We have proved that our BsAb has potent efficiency in inducing the T cell-mediated killing of several MUC1-expressing tumors (cervical cancer, breast cancer, and ovarian carcinoma) and this MUC1/CD3 BsAb could potentially be developed as a therapeutic antibody drug for the treatment of MUC1-expressing tumors, such as breast cancer, ovarian cancer, pancreatic cancer, colon cancer, cervical cancer, and uterine corpus endometrial carcinoma. Here, MUC1 is linked to breast cancer.