Specifically, we evaluated PEDF expression in endocrine-resistant MCF-7:5C, MCF-7:2A, and BT474 breast cancer cells versus endocrine-sensitive MCF-7, T47D, and ZR-75-1 cells and found that PEDF mRNA and protein levels were dramatically reduced in the endocrine-resistant breast cancer cell lines compared with the endocrine-sensitive cell lines. The gene discussed is SERPINF1; the disease is breast cancer.