Liang Lu, Yue Zhiwei, Du Wei, Li Yang, Tao Hongyan, Wang Di, Wang Ran, Huang Ziwei, He Ningning, Xie Xiaoyan, Han Zhongchao, Liu Na, Li Zongjin
Nankai University School of Medicine, Tianjin, China.
Beijing Institute of Health and Stem Cells, Health & Biotech Co., Beijing, China.
Cell Physiol Biochem. 2017;42(1):407-415. doi: 10.1159/000477485. Epub 2017 May 25.
Tumor derived vascular endothelial growth factor (VEGF) can stimulate proliferation and migration of endothelial cells and recruit endothelial progenitor cells into tumors for vascular formation via a paracrine manner. Now increasing evidence suggests that VEGF also serves as an autocrine factor promoting cell survival and tumor angiogenesis. Real time visualization of VEGF activity in the early stages of tumor formation using molecular imaging will provide unprecedented insight into the biological processes of cancer.
The mouse breast cancer cell line 4T1 was transfected with an inducible, bidirectional tetracycline (Bi-Tet) promoter driving VEGF and renilla luciferase (Rluc). This was used to quantitatively image conditional switching of VEGF by bioluminescence imaging (BLI) under the control of systemic administration of doxycycline. Simultaneously, 4T1 cells were labelled with the double fusion reporter gene (Fluc-eGFP) to establish a breast cancer model.
We found that inducible VEGF could promote proliferation and attenuate apoptosis due to oxidative stress in an autocrine manner in vitro. In vivo studies revealed that induction of VEGF expression during early tumor development not only dramatically enhanced tumor growth but also increased tumor angiogenesis as visualized by BLI. Finally, immunohistochemistry staining confirmed that inducing VEGF expression promoted cell survival and tumor neovascularization.
Together the inducible bidirectional tetracycline (Bi-Tet) co-expression system combined with the dual bioluminescence imaging (BLI) system provides a platform to investigate a target gene's role in the pathologic process of cancer and facilitates noninvasive monitoring of biological responses in real time.
肿瘤衍生的血管内皮生长因子（VEGF）可通过旁分泌方式刺激内皮细胞增殖和迁移，并将内皮祖细胞募集到肿瘤中以形成血管。现在越来越多的证据表明，VEGF还作为一种自分泌因子促进细胞存活和肿瘤血管生成。使用分子成像技术在肿瘤形成早期实时可视化VEGF活性，将为癌症的生物学过程提供前所未有的见解。
用可诱导的双向四环素（Bi-Tet）启动子驱动VEGF和海肾荧光素酶（Rluc）转染小鼠乳腺癌细胞系4T1。在强力霉素全身给药的控制下，用于通过生物发光成像（BLI）对VEGF的条件性切换进行定量成像。同时，用双融合报告基因（Fluc-eGFP）标记4T1细胞以建立乳腺癌模型。
我们发现，诱导型VEGF在体外可通过自分泌方式促进增殖并减轻氧化应激诱导的细胞凋亡。体内研究表明，在肿瘤早期发育过程中诱导VEGF表达不仅显著增强肿瘤生长，而且通过BLI可见增加肿瘤血管生成。最后，免疫组织化学染色证实诱导VEGF表达可促进细胞存活和肿瘤新生血管形成。
诱导型双向四环素（Bi-Tet）共表达系统与双生物发光成像（BLI）系统相结合，共同提供了一个平台，用于研究靶基因在癌症病理过程中的作用，并有助于实时无创监测生物学反应。
