Pargyline reduces estrogen-mediated tumor growth. Nude mice implanted with estradiol pellets were injected subcutaneously with (A) MCF-7 or (B) MCF-7-PELP1 model cells. After 4 weeks, mice were treated with or without pargyline (n = 10). Tumor growth was measured at weekly intervals. Tumor volume is shown. Ki-67 expression and TUNEL analysis was done on (C) MCF-7 and (D) MCF-7-PELP1 xenografts that were treated with or without pargyline. Representative images are shown. Quantitation performed as described in Materials and methods. ****P < 0.0001, **P < 0.001 *P < 0.05. PELP1, proline glutamic acid and leucine-rich protein 1; TUNEL, terminal deoxynucleotidyl transferase dUTP nick end-labeling.