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. The investigators are giving this drug for research purposes only. The length of time it is being given is not intended to treat cancer.