Research into treatments for breast cancer relies more and more on an understanding of how the cells of tumor tissue act when they are exposed to a new or different drug. To find these new or different drugs to treat cancer, researchers are looking at proteins that help cancer cells grow, such as a group of proteins called Kinases. In this study the investigators want to look at the activity of kinases when a particular experimental drug called GSK1120212 is administered. GSK1120212 blocks a kinase called MEK. GSK1120212 is not yet approved by the FDA for use in breast cancer patients. The investigators want to give subjects GSK1120212 for a short period of time (one week) to see how MEK and the other kinases function in cancer cells both before and after the study drug is given. This study is not intended to treat cancer, it is looking at ways that the investigators may treat cancer in the future.