Maurya Akhilendra Kumar, Vinayak Manjula
Biochemistry & Molecular Biology Laboratory, Centre of Advanced Study in Zoology, Banaras Hindu University, Varanasi, 221005, India,
Mol Biol Rep. 2015 Sep;42(9):1419-29. doi: 10.1007/s11033-015-3921-7. Epub 2015 Aug 27.
Protein kinase C (PKC) is a key regulator of cell growth and differentiation in mammalian cells and hyperactivation of PKC is believed to play an important role in tumor progression. PKC is downstream to signaling protein of phosphatidylinositol 3-Kinase (PI3K), a known up-regulator of cell proliferation and survival. Accumulation of reactive oxygen species (ROS) triggers oxidative stress in the tumor microenvironment, leading to the hyperactivation of various oxidative stress-stimulated signaling molecules. Quercetin (QUE) is a naturally occurring dietary flavonoid having antioxidant properties. QUE is reported to show antitumor activity both in vitro and in vivo; however, the molecular mechanism is yet to be thoroughly explored. HepG2 cells display cellular functions similar to the normal hepatocytes with high degree of morphological and functional differentiation, therefore HepG2 cell line is chosen as the suitable model for drug targeting. Present study is aimed to establish the signaling pathway involved in the anticarcinogenic action of QUE in HepG2 cell line. HepG2 cells were treated with different doses of QUE. Protein level and gene expression were analysed by Western blotting and RT-PCR, respectively. PKC activity was measured by non-radioactive-tagged phosphorylation. Results showed downregulation of expression of PI3K, PKC, COX-2 and ROS caused by QUE. Additionally, QUE enhanced the expression of p53 and BAX in HepG2 cells. Overall, results of the current study suggested that QUE elicited anticarcinogenic action by upregulation of p53 and BAX in HepG2 cells via downregulation of ROS, PKC, PI3K and COX-2, confirming our earlier report on the animal model.
蛋白激酶C（PKC）是哺乳动物细胞中细胞生长和分化的关键调节因子，PKC的过度激活被认为在肿瘤进展中起重要作用。PKC位于磷脂酰肌醇3激酶（PI3K）信号蛋白的下游，PI3K是已知的细胞增殖和存活的上调因子。活性氧（ROS）的积累引发肿瘤微环境中的氧化应激，导致各种氧化应激刺激的信号分子过度激活。槲皮素（QUE）是一种具有抗氧化特性的天然膳食类黄酮。据报道，QUE在体外和体内均显示出抗肿瘤活性；然而，其分子机制尚未得到充分探索。HepG2细胞具有与正常肝细胞相似的细胞功能，具有高度的形态和功能分化，因此选择HepG2细胞系作为合适的药物靶向模型。本研究旨在建立QUE在HepG2细胞系中抗癌作用所涉及的信号通路。用不同剂量的QUE处理HepG2细胞。分别通过蛋白质印迹法和RT-PCR分析蛋白质水平和基因表达。通过非放射性标记的磷酸化测量PKC活性。结果显示QUE导致PI3K、PKC、COX-2和ROS的表达下调。此外，QUE增强了HepG2细胞中p53和BAX的表达。总体而言，本研究结果表明，QUE通过下调ROS、PKC、PI3K和COX-2上调HepG2细胞中的p53和BAX，从而引发抗癌作用，证实了我们之前在动物模型上的报道。
