Mediators of glioblastoma resistance and invasion during antivascular endothelial growth factor therapy.
OBJECTIVE
Vascular endothelial growth factor (VEGF) has been identified as a critical regulator of angiogenesis. Currently, several different strategies are being used to target the VEGF-VEGF receptor signal transduction pathway in glioblastoma. Although anti-VEGF therapy seems be effective in normalizing abnormal tumor vasculature, leading to an enhanced response to radiation and chemotherapy, tumors eventually become resistant to the therapy and adopt a highly infiltrative and invasive phenotype.


METHODS
In the present study, we evaluated the effects of anti-VEGF therapy (bevacizumab) on glioblastoma invasion both in vitro and in vivo and evaluated the angiogenesis- and invasion-related mediators of developed resistance to this therapy.


RESULTS
We found that glioblastoma tumors escaped from antiangiogenic treatment by (a) reactivating angiogenesis through up-regulation of other proangiogenic factors and (b) invading normal brain areas, which was seen in association with up-regulation of matrix metalloproteinase (MMP)-2, MMP-9, and MMP-12; secreted protein, acidic, cysteine-rich; and tissue inhibitor of metalloproteinase 1. In addition to the paracrine effects of VEGF on endothelial cells, autocrine VEGF signaling seemed to regulate glioblastoma invasion because anti-VEGF therapy increased tumor invasiveness in vitro.


CONCLUSIONS
Collectively, these findings reinforce the importance of VEGF in regulating tumor invasion and identify potential mediators of resistance to targeted VEGF therapy. These results will be important for developing novel combination therapies to overcome this resistance phenotype.
Lucio-Eterovic
Agda K
AK
Brain Tumor Center, Department of Neuro-Oncology, The University of Texas M. D. Anderson Cancer Center, Houston, Texas 77030, USA.
Piao
Yuji
Y
de Groot
John F
JF
D020533:Angiogenesis Inhibitors / Q000494:pharmacology; D000818:Animals; D000911:Antibodies, Monoclonal / Q000494:pharmacology*; D061067:Antibodies, Monoclonal, Humanized; D000068258:Bevacizumab; D015153:Blotting, Western; D045744:Cell Line, Tumor; D002465:Cell Movement / Q000187:drug effects; D054370:Chemokine CXCL9 / Q000235:genetics / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D019008:Drug Resistance, Neoplasm; D004797:Enzyme-Linked Immunosorbent Assay; D015972:Gene Expression Regulation, Neoplastic / Q000187:drug effects; D005909:Glioblastoma / Q000188:drug therapy* / Q000378:metabolism / Q000473:pathology; D006801:Humans; D053208:Kaplan-Meier Estimate; D053508:Matrix Metalloproteinase 12 / Q000235:genetics / Q000378:metabolism; D051379:Mice; D008819:Mice, Nude; D009361:Neoplasm Invasiveness; D020133:Reverse Transcriptase Polymerase Chain Reaction; D012259:Ribonuclease, Pancreatic / Q000378:metabolism; D042461:Vascular Endothelial Growth Factor A / Q000037:antagonists & inhibitors* / Q000276:immunology / Q000378:metabolism; D040281:Vascular Endothelial Growth Factor Receptor-1 / Q000235:genetics / Q000378:metabolism; D040301:Vascular Endothelial Growth Factor Receptor-2 / Q000235:genetics / Q000378:metabolism; D023041:Xenograft Model Antitumor Assays
D020533:Angiogenesis Inhibitors; D000911:Antibodies, Monoclonal; D061067:Antibodies, Monoclonal, Humanized; D054370:Chemokine CXCL9; D042461:Vascular Endothelial Growth Factor A; D000068258:Bevacizumab; D040281:Vascular Endothelial Growth Factor Receptor-1; D040301:Vascular Endothelial Growth Factor Receptor-2; C046366:angiogenin; D012259:Ribonuclease, Pancreatic; D053508:Matrix Metalloproteinase 12