title: Plasminogen kringle 5 induces apoptosis of brain microvessel endothelial cells: sensitization by radiation and requirement for GRP78 and LRP1.
abstract: Recombinant plasminogen kringle 5 (rK5) has been shown to induce apoptosis of dermal microvessel endothelial cells (MvEC) in a manner that requires glucose-regulated protein 78 (GRP78). As we are interested in antiangiogenic therapy for glioblastoma tumors, and the effectiveness of antiangiogenic therapy can be enhanced when combined with radiation, we investigated the proapoptotic effects of rK5 combined with radiation on brain MvEC. We found that rK5 treatment of brain MvEC induced apoptosis in a dose- and time-dependent manner and that prior irradiation significantly sensitized (500-fold) the cells to rK5-induced apoptosis. The rK5-induced apoptosis of both unirradiated and irradiated MvEC required expression of GRP78 and the low-density lipoprotein receptor-related protein 1 (LRP1), a scavenger receptor, based on down-regulation studies with small interfering RNA, and blocking studies with either a GRP78 antibody or a competitive inhibitor of ligand binding to LRP1. Furthermore, p38 mitogen-activated protein kinase was found to be a necessary downstream effector for rK5-induced apoptosis. These data suggest that irradiation sensitizes brain MvEC to the rK5-induced apoptosis and that this signal requires LRP1 internalization of GRP78 and the activation of p38 mitogen-activated protein kinase. Our findings suggest that prior irradiation would have a dose-sparing effect on rK5 antiangiogenic therapy for brain tumors and further suggest that the effects of rK5 would be tumor specific, as the expression of GRP78 protein is up-regulated on the brain MvEC in glioblastoma tumor biopsies compared with the normal brain.
authors: Division of Neuropathology, Department of Pathology, University of Alabama at Birmingham, Birmingham, Alabama, USA.
authors: Braden C
authors: BC
authors: McFarland
authors: Jerry
authors: J
authors: Stewart
authors: Amal
authors: A
authors: Hamza
authors: Robert
authors: R
authors: Nordal
authors: Donald J
authors: DJ
authors: Davidson
authors: Jack
authors: J
authors: Henkin
authors: Candece L
authors: CL
authors: Gladson
mesh_terms: D020533:Angiogenesis Inhibitors / Q000627:therapeutic use; D017209:Apoptosis; D001921:Brain / Q000502:physiology*; D001932:Brain Neoplasms / Q000188:drug therapy / Q000401:mortality / Q000473:pathology; D002462:Cell Membrane / Q000502:physiology; D002560:Cerebrovascular Circulation / Q000502:physiology* / Q000528:radiation effects; D000091342:Endoplasmic Reticulum Chaperone BiP; D004730:Endothelium, Vascular / Q000502:physiology* / Q000528:radiation effects; D005909:Glioblastoma / Q000188:drug therapy / Q000401:mortality / Q000473:pathology; D006360:Heat-Shock Proteins / Q000502:physiology*; D006801:Humans; D015151:Immunoblotting; D008833:Microcirculation / Q000502:physiology* / Q000528:radiation effects; D009389:Neovascularization, Pathologic / Q000188:drug therapy; D010446:Peptide Fragments / Q000502:physiology* / Q000528:radiation effects; D010958:Plasminogen / Q000502:physiology* / Q000528:radiation effects; D011973:Receptors, LDL / Q000502:physiology*; D016019:Survival Analysis; D025521:Tumor Suppressor Proteins / Q000502:physiology*
chemical_list: D020533:Angiogenesis Inhibitors; D000091342:Endoplasmic Reticulum Chaperone BiP; C000717247:HSPA5 protein, human; D006360:Heat-Shock Proteins; D010446:Peptide Fragments; D011973:Receptors, LDL; D025521:Tumor Suppressor Proteins; C491499:plasminogen kringle 5; D010958:Plasminogen