This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. This research furthers the research of previous studies (MT2003-01 and MT2004-25) which were to determine whether a specific preparatory regimen (cyclophossphamide and fludarabine) could create an environment in which infused NK cells can grow and effectively treat patients with relapsed AML. This study will test the previous regimen in patients with Breast Cancer. The preparative regimen remains the same as in MT2003-01, and as in MT2004-25 cells will be enhanced by the removal of T and B-lymphocytes, which we believe will increase the rates of complete remission by allowing better NK cell expansion.