Gene expression profiling of mammary glands at an early stage of DMBA-induced carcinogenesis in the female Sprague-Dawley rat.

Background: Breast cancer is the most common cause of cancer death among women worldwide and the second leading cause of tumor-related death for women in westernized countries. Most research efforts to find a breast cancer biomarker have focused on the stage after the cancer is diagnosed. To investigate more deeply into mammary cancer prevention, a study of precancerous lesion development seems a priority. Experimentally-induced mammary tumors in rats constitute a powerful tool for studying the pathogenesis of this cancer and the molecular mechanisms involved in neoplastic progression. Furthermore, Materials and Methods: Twelve 7 wk-old virgin female Sprague-Dawley rats were randomized into 2 experimental groups: 1) DMBA-treated (40 mg/kg b.w. by intragastric administration (i.g.) in corn oil as the vehicle and 2) treated with corn oil (vehicle) by ig. At 2 and 4 weeks after DMBA administration, 3 animals randomly chosen from each experimental group were sacrificed and necropsied. Total RNA was extracted and the global gene expression patterns from the mammary gland and liver samples collected were used to identify the molecular profile of the precancerous stage genome. Significantly altered genes as evinced by multivariate data analysis were further confirmed by quantitative real time PCR and siRNA knockdown assays. Results and Discussion: Genes involved in cancer progression, migration, proliferation and oxidative stress were identified in this study. MARK,