Using the PyMT, EO771 and 4T1.2 breast cancer models, each with different metastatic capacities, we showed that while NAC prevents Hif-1α stabilization in vitro, it does not reduce primary tumor growth and that it, in fact, increases the number of metastatic foci in an experimental metastasis model, raising the question of whether NAC is truly beneficial in the treatment of breast cancer. The gene discussed is HIF1A; the disease is neoplasm.