Jia Huina, Ye Juan, You Jing, Shi Xiaoyan, Kang Wenyi, Wang Tianxiao
Institute of Traditional Chinese Medicine, College of Pharmacy, Henan University, Kaifeng, Henan 475004, P.R. China.
Oncol Rep. 2017 May;37(5):3001-3009. doi: 10.3892/or.2017.5513. Epub 2017 Mar 17.
Hydrogen sulfide (H2S), the third gasotransmitter, plays important roles in cancer biological processes. As endogenous H2S exerts pro-cancer functions, inhibition of its production in cancer cells may provide a new cancer treatment strategy and be achieved via regulation of the function of cystathionine β-synthase (CBS), one of the main metabolic enzymes synthesizing H2S. This enzyme plays important roles in the development and progression of colon and ovarian cancer, primarily regulating mitochondrial bioenergetics and accelerating cell cycle progression. In the present study, we firstly investigated the role of the CBS/H2S system in human hepatoma cells, and then the inhibitory effect of a quinolone-indolone conjugate QIC2 on this system. When CBS was overexpressed in human hepatoma HepG2 and SMMC-7721 cells, inhibition of endogenous CBS/H2S significantly reduced their viability and growth rate, as well as the proliferation of SMMC-7721 cells. Meanwhile, CBS knockdown caused multiple effects, including apoptosis of SMMC-7721 cells, an increase in the Bcl-2-associated X protein (Bax)/B cell lymphoma/leukemia (Bcl-2) ratio, activation of caspase-3 and polyADP-ribose polymerase (PARP), when compared with the scramble siRNA (Sc siRNA)-transfected groups. Heme oxygenase-1 (HO-1; a microsomal enzyme) expression was significantly decreased while the reactive oxygen species (ROS) level was increased in the CBS siRNA-transfected SMMC-7721 cells. QIC2 significantly reduced SMMC-7721 cell viability in a dose-dependent manner and showed a lower toxicity in human normal liver HL-7702 cells relative to the positive controls sunitinib and doxorubicin (DOX). The compound also inhibited cell proliferation and induced cell apoptosis in SMMC-7721 cells. Further analysis indicated that QIC2 downregulated the CBS/H2S system, decreased both HO-1 protein and glutathione (GSH) levels while increased the ROS level and activated the caspase-3 cascade. Collectively, our results demonstrated that the CBS/H2S system plays important roles in human hepatoma cells and QIC2 significantly inhibited cell growth via downregulation of the system.
硫化氢（H₂S）作为第三种气体信号分子，在癌症生物学过程中发挥着重要作用。由于内源性H₂S具有促癌功能，抑制其在癌细胞中的产生可能提供一种新的癌症治疗策略，可通过调节胱硫醚β-合酶（CBS）的功能来实现，CBS是合成H₂S的主要代谢酶之一。该酶在结肠癌和卵巢癌的发生发展中起重要作用，主要调节线粒体生物能量代谢并加速细胞周期进程。在本研究中，我们首先研究了CBS/H₂S系统在人肝癌细胞中的作用，然后研究了喹诺酮-吲哚酮共轭物QIC2对该系统的抑制作用。当CBS在人肝癌HepG2和SMMC-7721细胞中过表达时，抑制内源性CBS/H₂S可显著降低其活力和生长速率，以及SMMC-7721细胞的增殖。同时，与转染乱序小干扰RNA（Sc siRNA）的组相比，CBS基因敲低产生了多种效应，包括SMMC-7721细胞凋亡、Bcl-2相关X蛋白（Bax）/B细胞淋巴瘤/白血病-2（Bcl-2）比值增加、半胱天冬酶-3（caspase-3）和聚ADP核糖聚合酶（PARP）激活。在转染CBS小干扰RNA的SMMC-7721细胞中，血红素加氧酶-1（HO-1；一种微粒体酶）表达显著降低，而活性氧（ROS）水平升高。QIC2以剂量依赖性方式显著降低SMMC-7721细胞活力，相对于阳性对照舒尼替尼和阿霉素（DOX），其对人正常肝HL-7702细胞的毒性较低。该化合物还抑制SMMC-7721细胞的增殖并诱导其凋亡。进一步分析表明，QIC2下调CBS/H₂S系统，降低HO-1蛋白和谷胱甘肽（GSH）水平，同时升高ROS水平并激活caspase-3级联反应。总体而言，我们的结果表明CBS/H₂S系统在人肝癌细胞中起重要作用，QIC2通过下调该系统显著抑制细胞生长。
