Phase I Study of the Combination of MLN9708 and Fulvestrant

Participants in this study will have been diagnosed with advanced breast cancer that has become worse while being treated with fulvestrant. Participants will have estrogen-receptor positive disease, and have completed menopause. There is information from research labs which suggests that drugs that work like MLN9708 help kill breast cancer cells that have been treated with fulvestrant. The purpose of the study is to determine the proper dose as well as the good and bad effects of MLN9708 when it is given in combination with fulvestrant. The Investigators also want to learn more about how the drug combination affects tumor cells. The amount of MLN9708 participants receive will be determined by when they enter this study. Three different doses will be given to different participants. The Investigators expect to enroll a total of 12-18 people.