Both breast cancer and obesity are very serious problems in the U.S. Leptin, mainly secreted by adipocytes, is a product of the obese (ob) gene and plays an important role in breast cancer development. Leptin expression is up-regulated in obesity and it can promote breast cancer cell growth. On the other hand, exposure to environmental estrogens has been found to be directly related to breast cancer. Zeranol (Z), is a non-steroidal anabolic growth promoter with estrogenic activity and widely used in the U.S beef industry. Another natural compound extracted from cottonseed and used as an anticancer chemopreventive agent, gossypol, can inhibit breast cancer growth. It is suggested gossypol could be used as potential chemopreventive food components.
The current study demonstrated that Z stimulated the proliferation of primary cultured human normal and cancerous breast epithelial cells and sera collected from Z-implanted beef heifers stimulated the growth of pre-adipocytes isolated from breast cancer patients. This study is focusing on evaluation of Z and bio-active Z-containing sera collected from Z-implanted beef and its adverse health risk to human consumption of Z-containing meat produced from Z-implanted beef cattle. We hypothesize that Z might increase the risk of breast cancer in obese women. Cell proliferation assay, ELISA analysis, RT-PCR and Western blotting were conducted.
The primary cultured human normal breast epithelial cells (HNBECs) and pre-adipocytes (HNBPADs) were isolated from human normal breast tissues and cultured, the primary cultured human breast cancer epithelial cells (HBCECs) were isolated from breast cancer patients and cultured. The MTT assay to evaluate the proliferation of HNBECs, HBCECs, and HNBPADs was carried out. The sera used in the MTT assay were: non-zeranol serum (NZS) dropped from the non-zeranol-implantation beef heifers at day 0 (NZS-D0) and at day 30 post zeranol-implantation (NZS-D30); zeranol-serum (ZS) harvested from zeranol implantation heifers at day 0 (ZS-D0) and day 30 post zeranol-implantation (ZS-D30). The concentration for both NZS and ZS was 0.2, 1.0 and 5.0% in cultured medium.
Our result shows both Z and lp can increase primary cultured HNBECs, HNCECs, PADs and MCF-7 Adr cell growth. ZS have a greater power to stimulate HNBECs and HNBPADs growth than NZS and the combination of Z with leptin increase HNBECs and HNBPADs cyclin D1 mRNA expression and down-regulate P53 or PTPg mRNA expression while (-)-gossypol revert its effect in MCF-7 Adr cells, primary cultured PADs, HBCECs and HBNECs.
Leptin can increase the breast cancer cells’ sensitivity to Z and Z increase the ObR mRNA expression both in primary cultured HBCECs and MCF-7 Adr cells. Z stimulates primary cultured HNBECs and PADs secrete leptin. These results pointed out that the leptin may be involved in enhancing the HNBPADs sensitivity to ZS and there is interaction between Z and leptin in HNBPADs.
It suggests Z maybe more harmful to obese patients and might play a role in breast cancer development and (-)-gossypol may serve as a potential chemopreventive agent and play an important role in breast cancer chemoprevention.