title: In Vivo FRET Imaging of Tumor Endothelial Cells Highlights a Role of Low PKA Activity in Vascular Hyperpermeability.
abstract: Vascular hyperpermeability is a pathological hallmark of cancer. Previous in vitro studies have elucidated roles of various signaling molecules in vascular hyperpermeability; however, the activities of such signaling molecules have not been examined in live tumor tissues for technical reasons. Here, by in vivo two-photon excitation microscopy with transgenic mice expressing biosensors based on Förster resonance energy transfer, we examined the activity of protein kinase A (PKA), which maintains endothelial barrier function. The level of PKA activity was significantly lower in the intratumoral endothelial cells than the subcutaneous endothelial cells. PKA activation with a cAMP analogue alleviated the tumor vascular hyperpermeability, suggesting that the low PKA activity in the endothelial cells may be responsible for the tumor-tissue hyperpermeability. Because the vascular endothelial growth factor (VEGF) receptor is a canonical inducer of vascular hyperpermeability and a molecular target of anticancer drugs, we examined the causality between VEGF receptor activity and the PKA activity. Motesanib, a kinase inhibitor for VEGF receptor, activated tumor endothelial PKA and reduced the vascular permeability in the tumor. Conversely, subcutaneous injection of VEGF decreased endothelial PKA activity and induced hyperpermeability of subcutaneous blood vessels. Notably, in cultured human umbilical vascular endothelial cells, VEGF activated PKA rather than decreasing its activity, highlighting the remarkable difference between its actions in vitro and in vivo These data suggested that the VEGF receptor signaling pathway increases vascular permeability, at least in part, by reducing endothelial PKA activity in the live tumor tissue. Cancer Res; 76(18); 5266-76. ©2016 AACR.
authors.affiliation: Department of Pathology and Biology of Diseases, Graduate School of Medicine, Kyoto University, Kyoto, Japan. Medical Imaging System Development Center, R&D Headquarters, Canon Inc., Japan.
authors.forename: Fumio
authors.initials: F
authors.lastname: Yamauchi
authors.affiliation: Department of Pathology and Biology of Diseases, Graduate School of Medicine, Kyoto University, Kyoto, Japan. Innovative Techno-Hub for Integrated Medical Bio-Imaging, Kyoto University, Kyoto, Japan.
authors.forename: Yuji
authors.initials: Y
authors.lastname: Kamioka
authors.affiliation: Medical Imaging System Development Center, R&D Headquarters, Canon Inc., Japan.
authors.forename: Tetsuya
authors.initials: T
authors.lastname: Yano
authors.affiliation: Department of Pathology and Biology of Diseases, Graduate School of Medicine, Kyoto University, Kyoto, Japan. matsuda.michiyuki.2c@kyoto-u.ac.jp.
authors.forename: Michiyuki
authors.initials: M
authors.lastname: Matsuda
mesh_terms: D000818:Animals; D002199:Capillary Permeability / Q000502:physiology*; D045744:Cell Line, Tumor; D017868:Cyclic AMP-Dependent Protein Kinases / Q000378:metabolism*; D004195:Disease Models, Animal; D042783:Endothelial Cells / Q000201:enzymology* / Q000473:pathology; D031541:Fluorescence Resonance Energy Transfer; D061307:Human Umbilical Vein Endothelial Cells / Q000473:pathology; D006801:Humans; D007150:Immunohistochemistry; D051379:Mice; D008822:Mice, Transgenic; D009374:Neoplasms, Experimental / Q000473:pathology*; D040262:Receptors, Vascular Endothelial Growth Factor / Q000378:metabolism; D042461:Vascular Endothelial Growth Factor A / Q000378:metabolism
chemical_list: D042461:Vascular Endothelial Growth Factor A; D040262:Receptors, Vascular Endothelial Growth Factor; D017868:Cyclic AMP-Dependent Protein Kinases