植化素Withaferin A 引發人類非小細胞肺癌鐵依賴型細胞死亡的影響

Abstract

鐵依賴型細胞死亡(ferroptosis)為一調節性細胞死亡形式，其導致細胞死亡的特徵為：還原活化態的鐵存在、氧化含多元不飽和脂肪酸的磷脂質及脂質過氧化修復能力缺失，被認為是對抗惡性癌細胞的新契機。肺癌是全球死亡人數最多的癌症，預後不佳且死亡率逐年攀升，除傳統治療方法外，臨床也針對EGFR突變型(mutant-type)的肺癌細胞株開發標靶藥物，但對於無突變的EGFR 原生型(wild-type)肺癌細胞效果不彰。本研究透過基因分析發現肺癌細胞內鐵相關基因FTH1表現量不僅與ferroptosis發生有關，亦影響南非醉茄之萃取物Withaferin A (WA)作用於肺癌細胞的活性。經實驗證實儲鐵蛋白FTH1表現量較低的惡性非小細胞肺癌細胞CL1-5對ferroptosis inducer敏感性高，且WA經由提高進鐵蛋白TFRC提升細胞內鐵含量、增加生成細胞lipid ROS與抑制細胞抗氧化能力，並透過自噬體包裹、降解FTH1，促使容易產生氧化還原作用的游離鐵釋出，誘導CL1-5細胞發生ferroptosis。另外，WA合併肺癌臨床化療藥物能藉由引發ferroptosis造成肺癌細胞死亡。綜合以上結果，透過天然植化素WA誘導癌細胞產生ferroptosis，以改善EGFR 原生型之非小細胞肺癌細胞對化療藥物及標靶藥物療效有限的治療困境，是對抗惡性肺癌腫瘤相當具有潛力的新策略。

Ferroptosis is a regulated cell death characterized by the availability of redox active iron, oxidation of polyunsaturated fatty acid containing phospholipids and loss of lipid peroxide repair capacity. It is considered as a new hope for fighting malignant cancer cells. Lung cancer has been the leading cause of cancer death worldwide. The prognosis of lung cancer is poor and the mortality rate is increasing year by year. In addition to traditional treatment methods, targeted therapy has also been developed for EGFR mutant lung cancer cell lines, but the efficacy of EGFR wild-type lung cancer cells is limited. In the present study, database analysis results show that iron-related gene, FTH1 expression in lung cancer was not only associated with ferroptosis, but also the drug activity of withaferin A (WA), a kind of phytochemical extracted from Ashwagandha. CL1-5, a malignant non-small cell lung cancer (NSCLC) cell line, with a lower protein expression of FTH1 was sensitive to ferroptosis inducer, and WA-induced ferroptosis in CL1-5 proceeded through elevating the intracellular iron level by upregulating the protein expression of TFRC, increasing the production of lipid ROS. The antioxidant capacity was also inhibited. Besides, WA caused the degradation of FTH1 by formation of autophagosomes to release free iron which triggers ferroptosis, and the cell death effect of the combination of WA and lung cancer chemotherapeutic drugs on NSCLC is related to WA-induced ferroptosis. Overall, our results suggest that WA may increase the chance to fight against EGFR wild-type NSCLC and improve the quality of medical treatment.