Mitogen-activated protein 3 kinase 6 mediates angiogenic and tumorigenic effects via vascular endothelial growth factor expression

Am J Pathol. 2009 Apr;174(4):1553-63. doi: 10.2353/ajpath.2009.080190. Epub 2009 Feb 26.


Genome-wide screening using a small interfering RNA (siRNA) library has revealed novel molecules that are involved in a wide range of physiological responses. The expression of vascular endothelial growth factor (VEGF) is increased under hypoxic conditions, and plays a crucial role in tumor angiogenesis and tissue responses to ischemia. Here, we used a siRNA expression vector library to elucidate molecules that modify VEGF expression. Screening using an siRNA library revealed that MAPKKK6 (MEKK6/MAP3K6) regulates VEGF expression under both normoxic and hypoxic conditions in vitro, although the biological function of MAP3K6 remains unknown. Attenuation of VEGF expression by MAP3K6 inhibition was demonstrated by transient transfection of double-stranded RNA as well as by stable transfection of short hairpin RNA-expressing vectors against MAP3K6. Conditioned medium of MAP3K6-knocked down cells attenuated both endothelial proliferation and capillary network formation in a VEGF-dependent manner in vitro. In addition, tumor cells with down-regulation of MAP3K6 expression showed significant suppression of tumor growth in vivo, which was accompanied by significant repression of vessel formation and VEGF expression in these tumors. The results of this study suggest that MAP3K6 regulates VEGF expression in both normoxia and hypoxia, and that regulation of VEGF by MAP3K6 may play a crucial role in both angiogenesis and tumorigenesis.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Blotting, Western
  • Cell Line, Tumor
  • Endothelial Cells / metabolism
  • Enzyme-Linked Immunosorbent Assay
  • Gene Expression Regulation / physiology*
  • Gene Library
  • Genes, Reporter
  • Humans
  • MAP Kinase Kinase Kinases / metabolism*
  • Mice
  • Neoplasms / genetics*
  • Neoplasms / metabolism
  • Neovascularization, Pathologic / genetics*
  • Neovascularization, Pathologic / metabolism
  • Polymerase Chain Reaction
  • RNA, Small Interfering
  • Transfection
  • Vascular Endothelial Growth Factor A / genetics*
  • Vascular Endothelial Growth Factor A / metabolism
  • Xenograft Model Antitumor Assays


  • RNA, Small Interfering
  • Vascular Endothelial Growth Factor A
  • MAP Kinase Kinase Kinases
  • MAP kinase kinase kinase 6