Essential role for oncogenic Ras in tumour maintenance

Nature. 1999 Jul 29;400(6743):468-72. doi: 10.1038/22788.


Advanced malignancy in tumours represents the phenotypic endpoint of successive genetic lesions that affect the function and regulation of oncogenes and tumour-suppressor genes. The established tumour is maintained through complex and poorly understood host-tumour interactions that guide processes such as angiogenesis and immune sequestration. The many different genetic alterations that accompany tumour genesis raise questions as to whether experimental cancer-promoting mutations remain relevant during tumour maintenance. Here we show that melanoma genesis and maintenance are strictly dependent upon expression of H-RasV12G in a doxycycline-inducible H-Ras12G mouse melanoma model null for the tumour suppressor INK4a. Withdrawal of doxycycline and H-RasV12G down-regulation resulted in clinical and histological regression of primary and explanted tumours. The initial stages of regression involved marked apoptosis in the tumour cells and host-derived endothelial cells. Although the regulation of vascular endothelial growth factor (VEGF) was found to be Ras-dependent in vitro, the failure of persistent endogenous and enforced VEGF expression to sustain tumour viability indicates that the tumour-maintaining actions of activated Ras extend beyond the regulation of VEGF expression in vivo. Our results provide genetic evidence that H-RasV12G is important in both the genesis and maintenance of solid tumours.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Animals
  • Apoptosis
  • Doxycycline / pharmacology
  • Endothelial Growth Factors / metabolism
  • Gene Expression Regulation, Neoplastic / drug effects
  • Genes, ras*
  • Lymphokines / metabolism
  • Melanoma / blood supply
  • Melanoma / genetics*
  • Melanoma / immunology
  • Mice
  • Mice, SCID
  • Mice, Transgenic
  • Oncogenes*
  • Tumor Cells, Cultured
  • Vascular Endothelial Growth Factor A
  • Vascular Endothelial Growth Factors


  • Endothelial Growth Factors
  • Lymphokines
  • Vascular Endothelial Growth Factor A
  • Vascular Endothelial Growth Factors
  • Doxycycline