大腸直腸癌已躍居世界上癌症死亡率第二名,屬於固體型腫瘤,缺氧常見於此類 腫瘤,並誘發HIF-1α 表現而導致抗藥性及預後較差,因此抑制HIF-1α 被視為新的抗 癌策略。Zebularine (Zeb)是較穩定之DNA methyltransferase (DNMT)抑制劑,可殺死癌 細胞而不影響正常細胞,對小鼠也不具毒性。我們初步結果顯示,Zeb 可抑制人類大 腸癌細胞株HCT116 之HIF-1α表現,代表Zeb 是治療大腸直腸癌之潛力藥物。我們的 初步也證明Zeb對HCT116具毒殺性,對小鼠大腸癌也有療效。細胞自我吞噬(autophagy) 是指細胞在惡劣環境下,經由吞噬細胞內物質產生能量渡過外界壓力的一種保護機 制;也有研究報導指出,藥物會誘導癌細胞產生autophagy,造成細胞過度吞噬其內容 物而死亡,因此,autophagy在癌細胞為保護或是引發毒殺作用,目前仍無定論。缺氧 也會透過HIF-1α 導致autophagy 而促進細胞存活,但嚴重缺氧或無氧狀態則可透過活 化AMPK及unfolded protein response (UPR)造成autophagic cell death。我們初步結果顯 示,除抑制HIF-1α 表現外,Zeb 也可活化AMPK、UPR/ER stress、以及autophagy, 因此我們推測Zeb 可在缺氧狀態下,促進autophagic cell death。3 年內我們將執行4 項 目標: (1) 探討Zeb 在各種癌細胞及活體模式之抗癌作用。(第一年) (2) 研究Zeb 抑制HIF-1α表現之分子機轉。(第一年到第二年) (3) 研究Zeb 誘發autophagy之分子機轉。(第二年到第三年) (4) 探討Zeb 對缺氧導致抗藥性之作用。(第三年)

Project: A - Government Institutionb - Ministry of Science and Technology

Description

Colorectal cancer (CRC) is the second leading cause of cancer-related death in males and females in the world. Hypoxia and accumulation of hypoxia-inducible factor HIF-1α in solid tumor tissues, including CRC, have been reported to associate with resistance to anticancer therapy and poor prognosis. Therefore, targeting HIF-1α might provide clinical benefits to CRC. Zebularine (Zeb), a stable DNA methyltransferase (DNMT) inhibitor, has been shown to preferentially kill cancer cells and exhibits low toxicity in normal cells and mice. Our preliminary results demonstrated that Zeb inhibit HIF-1α expression human colorectal HCT116 cells, suggesting that Zeb might have clinical activity toward CRC. Indeed, Zeb showed anticancer effect in HCT116 cells and in mice colitis-associated colon cancer. Autophagy is a physiological process involved in the turnover of proteins or intracellular organelles. It serves as a temporary survival mechanism during starvation where self-digestion becomes an alternative energy source. It has been recently reported that HIF-1α-dependent autophagy protects cells from anticancer drug-induced apoptosis in hypoxia. However, severe hypoxia or anoxia could induce HIF-1α-independent autophagic cell death through activation of AMPK and unfolded protein response (UPR). In addition to HIF-1α inhibition, Zeb also induced AMPK activation, UPR/ER stress and autophagy in HCT116 cells. Therefore, we hypothesized that Zeb treatment will switch HIF-1α-dependent cytoprotective autophagy to HIF-1α-independent autophagic cell death in hypoxia, which could abrogate hypoxia-induced anticancer drug resistance. In this four-year research project, we plan to incorporate the preliminary results to test the following SPECIFIC AIMS: (1) To investigate the in vitro and in vivo anticancer effect of Zeb toward colorectal cancers. (Year 1) (2) To elucidate the molecular mechanisms of Zeb-mediated HIF-1α inhibition. (Year 1~2) (3) To elucidate the molecular mechanisms of Zeb-induced autophagy. (Year 2~3) (4) To investigate the effect of Zeb on hypoxia-mediated drug resistance. (Year 3)
StatusFinished
Effective start/end date8/1/137/31/14