Another important issue to be considered is the complex cross-talk between the steroid hormones themselves and steroid receptors; for example, progesterone induces changes in ERα chromatin binding events in breast cancer cell lines (MCF-7 and T-47D) and leads new gene expression profiles that are associated to a better prognosis in breast cancer patients; moreover, P4 inhibits estrogen proliferative effect in primary culture of breast tumor tissue and xenografts of tumor cells in mice [35]. Here, ESR1 is linked to breast cancer.