanol A markedly increased the level of ROS and the autophagy marker MAP-LC3 conversion from type I to type II. Pre-incubation with an antioxidant N-acetyl cystein (NAC) decreased the level of ROS, and reduced MAP-LC3 I-II conversion, and suppressed cell death. Blocking autophagy with a specific autophagy inhibitor 3-methyladenine (3-MA), the cytotoxic effect of this compound was attenuated.</p><p><b>CONCLUSION</b>Hirsutanol A has potent cytotoxic effect, and can induce autophagic cell death via increasing ROS production.</p>