探討天然植化素臺灣蚤休萃取物Formosanin C致腫瘤細胞鐵依賴性細胞死亡之效果

The effects of the Saponin Formosanin C induced ferroptosis on cancer cells

陳信志(Chen Hsin-Chih)

指導教授 ： 蘇純立

國立臺灣師範大學/教育學院/人類發展與家庭學系/碩士(2018年)

https://doi.org/10.6345/THE.NTNU.DHDFS.030.2018.A06

摘要

癌症是國人的十大死因之首，傳統化療與放療常常引起抗藥性導致預後不佳，因此找出新的替代路徑刻不容緩。鐵依賴性細胞死亡（Ferroptosis）是一種新發現的細胞死亡模式，同時需要不飽和脂肪酸、鐵與氧氣的參與，藉由使體內抗氧化酶GPX4產量減少或活性喪失進而引起脂質過氧化，傷害大分子物質引起細胞死亡，研究指出Ferroptosis具有潛在改善抗藥性的能力。Formosanin C（FC）是從台灣蚤休中分離的有效化合物，對腫瘤非常敏感，已知腫瘤細胞具有堆積鐵的能力，本研究為確定FC是否可以誘導大腸直腸癌與乳癌細胞株產生Ferroptosis，並探討FC誘導的Ferroptosis之相關路徑與分子調控。實驗發現在大腸直腸癌中FC可以誘發Ferroptosis透過Lipid ROS的產生，且KRAS與p53為FC誘導的Ferroptosis的正向調控子。在乳癌中，FC也可以產生Ferroptosis，透過抑制Nrf2-Keap1 pathway進而耗竭GSH與GPX4，並增加Lipid ROS的產生，另外會增加細胞內游離鐵池。透過上調進鐵蛋白與下調出鐵蛋白的表現，其中轉移與侵襲能力較強的三陰性乳癌細胞MDA-MB-231產生Ferroptosis的能力比較良性的MCF-7佳。此外FC也可以誘導乳癌細胞株產生Autophagy與Ferritinophagy，不過Autophagy與Ferroptosis的關係尚未釐清。綜上所述，天然化合物FC可以誘導大腸直腸癌與乳癌細胞株產生Ferroptosis，且能靶向預後較差的KRAS突變大腸直腸癌與三陰性乳癌，將來在臨床上可以透過癌症基因篩檢，找出KRAS陽性與p53陽性的大腸直腸癌腫瘤病患與應用轉移與侵襲能力強的惡性乳癌堆積鐵卓越的特性，藉由FC誘導Ferroptosis改善腫瘤病患預後不佳的問題，提升醫療品質。

關鍵字

台灣蚤休 ； 鐵依賴性死亡 ； 鐵蛋白自噬 ； 藥物阻抗

並列摘要

Formosanin C (FC), a phytosteroid sapogenin isolated from the plants. Ferroptosis, a novel form of regulated cell death, is characterized by a production of reactive oxygen species (ROS) from an accumulated iron and lipid peroxidation. Iron accumulati on has been reported in colorectal and breast cancer cells, and it is positive correlated with the degree of tumor malignancy. Therefore, ferroptosis may selectively eliminate cancer cells, and activation of this alternative cell death pathway may overcome the drug resistance associated with existing chemotherapeutics. Using ferroptosis specific inhibitor Ferrostatin-1(Fer-1) to screen various anticancer drugs and phytochemicals reveals that FC significantly inhibited the population growth of human colorectal and breast cancer cells via ferroptosis. Flow cytometric analysis after DCFHDA and C11-BODIPY581/591 staining further shows that FC increased both cytosolic and lipid ROS, respectively. These phenomena were paralleled by a decrease in GPX4 and GSH and related to Nrf2-Keap pathway. FC also increased labile iron pool via upregulation of iron input protein and downregulation of iron output protein. Comparison of four colorectal cancer cell lines, KRAS mutant HT-29 was more sensitive to FC-induced ferroptosis than Parental HT-29 and p53 KD HCT 116 was less sensitive to FC-induced ferroptosis than p53 wild type HCT 116. The results show that KRAS and p53 play a positive regulator in FC-induced ferroptosis of colorectal cancer cell lines. Compared two breast cancer cell lines, MDA-MB-231 acquired a stronger dependence on GPX4 and system Xc- than MCF-7. In summary, ferroptosis induction in colorectal and breast cancer cell lines by FC was characterized by an induced lipid peroxidation, iron accumulation and depletion of GSH and GPX4. FC also induced autophagy in two breast cnacer lines, by which ferroptosis was upregulated via degradation of nuclear receptor coactivator 4 to be responsible for ferritin degradation by ferritinophagy.

並列關鍵字

Formosanin C ； Ferroptosis ； Ferritinophagy ； Drug resistance

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