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. 2011 Mar;2(3):359-72.
doi: 10.1177/1947601911412376.

Therapeutic strategies for targeting ras proteins

Stephan Gysin  1 , Megan Salt, Amy Young, Frank McCormick
Affiliations

Therapeutic strategies for targeting ras proteins

Stephan Gysin et al. Genes Cancer. 2011 Mar.

Abstract

Ras genes are frequently activated in cancer. Attempts to develop drugs that target mutant Ras proteins have, so far, been unsuccessful. Tumors bearing these mutations, therefore, remain among the most difficult to treat. Most efforts to block activated Ras have focused on pathways downstream. Drugs that inhibit Raf kinase have shown clinical benefit in the treatment of malignant melanoma. However, these drugs have failed to show clinical benefit in Ras mutant tumors. It remains unclear to what extent Ras depends on Raf kinase for transforming activity, even though Raf proteins bind directly to Ras and are certainly major effectors of Ras action in normal cells and in development. Furthermore, Raf kinase inhibitors can lead to paradoxical activation of the MAPK pathway. MEK inhibitors block the Ras-MAPK pathway, but often activate the PI3'-kinase, and have shown little clinical benefit as single agents. This activation is mediated by EGF-R and other receptor tyrosine kinases through relief of a negative feedback loop from ERK. Drug combinations that target multiple points within the Ras signaling network are likely to be necessary to achieve substantial clinical benefit. Other effectors may also contribute to Ras signaling and provide a source of targets. In addition, unbiased screens for genes necessary for Ras transformation have revealed new potential targets and have added to our understanding of Ras cancer biology.

Keywords: MAPK kinase; Raf; Ras; signal transduction; targeted therapy.

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Conflict of interest statement

The author(s) declared the following potential conflicts of interest with respect to the research, authorship, and/or publication of this article: Dr. McCormick is a consultant to ONYX, and this review discusses the use of sorafenib. Drs. Gysin, Salt, and Young declare no conflicts of interest.

Figures

Figure 1.
Figure 1.
Ras processing.
Figure 2.
Figure 2.
C-termini of Ras proteins.
Figure 3.
Figure 3.
Pathways downstream of Ras.
See this image and copyright information in PMC

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