Tumor endothelial cells acquire drug resistance by MDR1 up-regulation via VEGF signaling in tumor microenvironment

Am J Pathol. 2012 Mar;180(3):1283-1293. doi: 10.1016/j.ajpath.2011.11.029. Epub 2012 Jan 13.


Tumor endothelial cells (TECs) are therapeutic targets in anti-angiogenic therapy. Contrary to the traditional assumption, TECs can be genetically abnormal and might also acquire drug resistance. In this study, mouse TECs and normal ECs were isolated to investigate the drug resistance of TECs and the mechanism by which it is acquired. TECs were more resistant to paclitaxel with the up-regulation of multidrug resistance (MDR) 1 mRNA, which encodes the P-glycoprotein, compared with normal ECs. Normal human microvascular ECs were cultured in tumor-conditioned medium (CM) and became more resistant to paclitaxel through MDR1 mRNA up-regulation and nuclear translocation of Y-box-binding protein 1, which is an MDR1 transcription factor. Vascular endothelial growth factor (VEGF) receptor 2 (VEGFR2) and Akt were activated in human microvascular ECs by tumor CM. We observed that tumor CM contained a significantly high level of VEGF. A VEGFR kinase inhibitor, Ki8751, and a phosphatidylinositol 3-kinase-Akt inhibitor, LY294002, blocked tumor CM-induced MDR1 up-regulation. MDR1 up-regulation, via the VEGF-VEGFR pathway in the tumor microenvironment, is one of the mechanisms of drug resistance acquired by TECs. We observed that VEGF secreted from tumors up-regulated MDR1 through the activation of VEGFR2 and Akt. This process is a novel mechanism of the acquisition of drug resistance by TECs in the tumor microenvironment.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • ATP Binding Cassette Transporter, Subfamily B, Member 1 / metabolism*
  • Antineoplastic Agents, Phytogenic / therapeutic use
  • Cell Proliferation
  • Drug Resistance, Neoplasm / physiology*
  • Endothelial Cells / physiology
  • Humans
  • Neoplasms / drug therapy*
  • Paclitaxel / therapeutic use
  • Phenylurea Compounds / pharmacology
  • Quinolines / pharmacology
  • Signal Transduction / physiology*
  • Transplantation, Heterologous
  • Tubulin Modulators / therapeutic use
  • Tumor Microenvironment / physiology
  • Up-Regulation
  • Vascular Endothelial Growth Factor A / physiology*
  • Vascular Endothelial Growth Factor Receptor-2 / antagonists & inhibitors
  • Y-Box-Binding Protein 1 / metabolism


  • ATP Binding Cassette Transporter, Subfamily B, Member 1
  • Antineoplastic Agents, Phytogenic
  • N-(2,4-difluorophenyl)-N'-(4-((6,7-dimethoxy-4-quinolyl)oxy)-2-fluorophenyl)urea
  • Phenylurea Compounds
  • Quinolines
  • Tubulin Modulators
  • Vascular Endothelial Growth Factor A
  • Y-Box-Binding Protein 1
  • YBX1 protein, human
  • Vascular Endothelial Growth Factor Receptor-2
  • Paclitaxel