The Prevention Program, Barbara Ann Karmanos Cancer Institute, and Department of Pathology, School of Medicine, Wayne State University, Detroit, MI 48201, USA.
Key Laboratory of Marine Chemistry Engineering and Technology, Ministry of Education, College of Chemistry and Chemical Engineering, Ocean University of China.
Int J Oncol. 2010 Jul;37(1):81-87. doi: 10.3892/ijo_00000655.
The metal ion copper is a cofactor essential for maintaining normal biological and physical functions in human beings. High copper levels have been found in variety of tumor tissues and are involved in tumor angiogenesis processes. The ubiquitin-proteasome system plays an important role in cell growth and apoptosis and has been shown as a novel target for cancer therapy. We previously reported that some organic copper complexes can inhibit the proteasomal chymotrypsin-like activity and induce apoptosis in human cancer cells and xenograft models. In the current study, we investigated the effect of oxidation status of copper, Cu(I) or Cu(II), on inhibition of proteasome activity, induction of apoptosis, and induction of reactive oxygen species (ROS) in human cancer cells. We report four major findings here: i) both Cu(I) and Cu(II) could inhibit the chymotrypsin-like activity of purified 20S proteasome, but Cu(I) was more potent than Cu(II), ii) purified 20S proteasome protein was able to reduce Cu(II) to Cu(I), suggesting that Cu(I) is the oxidation status of copper that directly reacts with the proteasome, iii) when complexed with the copper ligand neocuproine, Cu(I) showed higher ability to induce ROS production in cancer cells, compared with Cu(II), iv) addition of a ROS scavenger in the cancer cell culture-blocked copper-induced ROS generation, but did not overcome copper-mediated proteasome-inhibitory and cell death-inducing events, demonstrating the ROS-independent proteasome-inhibitory property of copper complexes.
金属离子铜是人类维持正常生物和生理功能所必需的辅助因子。在各种肿瘤组织中发现了高铜水平，并参与肿瘤血管生成过程。泛素-蛋白酶体系统在细胞生长和凋亡中起着重要作用，并已被证明是癌症治疗的新靶点。我们之前报道过，一些有机铜配合物可以抑制蛋白酶体糜蛋白酶样活性，并在人类癌细胞和异种移植模型中诱导细胞凋亡。在本研究中，我们研究了铜的氧化状态（Cu（I）或 Cu（II））对蛋白酶体活性抑制、细胞凋亡诱导和诱导活性氧（ROS）的影响在人类癌细胞中。我们在这里报告了四个主要发现：i）Cu（I）和 Cu（II）都可以抑制纯化的 20S 蛋白酶体的糜蛋白酶样活性，但 Cu（I）比 Cu（II）更有效，ii）纯化的 20S 蛋白酶体蛋白能够将 Cu（II）还原为 Cu（I），表明 Cu（I）是直接与蛋白酶体反应的铜的氧化状态，iii）当与铜配体 neocuproine 络合时，Cu（I）在癌细胞中诱导 ROS 产生的能力比 Cu（II）更高，iv）在癌细胞培养中添加 ROS 清除剂阻断了铜诱导的 ROS 生成，但不能克服铜介导的蛋白酶体抑制和细胞死亡诱导事件，证明了铜配合物具有 ROS 独立的蛋白酶体抑制特性。
