Akt1 and akt3 exert opposing roles in the regulation of vascular tumor growth

Cancer Res. 2015 Jan 1;75(1):40-50. doi: 10.1158/0008-5472.CAN-13-2961. Epub 2014 Nov 11.


Vascular tumors are endothelial cell neoplasms whose mechanisms of tumorigenesis are poorly understood. Moreover, current therapies, particularly those for malignant lesions, have little beneficial effect on clinical outcomes. In this study, we show that endothelial activation of the Akt1 kinase is sufficient to drive de novo tumor formation. Mechanistic investigations uncovered opposing functions for different Akt isoforms in this regulation, where Akt1 promotes and Akt3 inhibits vascular tumor growth. Akt3 exerted negative effects on tumor endothelial cell growth and migration by inhibiting activation of the translation regulatory kinase S6-Kinase (S6K) through modulation of Rictor expression. S6K in turn acted through a negative feedback loop to restrain Akt3 expression. Conversely, S6K signaling was increased in vascular tumor cells where Akt3 was silenced, and the growth of these tumor cells was inhibited by a novel S6K inhibitor. Overall, our findings offer a preclinical proof of concept for the therapeutic utility of treating vascular tumors, such as angiosarcomas, with S6K inhibitors.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Cell Line, Tumor
  • Cell Proliferation / physiology
  • Female
  • Humans
  • Mice
  • Mice, Inbred C57BL
  • Mice, Nude
  • Phosphorylation
  • Proto-Oncogene Proteins c-akt / metabolism*
  • Vascular Neoplasms / enzymology*
  • Vascular Neoplasms / pathology*


  • AKT1 protein, human
  • AKT3 protein, human
  • Akt1 protein, mouse
  • Akt3 protein, mouse
  • Proto-Oncogene Proteins c-akt