The Raf proteins are a family of serine/threonine-specific kinases that serve as a central intermediate in transmitting extracellular signals to the mitogen-activated protein kinase cascade, which controls cell growth, differentiation and survival. Three isoforms of Raf proteins have been found in mammalian cells: Raf-1, A-Raf and B-Raf. The B-raf involved in signal transduction from the membrane to the nucleus. It has been reported that T598 and S601 are the major phosphorylation sites of B-Raf in response to oncogenic Ras, and phosphorylation of these two residues is required for full activation of B-Raf. Mutations in the B-Raf gene have been reported in a number of human cancers, including malignant melanoma, thyroid cancer, and colorectal carcinoma. The poly6327 antibody recognizes human phosphorylated B-Raf (Thr598/Ser601) and has been shown to be useful for immunoflorence staining.