Hypothyroidism reduces mammary tumor progression via [Beta]-catenin-activated intrinsic apoptotic pathway in rats

Experimental hypothyroidism retards mammary carcinogenesis promoting apoptosis of tumor cells. [beta]-catenin plays a critical role in cell adhesion and intracellular signaling pathways conditioning the prognosis of breast cancer. However, the mechanistic connections associated with the expression of [beta]-catenin in thyroid status and breast cancer are not known. Therefore, we studied the relationship between the expression and localization of [beta]-catenin and apoptosis in mammary tumors induced by 7,12-dimethylbenz(a)anthracene (DMBA) in hypothyroid (Hypot) and euthyroid (EUT) rats. Female Sprague Dawley rats were treated with a dose of DMBA (15 mg/rat) at 55 days of age and were then divided into two groups: HypoT (0.01% 6-N-propyl-2-thiouracil in drinking water, n=54) and EUT (untreated control, n=43). Latency, incidence and progression of tumors were determined. At sacrifice, tumors were obtained for immunohistological studies and Western Blot. The latency was longer (p