Abstract: 455

ZERANOL STIMULATES ESTROGEN-REGULATED GENE EXPRESSION IN MCF-7 HUMAN BREAST CANCER CELLS AND NORMAL HUMAN BREAST EPITHELIAL CELLS.

F Irshaid¹ , SK Kulp^{1 *}, Y Sugimoto¹ , K Lee¹ , YC Lin^{1 *}
Lab Reprod & Molecular Endocrinology, College Vet Med, The Ohio State Univ, Columbus, Ohio ¹

Zeranol (Z) is a nonsteroidal anabolic growth promoter with estrogenic activity that is used by the meat-producing industry in the U.S. We have shown that meat and serum from Z-implanted beef cattle possess heat-stable mitogenic activity for primary cultured breast cells. HPLC measurements revealed Z residue levels in these tissues below the FDA limits for edible tissues (150-600 ppb). This study was designed to examine the effect of Z on the expression of estrogen-regulated genes in primary cultured normal human breast epithelial cells (EC) and the MCF-7 human breast cancer cells. EC were cultured in low Ca²⁺ DMEM/F12 (0.04 mM) and MCF-7 cells were cultured in regular DMEM/F12 (1.05 mM Ca²⁺) containing 5% FCS. Cells were treated for 48 hr with different concentrations of Z (0.0, 1.0, 10.0, 100 nM). After treatment, a non-radioactive cell proliferation assay was used to measure cell growth. Our data show that in both EC and MCF-7 cells, Z significantly increased cell proliferation at 10 and 100 nM (P<0.05). Also, the expression of estrogen-regulated genes were determined by RT-PCR. These results revealed that Z treatment elevated mRNA levels of both cyclin D1 and cathepsin D in both cell types in a dose- related manner. In EC cells, Z at 10 nM and 100 nM increased cyclin D1 mRNA 1.5 and 1.6 fold, respectively, and cathepsin D mRNA 1.6 and 1.8 fold, respectively. Similarly, in MCF-7 cells, Z at 10 nM and 100 nM increased cyclin D1 mRNA 1.5 and 1.6 fold, respectively, and cathepsin D mRNA 1.7 and 1.8 fold, respectively. These results indicate that both normal and cancerous human breast cells exhibit estrogenic responses to Z, and implicate the potential for xenoestrogenic effects on human breast cell growth. (Grants from Army Breast Cancer Research Program DAMD 8140 & NIH CA66193 & P30 CA16058).

    This abstract is being presented on Tuesday, August 3 at 8:00 AM to 10:15 AM at CUB 2nd Floor Ballroom.