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Research Articles: Therapeutics, Targets, and Development

Inhibition of phosphatidylinositol-3-kinase and mitogen-activated protein kinase kinase 1/2 prevents melanoma development and promotes melanoma regression in the transgenic TPRas mouse model

¹ Division of Radiation and Cancer Biology, Stanford University, Stanford, California; ² Division of Epidemiology and Biostatistics, and ³ Arizona Cancer Center, University of Arizona, Tucson, Arizona

Requests for reprints: Marianne Broome Powell, Division of Radiation and Cancer Biology, 269 Campus Drive, CCSR-S-1230, Stanford 94305, CA. Phone: 650-498-5874. E-mail: mbp{at}stanford.edu

Abstract

A number of human melanomas show hyperactivation of the Ras pathway due to mutations of the molecule or alteration of upstream or downstream effectors. In this study, we evaluated the effect of blocking the two Ras downstream pathways phosphatidylinositol-3-kinase/Akt and Raf/mitogen-activated protein kinase kinase/extracellular signal–regulated kinase on melanoma development and regression in the TPRas mouse model. The inhibition of these two signaling cascades by topically applied Ly294002 and U0126 significantly delayed melanoma development and significantly decreased the tumor incidence, particularly when the drugs were applied in combination. Treatment with the inhibitors of established melanomas resulted in complete remission in 33% of mice and partial regression in 46% of mice when drugs were delivered in combination. These responses correlated with increased apoptosis and decreased proliferation both in vitro and in vivo and reduced tumor angiogenesis. In conclusion, this study strongly supports the role of the phosphatidylinositol-3-kinase/Akt and Raf/mitogen-activated protein kinase kinase/extracellular signal–regulated kinase pathways in the development and maintenance of Ras-dependent melanomas and supports the notion that specific inhibition of these effectors may represent a very promising avenue for the treatment and prevention of the disease. [Mol Cancer Ther 2006;5(12):3071–7]

Grant support: NIH grants CA090897 and CA27502.

The costs of publication of this article were defrayed in part by the payment of page charges. This article must therefore be hereby marked advertisement in accordance with 18 U.S.C. Section 1734 solely to indicate this fact.

Received 5/ 9/06; revised 9/13/06; accepted 10/25/06.