A portion of the PBPCs will be exposed to a disabled virus which either carries genetic material referred to as the multidrug resistance gene (MDR1). The virus will transfer the MDR1 gene into a portion of the patient's PBPCs. The purpose of putting the MDR1 gene into the patients' PBPCs is to try to make these blood cells and their offspring resistant to the toxic effects of certain types of breast cancer chemotherapy. The MDR1 protein (Pgp) that is made from the MDR1 gene makes cells resistant to chemotherapy in laboratory systems by pumping the drug out of cells before the drug is able to kill the cell. Another portion of the patients PBPCs will be exposed to a similar disabled virus carrying a different gene called the NeoR gene. The NeoR gene should not change the effects of chemotherapy on blood forming cells. The purpose of using the NeoR gene is that it will serve as a point of comparison, to see if the presence of the MDR1 drug resistance gene really helps blood forming cells withstand subsequent chemotherapy.