title: Bone marrow X kinase-mediated signal transduction in irradiated vascular endothelium.
abstract: Radiation-induced activation of the phosphatidyl inositol-3 kinase/Akt signal transduction pathway requires Akt binding to phosphatidyl-inositol phosphates (PIP) on the cell membrane. The tyrosine kinase bone marrow X kinase (Bmx) binds to membrane-associated PIPs in a manner similar to Akt. Because Bmx is involved in cell growth and survival pathways, it could contribute to the radiation response within the vascular endothelium. We therefore studied Bmx signaling within the vascular endothelium. Bmx was activated rapidly in response to clinically relevant doses of ionizing radiation. Bmx inhibition enhanced the efficacy of radiotherapy in endothelial cells as well as tumor vascular endothelium in lung cancer tumors in mice. Retroviral shRNA knockdown of Bmx protein enhanced human umbilical vascular endothelial cell (HUVEC) radiosensitization. Furthermore, pretreatment of HUVEC with a pharmacologic inhibitor of Bmx, LFM-A13, produced significant radiosensitization of endothelial cells as measured by clonogenic survival analysis and apoptosis as well as functional assays including cell migration and tubule formation. In vivo, LFM-A13, when combined with radiation, resulted in significant tumor microvascular destruction as well as enhanced tumor growth delay. Bmx therefore represents a molecular target for the development of novel radiosensitizing agents.
authors.affiliation: Department of Radiation Oncology, Vanderbilt University School of Medicine, Nashville, TN 37232-5671, USA.
authors.forename: Tianxiang
authors.initials: T
authors.lastname: Tu
authors.forename: Dinesh
authors.initials: D
authors.lastname: Thotala
authors.forename: Ling
authors.initials: L
authors.lastname: Geng
authors.forename: Dennis E
authors.initials: DE
authors.lastname: Hallahan
authors.forename: Christopher D
authors.initials: CD
authors.lastname: Willey
mesh_terms: D000577:Amides / Q000633:toxicity; D001854:Bone Marrow Cells / Q000187:drug effects / Q000201:enzymology; D045744:Cell Line, Tumor; D002470:Cell Survival / Q000187:drug effects; D002478:Cells, Cultured; D004730:Endothelium, Vascular / Q000187:drug effects / Q000201:enzymology / Q000502:physiology* / Q000528:radiation effects*; D006801:Humans; D008175:Lung Neoplasms; D009570:Nitriles / Q000633:toxicity; D011505:Protein-Tyrosine Kinases / Q000187:drug effects / Q000378:metabolism*; D015398:Signal Transduction / Q000502:physiology*; D014471:Umbilical Veins
chemical_list: D000577:Amides; C118451:LFM A13; D009570:Nitriles; C492367:BMX protein, human; D011505:Protein-Tyrosine Kinases