The second targeted therapy was that of mucin-1 (MUC1)-stimulated peripheral blood mononuclear cells (PBMCs; M1SMC), which produce cytotoxic T lymphocytes (CTLs) that kill human breast cancer cells in vitro (6) and prevent human breast cancer cell tumor development in vivo in non-obese diabetic, severe combined immunodeficient (NOD-SCID) mice (7). This evidence concerns the gene MUC1 and breast cancer.