6-shogaol 和dehydrocostuslactone對人類肺癌細胞增生抑制作用和細胞程式死亡機制之探討

Cancer has been the leading cause of mortality in Taiwan since 1982. According to the statistics from Department of Health, lung cancer has been the leading cause of cancer related deaths in Taiwan in the recent decade. And the ratio of lung cancer in the causes of cancer related deaths was noted to increase year by year. The two major forms of lung cancer are non–small-cell lung cancer (about 85% of all lung cancers) and small-cell lung cancer (about 15%). The treatment of choice for early stage non-small lung cancer is surgery, followed by adjuvant chemotherapy or radiotherapy. Unfortunately, the risk of metastasis or recurrence after initial treatment is high, and these patients usually develop resistance to further treatment. For advanced/metastatic non-small lung cancer patients, they could only receive palliative chemotherapy or radiotherapy. The 5-year survival rate of non-small lung cancer patients is only 15%. Despite advances in early detection, non–small-cell lung cancer is often diagnosed at advanced stage and has poor prognosis. Therefore, development of a more effective therapy is urgent. There are a lot of clinically useful and important anti-cancer agents purified from plants. The majority of these anti-cancer agents were pure compound extracted from plant or its derivatives. Our laboratory focuses on pure compound from traditional Chinese herbal medicines, we try to study the active mechanism of their anti-cancer activity. And this allows a better appreciation of Chinese herbal medicines in the modern era and also a better understanding of its potential for therapy. From our preliminary screening, we observed that 6-shogaol from ginger and dehydrocostuslactone (DHE) from Saussurea lappa inhibited A549 human lung adenocarcinoma cell line and NCI-H460 human lung large cell carcinoma cell line. The first part of this study investigated the anticancer effect of 6-shogaol in A549 human non-small cell lung cancer cells. 6-shogaol inhibited cell proliferation mostly by inducing autophagic cell death. Pretreatment of cells with 3-methyladenine (3-MA), an autophagy inhibitor, suppressed 6-shogaol mediated antiproliferation activity, suggesting that induction of autophagy by 6-shogaol is conducive to cell death. We also found that 6-shogaol inhibited survival signaling through the AKT/mTOR signaling pathway by blocking the activation of AKT and downstream targets, including the mammalian target of rapamycin (mTOR), forkhead transcription factors (FKHR) and glycogen synthase kinase-3β (GSK-3β). Phosphorylation of both of mTOR’s downstream targets, p70 ribosomal protein S6 kinase (p70S6 kinase) and 4E-BP1, was also diminished. Overexpression of AKT by AKT cDNA transfection decreased 6-shogaol mediated autophagic cell death, supporting the hypothesis that inhibition of AKT is beneficial to autophagy. Moreover, reduction of AKT expression by siRNA potentiated 6-shogaol’s effect, also supporting the hypothesis that inhibition of AKT is beneficial to autophagy. Taken together, these findings suggest that 6-shogaol may be a promising chemopreventive agent against human non-small cell lung cancer. Project 2: This study investigates the anticancer effect of dehydrocostuslactone (DHE), a medicinal plant-derived sesquiterpene lactone, on human non-small cell lung cancer cell lines A549, NCI-H460 and NCI-H520. Our results showed that DHE inhibited the proliferation of A549, NCI-H460 and NCI-H520 cells. DHE induced apoptosis in both A549 and NCI-H460 cells. DHE triggered endoplasmic reticulum (ER) stress, as indicated by changes in cytosol-calcium levels, PKR-like ER kinase (PERK) phosphorylation, inositol requiring protein 1 (IRE1) and CHOP/GADD153 upregulation, X-box transcription factor-1 (XBP-1) mRNA splicing, and caspase-4 activation. The release of calcium triggered the production of ROS, which further enhances calcium overloading and subsequently activates p38, JNK and ERK1/2. Both IRE1 miRNA transfection and BAPTA-AM pretreatment inhibit DHE-mediated apoptosis, supporting the hypothesis that DHE induces cell death through ER stress. Importantly, animal studies showed 50% reduction in tumor size after 28 days of treatment with DHE. This study demonstrates that DHE may be a novel anticancer agent for the treatment of non-small cell lung cancer.