Analyzing a New Mechanism in Response to Tamoxifen Therapy in Breast Cancer Patients

This study will help to understand the interaction between estrogen receptor-alpha (ER alpha) and tumor suppressor protein p53 as well as impact on patient tumor gene expression in response to the hormonal therapy Tamoxifen. This information may eventually help select the appropriate therapy for future patients with similar cancer.

Women with abnormal mammogram or suspicious masses will undergo diagnostic core biopsies which will be analyzed for ER/PR and HER2Neu expression. For patients that are ER positive, p53 staining will be done. Women presenting tumors with an Allred score of 3 or greater status will be approached to participate. Women will be randomized to either standard of care surgical therapy or a 4 week intervention of Tamoxifen 20mg daily for 4 weeks prior to surgery. During the intervention, blood draws will be done to measure levels of tamoxifen metabolites in the blood and test for polymorphisms that may decrease levels of active metabolites. Women will undergo two blood draws for PK/PD and one for pharmacogenomics. Tissue microarray (TMA) will be generated from resected tumors for immunohistochemistry (IHC) and proximity ligation assay (PLA) for measuring ER alpha-p53 interaction. Tumor tissue will be used for analyzing tamoxifen metabolites and estradiol levels. RNA and proteins from the tumors will be used for analyzing gene expression.