Hypothyroidism and Mammary Cancer: Role of Peritumoral Adipose Tissue

To study the effects of HypoT on rat mammary tumor-associated adipose tissue and its ability to modify the biological behavior of breast cancer epithelial cells, we evaluated changes in the viability, proliferation, apoptosis, adhesion, and migration of tumorigenic (MCF-7, MDA-MB-231) and non-tumorigenic (MCF-10A) mammary cells incubated with the conditioned media from mammary adipose tissue (MAT-CMs) of HypoT and euthyroid (EUT) rats with and without mammary tumors. Female Sprague-Dawley rats were treated with 7, 12-Dimethylbenz[a]anthracen (15mg/rat) at 55 days of age to induce mammary tumors and were divided at random in HypoT (0.01% 6-N-propyl-2-thiouracil in drinking water, n = 30) and EUT (tap water, n = 30). Fragments of MAT were incubated for 24 h with M199 medium, and MAT-CMs were collected. MCF-7, MDA-MB-231, and MCF-10A were incubated with non-tumor and tumor MAT-CMs, and viability, proliferation, apoptosis, adhesion, and migration were quantified. Non-tumor MAT-CMs of HypoT rats favored apoptosis of MCF-10A; decreased the viability and adhesion of MCF-7; promoted proliferation, and decreased the adhesion of MDA-MB-231. Tumor MAT-CMs of HypoT rats stimulated proliferation in tumorigenic cells and inhibited apoptosis of MCF-10A. Non-tumor MAT-CMs of HypoT rats may protect against tumorigenesis while tumor MAT-CMs of HypoT may favor a more tumorigenic behavior of mammary tumor cells.