Breast cancer is one of the most common malignances among women in the U.S. Despite many advances in breast cancer detection and treatment, we are still no closer to eradicating this disease because it is more complex than we previously thought. Among many risk factors, estrogens and non-estrogenic endocrine disruptors are considered to play critical roles in human breast carcinogenesis. Zeranol (Z) is a non-steroidal agent with potent estrogenic activity. Recently, concerns have been raised about the potential adverse health risk posed by consuming the product containing bio-active Z metabolites produced by Z-implanted beef cattle. Our experimental data demonstrated that proliferation of pre-adipocytes isolated from adipose tissues of 60-day Z-implanted beef heifers was about 12-fold faster than that of the control pre-adipocytes. We have also demonstrated that Z-containing sera and meat extracts harvested from the Z-implanted beef heifers (30, 60, 90 days post-Z-implantation) possess potent mitogenic activities in stimulating the proliferation of primary cultured human normal, cancerous breast epithelial cells and MCF-7 cells. Z at 10 nM induced an 18-fold increase in aromatase mRNA expression levels in primary cultured human normal breast pre-adipocytes after 24 hrs of exposure. The current study examined the potential tumorigenic activity of bio-active Z containing sera harvested from heifers two months implantation with Z. Exposure of MCF-10A to 0.2, 1, and 5% Z-containing serum in low calcium DMEM/F12 medium over a period of 3 weeks, Our results showed that proliferation of MCF-10A treated with 0.2, 1 and 5% of Z-containing serum was 1.3, 1.75 and 1.8-fold faster than control sera exposed MCF-10A cells. The control serum exposed MCF-10A cells had no significant impacts on the induction of cyclin D1 and p53 mRNA expression. Z-containing sera at 0.2, 1 and 5% increased cyclin D1 protein expression to 2.4, 11.7, and 13.3% and decreased p53 protein expression to 1.74, 26, and 52% in MCF-10A as compared to the controls. Ten repeated treatment cycles of 0.2 and 1% of Z-containing sera stimulated MCF-10A cell anchorage independent colony formation in 0.35% soft agar, no such evidence was observed in the controls. Our experimental results suggest that transformation of MCF-10A cells to neoplastic breast cells by in vitro exposure of low levels of Z-containing sera may be mediated through the up-regulation of cyclin D1, and down-regulation of p53, at both the mRNA and protein levels. We hypothesize that consumption of bio-active Z metabolites containing meat produced from the Z-implanted beef cattle (equivalent to HPLC detectable concentration of 93 nM , 30 ppb) may have potential adverse health effects in the general population and menopausal women with high risk of breast cancer. (Supported by NIH grant R01 ES015212-01)

Citation Information: In: Proc Am Assoc Cancer Res; 2009 Apr 18-22; Denver, CO. Philadelphia (PA): AACR; 2009. Abstract nr 791.

100th AACR Annual Meeting-- Apr 18-22, 2009; Denver, CO

American Association for Cancer Research
2009