Panobinostat and Letrozole in Treating Patients With Metastatic Breast Cancer

RATIONALE: Panobinostat may stop the growth of tumor cells by blocking some of the enzymes needed for cell growth. Estrogen can cause the growth of breast cancer cells. Hormone therapy using letrozole may fight breast cancer by lowering the amount of estrogen the body makes. Giving panobinostat together with letrozole may be an effective treatment for breast cancer. PURPOSE: This phase I/II trial is studying the side effects and best dose of panobinostat when given together with letrozole and to see how well it works in treating patients with metastatic breast cancer.