Integrin Signaling in Mammary Tumor Cell Adhesion and Extravasation in Microvasculature
Bingmei Fu, PhD and Filippo Giancotti, PhD
Despite the widespread recognition of migration as a critical component in tumor malignancy, very little has been learned about the molecular mechanisms governing tumor adhesion and extravasation in vivo. The integrins are a family of receptors that attach cells to other cells and to the extracellular matrix (ECM) and transmit both mechanical and chemical signaling. Integrin signaling contributes to cell survival and growth, as well as adhesion and migration. Our previous study showed that β4 integrin signaling accelerates breast cancer progression by promoting the transition from adenocarcinoma in situ to invasive and metastatic carcinoma. However, our recent results for in vivo tumor cell adhesion in a single microvessel indicated that β4 integrin signaling defective mammary tumor cells adhered twice as much as that of wild type tumor cells. The objective of this pilot project is to investigate the role of α6β4 integrin in tumor cell adhesion and extravasation in in vivo animal models and in vitro cell monolayer and ECM protein coating systems. We shall test the following hypotheses: 1) β4 integrin signaling plays a differential role in mammary tumor cell adhesion and extravasation from that in tumor cell survival and progression; 2) β4 integrin signaling down regulates adhesion but induces migration; and 3) Mechanisms for tumor cell adhesion and extravasation in microvasculature are different from those for leukocyte adhesion and extravasation. The specific aims are: 1) to determine under which integrin ligand (e.g., laminin-5, -4, -2, and -1) coating, β4 signaling defective mammary tumor cells adhere more than wild type tumor cells under static and flow conditions; 2) to determine which cell adhesion molecules on microvascular endothelial cells of metastatic organs (e.g., the lung) are involved in tumor cell adhesion and extravasation through filter-based adhesion/transmigration assays to measure the adhesion/transmigration rates of normal mammary epithelial cell, wild type and β4 signaling defective mammary tumor cells, and leukocytes to/across cultured cell monolayers of microvascular endothelial cells isolated from the lung and muscle; 3) to examine the results from Aim 2 in in vivo animal models or an ex vivo isolated microvessel by using fluorescencelabeled or GFP-transfected tumor cells and fluorescence imaging microscope systems; 4) to determine which specific adhesion molecules at the endothelial surface and in the ECM are involved in tumor cell adhesion and extravasation by using various sized micro-beads coated with anti-ECM proteins (laminin -5, -5, -2, -1) or anti-VEGFR2 to measure the adhesion rates to A) cultured cell monolayer of brain and skeleton muscle microvascular endothelial cells under static and flow conditions and B) mesenteric microvessel wall under flow conditions This project will measure the role of specific adhesion and signaling molecules of tumor cells, endothelial cells and the ECM in tumor metastasis, and hence helps define a new class of targets for therapeutic drug design for cancer.
Shen, S., Fan, J. Cai, B., Lv, Y., Zeng, M., Hao, Y., Giancotti, F. and Fu, B.M.(2010). Vascular Endothelial Growth Factor Enhances Mammary Cancer Cell Adhesion to Endothelium in vivo. Experimental Physiology, 95 (2):369-379
Yonggang Lv, Min Zeng, Angela Pepe, Filippo Giancotti and Bingmei M. Fu “Beta 4 Integrin Signaling on Mammary Cancer Cell Adhesion in the Microcirculation,” Vascular Matrix Biology and Bioengineering Workshop – March 16-19, 2009 at the Telus Conference Center.
Jie Fan, and Bingmei Fu “Effects of VEGF on Brain Endothelium Permeability and Adhesion of Breast Cancer Cells” BMES 2009, Oct. 7-10, Pittsburgh, U.S.A
Jie Fan, Bin Cai, Yanyan Hao, Filippo G. Giancotti, & Bingmei M. Fu. VEGF Effect on Adhesion of Mammary Carcinoma Cells to Brain Microvascular Endothelium. NEBME 2010, New York, NY.
Bin Cai, Jie Fan, Min Zeng, & Bingmei M. Fu. Effects of VEGF on MDA-MB-435s cancer cell adhesion to microvessel walls in vivo. NEBME 2010, New York, NY.