The Ras/Raf/MEK/ERK signal transduction pathway is critical to the survival, growth, and proliferation of cells and has been implicated in several human cancers. B-Raf is a serine-threonine kinase in this pathway that has been shown to have a much higher basal kinase activity relative to either of its isoforms (A-Raf or C-Raf), and recently has been reported to be frequently mutated in various human cancers. Activating B-Raf mutations, most notably V600E (formerly termed ...