Jo Guk Heui, Kim Gi-Young, Kim Wun-Jae, Park Kun Young, Choi Yung Hyun
Department of Biochemistry, Dongeui University College of Korean Medicine, Busan 614-052, Republic of Korea.
Laboratory of Immunobiology, Department of Marine Life Sciences, Jeju National University, Jeju 690-756, Republic of Korea.
Int J Oncol. 2014 Oct;45(4):1497-506. doi: 10.3892/ijo.2014.2536. Epub 2014 Jul 4.
Sulforaphane, a naturally occurring isothiocyanate found in cruciferous vegetables, has received a great deal of attention because of its ability to inhibit cell proliferation and induce apoptosis in cancer cells. In this study, we investigated the anticancer activity of sulforaphane in the T24 human bladder cancer line, and explored its molecular mechanism of action. Our results showed that treatment with sulforaphane inhibited cell viability and induced apoptosis in T24 cells in a concentration-dependent manner. Sulforaphane-induced apoptosis was associated with mitochondria dysfunction, cytochrome c release and Bcl-2/Bax dysregulation. Furthermore, the increased activity of caspase-9 and -3, but not caspase-8, was accompanied by the cleavage of poly ADP-ribose polymerase, indicating the involvement of the mitochondria-mediated intrinsic apoptotic pathway. Concomitant with these changes, sulforaphane triggered reactive oxygen species (ROS) generation, which, along with the blockage of sulforaphane-induced loss of mitochondrial membrane potential and apoptosis, was strongly attenuated by the ROS scavenger N-acetyl-L-cysteine. Furthermore, sulforaphane was observed to activate endoplasmic reticulum (ER) stress and the nuclear factor-E2-related factor-2 (Nrf2) signaling pathway, as demonstrated by the upregulation of ER stress‑related proteins, including glucose-regulated protein 78 and C/EBP-homologous protein, and the accumulation of phosphorylated Nrf2 proteins in the nucleus and induction of heme oxygenase-1 expression, respectively. Taken together, these results demonstrate that sulforaphane has antitumor effects against bladder cancer cells through an ROS-mediated intrinsic apoptotic pathway, and suggest that ER stress and Nrf2 may represent strategic targets for sulforaphane-induced apoptosis.
萝卜硫素是一种存在于十字花科蔬菜中的天然异硫氰酸盐，因其能够抑制癌细胞增殖并诱导癌细胞凋亡而备受关注。在本研究中，我们调查了萝卜硫素对T24人膀胱癌细胞系的抗癌活性，并探讨了其分子作用机制。我们的结果表明，用萝卜硫素处理以浓度依赖性方式抑制T24细胞的活力并诱导其凋亡。萝卜硫素诱导的凋亡与线粒体功能障碍、细胞色素c释放和Bcl-2/Bax失调有关。此外，caspase-9和-3活性增加，但caspase-8活性未增加，同时伴有聚ADP-核糖聚合酶的裂解，表明线粒体介导的内源性凋亡途径参与其中。伴随着这些变化，萝卜硫素引发活性氧（ROS）生成，而ROS清除剂N-乙酰-L-半胱氨酸可强烈减弱ROS生成以及萝卜硫素诱导的线粒体膜电位丧失和凋亡。此外，观察到萝卜硫素激活内质网（ER）应激和核因子E2相关因子2（Nrf2）信号通路，分别表现为ER应激相关蛋白（包括葡萄糖调节蛋白78和C/EBP同源蛋白）上调、细胞核中磷酸化Nrf2蛋白积累以及血红素加氧酶-1表达诱导。综上所述，这些结果表明萝卜硫素通过ROS介导的内源性凋亡途径对膀胱癌细胞具有抗肿瘤作用，并提示ER应激和Nrf2可能是萝卜硫素诱导凋亡的战略靶点。
