Reddy Ramachandra K, Dubeau Louis, Kleiner Heather, Parr Tyler, Nichols Peter, Ko Bryce, Dong Dezheng, Ko Howard, Mao Changhui, DiGiovanni John, Lee Amy S
Department of Biochemistry and Molecular Biology, University of Southern California/Norris Comprehensive Cancer Center, University of Southern California Keck School of Medicine, Los Angeles, California 90089-9176, USA.
Cancer Res. 2002 Dec 15;62(24):7207-12.
A major challenge in treating cancer is the difficulty of bringing therapy to poorly perfused areas of solid tumors, which are often most resistant to chemotherapy and radiation. GRP94 is a chaperone protein localized in the endoplasmic reticulum with antiapoptotic properties. We report here that in vitro the proximal murine grp94 promoter is regulated differently from the hypoxia response element fused to the SV40 minimal promoter, with glucose starvation as an inducer of grp94 but a potent repressor of the hypoxia response element/SV40 fusion promoter. Through the use of transgenic mouse models, we showed that LacZ transgene expression driven by the grp94 promoter was strongly activated not only in spontaneous but also in a variety of chemically induced tumors. We additionally discovered that macrophages in the vicinity of malignant tumor showed a high level of transgene expression, consistent with intense beta-galactosidase staining at boundaries between viable tumor cells and necrotic areas. Isolated macrophages also showed grp94 mRNA and transgene activation under glucose starvation in vitro. In contrast, transgene activity was not detected in the normal tissue counterparts of any of the malignant tumors examined or macrophages associated with normal organs. These studies provide direct evidence that the tumor microenvironment is a potent physiological inducer of the grp94 promoter. The unique properties of the grp94 promoter suggest that it may offer a novel tool for directing transcription of therapeutic agents to tumors particularly in resistant regions bordering necrotic areas, delivered through standard vectors or macrophages.
治疗癌症的一个主要挑战在于，难以将治疗手段作用于实体瘤中灌注不良的区域，这些区域往往对化疗和放疗最具抗性。GRP94是一种定位于内质网的伴侣蛋白，具有抗凋亡特性。我们在此报告，在体外，近端小鼠grp94启动子的调控方式与融合到SV40最小启动子的缺氧反应元件不同，葡萄糖饥饿是grp94的诱导剂，但却是缺氧反应元件/SV40融合启动子的强效抑制剂。通过使用转基因小鼠模型，我们发现由grp94启动子驱动的LacZ转基因表达不仅在自发肿瘤中，而且在多种化学诱导的肿瘤中都被强烈激活。我们还发现，恶性肿瘤附近的巨噬细胞显示出高水平的转基因表达，这与活肿瘤细胞和坏死区域边界处强烈的β-半乳糖苷酶染色一致。体外分离的巨噬细胞在葡萄糖饥饿条件下也显示出grp94 mRNA和转基因激活。相比之下，在所检查的任何恶性肿瘤的正常组织对应物或与正常器官相关的巨噬细胞中均未检测到转基因活性。这些研究提供了直接证据，表明肿瘤微环境是grp94启动子的强效生理诱导剂。grp94启动子的独特特性表明，它可能提供一种新工具，用于将治疗剂的转录导向肿瘤，特别是在与坏死区域接壤的抗性区域，可通过标准载体或巨噬细胞递送。
