BRAF and breast cancer: We also identified four novel mutations in BRAF, T599K and G596D, which confer high kinase activity, and T310I and E451K, which are consistent with low-activity mutations in BRAF. These mutants were expressed in NT-3 panNET cells and in SKBr3 HER2-expressing breast cancer cells, to determine their effect on downstream signaling, and BRAF K601E RAF inhibitor sensitivity was further studied in 3T3 cells.