Anticancer effects of ZD6474, a VEGF receptor tyrosine kinase inhibitor, in gefitinib ("Iressa")-sensitive and resistant xenograft models

Cancer Sci. 2004 Dec;95(12):984-9. doi: 10.1111/j.1349-7006.2004.tb03187.x.

Abstract

ZD6474 is a novel, orally available inhibitor of vascular endothelial growth factor (VEGF) receptor-2 (KDR) tyrosine kinase, with additional activity against epidermal growth factor receptor (EGFR) tyrosine kinase. ZD6474 has been shown to inhibit angiogenesis and tumor growth in a range of tumor models. Gefitinib ("Iressa") is an selective EGFR tyrosine kinase inhibitor (TKI) that blocks signal transduction pathways. We examined the antitumor activity of ZD6474 in the gefitinib-sensitive lung adenocarcinoma cell line, PC-9, and a gefitinib-resistant variant (PC-9/ZD). PC-9/ZD cells showed cross-resistance to ZD6474 in an in vitro dye formation assay. In addition, ZD6474 showed dose-dependent inhibition of EGFR phosphorylation in PC-9 cells, but inhibition was only partial in PC-9/ZD cells. ZD6474-mediated inhibition of tyrosine residue phosphorylation (Tyr992 and Tyr1045) on EGFR was greater in PC-9 cells than in PC-9/ZD cells. These findings suggest that the inhibition of EGFR phosphorylation by ZD6474 can contribute a significant, direct growth-inhibitory effect in tumor cell lines dependent on EGFR signaling for growth and/or survival. The effect of ZD6474 (12.5-50 mg/kg/day p.o. for 21 days) on the growth of PC-9 and PC-9/ZD tumor xenografts in athymic mice was also investigated. The greatest effect was seen in gefitinib-sensitive PC-9 tumors, where ZD6474 treatment (>12.5 mg/kg/day) resulted in tumor regression. Dose-dependent growth inhibition, but not tumor regression, was seen in ZD6474-treated PC-9/ZD tumors. These studies demonstrate that the additional EGFR TKI activity may contribute significantly to the antitumor efficacy of ZD6474, in particular in those tumors that are dependent on continued EGFR-signaling for proliferation or survival. In addition, these results provide a preclinical rationale for further investigation of ZD6474 as a potential treatment option for both EGFR-TKI-sensitive and EGFR-TKI-resistant tumors.

MeSH terms

  • Adenocarcinoma / drug therapy
  • Animals
  • Antineoplastic Agents / therapeutic use*
  • Apoptosis / drug effects
  • Carcinoma, Non-Small-Cell Lung / drug therapy*
  • Cell Proliferation / drug effects
  • Drug Resistance, Neoplasm*
  • Enzyme Inhibitors / therapeutic use
  • Female
  • Gefitinib
  • Lung Neoplasms / drug therapy*
  • Mice
  • Mice, Nude
  • Neovascularization, Pathologic / drug therapy
  • Phosphorylation / drug effects
  • Piperidines / therapeutic use*
  • Quinazolines / therapeutic use*
  • Receptors, Vascular Endothelial Growth Factor / antagonists & inhibitors*
  • Tumor Cells, Cultured
  • Tyrosine / metabolism
  • Xenograft Model Antitumor Assays

Substances

  • Antineoplastic Agents
  • Enzyme Inhibitors
  • Piperidines
  • Quinazolines
  • Tyrosine
  • Receptors, Vascular Endothelial Growth Factor
  • Gefitinib
  • N-(4-bromo-2-fluorophenyl)-6-methoxy-7-((1-methylpiperidin-4-yl)methoxy)quinazolin-4-amine