The Ras proteins are low molecular-weight GTP-binding
proteins, which function as biological switches playing a key role
in mediation of signal transduction between G-protein-coupled
receptors and downstream events, such as mitogen-activated
protein kinase (MAPK) and Akt.1,2 Mutations or excessive activation
of Ras proteins are found in approximately 30% of human
cancers.3–5 It was reported that the inhibition of excessive activated
Ras proteins may revert malignant cells to a nonmalignant
phenotype and cause tumor regression both in vitro and in vivo.6
As a result, the Ras protein has become an attractive therapeutic
target for intervention of a number of cancers.