Lim Su-Wen, Loh Hwei-San, Ting Kang-Nee, Bradshaw Tracey D, Zeenathul Nazariah A
School of Biosciences, Faculty of Science, University of Nottingham Malaysia Campus, 43500 Semenyih, Malaysia.
BMC Complement Altern Med. 2014 Dec 6;14:469. doi: 10.1186/1472-6882-14-469.
Tocotrienols, especially the gamma isomer was discovered to possess cytotoxic effects associated with the induction of apoptosis in numerous cancers. Individual tocotrienol isomers are believed to induce dissimilar apoptotic mechanisms in different cancer types. This study was aimed to compare the cytotoxic potency of alpha-, gamma- and delta-tocotrienols, and to explore their resultant apoptotic mechanisms in human lung adenocarcinoma A549 and glioblastoma U87MG cells which are scarcely researched.
The cytotoxic effects of alpha-, gamma- and delta-tocotrienols in both A549 and U87MG cancer cells were first determined at the cell viability and morphological aspects. DNA damage types were then identified by comet assay and flow cytometric study was carried out to support the incidence of apoptosis. The involvements of caspase-8, Bid, Bax and mitochondrial membrane permeability (MMP) in the execution of apoptosis were further expounded.
All tocotrienols inhibited the growth of A549 and U87MG cancer cells in a concentration- and time-dependent manner. These treated cancer cells demonstrated some hallmarks of apoptotic morphologies, apoptosis was further confirmed by cell accumulation at the pre-G1 stage. All tocotrienols induced only double strand DNA breaks (DSBs) and no single strand DNA breaks (SSBs) in both treated cancer cells. Activation of caspase-8 leading to increased levels of Bid and Bax as well as cytochrome c release attributed by the disruption of mitochondrial membrane permeability in both A549 and U87MG cells were evident.
This study has shown that delta-tocotrienol, in all experimental approaches, possessed a higher efficacy (shorter induction period) and effectiveness (higher induction rate) in the execution of apoptosis in both A549 and U87MG cancer cells as compared to alpha- and gamma-tocotrienols. Tocotrienols in particular the delta isomer can be an alternative chemotherapeutic agent for treating lung and brain cancers.
生育三烯酚，尤其是γ异构体，被发现具有细胞毒性作用，与多种癌症中细胞凋亡的诱导有关。据信，单个生育三烯酚异构体在不同癌症类型中诱导不同的凋亡机制。本研究旨在比较α-、γ-和δ-生育三烯酚的细胞毒性效力，并探讨它们在研究较少的人肺腺癌A549和胶质母细胞瘤U87MG细胞中产生的凋亡机制。
首先从细胞活力和形态方面确定α-、γ-和δ-生育三烯酚对A549和U87MG癌细胞的细胞毒性作用。然后通过彗星试验鉴定DNA损伤类型，并进行流式细胞术研究以支持细胞凋亡的发生。进一步阐述了半胱天冬酶-8、Bid、Bax和线粒体膜通透性（MMP）在凋亡执行中的作用。
所有生育三烯酚均以浓度和时间依赖性方式抑制A549和U87MG癌细胞的生长。这些经处理的癌细胞表现出一些凋亡形态的特征，细胞在G1期前的积累进一步证实了细胞凋亡。所有生育三烯酚在两种经处理的癌细胞中仅诱导双链DNA断裂（DSB），未诱导单链DNA断裂（SSB）。在A549和U87MG细胞中，半胱天冬酶-8的激活导致Bid和Bax水平升高以及细胞色素c释放，这归因于线粒体膜通透性的破坏，这一点很明显。
本研究表明，在所有实验方法中，与α-和γ-生育三烯酚相比，δ-生育三烯酚在A549和U87MG癌细胞凋亡执行中具有更高的效力（诱导期更短）和有效性（诱导率更高）。生育三烯酚，特别是δ异构体，可作为治疗肺癌和脑癌的替代化疗药物。
