title: Stress chaperone GRP78/BiP confers chemoresistance to tumor-associated endothelial cells.
abstract: The tumor vasculature is essential for tumor growth and survival and is a key target for anticancer therapy. Glioblastoma multiforme, the most malignant form of brain tumor, is highly vascular and contains abnormal vessels, unlike blood vessels in normal brain. Previously, we showed that primary cultures of human brain endothelial cells, derived from blood vessels of malignant glioma tissues (TuBEC), are physiologically and functionally different from endothelial cells derived from nonmalignant brain tissues (BEC) and are substantially more resistant to apoptosis. Resistance of TuBEC to a wide range of current anticancer drugs has significant clinical consequences as it represents a major obstacle toward eradication of residual brain tumor. We report here that the endoplasmic reticulum chaperone GRP78/BiP is generally highly elevated in the vasculature derived from human glioma specimens, both in situ in tissue and in vitro in primary cell cultures, compared with minimal GRP78 expression in normal brain tissues and blood vessels. Interestingly, TuBEC constitutively overexpress GRP78 without concomitant induction of other major unfolded protein response targets. Resistance of TuBEC to chemotherapeutic agents such as CPT-11, etoposide, and temozolomide can be overcome by knockdown of GRP78 using small interfering RNA or chemical inhibition of its catalytic site. Conversely, overexpression of GRP78 in BEC rendered these cells resistant to drug treatments. Our findings provide the proof of principle that targeting GRP78 will sensitize the tumor vasculature to chemotherapeutic drugs, thus enhancing the efficacy of these drugs in combination therapy for glioma treatment.
authors: Department of Biochemistry and Molecular Biology, Keck School of Medicine, University of Southern California, Los Angeles, CA 90089-9176, USA.
authors: Jenilyn J
authors: JJ
authors: Virrey
authors: Dezheng
authors: D
authors: Dong
authors: Caryn
authors: C
authors: Stiles
authors: John B
authors: JB
authors: Patterson
authors: Ligaya
authors: L
authors: Pen
authors: Min
authors: M
authors: Ni
authors: Axel H
authors: AH
authors: Schönthal
authors: Thomas C
authors: TC
authors: Chen
authors: Florence M
authors: FM
authors: Hofman
authors: Amy S
authors: AS
authors: Lee
mesh_terms: D000970:Antineoplastic Agents / Q000494:pharmacology; D001932:Brain Neoplasms / Q000098:blood supply / Q000201:enzymology / Q000473:pathology*; D020169:Caspases / Q000378:metabolism; D002392:Catechin / Q000031:analogs & derivatives / Q000494:pharmacology; D016923:Cell Death / Q000187:drug effects; D019008:Drug Resistance, Neoplasm / Q000187:drug effects; D000091342:Endoplasmic Reticulum Chaperone BiP; D042783:Endothelial Cells / Q000187:drug effects / Q000473:pathology*; D006360:Heat-Shock Proteins / Q000037:antagonists & inhibitors / Q000378:metabolism*; D006801:Humans; D018832:Molecular Chaperones / Q000037:antagonists & inhibitors / Q000378:metabolism*; D017510:Protein Folding; D034741:RNA, Small Interfering / Q000378:metabolism
chemical_list: D000970:Antineoplastic Agents; D000091342:Endoplasmic Reticulum Chaperone BiP; C000717247:HSPA5 protein, human; D006360:Heat-Shock Proteins; D018832:Molecular Chaperones; D034741:RNA, Small Interfering; D002392:Catechin; C045651:epigallocatechin gallate; D020169:Caspases