title: Induction of proline-rich tyrosine kinase 2 activation-mediated C6 glioma cell invasion after anti-vascular endothelial growth factor therapy.
abstract: BACKGROUND
  Anti-angiogenic therapy inhibits tumor growth and is considered as a potential clinical therapy for malignant glioma. However, inevitable recurrences and unexpected tumor resistance, particularly increased invasion ability of glioma cell, were observed after anti-angiogenic treatment. The underlying mechanism remains undetermined. Focal adhesion kinase (FAK) and proline-rich tyrosine kinase 2 (Pyk2) are closely associated with cell migration; therefore, we investigated the possible role of these kinases in rat C6 glioma cell invasion induced by bevacizumab, a recombinant monoclonal antibody against vascular endothelial growth factor (VEGF).
  
  
  METHODS
  The effects of bevacizumab on migration and invasion of C6 glioma cells were investigated in vitro and in vivo. The cells proliferation, migration, and invasion were determined by MTT assay, wound healing, and transwell assay, respectively. Invasive potential of glioma cells in vivo was assessed by counting vimentin-positive cells crossing the solid tumor rim by immunohistochemical staining. The total and phosphorylated protein levels of FAK and Pyk2 were detected by Western blotting.
  
  
  RESULTS
  Bevacizumab exposure increased migration and invasion of cultured C6 cells in a concentration-dependent manner. In addition, the continuous bevacizumab treatment also promoted tumor invasion in rat C6 intracranial glioma models. Bevacizumab treatment enhanced Pyk2 phosphorylation at Tyr402, but no effect on FAK phosphorylation at Tyr397 both in vitro and in vivo. Knockdown of Pyk2 by siRNA or inhibition of Pyk2 phosphorylation by Src kinase specific inhibitor PP1 partially inhibited bevacizumab-induced cell invasion in cultured C6 glioma cells. Furthermore, the combined administration of bevacizumab and PP1 significantly suppressed glioma cell invasion into surrounding brain tissues compared to bevacizumab treatment alone in experimental rats.
  
  
  CONCLUSIONS
  These results suggest that anti-VEGF treatment promotes glioma cell invasion via activation of Pyk2. Inhibition of Pyk2 phosphorylation might be a potential target to ameliorate the therapeutic efficiency of anti-VEGF treatment.
authors.forename: Cheng-Shi
authors.initials: CS
authors.lastname: Xu
authors.forename: Ze-Fen
authors.initials: ZF
authors.lastname: Wang
authors.forename: Li-Ming
authors.initials: LM
authors.lastname: Dai
authors.forename: Sheng-Hua
authors.initials: SH
authors.lastname: Chu
authors.forename: Ling-Ling
authors.initials: LL
authors.lastname: Gong
authors.forename: Ming-Huan
authors.initials: MH
authors.lastname: Yang
authors.affiliation: Department of Neurosurgery, Zhongnan Hospital of Wuhan University, Wuhan 430071, PR China. lizhiqiang@whu.edu.cn.
authors.forename: Zhi-Qiang
authors.initials: ZQ
authors.lastname: Li
mesh_terms: D000818:Animals; D061067:Antibodies, Monoclonal, Humanized / Q000627:therapeutic use*; D000068258:Bevacizumab; D001932:Brain Neoplasms / Q000188:drug therapy / Q000201:enzymology / Q000473:pathology*; D045744:Cell Line, Tumor; D004789:Enzyme Activation; D004790:Enzyme Induction; D051418:Focal Adhesion Kinase 2 / Q000378:metabolism*; D005910:Glioma / Q000188:drug therapy / Q000201:enzymology / Q000473:pathology*; D009361:Neoplasm Invasiveness; D009362:Neoplasm Metastasis; D051381:Rats
chemical_list: D061067:Antibodies, Monoclonal, Humanized; D000068258:Bevacizumab; D051418:Focal Adhesion Kinase 2